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+++ b/ARCHITECTURE.md
@@ -0,0 +1,476 @@
+# Tachikoma Architecture
+
+This document provides a detailed technical overview of the Tachikoma AI integration library architecture.
+
+## Overview
+
+Tachikoma is designed as a modular, type-safe Swift package that abstracts AI provider differences behind a unified interface. The architecture emphasizes Swift 6 concurrency safety, performance, and extensibility.
+
+## Core Architecture Principles
+
+### 1. Protocol-Oriented Design
+All AI providers implement the `ModelInterface` protocol, ensuring consistent behavior across different services while allowing provider-specific optimizations.
+
+### 2. Swift 6 Strict Concurrency
+- All public APIs are actor-safe
+- Sendable conformance throughout the type system
+- `@MainActor` isolation where appropriate
+- No data races or concurrency issues
+
+### 3. Type Safety
+- Strongly-typed message system with enum-based content types
+- Compile-time verification of tool parameters
+- Generic tool system with context type safety
+
+### 4. Performance First
+- Intelligent caching with configurable policies
+- Streaming responses with minimal memory overhead
+- Lazy provider initialization
+- Efficient JSON handling without reflection
+
+## Module Structure
+
+```
+Tachikoma/
+├── Sources/Tachikoma/
+│   ├── Tachikoma.swift              # Main API entry point
+│   ├── Core/                        # Core abstractions
+│   │   ├── ModelInterface.swift     # Provider protocol
+│   │   ├── ModelProvider.swift      # Provider registry & management
+│   │   ├── MessageTypes.swift       # Message type system
+│   │   ├── StreamingTypes.swift     # Streaming event system
+│   │   ├── ModelParameters.swift    # Request/response parameters
+│   │   ├── ToolDefinitions.swift    # Tool calling system
+│   │   └── TachikomaError.swift     # Error handling
+│   └── Providers/                   # Provider implementations
+│       ├── OpenAI/
+│       │   ├── OpenAIModel.swift    # OpenAI implementation
+│       │   └── OpenAITypes.swift    # OpenAI-specific types
+│       ├── Anthropic/
+│       │   ├── AnthropicModel.swift # Anthropic implementation
+│       │   └── AnthropicTypes.swift # Anthropic-specific types
+│       ├── Grok/
+│       │   ├── GrokModel.swift      # Grok implementation
+│       │   └── GrokTypes.swift      # Grok-specific types
+│       └── Ollama/
+│           ├── OllamaModel.swift    # Ollama implementation
+│           └── OllamaTypes.swift    # Ollama-specific types
+```
+
+## Core Components
+
+### ModelInterface Protocol
+
+The central abstraction that all providers implement:
+
+```swift
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public protocol ModelInterface: Sendable {
+    /// Masked API key for debugging
+    var maskedApiKey: String { get }
+    
+    /// Get a single response
+    func getResponse(request: ModelRequest) async throws -> ModelResponse
+    
+    /// Get streaming response
+    func getStreamedResponse(request: ModelRequest) async throws -> AsyncThrowingStream<StreamEvent, any Error>
+}
+```
+
+**Key Design Decisions:**
+- `Sendable` conformance ensures thread safety
+- Async/await for all network operations
+- Streaming uses `AsyncThrowingStream` for memory efficiency
+- Availability annotations ensure compatibility
+
+### Message Type System
+
+Hierarchical message types that handle all AI interaction patterns:
+
+```swift
+public enum Message: Codable, Sendable {
+    case system(id: String? = nil, content: String)
+    case user(id: String? = nil, content: MessageContent)
+    case assistant(id: String? = nil, content: [AssistantContent], status: MessageStatus = .completed)
+    case tool(id: String? = nil, toolCallId: String, content: String)
+    case reasoning(id: String? = nil, content: String)
+}
+```
+
+**Content Type Hierarchy:**
+- `MessageContent`: Text, images, multimodal, files, audio
+- `AssistantContent`: Text output, refusals, tool calls
+- `ImageContent`: URLs, base64 data, detail levels
+- `AudioContent`: Transcripts, durations, metadata
+
+**Benefits:**
+- Type safety prevents invalid message construction
+- Codable conformance for persistence
+- Sendable for concurrency safety
+- Extensible for new content types
+
+### Streaming System
+
+Real-time event processing with comprehensive event types:
+
+```swift
+public enum StreamEvent {
+    case responseStarted(StreamResponseStarted)
+    case textDelta(StreamTextDelta)
+    case toolCallDelta(StreamToolCallDelta)
+    case toolCallCompleted(StreamToolCallCompleted)
+    case responseCompleted(StreamResponseCompleted)
+    case error(StreamError)
+}
+```
+
+**Stream Processing Flow:**
+1. `responseStarted` - Metadata and initialization
+2. `textDelta` - Incremental text content
+3. `toolCallDelta` - Incremental tool call construction
+4. `toolCallCompleted` - Complete tool call available
+5. `responseCompleted` - Stream finished with final metadata
+6. `error` - Error events for handling failures
+
+**Implementation Details:**
+- Each provider converts its streaming format to unified events
+- Back-pressure handling through `AsyncThrowingStream`
+- Automatic event ordering and consistency validation
+
+### Tool Calling System
+
+Generic, type-safe tool execution with context support:
+
+```swift
+public struct Tool<Context> {
+    public let execute: (ToolInput, Context) async throws -> ToolOutput
+    
+    public func toToolDefinition() -> ToolDefinition {
+        // Convert to provider-agnostic definition
+    }
+}
+```
+
+**Type Safety Features:**
+- Generic context ensures compile-time type checking
+- Parameter validation through JSON Schema
+- Async execution for I/O operations
+- Error handling with structured failures
+
+**Tool Definition System:**
+```swift
+public struct ToolDefinition {
+    public let function: FunctionDefinition
+    public let type: ToolType = .function
+}
+
+public struct FunctionDefinition {
+    public let name: String
+    public let description: String?
+    public let parameters: ToolParameters
+}
+```
+
+### Error Handling
+
+Comprehensive error system with recovery guidance:
+
+```swift
+public enum TachikomaError: Error, LocalizedError {
+    case modelNotFound(String)
+    case authenticationFailed
+    case invalidConfiguration(String)
+    case networkError(underlying: any Error)
+    case rateLimited
+    case insufficientQuota
+    case contextLengthExceeded
+    // ... more cases
+    
+    public var isRetryable: Bool { /* logic */ }
+    public var recoverySuggestion: String? { /* guidance */ }
+}
+```
+
+**Error Categories:**
+- **Client Errors**: Invalid requests, configuration issues
+- **Authentication Errors**: API key problems, quota issues
+- **Network Errors**: Connectivity, timeouts, server errors
+- **Provider Errors**: Model-specific limitations
+
+## Provider Implementations
+
+### OpenAI Provider
+
+**Dual API Support:**
+- Chat Completions API (`/v1/chat/completions`) for standard models
+- Responses API (`/v1/responses`) for o3/o4 reasoning models
+
+**Key Features:**
+- Automatic API selection based on model capabilities
+- Parameter filtering (o3/o4 models don't support temperature)
+- Reasoning summary handling for thinking models
+- Complete streaming support for both APIs
+
+**Implementation Highlights:**
+```swift
+private func convertToOpenAIRequest(_ request: ModelRequest, stream: Bool) throws -> OpenAIRequest {
+    // Convert unified request to OpenAI format
+    // Handle parameter filtering
+    // Support both API formats
+}
+```
+
+### Anthropic Provider
+
+**Native Claude Integration:**
+- Direct Claude API with proper message formatting
+- Content blocks for multimodal inputs
+- System prompt separation
+- Tool result handling as user messages
+
+**Streaming Implementation:**
+- Server-Sent Events (SSE) processing
+- Delta accumulation for tool calls
+- Proper handling of Claude's content block structure
+
+**Claude 4 Features:**
+- Extended thinking modes
+- Long-running task support
+- Advanced reasoning capabilities
+
+### Grok Provider
+
+**OpenAI Compatibility:**
+- Uses OpenAI-compatible Chat Completions API
+- Parameter filtering for Grok 3/4 models
+- Standard streaming implementation
+
+**Optimizations:**
+- Efficient parameter encoding
+- Proper error response handling
+- Rate limiting awareness
+
+### Ollama Provider
+
+**Local Inference:**
+- HTTP API for local models
+- Custom timeout handling (5 minutes for model loading)
+- Tool calling detection for compatible models
+
+**Model Support:**
+- Language models: llama3.3, mistral, etc.
+- Vision models: llava, bakllava (no tool calling)
+- Custom model endpoints
+
+## Provider Registry & Management
+
+### ModelProvider (Actor)
+
+Central registry for all model factories and instances:
+
+```swift
+@MainActor
+public final class ModelProvider {
+    public static let shared = ModelProvider()
+    
+    private var modelFactories: [String: @Sendable () throws -> any ModelInterface] = [:]
+    private var modelCache: [String: any ModelInterface] = [:]
+    
+    public func getModel(_ modelName: String) async throws -> any ModelInterface
+    public func register(modelName: String, factory: @escaping @Sendable () throws -> any ModelInterface)
+}
+```
+
+**Registration System:**
+- Default model registration at startup
+- Custom factory registration
+- Lenient name matching (e.g., "gpt" → "gpt-4.1")
+- Provider/model path resolution ("openai/gpt-4")
+
+**Caching Strategy:**
+- Model instances cached after first creation
+- Cache invalidation on registration changes
+- Memory-efficient with weak references where appropriate
+
+## Concurrency & Threading
+
+### Actor Usage
+
+**ModelProvider as MainActor:**
+- Centralizes model management
+- Ensures thread-safe registration
+- Coordinates provider initialization
+
+**Sendable Conformance:**
+- All message types are Sendable
+- Model instances are Sendable
+- Error types are Sendable
+- Tool definitions are Sendable
+
+**Async/Await Integration:**
+- All network operations are async
+- Streaming uses AsyncThrowingStream
+- No blocking operations on main thread
+
+### Memory Management
+
+**Streaming Efficiency:**
+- Events processed incrementally
+- No accumulation of entire responses
+- Automatic memory cleanup
+
+**Cache Management:**
+- Model instances cached intelligently
+- Configurable cache policies
+- Weak references for large objects
+
+## Security Considerations
+
+### API Key Handling
+
+**Environment Variables:**
+- Support for multiple key formats
+- Secure key storage recommendations
+- Masked keys in debug output
+
+**Key Security:**
+- Never log full API keys
+- Secure transmission only
+- No persistence of keys in plain text
+
+### Input Validation
+
+**Parameter Validation:**
+- Type-safe parameter construction
+- Range validation for numeric parameters
+- Required field enforcement
+
+**Content Filtering:**
+- Provider-specific content policies
+- Error handling for filtered content
+- Transparent policy communication
+
+## Performance Characteristics
+
+### Network Efficiency
+
+**Connection Management:**
+- URLSession with appropriate timeouts
+- HTTP/2 support where available
+- Connection pooling
+
+**Request Optimization:**
+- Minimal payload size
+- Efficient JSON encoding
+- Compression support
+
+### Memory Usage
+
+**Streaming Responses:**
+- Constant memory usage regardless of response size
+- Incremental processing
+- Automatic garbage collection
+
+**Object Creation:**
+- Minimal allocations in hot paths
+- Reuse of formatter objects
+- Efficient string handling
+
+## Testing Strategy
+
+### Unit Tests
+
+**Provider Tests:**
+- Mock network responses
+- Error condition testing
+- Parameter validation tests
+
+**Integration Tests:**
+- End-to-end flow testing
+- Streaming behavior validation
+- Tool calling integration
+
+**Performance Tests:**
+- Memory usage profiling
+- Response time benchmarks
+- Concurrent request handling
+
+## Extension Points
+
+### Custom Providers
+
+Implement `ModelInterface` to add new providers:
+
+```swift
+class CustomProvider: ModelInterface {
+    var maskedApiKey: String { "custom-***" }
+    
+    func getResponse(request: ModelRequest) async throws -> ModelResponse {
+        // Custom implementation
+    }
+    
+    func getStreamedResponse(request: ModelRequest) async throws -> AsyncThrowingStream<StreamEvent, Error> {
+        // Custom streaming
+    }
+}
+```
+
+### Message Type Extensions
+
+Add new content types by extending `MessageContent`:
+
+```swift
+extension MessageContent {
+    case customType(CustomData)
+}
+```
+
+### Tool System Extensions
+
+Create specialized tool contexts:
+
+```swift
+struct DatabaseContext {
+    let connection: DatabaseConnection
+    let schema: Schema
+}
+
+let dbTool = Tool<DatabaseContext> { input, context in
+    // Database operations with type-safe context
+}
+```
+
+## Future Considerations
+
+### Planned Features
+
+**Enhanced Caching:**
+- Persistent cache with TTL
+- Smart cache invalidation
+- Distributed caching support
+
+**Advanced Streaming:**
+- Bidirectional streaming
+- Stream multiplexing
+- Custom event types
+
+**Provider Enhancements:**
+- More granular configuration
+- Provider-specific optimizations
+- Enhanced error recovery
+
+### Scalability
+
+**High-Volume Usage:**
+- Connection pooling improvements
+- Request batching
+- Rate limiting integration
+
+**Enterprise Features:**
+- Audit logging
+- Metrics collection
+- Custom authentication
+
+---
+
+This architecture provides a solid foundation for AI integration while maintaining flexibility for future enhancements and provider additions.
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
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--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,173 @@
+# Changelog
+
+All notable changes to the Tachikoma project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [1.0.0] - 2025-01-XX
+
+### Added
+
+#### Core Framework
+- Initial release of Tachikoma AI integration library
+- Unified `ModelInterface` protocol for all AI providers
+- Comprehensive message type system with multimodal support
+- Real-time streaming response handling with `AsyncThrowingStream`
+- Type-safe tool calling system with generic context support
+- Actor-based provider registry with intelligent caching
+- Swift 6 strict concurrency compliance throughout
+
+#### Provider Support
+- **OpenAI Provider**: Complete integration with dual API support
+  - Chat Completions API for standard models (GPT-4o, GPT-4.1)
+  - Responses API for reasoning models (o3, o4 series)
+  - Automatic API selection based on model capabilities
+  - Parameter filtering for reasoning models
+  - Full streaming support for both APIs
+  - Reasoning summary handling for thinking models
+
+- **Anthropic Provider**: Native Claude API integration
+  - Support for Claude 4 (Opus, Sonnet) with thinking modes
+  - Claude 3.5/3.7 series compatibility
+  - Content block handling for multimodal inputs
+  - System prompt separation
+  - Server-Sent Events streaming
+  - Extended reasoning capabilities
+
+- **Grok Provider**: xAI integration with OpenAI compatibility
+  - Grok 4, Grok 3, Grok 2 series support
+  - Vision model capabilities
+  - Parameter filtering for Grok 3/4 models
+  - Standard streaming implementation
+  - OpenAI-compatible Chat Completions API
+
+- **Ollama Provider**: Local model inference support
+  - Support for Llama 3.3 (recommended), Mistral, CodeLlama
+  - Vision models (llava, bakllava) without tool calling
+  - Configurable endpoints for self-hosted deployments
+  - Extended timeouts for local model loading
+  - Tool calling detection for compatible models
+
+#### Message System
+- **Unified Message Types**: Support for system, user, assistant, tool, and reasoning messages
+- **Content Types**: Text, images (URL/base64), multimodal, files, audio with transcripts
+- **Assistant Content**: Text output, refusals, tool calls with proper typing
+- **Image Support**: High/low detail levels, multiple formats, base64 encoding
+- **Audio Support**: Transcript extraction, duration metadata
+
+#### Streaming System
+- **Event-Based Architecture**: Comprehensive streaming event types
+- **Real-Time Processing**: Incremental text deltas, tool call construction
+- **Memory Efficiency**: Constant memory usage regardless of response size
+- **Error Handling**: Structured error events with recovery information
+- **Provider Abstraction**: Unified events across different provider formats
+
+#### Tool Calling
+- **Generic Tool System**: Type-safe tool execution with context support
+- **Parameter Validation**: JSON Schema-based parameter validation
+- **Async Execution**: Non-blocking tool execution with proper error handling
+- **Tool Definitions**: Provider-agnostic tool definition format
+- **Context Management**: Type-safe context passing to tool functions
+
+#### Error Handling
+- **Comprehensive Error Types**: Structured error hierarchy with recovery guidance
+- **Provider-Specific Errors**: Tailored error handling for each provider
+- **Retry Logic**: Built-in retry detection with exponential backoff support
+- **Error Categories**: Client, authentication, network, and provider errors
+- **Localized Descriptions**: User-friendly error messages with recovery suggestions
+
+#### Configuration System
+- **Environment Variables**: Support for standard API key environment variables
+- **Provider Configuration**: Flexible configuration for custom endpoints
+- **Model Registration**: Runtime model factory registration
+- **Lenient Matching**: Intelligent model name resolution
+- **Cache Management**: Configurable caching policies
+
+### Technical Features
+
+#### Swift 6 Compliance
+- **Strict Concurrency**: Full Swift 6 strict concurrency mode compliance
+- **Sendable Conformance**: All public types conform to Sendable protocol
+- **Actor Safety**: Thread-safe operations with proper isolation
+- **Memory Safety**: No data races or concurrency issues
+- **Performance**: Optimized for concurrent execution
+
+#### Performance Optimizations
+- **Intelligent Caching**: Model instance caching with smart invalidation
+- **Connection Pooling**: Efficient network connection management
+- **Memory Management**: Minimal allocations and efficient garbage collection
+- **Streaming Efficiency**: Incremental processing without accumulation
+- **JSON Optimization**: Fast encoding/decoding without reflection
+
+#### Type Safety
+- **Compile-Time Verification**: Strong typing throughout the API
+- **Generic Constraints**: Type-safe tool contexts and parameters
+- **Enum-Based Design**: Exhaustive pattern matching for robustness
+- **Protocol-Oriented**: Clean abstractions with concrete implementations
+
+### Documentation
+- Comprehensive README with quick start guide
+- Detailed architecture documentation
+- API reference documentation
+- Code examples for common usage patterns
+- Migration guide from PeekabooCore
+- Performance optimization guidelines
+
+### Testing
+- Unit tests for all core components
+- Integration tests for provider functionality
+- Mock providers for testing scenarios
+- Performance benchmarks
+- Concurrency safety tests
+
+### Platform Support
+- macOS 14.0+
+- iOS 17.0+
+- watchOS 10.0+
+- tvOS 17.0+
+- Swift 6.0+
+- Xcode 16.0+
+
+## [Unreleased]
+
+### Planned Features
+- Enhanced caching with persistence and TTL
+- Bidirectional streaming support
+- Request batching for high-volume usage
+- Advanced error recovery mechanisms
+- Metrics collection and monitoring
+- Distributed caching support
+
+---
+
+## Version History
+
+- **v1.0.0**: Initial release extracted from PeekabooCore with Swift 6 compliance
+- **v0.x.x**: Development versions (internal)
+
+## Migration Notes
+
+### From PeekabooCore
+When migrating from PeekabooCore's AI system:
+
+1. **Error Types**: Replace `PeekabooError` with `TachikomaError`
+2. **Import Statements**: Update to `import Tachikoma`
+3. **Model Creation**: Use `Tachikoma.shared.getModel()` instead of direct instantiation
+4. **Streaming Events**: Update event handling for new event type hierarchy
+5. **Message Types**: Adopt new unified message type system
+6. **Tool Calling**: Update to generic tool system with context support
+
+### Breaking Changes
+This is the initial release, so no breaking changes from previous versions.
+
+## Contributors
+
+- **Extraction Lead**: AI Assistant
+- **Original Code**: Peekaboo project contributors
+- **Architecture Design**: Based on proven patterns from PeekabooCore
+- **Swift 6 Migration**: Complete rewrite for strict concurrency compliance
+
+## License
+
+This project is licensed under the MIT License. See LICENSE file for details.
\ No newline at end of file
diff --git a/Package.resolved b/Package.resolved
new file mode 100644
index 0000000..f2401e3
--- /dev/null
+++ b/Package.resolved
@@ -0,0 +1,15 @@
+{
+  "originHash" : "3929c9b9fd81518c26df5464b3e6a459042d74460f8bfd7fb79e21dc5c507bdf",
+  "pins" : [
+    {
+      "identity" : "swift-log",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-log.git",
+      "state" : {
+        "revision" : "ce592ae52f982c847a4efc0dd881cc9eb32d29f2",
+        "version" : "1.6.4"
+      }
+    }
+  ],
+  "version" : 3
+}
diff --git a/Package.swift b/Package.swift
new file mode 100644
index 0000000..e820da2
--- /dev/null
+++ b/Package.swift
@@ -0,0 +1,65 @@
+// swift-tools-version: 6.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "Tachikoma",
+    platforms: [
+        .macOS(.v14),
+        .iOS(.v17),
+        .watchOS(.v10),
+        .tvOS(.v17)
+    ],
+    products: [
+        .library(
+            name: "Tachikoma",
+            targets: ["Tachikoma"]
+        ),
+    ],
+    dependencies: [
+        .package(url: "https://github.com/apple/swift-log.git", from: "1.0.0"),
+    ],
+    targets: [
+        .target(
+            name: "Tachikoma",
+            dependencies: [
+                .product(name: "Logging", package: "swift-log"),
+            ],
+            path: "Sources",
+            swiftSettings: [
+                .enableExperimentalFeature("StrictConcurrency"),
+                .enableUpcomingFeature("BareSlashRegexLiterals"),
+                .enableUpcomingFeature("ConciseMagicFile"),
+                .enableUpcomingFeature("ForwardTrailingClosures"),
+                .enableUpcomingFeature("ImportObjcForwardDeclarations"),
+                .enableUpcomingFeature("DisableOutwardActorInference"),
+                .enableUpcomingFeature("ExistentialAny"),
+                .enableUpcomingFeature("DeprecateApplicationMain"),
+                .enableUpcomingFeature("GlobalConcurrency"),
+                .enableUpcomingFeature("IsolatedDefaultValues"),
+                .enableUpcomingFeature("InternalImportsByDefault"),
+            ]
+        ),
+        .testTarget(
+            name: "TachikomaTests",
+            dependencies: [
+                "Tachikoma",
+                .product(name: "Logging", package: "swift-log"),
+            ],
+            swiftSettings: [
+                .enableExperimentalFeature("StrictConcurrency"),
+                .enableUpcomingFeature("BareSlashRegexLiterals"),
+                .enableUpcomingFeature("ConciseMagicFile"),
+                .enableUpcomingFeature("ForwardTrailingClosures"),
+                .enableUpcomingFeature("ImportObjcForwardDeclarations"),
+                .enableUpcomingFeature("DisableOutwardActorInference"),
+                .enableUpcomingFeature("ExistentialAny"),
+                .enableUpcomingFeature("DeprecateApplicationMain"),
+                .enableUpcomingFeature("GlobalConcurrency"),
+                .enableUpcomingFeature("IsolatedDefaultValues"),
+                .enableUpcomingFeature("InternalImportsByDefault"),
+            ]
+        ),
+    ]
+)
\ No newline at end of file
diff --git a/README.md b/README.md
index 14aa939..76b6d7a 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,429 @@
-# Tachikoma
-One interface, every AI model. A Swift SDK to interface with AI providers.
+<div align="center">
+  <img src="assets/logo.png" alt="Tachikoma Logo" width="200">
+  <h1>Tachikoma</h1>
+</div>
+
+A comprehensive Swift package for AI model integration, providing a unified interface for multiple AI providers including OpenAI, Anthropic, Grok (xAI), and Ollama.
+
+Named after the spider-tank AI from Ghost in the Shell, Tachikoma provides an intelligent, adaptable interface for AI services.
+
+## Features
+
+- **Unified API**: Single interface for multiple AI providers
+- **Swift 6 Compliant**: Built with Swift 6 strict concurrency mode for maximum safety
+- **Streaming Support**: Real-time streaming responses for all supported providers
+- **Tool Calling**: Complete function calling support for AI agent workflows
+- **Multimodal**: Support for text, images, audio, and file inputs
+- **Type Safety**: Strongly-typed message handling and error management
+- **Performance**: Optimized for efficiency with intelligent caching and resource management
+
+## Supported Providers
+
+### OpenAI
+- **Models**: GPT-4o, GPT-4.1, o3, o4 series with full parameter support
+- **Features**: Chat Completions API, Responses API, streaming, tool calling, multimodal
+- **API Types**: Automatic selection between Chat Completions and Responses APIs
+
+### Anthropic (Claude)
+- **Models**: Claude 4 (Opus, Sonnet), Claude 3.5/3.7 series with thinking modes
+- **Features**: Native streaming, tool calling, multimodal, extended reasoning
+- **Capabilities**: Long-running tasks, system prompts, safety filtering
+
+### Grok (xAI)
+- **Models**: Grok 4, Grok 3, Grok 2 series with vision capabilities
+- **Features**: OpenAI-compatible API, streaming, tool calling, parameter filtering
+- **Performance**: High-speed inference with competitive pricing
+
+### Ollama
+- **Models**: Llama 3.3 (recommended), Mistral, CodeLlama, and vision models
+- **Features**: Local inference, tool calling (select models), streaming
+- **Deployment**: Self-hosted with configurable endpoints
+
+## Installation
+
+### Swift Package Manager
+
+Add Tachikoma as a dependency in your `Package.swift`:
+
+```swift
+dependencies: [
+    .package(url: "https://github.com/steipete/Tachikoma", from: "1.0.0")
+]
+```
+
+### Requirements
+
+- macOS 14.0+, iOS 17.0+, watchOS 10.0+, tvOS 17.0+
+- Swift 6.0+
+- Xcode 16.0+
+
+## Quick Start
+
+### Basic Usage
+
+```swift
+import Tachikoma
+
+// Get a model instance
+let tachikoma = Tachikoma.shared
+let model = try await tachikoma.getModel("claude-opus-4")
+
+// Create a simple request
+let request = ModelRequest(
+    messages: [
+        .user(content: .text("What is the capital of France?"))
+    ]
+)
+
+// Get response
+let response = try await model.getResponse(request: request)
+print(response.content.first?.text ?? "No response")
+```
+
+### Streaming Responses
+
+```swift
+let request = ModelRequest(
+    messages: [.user(content: .text("Write a story about AI"))],
+    settings: ModelSettings(temperature: 0.7)
+)
+
+for try await event in try await model.getStreamedResponse(request: request) {
+    switch event {
+    case .textDelta(let delta):
+        print(delta.delta, terminator: "")
+    case .responseCompleted:
+        print("\n[Stream completed]")
+    default:
+        break
+    }
+}
+```
+
+### Tool Calling
+
+```swift
+// Define a tool
+let weatherTool = ToolDefinition(
+    function: FunctionDefinition(
+        name: "get_weather",
+        description: "Get current weather for a location",
+        parameters: ToolParameters(
+            type: "object",
+            properties: [
+                "location": ParameterSchema(
+                    type: .string,
+                    description: "City name"
+                )
+            ],
+            required: ["location"]
+        )
+    )
+)
+
+let request = ModelRequest(
+    messages: [.user(content: .text("What's the weather in Tokyo?"))],
+    tools: [weatherTool],
+    settings: ModelSettings(toolChoice: .auto)
+)
+
+let response = try await model.getResponse(request: request)
+// Handle tool calls in response.content
+```
+
+### Multimodal Inputs
+
+```swift
+let imageData = Data(contentsOf: imageURL)
+let base64Image = imageData.base64EncodedString()
+
+let request = ModelRequest(
+    messages: [
+        .user(content: .multimodal([
+            .text("What do you see in this image?"),
+            .imageUrl(ImageUrl(
+                base64: base64Image,
+                detail: .high
+            ))
+        ]))
+    ]
+)
+
+let response = try await model.getResponse(request: request)
+```
+
+## Configuration
+
+### Environment Variables
+
+```bash
+# OpenAI
+export OPENAI_API_KEY="sk-..."
+
+# Anthropic
+export ANTHROPIC_API_KEY="sk-ant-..."
+
+# Grok (xAI)
+export X_AI_API_KEY="xai-..."
+# or
+export XAI_API_KEY="xai-..."
+
+# Ollama (optional, defaults to localhost:11434)
+export PEEKABOO_OLLAMA_BASE_URL="http://localhost:11434"
+```
+
+### Provider Configuration
+
+```swift
+// Configure custom provider settings
+let openAIConfig = ProviderConfiguration.openAI(
+    apiKey: "your-api-key",
+    baseURL: URL(string: "https://api.openai.com/v1"),
+    organizationId: "org-id"
+)
+
+try await Tachikoma.shared.configureProvider(openAIConfig)
+
+// Register custom model
+await Tachikoma.shared.registerModel(name: "custom-gpt") {
+    OpenAIModel(
+        apiKey: "your-key",
+        modelName: "gpt-4-custom"
+    )
+}
+```
+
+## Architecture
+
+### Core Components
+
+#### ModelInterface
+The unified protocol that all AI providers implement:
+
+```swift
+protocol ModelInterface: Sendable {
+    var maskedApiKey: String { get }
+    func getResponse(request: ModelRequest) async throws -> ModelResponse
+    func getStreamedResponse(request: ModelRequest) async throws -> AsyncThrowingStream<StreamEvent, Error>
+}
+```
+
+#### Message System
+Type-safe message handling with support for all content types:
+
+```swift
+public enum Message: Codable, Sendable {
+    case system(id: String? = nil, content: String)
+    case user(id: String? = nil, content: MessageContent)
+    case assistant(id: String? = nil, content: [AssistantContent], status: MessageStatus = .completed)
+    case tool(id: String? = nil, toolCallId: String, content: String)
+    case reasoning(id: String? = nil, content: String)
+}
+```
+
+#### Streaming System
+Real-time event handling for streaming responses:
+
+```swift
+public enum StreamEvent {
+    case responseStarted(StreamResponseStarted)
+    case textDelta(StreamTextDelta)
+    case toolCallDelta(StreamToolCallDelta)
+    case toolCallCompleted(StreamToolCallCompleted)
+    case responseCompleted(StreamResponseCompleted)
+    case error(StreamError)
+}
+```
+
+#### Tool System
+Comprehensive function calling with generic context support:
+
+```swift
+public struct Tool<Context> {
+    public let execute: (ToolInput, Context) async throws -> ToolOutput
+    public func toToolDefinition() -> ToolDefinition
+}
+```
+
+### Provider Architecture
+
+Each provider implements the `ModelInterface` with provider-specific optimizations:
+
+- **OpenAI**: Dual API support (Chat Completions + Responses API)
+- **Anthropic**: Native SSE streaming with content blocks
+- **Grok**: OpenAI-compatible with parameter filtering
+- **Ollama**: Local inference with tool calling detection
+
+### Error Handling
+
+Comprehensive error types with recovery suggestions:
+
+```swift
+public enum TachikomaError: Error, LocalizedError {
+    case modelNotFound(String)
+    case authenticationFailed
+    case rateLimited
+    case insufficientQuota
+    case contextLengthExceeded
+    // ... more cases with detailed descriptions
+    
+    public var isRetryable: Bool { /* ... */ }
+    public var recoverySuggestion: String? { /* ... */ }
+}
+```
+
+## Advanced Usage
+
+### Custom Providers
+
+```swift
+class CustomAIModel: ModelInterface {
+    var maskedApiKey: String { "custom-***" }
+    
+    func getResponse(request: ModelRequest) async throws -> ModelResponse {
+        // Custom implementation
+    }
+    
+    func getStreamedResponse(request: ModelRequest) async throws -> AsyncThrowingStream<StreamEvent, Error> {
+        // Custom streaming implementation
+    }
+}
+
+// Register the custom provider
+await Tachikoma.shared.registerModel(name: "custom-ai") {
+    CustomAIModel()
+}
+```
+
+### Batch Processing
+
+```swift
+let requests = [
+    ModelRequest(messages: [.user(content: .text("Question 1"))]),
+    ModelRequest(messages: [.user(content: .text("Question 2"))]),
+    ModelRequest(messages: [.user(content: .text("Question 3"))])
+]
+
+let responses = try await withThrowingTaskGroup(of: ModelResponse.self) { group in
+    for request in requests {
+        group.addTask {
+            try await model.getResponse(request: request)
+        }
+    }
+    
+    var results: [ModelResponse] = []
+    for try await response in group {
+        results.append(response)
+    }
+    return results
+}
+```
+
+### Tool Context Management
+
+```swift
+struct WeatherContext {
+    let apiKey: String
+    let units: String
+}
+
+let weatherTool = Tool<WeatherContext> { input, context in
+    let location = input.parameters["location"] as? String ?? ""
+    // Use context.apiKey and context.units for API call
+    return ToolOutput(content: "Weather data for \(location)")
+}
+
+// Use with context
+let context = WeatherContext(apiKey: "weather-key", units: "metric")
+let toolDefinition = weatherTool.toToolDefinition()
+```
+
+## Testing
+
+Tachikoma includes comprehensive test coverage:
+
+```bash
+# Run tests
+swift test
+
+# Run with verbose output
+swift test --verbose
+
+# Run specific test suites
+swift test --filter "ModelProviderTests"
+```
+
+### Mock Providers
+
+```swift
+class MockModel: ModelInterface {
+    var maskedApiKey: String = "mock-***"
+    var responses: [ModelResponse] = []
+    
+    func getResponse(request: ModelRequest) async throws -> ModelResponse {
+        return responses.removeFirst()
+    }
+}
+
+// Use in tests
+let mockModel = MockModel()
+mockModel.responses = [/* test responses */]
+await Tachikoma.shared.registerModel(name: "mock") { mockModel }
+```
+
+## Performance Considerations
+
+### Caching
+- Model instances are cached by default
+- Clear cache with `ModelProvider.shared.clearCache()`
+- Disable caching for specific models if needed
+
+### Memory Management
+- Streaming responses use `AsyncThrowingStream` for memory efficiency
+- Large responses are processed incrementally
+- Tool contexts should be lightweight for optimal performance
+
+### Concurrency
+- All APIs are actor-safe and Swift 6 compliant
+- Use `TaskGroup` for parallel processing
+- Respect rate limits with proper error handling
+
+## Migration Guide
+
+### From PeekabooCore
+
+If migrating from PeekabooCore's AI system:
+
+1. Replace `PeekabooError` with `TachikomaError`
+2. Update import statements
+3. Use `Tachikoma.shared.getModel()` instead of direct model creation
+4. Update streaming event handling for new event types
+
+### Version History
+
+- **v1.0.0**: Initial release with Swift 6 support
+- Core providers: OpenAI, Anthropic, Grok, Ollama
+- Complete tool calling and streaming support
+
+## Contributing
+
+1. Fork the repository
+2. Create a feature branch
+3. Ensure Swift 6 strict mode compliance
+4. Add comprehensive tests
+5. Update documentation
+6. Submit a pull request
+
+## License
+
+Tachikoma is available under the MIT License. See LICENSE for details.
+
+## Support
+
+- **Issues**: [GitHub Issues](https://github.com/steipete/Tachikoma/issues)
+- **Discussions**: [GitHub Discussions](https://github.com/steipete/Tachikoma/discussions)
+- **Documentation**: [API Reference](https://steipete.github.io/Tachikoma/)
+
+---
+
+Built with ❤️ for the Swift AI community.
diff --git a/Sources/Core/MessageTypes.swift b/Sources/Core/MessageTypes.swift
new file mode 100644
index 0000000..f364eb6
--- /dev/null
+++ b/Sources/Core/MessageTypes.swift
@@ -0,0 +1,366 @@
+import Foundation
+
+// MARK: - Unified Message Type
+
+/// Unified message enum that provides type-safe message handling
+public enum Message: Codable, Sendable {
+    case system(id: String? = nil, content: String)
+    case user(id: String? = nil, content: MessageContent)
+    case assistant(id: String? = nil, content: [AssistantContent], status: MessageStatus = .completed)
+    case tool(id: String? = nil, toolCallId: String, content: String)
+    case reasoning(id: String? = nil, content: String)
+
+    // MARK: - Properties
+
+    /// Get the message type
+    public var type: MessageType {
+        switch self {
+        case .system: .system
+        case .user: .user
+        case .assistant: .assistant
+        case .tool: .tool
+        case .reasoning: .reasoning
+        }
+    }
+
+    /// Get the message ID
+    public var id: String? {
+        switch self {
+        case let .system(id, _), let .user(id, _), let .assistant(id, _, _),
+             let .tool(id, _, _), let .reasoning(id, _):
+            id
+        }
+    }
+
+    // MARK: - Codable Implementation
+
+    private enum CodingKeys: String, CodingKey {
+        case type, id, content, status, toolCallId
+    }
+
+    public enum MessageType: String, Codable {
+        case system, user, assistant, tool, reasoning
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let type = try container.decode(MessageType.self, forKey: .type)
+        let id = try container.decodeIfPresent(String.self, forKey: .id)
+
+        switch type {
+        case .system:
+            let content = try container.decode(String.self, forKey: .content)
+            self = .system(id: id, content: content)
+
+        case .user:
+            let content = try container.decode(MessageContent.self, forKey: .content)
+            self = .user(id: id, content: content)
+
+        case .assistant:
+            let content = try container.decode([AssistantContent].self, forKey: .content)
+            let status = try container.decodeIfPresent(MessageStatus.self, forKey: .status) ?? .completed
+            self = .assistant(id: id, content: content, status: status)
+
+        case .tool:
+            let toolCallId = try container.decode(String.self, forKey: .toolCallId)
+            let content = try container.decode(String.self, forKey: .content)
+            self = .tool(id: id, toolCallId: toolCallId, content: content)
+
+        case .reasoning:
+            let content = try container.decode(String.self, forKey: .content)
+            self = .reasoning(id: id, content: content)
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(self.type, forKey: .type)
+
+        switch self {
+        case let .system(id, content):
+            try container.encodeIfPresent(id, forKey: .id)
+            try container.encode(content, forKey: .content)
+
+        case let .user(id, content):
+            try container.encodeIfPresent(id, forKey: .id)
+            try container.encode(content, forKey: .content)
+
+        case let .assistant(id, content, status):
+            try container.encodeIfPresent(id, forKey: .id)
+            try container.encode(content, forKey: .content)
+            try container.encode(status, forKey: .status)
+
+        case let .tool(id, toolCallId, content):
+            try container.encodeIfPresent(id, forKey: .id)
+            try container.encode(toolCallId, forKey: .toolCallId)
+            try container.encode(content, forKey: .content)
+
+        case let .reasoning(id, content):
+            try container.encodeIfPresent(id, forKey: .id)
+            try container.encode(content, forKey: .content)
+        }
+    }
+}
+
+// MARK: - Content Types
+
+/// User message content variants
+public enum MessageContent: Codable, Sendable {
+    case text(String)
+    case image(ImageContent)
+    case file(FileContent)
+    case audio(AudioContent)
+    case multimodal([MessageContentPart])
+
+    // Custom coding for enum
+    enum CodingKeys: String, CodingKey {
+        case type, value
+    }
+
+    enum ContentType: String, Codable {
+        case text, image, file, audio, multimodal
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let type = try container.decode(ContentType.self, forKey: .type)
+
+        switch type {
+        case .text:
+            let value = try container.decode(String.self, forKey: .value)
+            self = .text(value)
+        case .image:
+            let value = try container.decode(ImageContent.self, forKey: .value)
+            self = .image(value)
+        case .file:
+            let value = try container.decode(FileContent.self, forKey: .value)
+            self = .file(value)
+        case .audio:
+            let value = try container.decode(AudioContent.self, forKey: .value)
+            self = .audio(value)
+        case .multimodal:
+            let value = try container.decode([MessageContentPart].self, forKey: .value)
+            self = .multimodal(value)
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+
+        switch self {
+        case let .text(value):
+            try container.encode(ContentType.text, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .image(value):
+            try container.encode(ContentType.image, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .file(value):
+            try container.encode(ContentType.file, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .audio(value):
+            try container.encode(ContentType.audio, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .multimodal(value):
+            try container.encode(ContentType.multimodal, forKey: .type)
+            try container.encode(value, forKey: .value)
+        }
+    }
+}
+
+/// Image content for messages
+public struct ImageContent: Codable, Sendable {
+    public let url: String?
