UTFCN — Use The F***ing Core Nodes

A ComfyUI companion that nudges your workflows back toward core nodes. Over time a graph accumulates custom nodes that just re-implement things ComfyUI now ships itself. UTFCN spots those and helps you swap them out — fewer dependencies, more portable workflows.

It does three things:

1. On add — drop a custom node that has a core (or otherwise installed) equivalent and, depending on the mode, UTFCN either shows a quiet tip or (in Force mode) auto-replaces it with the equivalent on the spot.
2. Replace across a workflow — Extensions ▸ UTFCN ▸ Replace custom nodes with core / available… (also in the command palette). It scans the open graph and shows a preview of every swap before anything changes.
3. Replace one node — right-click any custom node ▸ Replace with core / available.

Nothing is ever swapped without your say-so, and the engine only rewires slots it can move losslessly — anything it can't map is reported, not guessed.

Works on uninstalled ("missing") nodes

The headline case: open a downloaded workflow full of red missing nodes and replace them with core equivalents without installing the packs at all. ComfyUI keeps each missing node as a placeholder that remembers its original type and wiring, so UTFCN can still match and swap it — via a curated rule (by name) or by matching the node's serialized signature against your core nodes. Both "Replace…" and the right-click item work on them; the bulk dialog labels them ⚠ not installed. (Widget values aren't carried for a node whose definition you don't have — links are.)

How it decides what's equivalent

The backend reads the live node registry (real INPUT_TYPES / RETURN_TYPES and each node's source module) and ranks candidates in three tiers:

Tier	Meaning	Auto-applied?
curated	a hand-written rule in mappings.json / user_mappings.json	yes (verified)
exact	identical input names+types and output types to a core/other-pack node	yes (verified)
partial	can structurally stand in (accepts all inputs, provides all outputs) but names/slots differ	suggestion only

"Available" means core is preferred, and if there's no core match it will offer an equivalent from a different installed pack as a fallback.

For an uninstalled node only curated (by name) and partial (by its serialized link signature) can apply — the exact tier needs the widget-level signature, which a node you haven't installed can't provide.

Shipped equivalences

mappings.json ships a small, hand-verified set (each checked lossless against the real core signatures):

• GetImageSize+ (essentials) → core GetImageSize
• MaskPreview+ (essentials) → core MaskPreview
• BOOLConstant / INTConstant / FloatConstant (KJNodes) → core PrimitiveBoolean / PrimitiveInt / PrimitiveFloat
• Convert Masks to Images / Mask Invert (WAS) → core MaskToImage / InvertMask

Rules for nodes you don't have installed are simply ignored. Everything else is found live: exact-signature matches auto-apply, looser ones are suggested.

Adding your own equivalences

To bless a partial match as safe, or to fix up slots whose names differ, add a rule to user_mappings.json (merged over the shipped mappings.json, survives updates):

{
  "rules": {
    "SomeCustomNode": [
      {
        "to": "CoreNode",
        "note": "why they're equivalent (shown in the preview)",
        "inputs":  { "old_input": "new_input" },
        "widgets": { "old_widget": "new_widget" },
        "outputs": { "old_output": "new_output" }
      }
    ]
  }
}

List targets in preference order (put the core node first). Any slot you don't list is matched by identical name, then by type + order. After editing, run Extensions ▸ UTFCN ▸ Refresh equivalence index (no restart needed).

Settings

UTFCN ▸ On add ▸ When adding a custom node that has a core / available equivalent:

• Off — do nothing.
• Suggest (default) — show a tip pointing at the equivalent.
• Force (auto-replace with core) — immediately swap it for the equivalent. Force only ever applies verified matches (curated or exact-signature); it never auto-applies a heuristic guess, and it never fires while you're opening or importing a workflow — only on nodes you add. Undo with Ctrl+Z.

Install

Clone into ComfyUI/custom_nodes/ and restart ComfyUI:

git clone https://github.com/ethanfel/ComfyUI-UTFCN

No Python dependencies. The node adds a single read-only server route (/utfcn/scan) and a frontend extension.

License

GPL-3.0-or-later. See LICENSE.