diff --git a/auto-claude-ui/package.json b/auto-claude-ui/package.json
index 437e249d..dc802097 100644
--- a/auto-claude-ui/package.json
+++ b/auto-claude-ui/package.json
@@ -1,6 +1,6 @@
 {
   "name": "auto-claude-ui",
-  "version": "2.5.6",
+  "version": "2.6.0",
   "description": "Desktop UI for Auto Claude autonomous coding framework",
   "main": "./out/main/index.js",
   "author": "Auto Claude Team",
diff --git a/auto-claude-ui/src/main/ipc-handlers/github/__tests__/oauth-handlers.spec.ts b/auto-claude-ui/src/main/ipc-handlers/github/__tests__/oauth-handlers.spec.ts
new file mode 100644
index 00000000..6ff4db97
--- /dev/null
+++ b/auto-claude-ui/src/main/ipc-handlers/github/__tests__/oauth-handlers.spec.ts
@@ -0,0 +1,548 @@
+/**
+ * Unit tests for GitHub OAuth handlers
+ * Tests device code parsing, shell.openExternal handling, and error recovery
+ */
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { EventEmitter } from 'events';
+
+// Mock child_process before importing
+const mockSpawn = vi.fn();
+const mockExecSync = vi.fn();
+const mockExecFileSync = vi.fn();
+
+vi.mock('child_process', () => ({
+  spawn: (...args: unknown[]) => mockSpawn(...args),
+  execSync: (...args: unknown[]) => mockExecSync(...args),
+  execFileSync: (...args: unknown[]) => mockExecFileSync(...args)
+}));
+
+// Mock shell.openExternal
+const mockOpenExternal = vi.fn();
+
+vi.mock('electron', () => {
+  const mockIpcMain = new (class extends EventEmitter {
+    private handlers: Map<string, Function> = new Map();
+
+    handle(channel: string, handler: Function): void {
+      this.handlers.set(channel, handler);
+    }
+
+    removeHandler(channel: string): void {
+      this.handlers.delete(channel);
+    }
+
+    async invokeHandler(channel: string, event: unknown, ...args: unknown[]): Promise<unknown> {
+      const handler = this.handlers.get(channel);
+      if (handler) {
+        return handler(event, ...args);
+      }
+      throw new Error(`No handler for channel: ${channel}`);
+    }
+
+    getHandler(channel: string): Function | undefined {
+      return this.handlers.get(channel);
+    }
+  })();
+
+  return {
+    ipcMain: mockIpcMain,
+    shell: {
+      openExternal: (...args: unknown[]) => mockOpenExternal(...args)
+    }
+  };
+});
+
+// Mock @electron-toolkit/utils
+vi.mock('@electron-toolkit/utils', () => ({
+  is: {
+    dev: true,
+    windows: process.platform === 'win32',
+    macos: process.platform === 'darwin',
+    linux: process.platform === 'linux'
+  }
+}));
+
+// Create mock process for spawn
+function createMockProcess(): EventEmitter & {
+  stdout: EventEmitter | null;
+  stderr: EventEmitter | null;
+  stdin: { write: ReturnType<typeof vi.fn>; end: ReturnType<typeof vi.fn> } | null;
+} {
+  const proc = new EventEmitter() as EventEmitter & {
+    stdout: EventEmitter | null;
+    stderr: EventEmitter | null;
+    stdin: { write: ReturnType<typeof vi.fn>; end: ReturnType<typeof vi.fn> } | null;
+  };
+  proc.stdout = new EventEmitter();
+  proc.stderr = new EventEmitter();
+  proc.stdin = { write: vi.fn(), end: vi.fn() };
+  return proc;
+}
+
+describe('GitHub OAuth Handlers', () => {
+  let ipcMain: EventEmitter & {
+    handlers: Map<string, Function>;
+    invokeHandler: (channel: string, event: unknown, ...args: unknown[]) => Promise<unknown>;
+    getHandler: (channel: string) => Function | undefined;
+  };
+
+  beforeEach(async () => {
+    vi.clearAllMocks();
+    vi.resetModules();
+
+    // Get mocked ipcMain
+    const electron = await import('electron');
+    ipcMain = electron.ipcMain as unknown as typeof ipcMain;
+  });
+
+  afterEach(() => {
+    vi.clearAllMocks();
+  });
+
+  describe('Device Code Parsing', () => {
+    it('should parse device code from standard gh CLI output format', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockResolvedValue(undefined);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      // Start the handler
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      // Simulate gh CLI output with device code
+      mockProcess.stderr?.emit('data', '! First copy your one-time code: ABCD-1234\n');
+      mockProcess.stderr?.emit('data', '- Press Enter to open github.com in your browser...\n');
+
+      // Complete the process
+      mockProcess.emit('close', 0);
+
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', true);
+      expect(result).toHaveProperty('data');
+      const data = (result as { data: { deviceCode: string } }).data;
+      expect(data.deviceCode).toBe('ABCD-1234');
+    });
+
+    it('should parse device code from alternate output format (lowercase "code")', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockResolvedValue(undefined);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      // Alternate format: "code: XXXX-XXXX" without "one-time"
+      mockProcess.stderr?.emit('data', 'Enter the code: EFGH-5678\n');
+      mockProcess.emit('close', 0);
+
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { deviceCode: string } }).data;
+      expect(data.deviceCode).toBe('EFGH-5678');
+    });
+
+    it('should parse device code from stdout (not just stderr)', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockResolvedValue(undefined);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      // Device code in stdout instead of stderr
+      mockProcess.stdout?.emit('data', '! First copy your one-time code: IJKL-9012\n');
+      mockProcess.emit('close', 0);
+
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { deviceCode: string } }).data;
+      expect(data.deviceCode).toBe('IJKL-9012');
+    });
+
+    it('should handle output without device code gracefully', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      // Output without device code
+      mockProcess.stderr?.emit('data', 'Some other message\n');
+      mockProcess.emit('close', 0);
+
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { deviceCode?: string } }).data;
+      expect(data.deviceCode).toBeUndefined();
+    });
+
+    it('should extract URL from output containing https://github.com/login/device', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockResolvedValue(undefined);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      mockProcess.stderr?.emit('data', '! First copy your one-time code: MNOP-3456\n');
+      mockProcess.stderr?.emit('data', 'Then visit https://github.com/login/device to authenticate\n');
+      mockProcess.emit('close', 0);
+
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { authUrl: string } }).data;
+      expect(data.authUrl).toBe('https://github.com/login/device');
+    });
+  });
+
+  describe('shell.openExternal Handling', () => {
+    it('should call shell.openExternal with extracted URL when device code found', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockResolvedValue(undefined);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      mockProcess.stderr?.emit('data', '! First copy your one-time code: QRST-7890\n');
+
+      // Wait for next tick to allow async browser opening
+      await new Promise(resolve => setTimeout(resolve, 10));
+
+      mockProcess.emit('close', 0);
+      await resultPromise;
+
+      expect(mockOpenExternal).toHaveBeenCalledWith('https://github.com/login/device');
+    });
+
+    it('should set browserOpened to true when shell.openExternal succeeds', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockResolvedValue(undefined);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      mockProcess.stderr?.emit('data', '! First copy your one-time code: UVWX-1234\n');
+
+      // Wait for async browser opening
+      await new Promise(resolve => setTimeout(resolve, 10));
+
+      mockProcess.emit('close', 0);
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { browserOpened: boolean } }).data;
+      expect(data.browserOpened).toBe(true);
+    });
+
+    it('should set browserOpened to false when shell.openExternal fails', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockRejectedValue(new Error('Failed to open browser'));
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      mockProcess.stderr?.emit('data', '! First copy your one-time code: YZAB-5678\n');
+
+      // Wait for async browser opening to fail
+      await new Promise(resolve => setTimeout(resolve, 10));
+
+      mockProcess.emit('close', 0);
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { browserOpened: boolean } }).data;
+      expect(data.browserOpened).toBe(false);
+    });
+
+    it('should provide fallbackUrl when browser fails to open', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockRejectedValue(new Error('Failed to open browser'));
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      mockProcess.stderr?.emit('data', '! First copy your one-time code: CDEF-9012\n');
+
+      // Wait for async browser opening to fail
+      await new Promise(resolve => setTimeout(resolve, 10));
+
+      mockProcess.emit('close', 0);
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { fallbackUrl?: string } }).data;
+      expect(data.fallbackUrl).toBe('https://github.com/login/device');
+    });
+
+    it('should not provide fallbackUrl when browser opens successfully', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockResolvedValue(undefined);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      mockProcess.stderr?.emit('data', '! First copy your one-time code: GHIJ-3456\n');
+
+      // Wait for async browser opening
+      await new Promise(resolve => setTimeout(resolve, 10));
+
+      mockProcess.emit('close', 0);
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { fallbackUrl?: string } }).data;
+      expect(data.fallbackUrl).toBeUndefined();
+    });
+  });
+
+  describe('Error Handling', () => {
+    it('should handle gh CLI process error', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      // Emit error event
+      mockProcess.emit('error', new Error('spawn gh ENOENT'));
+
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', false);
+      expect(result).toHaveProperty('error', 'spawn gh ENOENT');
+      const data = (result as { data: { fallbackUrl: string } }).data;
+      expect(data.fallbackUrl).toBe('https://github.com/login/device');
+    });
+
+    it('should handle non-zero exit code', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      mockProcess.stderr?.emit('data', 'error: some authentication error\n');
+      mockProcess.emit('close', 1);
+
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', false);
+      const data = (result as { data: { fallbackUrl: string } }).data;
+      expect(data.fallbackUrl).toBe('https://github.com/login/device');
+    });
+
+    it('should include device code in error result if it was extracted before failure', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+      mockOpenExternal.mockResolvedValue(undefined);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      // Device code output followed by failure
+      mockProcess.stderr?.emit('data', '! First copy your one-time code: KLMN-7890\n');
+
+      // Wait for async browser opening
+      await new Promise(resolve => setTimeout(resolve, 10));
+
+      mockProcess.stderr?.emit('data', 'error: authentication failed\n');
+      mockProcess.emit('close', 1);
+
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', false);
+      const data = (result as { data: { deviceCode: string; fallbackUrl: string } }).data;
+      expect(data.deviceCode).toBe('KLMN-7890');
+      expect(data.fallbackUrl).toBe('https://github.com/login/device');
+    });
+
+    it('should provide user-friendly error message on process spawn failure', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      const resultPromise = ipcMain.invokeHandler('github:startAuth', {});
+
+      mockProcess.emit('error', new Error('spawn gh ENOENT'));
+
+      const result = await resultPromise;
+
+      expect(result).toHaveProperty('success', false);
+      const data = (result as { data: { message: string } }).data;
+      expect(data.message).toContain('Failed to start GitHub CLI');
+    });
+  });
+
+  describe('gh CLI Check Handler', () => {
+    it('should return installed: true when gh CLI is found', async () => {
+      mockExecSync.mockImplementation((cmd: string) => {
+        if (cmd.includes('which gh') || cmd.includes('where gh')) {
+          return '/usr/local/bin/gh\n';
+        }
+        if (cmd === 'gh --version') {
+          return 'gh version 2.65.0 (2024-01-15)\n';
+        }
+        return '';
+      });
+
+      const { registerCheckGhCli } = await import('../oauth-handlers');
+      registerCheckGhCli();
+
+      const result = await ipcMain.invokeHandler('github:checkCli', {});
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { installed: boolean; version: string } }).data;
+      expect(data.installed).toBe(true);
+      expect(data.version).toContain('gh version');
+    });
+
+    it('should return installed: false when gh CLI is not found', async () => {
+      mockExecSync.mockImplementation(() => {
+        throw new Error('Command not found');
+      });
+
+      const { registerCheckGhCli } = await import('../oauth-handlers');
+      registerCheckGhCli();
+
+      const result = await ipcMain.invokeHandler('github:checkCli', {});
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { installed: boolean } }).data;
+      expect(data.installed).toBe(false);
+    });
+  });
+
+  describe('gh Auth Check Handler', () => {
+    it('should return authenticated: true with username when logged in', async () => {
+      mockExecSync.mockImplementation((cmd: string) => {
+        if (cmd === 'gh auth status') {
+          return 'Logged in to github.com as testuser\n';
+        }
+        if (cmd === 'gh api user --jq .login') {
+          return 'testuser\n';
+        }
+        return '';
+      });
+
+      const { registerCheckGhAuth } = await import('../oauth-handlers');
+      registerCheckGhAuth();
+
+      const result = await ipcMain.invokeHandler('github:checkAuth', {});
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { authenticated: boolean; username: string } }).data;
+      expect(data.authenticated).toBe(true);
+      expect(data.username).toBe('testuser');
+    });
+
+    it('should return authenticated: false when not logged in', async () => {
+      mockExecSync.mockImplementation(() => {
+        throw new Error('You are not logged into any GitHub hosts');
+      });
+
+      const { registerCheckGhAuth } = await import('../oauth-handlers');
+      registerCheckGhAuth();
+
+      const result = await ipcMain.invokeHandler('github:checkAuth', {});
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: { authenticated: boolean } }).data;
+      expect(data.authenticated).toBe(false);
+    });
+  });
+
+  describe('Spawn Arguments', () => {
+    it('should spawn gh with correct auth login arguments', async () => {
+      const mockProcess = createMockProcess();
+      mockSpawn.mockReturnValue(mockProcess);
+
+      const { registerStartGhAuth } = await import('../oauth-handlers');
+      registerStartGhAuth();
+
+      ipcMain.invokeHandler('github:startAuth', {});
+
+      expect(mockSpawn).toHaveBeenCalledWith(
+        'gh',
+        ['auth', 'login', '--web', '--scopes', 'repo'],
+        expect.objectContaining({
+          stdio: ['pipe', 'pipe', 'pipe']
+        })
+      );
+    });
+  });
+
+  describe('Repository Validation', () => {
+    it('should reject invalid repository format', async () => {
+      const { registerGetGitHubBranches } = await import('../oauth-handlers');
+      registerGetGitHubBranches();
+
+      // Test with injection attempt
+      const result = await ipcMain.invokeHandler(
+        'github:getBranches',
+        {},
+        'owner/repo; rm -rf /',
+        'token'
+      );
+
+      expect(result).toHaveProperty('success', false);
+      expect(result).toHaveProperty('error', 'Invalid repository format. Expected: owner/repo');
+    });
+
+    it('should accept valid repository format', async () => {
+      mockExecFileSync.mockReturnValue('main\nfeature-branch\n');
+
+      const { registerGetGitHubBranches } = await import('../oauth-handlers');
+      registerGetGitHubBranches();
+
+      const result = await ipcMain.invokeHandler(
+        'github:getBranches',
+        {},
+        'valid-owner/valid-repo',
+        'token'
+      );
+
+      expect(result).toHaveProperty('success', true);
+      const data = (result as { data: string[] }).data;
+      expect(data).toContain('main');
+      expect(data).toContain('feature-branch');
+    });
+  });
+});
diff --git a/auto-claude-ui/src/main/ipc-handlers/github/oauth-handlers.ts b/auto-claude-ui/src/main/ipc-handlers/github/oauth-handlers.ts
index 95f19f44..864eb367 100644
--- a/auto-claude-ui/src/main/ipc-handlers/github/oauth-handlers.ts
+++ b/auto-claude-ui/src/main/ipc-handlers/github/oauth-handlers.ts
@@ -3,7 +3,7 @@
  * Provides a simpler OAuth flow than manual PAT creation
  */
 
-import { ipcMain } from 'electron';
+import { ipcMain, shell } from 'electron';
 import { execSync, execFileSync, spawn } from 'child_process';
 import { IPC_CHANNELS } from '../../../shared/constants';
 import type { IPCResult } from '../../../shared/types';
@@ -33,6 +33,64 @@ function isValidGitHubRepo(repo: string): boolean {
   return GITHUB_REPO_PATTERN.test(repo);
 }
 
+// Regex patterns for parsing device code from gh CLI output
+// Expected format: "! First copy your one-time code: XXXX-XXXX"
+const DEVICE_CODE_PATTERN = /(?:one-time code|code):\s*([A-Z0-9]{4}-[A-Z0-9]{4})/i;
+
+// GitHub device flow URL pattern
+const DEVICE_URL_PATTERN = /https:\/\/github\.com\/login\/device/i;
+
+// Default GitHub device flow URL
+const GITHUB_DEVICE_URL = 'https://github.com/login/device';
+
+/**
+ * Parse device code from gh CLI stdout output
+ * Returns the device code (format: XXXX-XXXX) if found, null otherwise
+ */
+function parseDeviceCode(output: string): string | null {
+  const match = output.match(DEVICE_CODE_PATTERN);
+  if (match && match[1]) {
+    debugLog('Parsed device code:', match[1]);
+    return match[1];
+  }
+  return null;
+}
+
+/**
+ * Parse device URL from gh CLI output
+ * Returns the URL if found, or the default GitHub device URL
+ */
+function parseDeviceUrl(output: string): string {
+  const match = output.match(DEVICE_URL_PATTERN);
+  if (match) {
+    debugLog('Found device URL in output:', match[0]);
+    return match[0];
+  }
+  // Default to standard GitHub device flow URL
+  return GITHUB_DEVICE_URL;
+}
+
+/**
+ * Result of parsing device flow output from gh CLI
+ */
+interface DeviceFlowInfo {
+  deviceCode: string | null;
+  authUrl: string;
+}
+
+/**
+ * Parse both device code and URL from combined gh CLI output
+ * Searches through both stdout and stderr as gh may output to either
+ */
+function parseDeviceFlowOutput(stdout: string, stderr: string): DeviceFlowInfo {
+  const combinedOutput = `${stdout}\n${stderr}`;
+
+  return {
+    deviceCode: parseDeviceCode(combinedOutput),
+    authUrl: parseDeviceUrl(combinedOutput)
+  };
+}
+
 /**
  * Check if gh CLI is installed
  */
@@ -114,14 +172,31 @@ export function registerCheckGhAuth(): void {
   );
 }
 
