diff --git a/src/browser/App.tsx b/src/browser/App.tsx
index 8ab4af27d..0532df137 100644
--- a/src/browser/App.tsx
+++ b/src/browser/App.tsx
@@ -486,6 +486,14 @@ function AppInner() {
   // Handle keyboard shortcuts
   useEffect(() => {
     const handleKeyDown = (e: KeyboardEvent) => {
+      // DEBUG: Log Cmd+Q presses to diagnose menu accelerator issues
+      if (e.metaKey && e.key.toLowerCase() === "q") {
+        console.log("[App] Cmd+Q detected in renderer", {
+          key: e.key,
+          metaKey: e.metaKey,
+          defaultPrevented: e.defaultPrevented,
+        });
+      }
       if (matchesKeybind(e, KEYBINDS.NEXT_WORKSPACE)) {
         e.preventDefault();
         handleNavigateWorkspace("next");
diff --git a/src/browser/contexts/ProviderOptionsContext.tsx b/src/browser/contexts/ProviderOptionsContext.tsx
index 148bb09aa..fbd02bb67 100644
--- a/src/browser/contexts/ProviderOptionsContext.tsx
+++ b/src/browser/contexts/ProviderOptionsContext.tsx
@@ -1,5 +1,9 @@
-import React, { createContext, useContext } from "react";
-import { usePersistedState } from "@/browser/hooks/usePersistedState";
+import React, { createContext, useContext, useLayoutEffect } from "react";
+import {
+  readPersistedState,
+  updatePersistedState,
+  usePersistedState,
+} from "@/browser/hooks/usePersistedState";
 import type { MuxProviderOptions } from "@/common/types/providerOptions";
 
 interface ProviderOptionsContextType {
@@ -11,6 +15,10 @@ interface ProviderOptionsContextType {
 
 const ProviderOptionsContext = createContext<ProviderOptionsContextType | undefined>(undefined);
 
+const OPENAI_OPTIONS_KEY = "provider_options_openai";
+// One-time migration key: force disableAutoTruncation to true for existing users
+const OPENAI_TRUNCATION_MIGRATION_KEY = "provider_options_openai_truncation_migrated";
+
 export function ProviderOptionsProvider({ children }: { children: React.ReactNode }) {
   const [anthropicOptions, setAnthropicOptions] = usePersistedState<
     MuxProviderOptions["anthropic"]
@@ -19,12 +27,20 @@ export function ProviderOptionsProvider({ children }: { children: React.ReactNod
   });
 
   const [openaiOptions, setOpenAIOptions] = usePersistedState<MuxProviderOptions["openai"]>(
-    "provider_options_openai",
-    {
-      disableAutoTruncation: false,
-    }
+    OPENAI_OPTIONS_KEY,
+    { disableAutoTruncation: true }
   );
 
+  // One-time migration: force disableAutoTruncation to true for existing users
+  useLayoutEffect(() => {
+    const alreadyMigrated = readPersistedState<boolean>(OPENAI_TRUNCATION_MIGRATION_KEY, false);
+    if (alreadyMigrated) {
+      return;
+    }
+    updatePersistedState(OPENAI_OPTIONS_KEY, { disableAutoTruncation: true });
+    updatePersistedState(OPENAI_TRUNCATION_MIGRATION_KEY, true);
+  }, []);
+
   const [googleOptions, setGoogleOptions] = usePersistedState<MuxProviderOptions["google"]>(
     "provider_options_google",
     {}
diff --git a/src/browser/utils/messages/sendOptions.ts b/src/browser/utils/messages/sendOptions.ts
index 30e6c1b0b..685952ce8 100644
--- a/src/browser/utils/messages/sendOptions.ts
+++ b/src/browser/utils/messages/sendOptions.ts
@@ -26,7 +26,7 @@ function getProviderOptions(): MuxProviderOptions {
     { use1MContext: false }
   );
   const openai = readPersistedState<MuxProviderOptions["openai"]>("provider_options_openai", {
-    disableAutoTruncation: false,
+    disableAutoTruncation: true,
   });
   const google = readPersistedState<MuxProviderOptions["google"]>("provider_options_google", {});
 
diff --git a/src/desktop/main.ts b/src/desktop/main.ts
index 34505e0d0..9155ecc48 100644
--- a/src/desktop/main.ts
+++ b/src/desktop/main.ts
@@ -143,6 +143,13 @@ function timestamp(): string {
 
