fix(tts): request a browser-playable format from custom providers

`generateOpenAITTS` serves every custom OpenAI-compatible TTS provider but
never sent `response_format`, so it inherited whatever each provider
defaults to. OpenAI defaults to mp3; OpenRouter's /audio/speech defaults
to raw `pcm`. The unknown content type then fell through to the `'mp3'`
default below, the client built `data:audio/mp3;base64,…` from headerless
PCM samples, and playback failed with "no supported source was found" —
while the server logged a clean 200, because the audio really was
generated. Name the format instead of inheriting it.

Also stop mislabelling an unrecognised body: `pcm`/`l16` now raises a
message naming the cause, and `aac`/`opus` are recognised.

Two supporting fixes:

- /api/openrouter-models normalises its base URL the way the adapters do
  and falls back to the public catalog when a custom base URL fails, so a
  typo in a free-text settings field cannot empty the model picker. Also
  types the headers object so tsc accepts the conditional.
- provider-neutrality-guard pins exact per-vendor occurrence counts in
  lib/server/provider-config.ts. Adding the image and video env entries
  raises "openrouter" from 2 to 6 (each entry contributes both its key and
  its value); CI failed without the bump.

Closes #1355

app/api/openrouter-models/route.ts

@@ -16,7 +16,10 @@
  */
 import type { NextRequest } from 'next/server';
 
-import { OPENROUTER_DEFAULT_BASE_URL } from '@/lib/media/adapters/openrouter-image-adapter';
+import {
+  OPENROUTER_DEFAULT_BASE_URL,
+  openRouterBaseUrl,
+} from '@/lib/media/adapters/openrouter-image-adapter';
 import { apiError } from '@/lib/server/api-response';
 
 export const runtime = 'nodejs';
@@ -47,12 +50,14 @@ export async function GET(req: NextRequest) {
     req.headers.get('x-api-key')?.trim() ||
     '';
 
-  const baseUrl =
+  // Same normalisation the adapters use: a saved base URL that already ends in
+  // /images or /videos would otherwise ask for `/images/images/models` and 404.
+  const baseUrl = openRouterBaseUrl(
     req.headers.get('x-base-url')?.trim() ||
-    (kind === 'image'
-      ? process.env.IMAGE_OPENROUTER_BASE_URL?.trim()
-      : process.env.VIDEO_OPENROUTER_BASE_URL?.trim()) ||
-    OPENROUTER_DEFAULT_BASE_URL;
+      (kind === 'image'
+        ? process.env.IMAGE_OPENROUTER_BASE_URL?.trim()
+        : process.env.VIDEO_OPENROUTER_BASE_URL?.trim()),
+  );
 
   const cacheKey = `${kind}:${baseUrl}`;
   const hit = cache.get(cacheKey);
@@ -60,18 +65,20 @@ export async function GET(req: NextRequest) {
     return Response.json({ models: hit.models, cached: true });
   }
 
-  let upstream: Response;
-  try {
-    upstream = await fetch(`${baseUrl}/${kind}s/models`, {
-      method: 'GET',
-      headers: apiKey ? { Authorization: `Bearer ${apiKey}` } : {},
-    });
-  } catch {
-    return apiError('UPSTREAM_ERROR', 502, `unable to reach ${baseUrl}`);
+  const headers: Record<string, string> = apiKey ? { Authorization: `Bearer ${apiKey}` } : {};
+  const read = (base: string) =>
+    fetch(`${base}/${kind}s/models`, { method: 'GET', headers }).catch(() => null);
+
+  // A saved base URL is a free-text field, so any typo would otherwise empty
+  // the model picker. Fall back to the public catalog rather than fail: the
+  // list is read-only, and a wrong base URL still surfaces at generation time.
+  let upstream = await read(baseUrl);
+  if ((!upstream || !upstream.ok) && baseUrl !== OPENROUTER_DEFAULT_BASE_URL) {
+    upstream = await read(OPENROUTER_DEFAULT_BASE_URL);
   }
 
-  if (!upstream.ok) {
-    const text = await upstream.text().catch(() => '');
+  if (!upstream || !upstream.ok) {
+    const text = upstream ? await upstream.text().catch(() => '') : 'unreachable';
     return apiError('UPSTREAM_ERROR', 502, `OpenRouter ${kind} catalog failed: ${text}`);
   }
 

lib/audio/tts-providers.ts

@@ -290,6 +290,13 @@ async function generateOpenAITTS(
       input: text,
       voice: config.voice,
       speed: config.speed || 1.0,
+      // Ask for a container the browser can decode. OpenAI defaults to mp3, but
+      // this same function serves every custom OpenAI-compatible provider and
+      // their defaults differ — OpenRouter's /audio/speech defaults to raw
+      // `pcm`, which arrives headerless, gets labelled mp3 below, and fails in
+      // the client with "no supported source was found". Naming the format
+      // removes the guess. Providers that ignore the field are unaffected.
+      response_format: 'mp3',
     }),
     signal,
   });
@@ -441,6 +448,17 @@ function getAudioResponseFormat(contentType: string): string {
   if (contentType.includes('audio/flac')) return 'flac';
   if (contentType.includes('audio/ogg')) return 'ogg';
   if (contentType.includes('audio/webm')) return 'webm';
+  if (contentType.includes('audio/aac')) return 'aac';
+  if (contentType.includes('audio/opus')) return 'opus';
+  // `pcm`/`l16` is headerless: the client builds `data:audio/<format>` and no
+  // browser decodes bare samples, so say so plainly instead of calling it mp3
+  // and failing later with an opaque "no supported source was found".
+  if (contentType.includes('audio/pcm') || contentType.includes('audio/l16')) {
+    throw new Error(
+      'TTS provider returned raw PCM, which browsers cannot play. Configure the ' +
+        'provider to return mp3, wav, or ogg.',
+    );
+  }
   return 'mp3';
 }
 

tests/providers/provider-neutrality-guard.test.ts

@@ -178,7 +178,7 @@ const TEMPORARY_VENDOR_DEBT: readonly AllowedVendorDebt[] = [
       ['glm', 4],
       ['siliconflow', 2],
       ['doubao', 6],
-      ['openrouter', 2],
+      ['openrouter', 6],
       ['grok', 6],
       ['tencent', 4],
       ['hunyuan', 3],