+/**
+ * Result type for GitHub auth start, including device flow information
+ */
+interface GitHubAuthStartResult {
+  success: boolean;
+  message?: string;
+  deviceCode?: string;
+  authUrl?: string;
+  browserOpened?: boolean;
+  /**
+   * Fallback URL provided when browser launch fails.
+   * The frontend should display this URL so users can manually navigate to complete auth.
+   */
+  fallbackUrl?: string;
+}
+
 /**
  * Start GitHub OAuth flow using gh CLI
- * This will open the browser for device flow authentication
+ * This will extract the device code from gh CLI output and open the browser
+ * using Electron's shell.openExternal (bypasses macOS child process restrictions)
  */
 export function registerStartGhAuth(): void {
   ipcMain.handle(
     IPC_CHANNELS.GITHUB_START_AUTH,
-    async (): Promise<IPCResult<{ success: boolean; message?: string }>> => {
+    async (): Promise<IPCResult<GitHubAuthStartResult>> => {
       debugLog('startGitHubAuth handler called');
       return new Promise((resolve) => {
         try {
@@ -135,17 +210,60 @@ export function registerStartGhAuth(): void {
 
           let output = '';
           let errorOutput = '';
+          let deviceCodeExtracted = false;
+          let extractedDeviceCode: string | null = null;
+          let extractedAuthUrl: string = GITHUB_DEVICE_URL;
+          let browserOpenedSuccessfully = false;
+          let extractionInProgress = false;
+
+          // Function to attempt device code extraction and browser opening
+          // Uses mutex pattern to prevent race conditions from concurrent data handlers
+          const tryExtractAndOpenBrowser = async () => {
+            if (deviceCodeExtracted || extractionInProgress) return;
+            extractionInProgress = true;
+
+            const deviceFlowInfo = parseDeviceFlowOutput(output, errorOutput);
+
+            if (deviceFlowInfo.deviceCode) {
+              deviceCodeExtracted = true;
+              extractedDeviceCode = deviceFlowInfo.deviceCode;
+              extractedAuthUrl = deviceFlowInfo.authUrl;
+
+              debugLog('Device code extracted:', extractedDeviceCode);
+              debugLog('Auth URL:', extractedAuthUrl);
+
+              // Open browser using Electron's shell.openExternal
+              // This bypasses macOS child process restrictions that block gh CLI's browser launch
+              try {
+                await shell.openExternal(extractedAuthUrl);
+                browserOpenedSuccessfully = true;
+                debugLog('Browser opened successfully via shell.openExternal');
+              } catch (browserError) {
+                debugLog('Failed to open browser:', browserError instanceof Error ? browserError.message : browserError);
+                browserOpenedSuccessfully = false;
+                // Don't fail here - we'll return the device code so user can manually navigate
+              }
+            } else {
+              // No device code found yet, allow next data chunk to try again
+              extractionInProgress = false;
+            }
+          };
 
           ghProcess.stdout?.on('data', (data) => {
             const chunk = data.toString();
             output += chunk;
             debugLog('gh stdout:', chunk);
+            // Try to extract device code as data comes in
+            // Use void to explicitly ignore promise
+            void tryExtractAndOpenBrowser();
           });
 
           ghProcess.stderr?.on('data', (data) => {
             const chunk = data.toString();
             errorOutput += chunk;
             debugLog('gh stderr:', chunk);
+            // gh often outputs to stderr, so check there too
+            void tryExtractAndOpenBrowser();
           });
 
           ghProcess.on('close', (code) => {
@@ -154,17 +272,39 @@ export function registerStartGhAuth(): void {
             debugLog('Full stderr:', errorOutput);
 
             if (code === 0) {
+              // Success case - include fallbackUrl if browser failed to open
+              // so the user can manually navigate if needed
               resolve({
                 success: true,
                 data: {
                   success: true,
-                  message: 'Successfully authenticated with GitHub'
+                  message: browserOpenedSuccessfully
+                    ? 'Successfully authenticated with GitHub'
+                    : 'Authentication successful. Browser could not be opened automatically.',
+                  deviceCode: extractedDeviceCode || undefined,
+                  authUrl: extractedAuthUrl,
+                  browserOpened: browserOpenedSuccessfully,
+                  // Provide fallback URL when browser failed to open
+                  fallbackUrl: !browserOpenedSuccessfully ? extractedAuthUrl : undefined
                 }
               });
             } else {
+              // Even if auth failed, return device code info if we extracted it
+              // This allows user to retry manually with the fallback URL
+              const fallbackUrlForManualAuth = extractedDeviceCode ? extractedAuthUrl : GITHUB_DEVICE_URL;
+
               resolve({
                 success: false,
-                error: errorOutput || `Authentication failed with exit code ${code}`
+                error: errorOutput || `Authentication failed with exit code ${code}`,
+                data: {
+                  success: false,
+                  deviceCode: extractedDeviceCode || undefined,
+                  authUrl: extractedAuthUrl,
+                  browserOpened: browserOpenedSuccessfully,
+                  // Always provide fallback URL on failure for manual recovery
+                  fallbackUrl: fallbackUrlForManualAuth,
+                  message: 'Authentication failed. Please visit the URL manually to complete authentication.'
+                }
               });
             }
           });
@@ -173,14 +313,28 @@ export function registerStartGhAuth(): void {
             debugLog('gh process error:', error.message);
             resolve({
               success: false,
-              error: error.message
+              error: error.message,
+              data: {
+                success: false,
+                browserOpened: false,
+                // Provide fallback URL so user can attempt manual auth
+                fallbackUrl: GITHUB_DEVICE_URL,
+                message: 'Failed to start GitHub CLI. Please visit the URL manually to authenticate.'
+              }
             });
           });
         } catch (error) {
           debugLog('Exception in startGitHubAuth:', error instanceof Error ? error.message : error);
           resolve({
             success: false,
-            error: error instanceof Error ? error.message : 'Unknown error'
+            error: error instanceof Error ? error.message : 'Unknown error',
+            data: {
+              success: false,
+              browserOpened: false,
+              // Provide fallback URL for manual authentication recovery
+              fallbackUrl: GITHUB_DEVICE_URL,
+              message: 'An unexpected error occurred. Please visit the URL manually to authenticate.'
+            }
           });
         }
       });
diff --git a/auto-claude-ui/src/main/ipc-handlers/settings-handlers.ts b/auto-claude-ui/src/main/ipc-handlers/settings-handlers.ts
index 9297a838..25b1a763 100644
--- a/auto-claude-ui/src/main/ipc-handlers/settings-handlers.ts
+++ b/auto-claude-ui/src/main/ipc-handlers/settings-handlers.ts
@@ -94,7 +94,8 @@ export function registerSettingsHandlers(
   ipcMain.handle(
     IPC_CHANNELS.SETTINGS_GET,
     async (): Promise<IPCResult<AppSettings>> => {
-      let settings = { ...DEFAULT_APP_SETTINGS };
+      let settings: AppSettings = { ...DEFAULT_APP_SETTINGS };
+      let needsSave = false;
 
       if (existsSync(settingsPath)) {
         try {
@@ -105,6 +106,18 @@ export function registerSettingsHandlers(
         }
       }
 
+      // Migration: Set agent profile to 'auto' for users who haven't made a selection (one-time)
+      // This ensures new users get the optimized 'auto' profile as the default
+      // while preserving existing user preferences
+      if (!settings._migratedAgentProfileToAuto) {
+        // Only set 'auto' if user hasn't made a selection yet
+        if (!settings.selectedAgentProfile) {
+          settings.selectedAgentProfile = 'auto';
+        }
+        settings._migratedAgentProfileToAuto = true;
+        needsSave = true;
+      }
+
       // If no manual autoBuildPath is set, try to auto-detect
       if (!settings.autoBuildPath) {
         const detectedPath = detectAutoBuildSourcePath();
@@ -113,6 +126,16 @@ export function registerSettingsHandlers(
         }
       }
 
+      // Persist migration changes
+      if (needsSave) {
+        try {
+          writeFileSync(settingsPath, JSON.stringify(settings, null, 2));
+        } catch (error) {
+          console.error('[SETTINGS_GET] Failed to persist migration:', error);
+          // Continue anyway - settings will be migrated in-memory for this session
+        }
+      }
+
       return { success: true, data: settings as AppSettings };
     }
   );
diff --git a/auto-claude-ui/src/main/ipc-handlers/task/worktree-handlers.ts b/auto-claude-ui/src/main/ipc-handlers/task/worktree-handlers.ts
index acb3a821..a34a7d49 100644
--- a/auto-claude-ui/src/main/ipc-handlers/task/worktree-handlers.ts
+++ b/auto-claude-ui/src/main/ipc-handlers/task/worktree-handlers.ts
@@ -500,6 +500,21 @@ export function registerWorktreeHandlers(
 
               debug('Merge result. isStageOnly:', isStageOnly, 'newStatus:', newStatus, 'staged:', staged);
 
+              // Read suggested commit message if staging succeeded
+              let suggestedCommitMessage: string | undefined;
+              if (staged) {
+                const commitMsgPath = path.join(specDir, 'suggested_commit_message.txt');
+                try {
+                  if (existsSync(commitMsgPath)) {
+                    const { readFileSync } = require('fs');
+                    suggestedCommitMessage = readFileSync(commitMsgPath, 'utf-8').trim();
+                    debug('Read suggested commit message:', suggestedCommitMessage?.substring(0, 100));
+                  }
+                } catch (e) {
+                  debug('Failed to read suggested commit message:', e);
+                }
+              }
+
               // Persist the status change to implementation_plan.json
               const planPath = path.join(specDir, AUTO_BUILD_PATHS.IMPLEMENTATION_PLAN);
               try {
@@ -531,7 +546,8 @@ export function registerWorktreeHandlers(
                   success: true,
                   message,
                   staged,
-                  projectPath: staged ? project.path : undefined
+                  projectPath: staged ? project.path : undefined,
+                  suggestedCommitMessage
                 }
               });
             } else {
diff --git a/auto-claude-ui/src/main/ipc-handlers/terminal-handlers.ts b/auto-claude-ui/src/main/ipc-handlers/terminal-handlers.ts
index 6091635c..0dd83ba7 100644
--- a/auto-claude-ui/src/main/ipc-handlers/terminal-handlers.ts
+++ b/auto-claude-ui/src/main/ipc-handlers/terminal-handlers.ts
@@ -8,7 +8,7 @@ import { TerminalManager } from '../terminal-manager';
 import { projectStore } from '../project-store';
 import { terminalNameGenerator } from '../terminal-name-generator';
 import { debugLog, debugError } from '../../shared/utils/debug-logger';
-import { escapeShellArg } from '../../shared/utils/shell-escape';
+import { escapeShellArg, escapeShellArgWindows } from '../../shared/utils/shell-escape';
 
 
 /**
@@ -327,13 +327,20 @@ export function registerTerminalHandlers(
         await new Promise(resolve => setTimeout(resolve, 500));
 
         // Build the login command with the profile's config dir
-        // Use export to ensure the variable persists, then run setup-token
+        // Use platform-specific syntax and escaping for environment variables
         let loginCommand: string;
         if (!profile.isDefault && profile.configDir) {
-          // Use export and run in subshell to ensure CLAUDE_CONFIG_DIR is properly set
-          // SECURITY: Use escapeShellArg to prevent command injection via configDir
-          const escapedConfigDir = escapeShellArg(profile.configDir);
-          loginCommand = `export CLAUDE_CONFIG_DIR=${escapedConfigDir} && echo "Config dir: $CLAUDE_CONFIG_DIR" && claude setup-token`;
+          if (process.platform === 'win32') {
+            // SECURITY: Use Windows-specific escaping for cmd.exe
+            const escapedConfigDir = escapeShellArgWindows(profile.configDir);
+            // Windows cmd.exe syntax: set "VAR=value" with %VAR% for expansion
+            loginCommand = `set "CLAUDE_CONFIG_DIR=${escapedConfigDir}" && echo Config dir: %CLAUDE_CONFIG_DIR% && claude setup-token`;
+          } else {
+            // SECURITY: Use POSIX escaping for bash/zsh
+            const escapedConfigDir = escapeShellArg(profile.configDir);
+            // Unix/Mac bash/zsh syntax: export VAR=value with $VAR for expansion
+            loginCommand = `export CLAUDE_CONFIG_DIR=${escapedConfigDir} && echo "Config dir: $CLAUDE_CONFIG_DIR" && claude setup-token`;
+          }
         } else {
           loginCommand = 'claude setup-token';
         }
diff --git a/auto-claude-ui/src/renderer/App.tsx b/auto-claude-ui/src/renderer/App.tsx
index 591766b7..2961a920 100644
--- a/auto-claude-ui/src/renderer/App.tsx
+++ b/auto-claude-ui/src/renderer/App.tsx
@@ -29,7 +29,6 @@ import { Insights } from './components/Insights';
 import { GitHubIssues } from './components/GitHubIssues';
 import { Changelog } from './components/Changelog';
 import { Worktrees } from './components/Worktrees';
-import { AgentProfiles } from './components/AgentProfiles';
 import { WelcomeScreen } from './components/WelcomeScreen';
 import { RateLimitModal } from './components/RateLimitModal';
 import { SDKRateLimitModal } from './components/SDKRateLimitModal';
@@ -462,9 +461,6 @@ export function App() {
                 {activeView === 'worktrees' && selectedProjectId && (
                   <Worktrees projectId={selectedProjectId} />
                 )}
-                {activeView === 'agent-profiles' && (
-                  <AgentProfiles />
-                )}
                 {activeView === 'agent-tools' && (
                   <div className="flex h-full items-center justify-center">
                     <div className="text-center">
diff --git a/auto-claude-ui/src/renderer/components/AgentProfileSelector.tsx b/auto-claude-ui/src/renderer/components/AgentProfileSelector.tsx
index 85f0f4c8..88a16942 100644
--- a/auto-claude-ui/src/renderer/components/AgentProfileSelector.tsx
+++ b/auto-claude-ui/src/renderer/components/AgentProfileSelector.tsx
@@ -8,7 +8,7 @@
  * Used in TaskCreationWizard and TaskEditDialog.
  */
 import { useState } from 'react';
-import { Brain, Scale, Zap, Sliders, Sparkles, ChevronDown, ChevronUp } from 'lucide-react';
+import { Brain, Scale, Zap, Sliders, Sparkles, ChevronDown, ChevronUp, Pencil } from 'lucide-react';
 import { Label } from './ui/label';
 import {
   Select,
@@ -220,28 +220,37 @@ export function AgentProfileSelector({
 
       {/* Auto Profile - Phase Configuration */}
       {isAuto && (
-        <div className="space-y-3 rounded-lg border border-border bg-muted/30 p-4">
-          {/* Phase Summary */}
-          <div className="space-y-2">
-            <button
-              type="button"
-              onClick={() => setShowPhaseDetails(!showPhaseDetails)}
-              className={cn(
-                'flex w-full items-center justify-between text-sm',
-                'text-muted-foreground hover:text-foreground transition-colors'
+        <div className="rounded-lg border border-border bg-muted/30 overflow-hidden">
+          {/* Clickable Header */}
+          <button
+            type="button"
+            onClick={() => setShowPhaseDetails(!showPhaseDetails)}
+            className={cn(
+              'flex w-full items-center justify-between p-4 text-left',
+              'hover:bg-muted/50 transition-colors',
+              !disabled && 'cursor-pointer'
+            )}
+            disabled={disabled}
+          >
+            <div className="flex items-center gap-2">
+              <span className="font-medium text-sm text-foreground">Phase Configuration</span>
+              {!showPhaseDetails && (
+                <span className="flex items-center gap-1 text-xs text-muted-foreground">
+                  <Pencil className="h-3 w-3" />
+                  <span>Click to customize</span>
+                </span>
               )}
-              disabled={disabled}
-            >
-              <span className="font-medium text-foreground">Phase Configuration</span>
-              {showPhaseDetails ? (
-                <ChevronUp className="h-4 w-4" />
-              ) : (
-                <ChevronDown className="h-4 w-4" />
-              )}
-            </button>
+            </div>
+            {showPhaseDetails ? (
+              <ChevronUp className="h-4 w-4 text-muted-foreground" />
+            ) : (
+              <ChevronDown className="h-4 w-4 text-muted-foreground" />
+            )}
+          </button>
 
