Cannot execute because a node is missing the class_type property.: Node ID '#427'

[YihongT]

I noticed that many users have encountered this error, so I decided to open this issue to document my solution.

In my case, this issue is inherently related to a custom node (i.e., ComfyUI-KJNodes). After switching to the nightly version, the problem was resolved.

I hope this is helpful.

[kaganEArs]

nightly -> [1.0.1] -> nightly changed like this and restarted and it was fixed

[ltdrdata]

It seems that 1.0.1 is an outdated version than nightly version.

[euzkadie]

I have the same error but ID #11

[christian-byrne]

This issue has been addressed with improved error messaging in frontend v1.39.5 (backend: #12177, frontend: Comfy-Org/ComfyUI_frontend#8511).

The cryptic "Cannot execute because a node is missing the class_type property" error now shows:

• The actual node type (e.g., KSampler, LoadImage) that is missing
• The node's custom title if you renamed it in the workflow
• A hint to install missing custom nodes via ComfyUI Manager

To get the fix: Update frontend to v1.39.5+ or use --front-end-version Comfy-Org/ComfyUI_frontend@1.39.5. ComfyUI Desktop users will receive this in the next stable release (~mid-February 2026).

If the node source shows "Unknown": This happens when the Manager is not installed or the node is not in the registry. You can enable the built-in Manager with --enable-manager, use the legacy Manager UI with --enable-manager --enable-manager-legacy-ui, or install ComfyUI-Manager as a custom node. The node ID in the error message can still help you locate it in the workflow.

Feel free to reopen this issue if the problem persists after updating. Please include your ComfyUI version, frontend version (visible in bottom-right corner), and a screenshot of the error dialog.

For general guidance see https://docs.comfy.org, or contact support@comfy.org for additional help.