+    public let base64: String?
+    public let detail: ImageDetail?
+
+    public enum ImageDetail: String, Codable, Sendable {
+        case auto, low, high
+    }
+
+    public init(url: String? = nil, base64: String? = nil, detail: ImageDetail? = nil) {
+        self.url = url
+        self.base64 = base64
+        self.detail = detail
+    }
+}
+
+/// File content for messages
+public struct FileContent: Codable, Sendable {
+    public let id: String?
+    public let url: String?
+    public let name: String?
+    public let filename: String?
+    public let content: String?
+    public let mimeType: String?
+
+    public init(
+        id: String? = nil,
+        url: String? = nil,
+        name: String? = nil,
+        filename: String? = nil,
+        content: String? = nil,
+        mimeType: String? = nil)
+    {
+        self.id = id
+        self.url = url
+        self.name = name
+        self.filename = filename
+        self.content = content
+        self.mimeType = mimeType
+    }
+    
+    // Convenience constructor for test compatibility
+    public init(filename: String, content: String, mimeType: String) {
+        self.init(name: filename, filename: filename, content: content, mimeType: mimeType)
+    }
+}
+
+/// Audio content for messages
+public struct AudioContent: Codable, Sendable {
+    public let url: String?
+    public let base64: String?
+    public let transcript: String?
+    public let duration: TimeInterval?
+    public let mimeType: String?
+
+    public init(
+        url: String? = nil,
+        base64: String? = nil,
+        transcript: String? = nil,
+        duration: TimeInterval? = nil,
+        mimeType: String? = nil)
+    {
+        self.url = url
+        self.base64 = base64
+        self.transcript = transcript
+        self.duration = duration
+        self.mimeType = mimeType
+    }
+}
+
+/// Multimodal content part
+public struct MessageContentPart: Codable, Sendable {
+    public let type: String
+    public let text: String?
+    public let imageUrl: ImageContent?
+
+    public init(type: String, text: String? = nil, imageUrl: ImageContent? = nil) {
+        self.type = type
+        self.text = text
+        self.imageUrl = imageUrl
+    }
+}
+
+/// Assistant response content variants
+public enum AssistantContent: Codable, Sendable {
+    case outputText(String)
+    case refusal(String)
+    case toolCall(ToolCallItem)
+
+    // Custom coding
+    enum CodingKeys: String, CodingKey {
+        case type, value
+    }
+
+    enum ContentType: String, Codable {
+        case text, refusal, toolCall
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let type = try container.decode(ContentType.self, forKey: .type)
+
+        switch type {
+        case .text:
+            let value = try container.decode(String.self, forKey: .value)
+            self = .outputText(value)
+        case .refusal:
+            let value = try container.decode(String.self, forKey: .value)
+            self = .refusal(value)
+        case .toolCall:
+            let value = try container.decode(ToolCallItem.self, forKey: .value)
+            self = .toolCall(value)
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+
+        switch self {
+        case let .outputText(value):
+            try container.encode(ContentType.text, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .refusal(value):
+            try container.encode(ContentType.refusal, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .toolCall(value):
+            try container.encode(ContentType.toolCall, forKey: .type)
+            try container.encode(value, forKey: .value)
+        }
+    }
+}
+
+// MARK: - Tool Call Types
+
+/// Tool call item representing a function invocation
+public struct ToolCallItem: Codable, Sendable {
+    public let id: String
+    public let type: ToolCallType
+    public let function: FunctionCall
+    public let status: ToolCallStatus?
+
+    public init(id: String, type: ToolCallType = .function, function: FunctionCall, status: ToolCallStatus? = nil) {
+        self.id = id
+        self.type = type
+        self.function = function
+        self.status = status
+    }
+}
+
+/// Types of tool calls
+public enum ToolCallType: String, Codable, Sendable {
+    case function
+    case hosted = "hosted_tool"
+    case computer
+}
+
+/// Function call details
+public struct FunctionCall: Codable, Sendable {
+    public let name: String
+    public let arguments: String
+
+    public init(name: String, arguments: String) {
+        self.name = name
+        self.arguments = arguments
+    }
+}
+
+/// Tool call execution status
+public enum ToolCallStatus: String, Codable, Sendable {
+    case inProgress = "in_progress"
+    case completed
+    case failed
+}
+
+/// Message processing status
+public enum MessageStatus: String, Codable, Sendable {
+    case inProgress = "in_progress"
+    case completed
+    case incomplete
+}
+
+// MARK: - Helper Extensions
+
+extension AssistantContent {
+    /// Extract text content if available
+    public var textContent: String? {
+        switch self {
+        case let .outputText(text):
+            text
+        case let .refusal(text):
+            text
+        case .toolCall:
+            nil
+        }
+    }
+}
\ No newline at end of file
diff --git a/Sources/Core/ModelInterface.swift b/Sources/Core/ModelInterface.swift
new file mode 100644
index 0000000..c1eb5ca
--- /dev/null
+++ b/Sources/Core/ModelInterface.swift
@@ -0,0 +1,424 @@
+import Foundation
+
+// MARK: - Model Interface Protocol
+
+/// Protocol defining the interface for AI model providers
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public protocol ModelInterface: Sendable {
+    /// Get a non-streaming response from the model
+    /// - Parameter request: The model request containing messages, tools, and settings
+    /// - Returns: The model response
+    func getResponse(request: ModelRequest) async throws -> ModelResponse
+
+    /// Get a streaming response from the model
+    /// - Parameter request: The model request containing messages, tools, and settings
+    /// - Returns: An async stream of events
+    func getStreamedResponse(request: ModelRequest) async throws -> AsyncThrowingStream<StreamEvent, any Error>
+
+    /// Get a masked version of the API key for debugging
+    /// Returns the first 6 and last 2 characters of the API key
+    /// - Returns: Masked API key string (e.g., "sk-ant...AA")
+    var maskedApiKey: String { get }
+}
+
+// MARK: - Model Request & Response Types
+
+/// Request to send to a model
+public struct ModelRequest: Codable, Sendable {
+    /// The messages to send to the model
+    public let messages: [Message]
+
+    /// Available tools for the model to use
+    public let tools: [ToolDefinition]?
+
+    /// Model-specific settings
+    public let settings: ModelSettings
+
+    /// System instructions (some models support this separately from messages)
+    public let systemInstructions: String?
+
+    public init(
+        messages: [Message],
+        tools: [ToolDefinition]? = nil,
+        settings: ModelSettings,
+        systemInstructions: String? = nil)
+    {
+        self.messages = messages
+        self.tools = tools
+        self.settings = settings
+        self.systemInstructions = systemInstructions
+    }
+}
+
+/// Response from a model
+public struct ModelResponse: Codable, Sendable {
+    /// Unique identifier for the response
+    public let id: String
+
+    /// The model that generated the response
+    public let model: String?
+
+    /// Content returned by the model
+    public let content: [AssistantContent]
+
+    /// Token usage statistics
+    public let usage: Usage?
+
+    /// Whether the response was flagged for safety
+    public let flagged: Bool
+
+    /// Reason for flagging if applicable
+    public let flaggedCategories: [String]?
+
+    /// Finish reason
+    public let finishReason: FinishReason?
+
+    public init(
+        id: String,
+        model: String? = nil,
+        content: [AssistantContent],
+        usage: Usage? = nil,
+        flagged: Bool = false,
+        flaggedCategories: [String]? = nil,
+        finishReason: FinishReason? = nil)
+    {
+        self.id = id
+        self.model = model
+        self.content = content
+        self.usage = usage
+        self.flagged = flagged
+        self.flaggedCategories = flaggedCategories
+        self.finishReason = finishReason
+    }
+}
+
+// MARK: - Model Settings
+
+/// Settings for model behavior
+public struct ModelSettings: Codable, Sendable {
+    /// The model name/identifier
+    public let modelName: String
+
+    /// Temperature for randomness (0.0 to 2.0)
+    public let temperature: Double?
+
+    /// Top-p sampling parameter
+    public let topP: Double?
+
+    /// Maximum tokens to generate
+    public let maxTokens: Int?
+
+    /// Frequency penalty (-2.0 to 2.0)
+    public let frequencyPenalty: Double?
+
+    /// Presence penalty (-2.0 to 2.0)
+    public let presencePenalty: Double?
+
+    /// Stop sequences
+    public let stopSequences: [String]?
+
+    /// Tool choice setting
+    public let toolChoice: ToolChoice?
+
+    /// Whether to use parallel tool calls
+    public let parallelToolCalls: Bool?
+
+    /// Response format
+    public let responseFormat: ResponseFormat?
+
+    /// Seed for deterministic generation
+    public let seed: Int?
+
+    /// User identifier for tracking
+    public let user: String?
+
+    /// Additional provider-specific parameters
+    public let additionalParameters: ModelParameters?
+
+    public init(
+        modelName: String,
+        temperature: Double? = nil,
+        topP: Double? = nil,
+        maxTokens: Int? = nil,
+        frequencyPenalty: Double? = nil,
+        presencePenalty: Double? = nil,
+        stopSequences: [String]? = nil,
+        toolChoice: ToolChoice? = nil,
+        parallelToolCalls: Bool? = nil,
+        responseFormat: ResponseFormat? = nil,
+        seed: Int? = nil,
+        user: String? = nil,
+        additionalParameters: ModelParameters? = nil)
+    {
+        self.modelName = modelName
+        self.temperature = temperature
+        self.topP = topP
+        self.maxTokens = maxTokens
+        self.frequencyPenalty = frequencyPenalty
+        self.presencePenalty = presencePenalty
+        self.stopSequences = stopSequences
+        self.toolChoice = toolChoice
+        self.parallelToolCalls = parallelToolCalls
+        self.responseFormat = responseFormat
+        self.seed = seed
+        self.user = user
+        self.additionalParameters = additionalParameters
+    }
+
+    /// Default settings for Claude Opus 4
+    public static var `default`: ModelSettings {
+        ModelSettings(modelName: "claude-opus-4-20250514")
+    }
+    
+    // MARK: - Convenience Constructors
+    
+    /// Create settings with just specified parameters, using Claude Opus 4 as default model
+    public init(
+        temperature: Double? = nil,
+        topP: Double? = nil,
+        maxTokens: Int? = nil,
+        frequencyPenalty: Double? = nil,
+        presencePenalty: Double? = nil,
+        stopSequences: [String]? = nil,
+        toolChoice: ToolChoice? = nil,
+        parallelToolCalls: Bool? = nil,
+        responseFormat: ResponseFormat? = nil,
+        seed: Int? = nil,
+        user: String? = nil,
+        additionalParameters: ModelParameters? = nil)
+    {
+        self.init(
+            modelName: "claude-opus-4-20250514",
+            temperature: temperature,
+            topP: topP,
+            maxTokens: maxTokens,
+            frequencyPenalty: frequencyPenalty,
+            presencePenalty: presencePenalty,
+            stopSequences: stopSequences,
+            toolChoice: toolChoice,
+            parallelToolCalls: parallelToolCalls,
+            responseFormat: responseFormat,
+            seed: seed,
+            user: user,
+            additionalParameters: additionalParameters
+        )
+    }
+    
+    /// Convenience constructors for specific API types and reasoning parameters
+    public init(
+        apiType: String,
+        modelName: String = "claude-opus-4-20250514")
+    {
+        let params = ModelParameters([
+            "apiType": ModelParameters.Value.string(apiType)
+        ])
+        self.init(modelName: modelName, additionalParameters: params)
+    }
+    
+    public init(
+        reasoningEffort: String,
+        reasoning: [String: String]? = nil,
+        temperature: Double? = nil,
+        modelName: String = "o3")
+    {
+        var params: [String: ModelParameters.Value] = [
+            "reasoningEffort": ModelParameters.Value.string(reasoningEffort)
+        ]
+        if let reasoning = reasoning {
+            let reasoningValue = reasoning.mapValues { ModelParameters.Value.string($0) }
+            params["reasoning"] = ModelParameters.Value.dictionary(reasoningValue)
+        }
+        let modelParams = ModelParameters(params)
+        self.init(
+            modelName: modelName,
+            temperature: temperature,
+            additionalParameters: modelParams
+        )
+    }
+
+    // Custom coding for additionalParameters
+    enum CodingKeys: String, CodingKey {
+        case modelName, temperature, topP, maxTokens
+        case frequencyPenalty, presencePenalty, stopSequences
+        case toolChoice, parallelToolCalls, responseFormat
+        case seed, user, additionalParameters
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+
+        self.modelName = try container.decode(String.self, forKey: .modelName)
+        self.temperature = try container.decodeIfPresent(Double.self, forKey: .temperature)
+        self.topP = try container.decodeIfPresent(Double.self, forKey: .topP)
+        self.maxTokens = try container.decodeIfPresent(Int.self, forKey: .maxTokens)
+        self.frequencyPenalty = try container.decodeIfPresent(Double.self, forKey: .frequencyPenalty)
+        self.presencePenalty = try container.decodeIfPresent(Double.self, forKey: .presencePenalty)
+        self.stopSequences = try container.decodeIfPresent([String].self, forKey: .stopSequences)
+        self.toolChoice = try container.decodeIfPresent(ToolChoice.self, forKey: .toolChoice)
+        self.parallelToolCalls = try container.decodeIfPresent(Bool.self, forKey: .parallelToolCalls)
+        self.responseFormat = try container.decodeIfPresent(ResponseFormat.self, forKey: .responseFormat)
+        self.seed = try container.decodeIfPresent(Int.self, forKey: .seed)
+        self.user = try container.decodeIfPresent(String.self, forKey: .user)
+
+        // Decode additional parameters
+        self.additionalParameters = try container.decodeIfPresent(ModelParameters.self, forKey: .additionalParameters)
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+
+        try container.encode(self.modelName, forKey: .modelName)
+        try container.encodeIfPresent(self.temperature, forKey: .temperature)
+        try container.encodeIfPresent(self.topP, forKey: .topP)
+        try container.encodeIfPresent(self.maxTokens, forKey: .maxTokens)
+        try container.encodeIfPresent(self.frequencyPenalty, forKey: .frequencyPenalty)
+        try container.encodeIfPresent(self.presencePenalty, forKey: .presencePenalty)
+        try container.encodeIfPresent(self.stopSequences, forKey: .stopSequences)
+        try container.encodeIfPresent(self.toolChoice, forKey: .toolChoice)
+        try container.encodeIfPresent(self.parallelToolCalls, forKey: .parallelToolCalls)
+        try container.encodeIfPresent(self.responseFormat, forKey: .responseFormat)
+        try container.encodeIfPresent(self.seed, forKey: .seed)
+        try container.encodeIfPresent(self.user, forKey: .user)
+
+        // Encode additional parameters
+        try container.encodeIfPresent(self.additionalParameters, forKey: .additionalParameters)
+    }
+}
+
+// MARK: - Tool Choice
+
+/// Tool choice setting for models
+public enum ToolChoice: Codable, Sendable, Equatable {
+    case auto
+    case none
+    case required
+    case specific(toolName: String)
+
+    // Custom coding
+    enum CodingKeys: String, CodingKey {
+        case type, toolName
+    }
+
+    enum ChoiceType: String, Codable {
+        case auto, none, required, specific
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let type = try container.decode(ChoiceType.self, forKey: .type)
+
+        switch type {
+        case .auto:
+            self = .auto
+        case .none:
+            self = .none
+        case .required:
+            self = .required
+        case .specific:
+            let toolName = try container.decode(String.self, forKey: .toolName)
+            self = .specific(toolName: toolName)
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+
+        switch self {
+        case .auto:
+            try container.encode(ChoiceType.auto, forKey: .type)
+        case .none:
+            try container.encode(ChoiceType.none, forKey: .type)
+        case .required:
+            try container.encode(ChoiceType.required, forKey: .type)
+        case let .specific(toolName):
+            try container.encode(ChoiceType.specific, forKey: .type)
+            try container.encode(toolName, forKey: .toolName)
+        }
+    }
+}
+
+// MARK: - Response Format
+
+/// Response format specification
+public struct ResponseFormat: Codable, Sendable {
+    public let type: ResponseFormatType
+    public let jsonSchema: JSONSchema?
+
+    public init(type: ResponseFormatType, jsonSchema: JSONSchema? = nil) {
+        self.type = type
+        self.jsonSchema = jsonSchema
+    }
+
+    /// Plain text response
+    public static var text: ResponseFormat {
+        ResponseFormat(type: .text)
+    }
+
+    /// JSON object response
+    public static var jsonObject: ResponseFormat {
+        ResponseFormat(type: .jsonObject)
+    }
+}
+
+/// Response format types
+public enum ResponseFormatType: String, Codable, Sendable {
+    case text
+    case jsonObject = "json_object"
+    case jsonSchema = "json_schema"
+}
+
+/// JSON schema specification
+public struct JSONSchema: Codable, Sendable {
+    public let name: String
+    public let strict: Bool
+    private let schemaData: Data // Store as raw JSON data
+
+    // Custom coding for schema
+    enum CodingKeys: String, CodingKey {
+        case name, strict, schema
+    }
+
+    public init(name: String, strict: Bool = true, schema: [String: Any]) throws {
+        self.name = name
+        self.strict = strict
+        self.schemaData = try JSONSerialization.data(withJSONObject: schema)
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        self.name = try container.decode(String.self, forKey: .name)
+        self.strict = try container.decode(Bool.self, forKey: .strict)
+        self.schemaData = try container.decode(Data.self, forKey: .schema)
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(self.name, forKey: .name)
+        try container.encode(self.strict, forKey: .strict)
+        try container.encode(self.schemaData, forKey: .schema)
+    }
+
+    /// Get the schema as a dictionary
+    public func getSchema() throws -> [String: Any] {
+        guard let dict = try JSONSerialization.jsonObject(with: schemaData) as? [String: Any] else {
+            throw TachikomaError.invalidConfiguration("Invalid JSON schema data")
+        }
+        return dict
+    }
+}
+
+// MARK: - Model Provider Protocol
+
+/// Protocol for model provider factories
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public protocol ModelProviderProtocol {
+    /// Get a model by name
+    /// - Parameter modelName: The name of the model to retrieve
+    /// - Returns: A model instance conforming to ModelInterface
+    func getModel(modelName: String) throws -> any ModelInterface
+}
+
+// MARK: - Model Errors
+
+// MARK: - Note
+// ModelError is defined in TachikomaError.swift to avoid duplication
\ No newline at end of file
diff --git a/Sources/Core/ModelParameters.swift b/Sources/Core/ModelParameters.swift
new file mode 100644
index 0000000..d0f9175
--- /dev/null
+++ b/Sources/Core/ModelParameters.swift
@@ -0,0 +1,240 @@
+import Foundation
+
+// MARK: - Model Parameters
+
+/// Type-safe representation of additional model parameters
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct ModelParameters: Codable, Sendable {
+    private let storage: [String: Value]
+
+    /// Supported parameter value types
+    public enum Value: Codable, Sendable {
+        case string(String)
+        case int(Int)
+        case double(Double)
+        case bool(Bool)
+        case dictionary([String: Value])
+        case array([Value])
+
+        // MARK: - Codable
+
+        public init(from decoder: any Decoder) throws {
+            let container = try decoder.singleValueContainer()
+
+            if let intValue = try? container.decode(Int.self) {
+                self = .int(intValue)
+            } else if let doubleValue = try? container.decode(Double.self) {
+                self = .double(doubleValue)
+            } else if let boolValue = try? container.decode(Bool.self) {
+                self = .bool(boolValue)
+            } else if let stringValue = try? container.decode(String.self) {
+                self = .string(stringValue)
+            } else if let dictValue = try? container.decode([String: Value].self) {
+                self = .dictionary(dictValue)
+            } else if let arrayValue = try? container.decode([Value].self) {
+                self = .array(arrayValue)
+            } else {
+                throw DecodingError.dataCorruptedError(
+                    in: container,
+                    debugDescription: "Unable to decode ModelParameters.Value")
+            }
+        }
+
+        public func encode(to encoder: any Encoder) throws {
+            var container = encoder.singleValueContainer()
+
+            switch self {
+            case let .string(value):
+                try container.encode(value)
+            case let .int(value):
+                try container.encode(value)
+            case let .double(value):
+                try container.encode(value)
+            case let .bool(value):
+                try container.encode(value)
+            case let .dictionary(value):
+                try container.encode(value)
+            case let .array(value):
+                try container.encode(value)
+            }
+        }
+
+        /// Convert to raw value for JSON serialization
+        public var rawValue: Any {
+            switch self {
+            case let .string(value):
+                value
+            case let .int(value):
+                value
+            case let .double(value):
+                value
+            case let .bool(value):
+                value
+            case let .dictionary(dict):
+                dict.mapValues { $0.rawValue }
+            case let .array(array):
+                array.map(\.rawValue)
+            }
+        }
+    }
+
+    // MARK: - Initialization
+
+    public init(_ storage: [String: Value] = [:]) {
+        self.storage = storage
+    }
+
+    /// Initialize from a dictionary of raw values
+    public init(from rawValues: [String: Any]) {
+        var convertedStorage: [String: Value] = [:]
+        for (key, value) in rawValues {
+            if let converted = Self.convertToValue(value) {
+                convertedStorage[key] = converted
+            }
+        }
+        self.storage = convertedStorage
+    }
+
+    /// Convert any value to our Value enum
+    private static func convertToValue(_ value: Any) -> Value? {
+        switch value {
+        case let string as String:
+            return .string(string)
+        case let int as Int:
+            return .int(int)
+        case let double as Double:
+            return .double(double)
+        case let bool as Bool:
+            return .bool(bool)
+        case let dict as [String: Any]:
+            var converted: [String: Value] = [:]
+            for (k, v) in dict {
+                if let convertedValue = convertToValue(v) {
+                    converted[k] = convertedValue
+                }
+            }
+            return .dictionary(converted)
+        case let array as [Any]:
+            let converted = array.compactMap { self.convertToValue($0) }
+            return .array(converted)
+        default:
+            return nil
+        }
+    }
+
+    // MARK: - Access Methods
+
+    public subscript(key: String) -> Value? { self.storage[key] }
+
+    public func string(_ key: String) -> String? {
+        guard case let .string(value) = storage[key] else { return nil }
+        return value
+    }
+
+    public func int(_ key: String) -> Int? {
+        guard case let .int(value) = storage[key] else { return nil }
+        return value
+    }
+
+    public func double(_ key: String) -> Double? {
+        guard case let .double(value) = storage[key] else { return nil }
+        return value
+    }
+
+    public func bool(_ key: String) -> Bool? {
+        guard case let .bool(value) = storage[key] else { return nil }
+        return value
+    }
+
+    /// Get the raw dictionary for JSON serialization
+    public var rawDictionary: [String: Any] {
+        self.storage.mapValues { $0.rawValue }
+    }
+
+    /// Check if empty
+    public var isEmpty: Bool {
+        self.storage.isEmpty
+    }
+
+    // MARK: - Mutating Methods
+    
+    /// Set a parameter value
+    public mutating func set(_ key: String, value: Any) {
+        if let converted = Self.convertToValue(value) {
+            var newStorage = self.storage
+            newStorage[key] = converted
+            self = ModelParameters(newStorage)
+        }
+    }
+    
+    /// Get a parameter value
+    public func get(_ key: String) -> Any? {
+        return self.storage[key]?.rawValue
+    }
+
+    // MARK: - Builder Methods
+
+    public func with(_ key: String, value: String) -> ModelParameters {
+        var newStorage = self.storage
+        newStorage[key] = .string(value)
+        return ModelParameters(newStorage)
+    }
+
+    public func with(_ key: String, value: Int) -> ModelParameters {
+        var newStorage = self.storage
+        newStorage[key] = .int(value)
+        return ModelParameters(newStorage)
+    }
+
+    public func with(_ key: String, value: Double) -> ModelParameters {
+        var newStorage = self.storage
+        newStorage[key] = .double(value)
+        return ModelParameters(newStorage)
+    }
+
+    public func with(_ key: String, value: Bool) -> ModelParameters {
+        var newStorage = self.storage
+        newStorage[key] = .bool(value)
+        return ModelParameters(newStorage)
+    }
+
+    public func with(_ key: String, value: [String: Any]) -> ModelParameters {
+        guard let converted = Self.convertToValue(value) else { return self }
+        var newStorage = self.storage
+        newStorage[key] = converted
+        return ModelParameters(newStorage)
+    }
+
+    // MARK: - Codable
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.singleValueContainer()
+        self.storage = try container.decode([String: Value].self)
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.singleValueContainer()
+        try container.encode(self.storage)
+    }
+}
+
+// MARK: - Convenience Builders
+
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+extension ModelParameters {
+    /// Create parameters for OpenAI o3/o4 models
+    public static func o3Parameters(
+        reasoningEffort: String = "medium",
+        maxCompletionTokens: Int = 32768) -> ModelParameters
+    {
+        ModelParameters()
+            .with("reasoning_effort", value: reasoningEffort)
+            .with("max_completion_tokens", value: maxCompletionTokens)
+            .with("reasoning", value: ["summary": "detailed"])
+    }
+
+    /// Create parameters with API type
+    public static func withAPIType(_ apiType: String) -> ModelParameters {
+        ModelParameters().with("apiType", value: apiType)
+    }
+}
\ No newline at end of file
diff --git a/Sources/Core/ModelProvider.swift b/Sources/Core/ModelProvider.swift
new file mode 100644
index 0000000..487ee4e
--- /dev/null
+++ b/Sources/Core/ModelProvider.swift
@@ -0,0 +1,650 @@
+import Foundation
+
+// MARK: - Model Provider
+
+/// Singleton provider for managing model instances in Tachikoma
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public actor ModelProvider {
+    /// Shared instance
+    public static let shared = ModelProvider()
+
+    /// Registered model factories
+    private var modelFactories: [String: @Sendable () throws -> any ModelInterface] = [:]
+
+    /// Model instance cache
+    private var modelCache: [String: any ModelInterface] = [:]
+
+    private init() {
+        // Register default models when initialized
+        Task {
+            await self.registerDefaultModels()
+        }
+    }
+
+    // MARK: - Public Methods
+
+    /// Register a model factory
+    /// - Parameters:
+    ///   - name: The model name
+    ///   - factory: Factory closure that creates the model
+    public func register(
+        modelName: String,
+        factory: @escaping @Sendable () throws -> any ModelInterface)
+    {
+        self.modelFactories[modelName] = factory
+        // Clear cache for this model
+        self.modelCache.removeValue(forKey: modelName)
+    }
+
+    /// Get a model by name
+    /// - Parameter modelName: The name of the model
+    /// - Returns: A model instance
+    /// - Throws: TachikomaError if model not found
+    public func getModel(modelName: String) throws -> any ModelInterface {
+        // Check cache first
+        if let cached = modelCache[modelName] {
+            return cached
+        }
+
+        // Check for custom provider first (format: provider-id/model-path)
+        if let slashIndex = modelName.firstIndex(of: "/") {
+            let providerId = String(modelName[..<slashIndex])
+            let modelPath = String(modelName[modelName.index(after: slashIndex)...])
+            
+            if let model = try? createCustomProviderModel(providerId: providerId, modelPath: modelPath) {
+                self.modelCache[modelName] = model
+                return model
+            }
+        }
+
+        // Try exact match for built-in models
+        if let factory = modelFactories[modelName] {
+            let model = try factory()
+            self.modelCache[modelName] = model
+            return model
+        }
+
+        // Try lenient matching for shortened names
+        if let resolvedName = resolveLenientModelName(modelName),
+           let factory = modelFactories[resolvedName]
+        {
+            let model = try factory()
+            // Cache with both original and resolved names
+            self.modelCache[modelName] = model
+            self.modelCache[resolvedName] = model
+            return model
+        }
+
+        // Model not found in registry
+        throw TachikomaError.modelNotFound(modelName)
+    }
+
+    /// List all registered models
+    public func listModels() -> [String] {
+        Array(self.modelFactories.keys).sorted()
+    }
+
+    /// Clear model cache
+    public func clearCache() {
+        self.modelCache.removeAll()
+    }
+
+    /// Clear all model registrations and cache (useful for testing)
+    public func clearAll() async {
+        self.modelCache.removeAll()
+        self.modelFactories.removeAll()
+        // Re-register default models
+        await self.registerDefaultModels()
+    }
+
+    /// Unregister a model
+    public func unregister(modelName: String) {
+        self.modelFactories.removeValue(forKey: modelName)
+        self.modelCache.removeValue(forKey: modelName)
+    }
+
+    // MARK: - Private Methods
+
+    private func registerDefaultModels() async {
+        // Register OpenAI models
+        self.registerOpenAIModels()
+
+        // Register Anthropic models
+        self.registerAnthropicModels()
+
+        // Register Grok models
+        self.registerGrokModels()
+
+        // Register Ollama models
+        self.registerOllamaModels()
+    }
+
+    /// Resolve lenient model names to their full versions
+    private func resolveLenientModelName(_ modelName: String) -> String? {
+        let lowercased = modelName.lowercased()
+
+        // Claude model shortcuts
+        if lowercased == "claude-4-opus" || lowercased == "claude-opus-4" || lowercased == "claude-opus" {
+            return "claude-opus-4-20250514"
+        }
+        if lowercased == "claude-4-sonnet" || lowercased == "claude-sonnet-4" || lowercased == "claude-sonnet" {
+            return "claude-sonnet-4-20250514"
+        }
+        if lowercased == "claude-3.7-sonnet" || lowercased == "claude-3-7-sonnet" || lowercased == "claude-sonnet-3.7" {
+            return "claude-3-7-sonnet"
+        }
+        if lowercased == "claude-3.5-sonnet" || lowercased == "claude-3-5-sonnet" || lowercased == "claude-sonnet-3.5" {
+            return "claude-3-5-sonnet"
+        }
+        if lowercased == "claude-3.5-haiku" || lowercased == "claude-3-5-haiku" || lowercased == "claude-haiku-3.5" {
+            return "claude-3-5-haiku"
+        }
+        if lowercased == "claude-3.5-opus" || lowercased == "claude-3-5-opus" || lowercased == "claude-opus-3.5" {
+            return "claude-3-5-opus"
+        }
+        if lowercased == "claude" {
+            return "claude-opus-4-20250514" // Default to Claude Opus 4
+        }
+
+        // OpenAI model shortcuts
+        if lowercased == "gpt4" || lowercased == "gpt-4" {
+            return "gpt-4.1"
+        }
+        if lowercased == "gpt4-mini" || lowercased == "gpt-4-mini" {
+            return "gpt-4.1-mini"
+        }
+        if lowercased == "gpt" {
+            return "gpt-4.1" // Default to latest GPT
+        }
+
+        // Grok model shortcuts
+        if lowercased == "grok" || lowercased == "grok4" || lowercased == "grok-4" {
+            return "grok-4-0709"
+        }
+        if lowercased == "grok3" || lowercased == "grok-3" {
+            return "grok-3"
+        }
+        if lowercased == "grok2" || lowercased == "grok-2" {
+            return "grok-2-vision-1212"
+        }
+
+        // Ollama model shortcuts
+        if lowercased == "ollama" || lowercased == "llama" {
+            return "llama3.3" // Default to llama3.3 - best for agent tasks with tool support
+        }
+        if lowercased == "llama3" || lowercased == "llama-3" {
+            return "llama3.3" // Default to latest llama 3.x
+        }
+
+        // Check if it's a partial match for any registered model
+        let registeredModels = Array(modelFactories.keys)
+        for model in registeredModels {
+            if model.lowercased().contains(lowercased) || lowercased.contains(model.lowercased()) {
+                return model
+            }
+        }
+
+        return nil
+    }
+
+    private func registerOpenAIModels() {
+        let models = [
+            // GPT-4o series
+            "gpt-4o",
+            "gpt-4o-mini",
+
+            // GPT-4.1 series
+            "gpt-4.1",
+            "gpt-4.1-mini",
+
+            // o3 series (Responses API only)
+            "o3",
+            "o3-mini",
+            "o3-pro",
+
+            // o4 series (Responses API only)
+            "o4-mini",
+        ]
+
+        for modelName in models {
+            self.register(modelName: modelName) {
+                guard let apiKey = self.getOpenAIAPIKey() else {
+                    throw TachikomaError.authenticationFailed
+                }
+
+                return OpenAIModel(apiKey: apiKey, modelName: modelName)
+            }
+        }
+    }
+
+    nonisolated private func getOpenAIAPIKey() -> String? {
+        // Check environment variable
+        if let apiKey = ProcessInfo.processInfo.environment["OPENAI_API_KEY"] {
+            return apiKey
+        }
+
+        // Check standard configuration directory
+        let configPath = FileManager.default.homeDirectoryForCurrentUser
+            .appendingPathComponent(".tachikoma")
+            .appendingPathComponent("credentials")
+
+        if let credentials = try? String(contentsOf: configPath) {
+            for line in credentials.components(separatedBy: .newlines) {
+                let trimmed = line.trimmingCharacters(in: .whitespaces)
+                if trimmed.hasPrefix("OPENAI_API_KEY=") {
+                    return String(trimmed.dropFirst("OPENAI_API_KEY=".count))
+                }
+            }
+        }
+
+        return nil
+    }
+
+    private func registerAnthropicModels() {
+        // Map of model names to their actual IDs
+        let modelMappings: [String: String] = [
+            // Claude 4 series (Latest - May 2025)
+            "claude-opus-4-20250514": "claude-opus-4-20250514",
+            "claude-opus-4-20250514-thinking": "claude-opus-4-20250514-thinking",
+            "claude-sonnet-4-20250514": "claude-sonnet-4-20250514",
+            "claude-sonnet-4-20250514-thinking": "claude-sonnet-4-20250514-thinking",
+
+            // Claude 3.7 series (February 2025)
+            "claude-3-7-sonnet": "claude-3-7-sonnet",
+
+            // Claude 3.5 series (Still available)
+            "claude-3-5-haiku": "claude-3-5-haiku",
+            "claude-3-5-sonnet": "claude-3-5-sonnet",
+            "claude-3-5-opus": "claude-3-5-opus",
+        ]
+
+        for (alias, actualModelId) in modelMappings {
+            self.register(modelName: alias) {
+                guard let apiKey = self.getAnthropicAPIKey() else {
+                    throw TachikomaError.authenticationFailed
+                }
+
+                return AnthropicModel(apiKey: apiKey, modelName: actualModelId)
+            }
+        }
+    }
+
+    nonisolated private func getAnthropicAPIKey() -> String? {
+        // Check environment variable
+        if let apiKey = ProcessInfo.processInfo.environment["ANTHROPIC_API_KEY"] {
+            return apiKey
+        }
+
+        // Check standard configuration directory
+        let configPath = FileManager.default.homeDirectoryForCurrentUser
+            .appendingPathComponent(".tachikoma")
+            .appendingPathComponent("credentials")
+
+        if let credentials = try? String(contentsOf: configPath) {
+            for line in credentials.components(separatedBy: .newlines) {
+                let trimmed = line.trimmingCharacters(in: .whitespaces)
+                if trimmed.hasPrefix("ANTHROPIC_API_KEY=") {
+                    return String(trimmed.dropFirst("ANTHROPIC_API_KEY=".count))
+                }
+            }
+        }
+
+        return nil
+    }
+
+    private func registerGrokModels() {
+        let models = [
+            // Grok 4 series
+            "grok-4",
+            "grok-4-0709",
+            "grok-4-latest",
+
+            // Grok 3 series
+            "grok-3",
+            "grok-3-mini",
+            "grok-3-fast",
+            "grok-3-mini-fast",
+
+            // Grok 2 series
+            "grok-2-1212",
+            "grok-2-vision-1212",
+            "grok-2-image-1212",
+
+            // Beta models
+            "grok-beta",
+            "grok-vision-beta",
+        ]
+
+        for modelName in models {
+            self.register(modelName: modelName) {
+                guard let apiKey = self.getGrokAPIKey() else {
+                    throw TachikomaError.authenticationFailed
+                }
+
+                return GrokModel(apiKey: apiKey, modelName: modelName)
+            }
+        }
+    }
+
+    nonisolated private func getGrokAPIKey() -> String? {
+        // Check environment variables (both variants)
+        if let apiKey = ProcessInfo.processInfo.environment["X_AI_API_KEY"] {
+            return apiKey
+        }
+        if let apiKey = ProcessInfo.processInfo.environment["XAI_API_KEY"] {
+            return apiKey
+        }
+
+        // Check standard configuration directory
+        let configPath = FileManager.default.homeDirectoryForCurrentUser
+            .appendingPathComponent(".tachikoma")
+            .appendingPathComponent("credentials")
+
+        if let credentials = try? String(contentsOf: configPath) {
+            for line in credentials.components(separatedBy: .newlines) {
+                let trimmed = line.trimmingCharacters(in: .whitespaces)
+                if trimmed.hasPrefix("X_AI_API_KEY=") {
+                    return String(trimmed.dropFirst("X_AI_API_KEY=".count))
+                }
+                if trimmed.hasPrefix("XAI_API_KEY=") {
+                    return String(trimmed.dropFirst("XAI_API_KEY=".count))
+                }
+            }
+        }
+
+        return nil
+    }
+
+    private func registerOllamaModels() {
+        // Common Ollama models
+        let models = [
+            // Language models with tool support (recommended for agent tasks)
+            "llama3.3",
+            "llama3.3:latest",
+            "llama3.2",
+            "llama3.2:latest",
+
+            // Vision models (NOTE: These do NOT support tool calling)
+            "llava:latest",
+            "llava",
+            "bakllava:latest",
+            "bakllava",
+            "llama3.2-vision:11b",
+            "llama3.2-vision:90b",
+            "qwen2.5vl:7b",
+            "qwen2.5vl:32b",
+
+            // Other language models (tool support varies)
+            "llama2",
+            "llama2:latest",
+            "llama4",
+            "llama4:latest",
+            "codellama",
+            "codellama:latest",
+            "mistral",
+            "mistral:latest",
+            "mixtral",
+            "mixtral:latest",
+            "neural-chat",
+            "neural-chat:latest",
+            "gemma",
+            "gemma:latest",
+            "devstral",
+            "devstral:latest",
+            "deepseek-r1:8b",
+            "deepseek-r1:671b",
+        ]
+
+        // Get base URL from environment or default
+        let baseURLString = ProcessInfo.processInfo.environment["TACHIKOMA_OLLAMA_BASE_URL"] ?? "http://localhost:11434"
+        guard let baseURL = URL(string: baseURLString) else { return }
+
+        for modelName in models {
+            self.register(modelName: modelName) {
+                OllamaModel(modelName: modelName, baseURL: baseURL)
+            }
+        }
+    }
+
+    // MARK: - Custom Provider Support
+
+    /// Create a model instance for a custom provider
+    /// - Parameters:
+    ///   - providerId: The custom provider ID
+    ///   - modelPath: The model path within the provider
+    /// - Returns: A model instance
+    /// - Throws: TachikomaError if provider not found or configuration invalid
+    private func createCustomProviderModel(providerId: String, modelPath: String) throws -> any ModelInterface {
+        // For now, return a basic implementation
+        // This can be extended with a configuration system later
+        throw TachikomaError.modelNotFound("Custom providers not yet implemented")
+    }
+}
+
+// MARK: - Model Provider Configuration
+
+/// Configuration for model providers
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum ProviderConfiguration {
+    /// OpenAI configuration
+    public struct OpenAI: Sendable {
+        public let apiKey: String
+        public let organizationId: String?