-            {/* Compact summary when collapsed */}
-            {!showPhaseDetails && (
+          {/* Compact summary when collapsed */}
+          {!showPhaseDetails && (
+            <div className="px-4 pb-4 -mt-1">
               <div className="grid grid-cols-2 gap-2 text-xs">
                 {(Object.keys(PHASE_LABELS) as Array<keyof PhaseModelConfig>).map((phase) => {
                   const modelLabel = AVAILABLE_MODELS.find(m => m.value === currentPhaseModels[phase])?.label?.replace('Claude ', '') || currentPhaseModels[phase];
@@ -253,55 +262,61 @@ export function AgentProfileSelector({
                   );
                 })}
               </div>
-            )}
-          </div>
+            </div>
+          )}
 
           {/* Detailed Phase Configuration */}
           {showPhaseDetails && (
-            <div className="space-y-4 pt-2">
+            <div className="px-4 pb-4 space-y-4 border-t border-border pt-4">
               {(Object.keys(PHASE_LABELS) as Array<keyof PhaseModelConfig>).map((phase) => (
                 <div key={phase} className="space-y-2">
                   <div className="flex items-center justify-between">
-                    <Label className="text-xs font-medium text-muted-foreground">
+                    <Label className="text-xs font-medium text-foreground">
                       {PHASE_LABELS[phase].label}
                     </Label>
-                    <span className="text-xs text-muted-foreground">
+                    <span className="text-[10px] text-muted-foreground">
                       {PHASE_LABELS[phase].description}
                     </span>
                   </div>
                   <div className="grid grid-cols-2 gap-2">
-                    <Select
-                      value={currentPhaseModels[phase]}
-                      onValueChange={(value) => handlePhaseModelChange(phase, value as ModelType)}
-                      disabled={disabled}
-                    >
-                      <SelectTrigger className="h-8 text-xs">
-                        <SelectValue />
-                      </SelectTrigger>
-                      <SelectContent>
-                        {AVAILABLE_MODELS.map((m) => (
-                          <SelectItem key={m.value} value={m.value}>
-                            {m.label}
-                          </SelectItem>
-                        ))}
-                      </SelectContent>
-                    </Select>
-                    <Select
-                      value={currentPhaseThinking[phase]}
-                      onValueChange={(value) => handlePhaseThinkingChange(phase, value as ThinkingLevel)}
-                      disabled={disabled}
-                    >
-                      <SelectTrigger className="h-8 text-xs">
-                        <SelectValue />
-                      </SelectTrigger>
-                      <SelectContent>
-                        {THINKING_LEVELS.map((level) => (
-                          <SelectItem key={level.value} value={level.value}>
-                            {level.label}
-                          </SelectItem>
-                        ))}
-                      </SelectContent>
-                    </Select>
+                    <div className="space-y-1">
+                      <Label className="text-[10px] text-muted-foreground">Model</Label>
+                      <Select
+                        value={currentPhaseModels[phase]}
+                        onValueChange={(value) => handlePhaseModelChange(phase, value as ModelType)}
+                        disabled={disabled}
+                      >
+                        <SelectTrigger className="h-8 text-xs">
+                          <SelectValue />
+                        </SelectTrigger>
+                        <SelectContent>
+                          {AVAILABLE_MODELS.map((m) => (
+                            <SelectItem key={m.value} value={m.value}>
+                              {m.label}
+                            </SelectItem>
+                          ))}
+                        </SelectContent>
+                      </Select>
+                    </div>
+                    <div className="space-y-1">
+                      <Label className="text-[10px] text-muted-foreground">Thinking</Label>
+                      <Select
+                        value={currentPhaseThinking[phase]}
+                        onValueChange={(value) => handlePhaseThinkingChange(phase, value as ThinkingLevel)}
+                        disabled={disabled}
+                      >
+                        <SelectTrigger className="h-8 text-xs">
+                          <SelectValue />
+                        </SelectTrigger>
+                        <SelectContent>
+                          {THINKING_LEVELS.map((level) => (
+                            <SelectItem key={level.value} value={level.value}>
+                              {level.label}
+                            </SelectItem>
+                          ))}
+                        </SelectContent>
+                      </Select>
+                    </div>
                   </div>
                 </div>
               ))}
diff --git a/auto-claude-ui/src/renderer/components/AgentProfiles.tsx b/auto-claude-ui/src/renderer/components/AgentProfiles.tsx
index e47a5dd0..83bd7a90 100644
--- a/auto-claude-ui/src/renderer/components/AgentProfiles.tsx
+++ b/auto-claude-ui/src/renderer/components/AgentProfiles.tsx
@@ -19,7 +19,7 @@ const iconMap: Record<string, React.ElementType> = {
  */
 export function AgentProfiles() {
   const settings = useSettingsStore((state) => state.settings);
-  const selectedProfileId = settings.selectedAgentProfile || 'balanced';
+  const selectedProfileId = settings.selectedAgentProfile || 'auto';
 
   const handleSelectProfile = async (profileId: string) => {
     await saveSettings({ selectedAgentProfile: profileId });
diff --git a/auto-claude-ui/src/renderer/components/Sidebar.tsx b/auto-claude-ui/src/renderer/components/Sidebar.tsx
index fcae0347..9f626407 100644
--- a/auto-claude-ui/src/renderer/components/Sidebar.tsx
+++ b/auto-claude-ui/src/renderer/components/Sidebar.tsx
@@ -16,8 +16,7 @@ import {
   FileText,
   Sparkles,
   GitBranch,
-  HelpCircle,
-  UserCog
+  HelpCircle
 } from 'lucide-react';
 import { Button } from './ui/button';
 import { ScrollArea } from './ui/scroll-area';
@@ -57,7 +56,7 @@ import { GitSetupModal } from './GitSetupModal';
 import { RateLimitIndicator } from './RateLimitIndicator';
 import type { Project, AutoBuildVersionInfo, GitStatus } from '../../shared/types';
 
-export type SidebarView = 'kanban' | 'terminals' | 'roadmap' | 'context' | 'ideation' | 'github-issues' | 'changelog' | 'insights' | 'worktrees' | 'agent-tools' | 'agent-profiles';
+export type SidebarView = 'kanban' | 'terminals' | 'roadmap' | 'context' | 'ideation' | 'github-issues' | 'changelog' | 'insights' | 'worktrees' | 'agent-tools';
 
 interface SidebarProps {
   onSettingsClick: () => void;
@@ -85,8 +84,7 @@ const projectNavItems: NavItem[] = [
 
 const toolsNavItems: NavItem[] = [
   { id: 'github-issues', label: 'GitHub Issues', icon: Github, shortcut: 'G' },
-  { id: 'worktrees', label: 'Worktrees', icon: GitBranch, shortcut: 'W' },
-  { id: 'agent-profiles', label: 'Agent Profiles', icon: UserCog, shortcut: 'P' }
+  { id: 'worktrees', label: 'Worktrees', icon: GitBranch, shortcut: 'W' }
 ];
 
 export function Sidebar({
diff --git a/auto-claude-ui/src/renderer/components/TaskCreationWizard.tsx b/auto-claude-ui/src/renderer/components/TaskCreationWizard.tsx
index 6aaa57d9..58b4c449 100644
--- a/auto-claude-ui/src/renderer/components/TaskCreationWizard.tsx
+++ b/auto-claude-ui/src/renderer/components/TaskCreationWizard.tsx
@@ -102,11 +102,12 @@ export function TaskCreationWizard({
   const [model, setModel] = useState<ModelType | ''>(selectedProfile.model);
   const [thinkingLevel, setThinkingLevel] = useState<ThinkingLevel | ''>(selectedProfile.thinkingLevel);
   // Auto profile - per-phase configuration
+  // Use custom settings from app settings if available, otherwise fall back to defaults
   const [phaseModels, setPhaseModels] = useState<PhaseModelConfig | undefined>(
-    selectedProfile.phaseModels || DEFAULT_PHASE_MODELS
+    settings.customPhaseModels || selectedProfile.phaseModels || DEFAULT_PHASE_MODELS
   );
   const [phaseThinking, setPhaseThinking] = useState<PhaseThinkingConfig | undefined>(
-    selectedProfile.phaseThinking || DEFAULT_PHASE_THINKING
+    settings.customPhaseThinking || selectedProfile.phaseThinking || DEFAULT_PHASE_THINKING
   );
 
   // Image attachments
@@ -143,8 +144,8 @@ export function TaskCreationWizard({
         setProfileId(draft.profileId || settings.selectedAgentProfile || 'auto');
         setModel(draft.model || selectedProfile.model);
         setThinkingLevel(draft.thinkingLevel || selectedProfile.thinkingLevel);
-        setPhaseModels(draft.phaseModels || selectedProfile.phaseModels || DEFAULT_PHASE_MODELS);
-        setPhaseThinking(draft.phaseThinking || selectedProfile.phaseThinking || DEFAULT_PHASE_THINKING);
+        setPhaseModels(draft.phaseModels || settings.customPhaseModels || selectedProfile.phaseModels || DEFAULT_PHASE_MODELS);
+        setPhaseThinking(draft.phaseThinking || settings.customPhaseThinking || selectedProfile.phaseThinking || DEFAULT_PHASE_THINKING);
         setImages(draft.images);
         setReferencedFiles(draft.referencedFiles ?? []);
         setRequireReviewBeforeCoding(draft.requireReviewBeforeCoding ?? false);
@@ -159,15 +160,15 @@ export function TaskCreationWizard({
         }
         // Note: Referenced Files section is always visible, no need to expand
       } else {
-        // No draft - initialize from selected profile
+        // No draft - initialize from selected profile and custom settings
         setProfileId(settings.selectedAgentProfile || 'auto');
         setModel(selectedProfile.model);
         setThinkingLevel(selectedProfile.thinkingLevel);
-        setPhaseModels(selectedProfile.phaseModels || DEFAULT_PHASE_MODELS);
-        setPhaseThinking(selectedProfile.phaseThinking || DEFAULT_PHASE_THINKING);
+        setPhaseModels(settings.customPhaseModels || selectedProfile.phaseModels || DEFAULT_PHASE_MODELS);
+        setPhaseThinking(settings.customPhaseThinking || selectedProfile.phaseThinking || DEFAULT_PHASE_THINKING);
       }
     }
-  }, [open, projectId, settings.selectedAgentProfile, selectedProfile.model, selectedProfile.thinkingLevel]);
+  }, [open, projectId, settings.selectedAgentProfile, settings.customPhaseModels, settings.customPhaseThinking, selectedProfile.model, selectedProfile.thinkingLevel]);
 
   // Fetch branches and project default branch when dialog opens
   useEffect(() => {
@@ -542,12 +543,12 @@ export function TaskCreationWizard({
     setPriority('');
     setComplexity('');
     setImpact('');
-    // Reset to selected profile defaults
+    // Reset to selected profile defaults and custom settings
     setProfileId(settings.selectedAgentProfile || 'auto');
     setModel(selectedProfile.model);
     setThinkingLevel(selectedProfile.thinkingLevel);
-    setPhaseModels(selectedProfile.phaseModels || DEFAULT_PHASE_MODELS);
-    setPhaseThinking(selectedProfile.phaseThinking || DEFAULT_PHASE_THINKING);
+    setPhaseModels(settings.customPhaseModels || selectedProfile.phaseModels || DEFAULT_PHASE_MODELS);
+    setPhaseThinking(settings.customPhaseThinking || selectedProfile.phaseThinking || DEFAULT_PHASE_THINKING);
     setImages([]);
     setReferencedFiles([]);
     setRequireReviewBeforeCoding(false);
diff --git a/auto-claude-ui/src/renderer/components/onboarding/GraphitiStep.tsx b/auto-claude-ui/src/renderer/components/onboarding/GraphitiStep.tsx
index f6783ba4..7f765ced 100644
--- a/auto-claude-ui/src/renderer/components/onboarding/GraphitiStep.tsx
+++ b/auto-claude-ui/src/renderer/components/onboarding/GraphitiStep.tsx
@@ -26,7 +26,7 @@ import {
   SelectValue
 } from '../ui/select';
 import { useSettingsStore } from '../../stores/settings-store';
-import type { GraphitiLLMProvider, GraphitiEmbeddingProvider } from '../../../shared/types';
+import type { GraphitiLLMProvider, GraphitiEmbeddingProvider, AppSettings } from '../../../shared/types';
 
 interface GraphitiStepProps {
   onNext: () => void;
@@ -314,8 +314,8 @@ export function GraphitiStep({ onNext, onBack, onSkip }: GraphitiStepProps) {
       const result = await window.electronAPI.saveSettings(settingsToSave);
 
       if (result?.success) {
-        // Update local settings store
-        const storeUpdate: Record<string, string> = {};
+        // Update local settings store with API key settings
+        const storeUpdate: Partial<Pick<AppSettings, 'globalOpenAIApiKey' | 'globalAnthropicApiKey' | 'globalGoogleApiKey' | 'globalGroqApiKey' | 'ollamaBaseUrl'>> = {};
         if (config.openaiApiKey.trim()) storeUpdate.globalOpenAIApiKey = config.openaiApiKey.trim();
         if (config.anthropicApiKey.trim()) storeUpdate.globalAnthropicApiKey = config.anthropicApiKey.trim();
         if (config.googleApiKey.trim()) storeUpdate.globalGoogleApiKey = config.googleApiKey.trim();
diff --git a/auto-claude-ui/src/renderer/components/project-settings/GitHubOAuthFlow.tsx b/auto-claude-ui/src/renderer/components/project-settings/GitHubOAuthFlow.tsx
index c743cd6c..16764b24 100644
--- a/auto-claude-ui/src/renderer/components/project-settings/GitHubOAuthFlow.tsx
+++ b/auto-claude-ui/src/renderer/components/project-settings/GitHubOAuthFlow.tsx
@@ -1,4 +1,4 @@
-import { useState, useEffect, useRef } from 'react';
+import { useState, useEffect, useRef, useCallback } from 'react';
 import {
   Github,
   Loader2,
@@ -6,7 +6,10 @@ import {
   AlertCircle,
   Info,
   ExternalLink,
-  Terminal
+  Terminal,
+  Copy,
+  Check,
+  Clock
 } from 'lucide-react';
 import { Button } from '../ui/button';
 import { Card, CardContent } from '../ui/card';
@@ -29,6 +32,10 @@ function debugLog(message: string, data?: unknown) {
   }
 }
 
+// Authentication timeout in milliseconds (5 minutes)
+// GitHub device codes typically expire after 15 minutes, but 5 minutes is a reasonable UX timeout
+const AUTH_TIMEOUT_MS = 5 * 60 * 1000;
+
 /**
  * GitHub OAuth flow component using gh CLI
  * Guides users through authenticating with GitHub using the gh CLI
@@ -40,10 +47,54 @@ export function GitHubOAuthFlow({ onSuccess, onCancel }: GitHubOAuthFlowProps) {
   const [cliVersion, setCliVersion] = useState<string | undefined>();
   const [username, setUsername] = useState<string | undefined>();
 
+  // Device flow state for displaying code and auth URL
+  const [deviceCode, setDeviceCode] = useState<string | null>(null);
+  const [authUrl, setAuthUrl] = useState<string | null>(null);
+  const [browserOpened, setBrowserOpened] = useState<boolean>(false);
+  const [codeCopied, setCodeCopied] = useState<boolean>(false);
+  const [urlCopied, setUrlCopied] = useState<boolean>(false);
+  const [isTimeout, setIsTimeout] = useState<boolean>(false);
+
+  // Ref to track authentication timeout
+  const authTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  // Refs to track copy feedback timeouts
+  const codeCopyTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const urlCopyTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+
   // Check gh CLI installation and authentication status on mount
   // Use a ref to prevent double-execution in React Strict Mode
   const hasCheckedRef = useRef(false);
 
+  // Clear the authentication timeout
+  const clearAuthTimeout = useCallback(() => {
+    if (authTimeoutRef.current) {
+      debugLog('Clearing auth timeout');
+      clearTimeout(authTimeoutRef.current);
+      authTimeoutRef.current = null;
+    }
+  }, []);
+
+  // Cleanup copy feedback timeouts on unmount
+  useEffect(() => {
+    return () => {
+      if (codeCopyTimeoutRef.current) {
+        clearTimeout(codeCopyTimeoutRef.current);
+      }
+      if (urlCopyTimeoutRef.current) {
+        clearTimeout(urlCopyTimeoutRef.current);
+      }
+    };
+  }, []);
+
+  // Handle authentication timeout
+  const handleAuthTimeout = useCallback(() => {
+    debugLog('Authentication timeout triggered after 5 minutes');
+    setIsTimeout(true);
+    setError('Authentication timed out. The authentication window was open for too long. Please try again.');
+    setStatus('error');
+    authTimeoutRef.current = null;
+  }, []);
+
   useEffect(() => {
     if (hasCheckedRef.current) {
       debugLog('Skipping duplicate check (Strict Mode)');
@@ -52,8 +103,13 @@ export function GitHubOAuthFlow({ onSuccess, onCancel }: GitHubOAuthFlowProps) {
     hasCheckedRef.current = true;
     debugLog('Component mounted, checking GitHub status...');
     checkGitHubStatus();
+
+    // Cleanup timeout on unmount
+    return () => {
+      clearAuthTimeout();
+    };
     // eslint-disable-next-line react-hooks/exhaustive-deps -- Only run once on mount, checkGitHubStatus is intentionally excluded
-  }, []);
+  }, [clearAuthTimeout]);
 
   const checkGitHubStatus = async () => {
     debugLog('checkGitHubStatus() called');
@@ -138,21 +194,59 @@ export function GitHubOAuthFlow({ onSuccess, onCancel }: GitHubOAuthFlowProps) {
     setStatus('authenticating');
     setError(null);
 
+    // Reset device flow state
+    setDeviceCode(null);
+    setAuthUrl(null);
+    setBrowserOpened(false);
+    setCodeCopied(false);
+    setUrlCopied(false);
+    setIsTimeout(false);
+
+    // Clear any existing timeout and start a new one
+    clearAuthTimeout();
+    debugLog(`Starting auth timeout (${AUTH_TIMEOUT_MS / 1000 / 60} minutes)`);
+    authTimeoutRef.current = setTimeout(handleAuthTimeout, AUTH_TIMEOUT_MS);
+
     try {
       debugLog('Calling startGitHubAuth...');
       const result = await window.electronAPI.startGitHubAuth();
       debugLog('startGitHubAuth result:', result);
 
+      // Clear timeout since we got a response
+      clearAuthTimeout();
+
+      // Capture device flow info if available
+      if (result.data?.deviceCode) {
+        debugLog('Device code received:', result.data.deviceCode);
+        setDeviceCode(result.data.deviceCode);
+      }
+      if (result.data?.authUrl) {
+        debugLog('Auth URL received:', result.data.authUrl);
+        setAuthUrl(result.data.authUrl);
+      }
+      if (result.data?.browserOpened !== undefined) {
+        debugLog('Browser opened status:', result.data.browserOpened);
+        setBrowserOpened(result.data.browserOpened);
+      }
+
       if (result.success && result.data?.success) {
         debugLog('Auth successful, fetching token...');
         // Fetch the token and notify parent
         await fetchAndNotifyToken();
       } else {
         debugLog('Auth failed:', result.error);
-        setError(result.error || 'Authentication failed');
+        // Include fallback URL info in error message if available
+        const errorMessage = result.error || 'Authentication failed';
+        setError(errorMessage);
+        // Keep authUrl from response for fallback display
+        if (result.data?.fallbackUrl) {
+          setAuthUrl(result.data.fallbackUrl);
+        }
         setStatus('error');
       }
     } catch (err) {
+      // Clear timeout on error
+      clearAuthTimeout();
       debugLog('Error in handleStartAuth:', err);
       setError(err instanceof Error ? err.message : 'Authentication failed');
       setStatus('error');
@@ -169,6 +263,30 @@ export function GitHubOAuthFlow({ onSuccess, onCancel }: GitHubOAuthFlowProps) {
     checkGitHubStatus();
   };
 
+  const handleCopyDeviceCode = async () => {
+    if (!deviceCode) return;
+    debugLog('Copying device code to clipboard');
+    try {
+      await navigator.clipboard.writeText(deviceCode);
+      setCodeCopied(true);
+      // Clear any existing timeout before setting a new one
+      if (codeCopyTimeoutRef.current) {
+        clearTimeout(codeCopyTimeoutRef.current);
+      }
+      // Reset the copied state after 2 seconds
+      codeCopyTimeoutRef.current = setTimeout(() => setCodeCopied(false), 2000);
+    } catch (err) {
+      debugLog('Failed to copy device code:', err);
+    }
+  };
+
+  const handleOpenAuthUrl = () => {
+    if (authUrl) {
+      debugLog('Opening auth URL manually:', authUrl);
+      window.open(authUrl, '_blank');
+    }
+  };
+
   debugLog('Rendering with status:', status);
 
   return (
@@ -263,21 +381,81 @@ export function GitHubOAuthFlow({ onSuccess, onCancel }: GitHubOAuthFlowProps) {
 
       {/* Authenticating */}
       {status === 'authenticating' && (
-        <Card className="border border-info/30 bg-info/10">
-          <CardContent className="p-6">
-            <div className="flex items-center gap-4">
-              <Loader2 className="h-6 w-6 animate-spin text-info shrink-0" />
-              <div className="flex-1">
-                <h3 className="text-lg font-medium text-foreground">
-                  Authenticating...
-                </h3>
-                <p className="text-sm text-muted-foreground mt-1">
-                  Please complete the authentication in your browser. This window will update automatically.
-                </p>
+        <div className="space-y-4">
+          <Card className="border border-info/30 bg-info/10">
+            <CardContent className="p-6">
+              <div className="flex items-center gap-4">
+                <Loader2 className="h-6 w-6 animate-spin text-info shrink-0" />
+                <div className="flex-1">
+                  <h3 className="text-lg font-medium text-foreground">
+                    Authenticating...
+                  </h3>
+                  <p className="text-sm text-muted-foreground mt-1">
+                    {browserOpened
+                      ? 'Please complete the authentication in your browser. This window will update automatically.'
+                      : 'Waiting for authentication flow to start...'}
+                  </p>
+                </div>
               </div>
-            </div>
-          </CardContent>
-        </Card>
+            </CardContent>
+          </Card>
+
+          {/* Device Code Display */}
+          {deviceCode && (
+            <Card className="border border-primary/30 bg-primary/5">
+              <CardContent className="p-6">
+                <div className="text-center space-y-4">
+                  <div className="space-y-2">
+                    <p className="text-sm font-medium text-foreground">
+                      Your one-time code
+                    </p>
+                    <div className="flex items-center justify-center gap-3">
+                      <code className="text-3xl font-mono font-bold tracking-widest text-primary px-4 py-2 bg-primary/10 rounded-lg">
+                        {deviceCode}
+                      </code>
+                      <Button
+                        variant="outline"
+                        size="sm"
+                        onClick={handleCopyDeviceCode}
+                        className="shrink-0"
+                      >
+                        {codeCopied ? (
+                          <>
+                            <Check className="h-4 w-4 mr-1 text-success" />
+                            Copied
+                          </>
+                        ) : (
+                          <>
+                            <Copy className="h-4 w-4 mr-1" />
+                            Copy
+                          </>
+                        )}
+                      </Button>
+                    </div>
+                  </div>
+
+                  <div className="text-sm text-muted-foreground space-y-2">
+                    <p>
+                      {browserOpened
+                        ? 'Enter this code in your browser to complete authentication.'
+                        : 'Copy this code, then open the link below to authenticate.'}
+                    </p>
+                    {!browserOpened && authUrl && (
+                      <Button
+                        variant="link"
+                        onClick={handleOpenAuthUrl}
+                        className="text-info hover:text-info/80 p-0 h-auto gap-1"
+                      >
+                        <ExternalLink className="h-4 w-4" />
+                        Open {authUrl}
+                      </Button>
+                    )}
+                  </div>
+                </div>
+              </CardContent>
+            </Card>
+          )}
+        </div>
       )}
 
       {/* Success */}
@@ -302,22 +480,106 @@ export function GitHubOAuthFlow({ onSuccess, onCancel }: GitHubOAuthFlowProps) {
       {/* Error */}
       {status === 'error' && error && (
         <div className="space-y-4">
-          <Card className="border border-destructive/30 bg-destructive/10">
+          <Card className={`border ${isTimeout ? 'border-warning/30 bg-warning/10' : 'border-destructive/30 bg-destructive/10'}`}>
             <CardContent className="p-5">
               <div className="flex items-start gap-3">
-                <AlertCircle className="h-5 w-5 text-destructive shrink-0 mt-0.5" />
+                {isTimeout ? (
+                  <Clock className="h-5 w-5 text-warning shrink-0 mt-0.5" />
+                ) : (
+                  <AlertCircle className="h-5 w-5 text-destructive shrink-0 mt-0.5" />
+                )}
                 <div className="flex-1">
-                  <h3 className="text-lg font-medium text-destructive">
-                    Authentication Failed
+                  <h3 className={`text-lg font-medium ${isTimeout ? 'text-warning' : 'text-destructive'}`}>
+                    {isTimeout ? 'Authentication Timed Out' : 'Authentication Failed'}
                   </h3>
-                  <p className="text-sm text-destructive/80 mt-1">{error}</p>
+                  <p className={`text-sm mt-1 ${isTimeout ? 'text-warning/80' : 'text-destructive/80'}`}>{error}</p>
                 </div>
               </div>
             </CardContent>
           </Card>
 
+          {/* Fallback URL display when browser failed to open */}
+          {authUrl && (
+            <Card className="border border-warning/30 bg-warning/10">
+              <CardContent className="p-5">
+                <div className="space-y-4">
+                  <div className="flex items-start gap-3">
+                    <Info className="h-5 w-5 text-warning shrink-0 mt-0.5" />
+                    <div className="flex-1">
+                      <h3 className="text-base font-medium text-foreground">
+                        Complete Authentication Manually
+                      </h3>
+                      <p className="text-sm text-muted-foreground mt-1">
+                        The browser couldn't be opened automatically. Please visit the URL below to complete authentication:
+                      </p>
+                    </div>
+                  </div>
+
+                  <div className="flex flex-col gap-3">
+                    <div className="flex items-center gap-2 p-3 bg-muted rounded-lg">
+                      <code className="text-sm font-mono text-foreground flex-1 break-all">
+                        {authUrl}
+                      </code>
+                      <Button
+                        variant="outline"
+                        size="sm"
+                        onClick={async () => {
+                          try {
+                            await navigator.clipboard.writeText(authUrl);
+                            setUrlCopied(true);
+                            // Clear any existing timeout before setting a new one
+                            if (urlCopyTimeoutRef.current) {
+                              clearTimeout(urlCopyTimeoutRef.current);
+                            }
+                            urlCopyTimeoutRef.current = setTimeout(() => setUrlCopied(false), 2000);
+                          } catch (err) {
+                            debugLog('Failed to copy URL:', err);
+                          }
+                        }}
+                        className="shrink-0"
+                      >
+                        {urlCopied ? (
+                          <>
+                            <Check className="h-4 w-4 mr-1 text-success" />
+                            Copied
+                          </>
+                        ) : (
+                          <>
+                            <Copy className="h-4 w-4 mr-1" />
+                            Copy
+                          </>
+                        )}
+                      </Button>
+                    </div>
+
+                    <Button
+                      variant="secondary"
+                      onClick={handleOpenAuthUrl}
+                      className="gap-2"
+                    >
+                      <ExternalLink className="h-4 w-4" />
+                      Open URL in Browser
+                    </Button>
+                  </div>
+
+                  {/* Device code reminder if available */}
+                  {deviceCode && (
+                    <div className="pt-2 border-t border-warning/20">
+                      <p className="text-sm text-muted-foreground">
+                        When prompted, enter this code:{' '}
+                        <code className="font-mono font-bold text-primary px-2 py-0.5 bg-primary/10 rounded">
+                          {deviceCode}
+                        </code>
+                      </p>
+                    </div>
+                  )}
+                </div>
+              </CardContent>
+            </Card>
+          )}
+
           <div className="flex justify-center gap-3">
-            <Button onClick={handleRetry} variant="outline">
+            <Button onClick={handleStartAuth} variant="outline">
               Retry
             </Button>
             {onCancel && (
diff --git a/auto-claude-ui/src/renderer/components/settings/AgentProfileSettings.tsx b/auto-claude-ui/src/renderer/components/settings/AgentProfileSettings.tsx
new file mode 100644
index 00000000..08a51f32
--- /dev/null
+++ b/auto-claude-ui/src/renderer/components/settings/AgentProfileSettings.tsx
@@ -0,0 +1,304 @@
+import { useState } from 'react';
+import { Brain, Scale, Zap, Check, Sparkles, ChevronDown, ChevronUp, RotateCcw } from 'lucide-react';
+import { cn } from '../../lib/utils';
+import {
+  DEFAULT_AGENT_PROFILES,
+  AVAILABLE_MODELS,
+  THINKING_LEVELS,
+  DEFAULT_PHASE_MODELS,
+  DEFAULT_PHASE_THINKING
+} from '../../../shared/constants';
+import { useSettingsStore, saveSettings } from '../../stores/settings-store';
+import { SettingsSection } from './SettingsSection';
+import { Label } from '../ui/label';
+import { Button } from '../ui/button';
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue
+} from '../ui/select';
+import type { AgentProfile, PhaseModelConfig, PhaseThinkingConfig, ModelTypeShort, ThinkingLevel } from '../../../shared/types/settings';
+
+/**
+ * Icon mapping for agent profile icons
+ */
+const iconMap: Record<string, React.ElementType> = {
+  Brain,
+  Scale,
+  Zap,
+  Sparkles
+};
+
+const PHASE_LABELS: Record<keyof PhaseModelConfig, { label: string; description: string }> = {
+  spec: { label: 'Spec Creation', description: 'Discovery, requirements, context gathering' },
+  planning: { label: 'Planning', description: 'Implementation planning and architecture' },
+  coding: { label: 'Coding', description: 'Actual code implementation' },
+  qa: { label: 'QA Review', description: 'Quality assurance and validation' }
+};
+
+/**
+ * Agent Profile Settings component
+ * Displays preset agent profiles for quick model/thinking level configuration
+ * Used in the Settings page under Agent Settings
+ */
+export function AgentProfileSettings() {
+  const settings = useSettingsStore((state) => state.settings);
+  const selectedProfileId = settings.selectedAgentProfile || 'auto';
+  const [showPhaseConfig, setShowPhaseConfig] = useState(selectedProfileId === 'auto');
+
+  // Get current phase config from settings or defaults
+  const currentPhaseModels: PhaseModelConfig = settings.customPhaseModels || DEFAULT_PHASE_MODELS;
+  const currentPhaseThinking: PhaseThinkingConfig = settings.customPhaseThinking || DEFAULT_PHASE_THINKING;
+
+  const handleSelectProfile = async (profileId: string) => {
+    const success = await saveSettings({ selectedAgentProfile: profileId });
+    if (!success) {
+      // Log error for debugging - in future could show user toast notification
+      console.error('Failed to save agent profile selection');
+      return;
+    }
+    // Auto-expand phase config when Auto profile is selected
+    if (profileId === 'auto') {
+      setShowPhaseConfig(true);
+    }
+  };
+
+  const handlePhaseModelChange = async (phase: keyof PhaseModelConfig, value: ModelTypeShort) => {
+    const newPhaseModels = { ...currentPhaseModels, [phase]: value };
+    await saveSettings({ customPhaseModels: newPhaseModels });
+  };
+
+  const handlePhaseThinkingChange = async (phase: keyof PhaseThinkingConfig, value: ThinkingLevel) => {
+    const newPhaseThinking = { ...currentPhaseThinking, [phase]: value };
+    await saveSettings({ customPhaseThinking: newPhaseThinking });
+  };
+
+  const handleResetToDefaults = async () => {
+    await saveSettings({
+      customPhaseModels: DEFAULT_PHASE_MODELS,
+      customPhaseThinking: DEFAULT_PHASE_THINKING
+    });
+  };
+
+  /**
+   * Get human-readable model label
+   */
+  const getModelLabel = (modelValue: string): string => {
+    const model = AVAILABLE_MODELS.find((m) => m.value === modelValue);
+    return model?.label || modelValue;
+  };
+
+  /**
+   * Get human-readable thinking level label
+   */
+  const getThinkingLabel = (thinkingValue: string): string => {
+    const level = THINKING_LEVELS.find((l) => l.value === thinkingValue);
+    return level?.label || thinkingValue;
+  };
+
+  /**
+   * Check if current config differs from defaults
+   */
+  const hasCustomConfig = (): boolean => {
+    const phases: Array<keyof PhaseModelConfig> = ['spec', 'planning', 'coding', 'qa'];
+    return phases.some(
+      phase =>
+        currentPhaseModels[phase] !== DEFAULT_PHASE_MODELS[phase] ||
+        currentPhaseThinking[phase] !== DEFAULT_PHASE_THINKING[phase]
+    );
+  };
+
+  /**
+   * Render a single profile card
+   */
+  const renderProfileCard = (profile: AgentProfile) => {
+    const isSelected = selectedProfileId === profile.id;
+    const Icon = iconMap[profile.icon || 'Brain'] || Brain;
+
+    return (
+      <button
+        key={profile.id}
+        onClick={() => handleSelectProfile(profile.id)}
+        className={cn(
+          'relative w-full rounded-lg border p-4 text-left transition-all duration-200',
+          'hover:border-primary/50 hover:shadow-sm',
+          isSelected
+            ? 'border-primary bg-primary/5'
+            : 'border-border bg-card'
+        )}
+      >
+        {/* Selected indicator */}
+        {isSelected && (
+          <div className="absolute right-3 top-3 flex h-5 w-5 items-center justify-center rounded-full bg-primary">
+            <Check className="h-3 w-3 text-primary-foreground" />
+          </div>
+        )}
+
+        {/* Profile content */}
+        <div className="flex items-start gap-3">
+          <div
+            className={cn(
+              'flex h-10 w-10 items-center justify-center rounded-lg shrink-0',
+              isSelected ? 'bg-primary/10' : 'bg-muted'
+            )}
+          >
+            <Icon
+              className={cn(
+                'h-5 w-5',
+                isSelected ? 'text-primary' : 'text-muted-foreground'
+              )}
+            />
+          </div>
+
+          <div className="flex-1 min-w-0 pr-6">
+            <h3 className="font-medium text-sm text-foreground">{profile.name}</h3>
+            <p className="mt-0.5 text-xs text-muted-foreground line-clamp-2">
+              {profile.description}
+            </p>
+
+            {/* Model and thinking level badges */}
+            <div className="mt-2 flex flex-wrap gap-1.5">
+              <span className="inline-flex items-center rounded bg-muted px-2 py-0.5 text-[10px] font-medium text-muted-foreground">
+                {getModelLabel(profile.model)}
+              </span>
+              <span className="inline-flex items-center rounded bg-muted px-2 py-0.5 text-[10px] font-medium text-muted-foreground">
+                {getThinkingLabel(profile.thinkingLevel)} Thinking
+              </span>
+            </div>
+          </div>
+        </div>
+      </button>
+    );
+  };
+
+  return (
+    <SettingsSection
+      title="Default Agent Profile"
+      description="Select a preset configuration for model and thinking level"
+    >
+      <div className="space-y-4">
+        {/* Description */}
+        <div className="rounded-lg bg-muted/50 p-3">
+          <p className="text-xs text-muted-foreground">
+            Agent profiles provide preset configurations for Claude model and thinking level.
+            When you create a new task, these settings will be used as defaults. You can always
+            override them in the task creation wizard.
+          </p>
+        </div>
+
+        {/* Profile cards - 2 column grid on larger screens */}
+        <div className="grid grid-cols-1 lg:grid-cols-2 gap-3">
+          {DEFAULT_AGENT_PROFILES.map(renderProfileCard)}
+        </div>
+
+        {/* Phase Configuration (only for Auto profile) */}
+        {selectedProfileId === 'auto' && (
+          <div className="mt-6 rounded-lg border border-border bg-card">
+            {/* Header - Collapsible */}
+            <button
+              type="button"
+              onClick={() => setShowPhaseConfig(!showPhaseConfig)}
+              className="flex w-full items-center justify-between p-4 text-left hover:bg-muted/50 transition-colors rounded-t-lg"
+            >
+              <div>
+                <h4 className="font-medium text-sm text-foreground">Phase Configuration</h4>
+                <p className="text-xs text-muted-foreground mt-0.5">
+                  Customize model and thinking level for each phase
+                </p>
+              </div>
+              {showPhaseConfig ? (
+                <ChevronUp className="h-4 w-4 text-muted-foreground" />
+              ) : (
+                <ChevronDown className="h-4 w-4 text-muted-foreground" />
+              )}
+            </button>
+
+            {/* Phase Configuration Content */}
+            {showPhaseConfig && (
+              <div className="border-t border-border p-4 space-y-4">
+                {/* Reset button */}
+                {hasCustomConfig() && (
+                  <div className="flex justify-end">
+                    <Button
+                      variant="ghost"
+                      size="sm"
+                      onClick={handleResetToDefaults}
+                      className="text-xs h-7"
+                    >
+                      <RotateCcw className="h-3 w-3 mr-1.5" />
+                      Reset to defaults
+                    </Button>
+                  </div>
+                )}
+
+                {/* Phase Configuration Grid */}
+                <div className="space-y-4">
+                  {(Object.keys(PHASE_LABELS) as Array<keyof PhaseModelConfig>).map((phase) => (
+                    <div key={phase} className="space-y-2">
+                      <div className="flex items-center justify-between">
+                        <Label className="text-sm font-medium text-foreground">
+                          {PHASE_LABELS[phase].label}
+                        </Label>
+                        <span className="text-xs text-muted-foreground">
+                          {PHASE_LABELS[phase].description}
+                        </span>
+                      </div>
+                      <div className="grid grid-cols-2 gap-3">
+                        {/* Model Select */}
+                        <div className="space-y-1">
+                          <Label className="text-xs text-muted-foreground">Model</Label>
+                          <Select
+                            value={currentPhaseModels[phase]}
+                            onValueChange={(value) => handlePhaseModelChange(phase, value as ModelTypeShort)}
+                          >
+                            <SelectTrigger className="h-9">
+                              <SelectValue />
+                            </SelectTrigger>
+                            <SelectContent>
+                              {AVAILABLE_MODELS.map((m) => (
+                                <SelectItem key={m.value} value={m.value}>
+                                  {m.label}
+                                </SelectItem>
+                              ))}
+                            </SelectContent>
+                          </Select>
+                        </div>
+                        {/* Thinking Level Select */}
+                        <div className="space-y-1">
+                          <Label className="text-xs text-muted-foreground">Thinking Level</Label>
+                          <Select
+                            value={currentPhaseThinking[phase]}
+                            onValueChange={(value) => handlePhaseThinkingChange(phase, value as ThinkingLevel)}
+                          >
+                            <SelectTrigger className="h-9">
+                              <SelectValue />
+                            </SelectTrigger>
+                            <SelectContent>
+                              {THINKING_LEVELS.map((level) => (
+                                <SelectItem key={level.value} value={level.value}>
+                                  {level.label}
+                                </SelectItem>
+                              ))}
+                            </SelectContent>
+                          </Select>
+                        </div>
+                      </div>
+                    </div>
+                  ))}
+                </div>
+
+                {/* Info note */}
+                <p className="text-[10px] text-muted-foreground mt-4 pt-3 border-t border-border">
+                  These settings will be used as defaults when creating new tasks with the Auto profile.
+                  You can override them per-task in the task creation wizard.
+                </p>
+              </div>
+            )}
+          </div>
+        )}
+      </div>
+    </SettingsSection>
+  );
+}
diff --git a/auto-claude-ui/src/renderer/components/settings/GeneralSettings.tsx b/auto-claude-ui/src/renderer/components/settings/GeneralSettings.tsx
index 1f49c2f3..be4b1a3f 100644
--- a/auto-claude-ui/src/renderer/components/settings/GeneralSettings.tsx
+++ b/auto-claude-ui/src/renderer/components/settings/GeneralSettings.tsx
@@ -3,6 +3,7 @@ import { Input } from '../ui/input';
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '../ui/select';
 import { Switch } from '../ui/switch';
 import { SettingsSection } from './SettingsSection';
+import { AgentProfileSettings } from './AgentProfileSettings';
 import { AVAILABLE_MODELS } from '../../../shared/constants';
 import type { AppSettings } from '../../../shared/types';
 
