Node cannot connect

[YuLionel]

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The two nodes that could have been connected, such as the code and judgment branches, cannot be reconnected after manual disconnection and reconnection. After clicking on the connection, there is a delay of about 1 second, and then the connection is disconnected again. In two flows, one is good, while the other experiences such a situation

[dosubot[bot]]

Hi @YuLionel! I'm Dosu and I’m helping the dify team.

This behavior is usually caused by backend validation or state sync rejecting the new connection after an initial optimistic update. When you reconnect nodes, the frontend first adds the edge, but within about a second, the workflow state is synced to the backend, which may apply stricter validation. If the backend rejects the connection (for example, due to graph integrity rules, node type constraints, or parallel branch limitations), the frontend refreshes its state and removes the edge—resulting in the delayed disconnect you see.

This can happen intermittently if the flows have different structures or node types. For example, Dify currently does not allow a node to have multiple incoming connections from different branches or parallel paths, and certain node types (like code and conditional branches) have strict connection rules. If the flow where reconnection fails involves such a scenario, the backend will always reject the connection attempt after sync, even if it appears to work briefly on the frontend. See related discussion and technical details here and here.

Recent changes to workflow draft syncing (like PR #27487) have improved state consistency, but the underlying validation logic remains the same.

To troubleshoot: compare the structure of the working and non-working flows, especially the number of incoming/outgoing connections for each node and the types of nodes involved. Also, check your browser console and backend logs for validation errors when the disconnect happens—these often provide clues about which rule is being violated.

If you need to support more complex branching, you may need to adjust your workflow design to avoid multiple incoming connections to a single node or review the node types and their allowed transitions.

To reply, just mention @dosu.

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