+        public let baseURL: URL?
+
+        public init(
+            apiKey: String,
+            organizationId: String? = nil,
+            baseURL: URL? = nil)
+        {
+            self.apiKey = apiKey
+            self.organizationId = organizationId
+            self.baseURL = baseURL
+        }
+    }
+
+    /// Anthropic configuration
+    public struct Anthropic: Sendable {
+        public let apiKey: String
+        public let baseURL: URL?
+
+        public init(
+            apiKey: String,
+            baseURL: URL? = nil)
+        {
+            self.apiKey = apiKey
+            self.baseURL = baseURL
+        }
+    }
+
+    /// Ollama configuration
+    public struct Ollama: Sendable {
+        public let baseURL: URL
+
+        public init(baseURL: URL = URL(string: "http://localhost:11434")!) {
+            self.baseURL = baseURL
+        }
+    }
+
+    /// Grok/xAI configuration
+    public struct Grok: Sendable {
+        public let apiKey: String
+        public let baseURL: URL?
+
+        public init(
+            apiKey: String,
+            baseURL: URL? = nil)
+        {
+            self.apiKey = apiKey
+            self.baseURL = baseURL
+        }
+    }
+}
+
+// MARK: - Model Provider Extensions
+
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+extension ModelProvider {
+    /// Configure OpenAI models with specific settings
+    public func configureOpenAI(_ config: ProviderConfiguration.OpenAI) {
+        let models = [
+            // GPT-4o series
+            "gpt-4o",
+            "gpt-4o-mini",
+
+            // GPT-4.1 series
+            "gpt-4.1",
+            "gpt-4.1-mini",
+
+            // o3 series (Responses API only)
+            "o3",
+            "o3-mini",
+            "o3-pro",
+
+            // o4 series (Responses API only)
+            "o4-mini",
+        ]
+
+        for modelName in models {
+            self.register(modelName: modelName) {
+                OpenAIModel(
+                    apiKey: config.apiKey,
+                    baseURL: config.baseURL ?? URL(string: "https://api.openai.com/v1")!,
+                    organizationId: config.organizationId,
+                    modelName: modelName)
+            }
+        }
+    }
+
+    /// Configure Anthropic models with specific settings
+    public func configureAnthropic(_ config: ProviderConfiguration.Anthropic) {
+        // Map of model names to their actual IDs
+        let modelMappings: [String: String] = [
+            // Claude 4 series (Latest - May 2025)
+            "claude-opus-4-20250514": "claude-opus-4-20250514",
+            "claude-opus-4-20250514-thinking": "claude-opus-4-20250514-thinking",
+            "claude-sonnet-4-20250514": "claude-sonnet-4-20250514",
+            "claude-sonnet-4-20250514-thinking": "claude-sonnet-4-20250514-thinking",
+
+            // Claude 3.7 series (February 2025)
+            "claude-3-7-sonnet": "claude-3-7-sonnet",
+
+            // Claude 3.5 series (Still available)
+            "claude-3-5-haiku": "claude-3-5-haiku",
+            "claude-3-5-sonnet": "claude-3-5-sonnet",
+            "claude-3-5-opus": "claude-3-5-opus",
+        ]
+
+        for (alias, actualModelId) in modelMappings {
+            self.register(modelName: alias) {
+                AnthropicModel(
+                    apiKey: config.apiKey,
+                    baseURL: config.baseURL ?? URL(string: "https://api.anthropic.com/v1")!,
+                    modelName: actualModelId)
+            }
+        }
+    }
+
+    /// Configure Ollama models with specific settings
+    public func configureOllama(_ config: ProviderConfiguration.Ollama) {
+        let models = [
+            // Vision models
+            "llava:latest",
+            "llava",
+            "bakllava:latest",
+            "bakllava",
+            "llama3.2-vision:11b",
+            "llama3.2-vision:90b",
+            "qwen2.5vl:7b",
+            "qwen2.5vl:32b",
+
+            // Language models
+            "llama2",
+            "llama2:latest",
+            "llama3.2",
+            "llama3.2:latest",
+            "llama3.3",
+            "llama3.3:latest",
+            "llama4",
+            "llama4:latest",
+            "codellama",
+            "codellama:latest",
+            "mistral",
+            "mistral:latest",
+            "mixtral",
+            "mixtral:latest",
+            "neural-chat",
+            "neural-chat:latest",
+            "gemma",
+            "gemma:latest",
+            "devstral",
+            "devstral:latest",
+            "deepseek-r1:8b",
+            "deepseek-r1:671b",
+        ]
+
+        for modelName in models {
+            self.register(modelName: modelName) {
+                OllamaModel(modelName: modelName, baseURL: config.baseURL)
+            }
+        }
+    }
+
+    /// Configure Grok models with specific settings
+    public func configureGrok(_ config: ProviderConfiguration.Grok) {
+        let models = [
+            // Grok 4 series
+            "grok-4",
+            "grok-4-0709",
+            "grok-4-latest",
+
+            // Grok 3 series
+            "grok-3",
+            "grok-3-mini",
+            "grok-3-fast",
+            "grok-3-mini-fast",
+
+            // Grok 2 series
+            "grok-2-1212",
+            "grok-2-vision-1212",
+            "grok-2-image-1212",
+
+            // Beta models
+            "grok-beta",
+            "grok-vision-beta",
+        ]
+
+        for modelName in models {
+            self.register(modelName: modelName) {
+                GrokModel(
+                    apiKey: config.apiKey,
+                    modelName: modelName,
+                    baseURL: config.baseURL ?? URL(string: "https://api.x.ai/v1")!)
+            }
+        }
+    }
+
+    /// Quick setup with API key from environment
+    public func setupFromEnvironment() async throws {
+        if let apiKey = ProcessInfo.processInfo.environment["OPENAI_API_KEY"] {
+            self.configureOpenAI(ProviderConfiguration.OpenAI(apiKey: apiKey))
+        }
+
+        if let apiKey = ProcessInfo.processInfo.environment["ANTHROPIC_API_KEY"] {
+            self.configureAnthropic(ProviderConfiguration.Anthropic(apiKey: apiKey))
+        }
+
+        // Configure Ollama (no API key needed)
+        let ollamaBaseURL = ProcessInfo.processInfo.environment["TACHIKOMA_OLLAMA_BASE_URL"] ?? "http://localhost:11434"
+        if let baseURL = URL(string: ollamaBaseURL) {
+            self.configureOllama(ProviderConfiguration.Ollama(baseURL: baseURL))
+        }
+
+        // Configure Grok with various API key options
+        if let apiKey = ProcessInfo.processInfo.environment["X_AI_API_KEY"] ??
+            ProcessInfo.processInfo.environment["XAI_API_KEY"]
+        {
+            self.configureGrok(ProviderConfiguration.Grok(apiKey: apiKey))
+        }
+    }
+}
\ No newline at end of file
diff --git a/Sources/Core/StreamingTypes.swift b/Sources/Core/StreamingTypes.swift
new file mode 100644
index 0000000..66202f4
--- /dev/null
+++ b/Sources/Core/StreamingTypes.swift
@@ -0,0 +1,381 @@
+import Foundation
+
+// MARK: - Streaming Event Types
+
+/// Base protocol for all streaming events
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public protocol StreamingEvent: Codable, Sendable {
+    var type: StreamEventType { get }
+}
+
+/// Types of streaming events
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum StreamEventType: String, Codable, Sendable {
+    case textDelta = "text_delta"
+    case responseStarted = "response_started"
+    case responseCompleted = "response_completed"
+    case toolCallDelta = "tool_call_delta"
+    case toolCallCompleted = "tool_call_completed"
+    case functionCallArgumentsDelta = "function_call_arguments_delta"
+    case error
+    case unknown
+    case reasoningSummaryDelta = "reasoning_summary_delta"
+    case reasoningSummaryCompleted = "reasoning_summary_completed"
+}
+
+/// Main streaming event enum that encompasses all event types
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum StreamEvent: Codable, Sendable {
+    case textDelta(StreamTextDelta)
+    case responseStarted(StreamResponseStarted)
+    case responseCompleted(StreamResponseCompleted)
+    case toolCallDelta(StreamToolCallDelta)
+    case toolCallCompleted(StreamToolCallCompleted)
+    case functionCallArgumentsDelta(StreamFunctionCallArgumentsDelta)
+    case error(StreamError)
+    case unknown(StreamUnknown)
+    case reasoningSummaryDelta(StreamReasoningSummaryDelta)
+    case reasoningSummaryCompleted(StreamReasoningSummaryCompleted)
+
+    // Custom coding for the enum
+    enum CodingKeys: String, CodingKey {
+        case type, data
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let type = try container.decode(StreamEventType.self, forKey: .type)
+
+        switch type {
+        case .textDelta:
+            let data = try container.decode(StreamTextDelta.self, forKey: .data)
+            self = .textDelta(data)
+        case .responseStarted:
+            let data = try container.decode(StreamResponseStarted.self, forKey: .data)
+            self = .responseStarted(data)
+        case .responseCompleted:
+            let data = try container.decode(StreamResponseCompleted.self, forKey: .data)
+            self = .responseCompleted(data)
+        case .toolCallDelta:
+            let data = try container.decode(StreamToolCallDelta.self, forKey: .data)
+            self = .toolCallDelta(data)
+        case .toolCallCompleted:
+            let data = try container.decode(StreamToolCallCompleted.self, forKey: .data)
+            self = .toolCallCompleted(data)
+        case .functionCallArgumentsDelta:
+            let data = try container.decode(StreamFunctionCallArgumentsDelta.self, forKey: .data)
+            self = .functionCallArgumentsDelta(data)
+        case .error:
+            let data = try container.decode(StreamError.self, forKey: .data)
+            self = .error(data)
+        case .unknown:
+            let data = try container.decode(StreamUnknown.self, forKey: .data)
+            self = .unknown(data)
+        case .reasoningSummaryDelta:
+            let data = try container.decode(StreamReasoningSummaryDelta.self, forKey: .data)
+            self = .reasoningSummaryDelta(data)
+        case .reasoningSummaryCompleted:
+            let data = try container.decode(StreamReasoningSummaryCompleted.self, forKey: .data)
+            self = .reasoningSummaryCompleted(data)
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+
+        switch self {
+        case let .textDelta(data):
+            try container.encode(StreamEventType.textDelta, forKey: .type)
+            try container.encode(data, forKey: .data)
+        case let .responseStarted(data):
+            try container.encode(StreamEventType.responseStarted, forKey: .type)
+            try container.encode(data, forKey: .data)
+        case let .responseCompleted(data):
+            try container.encode(StreamEventType.responseCompleted, forKey: .type)
+            try container.encode(data, forKey: .data)
+        case let .toolCallDelta(data):
+            try container.encode(StreamEventType.toolCallDelta, forKey: .type)
+            try container.encode(data, forKey: .data)
+        case let .toolCallCompleted(data):
+            try container.encode(StreamEventType.toolCallCompleted, forKey: .type)
+            try container.encode(data, forKey: .data)
+        case let .functionCallArgumentsDelta(data):
+            try container.encode(StreamEventType.functionCallArgumentsDelta, forKey: .type)
+            try container.encode(data, forKey: .data)
+        case let .error(data):
+            try container.encode(StreamEventType.error, forKey: .type)
+            try container.encode(data, forKey: .data)
+        case let .unknown(data):
+            try container.encode(StreamEventType.unknown, forKey: .type)
+            try container.encode(data, forKey: .data)
+        case let .reasoningSummaryDelta(data):
+            try container.encode(StreamEventType.reasoningSummaryDelta, forKey: .type)
+            try container.encode(data, forKey: .data)
+        case let .reasoningSummaryCompleted(data):
+            try container.encode(StreamEventType.reasoningSummaryCompleted, forKey: .type)
+            try container.encode(data, forKey: .data)
+        }
+    }
+}
+
+// MARK: - Concrete Streaming Event Types
+
+/// Text delta event containing incremental text output
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamTextDelta: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.textDelta
+    public let delta: String
+    public let index: Int?
+
+    public init(delta: String, index: Int? = nil) {
+        self.delta = delta
+        self.index = index
+    }
+}
+
+/// Response started event
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamResponseStarted: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.responseStarted
+    public let id: String
+    public let model: String?
+    public let systemFingerprint: String?
+
+    public init(id: String, model: String? = nil, systemFingerprint: String? = nil) {
+        self.id = id
+        self.model = model
+        self.systemFingerprint = systemFingerprint
+    }
+}
+
+/// Response completed event with final metadata
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamResponseCompleted: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.responseCompleted
+    public let id: String
+    public let usage: Usage?
+    public let finishReason: FinishReason?
+
+    public init(id: String, usage: Usage? = nil, finishReason: FinishReason? = nil) {
+        self.id = id
+        self.usage = usage
+        self.finishReason = finishReason
+    }
+}
+
+/// Tool call delta event for incremental tool call information
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamToolCallDelta: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.toolCallDelta
+    public let id: String
+    public let index: Int
+    public let function: FunctionCallDelta
+
+    public init(id: String, index: Int, function: FunctionCallDelta) {
+        self.id = id
+        self.index = index
+        self.function = function
+    }
+}
+
+/// Tool call completed event
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamToolCallCompleted: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.toolCallCompleted
+    public let id: String
+    public let function: FunctionCall
+
+    public init(id: String, function: FunctionCall) {
+        self.id = id
+        self.function = function
+    }
+}
+
+/// Function call arguments delta event for incremental function call argument information
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamFunctionCallArgumentsDelta: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.functionCallArgumentsDelta
+    public let id: String
+    public let arguments: String
+
+    public init(id: String, arguments: String) {
+        self.id = id
+        self.arguments = arguments
+    }
+}
+
+/// Error event for stream errors
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamError: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.error
+    public let error: ErrorDetail
+
+    public init(error: ErrorDetail) {
+        self.error = error
+    }
+}
+
+/// Unknown event for forward compatibility
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamUnknown: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.unknown
+    public let eventType: String
+    public let rawJSON: [UInt8]
+
+    public init(eventType: String, rawJSON: [UInt8]) {
+        self.eventType = eventType
+        self.rawJSON = rawJSON
+    }
+
+    /// Get the raw data as a dictionary if possible
+    public func getRawData() throws -> [String: Any]? {
+        let data = Data(self.rawJSON)
+        return try JSONSerialization.jsonObject(with: data) as? [String: Any]
+    }
+
+    /// Get the raw data as a pretty-printed JSON string
+    public func getRawJSONString() -> String? {
+        let data = Data(self.rawJSON)
+        if let json = try? JSONSerialization.jsonObject(with: data),
+           let prettyData = try? JSONSerialization.data(withJSONObject: json, options: .prettyPrinted)
+        {
+            return String(data: prettyData, encoding: .utf8)
+        }
+        return String(data: data, encoding: .utf8)
+    }
+}
+
+/// Reasoning summary delta event for o3 models
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamReasoningSummaryDelta: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.reasoningSummaryDelta
+    public let delta: String
+    public let index: Int?
+
+    public init(delta: String, index: Int? = nil) {
+        self.delta = delta
+        self.index = index
+    }
+}
+
+/// Reasoning summary completed event for o3 models
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct StreamReasoningSummaryCompleted: StreamingEvent, Codable, Sendable {
+    public var type = StreamEventType.reasoningSummaryCompleted
+    public let summary: String
+    public let reasoningTokens: Int?
+
+    public init(summary: String, reasoningTokens: Int? = nil) {
+        self.summary = summary
+        self.reasoningTokens = reasoningTokens
+    }
+}
+
+// MARK: - Supporting Types
+
+/// Function call delta for incremental function information
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct FunctionCallDelta: Codable, Sendable {
+    public let name: String?
+    public let arguments: String?
+
+    public init(name: String? = nil, arguments: String? = nil) {
+        self.name = name
+        self.arguments = arguments
+    }
+}
+
+/// Token usage information
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct Usage: Codable, Sendable {
+    public let promptTokens: Int
+    public let completionTokens: Int
+    public let totalTokens: Int
+    public let promptTokensDetails: TokenDetails?
+    public let completionTokensDetails: TokenDetails?
+
+    public init(
+        promptTokens: Int,
+        completionTokens: Int,
+        totalTokens: Int,
+        promptTokensDetails: TokenDetails? = nil,
+        completionTokensDetails: TokenDetails? = nil)
+    {
+        self.promptTokens = promptTokens
+        self.completionTokens = completionTokens
+        self.totalTokens = totalTokens
+        self.promptTokensDetails = promptTokensDetails
+        self.completionTokensDetails = completionTokensDetails
+    }
+}
+
+/// Detailed token usage breakdown
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct TokenDetails: Codable, Sendable {
+    public let cachedTokens: Int?
+    public let audioTokens: Int?
+    public let reasoningTokens: Int?
+
+    public init(cachedTokens: Int? = nil, audioTokens: Int? = nil, reasoningTokens: Int? = nil) {
+        self.cachedTokens = cachedTokens
+        self.audioTokens = audioTokens
+        self.reasoningTokens = reasoningTokens
+    }
+}
+
+/// Reason why the response finished
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum FinishReason: String, Codable, Sendable {
+    case stop
+    case length
+    case toolCalls = "tool_calls"
+    case contentFilter = "content_filter"
+    case functionCall = "function_call"
+}
+
+/// Error detail information
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct ErrorDetail: Codable, Sendable {
+    public let message: String
+    public let type: String?
+    public let code: String?
+    public let param: String?
+
+    public init(message: String, type: String? = nil, code: String? = nil, param: String? = nil) {
+        self.message = message
+        self.type = type
+        self.code = code
+        self.param = param
+    }
+}
+
+// MARK: - Stream Event Extensions
+
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+extension StreamEvent {
+    /// Check if this is a final event
+    public var isFinal: Bool {
+        switch self {
+        case .responseCompleted, .error, .reasoningSummaryCompleted:
+            true
+        default:
+            false
+        }
+    }
+
+    /// Extract any text content from the event
+    public var textContent: String? {
+        switch self {
+        case let .textDelta(delta):
+            delta.delta
+        case let .reasoningSummaryDelta(delta):
+            delta.delta
+        case let .reasoningSummaryCompleted(completed):
+            completed.summary
+        case let .error(error):
+            error.error.message
+        default:
+            nil
+        }
+    }
+}
\ No newline at end of file
diff --git a/Sources/Core/TachikomaError.swift b/Sources/Core/TachikomaError.swift
new file mode 100644
index 0000000..871d9d2
--- /dev/null
+++ b/Sources/Core/TachikomaError.swift
@@ -0,0 +1,202 @@
+@_exported import Foundation
+
+// MARK: - Tachikoma Error Types
+
+/// Main error type for the Tachikoma library
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum TachikomaError: Error, LocalizedError, Sendable {
+    case modelNotFound(String)
+    case authenticationFailed
+    case invalidConfiguration(String)
+    case networkError(underlying: any Error)
+    case decodingError(underlying: any Error)
+    case invalidRequest(String)
+    case apiError(message: String, code: String? = nil)
+    case timeout
+    case rateLimited
+    case insufficientQuota
+    case modelOverloaded
+    case contextLengthExceeded
+    case contentFiltered
+    case invalidToolCall(String)
+    case streamingError(String)
+    case configurationError(String)
+
+    public var errorDescription: String? {
+        switch self {
+        case let .modelNotFound(model):
+            "Model not found: \(model)"
+        case .authenticationFailed:
+            "Authentication failed - check your API key"
+        case let .invalidConfiguration(message):
+            "Invalid configuration: \(message)"
+        case let .networkError(underlying):
+            "Network error: \(underlying.localizedDescription)"
+        case let .decodingError(underlying):
+            "Failed to decode response: \(underlying.localizedDescription)"
+        case let .invalidRequest(message):
+            "Invalid request: \(message)"
+        case let .apiError(message, code):
+            if let code {
+                "API error (\(code)): \(message)"
+            } else {
+                "API error: \(message)"
+            }
+        case .timeout:
+            "Request timed out"
+        case .rateLimited:
+            "Rate limited - please slow down requests"
+        case .insufficientQuota:
+            "Insufficient quota - check your billing"
+        case .modelOverloaded:
+            "Model is currently overloaded - try again later"
+        case .contextLengthExceeded:
+            "Context length exceeded - reduce input size"
+        case .contentFiltered:
+            "Content was filtered by safety systems"
+        case let .invalidToolCall(message):
+            "Invalid tool call: \(message)"
+        case let .streamingError(message):
+            "Streaming error: \(message)"
+        case let .configurationError(message):
+            "Configuration error: \(message)"
+        }
+    }
+
+    public var recoverySuggestion: String? {
+        switch self {
+        case .modelNotFound:
+            "Check available models with listModels() or verify the model name is correct"
+        case .authenticationFailed:
+            "Verify your API key is set correctly in environment variables or credentials file"
+        case .rateLimited:
+            "Wait a moment before making another request"
+        case .insufficientQuota:
+            "Check your billing settings and account quota"
+        case .modelOverloaded:
+            "Try using a different model or retry after a delay"
+        case .contextLengthExceeded:
+            "Reduce the length of your input messages or use a model with larger context"
+        case .contentFiltered:
+            "Modify your input to comply with content policies"
+        case .timeout:
+            "Check your network connection and try again"
+        default:
+            nil
+        }
+    }
+
+    /// Check if this error indicates a temporary condition that might resolve with retry
+    public var isRetryable: Bool {
+        switch self {
+        case .rateLimited, .modelOverloaded, .timeout, .networkError:
+            true
+        default:
+            false
+        }
+    }
+
+    /// Check if this error indicates an authentication issue
+    public var isAuthenticationError: Bool {
+        switch self {
+        case .authenticationFailed, .insufficientQuota:
+            true
+        default:
+            false
+        }
+    }
+
+    /// Check if this error indicates a client-side issue
+    public var isClientError: Bool {
+        switch self {
+        case .invalidRequest, .invalidConfiguration, .contextLengthExceeded, .contentFiltered, .invalidToolCall:
+            true
+        default:
+            false
+        }
+    }
+}
+
+// MARK: - Model Request/Response Errors
+
+/// Specific errors for model requests and responses
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum ModelError: Error, LocalizedError, Sendable {
+    case invalidInput(String)
+    case missingRequiredParameter(String)
+    case unsupportedParameter(String)
+    case invalidParameterValue(String, value: String)
+    case responseTooLarge
+    case emptyResponse
+    case malformedResponse(String)
+
+    public var errorDescription: String? {
+        switch self {
+        case let .invalidInput(message):
+            "Invalid input: \(message)"
+        case let .missingRequiredParameter(param):
+            "Missing required parameter: \(param)"
+        case let .unsupportedParameter(param):
+            "Unsupported parameter: \(param)"
+        case let .invalidParameterValue(param, value):
+            "Invalid value for parameter '\(param)': \(value)"
+        case .responseTooLarge:
+            "Response exceeds maximum size limit"
+        case .emptyResponse:
+            "Received empty response from API"
+        case let .malformedResponse(message):
+            "Malformed response: \(message)"
+        }
+    }
+}
+
+// MARK: - Streaming Errors
+
+/// Errors specific to streaming operations
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum StreamingError: Error, LocalizedError, Sendable {
+    case streamClosed
+    case invalidEventFormat(String)
+    case bufferOverflow
+    case connectionLost
+
+    public var errorDescription: String? {
+        switch self {
+        case .streamClosed:
+            "Stream was closed unexpectedly"
+        case let .invalidEventFormat(format):
+            "Invalid event format: \(format)"
+        case .bufferOverflow:
+            "Stream buffer overflow"
+        case .connectionLost:
+            "Connection to stream was lost"
+        }
+    }
+}
+
+// MARK: - Tool Execution Errors
+
+/// Errors for tool execution
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum ToolExecutionError: Error, LocalizedError, Sendable {
+    case toolNotFound(String)
+    case invalidArguments(String)
+    case executionFailed(String)
+    case timeout
+    case missingContext
+
+    public var errorDescription: String? {
+        switch self {
+        case let .toolNotFound(name):
+            "Tool not found: \(name)"
+        case let .invalidArguments(message):
+            "Invalid tool arguments: \(message)"
+        case let .executionFailed(message):
+            "Tool execution failed: \(message)"
+        case .timeout:
+            "Tool execution timed out"
+        case .missingContext:
+            "Required context is missing for tool execution"
+        }
+    }
+}
\ No newline at end of file
diff --git a/Sources/Core/ToolDefinitions.swift b/Sources/Core/ToolDefinitions.swift
new file mode 100644
index 0000000..3fd2969
--- /dev/null
+++ b/Sources/Core/ToolDefinitions.swift
@@ -0,0 +1,597 @@
+import Foundation
+
+// MARK: - Tool Definition
+
+/// A tool that can be used by an agent to perform actions
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct Tool<Context> {
+    /// Unique name of the tool
+    public let name: String
+
+    /// Description of what the tool does
+    public let description: String
+
+    /// Parameters the tool accepts
+    public let parameters: ToolParameters
+
+    /// Whether to use strict parameter validation
+    public let strict: Bool
+
+    /// The function to execute when the tool is called
+    public let execute: (ToolInput, Context) async throws -> ToolOutput
+
+    public init(
+        name: String,
+        description: String,
+        parameters: ToolParameters,
+        strict: Bool = true,
+        execute: @escaping (ToolInput, Context) async throws -> ToolOutput)
+    {
+        self.name = name
+        self.description = description
+        self.parameters = parameters
+        self.strict = strict
+        self.execute = execute
+    }
+
+    /// Convert to a tool definition for the model
+    public func toToolDefinition() -> ToolDefinition {
+        ToolDefinition(
+            type: .function,
+            function: FunctionDefinition(
+                name: self.name,
+                description: self.description,
+                parameters: self.parameters,
+                strict: self.strict))
+    }
+}
+
+// MARK: - Tool Definition Types
+
+/// Definition of a tool that can be sent to a model
+public struct ToolDefinition: Codable, Sendable {
+    public let type: ToolType
+    public let function: FunctionDefinition
+
+    public init(type: ToolType = .function, function: FunctionDefinition) {
+        self.type = type
+        self.function = function
+    }
+}
+
+/// Type of tool
+public enum ToolType: String, Codable, Sendable {
+    case function
+}
+
+/// Function definition for a tool
+public struct FunctionDefinition: Codable, Sendable {
+    public let name: String
+    public let description: String
+    public let parameters: ToolParameters
+    public let strict: Bool?
+
+    public init(
+        name: String,
+        description: String,
+        parameters: ToolParameters,
+        strict: Bool? = nil)
+    {
+        self.name = name
+        self.description = description
+        self.parameters = parameters
+        self.strict = strict
+    }
+}
+
+// MARK: - Tool Parameters
+
+/// Parameters schema for a tool
+public struct ToolParameters: Codable, Sendable {
+    public let type: String
+    public let properties: [String: ParameterSchema]
+    public let required: [String]
+    public let additionalProperties: Bool
+
+    public init(
+        type: String = "object",
+        properties: [String: ParameterSchema] = [:],
+        required: [String] = [],
+        additionalProperties: Bool = false)
+    {
+        self.type = type
+        self.properties = properties
+        self.required = required
+        self.additionalProperties = additionalProperties
+    }
+
+    /// Create parameters from a dictionary of property definitions
+    public static func object(
+        properties: [String: ParameterSchema],
+        required: [String] = []) -> ToolParameters
+    {
+        ToolParameters(
+            type: "object",
+            properties: properties,
+            required: required,
+            additionalProperties: false)
+    }
+}
+
+/// Schema for a single parameter
+public struct ParameterSchema: Codable, Sendable {
+    public let type: ParameterType
+    public let description: String?
+    public let enumValues: [String]?
+    public let items: Box<ParameterSchema>?
+    public let properties: [String: ParameterSchema]?
+    public let minimum: Double?
+    public let maximum: Double?
+    public let pattern: String?
+
+    public init(
+        type: ParameterType,
+        description: String? = nil,
+        enumValues: [String]? = nil,
+        items: ParameterSchema? = nil,
+        properties: [String: ParameterSchema]? = nil,
+        minimum: Double? = nil,
+        maximum: Double? = nil,
+        pattern: String? = nil)
+    {
+        self.type = type
+        self.description = description
+        self.enumValues = enumValues
+        self.items = items.map(Box.init)
+        self.properties = properties
+        self.minimum = minimum
+        self.maximum = maximum
+        self.pattern = pattern
+    }
+
+    // Convenience initializers
+    public static func string(description: String? = nil, pattern: String? = nil) -> ParameterSchema {
+        ParameterSchema(type: .string, description: description, pattern: pattern)
+    }
+
+    public static func number(
+        description: String? = nil,
+        minimum: Double? = nil,
+        maximum: Double? = nil) -> ParameterSchema
+    {
+        ParameterSchema(type: .number, description: description, minimum: minimum, maximum: maximum)
+    }
+
+    public static func integer(
+        description: String? = nil,
+        minimum: Double? = nil,
+        maximum: Double? = nil) -> ParameterSchema
+    {
+        ParameterSchema(type: .integer, description: description, minimum: minimum, maximum: maximum)
+    }
+
+    public static func boolean(description: String? = nil) -> ParameterSchema {
+        ParameterSchema(type: .boolean, description: description)
+    }
+
+    public static func array(of items: ParameterSchema, description: String? = nil) -> ParameterSchema {
+        ParameterSchema(type: .array, description: description, items: items)
+    }
+
+    public static func object(properties: [String: ParameterSchema], description: String? = nil) -> ParameterSchema {
+        ParameterSchema(type: .object, description: description, properties: properties)
+    }
+
+    public static func enumeration(_ values: [String], description: String? = nil) -> ParameterSchema {
+        ParameterSchema(type: .string, description: description, enumValues: values)
+    }
+
+    // Custom coding keys
+    enum CodingKeys: String, CodingKey {
+        case type, description
+        case enumValues = "enum"
+        case items, properties
+        case minimum, maximum, pattern
+    }
+}
+
+/// Parameter types
+public enum ParameterType: String, Codable, Sendable {
+    case string
+    case number
+    case integer
+    case boolean
+    case array
+    case object
+    case null
+}
+
+// MARK: - Tool Input/Output
+
+/// Input provided to a tool
+public enum ToolInput {
+    case string(String)
+    case dictionary([String: Any])
+    case array([Any])
+    case null
+
+    /// Parse from a JSON string
+    public init(jsonString: String) throws {
+        // Handle empty string as empty dictionary
+        if jsonString.isEmpty {
+            self = .dictionary([:])
+            return
+        }
+
+        guard let data = jsonString.data(using: .utf8) else {
+            throw ToolError.invalidInput("Invalid JSON string")
+        }
+
+        let parsed = try JSONSerialization.jsonObject(with: data)
+
+        if let dict = parsed as? [String: Any] {
+            self = .dictionary(dict)
+        } else if let array = parsed as? [Any] {
+            self = .array(array)
+        } else if let string = parsed as? String {
+            self = .string(string)
+        } else {
+            self = .null
+        }
+    }
+
+    /// Get value for a specific key (for dictionary inputs)
+    public func value<T>(for key: String) -> T? {
+        guard case let .dictionary(dict) = self else { return nil }
+        return dict[key] as? T
+    }
+
+    /// Get the raw string value
+    public var stringValue: String? {
+        switch self {
+        case let .string(str):
+            return str
+        case .dictionary, .array:
+            if let data = try? JSONSerialization.data(withJSONObject: rawValue),
+               let str = String(data: data, encoding: .utf8)
+            {
+                return str
+            }
+            return nil
+        case .null:
+            return nil
+        }
+    }
+
+    /// Get the raw value
+    public var rawValue: Any {
+        switch self {
+        case let .string(str):
+            str
+        case let .dictionary(dict):
+            dict
+        case let .array(array):
+            array
+        case .null:
+            NSNull()
+        }
+    }
+}
+
+/// Strongly-typed output from a tool
+public enum ToolOutput: Codable, Sendable {
+    case string(String)
+    case number(Double)
+    case boolean(Bool)
+    case object([String: ToolOutput])
+    case array([ToolOutput])
+    case null
+    case error(message: String, code: String? = nil)
+
+    // MARK: - Codable Implementation
+
+    private enum CodingKeys: String, CodingKey {
+        case type, value, message, code
+    }
+
+    private enum OutputType: String, Codable {
+        case string, number, boolean, object, array, null, error
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let type = try container.decode(OutputType.self, forKey: .type)
+
+        switch type {
+        case .string:
+            let value = try container.decode(String.self, forKey: .value)
+            self = .string(value)
+        case .number:
+            let value = try container.decode(Double.self, forKey: .value)
+            self = .number(value)
+        case .boolean:
+            let value = try container.decode(Bool.self, forKey: .value)
+            self = .boolean(value)
+        case .object:
+            let value = try container.decode([String: ToolOutput].self, forKey: .value)
+            self = .object(value)
+        case .array:
+            let value = try container.decode([ToolOutput].self, forKey: .value)
+            self = .array(value)
+        case .null:
+            self = .null
+        case .error:
+            let message = try container.decode(String.self, forKey: .message)
+            let code = try container.decodeIfPresent(String.self, forKey: .code)
+            self = .error(message: message, code: code)
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+
+        switch self {
+        case let .string(value):
+            try container.encode(OutputType.string, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .number(value):
+            try container.encode(OutputType.number, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .boolean(value):
+            try container.encode(OutputType.boolean, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .object(value):
+            try container.encode(OutputType.object, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case let .array(value):
+            try container.encode(OutputType.array, forKey: .type)
+            try container.encode(value, forKey: .value)
+        case .null:
+            try container.encode(OutputType.null, forKey: .type)
+        case let .error(message, code):
+            try container.encode(OutputType.error, forKey: .type)
+            try container.encode(message, forKey: .message)
+            try container.encodeIfPresent(code, forKey: .code)
+        }
+    }
+
+    // MARK: - Conversion Methods
+
+    /// Convert to JSON string for the model
+    public func toJSONString() throws -> String {
+        switch self {
+        case let .string(str):
+            return str // Return string directly for text output
+        case let .error(message, code):
+            // Special handling for errors to match expected format
+            var errorDict: [String: ToolOutput] = ["error": .string(message)]
+            if let code {
+                errorDict["error_code"] = .string(code)
+            }
+            let data = try JSONEncoder().encode(ToolOutput.object(errorDict))
+            guard let string = String(data: data, encoding: .utf8) else {
+                throw ToolError.serializationFailed
+            }
+            return string
+        default:
+            // For all other types, encode normally
+            let encoder = JSONEncoder()
+            encoder.outputFormatting = .prettyPrinted
+            let data = try encoder.encode(self)
+            guard let string = String(data: data, encoding: .utf8) else {
+                throw ToolError.serializationFailed
+            }
+            return string
+        }
+    }
+
+    /// Convert to a dictionary representation (for compatibility)
+    public func toDictionary() -> [String: Any]? {
+        switch self {
+        case let .object(dict):
+            var result: [String: Any] = [:]
+            for (key, value) in dict {
+                if let converted = value.toAny() {
+                    result[key] = converted
+                }
+            }
+            return result
+        default:
+            return nil
+        }
+    }
+
+    /// Convert to Any (for legacy compatibility)
+    private func toAny() -> Any? {
+        switch self {
+        case let .string(value):
+            return value
+        case let .number(value):
+            return value
+        case let .boolean(value):
+            return value
+        case let .object(dict):
+            var result: [String: Any] = [:]
+            for (key, value) in dict {
+                if let converted = value.toAny() {
+                    result[key] = converted
+                }
+            }
+            return result
+        case let .array(array):
+            return array.compactMap { $0.toAny() }
+        case .null:
+            return NSNull()
+        case let .error(message, _):
+            return ["error": message]
+        }
+    }
+}
+
+// MARK: - Builder Methods
+
+extension ToolOutput {
+    /// Create a dictionary/object output using a builder pattern
+    public static func dictionary(_ builder: () -> [String: ToolOutput]) -> ToolOutput {
+        .object(builder())
+    }
+
+    /// Create a dictionary/object output from key-value pairs
+    public static func dictionary(_ pairs: (String, ToolOutput)...) -> ToolOutput {
+        var dict: [String: ToolOutput] = [:]
+        for (key, value) in pairs {
+            dict[key] = value
+        }
+        return .object(dict)
+    }
+
+    /// Create from a Swift dictionary with automatic type conversion
+    public static func from(_ dict: [String: Any]) -> ToolOutput {
+        var result: [String: ToolOutput] = [:]
+        for (key, value) in dict {
+            result[key] = self.from(value)
+        }
+        return .object(result)
+    }
+
+    /// Create from any Swift value with automatic type conversion
+    public static func from(_ value: Any) -> ToolOutput {
+        switch value {
+        case let str as String:
+            .string(str)
+        case let num as Int:
+            .number(Double(num))
+        case let num as Double:
+            .number(num)
+        case let bool as Bool:
+            .boolean(bool)
+        case let dict as [String: Any]:
+            self.from(dict)
+        case let array as [Any]:
+            .array(array.map { self.from($0) })
+        case is NSNull:
+            .null
+        default:
+            // Fallback to string representation
+            .string(String(describing: value))
+        }
+    }
+
+    /// Convenience method for success results
+    public static func success(_ message: String, metadata: (String, ToolOutput)...) -> ToolOutput {
+        var dict: [String: ToolOutput] = ["result": .string(message)]
+        for (key, value) in metadata {
+            dict[key] = value
+        }
+        return .object(dict)
+    }
+}
+
+// MARK: - Tool Errors
+
+/// Errors that can occur during tool execution
+public enum ToolError: Error, LocalizedError, Sendable {
+    case invalidInput(String)
+    case executionFailed(String)
+    case serializationFailed
+    case contextMissing
+    case toolNotFound(String)
+
+    public var errorDescription: String? {
+        switch self {
+        case let .invalidInput(message):
+            "Invalid tool input: \(message)"
+        case let .executionFailed(message):
+            "Tool execution failed: \(message)"
+        case .serializationFailed:
+            "Failed to serialize tool output"
+        case .contextMissing:
+            "Required context is missing"
+        case let .toolNotFound(name):
+            "Tool not found: \(name)"
+        }
+    }
+}
+
+// MARK: - Helper Types
+
+/// Box type for recursive data structures
+public final class Box<T: Codable & Sendable>: Codable, Sendable {
+    public let value: T
+
+    public init(_ value: T) {
+        self.value = value
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.singleValueContainer()
+        self.value = try container.decode(T.self)
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.singleValueContainer()
+        try container.encode(self.value)
+    }
+}
+
+// MARK: - Tool Builder
+
+/// Builder pattern for creating tools
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct ToolBuilder<Context> {
+    private var name: String = ""
+    private var description: String = ""
+    private var parameters: ToolParameters = .init()
+    private var strict: Bool = true
+    private var execute: ((ToolInput, Context) async throws -> ToolOutput)?
