Alt + Drag a subgraph is corrupting the original subgraph

[Steudio]

Prerequisites

• I am running the latest version of ComfyUI
• I have searched existing issues to make sure this isn't a duplicate
• I have tested with all custom nodes disabled (see how)

What happened?

Alt + Drag a subgraph is corrupting the original subgraph (or maybe both?)

Steps to Reproduce

1. Select a subgraph.
2. Alt + drag the subgraph to create an independent copy.
3. Edit the new subgraph (e.g., delete some nodes that have input links).
4. Check the original subgraph, the nodes are still present (as expected), but their links are gone (not expected).

How is this affecting you?

Feature doesn't work as expected

ComfyUI Frontend Version

1.28.0

Browser

Firefox

Console Errors

Logs

Additional Context

No response

┆Issue is synchronized with this Notion page by Unito

[dosubot]

This is a known issue in ComfyUI Frontend, including version 1.28.0: Alt + Drag to duplicate a subgraph can corrupt the original subgraph’s links, especially after editing the copy. The root cause is how the frontend handles serialization and reference management during duplication—links may be lost or incorrectly mapped, and this often happens silently without console errors or logs. Multiple related reports confirm this behavior across versions and browsers (#5466, #5669, #4854).

Recent updates have improved the robustness of subgraph handling, including a refactor of serialization/deserialization logic for copying and pasting subgraphs (PR #5139), but manual intervention is still required if corruption occurs. The most reliable workaround is to manually rebuild the affected subgraph: remove all slots and connections, re-add them, and re-export the workflow. Editing the workflow JSON to remove broken link references may also help.

Subgraph features are still under active development, and there are no automated repair tools or UI warnings for this issue yet. If you keep seeing this problem, keeping your frontend updated and rebuilding subgraphs as needed is the best approach for now.

To reply, just mention @dosu.

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