sgl-project/sglang · error · HTTPException

{detail}

Error message

{detail}

What it means

Generic HTTP 400 wrapper: create_action_generation catches any ValueError from request parsing or generation-prep (response_format, extra_params, cosmos3 observation/prompt validation, sampling params) and re-raises it as HTTPException(400, detail=str(exc)). The detail text identifies the underlying validation failure.

Source

Thrown at python/sglang/multimodal_gen/runtime/entrypoints/action/api.py:228

                payload = await _multipart_action_payload(request, uploads_dir)
            elif "msgpack" in content_type:
                payload = unpack_msgpack(await request.body())
            else:
                payload = await request.json()
            wants_msgpack = _wants_msgpack(request)
            if wants_msgpack:
                _prefer_numpy_output(payload)
            output = await infer_action(payload, server_args)
            if _response_format(payload) == "raw":
                response = action_raw_response(output, preserve_numpy=wants_msgpack)
            else:
                response = action_generation_response(
                    output,
                    server_args,
                    preserve_numpy=wants_msgpack,
                )
    except ValueError as exc:
        raise HTTPException(status_code=400, detail=str(exc)) from exc
    if wants_msgpack:
        return Response(
            content=pack_msgpack(response), media_type="application/msgpack"
        )
    return orjson_response(response)


@router.get("/metadata")
async def action_metadata_endpoint(request: Request):
    return orjson_response(action_metadata(request.app.state.server_args))


@router.websocket("/realtime")
async def action_realtime_ws(websocket: WebSocket):
    server_args: ServerArgs = websocket.app.state.server_args
    await run_action_msgpack_ws(
        websocket,
        server_args,

View on GitHub (pinned to 0132848349)

Solutions

1. Read the detail field in the 400 response; it re-states the specific ValueError message (e.g. image dtype, JSON parse)
2. Fix the flagged field per that specific message
3. Re-send with a minimal known-good payload first, then add fields back to isolate the offending one

try:
    resp = requests.post(ACTION_URL, json=payload, timeout=30)
    resp.raise_for_status()
except requests.HTTPError:
    detail = resp.json().get("detail", "")
    logger.warning("action request rejected: %s", detail)
    # detail names the exact offending field; fix and retry once

When it happens

Trigger: Any malformed action-generation request: bad runtime.response_format, invalid extra_params JSON, wrong image dtype/shape, bad prompt type, or invalid sampling parameters.

Common situations: Client-side payload construction bugs; integration testing against the action endpoint with improperly formatted observations or params.

Related errors

• runtime.response_format must be 'envelope' or 'raw'
• {field_name} is not valid JSON
• {field_name} must be a JSON object
• Invalid request body: {e}
• cache_dit_params must be a dict, got {type(raw).__name__}.

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/0f9eedcbdc191ff1. Report an issue: GitHub.