@@ -18,64 +19,51 @@ interface GeneralSettingsProps {
 export function GeneralSettings({ settings, onSettingsChange, section }: GeneralSettingsProps) {
   if (section === 'agent') {
     return (
-      <SettingsSection
-        title="Default Agent Settings"
-        description="Configure defaults for new projects"
-      >
-        <div className="space-y-6">
-          <div className="space-y-3">
-            <Label htmlFor="defaultModel" className="text-sm font-medium text-foreground">Default Model</Label>
-            <p className="text-sm text-muted-foreground">The AI model used for agent tasks</p>
-            <Select
-              value={settings.defaultModel}
-              onValueChange={(value) => onSettingsChange({ ...settings, defaultModel: value })}
-            >
-              <SelectTrigger id="defaultModel" className="w-full max-w-md">
-                <SelectValue />
-              </SelectTrigger>
-              <SelectContent>
-                {AVAILABLE_MODELS.map((model) => (
-                  <SelectItem key={model.value} value={model.value}>
-                    {model.label}
-                  </SelectItem>
-                ))}
-              </SelectContent>
-            </Select>
-          </div>
-          <div className="space-y-3">
-            <Label htmlFor="agentFramework" className="text-sm font-medium text-foreground">Agent Framework</Label>
-            <p className="text-sm text-muted-foreground">The coding framework used for autonomous tasks</p>
-            <Select
-              value={settings.agentFramework}
-              onValueChange={(value) => onSettingsChange({ ...settings, agentFramework: value })}
-            >
-              <SelectTrigger id="agentFramework" className="w-full max-w-md">
-                <SelectValue />
-              </SelectTrigger>
-              <SelectContent>
-                <SelectItem value="auto-claude">Auto Claude</SelectItem>
-              </SelectContent>
-            </Select>
-          </div>
-          <div className="space-y-3">
-            <div className="flex items-center justify-between max-w-md">
-              <div className="space-y-1">
-                <Label htmlFor="autoNameTerminals" className="text-sm font-medium text-foreground">
-                  AI Terminal Naming
-                </Label>
-                <p className="text-sm text-muted-foreground">
-                  Automatically name terminals based on commands (uses Haiku)
-                </p>
+      <div className="space-y-8">
+        {/* Agent Profile Selection */}
+        <AgentProfileSettings />
+
+        {/* Other Agent Settings */}
+        <SettingsSection
+          title="Other Agent Settings"
+          description="Additional agent configuration options"
+        >
+          <div className="space-y-6">
+            <div className="space-y-3">
+              <Label htmlFor="agentFramework" className="text-sm font-medium text-foreground">Agent Framework</Label>
+              <p className="text-sm text-muted-foreground">The coding framework used for autonomous tasks</p>
+              <Select
+                value={settings.agentFramework}
+                onValueChange={(value) => onSettingsChange({ ...settings, agentFramework: value })}
+              >
+                <SelectTrigger id="agentFramework" className="w-full max-w-md">
+                  <SelectValue />
+                </SelectTrigger>
+                <SelectContent>
+                  <SelectItem value="auto-claude">Auto Claude</SelectItem>
+                </SelectContent>
+              </Select>
+            </div>
+            <div className="space-y-3">
+              <div className="flex items-center justify-between max-w-md">
+                <div className="space-y-1">
+                  <Label htmlFor="autoNameTerminals" className="text-sm font-medium text-foreground">
+                    AI Terminal Naming
+                  </Label>
+                  <p className="text-sm text-muted-foreground">
+                    Automatically name terminals based on commands (uses Haiku)
+                  </p>
+                </div>
+                <Switch
+                  id="autoNameTerminals"
+                  checked={settings.autoNameTerminals}
+                  onCheckedChange={(checked) => onSettingsChange({ ...settings, autoNameTerminals: checked })}
+                />
               </div>
-              <Switch
-                id="autoNameTerminals"
-                checked={settings.autoNameTerminals}
-                onCheckedChange={(checked) => onSettingsChange({ ...settings, autoNameTerminals: checked })}
-              />
             </div>
           </div>
-        </div>
-      </SettingsSection>
+        </SettingsSection>
+      </div>
     );
   }
 
diff --git a/auto-claude-ui/src/renderer/components/task-detail/TaskDetailModal.tsx b/auto-claude-ui/src/renderer/components/task-detail/TaskDetailModal.tsx
index 6163e9f6..8e6510c5 100644
--- a/auto-claude-ui/src/renderer/components/task-detail/TaskDetailModal.tsx
+++ b/auto-claude-ui/src/renderer/components/task-detail/TaskDetailModal.tsx
@@ -120,6 +120,7 @@ function TaskDetailModalContent({ open, task, onOpenChange }: { open: boolean; t
           state.setWorkspaceError(null);
           state.setStagedSuccess(result.data.message || 'Changes staged in main project');
           state.setStagedProjectPath(result.data.projectPath);
+          state.setSuggestedCommitMessage(result.data.suggestedCommitMessage);
         } else {
           onOpenChange(false);
         }
@@ -393,6 +394,7 @@ function TaskDetailModalContent({ open, task, onOpenChange }: { open: boolean; t
                             stageOnly={state.stageOnly}
                             stagedSuccess={state.stagedSuccess}
                             stagedProjectPath={state.stagedProjectPath}
+                            suggestedCommitMessage={state.suggestedCommitMessage}
                             mergePreview={state.mergePreview}
                             isLoadingPreview={state.isLoadingPreview}
                             showConflictDialog={state.showConflictDialog}
@@ -405,6 +407,7 @@ function TaskDetailModalContent({ open, task, onOpenChange }: { open: boolean; t
                             onStageOnlyChange={state.setStageOnly}
                             onShowConflictDialog={state.setShowConflictDialog}
                             onLoadMergePreview={state.loadMergePreview}
+                            onClose={handleClose}
                           />
                         </>
                       )}
diff --git a/auto-claude-ui/src/renderer/components/task-detail/TaskDetailPanel.tsx b/auto-claude-ui/src/renderer/components/task-detail/TaskDetailPanel.tsx
index 7090f5d7..cb9e6237 100644
--- a/auto-claude-ui/src/renderer/components/task-detail/TaskDetailPanel.tsx
+++ b/auto-claude-ui/src/renderer/components/task-detail/TaskDetailPanel.tsx
@@ -84,6 +84,7 @@ export function TaskDetailPanel({ task, onClose }: TaskDetailPanelProps) {
           state.setWorkspaceError(null);
           state.setStagedSuccess(result.data.message || 'Changes staged in main project');
           state.setStagedProjectPath(result.data.projectPath);
+          state.setSuggestedCommitMessage(result.data.suggestedCommitMessage);
         } else {
           console.warn('[TaskDetailPanel] Full merge success, closing panel');
           onClose();
@@ -196,6 +197,7 @@ export function TaskDetailPanel({ task, onClose }: TaskDetailPanelProps) {
                     stageOnly={state.stageOnly}
                     stagedSuccess={state.stagedSuccess}
                     stagedProjectPath={state.stagedProjectPath}
+                    suggestedCommitMessage={state.suggestedCommitMessage}
                     mergePreview={state.mergePreview}
                     isLoadingPreview={state.isLoadingPreview}
                     showConflictDialog={state.showConflictDialog}
diff --git a/auto-claude-ui/src/renderer/components/task-detail/TaskReview.tsx b/auto-claude-ui/src/renderer/components/task-detail/TaskReview.tsx
index bf633524..ebfd96d5 100644
--- a/auto-claude-ui/src/renderer/components/task-detail/TaskReview.tsx
+++ b/auto-claude-ui/src/renderer/components/task-detail/TaskReview.tsx
@@ -26,6 +26,7 @@ interface TaskReviewProps {
   stageOnly: boolean;
   stagedSuccess: string | null;
   stagedProjectPath: string | undefined;
+  suggestedCommitMessage: string | undefined;
   mergePreview: { files: string[]; conflicts: MergeConflict[]; summary: MergeStats; gitConflicts?: GitConflictInfo; uncommittedChanges?: { hasChanges: boolean; files: string[]; count: number } | null } | null;
   isLoadingPreview: boolean;
   showConflictDialog: boolean;
@@ -38,6 +39,7 @@ interface TaskReviewProps {
   onStageOnlyChange: (value: boolean) => void;
   onShowConflictDialog: (show: boolean) => void;
   onLoadMergePreview: () => void;
+  onClose?: () => void;
 }
 
 /**
@@ -64,6 +66,7 @@ export function TaskReview({
   stageOnly,
   stagedSuccess,
   stagedProjectPath,
+  suggestedCommitMessage,
   mergePreview,
   isLoadingPreview,
   showConflictDialog,
@@ -75,7 +78,8 @@ export function TaskReview({
   onShowDiffDialog,
   onStageOnlyChange,
   onShowConflictDialog,
-  onLoadMergePreview
+  onLoadMergePreview,
+  onClose
 }: TaskReviewProps) {
   return (
     <div className="space-y-4">
@@ -88,6 +92,7 @@ export function TaskReview({
           stagedSuccess={stagedSuccess}
           stagedProjectPath={stagedProjectPath}
           task={task}
+          suggestedCommitMessage={suggestedCommitMessage}
         />
       )}
 
@@ -116,9 +121,10 @@ export function TaskReview({
           task={task}
           projectPath={stagedProjectPath}
           hasWorktree={worktreeStatus?.exists || false}
+          onClose={onClose}
         />
       ) : (
-        <NoWorkspaceMessage task={task} />
+        <NoWorkspaceMessage task={task} onClose={onClose} />
       )}
 
       {/* QA Feedback Section */}
diff --git a/auto-claude-ui/src/renderer/components/task-detail/hooks/useTaskDetail.ts b/auto-claude-ui/src/renderer/components/task-detail/hooks/useTaskDetail.ts
index 71ad2a2c..9d5aab0c 100644
--- a/auto-claude-ui/src/renderer/components/task-detail/hooks/useTaskDetail.ts
+++ b/auto-claude-ui/src/renderer/components/task-detail/hooks/useTaskDetail.ts
@@ -30,6 +30,7 @@ export function useTaskDetail({ task }: UseTaskDetailOptions) {
   const [stageOnly, setStageOnly] = useState(task.status === 'human_review');
   const [stagedSuccess, setStagedSuccess] = useState<string | null>(null);
   const [stagedProjectPath, setStagedProjectPath] = useState<string | undefined>(undefined);
+  const [suggestedCommitMessage, setSuggestedCommitMessage] = useState<string | undefined>(undefined);
   const [phaseLogs, setPhaseLogs] = useState<TaskLogs | null>(null);
   const [isLoadingLogs, setIsLoadingLogs] = useState(false);
   const [expandedPhases, setExpandedPhases] = useState<Set<TaskLogPhase>>(new Set());
@@ -279,6 +280,7 @@ export function useTaskDetail({ task }: UseTaskDetailOptions) {
     stageOnly,
     stagedSuccess,
     stagedProjectPath,
+    suggestedCommitMessage,
     phaseLogs,
     isLoadingLogs,
     expandedPhases,
@@ -318,6 +320,7 @@ export function useTaskDetail({ task }: UseTaskDetailOptions) {
     setStageOnly,
     setStagedSuccess,
     setStagedProjectPath,
+    setSuggestedCommitMessage,
     setPhaseLogs,
     setIsLoadingLogs,
     setExpandedPhases,
diff --git a/auto-claude-ui/src/renderer/components/task-detail/task-review/StagedSuccessMessage.tsx b/auto-claude-ui/src/renderer/components/task-detail/task-review/StagedSuccessMessage.tsx
index 802f4e78..95d3e5f3 100644
--- a/auto-claude-ui/src/renderer/components/task-detail/task-review/StagedSuccessMessage.tsx
+++ b/auto-claude-ui/src/renderer/components/task-detail/task-review/StagedSuccessMessage.tsx
@@ -1,11 +1,14 @@
-import { GitMerge, ExternalLink } from 'lucide-react';
+import { useState } from 'react';
+import { GitMerge, ExternalLink, Copy, Check, Sparkles } from 'lucide-react';
 import { Button } from '../../ui/button';
+import { Textarea } from '../../ui/textarea';
 import type { Task } from '../../../../shared/types';
 
 interface StagedSuccessMessageProps {
   stagedSuccess: string;
   stagedProjectPath: string | undefined;
   task: Task;
+  suggestedCommitMessage?: string;
 }
 
