# Debug Render

Debug a WRONG or imperfect render (not a hard error) by inspecting inputs and...

- Repository: https://github.com/artokun/comfyui-mcp (883 stars)
- Category: Testing
- License: MIT
- Last updated: 2026-10-26
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add artokun/comfyui-mcp --skill debug-render -g -a claude-code -y`
Codex: `npx skills add artokun/comfyui-mcp --skill debug-render -g -a codex -y`
Cursor: `npx skills add artokun/comfyui-mcp --skill debug-render -g -a cursor -y`
Gemini CLI: `npx skills add artokun/comfyui-mcp --skill debug-render -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add artokun/comfyui-mcp`

## Description

Debug a WRONG or imperfect render (not a hard error) by inspecting inputs and intermediate steps with run-to-node. Render one branch up to an output, preview-tap latents/masks/preprocessor maps, localize the first bad stage, then fix. Use when a final image/video completes but looks wrong, such as artifacts, wrong subject/pose/composition/color, blur, a ControlNet/IPAdapter/mask/LoRA not taking, or a two-stage refiner or upscale degrading the result. For errors/OOM/missing nodes use the troubleshooting skill.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Debugging renders with run-to-node

When a final asset looks wrong (not when it errors), don't re-roll the whole
graph and hope. Localize the fault. Render only as far as one stage and look
at what that stage actually produces. The wrong-looking output is downstream of a
*first* bad step. Find that step, fix it there, and everything after it follows.

The tool for this is `panel_run` with `to_node_id` ("run to node"), which uses
ComfyUI's native partial execution. Only the target output node plus
everything upstream of it renders; every other branch is skipped. That makes each
probe fast and cheap, and the output is delivered to you automatically, same
as any run. Don't poll.

## When to reach for this

- A final image/video is wrong: artifacts, wrong subject/pose/composition, off
  color, soft/blurry, melted hands, wrong style.
- A conditioner isn't "taking" (ControlNet, IPAdapter, a mask, an inpaint, a
  LoRA) and you can't tell if the *input* to it is wrong or the *node* is wrong.
- A multi-stage pipeline (base → refiner, txt2img → upscale, decode → post)
  degrades, and you need to see which stage introduces the problem.
- You only want to test one branch of a multi-output graph without paying for
  the others.

If instead the run fails (red error, OOM, missing node, black image from a
crash), use the troubleshooting skill. This skill is for outputs that
*complete* but look wrong.

## The one hard rule: `to_node_id` must be an OUTPUT node

ComfyUI can only run *to* an output node: SaveImage, PreviewImage, SaveVideo,
SaveAudio, etc. (these show `is_output: true` in `panel_query_graph` detail rows). A bare
KSampler / VAEDecode / preprocessor is not an output node, so you can't target
it directly. To inspect a point that isn't already an output, add a preview
tap there:

The rest: https://github.com/artokun/comfyui-mcp/blob/HEAD/plugin/skills/debug-render/SKILL.md