diff --git a/packages/ui/src/lib/openchamberEvents.test.ts b/packages/ui/src/lib/openchamberEvents.test.ts
index e24e4b5e..0667eb89 100644
--- a/packages/ui/src/lib/openchamberEvents.test.ts
+++ b/packages/ui/src/lib/openchamberEvents.test.ts
@@ -1,12 +1,4 @@
-import { afterEach, beforeEach, describe, expect, mock, test } from 'bun:test';
-
-mock.module('./runtime-url', () => ({
-  getRuntimeUrlResolver: () => ({ sse: (path: string) => `http://runtime.test${path}` }),
-}));
-
-mock.module('./runtime-switch', () => ({
-  subscribeRuntimeEndpointChanged: () => () => undefined,
-}));
+import { afterEach, beforeEach, describe, expect, test } from 'bun:test';
 
 class MockEventSource {
   static CLOSED = 2;
@@ -29,20 +21,37 @@ class MockEventSource {
 describe('openchamber events', () => {
   beforeEach(() => {
     MockEventSource.instances = [];
-    globalThis.window = {} as Window & typeof globalThis;
-    globalThis.EventSource = MockEventSource as unknown as typeof EventSource;
+    Object.defineProperty(globalThis, 'window', {
+      value: Object.assign(new EventTarget(), { location: new URL('http://runtime.test') }),
+      configurable: true,
+      writable: true,
+    });
+    Object.defineProperty(globalThis, 'EventSource', { value: MockEventSource, configurable: true, writable: true });
   });
 
   afterEach(() => {
-    delete (globalThis as { window?: unknown }).window;
-    delete (globalThis as { EventSource?: unknown }).EventSource;
+    Reflect.deleteProperty(globalThis, 'window');
+    Reflect.deleteProperty(globalThis, 'EventSource');
+  });
+
+  test('does not open the server-only event stream in VS Code', async () => {
+    Object.defineProperty(window, '__VSCODE_CONFIG__', {
+      value: { workspaceFolder: 'C:/repo', workspaceFolders: [] },
+      configurable: true,
+    });
+    const { subscribeOpenchamberEvents } = await import('./openchamberEvents');
+    const unsubscribe = subscribeOpenchamberEvents(() => undefined);
+    try {
+      expect(MockEventSource.instances).toHaveLength(0);
+    } finally {
+      unsubscribe();
+    }
   });
 
   test('dispatches externally created session events', async () => {
     const { subscribeOpenchamberEvents } = await import('./openchamberEvents');
     const events: unknown[] = [];
-    const listener = (event: unknown) => events.push(event);
-    const unsubscribe = subscribeOpenchamberEvents(listener);
+    const unsubscribe = subscribeOpenchamberEvents((event) => events.push(event));
     const source = MockEventSource.instances[0];
 
     source.onmessage?.({
diff --git a/packages/ui/src/lib/openchamberEvents.ts b/packages/ui/src/lib/openchamberEvents.ts
index 9baa6020..60650884 100644
--- a/packages/ui/src/lib/openchamberEvents.ts
+++ b/packages/ui/src/lib/openchamberEvents.ts
@@ -1,5 +1,6 @@
 import { getRuntimeUrlResolver } from './runtime-url';
 import { subscribeRuntimeEndpointChanged } from './runtime-switch';
+import { isVSCodeRuntime } from './desktop';
 
 type ScheduledTaskRanEvent = {
   type: 'scheduled-task-ran';
@@ -284,6 +285,10 @@ const cleanupRuntimeChangeSubscription = () => {
 };
 
 export const subscribeOpenchamberEvents = (listener: Listener): (() => void) => {
+  // VS Code runs OpenCode through its bridge, not the OpenChamber server that
+  // owns this stream. Opening it here retries against vscode-webview:// forever.
+  if (isVSCodeRuntime()) return () => undefined;
+
   listeners.add(listener);
   ensureRuntimeChangeSubscription();
   connect();
diff --git a/packages/vscode/src/DOCUMENTATION.md b/packages/vscode/src/DOCUMENTATION.md
index 89bfa666..b02d1977 100644
--- a/packages/vscode/src/DOCUMENTATION.md
+++ b/packages/vscode/src/DOCUMENTATION.md
@@ -103,6 +103,13 @@ The webview build emits each worker as one self-contained file. VS Code webviews
 
 Message and part ordering is owned by [`packages/ui/src/sync/DOCUMENTATION.md`](../../ui/src/sync/DOCUMENTATION.md#session-message-loading). The VS Code webview consumes that shared sync implementation; bridge and proxy runtimes pass OpenCode records through without adding runtime-specific ordering.
 
+The OpenChamber control stream (`/api/openchamber/events`) requires the
+OpenChamber server, which the extension does not run. `subscribeOpenchamberEvents`
+therefore returns a no-op subscription in VS Code before resolving URLs or
+opening a connection. Session sync still uses the OpenCode SSE bridge and
+global session polling. Sending the control stream to the webview origin caused
+repeated `403` responses and URL-token requests to `/auth/url-token`.
+
 ## Extension guideline
 
 When adding new bridge route families: