# How do I set ComfyUI logging levels and write a log file with --verbose and --log-stdout?

- id: art_01M5P4EPC2J13H6V8VXN5VZY8V
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T08 · tags: none
- updated: 2026-10-24T04:59:37.723Z
- url: https://veyrul.com/articles/art_01M5P4EPC2J13H6V8VXN5VZY8V

Problem: capturing diagnostics from headless ComfyUI. Conditions: fb3befd. Method: --verbose accepts no value (console DEBUG), a LEVEL (console level) or LEVEL FILE (adds a file output), and may repeat. Levels: DEBUG, DETAIL, INFO, WARNING, ERROR, CRITICAL (DETAIL is a ComfyUI-specific level). Console level defaults to INFO; with several console entries the lowest wins. Each LEVEL FILE adds a logging.FileHandler with an absolute path, UTF-8; if the file cannot be opened a warning is logged and that output skipped. Example: --verbose INFO --verbose DETAIL comfyui_detail.log (inference from parser). --log-stdout sends sub-ERROR messages to stdout and keeps ERROR and above on stderr. Failure modes: LEVEL not in the list makes argparse error out; the setup_logger default of a comfyui_detail.log file only applies when file_outputs is None, whereas main.py passes a list (possibly empty), so by reading, no file is written unless asked. Limitations: no rotation handler is used. Version: fb3...

Problem: capturing diagnostics from headless ComfyUI. Conditions: fb3befd. Method: --verbose accepts no value (console DEBUG), a LEVEL (console level) or LEVEL FILE (adds a file output), and may repeat. Levels: DEBUG, DETAIL, INFO, WARNING, ERROR, CRITICAL (DETAIL is a ComfyUI-specific level). Console level defaults to INFO; with several console entries the lowest wins. Each LEVEL FILE adds a logging.FileHandler with an absolute path, UTF-8; if the file cannot be opened a warning is logged and that output skipped. Example: --verbose INFO --verbose DETAIL comfyui_detail.log (inference from parser). --log-stdout sends sub-ERROR messages to stdout and keeps ERROR and above on stderr. Failure modes: LEVEL not in the list makes argparse error out; the setup_logger default of a comfyui_detail.log file only applies when file_outputs is None, whereas main.py passes a list (possibly empty), so by reading, no file is written unless asked. Limitations: no rotation handler is used. Version: fb3befd.

Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources.

Limitations: Reading of code only; behaviour of main.py's empty-list case was inferred and not run.

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://raw.githubusercontent.com/comfyanonymous/ComfyUI/fb3befd168731438f88bc96e0920a538e8649878/comfy/cli_args.py",
      "note": "VerboseAction; --verbose argument; VerboseAction.__call__; --log-stdout argument; setup_logger; setup_logger; researcher reasoning"
    },
    {
      "url": "https://raw.githubusercontent.com/comfyanonymous/ComfyUI/fb3befd168731438f88bc96e0920a538e8649878/app/logger.py",
      "note": "VerboseAction; --verbose argument; VerboseAction.__call__; --log-stdout argument; setup_logger; setup_logger; researcher reasoning"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] Problem: capturing diagnostics from headless ComfyUI. Conditions: fb3befd. Method: --verbose accepts no value (console DEBUG), a LEVEL (console level) or LEVEL FILE (adds a file output), and may repeat. Levels: DEBUG, DETAIL, INFO, WARNING, ERROR, CRITICAL (DETAIL is a ComfyUI-specific level). Console level defaults to INFO; with several console entries the lowest wins. Each LEVEL FILE adds a logging.FileHandler with an absolute path, UTF-8; if the file cannot be opened a warning is logged and that output skipped. Example: --verbose INFO --verbose DETAIL comfyui_detail.log (inference from parser). --log-stdout sends sub-ERROR messages to stdout and keeps ERROR and above on stderr. Failure modes: LEVEL not in the list makes argparse error out; the setup_logger default of a comfyui_detail.log file only applies when file_outputs is None, whereas main.py passes a list (possibly empty), so by reading, no file is written unless asked. Limitations: no rotation handler is used. Version: fb3befd. · locator: VerboseAction; --verbose argument; VerboseAction.__call__; --log-stdout argument; setup_logger; setup_logger; researcher reasoning · source: https://raw.githubusercontent.com/comfyanonymous/ComfyUI/fb3befd168731438f88bc96e0920a538e8649878/comfy/cli_args.py

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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