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setup_env()

# prestartup_script.py
from comfy_env import setup_env; setup_env()

The launch-time entry point. ComfyUI core executes each pack's prestartup_script.py on every launch, before the server boots and before any node imports.

This happens before ComfyUI imports torch, folder_paths or comfy.model_management, and that is why process-wide hygiene belongs here and nowhere else. register_nodes() runs much later, at custom-node import time; both finish before the server binds a port.

setup_env() is mostly a health report plus environment hygiene.

What it does, in order

  1. Enable faulthandler: if native code segfaults later in the run, we get a Python traceback on stderr instead of a silent death.

  2. Print the startup banner: walks the pack for comfy-env.toml files and reports each isolation env's resolved workspace path and state:

    [comfy-env] comfyui-motioncapture: 1 isolation env(s):
[comfy-env]   nodes -> ...\custom_nodes\comfyui-motioncapture\nodes
[comfy-env]     env: ...\comfy-env\envs\motioncapture-nodes_py313-torch2.10-cu128\.pixi\envs\default  [OK]
[comfy-env] prestartup complete

    A [MISSING] status means the config was discovered but the env was never materialized. That line names the pack and the exact command, because the header above it scrolls away once several packs report:

    [comfy-env]     env: ...  [comfyui-motioncapture: MISSING -- run
`comfy-env install --dir .../custom_nodes/comfyui-motioncapture`]

  3. dedupe_libomp(): macOS only: symlinks redundant bundled libomp.dylib copies to torch's canonical one, because multiple loaded copies corrupt OpenMP runtime state and segfault inside native filters (ADR-0009). No-op elsewhere.

What it does NOT do

No pip, no pixi, no network, no writes to the workspace. A missing env is reported, not repaired.

It does not patch ComfyUI's globals as a principle.

One process-wide side effect is worth naming because it is not part of setup_env() at all but of the import comfy_env line that precedes it: the package's install/__init__.py (pulled in by the facade) sets os.environ["PYTHONUNBUFFERED"] = "1" and reconfigures sys.stdout and sys.stderr to line buffering for the whole process. That happens on import, before setup_env() runs, and stays in effect for ComfyUI's lifetime.