Comfy self-start: embed Python at env root not detected; falls back to system python

[scryptio]

Today I wanted to give SwarmUI a try because it is often recommended and easier to handle than plain ComfyUI. I tried to add a new self-start backend using comfyui-rocm.

I run Swarm on AMD with two Comfy self-start backends: the normal dlbackend/comfy/ install and a second one pointed at comfyui-rocm under dlbackend/comfy-2/. I'm not asking anyone to bundle that repo — I just want the second backend to use that tree's Python (newer ROCm/torch than Comfy's portable bundle). StartScript is configurable, but as far as I can tell there's no real way to attach your own env unless it happens to match one of two hardcoded layouts.

What I see: backend enabled, StartScript = dlbackend/comfy-2/main.py (flat main.py). Swarm doesn't pick up the embed next to the install from comfyui-rocm's own installer (python_env). It launches bare python from PATH — in my case Windows Store Python 3.14 — and Comfy dies with wrong torch (Torch not compiled with CUDA enabled, Manager complaining PyTorch isn't installed). Logs showed the interpreter under AppData\Local\Python\pythoncore-3.14-64\..., not dlbackend\comfy-2\python_env\.... Pip/lib stuff during init also didn't match the process that actually ran main.py.

I read NetworkBackendUtils.ConfigurePythonExeFor on Windows. It only checks {main.py folder}/venv/Scripts/python.exe, then {parent}/python_embeded/python.exe (official portable: comfy/ComfyUI/main.py + comfy/python_embeded/python.exe). Otherwise it uses python from PATH. Official portable doesn't use Scripts/python.exe either — embed exe is at the env root; the bat does python_embeded\python.exe -s ComfyUI\main.py. comfyui-rocm is the same embed idea with python_env/python.exe at the env root and a flat layout (main.py at repo root). Renaming/junctioning venv → python_env didn't help because Swarm never looks for {env}/python.exe, only those two patterns. I don't want Swarm to hardcode python_env and every other fork name — that's the same problem with extra steps.

What got me working (fragile): mirror portable (ComfyUI/ subfolder, python_embeded → python_env), then fix the install's python312._pth so it has ../ComfyUI like official portable — otherwise No module named 'comfy' after nesting. Works, but I wouldn't wish it on anyone.

What I'd like to see: the default behaviour for your shipped install; discovery from StartScript (venv + embed-with-exe-at-root, not a growing list of folder names); optional explicit python path override (1277-style) for edge cases; no silent fallback to system python — fail with a clear message. If policy is really "self-start only for Swarm-installed layouts," say that in docs.

I didn't open a PR because 1277 was closed fast and I'd rather hear if this direction is acceptable first.

(Wording edited for clarity; paths and logs are from my Windows/AMD setup.)