Add localhost->127.0.0.1 fallback for transcription fetch

src/models/media.test.ts

@@ -460,6 +460,28 @@ describe('transcribeAudio', () => {
     expect(global.fetch).toHaveBeenCalledTimes(2);
   });
 
+  it('falls back from localhost to 127.0.0.1 on transient fetch failures', async () => {
+    vi.mocked(global.fetch)
+      .mockRejectedValueOnce(new TypeError('fetch failed'))
+      .mockResolvedValueOnce({
+        ok: true,
+        json: async () => ({ text: mockTranscript }),
+      } as Response);
+
+    const config: AudioTranscriptionConfig = {
+      endpoint: 'http://localhost:18801/v1/audio/transcriptions',
+      apiKey: 'test-key',
+      model: 'test-model',
+    };
+
+    const result = await transcribeAudio(oggAudioAttachment, config);
+
+    expect(result).toBe(mockTranscript);
+    expect(global.fetch).toHaveBeenCalledTimes(2);
+    expect(vi.mocked(global.fetch).mock.calls[0]?.[0]).toBe('http://localhost:18801/v1/audio/transcriptions');
+    expect(vi.mocked(global.fetch).mock.calls[1]?.[0]).toBe('http://127.0.0.1:18801/v1/audio/transcriptions');
+  });
+
   // Positive: uses Whisper-1 model by default.
   it('uses whisper-1 model by default', async () => {
     const config: AudioTranscriptionConfig = {

src/models/media.ts

@@ -44,22 +44,42 @@ function isTransientNetworkError(error: unknown): boolean {
     || message.includes('ehostunreach');
 }
 
+function buildEndpointCandidates(endpoint: string): string[] {
+  try {
+    const parsed = new URL(endpoint);
+    if (parsed.hostname !== 'localhost') {
+      return [endpoint];
+    }
+    const ipv4Endpoint = new URL(endpoint);
+    ipv4Endpoint.hostname = '127.0.0.1';
+    return [endpoint, ipv4Endpoint.toString()];
+  } catch {
+    return [endpoint];
+  }
+}
+
 async function fetchTranscriptionWithRetry(endpoint: string, init: RequestInit): Promise<Response> {
+  const endpointCandidates = buildEndpointCandidates(endpoint);
+  let lastErrorMessage = 'Unknown network error';
+  let lastEndpoint = endpoint;
   for (let attempt = 1; attempt <= TRANSCRIPTION_FETCH_MAX_ATTEMPTS; attempt += 1) {
+    const endpointForAttempt = endpointCandidates[(attempt - 1) % endpointCandidates.length];
     const controller = new AbortController();
     const timeout = setTimeout(() => controller.abort(), TRANSCRIPTION_FETCH_TIMEOUT_MS);
     try {
-      return await fetch(endpoint, { ...init, signal: controller.signal });
+      return await fetch(endpointForAttempt, { ...init, signal: controller.signal });
     } catch (error) {
       const timedOut = error instanceof Error && error.name === 'AbortError';
       const retriable = timedOut || isTransientNetworkError(error);
       const normalizedMessage = timedOut
         ? `request timed out after ${TRANSCRIPTION_FETCH_TIMEOUT_MS}ms`
         : (error instanceof Error ? error.message : String(error));
+      lastErrorMessage = normalizedMessage;
+      lastEndpoint = endpointForAttempt;
       const exhausted = attempt >= TRANSCRIPTION_FETCH_MAX_ATTEMPTS;
       if (!retriable || exhausted) {
         throw new Error(
-          `Transcription request to ${endpoint} failed after ${attempt} attempt(s): ${normalizedMessage}`,
+          `Transcription service connectivity failure at ${lastEndpoint} after ${attempt} attempt(s): ${normalizedMessage}. This indicates endpoint/network availability, not missing audio bytes.`,
         );
       }
       await sleep(TRANSCRIPTION_FETCH_BASE_DELAY_MS * (2 ** (attempt - 1)));
@@ -68,7 +88,9 @@ async function fetchTranscriptionWithRetry(endpoint: string, init: RequestInit):
     }
   }
 
-  throw new Error(`Transcription request to ${endpoint} failed after retries`);
+  throw new Error(
+    `Transcription service connectivity failure at ${lastEndpoint} after retries: ${lastErrorMessage}. This indicates endpoint/network availability, not missing audio bytes.`,
+  );
 }
 
