fix: remove Transfer-Encoding chunked (illegal in HTTP/2) from SSE response headers

src/api/routes/rag.py

@@ -86,13 +86,11 @@ async def chat_with_rag_stream(
 
         user_id = current_user.id if current_user else None
 
-        # SSE headers: X-Accel-Buffering: no is critical for HF Spaces nginx
-        # to disable proxy buffering which causes ERR_HTTP2_PROTOCOL_ERROR
+        # X-Accel-Buffering: no tells HF nginx NOT to buffer — fixes ERR_HTTP2_PROTOCOL_ERROR
+        # NOTE: Do NOT set Transfer-Encoding: chunked — it is prohibited in HTTP/2 (RFC 7540 §8.1.2.2)
         headers = {
             "X-Accel-Buffering": "no",
             "Cache-Control": "no-cache, no-transform",
-            "Connection": "keep-alive",
-            "Transfer-Encoding": "chunked",
         }
 
         return StreamingResponse(