The recurring Windows desktop console-flash bug (#54220) is governed by the
*parent's* console, not by each child spawn. The desktop backend was launched as
GUI-subsystem pythonw.exe, which has no console at all — so every
console-subsystem child it spawns (git, gh, cmd, wmic, powershell, ...) had to
allocate its own console, flashing a window. That is why the fix had become an
endless per-call-site sweep of CREATE_NO_WINDOW flags: each leaf spawn was
papering over a missing console on the root.
Launch the backend as the venv's console python.exe instead. Under the existing
hiddenWindowsChildOptions() wrapper (windowsHide: true -> CREATE_NO_WINDOW) the
backend owns a single *windowless* console, and every descendant spawn inherits
it instead of allocating a visible one. This makes "no flashing windows" a
property of the one backend launch rather than a flag that must be remembered at
every spawn site — including spawns inside third-party libraries that no
call-site sweep can reach.
Verified on Windows 11 25H2 (Windows Terminal default): with the per-site hide
flag forcibly neutered, the canonical culprits (git/gh/cmd/wmic/powershell)
spawned naively and none flashed, while the same naive spawn from the old
console-less pythonw parent did flash — isolating the parent console as the cause.
Two premises behind the old pythonw approach did not hold up on current Windows
and are dropped here:
- The venv Scripts\python.exe uv shim, under CREATE_NO_WINDOW, re-execs base
python *windowless* — it does not flash a conhost (the #52239 concern), so the
base-pythonw detour is unnecessary.
- Console python restores stdout, so the backend announces its port on the normal
HERMES_DASHBOARD_READY stdout line; the pythonw-only ready-file side channel is
no longer needed and the readyFile opt-in is removed.
Removes the now-dead pythonw machinery (getNoConsoleVenvPython, toNoConsolePython,
applyWindowsNoConsoleSpawnHints, readVenvHome) and updates the test to assert the
new invariant: backend command is never pythonw, both backend spawns still go
through hiddenWindowsChildOptions, and no backend opts into the ready-file path.
Scope: this fixes the high-frequency backend-descendant flash classes. The
updater/UAC handoff (#54543) and embedded-terminal PTY accumulation (#53555)
classes have separate root causes and are unaffected.
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