Flux2 Klein cannot merge models with LoRA in ComfyUI.

[iamddtla0620]

Custom Node Testing

• I have tried disabling custom nodes and the issue persists (see how to disable custom nodes if you need help)

Expected Behavior

After a version update in March, ComfyUI is unable to detect any Flux2 Klein models (either 4B or 9B) when attempting to merge the model with a LoRA.

I have already ensured that ComfyUI is updated to the latest version, but the error always shows: “Unable to load logs, please ensure you have updated your ComfyUI backend.”

I have also disabled all custom nodes and all third-party extensions.

Actual Behavior

As shown in the workflow in the image, I am merging a model with a LoRA. Before March 2026, I was able to perform model merging normally. However, after an update in March, whenever I try to merge models, it always shows: “Unable to load logs, please ensure you have updated your ComfyUI backend.”

I do not encounter this error when merging other models, such as Zimage or Anima.

Steps to Reproduce

You can download any “Flux2 Klein base 9B” LoRA and attempt to merge it with the model, and you will find that the merge cannot be completed.

flux2_klein_9b_base_fp8_bug.json

Debug Logs

Unable to load logs, please ensure you have updated your ComfyUI backend.

I have updated ComfyUI to the latest version and tested it without installing any custom nodes or extensions.

Other

No response