ComfyUI V1 → V3 Migration Guide

Migrate existing V1 nodes to the modern V3 API. V3 uses classmethods, typed inputs/outputs, and ComfyExtension registration.

Migration Checklist

1. Change base class to io.ComfyNode
2. Replace INPUT_TYPES() with define_schema() returning io.Schema
3. Rename execution function to execute and make it a @classmethod
4. Replace return tuples with io.NodeOutput(...)
5. Replace IS_CHANGED with fingerprint_inputs
6. Replace VALIDATE_INPUTS with validate_inputs
7. Convert check_lazy_status to @classmethod
8. Replace NODE_CLASS_MAPPINGS with ComfyExtension + comfy_entrypoint()
9. Access hidden inputs via cls.hidden instead of kwargs
10. Remove __init__ methods (no instance state in V3)

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