Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add sandyup/comfyui-mcp --skill debug-rendergit clone --depth 1 https://github.com/sandyup/comfyui-mcpWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/sandyup/comfyui-mcp/debug-render)<a href="https://agentmods.dev/skills/sandyup/comfyui-mcp/debug-render"><img src="https://agentmods.dev/badge/skills/sandyup/comfyui-mcp/debug-render/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/sandyup/comfyui-mcp/debug-render"><img src="https://agentmods.dev/badge/skills/sandyup/comfyui-mcp/debug-render.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00122 | $0.01646 |
| Opus 5.5 | $0.00049 | $0.00658 |
| Sonnet 5.5 | $0.00024 | $0.00329 |
| Haiku 4.5 | $0.00012 | $0.00165 |
Grade A, and why
debug-render scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
89% identical to debug-render — 95 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.
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: 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_get_graph). 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:
| You want to see… | Wire type | Tap to add | Wiring |
|---|---|---|---|
| An intermediate image (post-process, refiner stage, composite) | IMAGE | PreviewImage |
image → PreviewImage.images |
| A latent (after a sampler, before/after upscale) | LATENT | VAEDecode → PreviewImage |
latent → VAEDecode.samples; reuse the graph's VAE → VAEDecode.vae; then → PreviewImage |
| A mask (inpaint, segmentation, attention) | MASK | MaskToImage → PreviewImage |
mask → MaskToImage.mask → PreviewImage |
| A ControlNet/preprocessor map (depth/pose/canny) | usually IMAGE already | PreviewImage |
the preprocessor's IMAGE output → PreviewImage.images |
| The actual prompt/conditioning | CONDITIONING | (can't preview as an image) | inspect widget values / the text node feeding it instead |
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 106 lines · 122 tokens per session scan A 3a70b2e78078
debug-render is a skill published in the GitHub repository sandyup/comfyui-mcp (2 stars, last pushed 3mo ago), licensed MIT. It adds 122 tokens to every session and 1,646 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 89% identical to debug-render, differing in 95 lines, and is treated as a copy.
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