+
+    public init() {}
+
+    public func withName(_ name: String) -> ToolBuilder<Context> {
+        var builder = self
+        builder.name = name
+        return builder
+    }
+
+    public func withDescription(_ description: String) -> ToolBuilder<Context> {
+        var builder = self
+        builder.description = description
+        return builder
+    }
+
+    public func withParameters(_ parameters: ToolParameters) -> ToolBuilder<Context> {
+        var builder = self
+        builder.parameters = parameters
+        return builder
+    }
+
+    public func withStrict(_ strict: Bool) -> ToolBuilder<Context> {
+        var builder = self
+        builder.strict = strict
+        return builder
+    }
+
+    public func withExecution(_ execute: @escaping (ToolInput, Context) async throws -> ToolOutput)
+    -> ToolBuilder<Context> {
+        var builder = self
+        builder.execute = execute
+        return builder
+    }
+
+    public func build() throws -> Tool<Context> {
+        guard !self.name.isEmpty else {
+            throw ToolError.invalidInput("Tool name is required")
+        }
+
+        guard let execute else {
+            throw ToolError.invalidInput("Tool execution function is required")
+        }
+
+        return Tool(
+            name: self.name,
+            description: self.description,
+            parameters: self.parameters,
+            strict: self.strict,
+            execute: execute)
+    }
+}
\ No newline at end of file
diff --git a/Sources/Providers/Anthropic/AnthropicModel.swift b/Sources/Providers/Anthropic/AnthropicModel.swift
new file mode 100644
index 0000000..151106a
--- /dev/null
+++ b/Sources/Providers/Anthropic/AnthropicModel.swift
@@ -0,0 +1,642 @@
+import Foundation
+
+/// Anthropic model implementation conforming to ModelInterface
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public final class AnthropicModel: ModelInterface, Sendable {
+    private let apiKey: String
+    private let baseURL: URL
+    private let session: URLSession
+    private let anthropicVersion: String
+    private let modelName: String?
+    private let customHeaders: [String: String]?
+
+    public init(
+        apiKey: String,
+        baseURL: URL = URL(string: "https://api.anthropic.com/v1")!,
+        anthropicVersion: String = "2023-06-01",
+        modelName: String? = nil,
+        session: URLSession? = nil)
+    {
+        self.apiKey = apiKey
+        self.baseURL = baseURL
+        self.anthropicVersion = anthropicVersion
+        self.modelName = modelName
+        self.customHeaders = nil
+        
+        if let session {
+            self.session = session
+        } else {
+            let config = URLSessionConfiguration.default
+            config.timeoutIntervalForRequest = 120 // 2 minutes
+            config.timeoutIntervalForResource = 120
+            self.session = URLSession(configuration: config)
+        }
+    }
+    
+    /// Initialize with custom provider configuration
+    public init(
+        apiKey: String,
+        baseURL: String,
+        modelName: String? = nil,
+        headers: [String: String]? = nil,
+        anthropicVersion: String = "2023-06-01",
+        session: URLSession? = nil)
+    {
+        self.apiKey = apiKey
+        self.baseURL = URL(string: baseURL) ?? URL(string: "https://api.anthropic.com/v1")!
+        self.anthropicVersion = anthropicVersion
+        self.modelName = modelName
+        self.customHeaders = headers
+        
+        if let session {
+            self.session = session
+        } else {
+            let config = URLSessionConfiguration.default
+            config.timeoutIntervalForRequest = 120 // 2 minutes
+            config.timeoutIntervalForResource = 120
+            self.session = URLSession(configuration: config)
+        }
+    }
+
+    // MARK: - ModelInterface Implementation
+
+    public var maskedApiKey: String {
+        guard self.apiKey.count > 8 else { return "***" }
+        let start = self.apiKey.prefix(6)
+        let end = self.apiKey.suffix(2)
+        return "\(start)...\(end)"
+    }
+
+    public func getResponse(request: ModelRequest) async throws -> ModelResponse {
+        let anthropicRequest = try convertToAnthropicRequest(request, stream: false)
+        let urlRequest = try createURLRequest(endpoint: "messages", body: anthropicRequest)
+
+        let (data, response) = try await session.data(for: urlRequest)
+
+        guard let httpResponse = response as? HTTPURLResponse else {
+            throw TachikomaError.networkError(underlying: URLError(.badServerResponse))
+        }
+
+        if httpResponse.statusCode != 200 {
+            try handleErrorResponse(data: data, response: httpResponse)
+        }
+
+        do {
+            let anthropicResponse = try JSONDecoder().decode(AnthropicResponse.self, from: data)
+            return try self.convertFromAnthropicResponse(anthropicResponse)
+        } catch {
+            throw TachikomaError.decodingError(underlying: error)
+        }
+    }
+
+    public func getStreamedResponse(request: ModelRequest) async throws -> AsyncThrowingStream<StreamEvent, any Error> {
+        let anthropicRequest = try convertToAnthropicRequest(request, stream: true)
+        let urlRequest = try createURLRequest(endpoint: "messages", body: anthropicRequest)
+
+        return AsyncThrowingStream { continuation in
+            Task {
+                do {
+                    let (bytes, response) = try await session.bytes(for: urlRequest)
+
+                    guard let httpResponse = response as? HTTPURLResponse else {
+                        continuation.finish(throwing: TachikomaError.networkError(underlying: URLError(.badServerResponse)))
+                        return
+                    }
+
+                    if httpResponse.statusCode != 200 {
+                        var errorData = Data()
+                        for try await byte in bytes.prefix(1024) {
+                            errorData.append(byte)
+                        }
+                        try self.handleErrorResponse(data: errorData, response: httpResponse)
+                    }
+
+                    // Process SSE stream
+                    var currentToolCalls: [String: PartialToolCall] = [:]
+                    var responseId: String?
+                    var accumulatedText = ""
+                    var currentContentIndex = 0
+                    var pendingUsage: Usage?
+
+                    for try await line in bytes.lines {
+                        // Skip empty lines
+                        if line.isEmpty {
+                            continue
+                        }
+
+                        // Handle SSE format
+                        if line.hasPrefix("data: ") {
+                            let data = String(line.dropFirst(6))
+
+                            // Parse the event
+                            if let eventData = data.data(using: .utf8) {
+                                do {
+                                    let event = try JSONDecoder().decode(
+                                        AnthropicStreamEvent.self,
+                                        from: eventData)
+
+                                    switch event.type {
+                                    case "message_start":
+                                        if let message = event.message {
+                                            responseId = message.id
+                                            continuation.yield(.responseStarted(StreamResponseStarted(
+                                                id: message.id,
+                                                model: message.model,
+                                                systemFingerprint: nil)))
+                                        }
+
+                                    case "content_block_start":
+                                        currentContentIndex = event.index ?? 0
+                                        if let block = event.contentBlock {
+                                            if block.type == "tool_use", let id = block.id, let name = block.name {
+                                                // Start tracking this tool call
+                                                let partialCall = PartialToolCall(
+                                                    id: id,
+                                                    name: name,
+                                                    index: currentContentIndex)
+                                                currentToolCalls[id] = partialCall
+                                            }
+                                        }
+
+                                    case "content_block_delta":
+                                        if let delta = event.delta {
+                                            if let text = delta.text {
+                                                // Text delta
+                                                continuation.yield(.textDelta(StreamTextDelta(
+                                                    delta: text,
+                                                    index: currentContentIndex)))
+                                                accumulatedText += text
+                                            } else if let partialJson = delta.partialJson {
+                                                // Tool use arguments delta
+                                                // Find the tool call being updated
+                                                if let toolCall = currentToolCalls.values
+                                                    .first(where: { $0.index == currentContentIndex })
+                                                {
+                                                    toolCall.appendArguments(partialJson)
+                                                    continuation.yield(.toolCallDelta(StreamToolCallDelta(
+                                                        id: toolCall.id,
+                                                        index: toolCall.index,
+                                                        function: FunctionCallDelta(
+                                                            name: toolCall.name,
+                                                            arguments: partialJson))))
+                                                }
+                                            }
+                                        }
+
+                                    case "content_block_stop":
+                                        // Complete any tool calls at this index
+                                        for (id, toolCall) in currentToolCalls {
+                                            if toolCall.index == currentContentIndex {
+                                                if let completed = toolCall.toCompleted() {
+                                                    continuation.yield(.toolCallCompleted(
+                                                        StreamToolCallCompleted(id: id, function: completed)))
+                                                }
+                                            }
+                                        }
+
+                                    case "message_delta":
+                                        // Skip regular parsing - will handle in catch block for usage data
+                                        break
+
+                                    case "message_stop":
+                                        // Final completion - emit responseCompleted with usage if available
+                                        if let id = responseId {
+                                            continuation.yield(.responseCompleted(StreamResponseCompleted(
+                                                id: id,
+                                                usage: pendingUsage,
+                                                finishReason: .stop)))
+                                        }
+                                        continuation.finish()
+                                        return
+
+                                    case "error":
+                                        if let error = event.error {
+                                            continuation.finish(throwing: TachikomaError.apiError(
+                                                message: error.message))
+                                            return
+                                        }
+
+                                    default:
+                                        // Unknown event type, ignore
+                                        break
+                                    }
+                                } catch {
+                                    // Special handling for message_delta events with usage
+                                    if let jsonData = data.data(using: .utf8) {
+                                        do {
+                                            if let json = try JSONSerialization
+                                                .jsonObject(with: jsonData) as? [String: Any]
+                                            {
+                                                if json["type"] as? String == "message_delta" {
+                                                    if let usage = json["usage"] as? [String: Any] {
+                                                        if let outputTokens = usage["output_tokens"] as? Int {
+                                                            // Extract input tokens if available
+                                                            let inputTokens = usage["input_tokens"] as? Int ?? 0
+
+                                                            // Create Usage object
+                                                            let tokenUsage = Usage(
+                                                                promptTokens: inputTokens,
+                                                                completionTokens: outputTokens,
+                                                                totalTokens: inputTokens + outputTokens,
+                                                                promptTokensDetails: nil,
+                                                                completionTokensDetails: nil)
+
+                                                            // Store the usage for later
+                                                            pendingUsage = tokenUsage
+                                                        }
+                                                    }
+                                                }
+                                            }
+                                        } catch {
+                                            // Failed to parse JSON, ignore
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+
+                    continuation.finish()
+                } catch {
+                    continuation.finish(throwing: TachikomaError.streamingError(error.localizedDescription))
+                }
+            }
+        }
+    }
+
+    // MARK: - Private Methods
+
+    private func createURLRequest(endpoint: String, body: any Encodable) throws -> URLRequest {
+        let url = self.baseURL.appendingPathComponent(endpoint)
+        var request = URLRequest(url: url)
+        request.httpMethod = "POST"
+        request.setValue(self.apiKey, forHTTPHeaderField: "x-api-key")
+        request.setValue(self.anthropicVersion, forHTTPHeaderField: "anthropic-version")
+        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
+        
+        // Add custom headers from provider configuration
+        customHeaders?.forEach { key, value in
+            request.setValue(value, forHTTPHeaderField: key)
+        }
+
+        let encoder = JSONEncoder()
+        encoder.outputFormatting = .sortedKeys
+
+        do {
+            request.httpBody = try encoder.encode(body)
+        } catch {
+            throw TachikomaError.configurationError("Failed to encode Anthropic request: \(error.localizedDescription)")
+        }
+
+        request.timeoutInterval = 120
+
+        return request
+    }
+
+    private func convertToAnthropicRequest(_ request: ModelRequest, stream: Bool) throws -> AnthropicRequest {
+        var anthropicMessages: [AnthropicMessage] = []
+        var systemPrompt: String? = nil
+
+        // Convert messages
+        for message in request.messages {
+            switch message {
+            case let .system(_, content):
+                // Anthropic uses a separate system parameter
+                if systemPrompt == nil {
+                    systemPrompt = content
+                } else {
+                    systemPrompt = (systemPrompt ?? "") + "\n\n" + content
+                }
+
+            case let .user(_, content):
+                let anthropicMessage = try convertUserMessage(content)
+                anthropicMessages.append(anthropicMessage)
+
+            case let .assistant(_, content, status):
+                let anthropicMessage = try convertAssistantMessage(content, status: status)
+                anthropicMessages.append(anthropicMessage)
+
+            case let .tool(_, toolCallId, content):
+                // Convert tool result to user message with tool_result content block
+                let toolResultBlock = AnthropicContentBlock.toolResult(
+                    toolUseId: toolCallId,
+                    content: content)
+                anthropicMessages.append(AnthropicMessage(
+                    role: .user,
+                    content: .array([toolResultBlock])))
+
+            case let .reasoning(_, content):
+                // Treat reasoning as a system message for now
+                if systemPrompt == nil {
+                    systemPrompt = "[Reasoning] " + content
+                } else {
+                    systemPrompt = (systemPrompt ?? "") + "\n\n[Reasoning] " + content
+                }
+            }
+        }
+
+        // Convert tools
+        let tools = request.tools?.map { toolDef -> AnthropicTool in
+            AnthropicTool(
+                name: toolDef.function.name,
+                description: toolDef.function.description,
+                inputSchema: self.convertToolParameters(toolDef.function.parameters))
+        }
+
+        // Convert tool choice
+        let toolChoice = self.convertToolChoice(request.settings.toolChoice)
+
+        // Create system content with cache control
+        let systemContent: AnthropicSystemContent? = if let systemPrompt {
+            // Use array format with cache control for system prompt
+            .array([
+                AnthropicSystemBlock(
+                    type: "text",
+                    text: systemPrompt,
+                    cacheControl: AnthropicCacheControl(type: "ephemeral")),
+            ])
+        } else {
+            nil
+        }
+
+        return AnthropicRequest(
+            model: self.modelName ?? request.settings.modelName,
+            messages: anthropicMessages,
+            system: systemContent,
+            maxTokens: request.settings.maxTokens ?? 4096,
+            temperature: request.settings.temperature,
+            topP: request.settings.topP,
+            topK: request.settings.additionalParameters?.int("top_k"),
+            stream: stream,
+            stopSequences: request.settings.stopSequences,
+            tools: tools,
+            toolChoice: toolChoice,
+            metadata: request.settings.user.map { AnthropicMetadata(userId: $0) })
+    }
+
+    private func convertUserMessage(_ content: MessageContent) throws -> AnthropicMessage {
+        switch content {
+        case let .text(text):
+            return AnthropicMessage(role: .user, content: .string(text))
+
+        case let .image(imageContent):
+            var blocks: [AnthropicContentBlock] = []
+
+            if let base64 = imageContent.base64 {
+                blocks.append(.image(base64: base64, mediaType: "image/jpeg"))
+            } else if imageContent.url != nil {
+                // For URLs, we'd need to download and convert to base64
+                // For now, throw an error
+                throw TachikomaError.invalidRequest("Image URLs not supported - please provide base64 data")
+            }
+
+            return AnthropicMessage(role: .user, content: .array(blocks))
+
+        case let .multimodal(parts):
+            let blocks = try parts.compactMap { part -> AnthropicContentBlock? in
+                if let text = part.text {
+                    return .text(text)
+                } else if let image = part.imageUrl {
+                    if let base64 = image.base64 {
+                        return .image(base64: base64, mediaType: "image/jpeg")
+                    } else if image.url != nil {
+                        throw TachikomaError.invalidRequest("Image URLs not supported - please provide base64 data")
+                    }
+                }
+                return nil
+            }
+            return AnthropicMessage(role: .user, content: .array(blocks))
+
+        case .file:
+            throw TachikomaError.invalidRequest("File content not supported in Anthropic API")
+
+        case let .audio(audioContent):
+            // Claude doesn't support native audio, so we need to use the transcript
+            if let transcript = audioContent.transcript {
+                // Include metadata about the audio source
+                var text = transcript
+                if let duration = audioContent.duration {
+                    text = "[Audio transcript, duration: \(Int(duration))s] \(transcript)"
+                } else {
+                    text = "[Audio transcript] \(transcript)"
+                }
+                return AnthropicMessage(role: .user, content: .string(text))
+            } else {
+                throw TachikomaError.invalidRequest("Audio content must be transcribed before sending to Claude. Please ensure transcript is provided.")
+            }
+        }
+    }
+
+    private func convertAssistantMessage(
+        _ content: [AssistantContent],
+        status: MessageStatus) throws -> AnthropicMessage
+    {
+        var blocks: [AnthropicContentBlock] = []
+
+        for content in content {
+            switch content {
+            case let .outputText(text):
+                blocks.append(.text(text))
+
+            case let .refusal(refusal):
+                blocks.append(.text(refusal))
+
+            case let .toolCall(toolCall):
+                // Parse arguments as JSON
+                let arguments: [String: Any] = if let data = toolCall.function.arguments.data(using: .utf8),
+                                                  let json = try? JSONSerialization
+                                                      .jsonObject(with: data) as? [String: Any]
+                {
+                    json
+                } else {
+                    [:]
+                }
+
+                blocks.append(.toolUse(
+                    id: toolCall.id,
+                    name: toolCall.function.name,
+                    input: arguments))
+            }
+        }
+
+        return AnthropicMessage(role: .assistant, content: .array(blocks))
+    }
+
+    private func convertToolParameters(_ params: ToolParameters) -> AnthropicJSONSchema {
+        var properties: [String: AnthropicPropertySchema] = [:]
+
+        for (key, schema) in params.properties {
+            properties[key] = self.convertParameterSchema(schema)
+        }
+
+        return AnthropicJSONSchema(
+            type: params.type,
+            properties: properties,
+            required: params.required)
+    }
+
+    private func convertParameterSchema(_ schema: ParameterSchema) -> AnthropicPropertySchema {
+        // Handle nested items for arrays
+        let items: AnthropicPropertySchema? = if schema.type == .array, let schemaItems = schema.items {
+            self.convertParameterSchema(schemaItems.value)
+        } else {
+            nil
+        }
+
+        // Handle nested properties for objects
+        let properties: [String: AnthropicPropertySchema]?
+        if schema.type == .object, let schemaProps = schema.properties {
+            var convertedProps: [String: AnthropicPropertySchema] = [:]
+            for (key, nestedSchema) in schemaProps {
+                convertedProps[key] = self.convertParameterSchema(nestedSchema)
+            }
+            properties = convertedProps
+        } else {
+            properties = nil
+        }
+
+        return AnthropicPropertySchema(
+            type: schema.type.rawValue,
+            description: schema.description,
+            enum: schema.enumValues,
+            items: items,
+            properties: properties,
+            required: nil // ParameterSchema doesn't have required field at this level
+        )
+    }
+
+    private func convertToolChoice(_ toolChoice: ToolChoice?) -> AnthropicToolChoice? {
+        guard let toolChoice else { return nil }
+
+        switch toolChoice {
+        case .auto:
+            return .auto
+        case .none:
+            return nil // Anthropic doesn't have a "none" option
+        case .required:
+            return .any
+        case let .specific(toolName):
+            return .tool(name: toolName)
+        }
+    }
+
+    private func convertFromAnthropicResponse(_ response: AnthropicResponse) throws -> ModelResponse {
+        var content: [AssistantContent] = []
+
+        // Convert content blocks
+        for block in response.content {
+            switch block.type {
+            case "text":
+                if let text = block.text {
+                    content.append(.outputText(text))
+                }
+
+            case "tool_use":
+                if let id = block.id,
+                   let name = block.name,
+                   let input = block.input
+                {
+                    // Convert input dictionary to JSON string
+                    let arguments: String = if let data = try? JSONSerialization.data(withJSONObject: input.mapValues { $0.toAny() }),
+                                               let json = String(data: data, encoding: .utf8)
+                    {
+                        json
+                    } else {
+                        "{}"
+                    }
+
+                    content.append(.toolCall(ToolCallItem(
+                        id: id,
+                        type: .function,
+                        function: FunctionCall(
+                            name: name,
+                            arguments: arguments))))
+                }
+
+            default:
+                // Unknown content block type, ignore
+                break
+            }
+        }
+
+        let usage = Usage(
+            promptTokens: response.usage.inputTokens,
+            completionTokens: response.usage.outputTokens,
+            totalTokens: response.usage.inputTokens + response.usage.outputTokens,
+            promptTokensDetails: nil,
+            completionTokensDetails: nil)
+
+        return ModelResponse(
+            id: response.id,
+            model: response.model,
+            content: content,
+            usage: usage,
+            flagged: false,
+            finishReason: self.convertStopReason(response.stopReason))
+    }
+
+    private func convertStopReason(_ reason: String?) -> FinishReason? {
+        guard let reason else { return nil }
+
+        switch reason {
+        case "end_turn":
+            return .stop
+        case "max_tokens":
+            return .length
+        case "stop_sequence":
+            return .stop
+        case "tool_use":
+            return .toolCalls
+        default:
+            return .stop
+        }
+    }
+
+    private func handleErrorResponse(data: Data, response: HTTPURLResponse) throws {
+        if let errorResponse = try? JSONDecoder().decode(AnthropicErrorResponse.self, from: data) {
+            let message = errorResponse.error.message
+            
+            switch response.statusCode {
+            case 401:
+                throw TachikomaError.authenticationFailed
+            case 429:
+                throw TachikomaError.rateLimited
+            case 400:
+                if message.contains("credit") || message.contains("usage") {
+                    throw TachikomaError.insufficientQuota
+                } else {
+                    throw TachikomaError.invalidRequest(message)
+                }
+            case 500...599:
+                throw TachikomaError.modelOverloaded
+            default:
+                throw TachikomaError.apiError(message: message)
+            }
+        } else {
+            throw TachikomaError.apiError(message: "HTTP \(response.statusCode)")
+        }
+    }
+}
+
+// MARK: - Helper Types
+
+private class PartialToolCall {
+    let id: String
+    let name: String
+    let index: Int
+    var arguments: String = ""
+
+    init(id: String, name: String, index: Int) {
+        self.id = id
+        self.name = name
+        self.index = index
+    }
+
+    func appendArguments(_ args: String) {
+        self.arguments += args
+    }
+
+    func toCompleted() -> FunctionCall? {
+        FunctionCall(name: self.name, arguments: self.arguments)
+    }
+}
\ No newline at end of file
diff --git a/Sources/Providers/Anthropic/AnthropicTypes.swift b/Sources/Providers/Anthropic/AnthropicTypes.swift
new file mode 100644
index 0000000..1e91af9
--- /dev/null
+++ b/Sources/Providers/Anthropic/AnthropicTypes.swift
@@ -0,0 +1,678 @@
+import Foundation
+
+// MARK: - Anthropic API Request Types
+
+/// Cache control configuration
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicCacheControl: Codable, Sendable {
+    public let type: String // "ephemeral"
+
+    public init(type: String = "ephemeral") {
+        self.type = type
+    }
+}
+
+/// System content that can be cached
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum AnthropicSystemContent: Codable, Sendable {
+    case string(String)
+    case array([AnthropicSystemBlock])
+
+    // Custom encoding/decoding
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.singleValueContainer()
+
+        if let stringValue = try? container.decode(String.self) {
+            self = .string(stringValue)
+        } else if let arrayValue = try? container.decode([AnthropicSystemBlock].self) {
+            self = .array(arrayValue)
+        } else {
+            throw DecodingError.typeMismatch(
+                AnthropicSystemContent.self,
+                DecodingError.Context(
+                    codingPath: decoder.codingPath,
+                    debugDescription: "Expected String or Array of system blocks"))
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.singleValueContainer()
+        switch self {
+        case let .string(value):
+            try container.encode(value)
+        case let .array(blocks):
+            try container.encode(blocks)
+        }
+    }
+}
+
+/// System block that can contain cache control
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicSystemBlock: Codable, Sendable {
+    public let type: String // "text"
+    public let text: String
+    public let cacheControl: AnthropicCacheControl?
+
+    enum CodingKeys: String, CodingKey {
+        case type, text
+        case cacheControl = "cache_control"
+    }
+
+    public init(type: String = "text", text: String, cacheControl: AnthropicCacheControl? = nil) {
+        self.type = type
+        self.text = text
+        self.cacheControl = cacheControl
+    }
+}
+
+/// Main request structure for Anthropic's Messages API
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicRequest: Codable, Sendable {
+    /// ID of the model to use (e.g., "claude-3-opus-20240229")
+    public let model: String
+
+    /// Input messages
+    public let messages: [AnthropicMessage]
+
+    /// System prompt (separate from messages)
+    public let system: AnthropicSystemContent?
+
+    /// Maximum number of tokens to generate
+    public let maxTokens: Int
+
+    /// Temperature for randomness (0.0 to 1.0)
+    public let temperature: Double?
+
+    /// Top-p sampling parameter
+    public let topP: Double?
+
+    /// Top-k sampling parameter
+    public let topK: Int?
+
+    /// Whether to stream the response
+    public let stream: Bool?
+
+    /// Stop sequences
+    public let stopSequences: [String]?
+
+    /// Available tools
+    public let tools: [AnthropicTool]?
+
+    /// Tool choice configuration
+    public let toolChoice: AnthropicToolChoice?
+
+    /// Metadata about the request
+    public let metadata: AnthropicMetadata?
+
+    enum CodingKeys: String, CodingKey {
+        case model, messages, system
+        case maxTokens = "max_tokens"
+        case temperature
+        case topP = "top_p"
+        case topK = "top_k"
+        case stream
+        case stopSequences = "stop_sequences"
+        case tools
+        case toolChoice = "tool_choice"
+        case metadata
+    }
+}
+
+/// Anthropic message structure
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicMessage: Codable, Sendable {
+    /// Role of the message sender
+    public let role: AnthropicRole
+
+    /// Content of the message
+    public let content: AnthropicContent
+
+    public init(role: AnthropicRole, content: AnthropicContent) {
+        self.role = role
+        self.content = content
+    }
+}
+
+/// Message roles in Anthropic API
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum AnthropicRole: String, Codable, Sendable {
+    case user
+    case assistant
+}
+
+/// Content types for Anthropic messages
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum AnthropicContent: Codable, Sendable {
+    case string(String)
+    case array([AnthropicContentBlock])
+
+    // Custom encoding/decoding
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.singleValueContainer()
+
+        if let stringValue = try? container.decode(String.self) {
+            self = .string(stringValue)
+        } else if let arrayValue = try? container.decode([AnthropicContentBlock].self) {
+            self = .array(arrayValue)
+        } else {
+            throw DecodingError.typeMismatch(
+                AnthropicContent.self,
+                DecodingError.Context(
+                    codingPath: decoder.codingPath,
+                    debugDescription: "Expected String or Array of content blocks"))
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.singleValueContainer()
+        switch self {
+        case let .string(value):
+            try container.encode(value)
+        case let .array(blocks):
+            try container.encode(blocks)
+        }
+    }
+}
+
+/// Content block for multimodal messages
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicContentBlock: Codable, Sendable {
+    public let type: String
+
+    // Text content
+    public let text: String?
+
+    // Image content
+    public let source: AnthropicImageSource?
+
+    // Tool use content
+    public let id: String?
+    public let name: String?
+    public let input: [String: AnthropicInputValue]?
+
+    // Tool result content
+    public let toolUseId: String?
+    public let content: AnthropicContent?
+    public let isError: Bool?
+
+    // Cache control
+    public let cacheControl: AnthropicCacheControl?
+
+    enum CodingKeys: String, CodingKey {
+        case type, text, source, id, name, input
+        case toolUseId = "tool_use_id"
+        case content
+        case isError = "is_error"
+        case cacheControl = "cache_control"
+    }
+}
+
+/// Image source for content blocks
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicImageSource: Codable, Sendable {
+    public let type: String // "base64"
+    public let mediaType: String // "image/jpeg", "image/png", etc.
+    public let data: String // base64 encoded image data
+
+    enum CodingKeys: String, CodingKey {
+        case type
+        case mediaType = "media_type"
+        case data
+    }
+}
+
+// MARK: - Tool Definitions
+
+/// Tool definition for Anthropic
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicTool: Codable, Sendable {
+    public let name: String
+    public let description: String
+    public let inputSchema: AnthropicJSONSchema
+    public let cacheControl: AnthropicCacheControl?
+
+    enum CodingKeys: String, CodingKey {
+        case name, description
+        case inputSchema = "input_schema"
+        case cacheControl = "cache_control"
+    }
+
+    public init(
+        name: String,
+        description: String,
+        inputSchema: AnthropicJSONSchema,
+        cacheControl: AnthropicCacheControl? = nil)
+    {
+        self.name = name
+        self.description = description
+        self.inputSchema = inputSchema
+        self.cacheControl = cacheControl
+    }
+}
+
+/// JSON Schema for tool parameters
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicJSONSchema: Codable, Sendable {
+    public let type: String
+    public let properties: [String: AnthropicPropertySchema]?
+    public let required: [String]?
+    public let description: String?
+
+    public init(
+        type: String = "object",
+        properties: [String: AnthropicPropertySchema]? = nil,
+        required: [String]? = nil,
+        description: String? = nil)
+    {
+        self.type = type
+        self.properties = properties
+        self.required = required
+        self.description = description
+    }
+}
+
+/// Tool choice configuration
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum AnthropicToolChoice: Codable, Sendable {
+    case auto
+    case any
+    case tool(name: String)
+
+    // Custom encoding/decoding
+    enum CodingKeys: String, CodingKey {
+        case type, name
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let type = try container.decode(String.self, forKey: .type)
+
+        switch type {
+        case "auto":
+            self = .auto
+        case "any":
+            self = .any
+        case "tool":
+            let name = try container.decode(String.self, forKey: .name)
+            self = .tool(name: name)
+        default:
+            throw DecodingError.dataCorruptedError(
+                forKey: .type,
+                in: container,
+                debugDescription: "Unknown tool choice type: \(type)")
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+
+        switch self {
+        case .auto:
+            try container.encode("auto", forKey: .type)
+        case .any:
+            try container.encode("any", forKey: .type)
+        case let .tool(name):
+            try container.encode("tool", forKey: .type)
+            try container.encode(name, forKey: .name)
+        }
+    }
+}
+
+/// Metadata for requests
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicMetadata: Codable, Sendable {
+    public let userId: String?
+
+    enum CodingKeys: String, CodingKey {
+        case userId = "user_id"
+    }
+}
+
+// MARK: - Response Types
+
+/// Response from Anthropic's Messages API
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicResponse: Codable, Sendable {
+    public let id: String
+    public let type: String
+    public let role: AnthropicRole
+    public let content: [AnthropicContentBlock]
+    public let model: String
+    public let stopReason: String?
+    public let stopSequence: String?
+    public let usage: AnthropicUsage
+
+    enum CodingKeys: String, CodingKey {
+        case id, type, role, content, model
+        case stopReason = "stop_reason"
+        case stopSequence = "stop_sequence"
+        case usage
+    }
+}
+
+/// Usage statistics
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicUsage: Codable, Sendable {
+    public let inputTokens: Int
+    public let outputTokens: Int
+
+    enum CodingKeys: String, CodingKey {
+        case inputTokens = "input_tokens"
+        case outputTokens = "output_tokens"
+    }
+}
+
+// MARK: - Streaming Types
+
+/// Server-sent event for streaming
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicStreamEvent: Codable, Sendable {
+    public let type: String
+
+    // Common fields
+    public let index: Int?
+    public let delta: AnthropicDelta?
+
+    // Message start
+    public let message: AnthropicStreamMessage?
+
+    // Content block start
+    public let contentBlock: AnthropicContentBlock?
+
+    // Message complete
+    public let usage: AnthropicUsage?
+    public let stopReason: String?
+    public let stopSequence: String?
+
+    // Error
+    public let error: AnthropicError?
+
+    enum CodingKeys: String, CodingKey {
+        case type, index, delta, message
+        case contentBlock = "content_block"
+        case usage
+        case stopReason = "stop_reason"
+        case stopSequence = "stop_sequence"
+        case error
+    }
+}
+
+/// Stream message metadata
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicStreamMessage: Codable, Sendable {
+    public let id: String
+    public let type: String
+    public let role: AnthropicRole
+    public let content: [AnthropicContentBlock]
+    public let model: String
+    public let usage: AnthropicUsage
+
+    enum CodingKeys: String, CodingKey {
+        case id, type, role, content, model, usage
+    }
+}
+
+/// Delta updates for streaming
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicDelta: Codable, Sendable {
+    // Text delta
+    public let text: String?
+
+    // Message delta fields
+    public let stopReason: String?
+    public let stopSequence: String?
+
+    // Tool use delta
+    public let type: String?
+    public let partialJson: String?
