fix: propagate ElevenLabs voice fetch errors to frontend

- elevenlabs_voices.py: re-raise exception on first fetch failure
  (empty cache) instead of silently returning empty list
- routes_tts.py: catch get_voices() exception and return available=False
  with the error detail; add optional error field to ProviderVoicesResponse
- VoiceSelector: show actual API error message when available=false

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/api/v1/routes_tts.py

@@ -49,6 +49,7 @@ class ProviderVoicesResponse(BaseModel):
     voices: list[VoiceInfo]
     default: str
     available: bool = True
+    error: Optional[str] = None
 
 
 class LanguagesResponse(BaseModel):
@@ -107,7 +108,17 @@ async def list_voices(
                 default="",
                 available=False,
             )
-        el_voices = await elevenlabs_voice_service.get_voices()
+        try:
+            el_voices = await elevenlabs_voice_service.get_voices()
+        except Exception as e:
+            logger.warning(f"ElevenLabs get_voices failed: {e}")
+            return ProviderVoicesResponse(
+                provider="elevenlabs",
+                voices=[],
+                default="",
+                available=False,
+                error=str(e),
+            )
         voices = [
             VoiceInfo(
                 id=v.voice_id,

backend/app/services/elevenlabs_voices.py

@@ -56,8 +56,10 @@ class ElevenLabsVoiceService:
             logger.info(f"Fetched {len(voices)} voices from ElevenLabs API")
             return voices
         except Exception as e:
-            logger.warning(f"Failed to fetch ElevenLabs voices, using stale cache: {e}")
-            return self._cache  # Stale cache fallback
+            if self._cache:
+                logger.warning(f"Failed to fetch ElevenLabs voices, using stale cache: {e}")
+                return self._cache
+            raise
 
     async def _fetch_voices(self) -> list[ElevenLabsVoice]:
         """Fetch voices from the ElevenLabs API."""

frontend/src/components/VoiceSelector.tsx

@@ -39,7 +39,7 @@ export function VoiceSelector({
 
         // Set default voice from API response if switching providers
         if (voicesData.available === false) {
-          setError(`ElevenLabs TTS is not configured on the server. Contact your administrator to set up the ELEVENLABS_API_KEY.`);
+          setError(voicesData.error || 'ElevenLabs TTS is not configured on the server. Contact your administrator to set up the ELEVENLABS_API_KEY.');
         } else if (voicesData.default && voicesData.voices.length > 0) {
           // Only reset default voice if the current one isn't in the new voice list
           const currentVoiceExists = voicesData.voices.some(v => v.id === preferences.default_voice);

frontend/src/types/api.ts

@@ -86,6 +86,7 @@ export interface ProviderVoicesResponse {
   voices: VoiceInfo[];
   default: string;
   available?: boolean;
+  error?: string;
 }
 
 /** @deprecated Use ProviderVoicesResponse instead */