Chatflow hangs on non-existing conversation id

[wylswz]

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Dify version

latest

Cloud or Self Hosted

Cloud

Steps to reproduce

1. Enter a chatflow and start a conversation.
2. Copy cURL of chat-messages api.
3. Modify the conversation id to a non-existing one.
4. Send request.

✔️ Expected Behavior

Request should fail with a 4xx status code.

❌ Actual Behavior

The request hangs with only ping events received..

[dosubot]

This is a known regression introduced in v1.13.0 and is tracked in issue #33210. It has been reported across every release from v1.13.0 through v1.14.2 [1].

Root cause: v1.13.0 moved Advanced Chat/Workflow execution to Celery async workers. When a non-existent conversation_id is passed, the API returns HTTP 200 and opens an SSE stream before the conversation is validated. The ConversationNotExistsError is then raised inside the Celery worker but never propagated back to the SSE client — so the connection hangs indefinitely with only ping events.

Fix status: PR #33274 by @fatelei targets this issue (explicitly references #33210) but remains unmerged as of now, which is why the bug persists on Dify Cloud and all self-hosted versions from v1.13.0 onward.

Workaround: Validate the conversation_id before calling the API, or pass an empty/null conversation_id to start a new conversation instead.

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