Fix IndexError: skip empty-choices chunks from HF Router streaming

backend/api/demo.py

@@ -211,6 +211,8 @@ async def execute_query_stream(req: ExecuteQueryRequest):
                     temperature=0.1,
                 )
                 async for chunk in stream:
+                    if not chunk.choices:
+                        continue  # HF Router sends empty-choices chunks (ping/final)
                     delta = chunk.choices[0].delta.content
                     if delta:
                         chunks.append(delta)
@@ -280,6 +282,8 @@ async def execute_query_stream(req: ExecuteQueryRequest):
                         temperature=0.3,
                     )
                     async for chunk in diag_stream:
+                        if not chunk.choices:
+                            continue
                         delta = chunk.choices[0].delta.content
                         if delta:
                             yield {"data": json.dumps({"type": "diagnosis_chunk", "chunk": delta})}

backend/env/sql_env.py

@@ -113,6 +113,8 @@ async def _call_llm(
                 temperature=0.1,
             )
             async for chunk in resp:
+                if not chunk.choices:
+                    continue
                 delta = chunk.choices[0].delta.content
                 if delta:
                     yield delta