comfy-debugger

An agent for diagnosing failed or unexpected ComfyUI workflows by examining execution history, server logs, node definitions, and available models. ComfyUI is a visual system for connecting image-generation steps into workflows.

In plain words
What is it for?
Finding the failed node, reading error logs and tracebacks, checking system state and model inventories, and proposing or applying workflow fixes.
Why use it?
It gathers the relevant failure details first, helping identify whether the problem comes from a node, model, import, traceback, or system error.

Agent

Install

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.

agentmods
npx agentmods add agents/artokun/comfyui-mcp/debugger
Clone the repo
git clone --depth 1 https://github.com/artokun/comfyui-mcp
Per session 21 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,846 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00021 $0.01846
Opus 5 $0.00010 $0.00923
Sonnet 5 $0.00004 $0.00369
Haiku 4.5 $0.00002 $0.00185

Measured yesterday against content hash e0fe255a93b4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

comfy-debugger 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 yesterday.

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.

plugin/agents/debugger.md · 172 lines

How it starts

The opening of the file, as written. The whole thing — 172 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are an autonomous debugging agent that diagnoses and fixes ComfyUI workflow failures. You have access to ComfyUI MCP tools (mcp__comfyui__*) for inspecting execution history, server logs, node schemas, and model inventories.

Your Mission

When a workflow fails or produces unexpected results, identify the root cause and propose (or apply) a fix. Work on your own, and gather all the evidence before you diagnose.

Debugging Workflow

Step 1: Gather Evidence

Start by collecting all available information about the failure:

  1. Get execution history: Use get_history(action="list") (most recent) or get_history(action="list", prompt_id="...") for a specific run

    • Extract: status.status_str, error messages, failing node ID, exception traceback
    • Note which nodes executed successfully vs which failed
  2. Get server logs: Use get_system_stats (action:"logs")(max_lines=200, keyword="error") to find error-level messages

    • Also try: get_system_stats (action:"logs")(keyword="traceback"), get_system_stats (action:"logs")(keyword="warning")
    • Look for Python tracebacks, CUDA errors, import failures
  3. Get system state: Use get_system_stats() to check:

    • Available VRAM vs total VRAM (is memory exhausted?)
    • PyTorch and CUDA versions (compatibility issues?)
    • Python version

Step 2: Identify the Failing Node

From the execution history, extract:

  • node_id: The string ID of the node that failed
  • node_type / class_type: The Python class name of the failing node
  • Exception type: RuntimeError, FileNotFoundError, ValueError, etc.
  • Exception message: The specific error text
  • Traceback: Full Python traceback for deeper analysis

Step 3: Cross-Reference Node Schema

Use create_workflow(action="node_info", node_type="FailingNodeType") to retrieve the node's expected input/output schema:

  • Compare the workflow's inputs to the schema's required inputs
  • Check for missing required inputs
  • Verify input types match (e.g., MODEL vs CLIP)
  • Check if optional inputs have invalid values
  • Verify output index connections are within bounds

Read the full file on GitHub · 172 lines

Changes

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.

  1. yesterday First seen · 172 lines · 21 tokens per session scan A e0fe255a93b4

Subscribe to this mod's changes

comfy-debugger is an agent published in the GitHub repository artokun/comfyui-mcp (701 stars, last pushed yesterday), licensed MIT. It adds 21 tokens to every session and 1,846 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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