hermes - 💡(How to fix) Fix WhatsApp bridge opens blank node.exe console window on Windows [2 pull requests]

Bug Description

On Windows, enabling the WhatsApp gateway platform launches the Node.js WhatsApp bridge in a visible blank console window.

The bridge stdout/stderr are already redirected to whatsapp/bridge.log, so the console contains no useful output. If the user closes the blank console window, the bridge exits with Windows status 0xC000013A (3221225786), and the gateway reconnection watcher starts it again, causing the blank node.exe window to reappear.

Steps to Reproduce

1. Run Hermes Gateway on Windows with the WhatsApp platform enabled.
2. Wait for the WhatsApp adapter to start the Node bridge: scripts/whatsapp-bridge/bridge.js
3. Observe a visible blank node.exe console window.
4. Close that console window.
5. Observe the gateway logs and reconnection watcher relaunching the bridge.

Expected Behavior

The WhatsApp bridge should run hidden/backgrounded on Windows, with output going to whatsapp/bridge.log, and no blank console window should appear.

Actual Behavior

A blank node.exe console window appears. Closing it kills the bridge, then Hermes relaunches it.

Observed process command line:

node C:\Users\<user>\AppData\Local\hermes\hermes-agent\scripts\whatsapp-bridge\bridge.js --port 3000 --session C:\Users\<user>\AppData\Local\hermes\whatsapp\session --mode self-chat

Observed gateway log:

ERROR gateway.platforms.whatsapp: [Whatsapp] WhatsApp bridge process exited unexpectedly (code 3221225786).
ERROR gateway.run: Fatal whatsapp adapter error (whatsapp_bridge_exited): WhatsApp bridge process exited unexpectedly (code 3221225786).
INFO gateway.run: whatsapp queued for background reconnection
INFO gateway.run: Reconnecting whatsapp (attempt 1)...

Likely Root Cause

gateway/platforms/whatsapp.py starts the bridge with subprocess.Popen(...) and redirects stdout/stderr, but does not pass a Windows creationflags value.

Current shape around the bridge launch:

self._bridge_process = subprocess.Popen(
    ["node", str(bridge_path), ...],
    stdout=bridge_log_fh,
    stderr=bridge_log_fh,
    preexec_fn=None if _IS_WINDOWS else os.setsid,
    env=bridge_env,
)

On Windows, launching a console subsystem executable like node.exe from a pythonw.exe gateway process can still allocate/show a new console window unless CREATE_NO_WINDOW is used.

Suggested Fix

Use subprocess.CREATE_NO_WINDOW when _IS_WINDOWS, while preserving os.setsid for POSIX:

popen_kwargs = {
    "stdout": bridge_log_fh,
    "stderr": bridge_log_fh,
    "env": bridge_env,
}
if _IS_WINDOWS:
    popen_kwargs["creationflags"] = getattr(subprocess, "CREATE_NO_WINDOW", 0x08000000)
else:
    popen_kwargs["preexec_fn"] = os.setsid

self._bridge_process = subprocess.Popen(
    ["node", str(bridge_path), "--port", str(self._bridge_port), "--session", str(self._session_path), "--mode", whatsapp_mode],
    **popen_kwargs,
)

Hermes already uses this pattern elsewhere on Windows, e.g. hermes_cli/gateway_windows.py for avoiding console flashes.

Environment

• OS: Windows 10
• Hermes install path: %LOCALAPPDATA%\hermes\hermes-agent
• Gateway started via scheduled task / pythonw.exe -m hermes_cli.main gateway run --replace
• WhatsApp platform enabled