diff --git a/src/offscreen/recorder.ts b/src/offscreen/recorder.ts
index 3fab2f4..a86caf2 100644
--- a/src/offscreen/recorder.ts
+++ b/src/offscreen/recorder.ts
@@ -105,6 +105,14 @@ export function resetBuffer(): void {
 
 // ─── Проверка кодека (D-20 strict-mode — no fallback chain) ─────────────
 
+// WR-02 fix: assertCodecSupported is a PURE predicate that throws. The
+// previous implementation broadcast a RECORDING_ERROR before throwing,
+// which violated single responsibility (a function named `assert*`
+// shouldn't have side effects) AND double-emitted with the
+// startRecording catch block — popup received two RECORDING_ERROR
+// messages for the same underlying problem. The single-source-of-truth
+// for the broadcast is now `startRecording`'s catch block via
+// classifyCaptureError.
 export function assertCodecSupported(): void {
   const supported =
     typeof MediaRecorder !== 'undefined' &&
@@ -112,12 +120,79 @@ export function assertCodecSupported(): void {
     MediaRecorder.isTypeSupported(VIDEO_MIME);
   if (!supported) {
     const ua = typeof navigator !== 'undefined' ? navigator.userAgent : '<unknown>';
-    const errMessage = `vp9 unsupported. UA=${ua}`;
-    chrome.runtime.sendMessage({ type: 'RECORDING_ERROR', error: errMessage });
-    throw new Error(errMessage);
+    throw new Error(`vp9 unsupported. UA=${ua}`);
   }
 }
 
+// WR-01 fix: classify capture-pipeline failures into a stable,
+// programmatically actionable error code. The previous implementation
+// forwarded the raw DOMException message ("Permission denied by user",
+// "Could not start video source", etc.) which changes between Chrome
+// versions and locales. The popup / future telemetry needs a stable
+// vocabulary — a string union the SW can switch on. The raw browser
+// error stays in the logs at warn level for forensic value.
+//
+// Codes:
+//   'user-cancelled'      — operator dismissed the getDisplayMedia picker
+//                           (DOMException name 'NotAllowedError' with no
+//                           system-permission denial context).
+//   'permission-denied'   — system-level screen-recording permission denied
+//                           by the OS (macOS Screen Recording privacy
+//                           toggle, etc.). NotAllowedError + DOMException
+//                           message hints OR SecurityError.
+//   'codec-unsupported'   — assertCodecSupported() threw; vp9 not in
+//                           MediaRecorder.isTypeSupported.
+//   'no-source-selected'  — NotFoundError: picker yielded no source
+//                           (rare; theoretically impossible if the picker
+//                           closes via Cancel — that is NotAllowedError).
+//   'capture-failed'      — AbortError / generic stream-acquisition failure.
+//   'unknown'             — anything else; we still log the raw error.
+export type CaptureErrorCode =
+  | 'user-cancelled'
+  | 'permission-denied'
+  | 'codec-unsupported'
+  | 'no-source-selected'
+  | 'capture-failed'
+  | 'unknown';
+
+export function classifyCaptureError(error: unknown): CaptureErrorCode {
+  if (error instanceof Error) {
+    // Our own assertion is the cleanest signal — it never wraps a
+    // DOMException, so prefix-matching is safe and stable.
+    if (error.message.startsWith('vp9 unsupported')) {
+      return 'codec-unsupported';
+    }
+    // DOMException has a stable `name` field per the WebIDL standard:
+    // https://webidl.spec.whatwg.org/#idl-DOMException
+    // The name does NOT vary between Chrome versions or locales, unlike
+    // the human-readable message — exactly what we want for routing.
+    const name = (error as { name?: string }).name;
+    if (name === 'NotAllowedError') {
+      // Distinguish system-permission denial from user-cancel by sniffing
+      // the message for the "system" keyword Chrome uses on macOS denial
+      // ("Permission denied by system"). On Linux/Windows the system case
+      // is typically wrapped as a SecurityError instead — handled below.
+      // The message text is locale-stable for English Chrome; for other
+      // locales we fall back to 'user-cancelled' which is the dominant
+      // NotAllowedError path in practice.
+      if (/system/i.test(error.message)) {
+        return 'permission-denied';
+      }
+      return 'user-cancelled';
+    }
+    if (name === 'SecurityError') {
+      return 'permission-denied';
+    }
+    if (name === 'NotFoundError') {
+      return 'no-source-selected';
+    }
+    if (name === 'AbortError') {
+      return 'capture-failed';
+    }
+  }
+  return 'unknown';
+}
+
 // ─── Захват экрана (getDisplayMedia inside offscreen — D-01) ────────────
 
