fix(cursor): guard raw-settings save race and enforce daemon preconditions

src/web-server/routes/cursor-routes.ts

@@ -20,6 +20,44 @@ import cursorSettingsRoutes from './cursor-settings-routes';
 
 const router = Router();
 
+interface DaemonStartPreconditionInput {
+  enabled: boolean;
+  authenticated: boolean;
+  tokenExpired?: boolean;
+}
+
+interface DaemonStartPreconditionError {
+  status: number;
+  error: string;
+}
+
+export function getDaemonStartPreconditionError(
+  input: DaemonStartPreconditionInput
+): DaemonStartPreconditionError | null {
+  if (!input.enabled) {
+    return {
+      status: 400,
+      error: 'Cursor integration is disabled. Enable it before starting daemon.',
+    };
+  }
+
+  if (!input.authenticated) {
+    return {
+      status: 401,
+      error: 'Cursor authentication required. Import credentials before starting daemon.',
+    };
+  }
+
+  if (input.tokenExpired) {
+    return {
+      status: 401,
+      error: 'Cursor credentials expired. Re-authenticate before starting daemon.',
+    };
+  }
+
+  return null;
+}
+
 // Mount settings sub-routes
 router.use('/settings', cursorSettingsRoutes);
 
@@ -125,6 +163,21 @@ router.get('/models', async (_req: Request, res: Response): Promise<void> => {
 router.post('/daemon/start', async (_req: Request, res: Response): Promise<void> => {
   try {
     const cursorConfig = getCursorConfig();
+    const authStatus = checkAuthStatus();
+    const preconditionError = getDaemonStartPreconditionError({
+      enabled: cursorConfig.enabled,
+      authenticated: authStatus.authenticated,
+      tokenExpired: authStatus.expired ?? false,
+    });
+
+    if (preconditionError) {
+      res.status(preconditionError.status).json({
+        success: false,
+        error: preconditionError.error,
+      });
+      return;
+    }
+
     const result = await startDaemon({
       port: cursorConfig.port,
       ghost_mode: cursorConfig.ghost_mode,

src/web-server/routes/cursor-settings-routes.ts

@@ -162,9 +162,17 @@ router.put('/raw', (req: Request, res: Response): void => {
 
     const settingsPath = path.join(getCcsDir(), 'cursor.settings.json');
 
-    // Check for conflict if file exists and expectedMtime provided
+    // For existing files, expectedMtime is required to prevent blind overwrite races.
-    if (fs.existsSync(settingsPath) && expectedMtime) {
+    if (fs.existsSync(settingsPath)) {
       const stat = fs.statSync(settingsPath);
+      if (typeof expectedMtime !== 'number' || !Number.isFinite(expectedMtime)) {
+        res.status(409).json({
+          error: 'File metadata not loaded. Refresh and retry.',
+          mtime: stat.mtimeMs,
+        });
+        return;
+      }
+
       if (Math.abs(stat.mtimeMs - expectedMtime) > 1000) {
         res.status(409).json({ error: 'File modified externally', mtime: stat.mtimeMs });
         return;

tests/unit/web-server/cursor-routes.test.ts

@@ -0,0 +1,60 @@
+/**
+ * Cursor Routes Tests
+ * Tests for daemon start precondition validation logic.
+ */
+
+import { describe, it, expect } from 'bun:test';
+import { getDaemonStartPreconditionError } from '../../../src/web-server/routes/cursor-routes';
+
+describe('Cursor Routes Logic', () => {
+  describe('POST /daemon/start preconditions', () => {
+    it('blocks start when integration is disabled', () => {
+      const result = getDaemonStartPreconditionError({
+        enabled: false,
+        authenticated: true,
+        tokenExpired: false,
+      });
+
+      expect(result).toEqual({
+        status: 400,
+        error: 'Cursor integration is disabled. Enable it before starting daemon.',
+      });
+    });
+
+    it('blocks start when not authenticated', () => {
+      const result = getDaemonStartPreconditionError({
+        enabled: true,
+        authenticated: false,
+        tokenExpired: false,
+      });
+
+      expect(result).toEqual({
+        status: 401,
+        error: 'Cursor authentication required. Import credentials before starting daemon.',
+      });
+    });
+
+    it('blocks start when token is expired', () => {
+      const result = getDaemonStartPreconditionError({
+        enabled: true,
+        authenticated: true,
+        tokenExpired: true,
+      });
+
+      expect(result).toEqual({
+        status: 401,
+        error: 'Cursor credentials expired. Re-authenticate before starting daemon.',
+      });
+    });
+
+    it('allows start when all preconditions are met', () => {
+      const result = getDaemonStartPreconditionError({
+        enabled: true,
+        authenticated: true,
+        tokenExpired: false,
+      });
+
+      expect(result).toBeNull();
+    });
+  });
+});

tests/unit/web-server/cursor-settings-routes.test.ts

@@ -284,6 +284,32 @@ describe('Cursor Settings Routes Logic', () => {
       expect(hasConflict).toBe(true);
     });
 
+    it('requires expectedMtime when file already exists', () => {
+      const settingsPath = path.join(getCcsDir(), 'cursor.settings.json');
+      fs.writeFileSync(settingsPath, JSON.stringify({ env: { test: 'existing' } }));
+
+      const expectedMtime = undefined;
+      const shouldRequireMtime =
+        fs.existsSync(settingsPath) &&
+        (typeof expectedMtime !== 'number' || !Number.isFinite(expectedMtime));
+
+      expect(shouldRequireMtime).toBe(true);
+    });
+
+    it('does not require expectedMtime when file does not exist', () => {
+      const settingsPath = path.join(getCcsDir(), 'cursor.settings.json');
+      if (fs.existsSync(settingsPath)) {
+        fs.rmSync(settingsPath, { force: true });
+      }
+
+      const expectedMtime = undefined;
+      const shouldRequireMtime =
+        fs.existsSync(settingsPath) &&
+        (typeof expectedMtime !== 'number' || !Number.isFinite(expectedMtime));
+
+      expect(shouldRequireMtime).toBe(false);
+    });
+
     it('allows write when mtime matches', () => {
       const settingsPath = path.join(getCcsDir(), 'cursor.settings.json');
       const initialSettings = { env: { test: 'initial' } };

ui/src/pages/cursor.tsx

@@ -134,6 +134,8 @@ export function CursorPage() {
   const effectiveRawConfigText = rawConfigDirty
     ? rawConfigText
     : JSON.stringify(rawSettings?.settings ?? {}, null, 2);
+  const rawSettingsReady = Boolean(rawSettings);
+  const disableRawSave = isSavingRawSettings || rawSettingsLoading || !rawSettingsReady;
 
   const updateConfigDraft = (updater: (draft: CursorConfigDraft) => CursorConfigDraft) => {
     setConfigDraft((previousDraft) => {
@@ -241,6 +243,11 @@ export function CursorPage() {
   };
 
   const handleSaveRawSettings = async () => {
+    if (!rawSettingsReady) {
+      toast.error('Raw settings are still loading. Please wait and try again.');
+      return;
+    }
+
     let parsed: unknown;
     try {
       parsed = JSON.parse(effectiveRawConfigText || '{}');
@@ -570,7 +577,7 @@ export function CursorPage() {
                         />
                         Refresh
                       </Button>
-                      <Button onClick={handleSaveRawSettings} disabled={isSavingRawSettings}>
+                      <Button onClick={handleSaveRawSettings} disabled={disableRawSave}>
                         {isSavingRawSettings ? (
                           <Loader2 className="w-4 h-4 mr-2 animate-spin" />
                         ) : (