+
+    enum CodingKeys: String, CodingKey {
+        case text
+        case stopReason = "stop_reason"
+        case stopSequence = "stop_sequence"
+        case type
+        case partialJson = "partial_json"
+    }
+}
+
+// MARK: - Error Types
+
+/// Anthropic error response
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicErrorResponse: Codable, Sendable {
+    public let error: AnthropicError
+
+    public var message: String {
+        self.error.message
+    }
+
+    public var code: String? {
+        nil // Anthropic doesn't provide error codes
+    }
+
+    public var type: String? {
+        self.error.type
+    }
+}
+
+/// Error details
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicError: Codable, Sendable {
+    public let type: String
+    public let message: String
+}
+
+// MARK: - Helper Extensions
+
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+extension AnthropicContentBlock {
+    /// Create a text content block
+    public static func text(_ text: String, cacheControl: AnthropicCacheControl? = nil) -> AnthropicContentBlock {
+        AnthropicContentBlock(
+            type: "text",
+            text: text,
+            source: nil,
+            id: nil,
+            name: nil,
+            input: nil,
+            toolUseId: nil,
+            content: nil,
+            isError: nil,
+            cacheControl: cacheControl)
+    }
+
+    /// Create an image content block
+    public static func image(
+        base64: String,
+        mediaType: String,
+        cacheControl: AnthropicCacheControl? = nil) -> AnthropicContentBlock
+    {
+        AnthropicContentBlock(
+            type: "image",
+            text: nil,
+            source: AnthropicImageSource(
+                type: "base64",
+                mediaType: mediaType,
+                data: base64),
+            id: nil,
+            name: nil,
+            input: nil,
+            toolUseId: nil,
+            content: nil,
+            isError: nil,
+            cacheControl: cacheControl)
+    }
+
+    /// Create a tool use content block
+    public static func toolUse(id: String, name: String, input: [String: Any]) -> AnthropicContentBlock {
+        AnthropicContentBlock(
+            type: "tool_use",
+            text: nil,
+            source: nil,
+            id: id,
+            name: name,
+            input: input.compactMapValues { AnthropicInputValue(from: $0) },
+            toolUseId: nil,
+            content: nil,
+            isError: nil,
+            cacheControl: nil)
+    }
+
+    /// Create a tool result content block
+    public static func toolResult(toolUseId: String, content: String, isError: Bool = false) -> AnthropicContentBlock {
+        AnthropicContentBlock(
+            type: "tool_result",
+            text: nil,
+            source: nil,
+            id: nil,
+            name: nil,
+            input: nil,
+            toolUseId: toolUseId,
+            content: .string(content),
+            isError: isError,
+            cacheControl: nil)
+    }
+}
+
+// MARK: - Input Value Types
+
+/// Type-safe input value for Anthropic tool use
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public enum AnthropicInputValue: Codable, Sendable {
+    case string(String)
+    case int(Int)
+    case double(Double)
+    case bool(Bool)
+    case array([AnthropicInputValue])
+    case object([String: AnthropicInputValue])
+    case null
+
+    // MARK: - Codable
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.singleValueContainer()
+
+        if container.decodeNil() {
+            self = .null
+        } else if let string = try? container.decode(String.self) {
+            self = .string(string)
+        } else if let int = try? container.decode(Int.self) {
+            self = .int(int)
+        } else if let double = try? container.decode(Double.self) {
+            self = .double(double)
+        } else if let bool = try? container.decode(Bool.self) {
+            self = .bool(bool)
+        } else if let array = try? container.decode([AnthropicInputValue].self) {
+            self = .array(array)
+        } else if let dict = try? container.decode([String: AnthropicInputValue].self) {
+            self = .object(dict)
+        } else {
+            throw DecodingError.dataCorruptedError(in: container, debugDescription: "Cannot decode AnthropicInputValue")
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.singleValueContainer()
+
+        switch self {
+        case let .string(value):
+            try container.encode(value)
+        case let .int(value):
+            try container.encode(value)
+        case let .double(value):
+            try container.encode(value)
+        case let .bool(value):
+            try container.encode(value)
+        case let .array(values):
+            try container.encode(values)
+        case let .object(dict):
+            try container.encode(dict)
+        case .null:
+            try container.encodeNil()
+        }
+    }
+
+    // MARK: - Conversion
+
+    /// Convert from Any value (for migration)
+    public init?(from value: Any) {
+        switch value {
+        case let string as String:
+            self = .string(string)
+        case let int as Int:
+            self = .int(int)
+        case let double as Double:
+            self = .double(double)
+        case let bool as Bool:
+            self = .bool(bool)
+        case let array as [Any]:
+            let values = array.compactMap { AnthropicInputValue(from: $0) }
+            if values.count == array.count {
+                self = .array(values)
+            } else {
+                return nil
+            }
+        case let dict as [String: Any]:
+            var values: [String: AnthropicInputValue] = [:]
+            for (key, val) in dict {
+                if let inputValue = AnthropicInputValue(from: val) {
+                    values[key] = inputValue
+                } else {
+                    return nil
+                }
+            }
+            self = .object(values)
+        case is NSNull:
+            self = .null
+        default:
+            return nil
+        }
+    }
+
+    /// Convert to Any (for JSON serialization)
+    public func toAny() -> Any {
+        switch self {
+        case let .string(value):
+            value
+        case let .int(value):
+            value
+        case let .double(value):
+            value
+        case let .bool(value):
+            value
+        case let .array(values):
+            values.map { $0.toAny() }
+        case let .object(dict):
+            dict.mapValues { $0.toAny() }
+        case .null:
+            NSNull()
+        }
+    }
+}
+
+/// Type-safe property schema for Anthropic JSON Schema
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnthropicPropertySchema: Codable, Sendable {
+    public let type: String
+    public let description: String?
+    public let `enum`: [String]?
+    public let items: Box<AnthropicPropertySchema>?
+    public let properties: [String: AnthropicPropertySchema]?
+    public let required: [String]?
+
+    public init(
+        type: String,
+        description: String? = nil,
+        enum enumValues: [String]? = nil,
+        items: AnthropicPropertySchema? = nil,
+        properties: [String: AnthropicPropertySchema]? = nil,
+        required: [String]? = nil)
+    {
+        self.type = type
+        self.description = description
+        self.enum = enumValues
+        self.items = items.map(Box.init)
+        self.properties = properties
+        self.required = required
+    }
+}
\ No newline at end of file
diff --git a/Sources/Providers/Grok/GrokModel.swift b/Sources/Providers/Grok/GrokModel.swift
new file mode 100644
index 0000000..d397ece
--- /dev/null
+++ b/Sources/Providers/Grok/GrokModel.swift
@@ -0,0 +1,479 @@
+import Foundation
+
+/// Grok model implementation using OpenAI-compatible Chat Completions API
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public final class GrokModel: ModelInterface, Sendable {
+    private let apiKey: String
+    private let modelName: String
+    private let baseURL: URL
+    private let session: URLSession
+
+    public init(
+        apiKey: String,
+        modelName: String = "grok-4-0709",
+        baseURL: URL = URL(string: "https://api.x.ai/v1")!,
+        session: URLSession? = nil)
+    {
+        self.apiKey = apiKey
+        self.modelName = modelName
+        self.baseURL = baseURL
+
+        // Create custom session with appropriate timeout
+        if let session {
+            self.session = session
+        } else {
+            let config = URLSessionConfiguration.default
+            config.timeoutIntervalForRequest = 300 // 5 minutes
+            config.timeoutIntervalForResource = 300
+            self.session = URLSession(configuration: config)
+        }
+    }
+
+    // MARK: - ModelInterface Implementation
+
+    public var maskedApiKey: String {
+        guard self.apiKey.count > 8 else { return "***" }
+        let start = self.apiKey.prefix(6)
+        let end = self.apiKey.suffix(2)
+        return "\(start)...\(end)"
+    }
+
+    public func getResponse(request: ModelRequest) async throws -> ModelResponse {
+        let grokRequest = try convertToGrokRequest(request, stream: false)
+        let urlRequest = try createURLRequest(endpoint: "chat/completions", body: grokRequest)
+
+        let (data, response) = try await session.data(for: urlRequest)
+
+        guard let httpResponse = response as? HTTPURLResponse else {
+            throw TachikomaError.networkError(underlying: URLError(.badServerResponse))
+        }
+
+        if httpResponse.statusCode != 200 {
+            try handleErrorResponse(data: data, response: httpResponse)
+        }
+
+        let chatResponse = try JSONDecoder().decode(GrokChatCompletionResponse.self, from: data)
+        return try self.convertFromGrokResponse(chatResponse)
+    }
+
+    public func getStreamedResponse(request: ModelRequest) async throws -> AsyncThrowingStream<StreamEvent, any Error> {
+        let grokRequest = try convertToGrokRequest(request, stream: true)
+        let urlRequest = try createURLRequest(endpoint: "chat/completions", body: grokRequest)
+
+        return AsyncThrowingStream { continuation in
+            Task {
+                do {
+                    let (bytes, response) = try await session.bytes(for: urlRequest)
+
+                    guard let httpResponse = response as? HTTPURLResponse else {
+                        continuation.finish(throwing: TachikomaError.networkError(underlying: URLError(.badServerResponse)))
+                        return
+                    }
+
+                    if httpResponse.statusCode != 200 {
+                        var errorData = Data()
+                        for try await byte in bytes.prefix(1024) {
+                            errorData.append(byte)
+                        }
+                        try self.handleErrorResponse(data: errorData, response: httpResponse)
+                    }
+
+                    // Process SSE stream
+                    var currentToolCalls: [String: GrokPartialToolCall] = [:]
+
+                    for try await line in bytes.lines {
+                        // Handle SSE format
+                        if line.hasPrefix("data: ") {
+                            let data = String(line.dropFirst(6))
+
+                            if data == "[DONE]" {
+                                // Send any pending tool calls
+                                for (id, toolCall) in currentToolCalls {
+                                    if let completed = toolCall.toCompleted() {
+                                        continuation.yield(.toolCallCompleted(
+                                            StreamToolCallCompleted(id: id, function: completed)))
+                                    }
+                                }
+                                continuation.finish()
+                                return
+                            }
+
+                            // Parse chunk
+                            if let chunkData = data.data(using: .utf8),
+                               let chunk = try? JSONDecoder().decode(
+                                   GrokChatCompletionChunk.self,
+                                   from: chunkData)
+                            {
+                                if let events = self.processGrokChunk(chunk, toolCalls: &currentToolCalls) {
+                                    for event in events {
+                                        continuation.yield(event)
+                                    }
+                                }
+                            }
+                        }
+                    }
+
+                    continuation.finish()
+                } catch {
+                    continuation.finish(throwing: TachikomaError.streamingError(error.localizedDescription))
+                }
+            }
+        }
+    }
+
+    // MARK: - Private Helper Methods
+
+    private func createURLRequest(endpoint: String, body: any Encodable) throws -> URLRequest {
+        let url = self.baseURL.appendingPathComponent(endpoint)
+        var request = URLRequest(url: url)
+        request.httpMethod = "POST"
+        request.setValue("Bearer \(self.apiKey)", forHTTPHeaderField: "Authorization")
+        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
+
+        let encoder = JSONEncoder()
+        encoder.outputFormatting = .sortedKeys
+
+        do {
+            request.httpBody = try encoder.encode(body)
+        } catch {
+            throw TachikomaError.configurationError("Failed to encode Grok request: \(error.localizedDescription)")
+        }
+
+        request.timeoutInterval = 300 // 5 minutes for Grok
+
+        return request
+    }
+
+    private func convertToGrokRequest(_ request: ModelRequest, stream: Bool) throws -> GrokChatCompletionRequest {
+        // Convert messages to OpenAI-compatible format
+        let messages = try request.messages.map { message -> GrokMessage in
+            switch message {
+            case let .system(_, content):
+                return GrokMessage(role: "system", content: .string(content), toolCalls: nil, toolCallId: nil)
+
+            case let .user(_, content):
+                return try self.convertUserMessageContent(content)
+
+            case let .assistant(_, content, _):
+                return try self.convertAssistantMessageContent(content)
+
+            case let .tool(_, toolCallId, content):
+                return GrokMessage(
+                    role: "tool",
+                    content: .string(content),
+                    toolCalls: nil,
+                    toolCallId: toolCallId)
+
+            case .reasoning:
+                throw TachikomaError.invalidRequest("Reasoning messages not supported in Grok")
+            }
+        }
+
+        // Convert tools to OpenAI-compatible format if present
+        let tools = request.tools?.map { toolDef -> GrokTool in
+            GrokTool(
+                type: "function",
+                function: GrokTool.Function(
+                    name: toolDef.function.name,
+                    description: toolDef.function.description,
+                    parameters: self.convertToolParameters(toolDef.function.parameters)))
+        }
+
+        // Filter parameters for Grok 4
+        let temperature = request.settings.temperature
+        var frequencyPenalty = request.settings.frequencyPenalty
+        var presencePenalty = request.settings.presencePenalty
+        var stop = request.settings.stopSequences
+
+        if self.modelName.contains("grok-4") || self.modelName.contains("grok-3") {
+            // Grok 3 and 4 models don't support these parameters
+            frequencyPenalty = nil
+            presencePenalty = nil
+            stop = nil
+        }
+
+        return GrokChatCompletionRequest(
+            model: self.modelName,
+            messages: messages,
+            tools: tools,
+            toolChoice: self.convertToolChoice(request.settings.toolChoice),
+            temperature: temperature,
+            maxTokens: request.settings.maxTokens,
+            stream: stream,
+            frequencyPenalty: frequencyPenalty,
+            presencePenalty: presencePenalty,
+            stop: stop)
+    }
+
+    private func convertUserMessageContent(_ content: MessageContent) throws -> GrokMessage {
+        switch content {
+        case let .text(text):
+            return GrokMessage(role: "user", content: .string(text), toolCalls: nil, toolCallId: nil)
+
+        case let .image(imageContent):
+            var content: [GrokMessageContentPart] = []
+
+            if let url = imageContent.url {
+                content.append(GrokMessageContentPart(
+                    type: "image_url",
+                    text: nil,
+                    imageUrl: GrokImageUrl(
+                        url: url,
+                        detail: imageContent.detail?.rawValue)))
+            } else if let base64 = imageContent.base64 {
+                content.append(GrokMessageContentPart(
+                    type: "image_url",
+                    text: nil,
+                    imageUrl: GrokImageUrl(
+                        url: "data:image/jpeg;base64,\(base64)",
+                        detail: imageContent.detail?.rawValue)))
+            }
+
+            return GrokMessage(role: "user", content: .array(content), toolCalls: nil, toolCallId: nil)
+
+        case let .multimodal(parts):
+            let content = parts.compactMap { part -> GrokMessageContentPart? in
+                if let text = part.text {
+                    return GrokMessageContentPart(
+                        type: "text",
+                        text: text,
+                        imageUrl: nil)
+                } else if let image = part.imageUrl {
+                    if let url = image.url {
+                        return GrokMessageContentPart(
+                            type: "image_url",
+                            text: nil,
+                            imageUrl: GrokImageUrl(url: url, detail: image.detail?.rawValue))
+                    } else if let base64 = image.base64 {
+                        return GrokMessageContentPart(
+                            type: "image_url",
+                            text: nil,
+                            imageUrl: GrokImageUrl(
+                                url: "data:image/jpeg;base64,\(base64)",
+                                detail: image.detail?.rawValue))
+                    }
+                }
+                return nil
+            }
+            return GrokMessage(role: "user", content: .array(content), toolCalls: nil, toolCallId: nil)
+
+        case .file:
+            throw TachikomaError.invalidRequest("File content not supported in Grok chat completions")
+
+        case let .audio(audioContent):
+            // Grok doesn't support native audio, so we need to use the transcript
+            if let transcript = audioContent.transcript {
+                // Include metadata about the audio source
+                var text = transcript
+                if let duration = audioContent.duration {
+                    text = "[Audio transcript, duration: \(Int(duration))s] \(transcript)"
+                } else {
+                    text = "[Audio transcript] \(transcript)"
+                }
+                return GrokMessage(role: "user", content: .string(text), toolCalls: nil, toolCallId: nil)
+            } else {
+                throw TachikomaError.invalidRequest("Audio content must be transcribed before sending to Grok. Please ensure transcript is provided.")
+            }
+        }
+    }
+
+    private func convertAssistantMessageContent(_ contentArray: [AssistantContent]) throws -> GrokMessage {
+        var textContent = ""
+        var toolCalls: [GrokToolCall] = []
+
+        for content in contentArray {
+            switch content {
+            case let .outputText(text):
+                textContent += text
+
+            case let .refusal(refusal):
+                return GrokMessage(role: "assistant", content: .string(refusal), toolCalls: nil, toolCallId: nil)
+
+            case let .toolCall(toolCall):
+                toolCalls.append(GrokToolCall(
+                    id: toolCall.id,
+                    type: toolCall.type.rawValue,
+                    function: GrokFunctionCall(
+                        name: toolCall.function.name,
+                        arguments: toolCall.function.arguments)))
+            }
+        }
+
+        // Include tool calls if present
+        if !toolCalls.isEmpty {
+            return GrokMessage(
+                role: "assistant",
+                content: textContent.isEmpty ? nil : .string(textContent),
+                toolCalls: toolCalls,
+                toolCallId: nil)
+        }
+
+        return GrokMessage(role: "assistant", content: .string(textContent), toolCalls: nil, toolCallId: nil)
+    }
+
+    private func convertToolParameters(_ params: ToolParameters) -> GrokTool.Parameters {
+        let (type, properties, required) = params.toGrokParameters()
+        return GrokTool.Parameters(
+            type: type,
+            properties: properties,
+            required: required)
+    }
+
+    private func convertToolChoice(_ toolChoice: ToolChoice?) -> GrokToolChoice? {
+        guard let toolChoice else { return nil }
+
+        switch toolChoice {
+        case .auto:
+            return .string("auto")
+        case .none:
+            return .string("none")
+        case .required:
+            return .string("required")
+        case let .specific(toolName):
+            return .object(GrokToolChoiceObject(
+                type: "function",
+                function: GrokToolChoiceFunction(name: toolName)))
+        }
+    }
+
+    private func convertFromGrokResponse(_ response: GrokChatCompletionResponse) throws -> ModelResponse {
+        guard let choice = response.choices.first else {
+            throw TachikomaError.apiError(message: "No choices in response")
+        }
+
+        var content: [AssistantContent] = []
+
+        // Add text content if present
+        if let textContent = choice.message.content {
+            content.append(.outputText(textContent))
+        }
+
+        // Add tool calls if present
+        if let toolCalls = choice.message.toolCalls {
+            for toolCall in toolCalls {
+                content.append(.toolCall(ToolCallItem(
+                    id: toolCall.id,
+                    type: .function,
+                    function: FunctionCall(
+                        name: toolCall.function.name,
+                        arguments: toolCall.function.arguments))))
+            }
+        }
+
+        let usage = response.usage.map { usage in
+            Usage(
+                promptTokens: usage.promptTokens,
+                completionTokens: usage.completionTokens,
+                totalTokens: usage.totalTokens,
+                promptTokensDetails: nil,
+                completionTokensDetails: nil)
+        }
+
+        return ModelResponse(
+            id: response.id,
+            model: response.model,
+            content: content,
+            usage: usage,
+            flagged: false,
+            finishReason: self.convertFinishReason(choice.finishReason))
+    }
+
+    private func convertFinishReason(_ reason: String?) -> FinishReason? {
+        guard let reason else { return nil }
+        return FinishReason(rawValue: reason)
+    }
+
+    private func processGrokChunk(
+        _ chunk: GrokChatCompletionChunk,
+        toolCalls: inout [String: GrokPartialToolCall]) -> [StreamEvent]?
+    {
+        var events: [StreamEvent] = []
+
+        // First chunk often contains metadata
+        if !chunk.id.isEmpty, chunk.model.isEmpty == false {
+            events.append(.responseStarted(StreamResponseStarted(
+                id: chunk.id,
+                model: chunk.model,
+                systemFingerprint: chunk.systemFingerprint)))
+        }
+
+        for choice in chunk.choices {
+            let delta = choice.delta
+
+            // Handle text content
+            if let content = delta.content, !content.isEmpty {
+                events.append(.textDelta(StreamTextDelta(delta: content, index: choice.index)))
+            }
+
+            // Handle tool calls
+            if let deltaToolCalls = delta.toolCalls {
+                for toolCallDelta in deltaToolCalls {
+                    let toolCallId = toolCallDelta.id ?? ""
+
+                    if toolCalls[toolCallId] == nil {
+                        let partialCall = GrokPartialToolCall(from: toolCallDelta)
+                        toolCalls[toolCallId] = partialCall
+                    } else {
+                        toolCalls[toolCallId]?.update(with: toolCallDelta)
+                    }
+
+                    // Emit delta event
+                    if let functionDelta = toolCallDelta.function {
+                        events.append(.toolCallDelta(StreamToolCallDelta(
+                            id: toolCallId,
+                            index: toolCallDelta.index,
+                            function: FunctionCallDelta(
+                                name: functionDelta.name,
+                                arguments: functionDelta.arguments))))
+                    }
+                }
+            }
+
+            // Handle finish reason
+            if let finishReason = choice.finishReason {
+                // If this is a tool call finish, emit completed events
+                if finishReason == "tool_calls" {
+                    for (id, toolCall) in toolCalls {
+                        if let completed = toolCall.toCompleted() {
+                            events.append(.toolCallCompleted(
+                                StreamToolCallCompleted(id: id, function: completed)))
+                        }
+                    }
+                }
+
+                events.append(.responseCompleted(StreamResponseCompleted(
+                    id: chunk.id,
+                    usage: nil,
+                    finishReason: FinishReason(rawValue: finishReason))))
+            }
+        }
+
+        return events.isEmpty ? nil : events
+    }
+
+    private func handleErrorResponse(data: Data, response: HTTPURLResponse) throws {
+        if let errorResponse = try? JSONDecoder().decode(GrokErrorResponse.self, from: data) {
+            let message = errorResponse.error.message
+            
+            switch response.statusCode {
+            case 401:
+                throw TachikomaError.authenticationFailed
+            case 429:
+                throw TachikomaError.rateLimited
+            case 400:
+                if message.contains("credit") || message.contains("usage") {
+                    throw TachikomaError.insufficientQuota
+                } else {
+                    throw TachikomaError.invalidRequest(message)
+                }
+            case 500...599:
+                throw TachikomaError.modelOverloaded
+            default:
+                throw TachikomaError.apiError(message: message, code: errorResponse.error.code)
+            }
+        } else {
+            throw TachikomaError.apiError(message: "HTTP \(response.statusCode)")
+        }
+    }
+}
+
diff --git a/Sources/Providers/Grok/GrokTypes.swift b/Sources/Providers/Grok/GrokTypes.swift
new file mode 100644
index 0000000..cbee943
--- /dev/null
+++ b/Sources/Providers/Grok/GrokTypes.swift
@@ -0,0 +1,346 @@
+import Foundation
+
+// MARK: - Helper Types
+
+internal class GrokPartialToolCall {
+    var id: String = ""
+    var type: String = "function"
+    var index: Int = 0
+    var name: String?
+    var arguments: String = ""
+
+    init() {
+        // Default initializer
+    }
+
+    init(from delta: GrokToolCallDelta) {
+        self.id = delta.id ?? ""
+        self.index = delta.index
+        self.name = delta.function?.name
+        self.arguments = delta.function?.arguments ?? ""
+    }
+
+    func update(with delta: GrokToolCallDelta) {
+        if let funcName = delta.function?.name {
+            self.name = funcName
+        }
+        if let args = delta.function?.arguments {
+            self.arguments += args
+        }
+    }
+
+    func toCompleted() -> FunctionCall? {
+        guard let name else { return nil }
+        return FunctionCall(name: name, arguments: self.arguments)
+    }
+}
+
+// MARK: - Grok Request Types
+
+internal struct GrokChatCompletionRequest: Encodable {
+    let model: String
+    let messages: [GrokMessage]
+    let tools: [GrokTool]?
+    let toolChoice: GrokToolChoice?
+    let temperature: Double?
+    let maxTokens: Int?
+    let stream: Bool
+    let frequencyPenalty: Double?
+    let presencePenalty: Double?
+    let stop: [String]?
+
+    enum CodingKeys: String, CodingKey {
+        case model, messages, tools, temperature, stream
+        case toolChoice = "tool_choice"
+        case maxTokens = "max_tokens"
+        case frequencyPenalty = "frequency_penalty"
+        case presencePenalty = "presence_penalty"
+        case stop
+    }
+}
+
+internal struct GrokMessage: Encodable {
+    let role: String
+    let content: GrokMessageContent?
+    let toolCalls: [GrokToolCall]?
+    let toolCallId: String?
+
+    enum CodingKeys: String, CodingKey {
+        case role, content
+        case toolCalls = "tool_calls"
+        case toolCallId = "tool_call_id"
+    }
+}
+
+internal enum GrokMessageContent: Encodable {
+    case string(String)
+    case array([GrokMessageContentPart])
+
+    func encode(to encoder: any Encoder) throws {
+        var container = encoder.singleValueContainer()
+        switch self {
+        case let .string(text):
+            try container.encode(text)
+        case let .array(parts):
+            try container.encode(parts)
+        }
+    }
+}
+
+internal struct GrokMessageContentPart: Encodable {
+    let type: String
+    let text: String?
+    let imageUrl: GrokImageUrl?
+
+    enum CodingKeys: String, CodingKey {
+        case type, text
+        case imageUrl = "image_url"
+    }
+}
+
+internal struct GrokImageUrl: Encodable {
+    let url: String
+    let detail: String?
+}
+
+internal struct GrokToolCall: Encodable {
+    let id: String
+    let type: String
+    let function: GrokFunctionCall
+}
+
+internal struct GrokFunctionCall: Encodable {
+    let name: String
+    let arguments: String
+}
+
+internal struct GrokTool: Encodable {
+    let type: String
+    let function: Function
+
+    struct Function: Encodable {
+        let name: String
+        let description: String?
+        let parameters: Parameters
+    }
+
+    struct Parameters: Encodable {
+        let type: String
+        let properties: [String: GrokPropertySchema]
+        let required: [String]
+    }
+}
+
+internal enum GrokToolChoice: Encodable {
+    case string(String)
+    case object(GrokToolChoiceObject)
+
+    func encode(to encoder: any Encoder) throws {
+        var container = encoder.singleValueContainer()
+        switch self {
+        case let .string(value):
+            try container.encode(value)
+        case let .object(obj):
+            try container.encode(obj)
+        }
+    }
+}
+
+internal struct GrokToolChoiceObject: Encodable {
+    let type: String
+    let function: GrokToolChoiceFunction
+}
+
+internal struct GrokToolChoiceFunction: Encodable {
+    let name: String
+}
+
+// MARK: - Response Types
+
+internal struct GrokChatCompletionResponse: Decodable {
+    let id: String
+    let model: String
+    let choices: [Choice]
+    let usage: Usage?
+
+    struct Choice: Decodable {
+        let message: Message
+        let finishReason: String?
+
+        enum CodingKeys: String, CodingKey {
+            case message
+            case finishReason = "finish_reason"
+        }
+    }
+
+    struct Message: Decodable {
+        let role: String
+        let content: String?
+        let toolCalls: [ToolCall]?
+
+        enum CodingKeys: String, CodingKey {
+            case role, content
+            case toolCalls = "tool_calls"
+        }
+
+        struct ToolCall: Decodable {
+            let id: String
+            let type: String
+            let function: Function
+
+            struct Function: Decodable {
+                let name: String
+                let arguments: String
+            }
+        }
+    }
+
+    struct Usage: Decodable {
+        let promptTokens: Int
+        let completionTokens: Int
+        let totalTokens: Int
+
+        enum CodingKeys: String, CodingKey {
+            case promptTokens = "prompt_tokens"
+            case completionTokens = "completion_tokens"
+            case totalTokens = "total_tokens"
+        }
+    }
+}
+
+// MARK: - Streaming Types
+
+internal struct GrokChatCompletionChunk: Decodable {
+    let id: String
+    let model: String
+    let choices: [StreamChoice]
+    let systemFingerprint: String?
+
+    enum CodingKeys: String, CodingKey {
+        case id, model, choices
+        case systemFingerprint = "system_fingerprint"
+    }
+
+    struct StreamChoice: Decodable {
+        let index: Int
+        let delta: Delta
+        let finishReason: String?
+
+        enum CodingKeys: String, CodingKey {
+            case index, delta
+            case finishReason = "finish_reason"
+        }
+
+        struct Delta: Decodable {
+            let role: String?
+            let content: String?
+            let toolCalls: [GrokToolCallDelta]?
+
+            enum CodingKeys: String, CodingKey {
+                case role, content
+                case toolCalls = "tool_calls"
+            }
+        }
+    }
+}
+
+internal struct GrokToolCallDelta: Decodable {
+    let index: Int
+    let id: String?
+    let type: String?
+    let function: StreamFunction?
+
+    struct StreamFunction: Decodable {
+        let name: String?
+        let arguments: String?
+    }
+}
+
+// MARK: - Error Types
+
+internal struct GrokErrorResponse: Decodable {
+    let error: GrokError
+
+    var message: String {
+        self.error.message
+    }
+
+    var code: String? {
+        self.error.code
+    }
+
+    var type: String? {
+        self.error.type
+    }
+}
+
+internal struct GrokError: Decodable {
+    let message: String
+    let type: String
+    let code: String?
+}
+
+// MARK: - Property Schema
+
+/// Type-safe property schema for Grok tool parameters
+internal struct GrokPropertySchema: Codable, Sendable {
+    let type: String
+    let description: String?
+    let `enum`: [String]?
+    let items: Box<GrokPropertySchema>?
+    let properties: [String: GrokPropertySchema]?
+    let minimum: Double?
+    let maximum: Double?
+    let pattern: String?
+    let required: [String]?
+
+    init(
+        type: String,
+        description: String? = nil,
+        enum enumValues: [String]? = nil,
+        items: GrokPropertySchema? = nil,
+        properties: [String: GrokPropertySchema]? = nil,
+        minimum: Double? = nil,
+        maximum: Double? = nil,
+        pattern: String? = nil,
+        required: [String]? = nil)
+    {
+        self.type = type
+        self.description = description
+        self.enum = enumValues
+        self.items = items.map(Box.init)
+        self.properties = properties
+        self.minimum = minimum
+        self.maximum = maximum
+        self.pattern = pattern
+        self.required = required
+    }
+
+    /// Create from a ParameterSchema
+    init(from schema: ParameterSchema) {
+        self.type = schema.type.rawValue
+        self.description = schema.description
+        self.enum = schema.enumValues
+        self.items = schema.items.map { Box(GrokPropertySchema(from: $0.value)) }
+        self.properties = schema.properties?.mapValues { GrokPropertySchema(from: $0) }
+        self.minimum = schema.minimum
+        self.maximum = schema.maximum
+        self.pattern = schema.pattern
+        self.required = nil
+    }
+}
+
+// MARK: - Extensions
+
+/// Helper to convert ToolParameters to Grok-compatible structure
+internal extension ToolParameters {
+    func toGrokParameters() -> (type: String, properties: [String: GrokPropertySchema], required: [String]) {
+        var grokProperties: [String: GrokPropertySchema] = [:]
+
+        for (key, schema) in properties {
+            grokProperties[key] = GrokPropertySchema(from: schema)
+        }
+
+        return (type: type, properties: grokProperties, required: required)
+    }
+}
\ No newline at end of file
diff --git a/Sources/Providers/Ollama/OllamaModel.swift b/Sources/Providers/Ollama/OllamaModel.swift
new file mode 100644
index 0000000..e58ffd2
--- /dev/null
+++ b/Sources/Providers/Ollama/OllamaModel.swift
@@ -0,0 +1,336 @@
+import Foundation
+
+/// Ollama model implementation conforming to ModelInterface
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public final class OllamaModel: ModelInterface, Sendable {
+    private let modelName: String
+    private let baseURL: URL
+    private let session: URLSession
+
+    public init(
+        modelName: String,
+        baseURL: URL = URL(string: "http://localhost:11434")!,
+        session: URLSession? = nil)
+    {
+        self.modelName = modelName
+        self.baseURL = baseURL
+        
+        if let session {
+            self.session = session
+        } else {
+            let config = URLSessionConfiguration.default
+            config.timeoutIntervalForRequest = 300 // 5 minutes for local models
+            config.timeoutIntervalForResource = 300
+            self.session = URLSession(configuration: config)
+        }
+    }
+
+    // MARK: - ModelInterface Implementation
+
+    public var maskedApiKey: String {
+        "local-ollama"
+    }
+
+    public func getResponse(request: ModelRequest) async throws -> ModelResponse {
+        let ollamaRequest = try convertToOllamaRequest(request, stream: false)
+        let urlRequest = try createURLRequest(endpoint: "api/chat", body: ollamaRequest)
+
+        let (data, response) = try await session.data(for: urlRequest)
+
+        guard let httpResponse = response as? HTTPURLResponse else {
+            throw TachikomaError.networkError(underlying: URLError(.badServerResponse))
+        }
+
+        if httpResponse.statusCode != 200 {
+            try handleErrorResponse(data: data, response: httpResponse)
+        }
+
+        let ollamaResponse = try JSONDecoder().decode(OllamaChatResponse.self, from: data)
+        return try self.convertFromOllamaResponse(ollamaResponse)
+    }
+
+    public func getStreamedResponse(request: ModelRequest) async throws -> AsyncThrowingStream<StreamEvent, any Error> {
+        let ollamaRequest = try convertToOllamaRequest(request, stream: true)
+        let urlRequest = try createURLRequest(endpoint: "api/chat", body: ollamaRequest)
+
+        return AsyncThrowingStream { continuation in
+            Task {
+                do {
+                    let (bytes, response) = try await session.bytes(for: urlRequest)
+
+                    guard let httpResponse = response as? HTTPURLResponse else {
+                        continuation.finish(throwing: TachikomaError.networkError(underlying: URLError(.badServerResponse)))
+                        return
+                    }
+
+                    if httpResponse.statusCode != 200 {
+                        var errorData = Data()
+                        for try await byte in bytes.prefix(1024) {
+                            errorData.append(byte)
+                        }
+                        try self.handleErrorResponse(data: errorData, response: httpResponse)
+                    }
+
+                    // Process JSON stream (one JSON object per line)
+                    for try await line in bytes.lines {
+                        if line.isEmpty { continue }
+                        
+                        if let data = line.data(using: .utf8),
+                           let chunk = try? JSONDecoder().decode(OllamaChatChunk.self, from: data) {
+                            
+                            if let events = self.processOllamaChunk(chunk) {
+                                for event in events {
+                                    continuation.yield(event)
+                                }
+                            }
+                            
+                            // Check if done
+                            if chunk.done {
+                                continuation.finish()
+                                return
+                            }
+                        }
+                    }
+
+                    continuation.finish()
+                } catch {
+                    continuation.finish(throwing: TachikomaError.streamingError(error.localizedDescription))
+                }
+            }
+        }
+    }
+
+    // MARK: - Private Methods
+
+    private func createURLRequest(endpoint: String, body: any Encodable) throws -> URLRequest {
+        let url = self.baseURL.appendingPathComponent(endpoint)
+        var request = URLRequest(url: url)
+        request.httpMethod = "POST"
+        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
+
+        let encoder = JSONEncoder()
+        encoder.outputFormatting = .sortedKeys
+
+        do {
+            request.httpBody = try encoder.encode(body)
+        } catch {
+            throw TachikomaError.configurationError("Failed to encode Ollama request: \(error.localizedDescription)")
+        }
+
+        request.timeoutInterval = 300 // 5 minutes for local models
+
+        return request
+    }
+
+    private func convertToOllamaRequest(_ request: ModelRequest, stream: Bool) throws -> OllamaChatRequest {
+        // Convert messages
+        let messages = try request.messages.compactMap { message -> OllamaMessage? in
+            switch message {
+            case let .system(_, content):
+                return OllamaMessage(role: "system", content: content, images: nil)
+
+            case let .user(_, content):
+                return try convertUserMessage(content)
+
+            case let .assistant(_, content, _):
+                return convertAssistantMessage(content)
+
+            case let .tool(_, _, content):
+                // Ollama handles tool results differently - might need adaptation
+                return OllamaMessage(role: "user", content: "Tool result: \(content)", images: nil)
+
+            case .reasoning:
+                // Skip reasoning messages for Ollama
+                return nil
+            }
+        }
+
+        // Convert tools (if supported by the model)
+        let tools = request.tools?.map { toolDef -> OllamaTool in
+            OllamaTool(
+                type: "function",
+                function: OllamaFunction(
+                    name: toolDef.function.name,
+                    description: toolDef.function.description,
+                    parameters: convertToolParameters(toolDef.function.parameters)))
+        }
+
+        return OllamaChatRequest(
+            model: self.modelName,
+            messages: messages,
+            tools: tools,
+            stream: stream,
+            options: OllamaOptions(
+                temperature: request.settings.temperature,
+                topP: request.settings.topP,
+                stop: request.settings.stopSequences))
+    }
+
+    private func convertUserMessage(_ content: MessageContent) throws -> OllamaMessage {
+        switch content {
+        case let .text(text):
+            return OllamaMessage(role: "user", content: text, images: nil)
+
+        case let .image(imageContent):
+            // Ollama supports base64 images
+            if let base64 = imageContent.base64 {
+                return OllamaMessage(role: "user", content: "", images: [base64])
+            } else if imageContent.url != nil {
+                throw TachikomaError.invalidRequest("Image URLs not supported in Ollama - please provide base64 data")
+            } else {
+                throw TachikomaError.invalidRequest("No image data provided")
+            }
+
+        case let .multimodal(parts):
+            var text = ""
+            var images: [String] = []
+            
+            for part in parts {
+                if let partText = part.text {
+                    text += partText
+                } else if let image = part.imageUrl {
+                    if let base64 = image.base64 {
+                        images.append(base64)
+                    } else if image.url != nil {
+                        throw TachikomaError.invalidRequest("Image URLs not supported in Ollama - please provide base64 data")
+                    }
+                }
+            }
+            
+            return OllamaMessage(role: "user", content: text, images: images.isEmpty ? nil : images)
+
+        case .file:
+            throw TachikomaError.invalidRequest("File content not supported in Ollama API")
+
+        case let .audio(audioContent):
+            // Ollama doesn't support native audio, use transcript if available
+            if let transcript = audioContent.transcript {
+                var text = transcript
+                if let duration = audioContent.duration {
+                    text = "[Audio transcript, duration: \(Int(duration))s] \(transcript)"
+                } else {
+                    text = "[Audio transcript] \(transcript)"
+                }
+                return OllamaMessage(role: "user", content: text, images: nil)
+            } else {
+                throw TachikomaError.invalidRequest("Audio content must be transcribed before sending to Ollama")
+            }
+        }
+    }
+
+    private func convertAssistantMessage(_ content: [AssistantContent]) -> OllamaMessage {
+        var text = ""
+        
+        for item in content {
+            switch item {
+            case let .outputText(outputText):
+                text += outputText
+            case let .refusal(refusal):
+                text += refusal
+            case let .toolCall(toolCall):
+                // Convert tool call to text representation for now
+                text += "\n[Tool Call: \(toolCall.function.name)(\(toolCall.function.arguments))]"
+            }
+        }
+        
+        return OllamaMessage(role: "assistant", content: text, images: nil)
+    }
+
+    private func convertToolParameters(_ params: ToolParameters) -> [String: Any] {
+        var properties: [String: Any] = [:]
+        
+        for (key, schema) in params.properties {
+            properties[key] = convertParameterSchema(schema)
+        }
+        
+        return [
+            "type": params.type,
+            "properties": properties,
+            "required": params.required
+        ]
+    }
+
+    private func convertParameterSchema(_ schema: ParameterSchema) -> [String: Any] {
+        var result: [String: Any] = [
+            "type": schema.type.rawValue
+        ]
+        
+        if let description = schema.description {
+            result["description"] = description
+        }
+        
+        if let enumValues = schema.enumValues {
+            result["enum"] = enumValues
+        }
+        
+        return result
+    }
+
+    private func convertFromOllamaResponse(_ response: OllamaChatResponse) throws -> ModelResponse {
+        let content: [AssistantContent] = [.outputText(response.message.content)]
+        
+        // Ollama doesn't provide detailed usage info in the same format
+        let usage = Usage(
+            promptTokens: 0, // Not provided by Ollama
+            completionTokens: 0, // Not provided by Ollama
+            totalTokens: 0, // Not provided by Ollama
+            promptTokensDetails: nil,
+            completionTokensDetails: nil)
+
+        return ModelResponse(
+            id: UUID().uuidString, // Ollama doesn't provide response IDs
+            model: response.model,
+            content: content,
+            usage: usage,
+            flagged: false,
+            finishReason: response.done ? .stop : nil)
+    }
+
+    private func processOllamaChunk(_ chunk: OllamaChatChunk) -> [StreamEvent]? {
+        var events: [StreamEvent] = []
+
+        // First chunk with model info
+        if !chunk.model.isEmpty && events.isEmpty {
+            events.append(.responseStarted(StreamResponseStarted(
+                id: UUID().uuidString,
+                model: chunk.model,
+                systemFingerprint: nil)))
+        }
+
+        // Text content
+        if let content = chunk.message?.content, !content.isEmpty {
+            events.append(.textDelta(StreamTextDelta(delta: content, index: 0)))
+        }
+
+        // Done
+        if chunk.done {
+            events.append(.responseCompleted(StreamResponseCompleted(
+                id: UUID().uuidString,
+                usage: nil,
+                finishReason: .stop)))
+        }
+
+        return events.isEmpty ? nil : events
+    }
+
+    private func handleErrorResponse(data: Data, response: HTTPURLResponse) throws {
+        // Try to decode Ollama error format
+        if let errorText = String(data: data, encoding: .utf8) {
+            let message = errorText.isEmpty ? "HTTP \(response.statusCode)" : errorText
+            
+            switch response.statusCode {
+            case 400:
+                throw TachikomaError.invalidRequest(message)
+            case 404:
+                throw TachikomaError.modelNotFound(self.modelName)
+            case 500...599:
+                throw TachikomaError.modelOverloaded
+            default:
+                throw TachikomaError.apiError(message: message)
+            }
+        } else {
+            throw TachikomaError.apiError(message: "HTTP \(response.statusCode)")
+        }
+    }
+}
+
diff --git a/Sources/Providers/Ollama/OllamaTypes.swift b/Sources/Providers/Ollama/OllamaTypes.swift
new file mode 100644
index 0000000..c64799f
--- /dev/null
+++ b/Sources/Providers/Ollama/OllamaTypes.swift
@@ -0,0 +1,69 @@
+import Foundation
+
+// MARK: - Ollama Request Types
+
+internal struct OllamaChatRequest: Encodable {
+    let model: String
+    let messages: [OllamaMessage]
+    let tools: [OllamaTool]?
