calesthio/OpenMontage · error · ComfyUIError

No prompt_id in response: {data}

Error message

No prompt_id in response: {data}

What it means

ComfyUIError raised when the /prompt response parsed successfully and contained no node_errors or error, yet lacks a prompt_id field. prompt_id is the only handle the client has for polling history and websockets, so without it the call cannot proceed. It usually indicates the server responded with something unexpected — an HTML error page that happened to parse, a proxy interposing, or an empty JSON object.

Source

Thrown at tools/_comfyui/client.py:196

    def submit(self, workflow: dict) -> str:
        """Queue a workflow for execution.  Returns the ``prompt_id``."""
        resp = requests.post(
            f"{self.server_url}/prompt",
            json={"prompt": workflow, "client_id": self.client_id},
            timeout=30,
        )
        try:
            data = resp.json()
        except ValueError:
            data = {}
        if data.get("node_errors"):
            raise ComfyUIError(f"Node errors: {json.dumps(data['node_errors'])}")
        if data.get("error"):
            raise ComfyUIError(f"Prompt error: {json.dumps(data['error'])}")
        resp.raise_for_status()
        prompt_id = data.get("prompt_id")
        if not prompt_id:
            raise ComfyUIError(f"No prompt_id in response: {data}")
        return prompt_id

    def poll(
        self,
        prompt_id: str,
        *,
        timeout: int = 600,
        interval: int = 5,
    ) -> dict:
        """Block until *prompt_id* finishes.  Returns the history entry."""
        deadline = time.time() + timeout
        while time.time() < deadline:
            entry = self._history_entry(prompt_id)
            if entry is not None:
                return entry
            time.sleep(interval)
        raise ComfyUIError(
            f"Prompt {prompt_id} did not complete within {timeout}s. "

View on GitHub (pinned to 95e1c3d0ab)

Solutions

1. Print the embedded data payload — it shows exactly what the server returned
2. Curl the server directly (GET {server_url}/system_stats) to confirm a real ComfyUI is listening at that URL
3. Remove/verify any proxy in front of ComfyUI or whitelist the client in ComfyUI's security config
4. Restart ComfyUI and wait for its startup log line before submitting

Example fix

# before
client = ComfyUIClient("http://localhost:8188")  # wrong port/service

# after
import requests
assert requests.get("http://localhost:8188/system_stats", timeout=5).ok
client = ComfyUIClient("http://localhost:8188")

import requests
stats = requests.get(f"{server_url}/system_stats", timeout=5)
stats.raise_for_status()  # real ComfyUI responds here
assert "comfyui" in stats.json().get("system", {}).get("comfyui_version", "") or stats.ok

def comfyui_is_alive(server_url: str) -> bool:
    try:
        return requests.get(f"{server_url}/system_stats", timeout=5).ok
    except requests.RequestException:
        return False

try:
    prompt_id = client.submit(workflow)
except ComfyUIError as e:
    if "No prompt_id" in str(e):
        raise SystemExit(f"server at {client.server_url} is not a healthy ComfyUI — check URL/proxy/startup")
    raise

When it happens

Trigger: submit() gets a 200 response whose body is {} or an unexpected shape; a reverse proxy returns a JSON body without prompt_id; ComfyUI is behind auth that returned a JSON-formatted denial; a very old/new ComfyUI build with a changed response contract.

Common situations: Wrong server_url pointing at a non-ComfyUI service; ComfyUI not fully started when the first submit lands; a port conflict serving a different tool; version mismatch between client expectations and server build.

Related errors

• Node errors: {json.dumps(data['node_errors'])}
• Prompt error: {json.dumps(data['error'])}
• Prompt {prompt_id} did not complete within {timeout}s. The j
• Execution error: {msgs}
• Execution error: {data}

AI-assisted analysis of calesthio/OpenMontage@95e1c3d0ab (2026-08-15). Data as JSON: /api/errors/ca3c4c38e5619ee5. Report an issue: GitHub.