 /**
@@ -14,8 +17,23 @@ interface StagedSuccessMessageProps {
 export function StagedSuccessMessage({
   stagedSuccess,
   stagedProjectPath,
-  task
+  task,
+  suggestedCommitMessage
 }: StagedSuccessMessageProps) {
+  const [commitMessage, setCommitMessage] = useState(suggestedCommitMessage || '');
+  const [copied, setCopied] = useState(false);
+
+  const handleCopy = async () => {
+    if (!commitMessage) return;
+    try {
+      await navigator.clipboard.writeText(commitMessage);
+      setCopied(true);
+      setTimeout(() => setCopied(false), 2000);
+    } catch (err) {
+      console.error('Failed to copy:', err);
+    }
+  };
+
   return (
     <div className="rounded-xl border border-success/30 bg-success/10 p-4">
       <h3 className="font-medium text-sm text-foreground mb-2 flex items-center gap-2">
@@ -25,6 +43,47 @@ export function StagedSuccessMessage({
       <p className="text-sm text-muted-foreground mb-3">
         {stagedSuccess}
       </p>
+
+      {/* Commit Message Section */}
+      {suggestedCommitMessage && (
+        <div className="bg-background/50 rounded-lg p-3 mb-3">
+          <div className="flex items-center justify-between mb-2">
+            <p className="text-xs text-muted-foreground flex items-center gap-1.5">
+              <Sparkles className="h-3 w-3 text-purple-400" />
+              AI-generated commit message
+            </p>
+            <Button
+              variant="ghost"
+              size="sm"
+              onClick={handleCopy}
+              className="h-6 px-2 text-xs"
+              disabled={!commitMessage}
+            >
+              {copied ? (
+                <>
+                  <Check className="h-3 w-3 mr-1 text-success" />
+                  Copied!
+                </>
+              ) : (
+                <>
+                  <Copy className="h-3 w-3 mr-1" />
+                  Copy
+                </>
+              )}
+            </Button>
+          </div>
+          <Textarea
+            value={commitMessage}
+            onChange={(e) => setCommitMessage(e.target.value)}
+            className="font-mono text-xs min-h-[100px] bg-background/80 resize-y"
+            placeholder="Commit message..."
+          />
+          <p className="text-[10px] text-muted-foreground mt-1.5">
+            Edit as needed, then copy and use with <code className="bg-background px-1 rounded">git commit -m "..."</code>
+          </p>
+        </div>
+      )}
+
       <div className="bg-background/50 rounded-lg p-3 mb-3">
         <p className="text-xs text-muted-foreground mb-2">Next steps:</p>
         <ol className="text-xs text-muted-foreground space-y-1 list-decimal list-inside">
diff --git a/auto-claude-ui/src/renderer/components/task-detail/task-review/WorkspaceMessages.tsx b/auto-claude-ui/src/renderer/components/task-detail/task-review/WorkspaceMessages.tsx
index cc2ee3e6..81daa813 100644
--- a/auto-claude-ui/src/renderer/components/task-detail/task-review/WorkspaceMessages.tsx
+++ b/auto-claude-ui/src/renderer/components/task-detail/task-review/WorkspaceMessages.tsx
@@ -24,12 +24,13 @@ export function LoadingMessage({ message = 'Loading workspace info...' }: Loadin
 
 interface NoWorkspaceMessageProps {
   task?: Task;
+  onClose?: () => void;
 }
 
 /**
  * Displays message when no workspace is found for the task
  */
-export function NoWorkspaceMessage({ task }: NoWorkspaceMessageProps) {
+export function NoWorkspaceMessage({ task, onClose }: NoWorkspaceMessageProps) {
   const [isMarkingDone, setIsMarkingDone] = useState(false);
 
   const handleMarkDone = async () => {
@@ -38,6 +39,8 @@ export function NoWorkspaceMessage({ task }: NoWorkspaceMessageProps) {
     setIsMarkingDone(true);
     try {
       await persistTaskStatus(task.id, 'done');
+      // Auto-close modal after marking as done
+      onClose?.();
     } catch (err) {
       console.error('Error marking task as done:', err);
     } finally {
@@ -85,12 +88,13 @@ interface StagedInProjectMessageProps {
   task: Task;
   projectPath?: string;
   hasWorktree?: boolean;
+  onClose?: () => void;
 }
 
 /**
  * Displays message when changes have already been staged in the main project
  */
-export function StagedInProjectMessage({ task, projectPath, hasWorktree = false }: StagedInProjectMessageProps) {
+export function StagedInProjectMessage({ task, projectPath, hasWorktree = false, onClose }: StagedInProjectMessageProps) {
   const [isDeleting, setIsDeleting] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
@@ -110,7 +114,8 @@ export function StagedInProjectMessage({ task, projectPath, hasWorktree = false
       // Mark task as done
       await persistTaskStatus(task.id, 'done');
 
-      // Success - the UI will update automatically via the store
+      // Auto-close modal after marking as done
+      onClose?.();
     } catch (err) {
       console.error('Error deleting worktree:', err);
       setError(err instanceof Error ? err.message : 'Failed to delete worktree');
diff --git a/auto-claude-ui/src/shared/types/ipc.ts b/auto-claude-ui/src/shared/types/ipc.ts
index 050efe6c..26d0a88b 100644
--- a/auto-claude-ui/src/shared/types/ipc.ts
+++ b/auto-claude-ui/src/shared/types/ipc.ts
@@ -319,7 +319,14 @@ export interface ElectronAPI {
   // GitHub OAuth operations (gh CLI)
   checkGitHubCli: () => Promise<IPCResult<{ installed: boolean; version?: string }>>;
   checkGitHubAuth: () => Promise<IPCResult<{ authenticated: boolean; username?: string }>>;
-  startGitHubAuth: () => Promise<IPCResult<{ success: boolean; message?: string }>>;
+  startGitHubAuth: () => Promise<IPCResult<{
+    success: boolean;
+    message?: string;
+    deviceCode?: string;
+    authUrl?: string;
+    browserOpened?: boolean;
+    fallbackUrl?: string;
+  }>>;
   getGitHubToken: () => Promise<IPCResult<{ token: string }>>;
   getGitHubUser: () => Promise<IPCResult<{ username: string; name?: string }>>;
   listGitHubUserRepos: () => Promise<IPCResult<{ repos: Array<{ fullName: string; description: string | null; isPrivate: boolean }> }>>;
diff --git a/auto-claude-ui/src/shared/types/settings.ts b/auto-claude-ui/src/shared/types/settings.ts
index 0ff41b41..2f06f569 100644
--- a/auto-claude-ui/src/shared/types/settings.ts
+++ b/auto-claude-ui/src/shared/types/settings.ts
@@ -82,10 +82,15 @@ export interface AppSettings {
   onboardingCompleted?: boolean;
   // Selected agent profile for preset model/thinking configurations
   selectedAgentProfile?: string;
+  // Custom phase configuration for Auto profile (overrides defaults)
+  customPhaseModels?: PhaseModelConfig;
+  customPhaseThinking?: PhaseThinkingConfig;
   // Changelog preferences
   changelogFormat?: ChangelogFormat;
   changelogAudience?: ChangelogAudience;
   changelogEmojiLevel?: ChangelogEmojiLevel;
+  // Migration flags (internal use)
+  _migratedAgentProfileToAuto?: boolean;
 }
 
 // Auto-Claude Source Environment Configuration (for auto-claude repo .env)
diff --git a/auto-claude-ui/src/shared/types/task.ts b/auto-claude-ui/src/shared/types/task.ts
index 398578b5..276078ae 100644
--- a/auto-claude-ui/src/shared/types/task.ts
+++ b/auto-claude-ui/src/shared/types/task.ts
@@ -356,6 +356,8 @@ export interface WorktreeMergeResult {
   staged?: boolean;
   alreadyStaged?: boolean;
   projectPath?: string;
+  // AI-generated commit message suggestion (for stage-only mode)
+  suggestedCommitMessage?: string;
   // New conflict info from smart merge
   conflicts?: MergeConflict[];
   stats?: MergeStats;
diff --git a/auto-claude-ui/src/shared/utils/shell-escape.ts b/auto-claude-ui/src/shared/utils/shell-escape.ts
index 57e46275..80364362 100644
--- a/auto-claude-ui/src/shared/utils/shell-escape.ts
+++ b/auto-claude-ui/src/shared/utils/shell-escape.ts
@@ -51,6 +51,33 @@ export function buildCdCommand(path: string | undefined): string {
   return `cd ${escapeShellPath(path)} && `;
 }
 
+/**
+ * Escape a string for safe use as a Windows cmd.exe argument.
+ *
+ * Windows cmd.exe uses different escaping rules than POSIX shells.
+ * This function escapes special characters that could break out of strings
+ * or execute additional commands.
+ *
+ * @param arg - The argument to escape
+ * @returns The escaped argument safe for use in cmd.exe
+ */
+export function escapeShellArgWindows(arg: string): string {
+  // Escape characters that have special meaning in cmd.exe:
+  // ^ is the escape character in cmd.exe
+  // " & | < > ^ need to be escaped
+  // % is used for variable expansion
+  const escaped = arg
+    .replace(/\^/g, '^^')     // Escape carets first (escape char itself)
+    .replace(/"/g, '^"')      // Escape double quotes
+    .replace(/&/g, '^&')      // Escape ampersand (command separator)
+    .replace(/\|/g, '^|')     // Escape pipe
+    .replace(/</g, '^<')      // Escape less than
+    .replace(/>/g, '^>')      // Escape greater than
+    .replace(/%/g, '%%');     // Escape percent (variable expansion)
+
+  return escaped;
+}
+
 /**
  * Validate that a path doesn't contain obviously malicious patterns.
  * This is a defense-in-depth measure - escaping should handle all cases,
diff --git a/auto-claude-ui/vitest.config.ts b/auto-claude-ui/vitest.config.ts
index abc39cc8..6eb2f5ee 100644
--- a/auto-claude-ui/vitest.config.ts
+++ b/auto-claude-ui/vitest.config.ts
@@ -5,13 +5,13 @@ export default defineConfig({
   test: {
     globals: true,
     environment: 'node',
-    include: ['src/**/*.test.ts', 'src/**/*.test.tsx'],
+    include: ['src/**/*.test.ts', 'src/**/*.test.tsx', 'src/**/*.spec.ts', 'src/**/*.spec.tsx'],
     exclude: ['node_modules', 'dist', 'out'],
     coverage: {
       provider: 'v8',
       reporter: ['text', 'json', 'html'],
       include: ['src/**/*.ts', 'src/**/*.tsx'],
-      exclude: ['src/**/*.test.ts', 'src/**/*.test.tsx', 'src/**/*.d.ts']
+      exclude: ['src/**/*.test.ts', 'src/**/*.test.tsx', 'src/**/*.spec.ts', 'src/**/*.spec.tsx', 'src/**/*.d.ts']
     },
     // Mock Electron modules for unit tests
     alias: {
diff --git a/auto-claude/cli/workspace_commands.py b/auto-claude/cli/workspace_commands.py
index f204a480..4ebf5f82 100644
--- a/auto-claude/cli/workspace_commands.py
+++ b/auto-claude/cli/workspace_commands.py
@@ -189,7 +189,83 @@ def handle_merge_command(
     Returns:
         True if merge succeeded, False otherwise
     """
-    return merge_existing_build(project_dir, spec_name, no_commit=no_commit)
+    success = merge_existing_build(project_dir, spec_name, no_commit=no_commit)
+
+    # Generate commit message suggestion if staging succeeded (no_commit mode)
+    if success and no_commit:
+        _generate_and_save_commit_message(project_dir, spec_name)
+
+    return success
+
+
+def _generate_and_save_commit_message(project_dir: Path, spec_name: str) -> None:
+    """
+    Generate a commit message suggestion and save it for the UI.
+
+    Args:
+        project_dir: Project root directory
+        spec_name: Name of the spec
+    """
+    try:
+        from commit_message import generate_commit_message_sync
+
+        # Get diff summary for context
+        diff_summary = ""
+        files_changed = []
+        try:
+            result = subprocess.run(
+                ["git", "diff", "--staged", "--stat"],
+                cwd=project_dir,
+                capture_output=True,
+                text=True,
+            )
+            if result.returncode == 0:
+                diff_summary = result.stdout.strip()
+
+            # Get list of changed files
+            result = subprocess.run(
+                ["git", "diff", "--staged", "--name-only"],
+                cwd=project_dir,
+                capture_output=True,
+                text=True,
+            )
+            if result.returncode == 0:
+                files_changed = [
+                    f.strip() for f in result.stdout.strip().split("\n") if f.strip()
+                ]
+        except Exception as e:
+            debug_warning(MODULE, f"Could not get diff summary: {e}")
+
+        # Generate commit message
+        debug(MODULE, "Generating commit message suggestion...")
+        commit_message = generate_commit_message_sync(
+            project_dir=project_dir,
+            spec_name=spec_name,
+            diff_summary=diff_summary,
+            files_changed=files_changed,
+        )
+
+        if commit_message:
+            # Save to spec directory for UI to read
+            spec_dir = project_dir / ".auto-claude" / "specs" / spec_name
+            if not spec_dir.exists():
+                spec_dir = project_dir / "auto-claude" / "specs" / spec_name
+
+            if spec_dir.exists():
+                commit_msg_file = spec_dir / "suggested_commit_message.txt"
+                commit_msg_file.write_text(commit_message, encoding="utf-8")
+                debug_success(
+                    MODULE, f"Saved commit message suggestion to {commit_msg_file}"
+                )
+            else:
+                debug_warning(MODULE, f"Spec directory not found: {spec_dir}")
+        else:
+            debug_warning(MODULE, "No commit message generated")
+
+    except ImportError:
+        debug_warning(MODULE, "commit_message module not available")
+    except Exception as e:
+        debug_warning(MODULE, f"Failed to generate commit message: {e}")
 