+    let stream: Bool
+    let options: OllamaOptions?
+}
+
+internal struct OllamaMessage: Codable {
+    let role: String
+    let content: String
+    let images: [String]?
+}
+
+internal struct OllamaTool: Encodable {
+    let type: String
+    let function: OllamaFunction
+}
+
+internal struct OllamaFunction: Encodable {
+    let name: String
+    let description: String
+    let parameters: [String: Any]
+    
+    enum CodingKeys: String, CodingKey {
+        case name, description, parameters
+    }
+    
+    func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(name, forKey: .name)
+        try container.encode(description, forKey: .description)
+        
+        // Encode parameters as JSON
+        let data = try JSONSerialization.data(withJSONObject: parameters)
+        let jsonString = String(data: data, encoding: .utf8) ?? "{}"
+        try container.encode(jsonString, forKey: .parameters)
+    }
+}
+
+internal struct OllamaOptions: Encodable {
+    let temperature: Double?
+    let topP: Double?
+    let stop: [String]?
+    
+    enum CodingKeys: String, CodingKey {
+        case temperature
+        case topP = "top_p"
+        case stop
+    }
+}
+
+// MARK: - Ollama Response Types
+
+internal struct OllamaChatResponse: Decodable {
+    let model: String
+    let message: OllamaMessage
+    let done: Bool
+}
+
+internal struct OllamaChatChunk: Decodable {
+    let model: String
+    let message: OllamaMessage?
+    let done: Bool
+}
\ No newline at end of file
diff --git a/Sources/Providers/OpenAI/OpenAIModel.swift b/Sources/Providers/OpenAI/OpenAIModel.swift
new file mode 100644
index 0000000..8abd840
--- /dev/null
+++ b/Sources/Providers/OpenAI/OpenAIModel.swift
@@ -0,0 +1,516 @@
+import Foundation
+
+/// OpenAI model implementation conforming to ModelInterface
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public final class OpenAIModel: ModelInterface, Sendable {
+    private let apiKey: String
+    private let baseURL: URL
+    private let session: URLSession
+    private let organizationId: String?
+    private let customHeaders: [String: String]?
+    private let customModelName: String?
+
+    public init(
+        apiKey: String,
+        baseURL: URL = URL(string: "https://api.openai.com/v1")!,
+        organizationId: String? = nil,
+        modelName: String? = nil,
+        headers: [String: String]? = nil,
+        session: URLSession? = nil)
+    {
+        self.apiKey = apiKey
+        self.baseURL = baseURL
+        self.organizationId = organizationId
+        self.customHeaders = headers
+        self.customModelName = modelName
+        
+        if let session {
+            self.session = session
+        } else {
+            let config = URLSessionConfiguration.default
+            config.timeoutIntervalForRequest = 600 // 10 minutes for o3 models
+            config.timeoutIntervalForResource = 600
+            self.session = URLSession(configuration: config)
+        }
+    }
+
+    // MARK: - ModelInterface Implementation
+
+    public var maskedApiKey: String {
+        guard self.apiKey.count > 8 else { return "***" }
+        let start = self.apiKey.prefix(6)
+        let end = self.apiKey.suffix(2)
+        return "\(start)...\(end)"
+    }
+
+    public func getResponse(request: ModelRequest) async throws -> ModelResponse {
+        let openAIRequest = try convertToOpenAIRequest(request, stream: false)
+        let endpoint = getEndpointForModel(request.settings.modelName)
+        let urlRequest = try createURLRequest(endpoint: endpoint, body: openAIRequest)
+
+        let (data, response) = try await session.data(for: urlRequest)
+
+        guard let httpResponse = response as? HTTPURLResponse else {
+            throw TachikomaError.networkError(underlying: URLError(.badServerResponse))
+        }
+
+        if httpResponse.statusCode != 200 {
+            try handleErrorResponse(data: data, response: httpResponse)
+        }
+
+        do {
+            let openAIResponse = try JSONDecoder().decode(OpenAIResponse.self, from: data)
+            return try convertFromOpenAIResponse(openAIResponse)
+        } catch {
+            throw TachikomaError.decodingError(underlying: error)
+        }
+    }
+
+    public func getStreamedResponse(request: ModelRequest) async throws -> AsyncThrowingStream<StreamEvent, any Error> {
+        let openAIRequest = try convertToOpenAIRequest(request, stream: true)
+        let endpoint = getEndpointForModel(request.settings.modelName)
+        let urlRequest = try createURLRequest(endpoint: endpoint, body: openAIRequest)
+
+        return AsyncThrowingStream { continuation in
+            Task {
+                do {
+                    let (bytes, response) = try await session.bytes(for: urlRequest)
+
+                    guard let httpResponse = response as? HTTPURLResponse else {
+                        continuation.finish(throwing: TachikomaError.networkError(underlying: URLError(.badServerResponse)))
+                        return
+                    }
+
+                    if httpResponse.statusCode != 200 {
+                        var errorData = Data()
+                        for try await byte in bytes.prefix(1024) {
+                            errorData.append(byte)
+                        }
+                        try self.handleErrorResponse(data: errorData, response: httpResponse)
+                    }
+
+                    // Process SSE stream
+                    for try await line in bytes.lines {
+                        if line.hasPrefix("data: ") {
+                            let data = String(line.dropFirst(6))
+
+                            if data == "[DONE]" {
+                                continuation.finish()
+                                return
+                            }
+
+                            if let chunkData = data.data(using: .utf8),
+                               let chunk = try? JSONDecoder().decode(OpenAIStreamChunk.self, from: chunkData) {
+                                if let events = processStreamChunk(chunk) {
+                                    for event in events {
+                                        continuation.yield(event)
+                                    }
+                                }
+                            }
+                        }
+                    }
+
+                    continuation.finish()
+                } catch {
+                    continuation.finish(throwing: TachikomaError.streamingError(error.localizedDescription))
+                }
+            }
+        }
+    }
+
+    // MARK: - Private Methods
+
+    private func getEndpointForModel(_ modelName: String) -> String {
+        // Use Responses API for o3/o4 models, Chat Completions for others
+        if modelName.hasPrefix("o3") || modelName.hasPrefix("o4") {
+            return "responses"
+        } else {
+            return "chat/completions"
+        }
+    }
+
+    private func createURLRequest(endpoint: String, body: any Encodable) throws -> URLRequest {
+        let url = self.baseURL.appendingPathComponent(endpoint)
+        var request = URLRequest(url: url)
+        request.httpMethod = "POST"
+        request.setValue("Bearer \(self.apiKey)", forHTTPHeaderField: "Authorization")
+        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
+
+        if let orgId = organizationId {
+            request.setValue(orgId, forHTTPHeaderField: "OpenAI-Organization")
+        }
+        
+        customHeaders?.forEach { key, value in
+            request.setValue(value, forHTTPHeaderField: key)
+        }
+
+        let encoder = JSONEncoder()
+        encoder.outputFormatting = .sortedKeys
+
+        do {
+            request.httpBody = try encoder.encode(body)
+        } catch {
+            throw TachikomaError.configurationError("Failed to encode OpenAI request: \(error.localizedDescription)")
+        }
+
+        // Set timeout for different API types
+        if endpoint == "responses" {
+            request.timeoutInterval = 600 // 10 minutes for o3 models
+        } else {
+            request.timeoutInterval = 120 // 2 minutes for other models
+        }
+
+        return request
+    }
+
+    private func convertToOpenAIRequest(_ request: ModelRequest, stream: Bool) throws -> any Encodable {
+        let modelName = customModelName ?? request.settings.modelName
+        
+        if modelName.hasPrefix("o3") || modelName.hasPrefix("o4") {
+            return try convertToResponsesRequest(request, stream: stream)
+        } else {
+            return try convertToChatRequest(request, stream: stream)
+        }
+    }
+
+    private func convertToChatRequest(_ request: ModelRequest, stream: Bool) throws -> OpenAIChatRequest {
+        let messages = try request.messages.map { message -> OpenAIMessage in
+            switch message {
+            case let .system(_, content):
+                return OpenAIMessage(role: "system", content: .string(content))
+            case let .user(_, content):
+                return try convertUserMessage(content)
+            case let .assistant(_, content, _):
+                return try convertAssistantMessage(content)
+            case let .tool(_, toolCallId, content):
+                return OpenAIMessage(role: "tool", content: .string(content), toolCallId: toolCallId)
+            case .reasoning:
+                throw TachikomaError.invalidRequest("Reasoning messages not supported in Chat Completions API")
+            }
+        }
+
+        let tools = request.tools?.map { tool in
+            OpenAITool(
+                type: "function",
+                function: OpenAIFunction(
+                    name: tool.function.name,
+                    description: tool.function.description,
+                    parameters: convertToolParameters(tool.function.parameters)))
+        }
+
+        return OpenAIChatRequest(
+            model: customModelName ?? request.settings.modelName,
+            messages: messages,
+            tools: tools,
+            toolChoice: convertToolChoice(request.settings.toolChoice),
+            temperature: request.settings.temperature,
+            topP: request.settings.topP,
+            stream: stream,
+            maxTokens: request.settings.maxTokens)
+    }
+
+    private func convertToResponsesRequest(_ request: ModelRequest, stream: Bool) throws -> OpenAIResponsesRequest {
+        let messages = try request.messages.compactMap { message -> OpenAIMessage? in
+            switch message {
+            case let .system(_, content):
+                return OpenAIMessage(role: "system", content: .string(content))
+            case let .user(_, content):
+                return try convertUserMessage(content)
+            case let .assistant(_, content, _):
+                return try convertAssistantMessage(content)
+            case let .tool(_, _, content):
+                return OpenAIMessage(role: "user", content: .string(content))
+            case .reasoning:
+                return nil // Skip reasoning messages
+            }
+        }
+
+        let tools = request.tools?.map { tool in
+            OpenAIResponsesTool(
+                type: "function",
+                name: tool.function.name,
+                description: tool.function.description,
+                parameters: convertToolParameters(tool.function.parameters))
+        }
+
+        let modelName = customModelName ?? request.settings.modelName
+        
+        return OpenAIResponsesRequest(
+            model: modelName,
+            input: messages,
+            tools: tools,
+            toolChoice: convertToolChoice(request.settings.toolChoice),
+            temperature: nil, // o3/o4 models don't support temperature
+            topP: request.settings.topP,
+            stream: stream,
+            maxOutputTokens: request.settings.maxTokens ?? 65536,
+            reasoning: (modelName.hasPrefix("o3") || modelName.hasPrefix("o4")) ? 
+                OpenAIReasoning(
+                    effort: request.settings.additionalParameters?.string("reasoning_effort") ?? "medium",
+                    summary: "detailed") : nil)
+    }
+
+    private func convertUserMessage(_ content: MessageContent) throws -> OpenAIMessage {
+        switch content {
+        case let .text(text):
+            return OpenAIMessage(role: "user", content: .string(text))
+        case let .image(imageContent):
+            var parts: [OpenAIMessageContentPart] = []
+            
+            if let url = imageContent.url {
+                parts.append(OpenAIMessageContentPart(
+                    type: "image_url",
+                    text: nil,
+                    imageUrl: OpenAIImageUrl(url: url, detail: imageContent.detail?.rawValue)))
+            } else if let base64 = imageContent.base64 {
+                parts.append(OpenAIMessageContentPart(
+                    type: "image_url", 
+                    text: nil,
+                    imageUrl: OpenAIImageUrl(url: "data:image/jpeg;base64,\(base64)", detail: imageContent.detail?.rawValue)))
+            }
+            
+            return OpenAIMessage(role: "user", content: .array(parts))
+        case let .multimodal(parts):
+            let contentParts = parts.compactMap { part -> OpenAIMessageContentPart? in
+                if let text = part.text {
+                    return OpenAIMessageContentPart(type: "text", text: text, imageUrl: nil)
+                } else if let image = part.imageUrl {
+                    if let url = image.url {
+                        return OpenAIMessageContentPart(
+                            type: "image_url",
+                            text: nil,
+                            imageUrl: OpenAIImageUrl(url: url, detail: image.detail?.rawValue))
+                    } else if let base64 = image.base64 {
+                        return OpenAIMessageContentPart(
+                            type: "image_url",
+                            text: nil,
+                            imageUrl: OpenAIImageUrl(url: "data:image/jpeg;base64,\(base64)", detail: image.detail?.rawValue))
+                    }
+                }
+                return nil
+            }
+            return OpenAIMessage(role: "user", content: .array(contentParts))
+        case .file:
+            throw TachikomaError.invalidRequest("File content not supported in OpenAI API")
+        case let .audio(audioContent):
+            if let transcript = audioContent.transcript {
+                var text = transcript
+                if let duration = audioContent.duration {
+                    text = "[Audio transcript, duration: \(Int(duration))s] \(transcript)"
+                } else {
+                    text = "[Audio transcript] \(transcript)"
+                }
+                return OpenAIMessage(role: "user", content: .string(text))
+            } else {
+                throw TachikomaError.invalidRequest("Audio content must be transcribed before sending to OpenAI")
+            }
+        }
+    }
+
+    private func convertAssistantMessage(_ content: [AssistantContent]) throws -> OpenAIMessage {
+        var textContent = ""
+        var toolCalls: [OpenAIToolCall] = []
+
+        for item in content {
+            switch item {
+            case let .outputText(text):
+                textContent += text
+            case let .refusal(refusal):
+                return OpenAIMessage(role: "assistant", content: .string(refusal))
+            case let .toolCall(toolCall):
+                toolCalls.append(OpenAIToolCall(
+                    id: toolCall.id,
+                    type: "function",
+                    function: OpenAIFunction(
+                        name: toolCall.function.name,
+                        description: nil,
+                        parameters: nil,
+                        arguments: toolCall.function.arguments)))
+            }
+        }
+
+        if !toolCalls.isEmpty {
+            return OpenAIMessage(role: "assistant", content: .string(textContent), toolCalls: toolCalls)
+        } else {
+            return OpenAIMessage(role: "assistant", content: .string(textContent))
+        }
+    }
+
+    private func convertToolParameters(_ params: ToolParameters) -> [String: Any] {
+        var properties: [String: Any] = [:]
+        
+        for (key, schema) in params.properties {
+            properties[key] = convertParameterSchema(schema)
+        }
+        
+        return [
+            "type": params.type,
+            "properties": properties,
+            "required": params.required,
+            "additionalProperties": params.additionalProperties
+        ]
+    }
+
+    private func convertParameterSchema(_ schema: ParameterSchema) -> [String: Any] {
+        var result: [String: Any] = [
+            "type": schema.type.rawValue
+        ]
+        
+        if let description = schema.description {
+            result["description"] = description
+        }
+        
+        if let enumValues = schema.enumValues {
+            result["enum"] = enumValues
+        }
+        
+        if let minimum = schema.minimum {
+            result["minimum"] = minimum
+        }
+        
+        if let maximum = schema.maximum {
+            result["maximum"] = maximum
+        }
+        
+        if let pattern = schema.pattern {
+            result["pattern"] = pattern
+        }
+        
+        if let items = schema.items {
+            result["items"] = convertParameterSchema(items.value)
+        }
+        
+        if let properties = schema.properties {
+            result["properties"] = properties.mapValues { convertParameterSchema($0) }
+        }
+        
+        return result
+    }
+
+    private func convertToolChoice(_ toolChoice: ToolChoice?) -> String? {
+        guard let toolChoice else { return nil }
+
+        switch toolChoice {
+        case .auto:
+            return "auto"
+        case .none:
+            return "none"
+        case .required:
+            return "required"
+        case let .specific(toolName):
+            return toolName
+        }
+    }
+
+    private func convertFromOpenAIResponse(_ response: OpenAIResponse) throws -> ModelResponse {
+        guard let choice = response.choices.first else {
+            throw TachikomaError.apiError(message: "No choices in OpenAI response")
+        }
+
+        var content: [AssistantContent] = []
+
+        if let messageContent = choice.message.content {
+            switch messageContent {
+            case let .string(text):
+                content.append(.outputText(text))
+            case let .array(parts):
+                // Extract text from content parts
+                let text = parts.compactMap { $0.text }.joined()
+                if !text.isEmpty {
+                    content.append(.outputText(text))
+                }
+            }
+        }
+
+        if let toolCalls = choice.message.toolCalls {
+            for toolCall in toolCalls {
+                content.append(.toolCall(ToolCallItem(
+                    id: toolCall.id,
+                    type: .function,
+                    function: FunctionCall(
+                        name: toolCall.function.name,
+                        arguments: toolCall.function.arguments ?? ""))))
+            }
+        }
+
+        let usage = response.usage.map { usage in
+            Usage(
+                promptTokens: usage.promptTokens,
+                completionTokens: usage.completionTokens,
+                totalTokens: usage.totalTokens,
+                promptTokensDetails: nil,
+                completionTokensDetails: nil)
+        }
+
+        return ModelResponse(
+            id: response.id,
+            model: response.model,
+            content: content,
+            usage: usage,
+            flagged: false,
+            finishReason: convertFinishReason(choice.finishReason))
+    }
+
+    private func convertFinishReason(_ reason: String?) -> FinishReason? {
+        guard let reason else { return nil }
+        return FinishReason(rawValue: reason)
+    }
+
+    private func processStreamChunk(_ chunk: OpenAIStreamChunk) -> [StreamEvent]? {
+        var events: [StreamEvent] = []
+
+        if let delta = chunk.choices?.first?.delta {
+            if let content = delta.content {
+                events.append(.textDelta(StreamTextDelta(delta: content, index: 0)))
+            }
+
+            if let toolCalls = delta.toolCalls {
+                for toolCall in toolCalls {
+                    if let id = toolCall.id, let function = toolCall.function {
+                        events.append(.toolCallDelta(StreamToolCallDelta(
+                            id: id,
+                            index: toolCall.index ?? 0,
+                            function: FunctionCallDelta(
+                                name: function.name,
+                                arguments: function.arguments))))
+                    }
+                }
+            }
+        }
+
+        if let finishReason = chunk.choices?.first?.finishReason {
+            events.append(.responseCompleted(StreamResponseCompleted(
+                id: chunk.id ?? "",
+                usage: nil,
+                finishReason: convertFinishReason(finishReason))))
+        }
+
+        return events.isEmpty ? nil : events
+    }
+
+    private func handleErrorResponse(data: Data, response: HTTPURLResponse) throws {
+        if let errorResponse = try? JSONDecoder().decode(OpenAIErrorResponse.self, from: data) {
+            let message = errorResponse.error.message
+            let code = errorResponse.error.code
+            
+            switch response.statusCode {
+            case 401:
+                throw TachikomaError.authenticationFailed
+            case 429:
+                throw TachikomaError.rateLimited
+            case 400:
+                if message.contains("context_length_exceeded") {
+                    throw TachikomaError.contextLengthExceeded
+                } else {
+                    throw TachikomaError.invalidRequest(message)
+                }
+            case 500...599:
+                throw TachikomaError.modelOverloaded
+            default:
+                throw TachikomaError.apiError(message: message, code: code)
+            }
+        } else {
+            throw TachikomaError.apiError(message: "HTTP \(response.statusCode)", code: "\(response.statusCode)")
+        }
+    }
+}
\ No newline at end of file
diff --git a/Sources/Providers/OpenAI/OpenAITypes.swift b/Sources/Providers/OpenAI/OpenAITypes.swift
new file mode 100644
index 0000000..d44ecf6
--- /dev/null
+++ b/Sources/Providers/OpenAI/OpenAITypes.swift
@@ -0,0 +1,481 @@
+import Foundation
+
+// MARK: - Helper Types
+
+/// Sendable wrapper for Any values
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnySendable: Codable, @unchecked Sendable {
+    public let value: Any
+    
+    public init(_ value: Any) {
+        self.value = value
+    }
+    
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.singleValueContainer()
+        
+        if let intValue = try? container.decode(Int.self) {
+            self.value = intValue
+        } else if let doubleValue = try? container.decode(Double.self) {
+            self.value = doubleValue
+        } else if let boolValue = try? container.decode(Bool.self) {
+            self.value = boolValue
+        } else if let stringValue = try? container.decode(String.self) {
+            self.value = stringValue
+        } else if let arrayValue = try? container.decode([AnySendable].self) {
+            self.value = arrayValue.map(\.value)
+        } else if let dictValue = try? container.decode([String: AnySendable].self) {
+            self.value = dictValue.mapValues(\.value)
+        } else {
+            self.value = NSNull()
+        }
+    }
+    
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.singleValueContainer()
+        
+        switch value {
+        case let intValue as Int:
+            try container.encode(intValue)
+        case let doubleValue as Double:
+            try container.encode(doubleValue)
+        case let boolValue as Bool:
+            try container.encode(boolValue)
+        case let stringValue as String:
+            try container.encode(stringValue)
+        case let arrayValue as [Any]:
+            try container.encode(arrayValue.map { AnySendable($0) })
+        case let dictValue as [String: Any]:
+            try container.encode(dictValue.mapValues { AnySendable($0) })
+        default:
+            try container.encodeNil()
+        }
+    }
+}
+
+// MARK: - OpenAI API Request Types
+
+/// Chat Completions API request format
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIChatRequest: Codable, Sendable {
+    public let model: String
+    public let messages: [OpenAIMessage]
+    public let tools: [OpenAITool]?
+    public let toolChoice: String?
+    public let temperature: Double?
+    public let topP: Double?
+    public let stream: Bool?
+    public let maxTokens: Int?
+
+    enum CodingKeys: String, CodingKey {
+        case model, messages, tools, temperature, stream
+        case toolChoice = "tool_choice"
+        case topP = "top_p"
+        case maxTokens = "max_tokens"
+    }
+}
+
+/// Responses API request format (for o3/o4 models)
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIResponsesRequest: Codable, Sendable {
+    public let model: String
+    public let input: [OpenAIMessage]
+    public let tools: [OpenAIResponsesTool]?
+    public let toolChoice: String?
+    public let temperature: Double?
+    public let topP: Double?
+    public let stream: Bool?
+    public let maxOutputTokens: Int?
+    public let reasoning: OpenAIReasoning?
+
+    enum CodingKeys: String, CodingKey {
+        case model, input, tools, temperature, stream, reasoning
+        case toolChoice = "tool_choice"
+        case topP = "top_p"
+        case maxOutputTokens = "max_output_tokens"
+    }
+}
+
+/// OpenAI message format
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIMessage: Codable, Sendable {
+    public let role: String
+    public let content: MessageContent?
+    public let toolCalls: [OpenAIToolCall]?
+    public let toolCallId: String?
+
+    public enum MessageContent: Codable, Sendable {
+        case string(String)
+        case array([OpenAIMessageContentPart])
+
+        public init(from decoder: any Decoder) throws {
+            let container = try decoder.singleValueContainer()
+            if let stringValue = try? container.decode(String.self) {
+                self = .string(stringValue)
+            } else if let arrayValue = try? container.decode([OpenAIMessageContentPart].self) {
+                self = .array(arrayValue)
+            } else {
+                throw DecodingError.dataCorruptedError(in: container, debugDescription: "Unable to decode message content")
+            }
+        }
+
+        public func encode(to encoder: any Encoder) throws {
+            var container = encoder.singleValueContainer()
+            switch self {
+            case let .string(value):
+                try container.encode(value)
+            case let .array(value):
+                try container.encode(value)
+            }
+        }
+    }
+
+    enum CodingKeys: String, CodingKey {
+        case role, content
+        case toolCalls = "tool_calls"
+        case toolCallId = "tool_call_id"
+    }
+
+    public init(role: String, content: MessageContent? = nil, toolCalls: [OpenAIToolCall]? = nil, toolCallId: String? = nil) {
+        self.role = role
+        self.content = content
+        self.toolCalls = toolCalls
+        self.toolCallId = toolCallId
+    }
+}
+
+/// OpenAI message content part for multimodal messages
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIMessageContentPart: Codable, Sendable {
+    public let type: String
+    public let text: String?
+    public let imageUrl: OpenAIImageUrl?
+
+    enum CodingKeys: String, CodingKey {
+        case type, text
+        case imageUrl = "image_url"
+    }
+
+    public init(type: String, text: String? = nil, imageUrl: OpenAIImageUrl? = nil) {
+        self.type = type
+        self.text = text
+        self.imageUrl = imageUrl
+    }
+}
+
+/// OpenAI image URL format
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIImageUrl: Codable, Sendable {
+    public let url: String
+    public let detail: String?
+
+    public init(url: String, detail: String? = nil) {
+        self.url = url
+        self.detail = detail
+    }
+}
+
+/// OpenAI tool definition for Chat Completions API
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAITool: Codable, Sendable {
+    public let type: String
+    public let function: OpenAIFunction
+
+    public init(type: String, function: OpenAIFunction) {
+        self.type = type
+        self.function = function
+    }
+}
+
+/// OpenAI tool definition for Responses API
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIResponsesTool: Codable, Sendable {
+    public let type: String
+    public let name: String
+    public let description: String
+    public let parameters: [String: AnySendable]
+
+    enum CodingKeys: String, CodingKey {
+        case type, name, description, parameters
+    }
+
+    public init(type: String, name: String, description: String, parameters: [String: Any]) {
+        self.type = type
+        self.name = name
+        self.description = description
+        self.parameters = parameters.mapValues { AnySendable($0) }
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        self.type = try container.decode(String.self, forKey: .type)
+        self.name = try container.decode(String.self, forKey: .name)
+        self.description = try container.decode(String.self, forKey: .description)
+        
+        // Decode parameters as generic JSON
+        let parametersContainer = try container.nestedContainer(keyedBy: AnyCodingKey.self, forKey: .parameters)
+        var parameters: [String: AnySendable] = [:]
+        for key in parametersContainer.allKeys {
+            parameters[key.stringValue] = try parametersContainer.decode(AnySendable.self, forKey: key)
+        }
+        self.parameters = parameters
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(type, forKey: .type)
+        try container.encode(name, forKey: .name)
+        try container.encode(description, forKey: .description)
+        
+        // Skip encoding parameters for now - this needs to be handled at runtime
+        try container.encodeIfPresent(nil as String?, forKey: .parameters)
+    }
+}
+
+/// OpenAI function definition
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIFunction: Codable, Sendable {
+    public let name: String
+    public let description: String?
+    public let parameters: [String: AnySendable]?
+    public let arguments: String?
+
+    enum CodingKeys: String, CodingKey {
+        case name, description, parameters, arguments
+    }
+
+    public init(name: String, description: String? = nil, parameters: [String: Any]? = nil, arguments: String? = nil) {
+        self.name = name
+        self.description = description
+        self.parameters = parameters?.mapValues { AnySendable($0) }
+        self.arguments = arguments
+    }
+
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        self.name = try container.decode(String.self, forKey: .name)
+        self.description = try container.decodeIfPresent(String.self, forKey: .description)
+        self.arguments = try container.decodeIfPresent(String.self, forKey: .arguments)
+        
+        if container.contains(.parameters) {
+            let parametersContainer = try container.nestedContainer(keyedBy: AnyCodingKey.self, forKey: .parameters)
+            var parameters: [String: AnySendable] = [:]
+            for key in parametersContainer.allKeys {
+                parameters[key.stringValue] = try parametersContainer.decode(AnySendable.self, forKey: key)
+            }
+            self.parameters = parameters
+        } else {
+            self.parameters = nil
+        }
+    }
+
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(name, forKey: .name)
+        try container.encodeIfPresent(description, forKey: .description)
+        try container.encodeIfPresent(arguments, forKey: .arguments)
+        
+        if let parameters = parameters {
+            // Convert AnySendable parameters to AnyCodable for encoding
+            let codableParams = parameters.mapValues { AnyCodable($0.value) }
+            try container.encode(codableParams, forKey: .parameters)
+        }
+    }
+}
+
+/// OpenAI tool call
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIToolCall: Codable, Sendable {
+    public let id: String
+    public let type: String
+    public let function: OpenAIFunction
+
+    public init(id: String, type: String, function: OpenAIFunction) {
+        self.id = id
+        self.type = type
+        self.function = function
+    }
+}
+
+/// OpenAI reasoning configuration for o3/o4 models
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIReasoning: Codable, Sendable {
+    public let effort: String
+    public let summary: String
+
+    public init(effort: String, summary: String) {
+        self.effort = effort
+        self.summary = summary
+    }
+}
+
+// MARK: - OpenAI Response Types
+
+/// OpenAI Chat Completions response
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIResponse: Codable, Sendable {
+    public let id: String
+    public let model: String
+    public let choices: [OpenAIChoice]
+    public let usage: OpenAIUsage?
+}
+
+/// OpenAI response choice
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIChoice: Codable, Sendable {
+    public let message: OpenAIMessage
+    public let finishReason: String?
+
+    enum CodingKeys: String, CodingKey {
+        case message
+        case finishReason = "finish_reason"
+    }
+}
+
+/// OpenAI usage information
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIUsage: Codable, Sendable {
+    public let promptTokens: Int
+    public let completionTokens: Int
+    public let totalTokens: Int
+
+    enum CodingKeys: String, CodingKey {
+        case promptTokens = "prompt_tokens"
+        case completionTokens = "completion_tokens"
+        case totalTokens = "total_tokens"
+    }
+}
+
+// MARK: - OpenAI Streaming Types
+
+/// OpenAI streaming chunk
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIStreamChunk: Codable, Sendable {
+    public let id: String?
+    public let model: String?
+    public let choices: [OpenAIStreamChoice]?
+}
+
+/// OpenAI streaming choice
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIStreamChoice: Codable, Sendable {
+    public let delta: OpenAIStreamDelta?
+    public let finishReason: String?
+
+    enum CodingKeys: String, CodingKey {
+        case delta
+        case finishReason = "finish_reason"
+    }
+}
+
+/// OpenAI streaming delta
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIStreamDelta: Codable, Sendable {
+    public let content: String?
+    public let toolCalls: [OpenAIStreamToolCall]?
+
+    enum CodingKeys: String, CodingKey {
+        case content
+        case toolCalls = "tool_calls"
+    }
+}
+
+/// OpenAI streaming tool call
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIStreamToolCall: Codable, Sendable {
+    public let id: String?
+    public let type: String?
+    public let index: Int?
+    public let function: OpenAIStreamFunction?
+}
+
+/// OpenAI streaming function
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIStreamFunction: Codable, Sendable {
+    public let name: String?
+    public let arguments: String?
+}
+
+// MARK: - Error Types
+
+/// OpenAI error response
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIErrorResponse: Codable, Sendable {
+    public let error: OpenAIError
+}
+
+/// OpenAI error details
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct OpenAIError: Codable, Sendable {
+    public let message: String
+    public let type: String?
+    public let code: String?
+}
+
+// MARK: - Helper Types
+
+/// Dynamic coding key for JSON encoding/decoding
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+struct AnyCodingKey: CodingKey {
+    var stringValue: String
+    var intValue: Int?
+
+    init?(stringValue: String) {
+        self.stringValue = stringValue
+        self.intValue = nil
+    }
+
+    init?(intValue: Int) {
+        self.stringValue = "\(intValue)"
+        self.intValue = intValue
+    }
+}
+
+/// Wrapper for any codable value
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public struct AnyCodable: Codable, @unchecked Sendable {
+    public let value: Any
+    
+    public init(_ value: Any) {
+        self.value = value
+    }
+    
+    public func encode(to encoder: any Encoder) throws {
+        var container = encoder.singleValueContainer()
+        
+        if let intValue = value as? Int {
+            try container.encode(intValue)
+        } else if let doubleValue = value as? Double {
+            try container.encode(doubleValue)
+        } else if let stringValue = value as? String {
+            try container.encode(stringValue)
+        } else if let boolValue = value as? Bool {
+            try container.encode(boolValue)
+        } else {
+            let data = try JSONSerialization.data(withJSONObject: value)
+            let str = String(data: data, encoding: .utf8) ?? "{}"
+            try container.encode(str)
+        }
+    }
+    
+    public init(from decoder: any Decoder) throws {
+        let container = try decoder.singleValueContainer()
+        
+        if let intValue = try? container.decode(Int.self) {
+            value = intValue
+        } else if let doubleValue = try? container.decode(Double.self) {
+            value = doubleValue
+        } else if let stringValue = try? container.decode(String.self) {
+            value = stringValue
+        } else if let boolValue = try? container.decode(Bool.self) {
+            value = boolValue
+        } else {
+            value = NSNull()
+        }
+    }
+}
+
+// MARK: - Container Extensions
+
+// Note: Complex Any encoding/decoding extensions removed
+// We use AnySendable for type-safe handling of dynamic JSON data
\ No newline at end of file
diff --git a/Sources/Tachikoma.swift b/Sources/Tachikoma.swift
new file mode 100644
index 0000000..5d00166
--- /dev/null
+++ b/Sources/Tachikoma.swift
@@ -0,0 +1,87 @@
+import Foundation
+@_exported import Logging
+
+/// Tachikoma - A comprehensive Swift package for AI model integration
+///
+/// Tachikoma provides a unified interface for connecting to various AI providers
+/// including OpenAI, Anthropic, Grok (xAI), Ollama, and custom endpoints.
+/// It supports both streaming and non-streaming responses, tool calling,
+/// multimodal inputs, and configuration management.
+///
+/// Named after the AI entity from Ghost in the Shell, Tachikoma embodies
+/// the cyberpunk aesthetic of autonomous AI systems.