 async function startRecording(): Promise<void> {
@@ -150,9 +225,13 @@ async function startRecording(): Promise<void> {
       'max_segments:', MAX_SEGMENTS,
     );
   } catch (error) {
+    // WR-01: emit a stable error code, not the raw DOMException message.
+    // Raw message stays in logs at warn level for forensic value.
+    const code = classifyCaptureError(error);
     const msg = error instanceof Error ? error.message : String(error);
-    logger.error('startRecording failed:', msg);
-    chrome.runtime.sendMessage({ type: 'RECORDING_ERROR', error: msg });
+    logger.warn('startRecording failed (raw):', msg);
+    logger.error('startRecording failed (code):', code);
+    chrome.runtime.sendMessage({ type: 'RECORDING_ERROR', error: code });
     throw error;
   }
 }
diff --git a/tests/offscreen/codec-check.test.ts b/tests/offscreen/codec-check.test.ts
index ea52caa..f6468e8 100644
--- a/tests/offscreen/codec-check.test.ts
+++ b/tests/offscreen/codec-check.test.ts
@@ -17,14 +17,23 @@ describe('codec strict mode', () => {
     };
   });
 
-  it('throws on unsupported vp9 and emits RECORDING_ERROR', async () => {
+  // WR-02 fix: assertCodecSupported is a pure predicate that throws.
+  // The previous spec expected a RECORDING_ERROR broadcast from inside
+  // the assertion; that side-effect was removed (single-responsibility +
+  // it double-emitted with startRecording's catch block). The notify is
+  // now solely the caller's (startRecording's) responsibility — exercised
+  // via integration through `classifyCaptureError` rather than from this
+  // unit test, since `startRecording` requires a full getDisplayMedia
+  // stub that jsdom does not provide.
+  it('throws on unsupported vp9 (pure assertion, no side-effect)', async () => {
     (globalThis as unknown as GlobalWithChrome).MediaRecorder = {
       isTypeSupported: vi.fn().mockReturnValue(false),
     };
     const mod = await import('../../src/offscreen/recorder');
     expect(() => mod.assertCodecSupported()).toThrow(/vp9 unsupported/);
     const stub = (globalThis as unknown as GlobalWithChrome).chrome!;
-    expect(stub.runtime.sendMessage).toHaveBeenCalledWith(
+    // The assertion itself MUST NOT emit RECORDING_ERROR.
+    expect(stub.runtime.sendMessage).not.toHaveBeenCalledWith(
       expect.objectContaining({ type: 'RECORDING_ERROR' })
     );
   });
@@ -41,3 +50,74 @@ describe('codec strict mode', () => {
     );
   });
 });
+
+// WR-01 fix: classifyCaptureError maps DOMException / Error shapes to a
+// stable string union. The popup / SW route can switch on the code
+// instead of substring-matching DOMException.message — message text
+// changes between Chrome versions and locales, name and prototype do not.
+describe('classifyCaptureError (WR-01 stable error codes)', () => {
+  beforeEach(() => {
+    vi.resetModules();
+    (globalThis as unknown as GlobalWithChrome).chrome = {
+      runtime: { sendMessage: vi.fn() },
+    };
+    (globalThis as unknown as GlobalWithChrome).MediaRecorder = {
+      isTypeSupported: vi.fn().mockReturnValue(true),
+    };
+  });
+
+  function makeDomError(name: string, message: string): Error {
+    const e = new Error(message);
+    (e as { name: string }).name = name;
+    return e;
+  }
+
+  it('codec error → "codec-unsupported"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(new Error('vp9 unsupported. UA=<test>'))).toBe(
+      'codec-unsupported',
+    );
+  });
+
+  it('NotAllowedError (no system hint) → "user-cancelled"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(
+      mod.classifyCaptureError(makeDomError('NotAllowedError', 'Permission denied by user')),
+    ).toBe('user-cancelled');
+  });
+
+  it('NotAllowedError with "system" in message → "permission-denied"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(
+      mod.classifyCaptureError(makeDomError('NotAllowedError', 'Permission denied by system')),
+    ).toBe('permission-denied');
+  });
+
+  it('SecurityError → "permission-denied"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(makeDomError('SecurityError', 'blocked'))).toBe(
+      'permission-denied',
+    );
+  });
+
+  it('NotFoundError → "no-source-selected"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(makeDomError('NotFoundError', 'no source'))).toBe(
+      'no-source-selected',
+    );
+  });
+
+  it('AbortError → "capture-failed"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(makeDomError('AbortError', 'aborted'))).toBe(
+      'capture-failed',
+    );
+  });
+
+  it('arbitrary error → "unknown"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(new Error('totally novel failure'))).toBe('unknown');
+    expect(mod.classifyCaptureError('a bare string')).toBe('unknown');
+    expect(mod.classifyCaptureError(null)).toBe('unknown');
+  });
+});