 
 def handle_review_command(project_dir: Path, spec_name: str) -> None:
diff --git a/auto-claude/commit_message.py b/auto-claude/commit_message.py
new file mode 100644
index 00000000..fd3476e1
--- /dev/null
+++ b/auto-claude/commit_message.py
@@ -0,0 +1,373 @@
+"""
+Commit Message Generator
+========================
+
+Generates high-quality commit messages using Claude Haiku.
+
+Features:
+- Conventional commits format (feat/fix/refactor/etc)
+- GitHub issue references (Fixes #123)
+- Context-aware descriptions from spec metadata
+"""
+
+from __future__ import annotations
+
+import asyncio
+import json
+import logging
+import re
+import sys
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    pass
+
+logger = logging.getLogger(__name__)
+
+# Map task categories to conventional commit types
+CATEGORY_TO_COMMIT_TYPE = {
+    "feature": "feat",
+    "bug_fix": "fix",
+    "bug": "fix",
+    "refactoring": "refactor",
+    "refactor": "refactor",
+    "documentation": "docs",
+    "docs": "docs",
+    "testing": "test",
+    "test": "test",
+    "performance": "perf",
+    "perf": "perf",
+    "security": "security",
+    "chore": "chore",
+    "style": "style",
+    "ci": "ci",
+    "build": "build",
+}
+
+SYSTEM_PROMPT = """You are a Git expert who writes clear, concise commit messages following conventional commits format.
+
+Rules:
+1. First line: type(scope): description (max 72 chars total)
+2. Leave blank line after first line
+3. Body: 1-3 sentences explaining WHAT changed and WHY
+4. If GitHub issue number provided, end with "Fixes #N" on its own line
+5. Be specific about the changes, not generic
+6. Use imperative mood ("Add feature" not "Added feature")
+
+Types: feat, fix, refactor, docs, test, perf, chore, style, ci, build
+
+Example output:
+feat(auth): add OAuth2 login flow
+
+Implement OAuth2 authentication with Google and GitHub providers.
+Add token refresh logic and secure storage.
+
+Fixes #42"""
+
+
+def _get_spec_context(spec_dir: Path) -> dict:
+    """
+    Extract context from spec files for commit message generation.
+
+    Returns dict with:
+    - title: Feature/task title
+    - category: Task category (feature, bug_fix, etc)
+    - description: Brief description
+    - github_issue: GitHub issue number if linked
+    """
+    context = {
+        "title": "",
+        "category": "chore",
+        "description": "",
+        "github_issue": None,
+    }
+
+    # Try to read spec.md for title
+    spec_file = spec_dir / "spec.md"
+    if spec_file.exists():
+        try:
+            content = spec_file.read_text(encoding="utf-8")
+            # Extract title from first H1 or H2
+            title_match = re.search(r"^#+ (.+)$", content, re.MULTILINE)
+            if title_match:
+                context["title"] = title_match.group(1).strip()
+
+            # Look for overview/description section
+            overview_match = re.search(
+                r"## Overview\s*\n(.+?)(?=\n##|\Z)", content, re.DOTALL
+            )
+            if overview_match:
+                context["description"] = overview_match.group(1).strip()[:200]
+        except Exception as e:
+            logger.debug(f"Could not read spec.md: {e}")
+
+    # Try to read requirements.json for metadata
+    req_file = spec_dir / "requirements.json"
+    if req_file.exists():
+        try:
+            req_data = json.loads(req_file.read_text(encoding="utf-8"))
+            if not context["title"] and req_data.get("feature"):
+                context["title"] = req_data["feature"]
+            if req_data.get("workflow_type"):
+                context["category"] = req_data["workflow_type"]
+            if req_data.get("task_description") and not context["description"]:
+                context["description"] = req_data["task_description"][:200]
+        except Exception as e:
+            logger.debug(f"Could not read requirements.json: {e}")
+
+    # Try to read implementation_plan.json for GitHub issue
+    plan_file = spec_dir / "implementation_plan.json"
+    if plan_file.exists():
+        try:
+            plan_data = json.loads(plan_file.read_text(encoding="utf-8"))
+            # Check for GitHub metadata
+            metadata = plan_data.get("metadata", {})
+            if metadata.get("githubIssueNumber"):
+                context["github_issue"] = metadata["githubIssueNumber"]
+            # Fallback title
+            if not context["title"]:
+                context["title"] = plan_data.get("feature") or plan_data.get(
+                    "title", ""
+                )
+        except Exception as e:
+            logger.debug(f"Could not read implementation_plan.json: {e}")
+
+    return context
+
+
+def _build_prompt(
+    spec_context: dict,
+    diff_summary: str,
+    files_changed: list[str],
+) -> str:
+    """Build the prompt for Claude."""
+    commit_type = CATEGORY_TO_COMMIT_TYPE.get(
+        spec_context.get("category", "").lower(), "chore"
+    )
+
+    github_ref = ""
+    if spec_context.get("github_issue"):
+        github_ref = f"\nGitHub Issue: #{spec_context['github_issue']} (include 'Fixes #{spec_context['github_issue']}' at the end)"
+
+    # Truncate file list if too long
+    if len(files_changed) > 20:
+        files_display = (
+            "\n".join(files_changed[:20])
+            + f"\n... and {len(files_changed) - 20} more files"
+        )
+    else:
+        files_display = (
+            "\n".join(files_changed) if files_changed else "(no files listed)"
+        )
+
+    prompt = f"""Generate a commit message for this change.
+
+Task: {spec_context.get("title", "Unknown task")}
+Type: {commit_type}
+Files changed: {len(files_changed)}
+{github_ref}
+
+Description: {spec_context.get("description", "No description available")}
+
+Changed files:
+{files_display}
+
+Diff summary:
+{diff_summary[:2000] if diff_summary else "(no diff available)"}
+
+Generate ONLY the commit message, nothing else. Follow the format exactly:
+type(scope): short description
+
+Body explaining changes.
+
+Fixes #N (if applicable)"""
+
+    return prompt
+
+
+async def _call_claude_haiku(prompt: str) -> str:
+    """Call Claude Haiku with low thinking for fast commit message generation."""
+    from core.auth import ensure_claude_code_oauth_token, get_auth_token
+
+    if not get_auth_token():
+        logger.warning("No authentication token found")
+        return ""
+
+    ensure_claude_code_oauth_token()
+
+    try:
+        from claude_agent_sdk import ClaudeAgentOptions, ClaudeSDKClient
+    except ImportError:
+        logger.warning("claude_agent_sdk not installed")
+        return ""
+
+    client = ClaudeSDKClient(
+        options=ClaudeAgentOptions(
+            model="claude-haiku-4-5-20251001",
+            system_prompt=SYSTEM_PROMPT,
+            allowed_tools=[],
+            max_turns=1,
+            max_thinking_tokens=1024,  # Low thinking for speed
+        )
+    )
+
+    try:
+        async with client:
+            await client.query(prompt)
+
+            response_text = ""
+            async for msg in client.receive_response():
+                msg_type = type(msg).__name__
+                if msg_type == "AssistantMessage" and hasattr(msg, "content"):
+                    for block in msg.content:
+                        if hasattr(block, "text"):
+                            response_text += block.text
+
+            logger.info(f"Generated commit message: {len(response_text)} chars")
+            return response_text.strip()
+
+    except Exception as e:
+        logger.error(f"Claude SDK call failed: {e}")
+        print(f"    [WARN] Commit message generation failed: {e}", file=sys.stderr)
+        return ""
+
+
+def generate_commit_message_sync(
+    project_dir: Path,
+    spec_name: str,
+    diff_summary: str = "",
+    files_changed: list[str] | None = None,
+    github_issue: int | None = None,
+) -> str:
+    """
+    Generate a commit message synchronously.
+
+    Args:
+        project_dir: Project root directory
+        spec_name: Spec identifier (e.g., "001-add-feature")
+        diff_summary: Git diff stat or summary
+        files_changed: List of changed file paths
+        github_issue: GitHub issue number if linked (overrides spec metadata)
+
+    Returns:
+        Generated commit message or fallback message
+    """
+    # Find spec directory
+    spec_dir = project_dir / ".auto-claude" / "specs" / spec_name
+    if not spec_dir.exists():
+        # Try alternative location
+        spec_dir = project_dir / "auto-claude" / "specs" / spec_name
+
+    # Get context from spec files
+    spec_context = _get_spec_context(spec_dir) if spec_dir.exists() else {}
+
+    # Override with provided github_issue
+    if github_issue:
+        spec_context["github_issue"] = github_issue
+
+    # Build prompt
+    prompt = _build_prompt(
+        spec_context,
+        diff_summary,
+        files_changed or [],
+    )
+
+    # Call Claude
+    try:
+        # Check if we're already in an async context
+        try:
+            loop = asyncio.get_running_loop()
+        except RuntimeError:
+            loop = None
+
+        if loop and loop.is_running():
+            # Already in an async context - run in a new thread
+            # Use lambda to ensure coroutine is created inside the worker thread
+            import concurrent.futures
+
+            with concurrent.futures.ThreadPoolExecutor() as pool:
+                result = pool.submit(
+                    lambda: asyncio.run(_call_claude_haiku(prompt))
+                ).result()
+        else:
+            result = asyncio.run(_call_claude_haiku(prompt))
+
+        if result:
+            return result
+    except Exception as e:
+        logger.error(f"Failed to generate commit message: {e}")
+
+    # Fallback message
+    commit_type = CATEGORY_TO_COMMIT_TYPE.get(
+        spec_context.get("category", "").lower(), "chore"
+    )
+    title = spec_context.get("title", spec_name)
+    fallback = f"{commit_type}: {title}"
+
+    if github_issue or spec_context.get("github_issue"):
+        issue_num = github_issue or spec_context.get("github_issue")
+        fallback += f"\n\nFixes #{issue_num}"
+
+    return fallback
+
+
+async def generate_commit_message(
+    project_dir: Path,
+    spec_name: str,
+    diff_summary: str = "",
+    files_changed: list[str] | None = None,
+    github_issue: int | None = None,
+) -> str:
+    """
+    Generate a commit message asynchronously.
+
+    Args:
+        project_dir: Project root directory
+        spec_name: Spec identifier (e.g., "001-add-feature")
+        diff_summary: Git diff stat or summary
+        files_changed: List of changed file paths
+        github_issue: GitHub issue number if linked (overrides spec metadata)
+
+    Returns:
+        Generated commit message or fallback message
+    """
+    # Find spec directory
+    spec_dir = project_dir / ".auto-claude" / "specs" / spec_name
+    if not spec_dir.exists():
+        spec_dir = project_dir / "auto-claude" / "specs" / spec_name
+
+    # Get context from spec files
+    spec_context = _get_spec_context(spec_dir) if spec_dir.exists() else {}
+
+    # Override with provided github_issue
+    if github_issue:
+        spec_context["github_issue"] = github_issue
+
+    # Build prompt
+    prompt = _build_prompt(
+        spec_context,
+        diff_summary,
+        files_changed or [],
+    )
+
+    # Call Claude
+    try:
+        result = await _call_claude_haiku(prompt)
+        if result:
+            return result
+    except Exception as e:
+        logger.error(f"Failed to generate commit message: {e}")
+
+    # Fallback message
+    commit_type = CATEGORY_TO_COMMIT_TYPE.get(
+        spec_context.get("category", "").lower(), "chore"
+    )
+    title = spec_context.get("title", spec_name)
+    fallback = f"{commit_type}: {title}"
+
+    if github_issue or spec_context.get("github_issue"):
+        issue_num = github_issue or spec_context.get("github_issue")
+        fallback += f"\n\nFixes #{issue_num}"
+
+    return fallback
diff --git a/auto-claude/core/auth.py b/auto-claude/core/auth.py
index 7ba8c0f4..76e54eb5 100644
--- a/auto-claude/core/auth.py
+++ b/auto-claude/core/auth.py
@@ -47,7 +47,13 @@ def get_token_from_keychain() -> str | None:
     try:
         # Query macOS Keychain for Claude Code credentials
         result = subprocess.run(
-            ["/usr/bin/security", "find-generic-password", "-s", "Claude Code-credentials", "-w"],
+            [
+                "/usr/bin/security",
+                "find-generic-password",
+                "-s",
+                "Claude Code-credentials",
+                "-w",
+            ],
             capture_output=True,
             text=True,
             timeout=5,
diff --git a/auto-claude/core/workspace.py b/auto-claude/core/workspace.py
index 0349a821..4d55db84 100644
--- a/auto-claude/core/workspace.py
+++ b/auto-claude/core/workspace.py
@@ -80,6 +80,7 @@ from core.workspace.display import (
     show_build_summary,
 )
 from core.workspace.git_utils import (
+    MAX_PARALLEL_AI_MERGES,
     _is_auto_claude_file,
     get_existing_build_worktree,
 )
@@ -97,6 +98,7 @@ from core.workspace.git_utils import (
 from core.workspace.models import (
     MergeLock,
     MergeLockError,
+    ParallelMergeResult,
     ParallelMergeTask,
 )
 from merge import (
@@ -858,13 +860,13 @@ def _resolve_git_conflicts_with_ai(
         start_time = time.time()
 
         # Run parallel merges
-        # TODO: _run_parallel_merges not yet implemented - see line 140
-        # parallel_results = asyncio.run(_run_parallel_merges(
-        #     tasks=files_needing_ai_merge,
-        #     project_dir=project_dir,
-        #     max_concurrent=MAX_PARALLEL_AI_MERGES,
-        # ))
-        parallel_results = []  # Placeholder until function is implemented
+        parallel_results = asyncio.run(
+            _run_parallel_merges(
+                tasks=files_needing_ai_merge,
+                project_dir=project_dir,
+                max_concurrent=MAX_PARALLEL_AI_MERGES,
+            )
+        )
 
         elapsed = time.time() - start_time
 
@@ -996,3 +998,332 @@ def _resolve_git_conflicts_with_ai(
 # - Git utilities from workspace/git_utils.py
 # - Display functions from workspace/display.py
 # - Finalization functions from workspace/finalization.py
+
+
+# =============================================================================
+# Parallel AI Merge Implementation
+# =============================================================================
+
+import asyncio
+import logging
+import os
+
+_merge_logger = logging.getLogger(__name__)
+
+# System prompt for AI file merging
+AI_MERGE_SYSTEM_PROMPT = """You are an expert code merge assistant. Your task is to perform a 3-way merge of code files.
+
+RULES:
+1. Preserve all functional changes from both versions (ours and theirs)
+2. Maintain code style consistency
+3. Resolve conflicts by understanding the semantic purpose of each change
+4. When changes are independent (different functions/sections), include both
+5. When changes overlap, combine them logically or prefer the more complete version
+6. Preserve all imports from both versions
+7. Output ONLY the merged code - no explanations, no markdown, no code fences
+
+IMPORTANT: Output the raw merged file content only. Do not wrap in code blocks."""
+
+
+def _infer_language_from_path(file_path: str) -> str:
+    """Infer programming language from file extension."""
+    ext_map = {
+        ".py": "python",
+        ".js": "javascript",
+        ".jsx": "javascript",
+        ".ts": "typescript",
+        ".tsx": "typescript",
+        ".rs": "rust",
+        ".go": "go",
+        ".java": "java",
+        ".cpp": "cpp",
+        ".c": "c",
+        ".h": "c",
+        ".hpp": "cpp",
+        ".rb": "ruby",
+        ".php": "php",
+        ".swift": "swift",
+        ".kt": "kotlin",
+        ".scala": "scala",
+        ".json": "json",
+        ".yaml": "yaml",
+        ".yml": "yaml",
+        ".toml": "toml",
+        ".md": "markdown",
+        ".html": "html",
+        ".css": "css",
+        ".scss": "scss",
+        ".sql": "sql",
+    }
+    ext = os.path.splitext(file_path)[1].lower()
+    return ext_map.get(ext, "text")
+
+
+def _try_simple_3way_merge(
+    base: str | None,
+    ours: str,
+    theirs: str,
+) -> tuple[bool, str | None]:
+    """
+    Attempt a simple 3-way merge without AI.
+
+    Returns:
+        (success, merged_content) - if success is True, merged_content is the result
+    """
+    # If base is None, we can't do a proper 3-way merge
+    if base is None:
+        # If both are identical, no conflict
+        if ours == theirs:
+            return True, ours
+        # Otherwise, we need AI to decide
+        return False, None
+
+    # If ours equals base, theirs is the only change - take theirs
+    if ours == base:
+        return True, theirs
+
+    # If theirs equals base, ours is the only change - take ours
+    if theirs == base:
+        return True, ours
+
+    # If ours equals theirs, both made same change - take either
+    if ours == theirs:
+        return True, ours
+
+    # Both changed differently from base - need AI merge
+    # We could try a line-by-line merge here, but for safety let's use AI
+    return False, None
+
+
+def _build_merge_prompt(
+    file_path: str,
+    base_content: str | None,
+    main_content: str,
+    worktree_content: str,
+    spec_name: str,
+) -> str:
+    """Build the prompt for AI file merge."""
+    language = _infer_language_from_path(file_path)
+
+    base_section = ""
+    if base_content:
+        # Truncate very large files
+        if len(base_content) > 10000:
+            base_content = base_content[:10000] + "\n... (truncated)"
+        base_section = f"""
+BASE (common ancestor):
+```{language}
+{base_content}
+```
+"""
+
+    # Truncate large content
+    if len(main_content) > 15000:
+        main_content = main_content[:15000] + "\n... (truncated)"
+    if len(worktree_content) > 15000:
+        worktree_content = worktree_content[:15000] + "\n... (truncated)"
+
+    prompt = f"""Perform a 3-way merge for file: {file_path}
+Task being merged: {spec_name}
+{base_section}
+OURS (current main branch):
+```{language}
+{main_content}
+```
+
+THEIRS (changes from task worktree):
+```{language}
+{worktree_content}
+```
+
+Merge these versions, preserving all meaningful changes from both. Output only the merged file content, no explanations."""
+
+    return prompt
+
+
+def _strip_code_fences(content: str) -> str:
+    """Remove markdown code fences if present."""
+    # Check if content starts with code fence
+    lines = content.strip().split("\n")
+    if lines and lines[0].startswith("```"):
+        # Remove first and last line if they're code fences
+        if lines[-1].strip() == "```":
+            return "\n".join(lines[1:-1])
+        else:
+            return "\n".join(lines[1:])
+    return content
+
+
+async def _merge_file_with_ai_async(
+    task: ParallelMergeTask,
+    semaphore: asyncio.Semaphore,
+) -> ParallelMergeResult:
+    """
+    Merge a single file using AI.
+
+    Args:
+        task: The merge task with file contents
+        semaphore: Semaphore for concurrency control
+
+    Returns:
+        ParallelMergeResult with merged content or error
+    """
+    async with semaphore:
+        try:
+            # First try simple 3-way merge
+            success, merged = _try_simple_3way_merge(
+                task.base_content,
+                task.main_content,
+                task.worktree_content,
+            )
+
+            if success and merged is not None:
+                debug(MODULE, f"Auto-merged {task.file_path} without AI")
+                return ParallelMergeResult(
+                    file_path=task.file_path,
+                    merged_content=merged,
+                    success=True,
+                    was_auto_merged=True,
+                )
+
+            # Need AI merge
+            debug(MODULE, f"Using AI to merge {task.file_path}")
+
+            # Import auth utilities
+            from core.auth import ensure_claude_code_oauth_token, get_auth_token
+
+            if not get_auth_token():
+                return ParallelMergeResult(
+                    file_path=task.file_path,
+                    merged_content=None,
+                    success=False,
+                    error="No authentication token available",
+                )
+
+            ensure_claude_code_oauth_token()
+
+            # Build prompt
+            prompt = _build_merge_prompt(
+                task.file_path,
+                task.base_content,
+                task.main_content,
+                task.worktree_content,
+                task.spec_name,
+            )
+
+            # Call Claude Haiku for fast merge
+            try:
+                from claude_agent_sdk import ClaudeAgentOptions, ClaudeSDKClient
+            except ImportError:
+                return ParallelMergeResult(
+                    file_path=task.file_path,
+                    merged_content=None,
+                    success=False,
+                    error="claude_agent_sdk not installed",
+                )
+
+            client = ClaudeSDKClient(
+                options=ClaudeAgentOptions(
+                    model="claude-haiku-4-5-20251001",
+                    system_prompt=AI_MERGE_SYSTEM_PROMPT,
+                    allowed_tools=[],
+                    max_turns=1,
+                    max_thinking_tokens=1024,  # Low thinking for speed
+                )
+            )
+
+            response_text = ""
+            async with client:
+                await client.query(prompt)
+
+                async for msg in client.receive_response():
+                    msg_type = type(msg).__name__
+                    if msg_type == "AssistantMessage" and hasattr(msg, "content"):
+                        for block in msg.content:
+                            if hasattr(block, "text"):
+                                response_text += block.text
+
+            if response_text:
+                # Strip any code fences the model might have added
+                merged_content = _strip_code_fences(response_text.strip())
+
+                debug(MODULE, f"AI merged {task.file_path} successfully")
+                return ParallelMergeResult(
+                    file_path=task.file_path,
+                    merged_content=merged_content,
+                    success=True,
+                    was_auto_merged=False,
+                )
+            else:
+                return ParallelMergeResult(
+                    file_path=task.file_path,
+                    merged_content=None,
+                    success=False,
+                    error="AI returned empty response",
+                )
+
+        except Exception as e:
+            _merge_logger.error(f"Failed to merge {task.file_path}: {e}")
+            return ParallelMergeResult(
+                file_path=task.file_path,
+                merged_content=None,
+                success=False,
+                error=str(e),
+            )
+
+
+async def _run_parallel_merges(
+    tasks: list[ParallelMergeTask],
+    project_dir: Path,
+    max_concurrent: int = MAX_PARALLEL_AI_MERGES,
+) -> list[ParallelMergeResult]:
+    """
+    Run file merges in parallel with concurrency control.
+
+    Args:
+        tasks: List of merge tasks to process
+        project_dir: Project directory (for context, not currently used)
+        max_concurrent: Maximum number of concurrent merge operations
+
+    Returns:
+        List of ParallelMergeResult for each task
+    """
+    if not tasks:
+        return []
+
+    debug(
+        MODULE,
+        f"Starting parallel merge of {len(tasks)} files (max concurrent: {max_concurrent})",
+    )
+
+    # Create semaphore for concurrency control
+    semaphore = asyncio.Semaphore(max_concurrent)
+
+    # Create tasks
+    merge_coroutines = [_merge_file_with_ai_async(task, semaphore) for task in tasks]
+
+    # Run all merges concurrently
+    results = await asyncio.gather(*merge_coroutines, return_exceptions=True)
+
+    # Process results, converting exceptions to error results
+    final_results: list[ParallelMergeResult] = []
+    for i, result in enumerate(results):
+        if isinstance(result, Exception):
+            final_results.append(
+                ParallelMergeResult(
+                    file_path=tasks[i].file_path,
+                    merged_content=None,
+                    success=False,
+                    error=str(result),
+                )
+            )
+        else:
+            final_results.append(result)
+
+    debug(
+        MODULE,
+        f"Parallel merge complete: {sum(1 for r in final_results if r.success)} succeeded, "
+        f"{sum(1 for r in final_results if not r.success)} failed",
+    )
+
+    return final_results
diff --git a/auto-claude/core/workspace/__init__.py b/auto-claude/core/workspace/__init__.py
index 43a9e23e..e5b5ac71 100644
--- a/auto-claude/core/workspace/__init__.py
+++ b/auto-claude/core/workspace/__init__.py
@@ -27,8 +27,7 @@ _spec = importlib.util.spec_from_file_location("workspace_module", _workspace_fi
 _workspace_module = importlib.util.module_from_spec(_spec)
 _spec.loader.exec_module(_workspace_module)
 merge_existing_build = _workspace_module.merge_existing_build
-# TODO: _run_parallel_merges not yet implemented in workspace.py
-# _run_parallel_merges = _workspace_module._run_parallel_merges
+_run_parallel_merges = _workspace_module._run_parallel_merges
 
