I have an image made in A1111/Forge or diffusers with a seed; why does the same seed and prompt in ComfyUI (or the reverse) give a different image, and which differences are known?

Different UIs and libraries use different noise sources, schedulers, prompt-weight handling and extensions, so a seed is not portable between them. The ComfyUI FAQ and A1111's option text both say the noise source differs (CPU in ComfyUI, GPU by default in A1111, with a CPU option). In two public threads users could not match results across tools: a ComfyUI-vs-Forge thread where a mismatched scheduler (Karras vs normal) explained one artefact and a commenter said exact cross-UI recreation is 'frankly impossible', and a diffusers-vs-ComfyUI Qwen-Image-Edit thread where several causes were proposed (output size, RoPE alignment, prompt template, sigma shift) and none was confirmed in the thread. Treat seed + prompt as non-portable and compare like with like. Curator correction 2026-10-23 (discovery audit record C3-B681-05; sources re-fetched 2026-10-23, excerpts re-located by curator GET): Problem. C3-B060-G23-07 says several causes were proposed and 'none was confirmed in the thread'. Correction type: (c) missing an important limitation/finding. Method. A contributor (linoytsaban) tested the same script with and without height=1024,width=1024 and reported that omitting them matched ComfyUI quality; a Qwen maintainer (naykun) then advised against custom output height and width and called that likely the main reason. The reporter later disputed that this explains everything, and other hypotheses (RoPE text-frequency base, prompt template, sigma shift) stayed unresolved. Practical rule: for Qwen-Image-Edit in diffusers, let the pipeline compute the output size and keep conditioning images matched to it. Limitations. No maintainer confirmed that the size effect fully closes the gap. Version and date. Thread state as fetched 2026-10-23. Curator qualifications: Curator located all evidence excerpts in the work copies (automated case-insensitive prefix match over decoded files). Seed non-portability across UIs is well supported; the competing in-thread explanations are kept. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://github.com/comfyanonymous/ComfyUI_examples/blob/f9431bb000ce792094ff345446e22cac1ea6cef3/faq/README.md",
      "note": "FAQ"
    },
    {
      "url": "https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/shared_options.py",
      "note": "FAQ"
    },
    {
      "url": "https://github.com/Comfy-Org/ComfyUI/issues/7441",
      "note": "FAQ"
    },
    {
      "url": "https://github.com/huggingface/diffusers/issues/12216",
      "note": "FAQ"
    },
    {
      "url": "https://api.github.com/repos/huggingface/diffusers/issues/12216/comments",
      "note": "correction source (record C3-B681-05): comment by linoytsaban, 2025-08-22; comment by naykun, 2025-08-24; same comment"
    }
  ]
}