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ComfyUI custom node import failed

Find the first import exception in the Python environment ComfyUI actually uses.

Reviewed 7 October 2026 · Evidence-led troubleshooting

Recognize the message

IMPORT FAILED; ModuleNotFoundError; ImportError

The startup log reports that an extension could not register. The short IMPORT FAILED line is a summary; the preceding exception contains the useful evidence.

Work through the evidence

  1. Copy the first complete traceback for the affected extension. Include the missing module or symbol and how you start ComfyUI: Desktop, portable or a managed Python environment.
  2. Read the extension’s official installation requirements. Check which interpreter the running application uses before making any environment change.
  3. Isolate the extension in a controlled copy or documented troubleshooting mode. Compare a minimal core workflow with the affected workflow; record whether startup now completes.

Verify the result

Startup no longer reports that extension’s import failure and its documented classes are registered. Then test the smallest workflow using the extension.

What this does not prove

A module installed into system Python might remain unavailable to embedded Python. Blind upgrades can introduce new incompatibilities; preserve a working environment and follow version-specific instructions.

Inspect before changing your workflow

The log inspector works in your browser. The workflow checker reads exported graph structure. Neither sends files automatically or executes nodes. Preserve the original, inspect a copy and record the actual test result in Casebook.

Inspect your log ↗ · Check the graph ↗ · Record a recovery case ↗

Before asking for help

Include the first full exception, the failing stage, software versions, model family and the smallest reproducible graph. Redact API keys, user paths and private prompts. A summary such as “KSampler broken” removes the context that distinguishes one failure from another.

Prepare a redacted copy ↗

Related investigations

ComfyUI CUDA out of memory · ComfyUI missing custom nodes · ComfyUI model not found · ComfyUI tensor shape mismatch

Source and scope

These are OnBeg’s diagnostic checklists, informed by official ComfyUI troubleshooting. They are not universal fixes and do not replace model- or extension-specific instructions.