 # Models and Enums
 # Display Functions
@@ -105,7 +104,7 @@ from .setup import (
 __all__ = [
     # Merge Operations (from workspace.py)
     "merge_existing_build",
-    # '_run_parallel_merges',  # TODO: not yet implemented - Private but used by tests
+    "_run_parallel_merges",  # Private but used internally
     # Models
     "WorkspaceMode",
     "WorkspaceChoice",
diff --git a/auto-claude/merge/file_evolution/modification_tracker.py b/auto-claude/merge/file_evolution/modification_tracker.py
index 5a4416de..c30d8848 100644
--- a/auto-claude/merge/file_evolution/modification_tracker.py
+++ b/auto-claude/merge/file_evolution/modification_tracker.py
@@ -196,7 +196,9 @@ class ModificationTracker:
                     try:
                         new_content = current_file.read_text(encoding="utf-8")
                     except UnicodeDecodeError:
-                        new_content = current_file.read_text(encoding="utf-8", errors="replace")
+                        new_content = current_file.read_text(
+                            encoding="utf-8", errors="replace"
+                        )
                 else:
                     # File was deleted
                     new_content = ""
diff --git a/auto-claude/merge/timeline_tracker.py b/auto-claude/merge/timeline_tracker.py
index 92ca006b..d557747d 100644
--- a/auto-claude/merge/timeline_tracker.py
+++ b/auto-claude/merge/timeline_tracker.py
@@ -509,7 +509,9 @@ class FileTimelineTracker:
                     try:
                         content = full_path.read_text(encoding="utf-8")
                     except UnicodeDecodeError:
-                        content = full_path.read_text(encoding="utf-8", errors="replace")
+                        content = full_path.read_text(
+                            encoding="utf-8", errors="replace"
+                        )
                     self.on_task_worktree_change(task_id, file_path, content)
 
             debug_success(MODULE, f"Captured {len(changed_files)} files from worktree")
diff --git a/auto-claude/prompts/planner.md b/auto-claude/prompts/planner.md
index 9a27c670..661676c9 100644
--- a/auto-claude/prompts/planner.md
+++ b/auto-claude/prompts/planner.md
@@ -90,9 +90,9 @@ Find these critical sections:
 cat project_index.json
 ```
 
-**IF THIS FILE DOES NOT EXIST, YOU MUST CREATE IT.**
+**IF THIS FILE DOES NOT EXIST, YOU MUST CREATE IT USING THE WRITE TOOL.**
 
-Based on your Phase 0 investigation, create `project_index.json`:
+Based on your Phase 0 investigation, use the Write tool to create `project_index.json`:
 
 ```json
 {
@@ -130,9 +130,9 @@ This contains:
 cat context.json
 ```
 
-**IF THIS FILE DOES NOT EXIST, YOU MUST CREATE IT.**
+**IF THIS FILE DOES NOT EXIST, YOU MUST CREATE IT USING THE WRITE TOOL.**
 
-Based on your Phase 0 investigation and the spec.md, create `context.json`:
+Based on your Phase 0 investigation and the spec.md, use the Write tool to create `context.json`:
 
 ```json
 {
@@ -203,6 +203,15 @@ Minimal overhead - just subtasks, no phases.
 
 ## PHASE 3: CREATE implementation_plan.json
 
+**🚨 CRITICAL: YOU MUST USE THE WRITE TOOL TO CREATE THIS FILE 🚨**
+
+You MUST use the Write tool to save the implementation plan to `implementation_plan.json`.
+Do NOT just describe what the file should contain - you must actually call the Write tool with the complete JSON content.
+
+**Required action:** Call the Write tool with:
+- file_path: `implementation_plan.json` (in the spec directory)
+- content: The complete JSON plan structure shown below
+
 Based on the workflow type and services involved, create the implementation plan.
 
 ### Plan Structure
@@ -631,8 +640,26 @@ Include parallelism analysis, verification strategy, and QA configuration in the
 
 ---
 
+**🚨 END OF PHASE 4 CHECKPOINT 🚨**
+
+Before proceeding to PHASE 5, verify you have:
+1. ✅ Created the complete implementation_plan.json structure
+2. ✅ Used the Write tool to save it (not just described it)
+3. ✅ Added the summary section with parallelism analysis
+4. ✅ Added the verification_strategy section
+5. ✅ Added the qa_acceptance section
+
+If you have NOT used the Write tool yet, STOP and do it now!
+
+---
+
 ## PHASE 5: CREATE init.sh
 
+**🚨 CRITICAL: YOU MUST USE THE WRITE TOOL TO CREATE THIS FILE 🚨**
+
+You MUST use the Write tool to save the init.sh script.
+Do NOT just describe what the file should contain - you must actually call the Write tool.
+
 Create a setup script based on `project_index.json`:
 
 ```bash
@@ -735,6 +762,11 @@ Note: If the commit fails (e.g., nothing to commit, or in a special workspace),
 
 ## PHASE 7: CREATE build-progress.txt
 
+**🚨 CRITICAL: YOU MUST USE THE WRITE TOOL TO CREATE THIS FILE 🚨**
+
+You MUST use the Write tool to save build-progress.txt.
+Do NOT just describe what the file should contain - you must actually call the Write tool with the complete content shown below.
+
 ```
 === AUTO-BUILD PROGRESS ===
 
diff --git a/auto-claude/prompts_pkg/prompts.py b/auto-claude/prompts_pkg/prompts.py
index fcda78fa..95f7de47 100644
--- a/auto-claude/prompts_pkg/prompts.py
+++ b/auto-claude/prompts_pkg/prompts.py
@@ -9,7 +9,8 @@ import json
 from pathlib import Path
 
 # Directory containing prompt files
-PROMPTS_DIR = Path(__file__).parent / "prompts"
+# prompts/ is a sibling directory of prompts_pkg/, so go up one level first
+PROMPTS_DIR = Path(__file__).parent.parent / "prompts"
 
 
 def get_planner_prompt(spec_dir: Path) -> str:
@@ -38,10 +39,15 @@ def get_planner_prompt(spec_dir: Path) -> str:
 
 Your spec file is located at: `{spec_dir}/spec.md`
 
-Store all build artifacts in this spec directory:
-- `{spec_dir}/implementation_plan.json` - Subtask-based implementation plan
-- `{spec_dir}/build-progress.txt` - Progress notes
-- `{spec_dir}/init.sh` - Environment setup script
+🚨 CRITICAL FILE CREATION INSTRUCTIONS 🚨
+
+You MUST use the Write tool to create these files in the spec directory:
+- `{spec_dir}/implementation_plan.json` - Subtask-based implementation plan (USE WRITE TOOL!)
+- `{spec_dir}/build-progress.txt` - Progress notes (USE WRITE TOOL!)
+- `{spec_dir}/init.sh` - Environment setup script (USE WRITE TOOL!)
+
+DO NOT just describe what these files should contain. You MUST actually call the Write tool
+with the file path and complete content to create them.
 
 The project root is the parent of auto-claude/. Implement code in the project root, not in the spec directory.
 
diff --git a/auto-claude/runners/insights_runner.py b/auto-claude/runners/insights_runner.py
index f6fae98d..a2de9f94 100644
--- a/auto-claude/runners/insights_runner.py
+++ b/auto-claude/runners/insights_runner.py
@@ -331,7 +331,9 @@ def main():
     parser.add_argument("--project-dir", required=True, help="Project directory path")
     parser.add_argument("--message", required=True, help="User message")
     parser.add_argument("--history", default="[]", help="JSON conversation history")
-    parser.add_argument("--history-file", help="Path to JSON file containing conversation history")
+    parser.add_argument(
+        "--history-file", help="Path to JSON file containing conversation history"
+    )
     parser.add_argument(
         "--model",
         default="claude-sonnet-4-5-20250929",
@@ -364,13 +366,21 @@ def main():
     # Load history from file if provided, otherwise parse inline JSON
     try:
         if args.history_file:
-            debug("insights_runner", "Loading history from file", file=args.history_file)
-            with open(args.history_file, 'r', encoding='utf-8') as f:
+            debug(
+                "insights_runner", "Loading history from file", file=args.history_file
+            )
+            with open(args.history_file, encoding="utf-8") as f:
                 history = json.load(f)
-            debug_detailed("insights_runner", "Loaded history from file", history_length=len(history))
+            debug_detailed(
+                "insights_runner",
+                "Loaded history from file",
+                history_length=len(history),
+            )
         else:
             history = json.loads(args.history)
-            debug_detailed("insights_runner", "Parsed inline history", history_length=len(history))
+            debug_detailed(
+                "insights_runner", "Parsed inline history", history_length=len(history)
+            )
     except (json.JSONDecodeError, FileNotFoundError, OSError) as e:
         debug_error("insights_runner", f"Failed to load history: {e}")
         history = []
diff --git a/tests/test_merge_parallel.py b/tests/test_merge_parallel.py
index 41face5d..be2f9159 100644
--- a/tests/test_merge_parallel.py
+++ b/tests/test_merge_parallel.py
@@ -21,9 +21,7 @@ import pytest
 sys.path.insert(0, str(Path(__file__).parent.parent / "auto-claude"))
 
 from workspace import ParallelMergeTask, ParallelMergeResult
-
-# _run_parallel_merges is not yet implemented - tests that use it are skipped
-_run_parallel_merges = None
+from core.workspace import _run_parallel_merges
 
 
 class TestParallelMergeDataclasses:
@@ -101,11 +99,10 @@ class TestParallelMergeDataclasses:
 class TestParallelMergeRunner:
     """Tests for the parallel merge runner."""
 
-    @pytest.mark.skip(reason="_run_parallel_merges not yet implemented")
-    def test_run_parallel_merges_empty_list(self, project_dir):
+    def test_run_parallel_merges_empty_list(self, tmp_path):
         """Running with empty task list returns empty results."""
         import asyncio
-        results = asyncio.run(_run_parallel_merges([], project_dir))
+        results = asyncio.run(_run_parallel_merges([], tmp_path))
         assert results == []
 
     def test_parallel_merge_task_with_data(self):
@@ -123,6 +120,81 @@ class TestParallelMergeRunner:
         assert task.spec_name == "001-feature"
 
 
+class TestSimple3WayMerge:
+    """Tests for the simple 3-way merge logic."""
+
+    def test_identical_files_merge(self, tmp_path):
+        """When both versions are identical, return that version."""
+        import asyncio
+
+        task = ParallelMergeTask(
+            file_path="src/test.py",
+            main_content="def main(): pass",
+            worktree_content="def main(): pass",  # Same as main
+            base_content="def main(): pass",  # Same as both
+            spec_name="001-no-change",
+        )
+
+        results = asyncio.run(_run_parallel_merges([task], tmp_path))
+        assert len(results) == 1
+        assert results[0].success is True
+        assert results[0].was_auto_merged is True
+        assert results[0].merged_content == "def main(): pass"
+
+    def test_only_worktree_changed(self, tmp_path):
+        """When only worktree changed, take worktree version."""
+        import asyncio
+
+        task = ParallelMergeTask(
+            file_path="src/test.py",
+            main_content="def main(): pass",  # Same as base
+            worktree_content="def main():\n    print('new')",  # Changed
+            base_content="def main(): pass",
+            spec_name="001-worktree-only",
+        )
+
+        results = asyncio.run(_run_parallel_merges([task], tmp_path))
+        assert len(results) == 1
+        assert results[0].success is True
+        assert results[0].was_auto_merged is True
+        assert "print('new')" in results[0].merged_content
+
+    def test_only_main_changed(self, tmp_path):
+        """When only main changed, take main version."""
+        import asyncio
+
+        task = ParallelMergeTask(
+            file_path="src/test.py",
+            main_content="def main():\n    print('main')",  # Changed
+            worktree_content="def main(): pass",  # Same as base
+            base_content="def main(): pass",
+            spec_name="001-main-only",
+        )
+
+        results = asyncio.run(_run_parallel_merges([task], tmp_path))
+        assert len(results) == 1
+        assert results[0].success is True
+        assert results[0].was_auto_merged is True
+        assert "print('main')" in results[0].merged_content
+
+    def test_no_base_but_identical(self, tmp_path):
+        """When no base and both identical, return that version."""
+        import asyncio
+
+        task = ParallelMergeTask(
+            file_path="src/new.py",
+            main_content="# Same content",
+            worktree_content="# Same content",
+            base_content=None,  # New file, no base
+            spec_name="001-new-identical",
+        )
+
+        results = asyncio.run(_run_parallel_merges([task], tmp_path))
+        assert len(results) == 1
+        assert results[0].success is True
+        assert results[0].was_auto_merged is True
+
+
 class TestParallelMergeIntegration:
     """Integration tests for parallel merge flow."""