diff --git a/Signal/AppLaunch/AppDelegate.swift b/Signal/AppLaunch/AppDelegate.swift
index 1c17bb9398..f02a715a74 100644
--- a/Signal/AppLaunch/AppDelegate.swift
+++ b/Signal/AppLaunch/AppDelegate.swift
@@ -100,6 +100,12 @@ final class AppDelegate: UIResponder, UIApplicationDelegate {
 
         // Ensure that all windows have the correct frame.
         WindowManager.shared.updateWindowFrames()
+
+        AppReadiness.runNowOrWhenMainAppDidBecomeReadyAsync {
+            self.incrementalMessageTSAttachmentMigrator?.runInMainAppBackgroundIfNeeded(
+                databaseStorage: self.databaseStorage
+            )
+        }
     }
 
     private let flushQueue = DispatchQueue(label: "org.signal.flush", qos: .utility)
diff --git a/Signal/src/IncrementalMessageTSAttachmentMigrator.swift b/Signal/src/IncrementalMessageTSAttachmentMigrator.swift
index b87cd3964e..b5713cb85f 100644
--- a/Signal/src/IncrementalMessageTSAttachmentMigrator.swift
+++ b/Signal/src/IncrementalMessageTSAttachmentMigrator.swift
@@ -125,6 +125,11 @@ extension IncrementalMessageTSAttachmentMigrator {
             return
         case .started:
             // Don't _start_ in the main app, but continue making progress if we already started.
+
+            if isRunningInMainApp.get() {
+                return
+            }
+
             Logger.info("Continuing migration in main app")
             Task {
                 await runInMainAppBackground()
@@ -135,8 +140,19 @@ extension IncrementalMessageTSAttachmentMigrator {
     private func runInMainAppBackground() async {
         var batchCount = 0
         var didFinish = false
+        isRunningInMainApp.set(true)
+        defer {
+            isRunningInMainApp.set(false)
+        }
         while !didFinish {
             do {
+                guard CurrentAppContext().isMainAppAndActive else {
+                    // If the main app goes into the background, we shouldn't be
+                    // grabbing the sql write lock. Stop.
+                    Logger.info("Stopping when backgrounding app")
+                    return
+                }
+
                 // Add a small delay between each batch to avoid locking the db write queue.
                 try await Task.sleep(nanoseconds: 300 * NSEC_PER_MSEC)
 
diff --git a/SignalServiceKit/Storage/Database/IncrementalMigrations/TSAttachment/IncrementalTSAttachmentMigrator.swift b/SignalServiceKit/Storage/Database/IncrementalMigrations/TSAttachment/IncrementalTSAttachmentMigrator.swift
index 3522cd35dd..c83fac0f38 100644
--- a/SignalServiceKit/Storage/Database/IncrementalMigrations/TSAttachment/IncrementalTSAttachmentMigrator.swift
+++ b/SignalServiceKit/Storage/Database/IncrementalMigrations/TSAttachment/IncrementalTSAttachmentMigrator.swift
@@ -12,6 +12,8 @@ public protocol IncrementalMessageTSAttachmentMigrator {
 
     // Returns true if done.
     func runNextBatch() async throws -> Bool
+
+    var isRunningInMainApp: AtomicBool { get }
 }
 
 public class IncrementalMessageTSAttachmentMigratorImpl: IncrementalMessageTSAttachmentMigrator {
@@ -20,6 +22,8 @@ public class IncrementalMessageTSAttachmentMigratorImpl: IncrementalMessageTSAtt
 
     private let databaseStorage: SDSDatabaseStorage
 
+    public let isRunningInMainApp = AtomicBool(false, lock: .init())
+
     public init(databaseStorage: SDSDatabaseStorage) {
         self.databaseStorage = databaseStorage
 
@@ -100,6 +104,8 @@ public class IncrementalMessageTSAttachmentMigratorImpl: IncrementalMessageTSAtt
 public class NoOpIncrementalMessageTSAttachmentMigrator: IncrementalMessageTSAttachmentMigrator {
     public init() {}
 
+    public let isRunningInMainApp = AtomicBool(false, lock: .init())
+
     public func runUntilFinished() async {}
 
     // Returns true if done.
@@ -114,6 +120,8 @@ public class IncrementalMessageTSAttachmentMigratorMock: IncrementalMessageTSAtt
 
     public init() {}
 
+    public let isRunningInMainApp = AtomicBool(false, lock: .init())
+
     public func runUntilFinished() async {}
 
     // Returns true if done.