fix(vscode,ui): stop postMessage crash when opening chat in Cursor (#2335)

VS Code webviews delete window.parent, so ChatContainer's settings-sync
effect threw TypeError on chat open. Also harden the webview bridge when
acquireVsCodeApi() returns undefined and SSE panel disposal races.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/vscode/webview/api/bridge-acquire-fallback.test.ts

@@ -0,0 +1,51 @@
+import { describe, test } from 'node:test';
+import assert from 'node:assert/strict';
+
+/**
+ * When acquireVsCodeApi() returns undefined (broken Cursor/VSCodium webview slot),
+ * getVSCodeAPI().postMessage used to throw:
+ * TypeError: Cannot read properties of undefined (reading 'postMessage')
+ *
+ * The bridge must fall back to a noop API and fail via normal request timeout instead.
+ */
+describe('VS Code webview bridge acquireVsCodeApi fallback', () => {
+  test('does not throw TypeError when acquireVsCodeApi returns undefined', async () => {
+    const originalWindow = globalThis.window;
+    const originalAcquire = (globalThis as typeof globalThis & { acquireVsCodeApi?: unknown }).acquireVsCodeApi;
+    const originalWarn = console.warn;
+    const warnings: unknown[][] = [];
+
+    try {
+      Object.defineProperty(globalThis, 'window', {
+        configurable: true,
+        value: new EventTarget(),
+      });
+      Object.defineProperty(globalThis, 'acquireVsCodeApi', {
+        configurable: true,
+        value: () => undefined,
+      });
+      console.warn = (...args: unknown[]) => {
+        warnings.push(args);
+      };
+
+      const { sendBridgeMessageWithOptions } = await import(`./bridge?acquire-fallback-${Date.now()}`);
+
+      const result = await sendBridgeMessageWithOptions('api:proxy', { path: '/health' }, { timeoutMs: 20 }).then(
+        () => 'resolved' as const,
+        (error: unknown) => error,
+      );
+
+      assert.ok(result instanceof Error, `expected Error, got ${String(result)}`);
+      assert.notEqual((result as Error).name, 'TypeError');
+      assert.match((result as Error).message, /timed out/i);
+      assert.ok(
+        warnings.some((entry) => String(entry[0] ?? '').includes('VS Code API unavailable')),
+        'expected a one-time warning that the VS Code API was unavailable',
+      );
+    } finally {
+      console.warn = originalWarn;
+      Object.defineProperty(globalThis, 'window', { configurable: true, value: originalWindow });
+      Object.defineProperty(globalThis, 'acquireVsCodeApi', { configurable: true, value: originalAcquire });
+    }
+  });
+});

packages/vscode/webview/api/bridge.ts

@@ -9,10 +9,24 @@ interface VSCodeAPI {
 }
 
 let vscodeApi: VSCodeAPI | null = null;
+let noopWarned = false;
+
+const noopVSCodeApi: VSCodeAPI = {
+  postMessage: (message) => {
+    // acquireVsCodeApi() can return undefined in broken/non-standard webview slots
+    // (Cursor after extension update, VSCodium, headless). Drop the message instead
+    // of throwing TypeError: Cannot read properties of undefined (reading 'postMessage').
+    if (!noopWarned) {
+      noopWarned = true;
+      console.warn('[openchamber] VS Code API unavailable; dropping postMessage', message);
+    }
+  },
+};
 
 function getVSCodeAPI(): VSCodeAPI {
   if (!vscodeApi) {
-    vscodeApi = acquireVsCodeApi();
+    const acquired = typeof acquireVsCodeApi === 'function' ? acquireVsCodeApi() : undefined;
+    vscodeApi = acquired ?? noopVSCodeApi;
   }
   return vscodeApi;
 }