 /** Check whether an attachment is a supported image type. */

src/tools/builtin/audio-transcribe.test.ts

@@ -335,10 +335,30 @@ describe('createAudioTranscribeTool', () => {
 
       const result = await tool.execute({ data: 'AAAAAAA=', mime_type: 'audio/wav' });
       expect(result.success).toBe(false);
-      expect(result.error).toMatch(/failed after 3 attempt/);
+      expect(result.error).toMatch(/connectivity failure/i);
       expect(result.error).toMatch(/audio\/transcriptions/);
     });
 
+    it('falls back from localhost to 127.0.0.1 for transient fetch failures', async () => {
+      const localhostTool = createAudioTranscribeTool({
+        endpoint: 'http://localhost:18801/v1/audio/transcriptions',
+        model: 'whisper-1',
+      });
+      mockFetch
+        .mockRejectedValueOnce(new TypeError('fetch failed'))
+        .mockResolvedValueOnce({
+          ok: true,
+          text: async () => JSON.stringify({ text: 'Local fallback transcript' }),
+        });
+
+      const result = await localhostTool.execute({ data: 'AAAAAAA=', mime_type: 'audio/wav' });
+      expect(result.success).toBe(true);
+      expect(result.output).toBe('Local fallback transcript');
+      expect(mockFetch).toHaveBeenCalledTimes(2);
+      expect(mockFetch.mock.calls[0][0]).toBe('http://localhost:18801/v1/audio/transcriptions');
+      expect(mockFetch.mock.calls[1][0]).toBe('http://127.0.0.1:18801/v1/audio/transcriptions');
+    });
+
     it('returns clear error when transcription payload has no text field', async () => {
       mockFetch.mockResolvedValueOnce({
         ok: true,

src/tools/builtin/audio-transcribe.ts

@@ -45,22 +45,42 @@ function isTransientNetworkError(error: unknown): boolean {
     || message.includes('ehostunreach');
 }
 
+function buildEndpointCandidates(endpoint: string): string[] {
+  try {
+    const parsed = new URL(endpoint);
+    if (parsed.hostname !== 'localhost') {
+      return [endpoint];
+    }
+    const ipv4Endpoint = new URL(endpoint);
+    ipv4Endpoint.hostname = '127.0.0.1';
+    return [endpoint, ipv4Endpoint.toString()];
+  } catch {
+    return [endpoint];
+  }
+}
+
 async function fetchWithRetry(endpoint: string, init: RequestInit): Promise<Response> {
+  const endpointCandidates = buildEndpointCandidates(endpoint);
+  let lastErrorMessage = 'Unknown network error';
+  let lastEndpoint = endpoint;
   for (let attempt = 1; attempt <= TRANSCRIPTION_FETCH_MAX_ATTEMPTS; attempt += 1) {
+    const endpointForAttempt = endpointCandidates[(attempt - 1) % endpointCandidates.length];
     const controller = new AbortController();
     const timeout = setTimeout(() => controller.abort(), TRANSCRIPTION_FETCH_TIMEOUT_MS);
     try {
-      return await fetch(endpoint, { ...init, signal: controller.signal });
+      return await fetch(endpointForAttempt, { ...init, signal: controller.signal });
     } catch (error) {
       const timedOut = error instanceof Error && error.name === 'AbortError';
       const normalizedMessage = timedOut
         ? `request timed out after ${TRANSCRIPTION_FETCH_TIMEOUT_MS}ms`
         : (error instanceof Error ? error.message : String(error));
+      lastErrorMessage = normalizedMessage;
+      lastEndpoint = endpointForAttempt;
       const retriable = timedOut || isTransientNetworkError(error);
       const exhausted = attempt >= TRANSCRIPTION_FETCH_MAX_ATTEMPTS;
       if (!retriable || exhausted) {
         throw new Error(
-          `Transcription request to ${endpoint} failed after ${attempt} attempt(s): ${normalizedMessage}`,
+          `Transcription service connectivity failure at ${lastEndpoint} after ${attempt} attempt(s): ${normalizedMessage}. This indicates endpoint/network availability, not missing audio bytes.`,
         );
       }
       await sleep(TRANSCRIPTION_FETCH_BASE_DELAY_MS * (2 ** (attempt - 1)));
@@ -69,7 +89,9 @@ async function fetchWithRetry(endpoint: string, init: RequestInit): Promise<Resp
     }
   }
 
-  throw new Error(`Transcription request to ${endpoint} failed after retries`);
+  throw new Error(
+    `Transcription service connectivity failure at ${lastEndpoint} after retries: ${lastErrorMessage}. This indicates endpoint/network availability, not missing audio bytes.`,
+  );
 }
 
 function validateUrl(url: string): { valid: boolean; error?: string } {