 function createMenu() {
   const template: MenuItemConstructorOptions[] = [
+    {
+      label: "File",
+      submenu:
+        process.platform === "darwin"
+          ? [{ role: "close" }] // macOS: Cmd+W to close window
+          : [{ role: "quit" }], // Windows/Linux: Quit in File menu
+    },
     {
       label: "Edit",
       submenu: [
@@ -182,7 +189,14 @@ function createMenu() {
     },
     {
       label: "Window",
-      submenu: [{ role: "minimize" }, { role: "close" }],
+      submenu:
+        process.platform === "darwin"
+          ? [
+              // macOS Window menu - close is in File menu to avoid Cmd+Q/Cmd+W conflicts
+              { role: "minimize" },
+              { role: "zoom" },
+            ]
+          : [{ role: "minimize" }, { role: "close" }],
     },
   ];
 
@@ -206,7 +220,12 @@ function createMenu() {
         { role: "hideOthers" },
         { role: "unhide" },
         { type: "separator" },
-        { role: "quit" },
+        {
+          role: "quit",
+          click: () => {
+            console.log(`[${timestamp()}] Quit menu item clicked`);
+          },
+        },
       ],
     });
   }
@@ -504,7 +523,13 @@ function createWindow() {
     // First token count will use approximation, accurate count caches in background.
   });
 
+  // Log when window is about to close (can be prevented)
+  mainWindow.on("close", (event) => {
+    console.log(`[${timestamp()}] mainWindow 'close' event fired`);
+  });
+
   mainWindow.on("closed", () => {
+    console.log(`[${timestamp()}] mainWindow 'closed' event fired`);
     mainWindow = null;
   });
 }
@@ -573,12 +598,15 @@ if (gotTheLock) {
   let isDisposing = false;
 
   app.on("before-quit", (event) => {
+    console.log(`[${timestamp()}] app 'before-quit' event fired (isDisposing=${isDisposing}, hasServices=${!!services})`);
     // Skip if already disposing or no services to clean up
     if (isDisposing || !services) {
+      console.log(`[${timestamp()}] before-quit: skipping (already disposing or no services)`);
       return;
     }
 
     // Prevent quit, clean up, then quit again
+    console.log(`[${timestamp()}] before-quit: preventing quit, starting disposal`);
     event.preventDefault();
     isDisposing = true;
 
@@ -594,6 +622,7 @@ if (gotTheLock) {
   });
 
   app.on("window-all-closed", () => {
+    console.log(`[${timestamp()}] app 'window-all-closed' event fired (platform=${process.platform})`);
     if (process.platform !== "darwin") {
       app.quit();
     }
diff --git a/tests/ipc/sendMessage.heavy.test.ts b/tests/ipc/sendMessage.heavy.test.ts
index dcf9d8363..41228daca 100644
--- a/tests/ipc/sendMessage.heavy.test.ts
+++ b/tests/ipc/sendMessage.heavy.test.ts
@@ -41,13 +41,21 @@ describeIntegration("sendMessage heavy/load tests", () => {
         await withSharedWorkspace(provider, async ({ env, workspaceId, collector }) => {
           // Build up large conversation history to exceed context limit
           // This approach is model-agnostic - it keeps sending until we've built up enough history
+          // Use auto-truncation enabled (disableAutoTruncation: false) so history builds up successfully
           const largeMessage = "x".repeat(50_000);
           for (let i = 0; i < 10; i++) {
             await sendMessageWithModel(
               env,
               workspaceId,
               `Message ${i}: ${largeMessage}`,
-              modelString(provider, model)
+              modelString(provider, model),
+              {
+                providerOptions: {
+                  openai: {
+                    disableAutoTruncation: false,
+                  },
+                },
+              }
             );
             await collector.waitForEvent("stream-end", 30000);
             collector.clear();
@@ -93,8 +101,14 @@ describeIntegration("sendMessage heavy/load tests", () => {
             env,
             workspaceId,
             "This should succeed with auto-truncation",
-            modelString(provider, model)
-            // disableAutoTruncation defaults to false (auto-truncation enabled)
+            modelString(provider, model),
+            {
+              providerOptions: {
+                openai: {
+                  disableAutoTruncation: false,
+                },
+              },
+            }
           );
 
           expect(successResult.success).toBe(true);