`comfy launch --background` fails with FileNotFoundError when comfy-cli is invoked by path

[cancan101]

Describe the bug
background_launch() re-execs the CLI as a bare "comfy" through subprocess.Popen (no shell=True), so the child is resolved via PATH. When comfy-cli is invoked by its own path from a virtualenv that hasn't been activated — e.g. /path/to/.venv/bin/comfy launch --background — the child spawn raises FileNotFoundError and the launch dies with an unhandled traceback.

This is a normal way to use a Python console script (it's how a script or launcher invokes a tool it installed into a project-local venv), and comfy-cli otherwise anchors subprocesses properly — resolve_python.py and uv.py use sys.executable throughout. Only this call site assumes PATH.

To Reproduce

python3 -m venv .venv-comfy
.venv-comfy/bin/pip install comfy-cli

# a stand-in workspace is enough to reach the failing call
mkdir -p fake-ws && echo 'print("hi")' > fake-ws/main.py

# the key condition: `comfy` is NOT on PATH
env -i HOME="$HOME" PATH=/usr/bin:/bin \
  ./.venv-comfy/bin/comfy --skip-prompt --workspace="$PWD/fake-ws" launch --background

Environment

• comfy-cli 1.15.0
• Python 3.11, Linux (originally hit on macOS / Apple silicon)
• comfy-cli installed into a project-local venv and invoked without activating it

Observed

FileNotFoundError: [Errno 2] No such file or directory: 'comfy'

…raised from comfy_cli/command/launch.py → background_launch → subprocess.Popen.

Expected behavior
The background launch should start, as it does when the same binary's directory happens to be on PATH. Re-running the identical command with only PATH="$PWD/.venv-comfy/bin:$PATH" changed gets past the spawn and executes the workspace — PATH is the only variable.

Cause

comfy_cli/command/launch.py, in background_launch():

cmd = [
    "comfy",
    f"--workspace={os.path.abspath(os.getcwd())}",
    "launch",
]
...
process = subprocess.Popen(
    cmd,
    stdout=logfh,
    stderr=subprocess.STDOUT,
    env=env,
)

cmd[0] is a bare name, so Popen resolves it against PATH — which need not contain the comfy-cli that is currently running.

Suggested fix

Anchor the re-exec to the running installation rather than to PATH. Either of these is a no-op when comfy is on PATH:

cmd = [sys.argv[0], f"--workspace={...}", "launch"]                     # the path actually invoked
cmd = [sys.executable, "-m", "comfy_cli", f"--workspace={...}", "launch"]   # interpreter-anchored

sys.executable-based spawning would also match what resolve_python.py / uv.py already do.

Secondary note

Because the failure happens after the parent prints Launching ComfyUI from: <workspace>, it reads as though ComfyUI itself failed to start, which sends you looking at the workspace and its models rather than at the CLI. Catching FileNotFoundError around the spawn and reporting something like "could not re-exec comfy; is it on PATH?" would make the failure self-explanatory even before the fix above.

Nice to have

• Terminal output
• Screenshots

Additional context
Add any other context about the problem here.

[dosubot]

Hi @cancan101! I'm Dosu and I'm helping the Comfy Org team.

This is a valid bug — the bare "comfy" in background_launch() is inconsistent with the rest of the codebase. Other call sites that re-exec comfy-cli subcommands already use [sys.executable, "-m", "comfy_cli", ...]:

• run_cli.py builds commands as [sys.executable, "-m", "comfy_cli"]
• watcher.py spawns watch jobs with [sys.executable, "-m", "comfy_cli", "_watch", ...]
• models.py spawns download workers with [sys.executable, "-m", "comfy_cli", "model", "_download-worker", ...]

Similarly, resolve_python.py and uv.py consistently use sys.executable rather than bare command names [1] [2].

The fix in background_launch() [3] would be straightforward — replacing the bare "comfy" with [sys.executable, "-m", "comfy_cli", ...] to match the established pattern. The sys.executable approach is likely preferable over sys.argv[0] since the rest of the codebase already uses it, and it avoids edge cases where sys.argv[0] might be a relative path that doesn't survive a cwd change.

PR #643 recently did analogous work for bare git/ffmpeg/ffprobe commands [4], but didn't touch this call site.

Good catch on the error reporting angle too — the FileNotFoundError after the "Launching ComfyUI from:" message is misleading.

To reply, just mention @dosu.

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