diff --git a/app/DevelopmentService.main.ts b/app/DevelopmentService.main.ts
new file mode 100644
index 000000000..9fb7fb004
--- /dev/null
+++ b/app/DevelopmentService.main.ts
@@ -0,0 +1,37 @@
+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { join } from 'node:path';
+import { pathToFileURL } from 'node:url';
+import { protocol, net } from 'electron';
+
+import { isPathInside } from '../ts/util/isPathInside.node.ts';
+import { getAppRootDir } from '../ts/util/appRootDir.main.ts';
+
+type DevelopmentServiceOptions = Readonly<{
+  isDevelopment: boolean;
+}>;
+
+export function start({ isDevelopment }: DevelopmentServiceOptions): void {
+  if (!isDevelopment) {
+    protocol.handle('bundles', () => {
+      return new Response('Unavailable in production', {
+        status: 404,
+      });
+    });
+    return;
+  }
+
+  const BUNDLES_DIR = join(getAppRootDir(), 'bundles');
+
+  // Serve source maps
+  protocol.handle('bundles', req => {
+    const url = new URL(req.url);
+    const path = join(BUNDLES_DIR, url.pathname.slice(1));
+    if (!isPathInside(path, BUNDLES_DIR)) {
+      throw new Error(`Invalid source map request: ${path}`);
+    }
+
+    return net.fetch(pathToFileURL(path).toString());
+  });
+}
diff --git a/app/main.main.ts b/app/main.main.ts
index 14f745f95..1a59da22a 100644
--- a/app/main.main.ts
+++ b/app/main.main.ts
@@ -86,6 +86,7 @@ import { SystemTraySettingCache } from './SystemTraySettingCache.node.ts';
 import { OptionalResourceService } from './OptionalResourceService.main.ts';
 import { EmojiService } from './EmojiService.main.ts';
 import { AssetService } from './AssetService.main.ts';
+import * as DevelopmentService from './DevelopmentService.main.ts';
 import {
   SystemTraySetting,
   shouldMinimizeToSystemTray,
@@ -2092,6 +2093,9 @@ app.on('ready', async () => {
   );
   await EmojiService.create(resourceService);
   AssetService.create(resourceService);
+  DevelopmentService.start({
+    isDevelopment: development && !app.isPackaged,
+  });
 
   if (!resolvedTranslationsLocale) {
     preferredSystemLocales = resolveCanonicalLocales(
diff --git a/background.html b/background.html
index fc503312d..1f3925040 100644
--- a/background.html
+++ b/background.html
@@ -16,7 +16,7 @@
       http-equiv="Content-Security-Policy"
       content="default-src 'none';
             child-src 'self';
-            connect-src 'self' https: wss: attachment:;
+            connect-src 'self' https: wss: attachment: bundles:;
             font-src 'self' asset:;
             form-action 'self';
             frame-src 'none';
diff --git a/preload.wrapper.ts b/preload.wrapper.ts
index d05df1d67..bc3e12f37 100644
--- a/preload.wrapper.ts
+++ b/preload.wrapper.ts
@@ -23,7 +23,7 @@ try {
   }
 }
 
-const source = readFileSync(srcPath);
+const source = readFileSync(srcPath, 'utf8');
 
 window.preloadCompileStartTime = Date.now();
 
@@ -38,27 +38,22 @@ window.preloadCompileStartTime = Date.now();
 // path-independent value for reproducibility, and otherwise use full absolute
 // path in the packaged app.
 const filename = process.env.GENERATE_PRELOAD_CACHE
-  ? 'preload.bundle.js'
+  ? 'bundles/preload/main.js'
   : srcPath;
 
-const script = new Script(
-  `(function(require, __dirname, exports){${source.toString()}})`,
-  {
-    filename,
-    lineOffset: 0,
-    cachedData,
-    importModuleDynamically: constants.USE_MAIN_CONTEXT_DEFAULT_LOADER,
-  }
-);
+// Note: we wrap with (function(require, __dirname, exports){}) in
+// `rolldown.config.ts` to preserve correct offsets in the sourcemap.
+const script = new Script(source, {
+  filename,
+  lineOffset: 0,
+  cachedData,
+  importModuleDynamically: constants.USE_MAIN_CONTEXT_DEFAULT_LOADER,
+});
 
 const { cachedDataRejected } = script;
 
 const fn = script.runInThisContext({
-  filename,
-  lineOffset: 0,
-  columnOffset: 0,
   displayErrors: true,
-  importModuleDynamically: constants.USE_MAIN_CONTEXT_DEFAULT_LOADER,
 });
 
 // See `scripts/generate-preload-cache.mjs`
diff --git a/rolldown.config.ts b/rolldown.config.ts
index d77649e8e..9fc5fb268 100644
--- a/rolldown.config.ts
+++ b/rolldown.config.ts
@@ -72,7 +72,7 @@ const defaults = {
   plugins: [
     {
       name: 'NODE_ENV',
-      async transform(code, id) {
+      transform(code, id) {
         if (id.endsWith('.json')) {
           return;
         }
@@ -82,13 +82,12 @@ const defaults = {
           return;
         }
 
-        const { code: newCode } = await transform(id, code, {
+        return transform(id, code, {
           define: {
             'process.env.NODE_ENV': isProd ? '"production"' : '"development"',
           },
+          sourcemap: !isProd,
         });
-
-        return { code: newCode };
       },
     },
   ],
@@ -101,6 +100,28 @@ const defaults = {
     generatedCode: {
       symbols: false,
     },
+    sourcemap: !isProd,
+    sourcemapBaseUrl: 'bundles:///',
+    postBanner: ({ fileName }) => {
+      // See preload.wrapper.ts
+      if (fileName === 'preload/main.js') {
+        return '(function(require, __dirname, exports){';
+      }
+
+      return '';
+    },
+    postFooter: ({ fileName }) => {
+      const lines = new Array<string>();
+
+      // See preload.wrapper.ts
+      if (fileName === 'preload/main.js') {
+        lines.push('})');
+      }
+
+      lines.push(`//# sourceURL=bundles:///${fileName}`);
+
+      return lines.join('\n');
+    },
   },
   watch: {
     clearScreen: false,