diff --git a/src/browser/errors.test.ts b/src/browser/errors.test.ts
index 8f2897a3c..98c977453 100644
--- a/src/browser/errors.test.ts
+++ b/src/browser/errors.test.ts
@@ -12,6 +12,9 @@ describe('classifyBrowserError', () => {
       'CDP connection reset',
       'Daemon command failed',
       'No window with id: 123',
+      'Detached while handling command id=cmd_42',
+      'No tab with id: 456',
+      'Debugger is not attached to the tab',
     ]) {
       const advice = classifyBrowserError(new Error(msg));
       expect(advice.kind, `expected "${msg}" → extension-transient`).toBe('extension-transient');
diff --git a/src/browser/errors.ts b/src/browser/errors.ts
index 1889b2f2e..e9426763f 100644
--- a/src/browser/errors.ts
+++ b/src/browser/errors.ts
@@ -45,6 +45,14 @@ const EXTENSION_TRANSIENT_PATTERNS = [
   'CDP connection',
   'Daemon command failed',
   'No window with id',
+  // CDP debugger detach race — daemon detaches a command while still serving
+  // it under concurrent load. Already treated as transient in the e2e
+  // test harness (tests/e2e/browser-public.test.ts isTransientBrowserDetach),
+  // but classifyBrowserError did not list it, so CLI runtime would surface
+  // it as a hard 500 to callers instead of retrying.
+  'Detached while handling command',
+  'No tab with id',
+  'Debugger is not attached to the tab',
 ] as const;
 
 /**