+@available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
+public final class Tachikoma: @unchecked Sendable {
+    public static let shared = Tachikoma()
+    
+    private let logger: Logger
+    
+    private init() {
+        self.logger = Logger(label: "build.tachikoma")
+    }
+    
+    /// Get the shared logger instance
+    public var log: Logger {
+        logger
+    }
+    
+    /// Get a model instance for the specified model name
+    /// - Parameter modelName: The model identifier (e.g., "gpt-4.1", "claude-opus-4", "provider-id/model-name")
+    /// - Returns: A model instance conforming to ModelInterface
+    /// - Throws: TachikomaError if the model is not available or configuration is invalid
+    public func getModel(_ modelName: String) async throws -> any ModelInterface {
+        return try await ModelProvider.shared.getModel(modelName: modelName)
+    }
+    
+    /// Configure OpenAI provider with specific settings
+    /// - Parameter configuration: OpenAI configuration
+    public func configureOpenAI(_ configuration: ProviderConfiguration.OpenAI) async {
+        await ModelProvider.shared.configureOpenAI(configuration)
+    }
+    
+    /// Configure Anthropic provider with specific settings
+    /// - Parameter configuration: Anthropic configuration
+    public func configureAnthropic(_ configuration: ProviderConfiguration.Anthropic) async {
+        await ModelProvider.shared.configureAnthropic(configuration)
+    }
+    
+    /// Configure Ollama provider with specific settings
+    /// - Parameter configuration: Ollama configuration
+    public func configureOllama(_ configuration: ProviderConfiguration.Ollama) async {
+        await ModelProvider.shared.configureOllama(configuration)
+    }
+    
+    /// Configure Grok provider with specific settings
+    /// - Parameter configuration: Grok configuration
+    public func configureGrok(_ configuration: ProviderConfiguration.Grok) async {
+        await ModelProvider.shared.configureGrok(configuration)
+    }
+    
+    /// Set up all providers from environment variables
+    /// - Throws: TachikomaError if setup fails
+    public func setupFromEnvironment() async throws {
+        try await ModelProvider.shared.setupFromEnvironment()
+    }
+    
+    /// List all available models from configured providers
+    /// - Returns: Array of available model identifiers
+    public func availableModels() async -> [String] {
+        return await ModelProvider.shared.listModels()
+    }
+    
+    /// Clear all cached model instances
+    public func clearModelCache() async {
+        await ModelProvider.shared.clearCache()
+    }
+    
+    /// Register a custom model factory
+    /// - Parameters:
+    ///   - modelName: The model name to register
+    ///   - factory: Factory closure that creates the model instance
+    public func registerModel(
+        name modelName: String,
+        factory: @escaping @Sendable () throws -> any ModelInterface) async
+    {
+        await ModelProvider.shared.register(modelName: modelName, factory: factory)
+    }
+}
\ No newline at end of file
diff --git a/Tests/TachikomaTests/AnthropicModelTests.swift b/Tests/TachikomaTests/AnthropicModelTests.swift
new file mode 100644
index 0000000..8c34cd7
--- /dev/null
+++ b/Tests/TachikomaTests/AnthropicModelTests.swift
@@ -0,0 +1,373 @@
+import Foundation
+import Testing
+@testable import Tachikoma
+
+@Suite("Anthropic Model Tests")
+struct AnthropicModelTests {
+    @Test("Model initialization")
+    func modelInitialization() async throws {
+        let model = AnthropicModel(
+            apiKey: "sk-ant-test-key-123456789",
+            modelName: "claude-opus-4-20250514")
+
+        #expect(model.maskedApiKey == "sk-ant...789")
+    }
+
+    @Test("API key masking")
+    func apiKeyMasking() async throws {
+        // Test short key
+        let shortModel = AnthropicModel(apiKey: "short")
+        #expect(shortModel.maskedApiKey == "***")
+
+        // Test normal key
+        let normalModel = AnthropicModel(apiKey: "sk-ant-api-key-1234567890abcdefghijklmnopqrstuvwxyz")
+        #expect(normalModel.maskedApiKey == "sk-ant...xyz")
+    }
+
+    @Test("System message extraction")
+    func systemMessageExtraction() async throws {
+        let model = AnthropicModel(apiKey: "test-key")
+
+        let request = ModelRequest(
+            messages: [
+                Message.system(content: "You are a helpful assistant."),
+                Message.user(content: .text("Hello!")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        // System messages should be properly handled
+        #expect(request.messages.first?.type == .system)
+    }
+
+    @Test("Tool conversion")
+    func toolConversion() async throws {
+        let model = AnthropicModel(apiKey: "test-key")
+
+        let toolDef = ToolDefinition(
+            function: FunctionDefinition(
+                name: "get_weather",
+                description: "Get the current weather",
+                parameters: ToolParameters(
+                    properties: ["location": ParameterSchema(type: .string, description: "The location")],
+                    required: ["location"])))
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("What's the weather?")),
+            ],
+            tools: [toolDef],
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        #expect(request.tools?.count == 1)
+        #expect(request.tools?.first?.function.name == "get_weather")
+
+        // Test that the model can process the request (will fail at network level)
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Image content handling")
+    func imageContentHandling() async throws {
+        let model = AnthropicModel(apiKey: "test-key", modelName: "claude-opus-4-20250514")
+
+        let imageData = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNkYPhfDwAChwGA60e6kgAAAABJRU5ErkJggg=="
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .multimodal([
+                    MessageContentPart(type: "text", text: "What's in this image?"),
+                    MessageContentPart(type: "image", imageUrl: ImageContent(base64: imageData)),
+                ])),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        if case let .user(_, content) = request.messages.first,
+           case let .multimodal(parts) = content
+        {
+            #expect(parts.count == 2)
+        } else {
+            Issue.record("Expected multimodal content")
+        }
+
+        // Test that URL images are supported
+        let urlRequest = ModelRequest(
+            messages: [
+                Message.user(content: .image(ImageContent(url: "https://example.com/image.jpg"))),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        if case let .user(_, content) = urlRequest.messages.first,
+           case .image = content
+        {
+            // Expected image content
+        } else {
+            Issue.record("Expected image content")
+        }
+
+        // Test processing (will fail at network level)
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Message type conversion")
+    func messageTypeConversion() async throws {
+        let model = AnthropicModel(apiKey: "test-key")
+
+        // Test various message types
+        let messages: [Message] = [
+            Message.system(content: "You are Claude."),
+            Message.user(content: .text("Hello Claude!")),
+            Message.assistant(content: [.outputText("Hello! How can I help you?")]),
+            Message.user(content: .text("What's 2+2?")),
+            Message.assistant(content: [.outputText("2 + 2 = 4")]),
+        ]
+
+        let request = ModelRequest(
+            messages: messages,
+            tools: nil,
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        // Verify message structure
+        #expect(request.messages.count == 5)
+        #expect(request.messages[0].type == .system)
+        #expect(request.messages[1].type == .user)
+        #expect(request.messages[2].type == .assistant)
+
+        // Test processing (will fail at network level)
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Streaming response handling")
+    func streamingResponseHandling() async throws {
+        let model = AnthropicModel(apiKey: "test-key")
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Write a short poem")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        // Test streaming (will fail at network level)
+        do {
+            let stream = try await model.getStreamedResponse(request: request)
+            var eventCount = 0
+
+            for try await event in stream {
+                eventCount += 1
+                _ = event
+            }
+
+            Issue.record("Expected network error but got \(eventCount) events")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Tool call handling")
+    func toolCallHandling() async throws {
+        let model = AnthropicModel(apiKey: "test-key")
+
+        // Create a tool call message
+        let toolCall = ToolCallItem(
+            id: "call_123",
+            type: .function,
+            function: FunctionCall(
+                name: "get_weather",
+                arguments: "{\"location\": \"Paris\"}"
+            )
+        )
+
+        let messages: [Message] = [
+            Message.user(content: .text("What's the weather in Paris?")),
+            Message.assistant(content: [.toolCall(toolCall)]),
+            Message.tool(toolCallId: "call_123", content: "It's sunny, 22°C"),
+        ]
+
+        let request = ModelRequest(
+            messages: messages,
+            tools: nil,
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        // Test tool call processing (will fail at network level)
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Model variants")
+    func modelVariants() async throws {
+        let modelNames = [
+            "claude-opus-4-20250514",
+            "claude-sonnet-4-20250514",
+            "claude-opus-4-20250514-thinking",
+            "claude-sonnet-4-20250514-thinking",
+            "claude-3-7-sonnet",
+            "claude-3-5-sonnet",
+            "claude-3-5-haiku",
+        ]
+
+        for modelName in modelNames {
+            let model = AnthropicModel(apiKey: "test-key", modelName: modelName)
+            #expect(model.maskedApiKey == "***")
+
+            // Test that each model variant can be created and handles requests
+            let request = ModelRequest(
+                messages: [Message.user(content: .text("Test"))],
+                settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+            do {
+                _ = try await model.getResponse(request: request)
+                Issue.record("Expected network error for \(modelName)")
+            } catch {
+                #expect(error is TachikomaError)
+            }
+        }
+    }
+
+    @Test("Error handling")
+    func errorHandling() async throws {
+        let model = AnthropicModel(apiKey: "invalid-key")
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Test")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error but got success")
+        } catch let error as TachikomaError {
+            // Verify we get appropriate error types
+            switch error {
+            case .apiError, .authenticationFailed, .networkError:
+                // Expected error types for invalid API key
+                break
+            default:
+                Issue.record("Unexpected error type: \(error)")
+            }
+        } catch {
+            Issue.record("Unexpected error type: \(type(of: error))")
+        }
+    }
+
+    @Test("Audio content handling")
+    func audioContentHandling() async throws {
+        let model = AnthropicModel(apiKey: "test-key")
+
+        let audioContent = AudioContent(
+            transcript: "Hello, this is a test transcript.",
+            duration: 5.0
+        )
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .audio(audioContent)),
+            ],
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        // Test audio content processing
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("File content rejection")
+    func fileContentRejection() async throws {
+        let model = AnthropicModel(apiKey: "test-key")
+
+        let fileContent = FileContent(
+            id: nil,
+            url: nil,
+            name: "test.txt"
+        )
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .file(fileContent)),
+            ],
+            settings: ModelSettings(modelName: "claude-opus-4-20250514"))
+
+        // File content should be rejected
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error for file content")
+        } catch let error as TachikomaError {
+            switch error {
+            case .invalidRequest:
+                // Expected - file content not supported
+                break
+            default:
+                Issue.record("Expected invalidRequest error, got: \(error)")
+            }
+        }
+    }
+}
+
+// MARK: - Provider Configuration Tests
+
+@Suite("Anthropic Provider Configuration Tests")
+struct AnthropicProviderConfigurationTests {
+    @Test("Provider configuration")
+    func providerConfiguration() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Test custom Anthropic configuration
+        let config = ProviderConfiguration.Anthropic(
+            apiKey: "test-key",
+            baseURL: URL(string: "https://api.anthropic.com/v1")!
+        )
+
+        await tachikoma.configureAnthropic(config)
+    }
+
+    @Test("Model registration")
+    func modelRegistration() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register Claude models
+        let modelNames = [
+            "claude-opus-4",
+            "claude-sonnet-4",
+            "claude-3-5-sonnet",
+            "claude-3-5-haiku",
+        ]
+
+        for modelName in modelNames {
+            await tachikoma.registerModel(name: modelName, factory: {
+                AnthropicModel(apiKey: "test-key", modelName: modelName)
+            })
+
+            do {
+                let model = try await tachikoma.getModel(modelName)
+                #expect(model is AnthropicModel)
+            } catch {
+                Issue.record("Failed to get model \(modelName): \(error)")
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/Tests/TachikomaTests/GrokModelTests.swift b/Tests/TachikomaTests/GrokModelTests.swift
new file mode 100644
index 0000000..47f2f96
--- /dev/null
+++ b/Tests/TachikomaTests/GrokModelTests.swift
@@ -0,0 +1,331 @@
+import Foundation
+import Testing
+@testable import Tachikoma
+
+@Suite("Grok Model Tests")
+struct GrokModelTests {
+    @Test("Model initialization")
+    func modelInitialization() async throws {
+        let model = GrokModel(
+            apiKey: "test-key-123456",
+            baseURL: URL(string: "https://api.x.ai/v1")!)
+
+        #expect(model.maskedApiKey == "test-k...56")
+    }
+
+    @Test("API key masking")
+    func apiKeyMasking() async throws {
+        // Test short key
+        let shortModel = GrokModel(apiKey: "short")
+        #expect(shortModel.maskedApiKey == "***")
+
+        // Test normal key
+        let normalModel = GrokModel(apiKey: "test-api-key-1234567890abcdefghijklmnopqrstuvwxyz")
+        #expect(normalModel.maskedApiKey == "test-a...yz")
+    }
+
+    @Test("Default base URL")
+    func defaultBaseURL() async throws {
+        let model = GrokModel(apiKey: "test-key-123456")
+
+        // Verify it uses the correct xAI API endpoint
+        // We can't directly access baseURL, but we can test the behavior
+        #expect(model.maskedApiKey == "test-k...56")
+    }
+
+    @Test("Parameter filtering for Grok 4")
+    func grok4ParameterFiltering() async throws {
+        let model = GrokModel(apiKey: "test-key")
+
+        // Create a request with parameters that should be filtered for Grok 4
+        let settings = ModelSettings(
+            modelName: "grok-4",
+            temperature: 0.7,
+            frequencyPenalty: 0.5, // Should be removed for grok-4
+            presencePenalty: 0.5, // Should be removed for grok-4
+            stopSequences: ["stop"] // Should be removed for grok-4
+        )
+
+        let request = ModelRequest(
+            messages: [
+                Message.system(content: "Test system message"),
+                Message.user(content: .text("Test user message")),
+            ],
+            tools: nil,
+            settings: settings)
+
+        // We can't directly test the filtering without mocking the network request
+        // But we can verify the model handles the request without crashing
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            // Expected to fail due to no valid API key/network
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Tool parameter conversion")
+    func toolParameterConversion() async throws {
+        let model = GrokModel(apiKey: "test-key")
+
+        // Create a tool definition
+        let tool = ToolDefinition(
+            function: FunctionDefinition(
+                name: "test_tool",
+                description: "A test tool",
+                parameters: ToolParameters(
+                    type: "object",
+                    properties: [
+                        "message": ParameterSchema(
+                            type: .string,
+                            description: "A test message"),
+                        "count": ParameterSchema(
+                            type: .integer,
+                            description: "A count",
+                            minimum: 0,
+                            maximum: 100),
+                    ],
+                    required: ["message"])))
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Use the test tool")),
+            ],
+            tools: [tool],
+            settings: ModelSettings(modelName: "grok-4"))
+
+        // Verify the model can process tool definitions
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            // Expected to fail due to no valid API key/network
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Message type conversion")
+    func messageTypeConversion() async throws {
+        let model = GrokModel(apiKey: "test-key")
+
+        // Test various message types
+        let messages: [Message] = [
+            Message.system(content: "System prompt"),
+            Message.user(content: .text("User text")),
+            Message.assistant(content: [.outputText("Assistant response")]),
+            Message.tool(
+                toolCallId: "tool-123",
+                content: "Tool result"),
+        ]
+
+        let request = ModelRequest(
+            messages: messages,
+            tools: nil,
+            settings: ModelSettings(modelName: "grok-4"))
+
+        // Verify message conversion doesn't crash
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            // Expected to fail due to no valid API key/network
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Multimodal message support")
+    func multimodalMessageSupport() async throws {
+        let model = GrokModel(apiKey: "test-key", modelName: "grok-2-vision-1212")
+
+        // Create a multimodal message with text and image
+        let imageData = Data([0xFF, 0xD8, 0xFF]) // Minimal JPEG header
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .multimodal([
+                    MessageContentPart(type: "text", text: "What is in this image?"),
+                    MessageContentPart(type: "image", imageUrl: ImageContent(base64: imageData.base64EncodedString())),
+                ])),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "grok-2-vision-1212"))
+
+        // Verify multimodal content handling
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            // Expected to fail due to no valid API key/network
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Streaming response handling")
+    func streamingResponse() async throws {
+        let model = GrokModel(apiKey: "test-key")
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Stream this response")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "grok-4"))
+
+        // Test streaming
+        do {
+            let stream = try await model.getStreamedResponse(request: request)
+            var eventCount = 0
+
+            for try await event in stream {
+                eventCount += 1
+                // Would normally process events here
+                _ = event
+            }
+
+            Issue.record("Expected network error but got success with \(eventCount) events")
+        } catch {
+            // Expected to fail due to no valid API key/network
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Error handling")
+    func errorHandling() async throws {
+        let model = GrokModel(apiKey: "invalid-key")
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Test")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "grok-4"))
+
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error but got success")
+        } catch let error as TachikomaError {
+            // Verify we get appropriate error types
+            switch error {
+            case .apiError, .authenticationFailed:
+                // Expected error types for invalid API key
+                break
+            default:
+                Issue.record("Unexpected error type: \(error)")
+            }
+        } catch {
+            Issue.record("Unexpected error type: \(type(of: error))")
+        }
+    }
+
+    @Test("Reasoning message rejection")
+    func reasoningMessageRejection() async throws {
+        let model = GrokModel(apiKey: "test-key")
+
+        let request = ModelRequest(
+            messages: [
+                Message.reasoning(content: "Some reasoning"),
+                Message.user(content: .text("Test")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "grok-4"))
+
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error for reasoning messages")
+        } catch let error as TachikomaError {
+            switch error {
+            case .invalidRequest:
+                // Expected - reasoning messages not supported
+                break
+            default:
+                Issue.record("Expected invalidRequest error, got: \(error)")
+            }
+        }
+    }
+}
+
+// MARK: - Model Provider Tests
+
+@Suite("Grok Model Provider Tests")
+struct GrokModelProviderTests {
+    @Test("Grok model registration")
+    func grokModelRegistration() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register a test Grok model
+        await tachikoma.registerModel(name: "test-grok", factory: {
+            GrokModel(apiKey: "test-key", modelName: "grok-4")
+        })
+
+        // Test that we can get the model
+        do {
+            let model = try await tachikoma.getModel("test-grok")
+            #expect(model is GrokModel)
+        } catch {
+            Issue.record("Failed to get registered model: \(error)")
+        }
+    }
+
+    @Test("Model name variants")
+    func modelNameVariants() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register various Grok model names
+        let modelNames = [
+            "grok-4",
+            "grok-4-0709",
+            "grok-4-latest",
+            "grok-2-1212",
+            "grok-2-vision-1212",
+            "grok-beta",
+            "grok-vision-beta",
+        ]
+
+        for modelName in modelNames {
+            await tachikoma.registerModel(name: modelName, factory: {
+                GrokModel(apiKey: "test-key", modelName: modelName)
+            })
+
+            do {
+                let model = try await tachikoma.getModel(modelName)
+                #expect(model is GrokModel)
+            } catch {
+                Issue.record("Failed to get model \(modelName): \(error)")
+            }
+        }
+    }
+
+    @Test("Parameter filtering detection")
+    func parameterFilteringDetection() async throws {
+        // Test that Grok 3 and 4 models filter parameters correctly
+        let grok3Model = GrokModel(apiKey: "test-key", modelName: "grok-3")
+        let grok4Model = GrokModel(apiKey: "test-key", modelName: "grok-4")
+        let grokBetaModel = GrokModel(apiKey: "test-key", modelName: "grok-beta")
+
+        // All should handle the same request without errors (though network will fail)
+        let settings = ModelSettings(
+            modelName: "grok-4",
+            temperature: 0.7,
+            frequencyPenalty: 0.5,
+            presencePenalty: 0.5,
+            stopSequences: ["stop"]
+        )
+
+        let request = ModelRequest(
+            messages: [Message.user(content: .text("Test"))],
+            settings: settings
+        )
+
+        // Test each model handles parameter filtering
+        for (name, model) in [("grok-3", grok3Model), ("grok-4", grok4Model), ("grok-beta", grokBetaModel)] {
+            do {
+                _ = try await model.getResponse(request: request)
+                Issue.record("Expected network error for \(name)")
+            } catch {
+                // Expected to fail due to network/auth, but not due to parameter issues
+                #expect(error is TachikomaError)
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/Tests/TachikomaTests/OllamaModelTests.swift b/Tests/TachikomaTests/OllamaModelTests.swift
new file mode 100644
index 0000000..f4cdbd0
--- /dev/null
+++ b/Tests/TachikomaTests/OllamaModelTests.swift
@@ -0,0 +1,611 @@
+import Foundation
+import Testing
+@testable import Tachikoma
+
+@Suite("Ollama Model Tests")
+struct OllamaModelTests {
+    @Test("Model initialization")
+    func modelInitialization() async throws {
+        let model = OllamaModel(
+            modelName: "llama3.3",
+            baseURL: URL(string: "http://localhost:11434")!)
+
+        // Ollama doesn't use API keys, so maskedApiKey should return a placeholder
+        #expect(model.maskedApiKey == "local-ollama")
+    }
+
+    @Test("Default base URL")
+    func defaultBaseURL() async throws {
+        let model = OllamaModel(modelName: "llama3.3")
+
+        // Should use default localhost URL
+        #expect(model.maskedApiKey == "local-ollama")
+    }
+
+    @Test("Custom base URL")
+    func customBaseURL() async throws {
+        let customURL = URL(string: "http://remote-server:11434")!
+        let model = OllamaModel(modelName: "llama3.3", baseURL: customURL)
+
+        #expect(model.maskedApiKey == "local-ollama")
+    }
+
+    @Test("Tool calling support detection")
+    func toolCallingSupportDetection() async throws {
+        // Models with tool calling support
+        let supportedModels = [
+            "llama3.3",
+            "llama3.2",
+            "llama3.1",
+            "mistral-nemo",
+            "firefunction-v2",
+            "command-r-plus",
+            "command-r",
+        ]
+
+        for modelName in supportedModels {
+            let model = OllamaModel(modelName: modelName)
+
+            let toolDef = ToolDefinition(
+                function: FunctionDefinition(
+                    name: "get_time",
+                    description: "Get current time",
+                    parameters: ToolParameters(
+                        properties: [:],
+                        required: [])))
+
+            let request = ModelRequest(
+                messages: [
+                    Message.user(content: .text("What time is it?")),
+                ],
+                tools: [toolDef],
+                settings: ModelSettings(modelName: "llama3.3"))
+
+            // Should handle tool calls (will fail at network level)
+            do {
+                _ = try await model.getResponse(request: request)
+                Issue.record("Expected network error for \(modelName)")
+            } catch {
+                #expect(error is TachikomaError)
+            }
+        }
+    }
+
+    @Test("Vision model tool rejection")
+    func visionModelToolRejection() async throws {
+        // Vision models that don't support tool calling
+        let visionModels = [
+            "llava",
+            "bakllava",
+            "llama3.2-vision:11b",
+            "qwen2.5vl:7b",
+        ]
+
+        for modelName in visionModels {
+            let model = OllamaModel(modelName: modelName)
+
+            let toolDef = ToolDefinition(
+                function: FunctionDefinition(
+                    name: "get_time",
+                    description: "Get current time",
+                    parameters: ToolParameters(
+                        properties: [:],
+                        required: [])))
+
+            let request = ModelRequest(
+                messages: [
+                    Message.user(content: .text("What time is it?")),
+                ],
+                tools: [toolDef],
+                settings: ModelSettings(modelName: "llama3.3"))
+
+            // Should reject tool calls for vision models
+            do {
+                _ = try await model.getResponse(request: request)
+                Issue.record("Expected error for vision model \(modelName) with tools")
+            } catch let error as TachikomaError {
+                switch error {
+                case .invalidRequest:
+                    // Expected - vision models don't support tool calling
+                    break
+                default:
+                    Issue.record("Expected invalidRequest error for \(modelName), got: \(error)")
+                }
+            }
+        }
+    }
+
+    @Test("Message type conversion")
+    func messageTypeConversion() async throws {
+        let model = OllamaModel(modelName: "llama3.3")
+
+        // Test various message types
+        let messages: [Message] = [
+            Message.system(content: "You are a helpful assistant."),
+            Message.user(content: .text("Hello!")),
+            Message.assistant(content: [.outputText("Hi there!")]),
+            Message.tool(
+                toolCallId: "call_123",
+                content: "Current time: 2:30 PM"),
+        ]
+
+        let request = ModelRequest(
+            messages: messages,
+            tools: nil,
+            settings: ModelSettings(modelName: "llama3.3"))
+
+        // Verify message conversion doesn't crash
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Multimodal message support for vision models")
+    func multimodalMessageSupport() async throws {
+        let model = OllamaModel(modelName: "llava")
+
+        // Create a multimodal message with text and image
+        let imageData = Data([0xFF, 0xD8, 0xFF]) // Minimal JPEG header
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .multimodal([
+                    MessageContentPart(type: "text", text: "What is in this image?"),
+                    MessageContentPart(type: "image", imageUrl: ImageContent(base64: imageData.base64EncodedString())),
+                ])),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "llava"))
+
+        // Verify multimodal content handling for vision models
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Text-only models image rejection")
+    func textOnlyModelsImageRejection() async throws {
+        let model = OllamaModel(modelName: "llama3.3") // Text-only model
+
+        let imageData = Data([0xFF, 0xD8, 0xFF])
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .image(ImageContent(base64: imageData.base64EncodedString()))),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "llama3.3"))
+
+        // Should reject image content for text-only models
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error for text-only model with image")
+        } catch let error as TachikomaError {
+            switch error {
+            case .invalidRequest:
+                // Expected - text-only models don't support images
+                break
+            default:
+                Issue.record("Expected invalidRequest error, got: \(error)")
+            }
+        }
+    }
+
+    @Test("Streaming response handling")
+    func streamingResponse() async throws {
+        let model = OllamaModel(modelName: "llama3.3")
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Tell me a joke")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "llama3.3"))
+
+        // Test streaming
+        do {
+            let stream = try await model.getStreamedResponse(request: request)
+            var eventCount = 0
+
+            for try await event in stream {
+                eventCount += 1
+                _ = event
+            }
+
+            Issue.record("Expected network error but got success with \(eventCount) events")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Extended timeout handling")
+    func extendedTimeoutHandling() async throws {
+        let model = OllamaModel(modelName: "llama3.3")
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Generate a long response")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "llama3.3"))
+
+        // Ollama requests should have extended timeouts (5 minutes)
+        // We can't test the actual timeout without a real server,
+        // but we can verify the request structure
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Tool call JSON parsing")
+    func toolCallJSONParsing() async throws {
+        let model = OllamaModel(modelName: "llama3.3")
+
+        // Test models that output tool calls as JSON in content
+        let toolDef = ToolDefinition(
+            function: FunctionDefinition(
+                name: "calculate",
+                description: "Perform calculation",
+                parameters: ToolParameters(
+                    properties: [
+                        "expression": ParameterSchema(type: .string, description: "Math expression")
+                    ],
+                    required: ["expression"])))
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("What is 5 + 3?")),
+            ],
+            tools: [toolDef],
+            settings: ModelSettings(modelName: "llama3.3"))
+
+        // Should handle tool call parsing
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Error handling")
+    func errorHandling() async throws {
+        let model = OllamaModel(modelName: "nonexistent-model")
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Test")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "llama3.3"))
+
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error but got success")
+        } catch let error as TachikomaError {
+            // Verify we get appropriate error types
+            switch error {
+            case .apiError, .networkError:
+                // Expected error types for nonexistent model
+                break
+            default:
+                Issue.record("Unexpected error type: \(error)")
+            }
+        } catch {
+            Issue.record("Unexpected error type: \(type(of: error))")
+        }
+    }
+
+    @Test("Reasoning message rejection")
+    func reasoningMessageRejection() async throws {
+        let model = OllamaModel(modelName: "llama3.3")
+
+        let request = ModelRequest(
+            messages: [
+                Message.reasoning(content: "Let me think..."),
+                Message.user(content: .text("Test")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "llama3.3"))
+
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error for reasoning messages")
+        } catch let error as TachikomaError {
+            switch error {
+            case .invalidRequest:
+                // Expected - reasoning messages not supported
+                break
+            default:
+                Issue.record("Expected invalidRequest error, got: \(error)")
+            }
+        }
+    }
+
+    @Test("File content rejection")
+    func fileContentRejection() async throws {
+        let model = OllamaModel(modelName: "llama3.3")
+
+        let fileContent = FileContent(
+            id: nil,
+            url: nil,
+            name: "test.txt"
+        )
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .file(fileContent)),
+            ],
+            settings: ModelSettings(modelName: "llama3.3"))
+
+        // File content should be rejected
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error for file content")
+        } catch let error as TachikomaError {
+            switch error {
+            case .invalidRequest:
+                // Expected - file content not supported
+                break
+            default:
+                Issue.record("Expected invalidRequest error, got: \(error)")
+            }
+        }
+    }
+
+    @Test("Audio content handling")
+    func audioContentHandling() async throws {
+        let model = OllamaModel(modelName: "llama3.3")
+
+        let audioContent = AudioContent(
+            transcript: "Hello, this is a test transcript.",
+            duration: 5.0
+        )
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .audio(audioContent)),
+            ],
+            settings: ModelSettings(modelName: "llama3.3"))
+
+        // Test audio content processing (converts to text)
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+}
+
+// MARK: - Model Provider Tests
+
+@Suite("Ollama Model Provider Tests")
+struct OllamaModelProviderTests {
+    @Test("Ollama model registration")
+    func ollamaModelRegistration() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register a test Ollama model
+        await tachikoma.registerModel(name: "test-llama", factory: {
+            OllamaModel(modelName: "llama3.3")
+        })
+
+        // Test that we can get the model
+        do {
+            let model = try await tachikoma.getModel("test-llama")
+            #expect(model is OllamaModel)
+        } catch {
+            Issue.record("Failed to get registered model: \(error)")
+        }
+    }
+
+    @Test("Model name variants")
+    func modelNameVariants() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register various Ollama model names
+        let modelNames = [
+            "llama3.3",
+            "llama3.2",
+            "llama3.1",
+            "llava",
+            "mistral-nemo",
+            "firefunction-v2",
+            "command-r-plus",
+            "deepseek-r1:8b",
+        ]
+
+        for modelName in modelNames {
+            await tachikoma.registerModel(name: modelName, factory: {
+                OllamaModel(modelName: modelName)
+            })
+
+            do {
+                let model = try await tachikoma.getModel(modelName)
+                #expect(model is OllamaModel)
+            } catch {
+                Issue.record("Failed to get model \(modelName): \(error)")
+            }
+        }
+    }
+
+    @Test("Base URL configuration")
+    func baseURLConfiguration() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Test custom base URL
+        let customURL = URL(string: "http://remote-ollama:11434")!
+
+        await tachikoma.registerModel(name: "custom-ollama", factory: {
+            OllamaModel(modelName: "llama3.3", baseURL: customURL)
+        })
+
+        do {
+            let model = try await tachikoma.getModel("custom-ollama")
+            #expect(model is OllamaModel)
+        } catch {
+            Issue.record("Failed to get custom URL model: \(error)")
+        }
+    }
+
+    @Test("Tool support matrix")
+    func toolSupportMatrix() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Models with tool support
+        let toolSupportedModels = [
+            "llama3.3",
+            "llama3.2",
+            "mistral-nemo",
+            "firefunction-v2",
+        ]
+
+        // Models without tool support  
+        let nonToolModels = [
+            "llava",
+            "bakllava",
+            "devstral",
+        ]
+
+        let toolDef = ToolDefinition(
+            function: FunctionDefinition(
+                name: "test_tool",
+                description: "Test tool",
+                parameters: ToolParameters(properties: [:], required: [])))
+
+        // Test tool-supported models
+        for modelName in toolSupportedModels {
+            await tachikoma.registerModel(name: "tool-\(modelName)", factory: {
+                OllamaModel(modelName: modelName)
+            })
+
+            do {
+                let model = try await tachikoma.getModel("tool-\(modelName)")
+                #expect(model is OllamaModel)
+
+                // Should accept tool definitions
+                let request = ModelRequest(
+                    messages: [Message.user(content: .text("Use tool"))],
+                    tools: [toolDef],
+                    settings: ModelSettings(modelName: "llama3.3"))
+
+                do {
+                    _ = try await model.getResponse(request: request)
+                    Issue.record("Expected network error for \(modelName)")
+                } catch {
+                    #expect(error is TachikomaError)
+                }
+            } catch {
+                Issue.record("Failed to get tool model \(modelName): \(error)")
+            }
+        }
+
+        // Test non-tool models
+        for modelName in nonToolModels {
+            await tachikoma.registerModel(name: "no-tool-\(modelName)", factory: {
+                OllamaModel(modelName: modelName)
+            })
+
+            do {
+                let model = try await tachikoma.getModel("no-tool-\(modelName)")
+                #expect(model is OllamaModel)
+
+                // Should reject tool definitions
+                let request = ModelRequest(
+                    messages: [Message.user(content: .text("Use tool"))],
+                    tools: [toolDef],
+                    settings: ModelSettings(modelName: "llama3.3"))
+
+                do {
+                    _ = try await model.getResponse(request: request)
+                    Issue.record("Expected error for non-tool model \(modelName)")
+                } catch let error as TachikomaError {
+                    switch error {
+                    case .invalidRequest:
+                        // Expected for non-tool models
+                        break
+                    default:
+                        Issue.record("Expected invalidRequest for \(modelName), got: \(error)")
+                    }
+                }
+            } catch {
+                Issue.record("Failed to get non-tool model \(modelName): \(error)")
+            }
+        }
+    }
+
+    @Test("Vision capability detection")
+    func visionCapabilityDetection() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Vision models
+        let visionModels = ["llava", "bakllava", "llama3.2-vision:11b"]
+        
+        // Text-only models
+        let textModels = ["llama3.3", "mistral-nemo", "command-r"]
+
+        let imageData = Data([0xFF, 0xD8, 0xFF])
+
+        // Test vision models accept images
+        for modelName in visionModels {
+            await tachikoma.registerModel(name: "vision-\(modelName)", factory: {
+                OllamaModel(modelName: modelName)
+            })
+
+            do {
+                let model = try await tachikoma.getModel("vision-\(modelName)")
+                let request = ModelRequest(
+                    messages: [Message.user(content: .image(ImageContent(base64: imageData.base64EncodedString())))],
+                    settings: ModelSettings(modelName: "llama3.3"))
+
+                do {
+                    _ = try await model.getResponse(request: request)
+                    Issue.record("Expected network error for vision model \(modelName)")
+                } catch {
+                    #expect(error is TachikomaError)
+                }
+            } catch {
+                Issue.record("Failed vision model test for \(modelName): \(error)")
+            }
+        }
+
+        // Test text models reject images
+        for modelName in textModels {
+            await tachikoma.registerModel(name: "text-\(modelName)", factory: {
+                OllamaModel(modelName: modelName)
+            })
+
+            do {
+                let model = try await tachikoma.getModel("text-\(modelName)")
+                let request = ModelRequest(
+                    messages: [Message.user(content: .image(ImageContent(base64: imageData.base64EncodedString())))],
+                    settings: ModelSettings(modelName: "llama3.3"))
+
+                do {
+                    _ = try await model.getResponse(request: request)
+                    Issue.record("Expected error for text model \(modelName) with image")
+                } catch let error as TachikomaError {
+                    switch error {
+                    case .invalidRequest:
+                        // Expected for text-only models
+                        break
+                    default:
+                        Issue.record("Expected invalidRequest for \(modelName), got: \(error)")
+                    }
+                }
+            } catch {
+                Issue.record("Failed text model test for \(modelName): \(error)")
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/Tests/TachikomaTests/OpenAIModelTests.swift b/Tests/TachikomaTests/OpenAIModelTests.swift
new file mode 100644
index 0000000..a1f1644
--- /dev/null
+++ b/Tests/TachikomaTests/OpenAIModelTests.swift
@@ -0,0 +1,475 @@
+import Foundation
+import Testing
+@testable import Tachikoma
+
+@Suite("OpenAI Model Tests")
+struct OpenAIModelTests {
+    @Test("Model initialization")
+    func modelInitialization() async throws {
+        let model = OpenAIModel(
+            apiKey: "sk-test-key-123456789",
+            modelName: "gpt-4.1")
+
+        #expect(model.maskedApiKey == "sk-...789")
+    }
+
+    @Test("API key masking")
+    func apiKeyMasking() async throws {
+        // Test short key
+        let shortModel = OpenAIModel(apiKey: "short")
+        #expect(shortModel.maskedApiKey == "***")
+
+        // Test normal key
+        let normalModel = OpenAIModel(apiKey: "sk-test-api-key-1234567890abcdefghijklmnopqrstuvwxyz")
+        #expect(normalModel.maskedApiKey == "sk-...xyz")
+    }
+
+    @Test("Default base URL")
+    func defaultBaseURL() async throws {
+        let model = OpenAIModel(apiKey: "test-key")
+
+        // Verify it uses the correct OpenAI API endpoint
+        // We can't directly access baseURL, but we can test the behavior
+        #expect(model.maskedApiKey == "***")
+    }
+
+    @Test("Dual API support")
+    func dualAPISupport() async throws {
+        let model = OpenAIModel(apiKey: "test-key")
+
+        // Test Chat Completions API request
+        let chatRequest = ModelRequest(
+            messages: [
+                Message.user(content: .text("Hello")),
+            ],
+            tools: nil,
+            settings: ModelSettings(apiType: "chat"))
+
+        // Test Responses API request (for reasoning models)
+        let responsesRequest = ModelRequest(
+            messages: [
+                Message.user(content: .text("Hello")),
+            ],
+            tools: nil,
+            settings: ModelSettings(apiType: "responses"))
+
+        // Both should be processable (will fail at network level)
+        do {
+            _ = try await model.getResponse(request: chatRequest)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+
+        do {
+            _ = try await model.getResponse(request: responsesRequest)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Reasoning models parameter handling")
+    func reasoningModelsParameterHandling() async throws {
+        let model = OpenAIModel(apiKey: "test-key", modelName: "o3")
+
+        // Create a request with reasoning parameters
+        let settings = ModelSettings(
+            reasoningEffort: "medium",
+            reasoning: ["summary": "detailed"],
+            temperature: nil // o3 models don't support temperature
+        )
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Solve this complex problem")),
+            ],
+            tools: nil,
+            settings: settings)
+
+        // Should handle reasoning parameters correctly
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Tool parameter conversion")
+    func toolParameterConversion() async throws {
+        let model = OpenAIModel(apiKey: "test-key")
+
+        // Create a tool definition
+        let tool = ToolDefinition(
+            function: FunctionDefinition(
+                name: "get_weather",
+                description: "Get current weather",
+                parameters: ToolParameters(
+                    type: "object",
+                    properties: [
+                        "location": ParameterSchema(
+                            type: .string,
+                            description: "The location"),
+                        "units": ParameterSchema(
+                            type: .string,
+                            description: "Temperature units",
+                            enumValues: ["celsius", "fahrenheit"]),
+                    ],
+                    required: ["location"])))
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("What's the weather in Paris?")),
+            ],
+            tools: [tool],
+            settings: ModelSettings(modelName: "gpt-4.1"))
+
+        // Verify the model can process tool definitions
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Message type conversion")
+    func messageTypeConversion() async throws {
+        let model = OpenAIModel(apiKey: "test-key")
+
+        // Test various message types
+        let messages: [Message] = [
+            Message.system(content: "You are a helpful assistant."),
+            Message.user(content: .text("Hello!")),
+            Message.assistant(content: [.outputText("Hi there!")]),
+            Message.tool(
+                toolCallId: "call_123",
+                content: "Weather data"),
+        ]
+
+        let request = ModelRequest(
+            messages: messages,
+            tools: nil,
+            settings: ModelSettings(modelName: "gpt-4.1"))
+
+        // Verify message conversion doesn't crash
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Multimodal message support")
+    func multimodalMessageSupport() async throws {
+        let model = OpenAIModel(apiKey: "test-key", modelName: "gpt-4o")
+
+        // Create a multimodal message with text and image
+        let imageData = Data([0xFF, 0xD8, 0xFF]) // Minimal JPEG header
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .multimodal([
+                    MessageContentPart(type: "text", text: "What is in this image?"),
+                    MessageContentPart(type: "image", imageUrl: ImageContent(base64: imageData.base64EncodedString())),
+                ])),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "gpt-4.1"))
+
+        // Verify multimodal content handling
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Streaming response handling")
+    func streamingResponse() async throws {
+        let model = OpenAIModel(apiKey: "test-key")
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Write a short story")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "gpt-4.1"))
+
+        // Test streaming
+        do {
+            let stream = try await model.getStreamedResponse(request: request)
+            var eventCount = 0
+
+            for try await event in stream {
+                eventCount += 1
+                _ = event
+            }
+
+            Issue.record("Expected network error but got success with \(eventCount) events")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Error handling")
+    func errorHandling() async throws {
+        let model = OpenAIModel(apiKey: "invalid-key")
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .text("Test")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "gpt-4.1"))
+
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error but got success")
+        } catch let error as TachikomaError {
+            // Verify we get appropriate error types
+            switch error {
+            case .apiError, .authenticationFailed:
+                // Expected error types for invalid API key
+                break
+            default:
+                Issue.record("Unexpected error type: \(error)")
+            }
+        } catch {
+            Issue.record("Unexpected error type: \(type(of: error))")
+        }
+    }
+
+    @Test("Reasoning message handling")
+    func reasoningMessageHandling() async throws {
+        let model = OpenAIModel(apiKey: "test-key", modelName: "o3")
+
+        let request = ModelRequest(
+            messages: [
+                Message.reasoning(content: "Let me think about this step by step..."),
+                Message.user(content: .text("What is 2+2?")),
+            ],
+            tools: nil,
+            settings: ModelSettings(modelName: "gpt-4.1"))
+
+        // o3 models should handle reasoning messages
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error but got success")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+
+    @Test("Model variants")
+    func modelVariants() async throws {
+        let modelNames = [
+            "o3",
+            "o3-mini",
+            "o3-pro",
+            "o4-mini",
+            "gpt-4.1",
+            "gpt-4.1-mini",
+            "gpt-4o",
+            "gpt-4o-mini",
+        ]
+
+        for modelName in modelNames {
+            let model = OpenAIModel(apiKey: "test-key", modelName: modelName)
+            #expect(model.maskedApiKey == "***")
+
+            // Test that each model variant can be created and handles requests
+            let request = ModelRequest(
+                messages: [Message.user(content: .text("Test"))],
+                settings: ModelSettings(modelName: "gpt-4.1"))
+
+            do {
+                _ = try await model.getResponse(request: request)
+                Issue.record("Expected network error for \(modelName)")
+            } catch {
+                #expect(error is TachikomaError)
+            }
+        }
+    }
+
+    @Test("Temperature parameter filtering")
+    func temperatureParameterFiltering() async throws {
+        // o3 models should not support temperature
+        let o3Model = OpenAIModel(apiKey: "test-key", modelName: "o3")
+        let gptModel = OpenAIModel(apiKey: "test-key", modelName: "gpt-4.1")
+
+        let settings = ModelSettings(temperature: 0.7)
+
+        let request = ModelRequest(
+            messages: [Message.user(content: .text("Test"))],
+            settings: settings)
+
+        // Both should handle the request (temperature filtered for o3)
+        for (name, model) in [("o3", o3Model), ("gpt-4.1", gptModel)] {
+            do {
+                _ = try await model.getResponse(request: request)
+                Issue.record("Expected network error for \(name)")
+            } catch {
+                #expect(error is TachikomaError)
+            }
+        }
+    }
+
+    @Test("File content rejection")
+    func fileContentRejection() async throws {
+        let model = OpenAIModel(apiKey: "test-key")
+
+        let fileContent = FileContent(
+            filename: "test.txt",
+            content: "Test file content",
+            mimeType: "text/plain"
+        )
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .file(fileContent)),
+            ],
+            settings: ModelSettings(modelName: "gpt-4.1"))
+
+        // File content should be rejected
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected error for file content")
+        } catch let error as TachikomaError {
+            switch error {
+            case .invalidRequest:
+                // Expected - file content not supported
+                break
+            default:
+                Issue.record("Expected invalidRequest error, got: \(error)")
+            }
+        }
+    }
+
+    @Test("Audio content handling")
+    func audioContentHandling() async throws {
+        let model = OpenAIModel(apiKey: "test-key")
+
+        let audioContent = AudioContent(
+            transcript: "Hello, this is a test transcript.",
+            duration: 5.0
+        )
+
+        let request = ModelRequest(
+            messages: [
+                Message.user(content: .audio(audioContent)),
+            ],
+            settings: ModelSettings(modelName: "gpt-4.1"))
+
+        // Test audio content processing
+        do {
+            _ = try await model.getResponse(request: request)
+            Issue.record("Expected network error")
+        } catch {
+            #expect(error is TachikomaError)
+        }
+    }
+}
+
+// MARK: - Provider Configuration Tests
+
+@Suite("OpenAI Provider Configuration Tests")
+struct OpenAIProviderConfigurationTests {
+    @Test("Provider configuration")
+    func providerConfiguration() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Test custom OpenAI configuration
+        let config = ProviderConfiguration.OpenAI(
+            apiKey: "test-key",
+            baseURL: URL(string: "https://api.openai.com/v1")!
+        )
+
+        await tachikoma.configureOpenAI(config)
+    }
+
+    @Test("Model registration")
+    func modelRegistration() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register OpenAI models
+        let modelNames = [
+            "o3",
+            "o3-mini",
+            "gpt-4.1",
+            "gpt-4o",
+        ]
+
+        for modelName in modelNames {
+            await tachikoma.registerModel(name: modelName, factory: {
+                OpenAIModel(apiKey: "test-key", modelName: modelName)
+            })
+
+            do {
+                let model = try await tachikoma.getModel(modelName)
+                #expect(model is OpenAIModel)
+            } catch {
+                Issue.record("Failed to get model \(modelName): \(error)")
+            }
+        }
+    }
+
+    @Test("API type selection")
+    func apiTypeSelection() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register models with different API preferences
+        await tachikoma.registerModel(name: "gpt-4.1-chat", factory: {
+            OpenAIModel(apiKey: "test-key", modelName: "gpt-4.1")
+        })
+
+        await tachikoma.registerModel(name: "o3-responses", factory: {
+            OpenAIModel(apiKey: "test-key", modelName: "o3")
+        })
+
+        // Test that both can be retrieved
+        do {
+            let chatModel = try await tachikoma.getModel("gpt-4.1-chat")
+            #expect(chatModel is OpenAIModel)
+
+            let responsesModel = try await tachikoma.getModel("o3-responses")
+            #expect(responsesModel is OpenAIModel)
+        } catch {
+            Issue.record("Failed to get models: \(error)")
+        }
+    }
+
+    @Test("Lenient model name resolution")
+    func lenientModelNameResolution() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register base models
+        await tachikoma.registerModel(name: "gpt-4.1", factory: {
+            OpenAIModel(apiKey: "test-key", modelName: "gpt-4.1")
+        })
+
+        await tachikoma.registerModel(name: "o3", factory: {
+            OpenAIModel(apiKey: "test-key", modelName: "o3")
+        })
+
+        // Test lenient name matching
+        let nameMapping = [
+            "gpt": "gpt-4.1",
+            "gpt-4": "gpt-4.1",
+            "gpt4": "gpt-4.1",
+            "o3": "o3",
+        ]
+
+        for (input, _) in nameMapping {
+            do {
+                let model = try await tachikoma.getModel(input)
+                #expect(model is OpenAIModel)
+            } catch {
+                Issue.record("Failed to resolve \(input): \(error)")
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/Tests/TachikomaTests/StreamingAndToolTests.swift b/Tests/TachikomaTests/StreamingAndToolTests.swift
new file mode 100644
index 0000000..b40458d
--- /dev/null
+++ b/Tests/TachikomaTests/StreamingAndToolTests.swift
@@ -0,0 +1,439 @@
+import Foundation
+import Testing
+@testable import Tachikoma
+
+@Suite("Streaming Types Tests")
+struct StreamingTypesTests {
+    @Test("StreamEvent creation and types")
+    func streamEventCreationAndTypes() {
+        let events: [StreamEvent] = [
+            .contentDelta("Hello"),
+            .contentComplete("Hello, world!"),
+            .toolCallDelta("tool_123", "get_", "{}"),
+            .toolCallComplete("tool_123", "get_weather", "{\"location\": \"SF\"}"),
+            .reasoningDelta("I need to think..."),
+            .reasoningComplete("I need to think about this carefully."),
+            .done,
+            .error("Network error"),
+            .metadata(["usage": ["tokens": 42]]),
+        ]
+        
+        #expect(events.count == 9)
+        
+        // Test specific event properties
+        if case let .contentDelta(text) = events[0] {
+            #expect(text == "Hello")
+        } else {
+            Issue.record("Expected contentDelta event")
+        }
+        
+        if case let .toolCallDelta(id, name, args) = events[2] {
+            #expect(id == "tool_123")
+            #expect(name == "get_")
+            #expect(args == "{}")
+        } else {
+            Issue.record("Expected toolCallDelta event")
+        }
+        
+        if case .done = events[6] {
+            // Expected
+        } else {
+            Issue.record("Expected done event")
+        }
+    }
+
+    @Test("StreamEvent Codable")
+    func streamEventCodable() throws {
+        let originalEvents: [StreamEvent] = [
+            .contentDelta("Hello"),
+            .toolCallComplete("tool_123", "get_weather", "{\"location\": \"SF\"}"),
+            .done,
+            .error("Network error"),
+            .metadata(["usage": ["tokens": 42]]),
+        ]
+        
+        let encoder = JSONEncoder()
+        let decoder = JSONDecoder()
+        
+        for originalEvent in originalEvents {
+            let data = try encoder.encode(originalEvent)
+            let decodedEvent = try decoder.decode(StreamEvent.self, from: data)
+            
+            // Compare events (simplified comparison)
+            switch (originalEvent, decodedEvent) {
+            case let (.contentDelta(orig), .contentDelta(decoded)):
+                #expect(orig == decoded)
+            case let (.toolCallComplete(origId, origName, origArgs), .toolCallComplete(decodedId, decodedName, decodedArgs)):
+                #expect(origId == decodedId)
+                #expect(origName == decodedName)
+                #expect(origArgs == decodedArgs)
+            case (.done, .done):
+                // Expected
+                break
+            case let (.error(orig), .error(decoded)):
+                #expect(orig == decoded)
+            case (.metadata, .metadata):
+                // Metadata comparison is complex, just verify it decodes
+                break
+            default:
+                Issue.record("Event types don't match")
+            }
+        }
+    }
+
+    @Test("StreamingResponseIterator behavior")
+    func streamingResponseIteratorBehavior() async throws {
+        // Create a mock stream of events
+        let events: [StreamEvent] = [
+            .contentDelta("Hello"),
+            .contentDelta(" world"),
+            .contentComplete("Hello world!"),
+            .done
+        ]
+        
+        // Create an AsyncStream to simulate streaming
+        let stream = AsyncThrowingStream<StreamEvent, Error> { continuation in
+            Task {
+                for event in events {
+                    continuation.yield(event)
+                    try await Task.sleep(nanoseconds: 1_000_000) // 1ms delay
+                }
+                continuation.finish()
+            }
+        }
+        
+        // Collect events from the stream
+        var collectedEvents: [StreamEvent] = []
+        
+        do {
+            for try await event in stream {
+                collectedEvents.append(event)
+            }
+        } catch {
+            Issue.record("Stream iteration failed: \(error)")
+        }
+        
+        #expect(collectedEvents.count == 4)
+        
+        // Verify event sequence
+        if case let .contentDelta(text1) = collectedEvents[0] {
+            #expect(text1 == "Hello")
+        } else {
+            Issue.record("Expected first contentDelta")
+        }
+        
+        if case let .contentDelta(text2) = collectedEvents[1] {
+            #expect(text2 == " world")
+        } else {
+            Issue.record("Expected second contentDelta")
+        }
+        
+        if case .done = collectedEvents[3] {
+            // Expected
+        } else {
+            Issue.record("Expected done event at end")
+        }
+    }
+
+    @Test("StreamEvent error handling")
+    func streamEventErrorHandling() async throws {
+        let stream = AsyncThrowingStream<StreamEvent, Error> { continuation in
+            continuation.yield(.contentDelta("Hello"))
+            continuation.finish(throwing: TachikomaError.networkError("Connection lost"))
+        }
+        
+        var collectedEvents: [StreamEvent] = []
+        var caughtError: Error?
+        
+        do {
+            for try await event in stream {
+                collectedEvents.append(event)
+            }
+        } catch {
+            caughtError = error
+        }
+        
+        #expect(collectedEvents.count == 1)
+        #expect(caughtError is TachikomaError)
+        
+        if let tachikomaError = caughtError as? TachikomaError,
+           case let .networkError(message) = tachikomaError {
+            #expect(message == "Connection lost")
+        } else {
+            Issue.record("Expected TachikomaError.networkError")
+        }
+    }
+}
+
+// MARK: - Tool Definition Tests
+
+@Suite("Tool Definition Tests")
+struct ToolDefinitionTests {
+    @Test("Simple tool definition")
+    func simpleToolDefinition() {
+        let tool = ToolDefinition(
+            function: FunctionDefinition(
+                name: "get_time",
+                description: "Get the current time",
+                parameters: ToolParameters(
+                    properties: [:],
+                    required: []
+                )
+            )
+        )
+        
+        #expect(tool.function.name == "get_time")
+        #expect(tool.function.description == "Get the current time")
+        #expect(tool.function.parameters.properties.isEmpty)
+        #expect(tool.function.parameters.required.isEmpty)
+    }
+
+    @Test("Tool definition with parameters")
+    func toolDefinitionWithParameters() {
+        let tool = ToolDefinition(
+            function: FunctionDefinition(
+                name: "get_weather",
+                description: "Get weather information",
+                parameters: ToolParameters(
+                    type: "object",
+                    properties: [
+                        "location": ParameterSchema(
+                            type: .string,
+                            description: "The location to get weather for"
+                        ),
+                        "units": ParameterSchema(
+                            type: .string,
+                            description: "Temperature units",
+                            enumValues: ["celsius", "fahrenheit"]
+                        ),
+                        "include_forecast": ParameterSchema(
+                            type: .boolean,
+                            description: "Include forecast data"
+                        )
+                    ],
+                    required: ["location"]
+                )
+            )
+        )
+        
+        #expect(tool.function.name == "get_weather")
+        #expect(tool.function.parameters.properties.count == 3)
+        #expect(tool.function.parameters.required == ["location"])
+        
+        // Check parameter schemas
+        let locationParam = tool.function.parameters.properties["location"]
+        #expect(locationParam?.type == .string)
+        #expect(locationParam?.description == "The location to get weather for")
+        
+        let unitsParam = tool.function.parameters.properties["units"]
+        #expect(unitsParam?.enumValues == ["celsius", "fahrenheit"])
+    }
+
+    @Test("ParameterSchema types")
+    func parameterSchemaTypes() {
+        let schemas: [ParameterSchema] = [
+            ParameterSchema(type: .string, description: "A string value"),
+            ParameterSchema(type: .integer, description: "An integer value", minimum: 0, maximum: 100),
+            ParameterSchema(type: .number, description: "A number value"),
+            ParameterSchema(type: .boolean, description: "A boolean value"),
+            ParameterSchema(type: .array, description: "An array value"),
+            ParameterSchema(type: .object, description: "An object value"),
+        ]
+        
+        #expect(schemas.count == 6)
+        
+        // Test specific properties
+        let intSchema = schemas[1]
+        #expect(intSchema.type == .integer)
+        #expect(intSchema.minimum == 0)
+        #expect(intSchema.maximum == 100)
+    }
+
+    @Test("Tool parameters codable")
+    func toolParametersCodable() throws {
+        let original = ToolParameters(
+            type: "object",
+            properties: [
+                "name": ParameterSchema(type: .string, description: "Name field"),
+                "age": ParameterSchema(type: .integer, description: "Age field", minimum: 0),
+            ],
+            required: ["name"]
+        )
+        
+        let encoder = JSONEncoder()
+        let data = try encoder.encode(original)
+        
+        let decoder = JSONDecoder()
+        let decoded = try decoder.decode(ToolParameters.self, from: data)
+        
+        #expect(decoded.type == original.type)
+        #expect(decoded.properties.count == original.properties.count)
+        #expect(decoded.required == original.required)
+        
+        let nameParam = decoded.properties["name"]
+        #expect(nameParam?.type == .string)
+        #expect(nameParam?.description == "Name field")
+    }
+
+    @Test("Generic Tool creation")
+    func genericToolCreation() async throws {
+        // Context type for the tool
+        struct WeatherContext {
+            let apiKey: String
+        }
+        
+        // Create a generic tool
+        let weatherTool = Tool<WeatherContext>(
+            name: "get_weather",
+            description: "Get weather for a location",
+            parameters: ToolParameters(
+                properties: [
+                    "location": ParameterSchema(type: .string, description: "Location name")
+                ],
+                required: ["location"]
+            )
+        ) { input, context in
+            // Simulate tool execution
+            var location = "Unknown"
+            if case let .dictionary(dict) = input {
+                location = dict["location"] as? String ?? "Unknown"
+            }
+            return .string("Weather in \(location): 72°F and sunny (API key: \(context.apiKey.prefix(3))...)")
+        }
+        
+        // Convert to tool definition
+        let toolDef = weatherTool.toToolDefinition()
+        
+        #expect(toolDef.function.name == "get_weather")
+        #expect(toolDef.function.description == "Get weather for a location")
+        
+        // Test tool execution
+        let context = WeatherContext(apiKey: "test-api-key-123")
+        let input = ToolInput.dictionary(["location": "San Francisco"])
+        
+        let output = try await weatherTool.execute(input, context)
+        
+        if case let .string(result) = output {
+            #expect(result.contains("San Francisco"))
+            #expect(result.contains("test..."))
+        } else {
+            Issue.record("Expected string output")
+        }
+    }
+
+    @Test("ToolCallItem creation")
+    func toolCallItemCreation() {
+        let toolCall = ToolCallItem(
+            id: "call_abc123",
+            type: .function,
+            function: FunctionCall(
+                name: "calculate",
+                arguments: "{\"expression\": \"2 + 2\"}"
+            )
+        )
+        
+        #expect(toolCall.id == "call_abc123")
+        #expect(toolCall.type == .function)
+        #expect(toolCall.function.name == "calculate")
+        #expect(toolCall.function.arguments == "{\"expression\": \"2 + 2\"}")
+    }
+
+    @Test("ToolInput and ToolOutput")
+    func toolInputAndOutput() {
+        let input = ToolInput.dictionary([
+            "location": "Paris",
+            "units": "celsius"
+        ])
+        
+        if case let .dictionary(args) = input {
+            #expect(args["location"] as? String == "Paris")
+            #expect(args["units"] as? String == "celsius")
+        } else {
+            Issue.record("Expected dictionary input")
+        }
+        
+        let output = ToolOutput.string("Weather in Paris: 18°C and cloudy")
+        
+        if case let .string(content) = output {
+            #expect(content == "Weather in Paris: 18°C and cloudy")
+        } else {
+            Issue.record("Expected string output")
+        }
+    }
+
+    @Test("FunctionCall argument parsing")
+    func functionCallArgumentParsing() throws {
+        let functionCall = FunctionCall(
+            name: "get_weather",
+            arguments: "{\"location\": \"Tokyo\", \"units\": \"celsius\"}"
+        )
+        
+        #expect(functionCall.name == "get_weather")
+        #expect(functionCall.arguments == "{\"location\": \"Tokyo\", \"units\": \"celsius\"}")
+        
+        // Test parsing arguments as JSON
+        let data = functionCall.arguments.data(using: .utf8)!
+        let parsed = try JSONSerialization.jsonObject(with: data) as? [String: Any]
+        
+        #expect(parsed?["location"] as? String == "Tokyo")
+        #expect(parsed?["units"] as? String == "celsius")
+    }
+
+    @Test("ParameterSchema with complex properties")
+    func parameterSchemaWithComplexProperties() {
+        let schema = ParameterSchema(
+            type: .object,
+            description: "A complex object",
+            properties: [
+                "nested_string": ParameterSchema(type: .string, description: "Nested string"),
+                "nested_array": ParameterSchema(type: .array, description: "Nested array"),
+            ]
+        )
+        
+        #expect(schema.type == .object)
+        #expect(schema.properties?.count == 2)
+        
+        let nestedString = schema.properties?["nested_string"] as? ParameterSchema
+        #expect(nestedString?.type == .string)
+        #expect(nestedString?.description == "Nested string")
+    }
+
+    @Test("Tool definition JSON serialization")
+    func toolDefinitionJSONSerialization() throws {
+        let tool = ToolDefinition(
+            function: FunctionDefinition(
+                name: "calculate",
+                description: "Perform a calculation",
+                parameters: ToolParameters(
+                    type: "object",
+                    properties: [
+                        "expression": ParameterSchema(
+                            type: .string,
+                            description: "Mathematical expression to evaluate"
+                        )
+                    ],
+                    required: ["expression"]
+                )
+            )
+        )
+        
+        let encoder = JSONEncoder()
+        encoder.outputFormatting = .prettyPrinted
+        
+        let jsonData = try encoder.encode(tool)
+        let jsonString = String(data: jsonData, encoding: .utf8)!
+        
+        #expect(jsonString.contains("calculate"))
+        #expect(jsonString.contains("Perform a calculation"))
+        #expect(jsonString.contains("expression"))
+        #expect(jsonString.contains("Mathematical expression"))
+        
+        // Test round-trip encoding/decoding
+        let decoder = JSONDecoder()
+        let decoded = try decoder.decode(ToolDefinition.self, from: jsonData)
+        
+        #expect(decoded.function.name == tool.function.name)
+        #expect(decoded.function.description == tool.function.description)
+        #expect(decoded.function.parameters.required == tool.function.parameters.required)
+    }
+}
\ No newline at end of file
diff --git a/Tests/TachikomaTests/TachikomaCoreTests.swift b/Tests/TachikomaTests/TachikomaCoreTests.swift
new file mode 100644
index 0000000..06cd39f
--- /dev/null
+++ b/Tests/TachikomaTests/TachikomaCoreTests.swift
@@ -0,0 +1,507 @@
+import Foundation
+import Testing
+@testable import Tachikoma
+
+@Suite("Tachikoma Core Tests")
+struct TachikomaCoreTests {
+    @Test("Tachikoma singleton initialization")
+    func singletonInitialization() async throws {
+        let tachikoma1 = Tachikoma.shared
+        let tachikoma2 = Tachikoma.shared
+        
+        // Should be the same instance
+        #expect(tachikoma1 === tachikoma2)
+    }
+
+    @Test("Model registration and retrieval")
+    func modelRegistrationAndRetrieval() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register a test model
+        await tachikoma.registerModel(name: "test-model", factory: {
+            OpenAIModel(apiKey: "test-key", modelName: "gpt-4.1")
+        })
+
+        // Should be able to retrieve it
+        do {
+            let model = try await tachikoma.getModel("test-model")
+            #expect(model is OpenAIModel)
+        } catch {
+            Issue.record("Failed to retrieve registered model: \(error)")
+        }
+    }
+
+    @Test("Model not found error")
+    func modelNotFoundError() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Should throw error for non-existent model
+        do {
+            _ = try await tachikoma.getModel("nonexistent-model")
+            Issue.record("Expected error for nonexistent model")
+        } catch let error as TachikomaError {
+            switch error {
+            case .modelNotFound:
+                // Expected
+                break
+            default:
+                Issue.record("Expected modelNotFound error, got: \(error)")
+            }
+        }
+    }
+
+    @Test("Provider configuration")
+    func providerConfiguration() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Test OpenAI configuration
+        let openaiConfig = ProviderConfiguration.OpenAI(
+            apiKey: "test-key",
+            baseURL: URL(string: "https://api.openai.com/v1")!
+        )
+        await tachikoma.configureOpenAI(openaiConfig)
+
+        // Test Anthropic configuration
+        let anthropicConfig = ProviderConfiguration.Anthropic(
+            apiKey: "test-key",
+            baseURL: URL(string: "https://api.anthropic.com/v1")!
+        )
+        await tachikoma.configureAnthropic(anthropicConfig)
+
+        // Test Grok configuration
+        let grokConfig = ProviderConfiguration.Grok(
+            apiKey: "test-key",
+            baseURL: URL(string: "https://api.x.ai/v1")!
+        )
+        await tachikoma.configureGrok(grokConfig)
+
+        // Test Ollama configuration
+        let ollamaConfig = ProviderConfiguration.Ollama(
+            baseURL: URL(string: "http://localhost:11434")!
+        )
+        await tachikoma.configureOllama(ollamaConfig)
+    }
+
+    @Test("Model factory functions")
+    func modelFactoryFunctions() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Test that factory functions work correctly
+        await tachikoma.registerModel(name: "factory-openai", factory: {
+            OpenAIModel(apiKey: "test-key", modelName: "gpt-4.1")
+        })
+
+        await tachikoma.registerModel(name: "factory-anthropic", factory: {
+            AnthropicModel(apiKey: "test-key", modelName: "claude-opus-4-20250514")
+        })
+
+        await tachikoma.registerModel(name: "factory-grok", factory: {
+            GrokModel(apiKey: "test-key", modelName: "grok-4")
+        })
+
+        await tachikoma.registerModel(name: "factory-ollama", factory: {
+            OllamaModel(modelName: "llama3.3")
+        })
+
+        // Test retrieval
+        let modelNames = ["factory-openai", "factory-anthropic", "factory-grok", "factory-ollama"]
+        
+        for modelName in modelNames {
+            do {
+                let model = try await tachikoma.getModel(modelName)
+                #expect(model is any ModelInterface)
+            } catch {
+                Issue.record("Failed to get \(modelName): \(error)")
+            }
+        }
+    }
+
+    @Test("Concurrent model access")
+    func concurrentModelAccess() async throws {
+        let tachikoma = Tachikoma.shared
+
+        // Register a model
+        await tachikoma.registerModel(name: "concurrent-test", factory: {
+            OpenAIModel(apiKey: "test-key", modelName: "gpt-4.1")
+        })
+
+        // Access it concurrently
+        await withTaskGroup(of: Void.self) { group in
+            for i in 0..<10 {
+                group.addTask {
+                    do {
+                        let model = try await tachikoma.getModel("concurrent-test")
+                        #expect(model is OpenAIModel)
+                    } catch {
+                        Issue.record("Concurrent access failed for iteration \(i): \(error)")
+                    }
+                }
+            }
+        }
+    }
+}
+
+// MARK: - Message Type Tests
+
+@Suite("Message Type Tests")
+struct MessageTypeTests {
+    @Test("System message creation")
+    func systemMessageCreation() {
+        let message = Message.system(content: "You are a helpful assistant.")
+        
+        if case let .system(id, content) = message {
+            #expect(id == nil)
+            #expect(content == "You are a helpful assistant.")
+        } else {
+            Issue.record("Expected system message")
+        }
+    }
+
+    @Test("User message with text content")
+    func userMessageWithTextContent() {
+        let message = Message.user(content: .text("Hello, AI!"))
+        
+        if case let .user(id, content) = message {
+            #expect(id == nil)
+            if case let .text(text) = content {
+                #expect(text == "Hello, AI!")
+            } else {
+                Issue.record("Expected text content")
+            }
+        } else {
+            Issue.record("Expected user message")
+        }
+    }
+
+    @Test("User message with multimodal content")
+    func userMessageWithMultimodalContent() {
+        let imageData = Data([0xFF, 0xD8, 0xFF])
+        let message = Message.user(content: .multimodal([
+            .text("What's in this image?"),
+            .imageUrl(ImageUrl(base64: imageData.base64EncodedString()))
+        ]))
+        
+        if case let .user(_, content) = message {
+            if case let .multimodal(parts) = content {
+                #expect(parts.count == 2)
+                
+                if case let .text(text) = parts[0] {
+                    #expect(text == "What's in this image?")
+                } else {
+                    Issue.record("Expected text part at index 0")
+                }
+                
+                if case .imageUrl = parts[1] {
+                    // Expected image part
+                } else {
+                    Issue.record("Expected image part at index 1")
+                }
+            } else {
+                Issue.record("Expected multimodal content")
+            }
+        } else {
+            Issue.record("Expected user message")
+        }
+    }
+
+    @Test("Assistant message creation")
+    func assistantMessageCreation() {
+        let message = Message.assistant(content: [
+            .outputText("Hello! How can I help you?")
+        ])
+        
+        if case let .assistant(id, content, status) = message {
+            #expect(id == nil)
+            #expect(status == .completed)
+            #expect(content.count == 1)
+            
+            if case let .outputText(text) = content[0] {
+                #expect(text == "Hello! How can I help you?")
+            } else {
+                Issue.record("Expected output text content")
+            }
+        } else {
+            Issue.record("Expected assistant message")
+        }
+    }
+
+    @Test("Tool call message")
+    func toolCallMessage() {
+        let toolCall = ToolCallItem(
+            id: "call_123",
+            type: .function,
+            function: FunctionCall(
+                name: "get_weather",
+                arguments: "{\"location\": \"San Francisco\"}"
+            )
+        )
+        
+        let message = Message.assistant(content: [.toolCall(toolCall)])
+        
+        if case let .assistant(_, content, _) = message {
+            if case let .toolCall(call) = content[0] {
+                #expect(call.id == "call_123")
+                #expect(call.function.name == "get_weather")
+                #expect(call.function.arguments == "{\"location\": \"San Francisco\"}")
+            } else {
+                Issue.record("Expected tool call content")
+            }
+        } else {
+            Issue.record("Expected assistant message")
+        }
+    }
+
+    @Test("Tool result message")
+    func toolResultMessage() {
+        let message = Message.tool(
+            toolCallId: "call_123",
+            content: "The weather in San Francisco is 72°F and sunny."
+        )
+        
+        if case let .tool(id, toolCallId, content) = message {
+            #expect(id == nil)
+            #expect(toolCallId == "call_123")
+            #expect(content == "The weather in San Francisco is 72°F and sunny.")
+        } else {
+            Issue.record("Expected tool message")
+        }
+    }
+
+    @Test("Reasoning message")
+    func reasoningMessage() {
+        let message = Message.reasoning(content: "Let me think about this step by step...")
+        
+        if case let .reasoning(id, content) = message {
+            #expect(id == nil)
+            #expect(content == "Let me think about this step by step...")
+        } else {
+            Issue.record("Expected reasoning message")
+        }
+    }
+
+    @Test("Message with custom ID")
+    func messageWithCustomID() {
+        let message = Message.user(id: "custom-123", content: .text("Hello"))
+        
+        if case let .user(id, _) = message {
+            #expect(id == "custom-123")
+        } else {
+            Issue.record("Expected user message with custom ID")
+        }
+    }
+
+    @Test("Message type property")
+    func messageTypeProperty() {
+        let messages: [Message] = [
+            .system(content: "System"),
+            .user(content: .text("User")),
+            .assistant(content: [.outputText("Assistant")]),
+            .tool(toolCallId: "call", content: "Tool"),
+            .reasoning(content: "Reasoning")
+        ]
+        
+        let expectedTypes: [MessageType] = [.system, .user, .assistant, .tool, .reasoning]
+        
+        for (message, expectedType) in zip(messages, expectedTypes) {
+            #expect(message.type == expectedType)
+        }
+    }
+}
+
+// MARK: - MessageContent Tests
+
+@Suite("MessageContent Tests")
+struct MessageContentTests {
+    @Test("Text content")
+    func textContent() {
+        let content = MessageContent.text("Hello, world!")
+        
+        if case let .text(text) = content {
+            #expect(text == "Hello, world!")
+        } else {
+            Issue.record("Expected text content")
+        }
+    }
+
+    @Test("Image content with base64")
+    func imageContentWithBase64() {
+        let imageData = Data([0xFF, 0xD8, 0xFF])
+        let imageUrl = ImageUrl(base64: imageData.base64EncodedString())
+        let content = MessageContent.image(imageUrl)
+        
+        if case let .image(url) = content {
+            #expect(url.base64 == imageData.base64EncodedString())
+            #expect(url.url == nil)
+        } else {
+            Issue.record("Expected image content")
+        }
+    }
+
+    @Test("Image content with URL")
+    func imageContentWithURL() {
+        let imageUrl = ImageUrl(url: "https://example.com/image.jpg")
+        let content = MessageContent.image(imageUrl)
+        
+        if case let .image(url) = content {
+            #expect(url.url == "https://example.com/image.jpg")
+            #expect(url.base64 == nil)
+        } else {
+            Issue.record("Expected image content")
+        }
+    }
+
+    @Test("Audio content")
+    func audioContent() {
+        let audioData = AudioContent(
+            transcript: "Hello, this is a test.",
+            duration: 5.0
+        )
+        let content = MessageContent.audio(audioData)
+        
+        if case let .audio(audio) = content {
+            #expect(audio.transcript == "Hello, this is a test.")
+            #expect(audio.duration == 5.0)
+        } else {
+            Issue.record("Expected audio content")
+        }
+    }
+
+    @Test("File content")
+    func fileContent() {
+        let fileData = FileContent(
+            filename: "test.txt",
+            content: "File content here",
+            mimeType: "text/plain"
+        )
+        let content = MessageContent.file(fileData)
+        
+        if case let .file(file) = content {
+            #expect(file.filename == "test.txt")
+            #expect(file.content == "File content here")
+            #expect(file.mimeType == "text/plain")
+        } else {
+            Issue.record("Expected file content")
+        }
+    }
+
+    @Test("Multimodal content")
+    func multimodalContent() {
+        let parts: [MessageContentPart] = [
+            .text("Describe this image:"),
+            .imageUrl(ImageUrl(url: "https://example.com/image.jpg")),
+            .text("What do you see?")
+        ]
+        let content = MessageContent.multimodal(parts)
+        
+        if case let .multimodal(contentParts) = content {
+            #expect(contentParts.count == 3)
+            
+            #expect(contentParts[0].type == "text")
+            #expect(contentParts[0].text == "Describe this image:")
+            
+            #expect(contentParts[1].type == "image")
+            #expect(contentParts[1].imageUrl != nil)
+            
+            #expect(contentParts[2].type == "text")
+            #expect(contentParts[2].text == "What do you see?")
+        } else {
+            Issue.record("Expected multimodal content")
+        }
+    }
+}
+
+// MARK: - Error Handling Tests
+
+@Suite("Error Handling Tests")
+struct ErrorHandlingTests {
+    @Test("TachikomaError cases")
+    func tachikomaErrorCases() {
+        let errors: [TachikomaError] = [
+            .modelNotFound("test-model"),
+            .invalidRequest("Invalid parameters"),
+            .authenticationFailed,
+            .apiError(message: "Rate limit exceeded", code: "429"),
+            .networkError(underlying: URLError(.notConnectedToInternet)),
+            .configurationError("Missing configuration"),
+            .streamingError("Stream interrupted"),
+        ]
+        
+        // Verify all error cases can be created
+        #expect(errors.count == 9)
+        
+        // Test error descriptions
+        for error in errors {
+            let description = error.localizedDescription
+            #expect(!description.isEmpty)
+        }
+    }
+
+    @Test("Error equality")
+    func errorEquality() {
+        let error1 = TachikomaError.modelNotFound("test")
+        let error2 = TachikomaError.modelNotFound("test")
+        let error3 = TachikomaError.modelNotFound("different")
+        
+        #expect(error1.localizedDescription == error2.localizedDescription)
+        #expect(error1.localizedDescription != error3.localizedDescription)
+    }
+}
+
+// MARK: - Model Settings Tests
+
+@Suite("Model Settings Tests")
+struct ModelSettingsTests {
+    @Test("Default model settings")
+    func defaultModelSettings() {
+        let settings = ModelSettings(modelName: "test-model")
+        
+        #expect(settings.modelName == "test-model")
+        #expect(settings.temperature == nil)
+        #expect(settings.maxTokens == nil)
+        #expect(settings.topP == nil)
+        #expect(settings.frequencyPenalty == nil)
+        #expect(settings.presencePenalty == nil)
+        #expect(settings.stopSequences == nil)
+        #expect(settings.seed == nil)
+        #expect(settings.toolChoice == nil)
+        #expect(settings.parallelToolCalls == nil)
+        #expect(settings.additionalParameters == nil)
+    }
+
+    @Test("Custom model settings")
+    func customModelSettings() {
+        var additionalParams = ModelParameters()
+        additionalParams.set("apiType", value: "chat")
+        additionalParams.set("reasoningEffort", value: "medium")
+        additionalParams.set("reasoning", value: ["summary": "detailed"])
+        additionalParams.set("logprobs", value: true)
+        additionalParams.set("topLogprobs", value: 5)
+        
+        let settings = ModelSettings(
+            modelName: "test-model",
+            temperature: 0.7,
+            topP: 0.9,
+            maxTokens: 1000,
+            frequencyPenalty: 0.1,
+            presencePenalty: 0.2,
+            stopSequences: ["STOP"],
+            toolChoice: .auto,
+            parallelToolCalls: true,
+            seed: 42,
+            additionalParameters: additionalParams
+        )
+        
+        #expect(settings.modelName == "test-model")
+        #expect(settings.temperature == 0.7)
+        #expect(settings.maxTokens == 1000)
+        #expect(settings.topP == 0.9)
+        #expect(settings.frequencyPenalty == 0.1)
+        #expect(settings.presencePenalty == 0.2)
+        #expect(settings.stopSequences == ["STOP"])
+        #expect(settings.seed == 42)
+        #expect(settings.toolChoice == .auto)
+        #expect(settings.parallelToolCalls == true)
+        #expect(settings.additionalParameters?.get("apiType") as? String == "chat")
+        #expect(settings.additionalParameters?.get("reasoningEffort") as? String == "medium")
+    }
+}
\ No newline at end of file
diff --git a/assets/logo.png b/assets/logo.png
new file mode 100644
index 0000000..6681c8e
Binary files /dev/null and b/assets/logo.png differ