# What happens if --front-end-version cannot be fetched, and does --front-end-root get any fallback?

- id: art_01M5P4CGFTG4Y7TYRC4W8VDP5K
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T04, T08 · tags: none
- updated: 2026-10-24T04:58:26.163Z
- url: https://veyrul.com/articles/art_01M5P4CGFTG4Y7TYRC4W8VDP5K

Problem. A pinned frontend fails to download, so what UI do you actually get. Conditions. --front-end-version set to a non-default value and no --front-end-root. Method. FrontendManager.init_frontend wraps init_frontend_unsafe in a broad try/except: on any exception it logs 'Failed to initialize frontend' with the error, logs 'Falling back to the default frontend.' and returns the pip-package frontend path. Server startup does not abort. --front-end-root is different: argparse validates the directory at launch (exists, is a directory, readable) and refuses to start otherwise; when valid, server.py uses it directly and never calls init_frontend, so there is no version check or fallback to the pip package. Failure modes. A typo or offline machine yields the packaged frontend silently apart from a log line, so a pin is not a guarantee; check the log line 'web root'. An empty or wrong directory under --front-end-root gives a broken UI with no fallback (inference). Limitations. Interacti...

Problem. A pinned frontend fails to download, so what UI do you actually get. Conditions. --front-end-version set to a non-default value and no --front-end-root. Method. FrontendManager.init_frontend wraps init_frontend_unsafe in a broad try/except: on any exception it logs 'Failed to initialize frontend' with the error, logs 'Falling back to the default frontend.' and returns the pip-package frontend path. Server startup does not abort. --front-end-root is different: argparse validates the directory at launch (exists, is a directory, readable) and refuses to start otherwise; when valid, server.py uses it directly and never calls init_frontend, so there is no version check or fallback to the pip package. Failure modes. A typo or offline machine yields the packaged frontend silently apart from a log line, so a pin is not a guarantee; check the log line 'web root'. An empty or wrong directory under --front-end-root gives a broken UI with no fallback (inference). Limitations. Interaction with --offline was not tested. Version and date. commit fb3befd, read 2026-10-24.

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

Limitations: Static code reading, not executed. Other routes (e.g. static file handlers) in later server code were not read, so claims about a broken UI for a wrong root are inference.

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/app/frontend_management.py",
      "note": "init_frontend; cli_args.py --front-end-root; is_valid_directory; PromptServer.__init__; researcher reasoning"
    },
    {
      "url": "https://raw.githubusercontent.com/comfyanonymous/ComfyUI/fb3befd168731438f88bc96e0920a538e8649878/comfy/cli_args.py",
      "note": "init_frontend; cli_args.py --front-end-root; is_valid_directory; PromptServer.__init__; researcher reasoning"
    },
    {
      "url": "https://raw.githubusercontent.com/comfyanonymous/ComfyUI/fb3befd168731438f88bc96e0920a538e8649878/server.py",
      "note": "init_frontend; cli_args.py --front-end-root; is_valid_directory; PromptServer.__init__; researcher reasoning"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] Problem. A pinned frontend fails to download, so what UI do you actually get. Conditions. --front-end-version set to a non-default value and no --front-end-root. Method. FrontendManager.init_frontend wraps init_frontend_unsafe in a broad try/except: on any exception it logs 'Failed to initialize frontend' with the error, logs 'Falling back to the default frontend.' and returns the pip-package frontend path. Server startup does not abort. --front-end-root is different: argparse validates the directory at launch (exists, is a directory, readable) and refuses to start otherwise; when valid, server.py uses it directly and never calls init_frontend, so there is no version check or fallback to the pip package. Failure modes. A typo or offline machine yields the packaged frontend silently apart from a log line, so a pin is not a guarantee; check the log line 'web root'. An empty or wrong directory under --front-end-root gives a broken UI with no fallback (inference). Limitations. Interaction with --offline was not tested. Version and date. commit fb3befd, read 2026-10-24. · locator: init_frontend; cli_args.py --front-end-root; is_valid_directory; PromptServer.__init__; researcher reasoning · source: https://raw.githubusercontent.com/comfyanonymous/ComfyUI/fb3befd168731438f88bc96e0920a538e8649878/app/frontend_management.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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