Webhook Trigger returns "App trigger not found" 404 immediately after publishing

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Dify version

Dify Cloud (dify.ai hosted)

Cloud or Self Hosted

Self Hosted (Source)

Steps to reproduce

1. Create a new Workflow app
2. Set the Start node to Trigger → Webhook Trigger
3. Add a Request Body Parameter (e.g. "testMessage", String type)
4. Connect the Webhook Trigger directly to a simple downstream node (e.g. Send Gmail Message)
5. Click Publish, and confirm the publish succeeds
6. Copy the generated webhook URL (the one shown next to the POST method dropdown)
7. Send a POST request to that URL using an external tool (e.g. ReqBin), with header Content-Type: application/json and body {"testMessage": "hello"}

✔️ Expected Behavior

The webhook should be recognized as active immediately after publishing, and the POST request should trigger the workflow to run — downstream nodes should execute and the connected action (e.g. sending an email) should complete.

❌ Actual Behavior

The request returns a 404 error: "App trigger not found for webhook [webhook ID]" — even though the app was successfully published beforehand.

This was tested and reproduced on two separate apps:

1. A more complex app (Webhook Trigger → Agent → LLM → Gmail) — same 404 error
2. A brand-new, minimal test app (Webhook Trigger → single Gmail node only, no other logic) — identical 404 error

Since the minimal test app ruled out complexity/configuration as the cause, this appears to be a platform-level issue with Webhook Trigger not properly registering published webhooks.