fix: normalize CosyVoice3 instructions

deploy/selfmedia-voice/api.py

@@ -89,6 +89,17 @@ async def lifespan(_: FastAPI):
 
 app = FastAPI(title="SelfMedia Voice", version="1", lifespan=lifespan)
 
+INSTRUCTION_END_TOKEN = "<|endofprompt|>"
+
+
+def normalize_instruction(value: str | None) -> str | None:
+    if value is None or not value.strip():
+        return None
+    normalized = value.strip()
+    if INSTRUCTION_END_TOKEN in normalized:
+        return normalized
+    return f"You are a helpful assistant. {normalized}{INSTRUCTION_END_TOKEN}"
+
 
 @app.get("/health")
 def health() -> dict:
@@ -125,7 +136,7 @@ def speech(request: SpeechRequest) -> Response:
         raise HTTPException(status_code=400, detail="voice must select the configured reference voice")
 
     started = time.perf_counter()
-    instruction = request.instructions or request.instruct
+    instruction = normalize_instruction(request.instructions or request.instruct)
     with runtime.lock:
         inference = (
             runtime.model.inference_instruct2(