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debug-render

Diagnose wrong ComfyUI renders by probing intermediate stages with run-to-node partial execution.

715|111|Updated Feb 15, 2026
Search Tags:#image generation#preview#Debugging#Workflow#render#ComfyUI#partial execution
One-click install
npx skills add https://github.com/artokun/comfyui-mcp --skill debug-render
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: debug-render
Source: https://github.com/artokun/comfyui-mcp/tree/main/plugin/skills/debug-render
Command: npx skills add https://github.com/artokun/comfyui-mcp --skill debug-render

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

A ComfyUI render that completes but looks wrong (artifacts, wrong pose, ignored ControlNet, degraded upscale) is hard to fix by re-running the whole graph blindly. This Skill localizes the first bad stage by rendering only up to a chosen output node and inspecting what each stage actually produces.

Core Features & Use Cases

  • Partial execution probing: Uses panel_run with to_node_id so only the target output node and its upstream branch render, making each probe fast and cheap.
  • Preview taps for non-output points: Adds temporary PreviewImage, VAEDecode, or MaskToImage taps to inspect latents, masks, preprocessor maps, and intermediate images.
  • Bisection workflow with symptom guide: Maps symptoms (ControlNet ignored, inpaint bleeding, refiner degradation, bad quality) to the right first probe point, then bisects until the faulty node is found.
  • Use Case: A txt2img plus upscale pipeline produces a blurry final image. Preview the base latent before the refiner, confirm it is good, then fix the refiner stage's sampler settings and confirm with another run-to-node before the full render.

Quick Start

Ask the agent to debug why the final image looks wrong by running the graph only up to a preview tap on the suspected stage and inspecting the delivered output.

Frequently Asked Questions about debug-render

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I debug a ComfyUI render that looks wrong but does not error?▼

Use run-to-node partial execution: call panel_run with to_node_id set to an output node so only that branch renders. Inspect the delivered image, then bisect upstream or downstream until you find the first stage whose output is bad, and fix that node.

How do I preview an intermediate latent or mask in ComfyUI?▼

Add a temporary preview tap: route a latent through VAEDecode into PreviewImage, or a mask through MaskToImage into PreviewImage, then run to that tap. Remove the tap with panel_remove_node after inspecting the delivered preview.

Why is my ControlNet or IPAdapter not taking effect in ComfyUI?▼

Preview the preprocessor map (depth, pose, canny) feeding the ControlNet, or the resized reference image feeding the IPAdapter. A blank or wrong map means the preprocessor or its input is at fault, not the sampler.

Can I run a ComfyUI graph only up to a KSampler node?▼

No. ComfyUI partial execution only targets output nodes such as SaveImage, PreviewImage, SaveVideo, or SaveAudio. To inspect a non-output point like a KSampler, add a VAEDecode plus PreviewImage tap downstream of it and run to that.

When should I use troubleshooting instead of render debugging?▼

Use troubleshooting when the run fails outright: red errors, out-of-memory, missing nodes, or a black image from a crash. Render debugging with run-to-node is for outputs that complete successfully but look wrong.

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