The bootstrap fix hid the console windows the Rust shell spawns, but the running
backend is a second, larger source: it makes 70+ subprocess spawns (ffmpeg for
dubbing, engine sidecars, yt-dlp, demucs, WhisperX), only one of which set any
creation flag — and third-party libraries (imageio-ffmpeg, yt-dlp) shell out to
ffmpeg themselves. Since the backend runs console-less, on Windows each console
child got a fresh cmd window flashed on screen during generation/dubbing.
Patch subprocess.Popen once at backend startup (before anything spawns) to OR
CREATE_NO_WINDOW into every child's creationflags — covering run/call/
check_output (all built on Popen) and every stdlib-using library, from a single
auditable choke point. Composes with the existing CREATE_NEW_PROCESS_GROUP and
honours an explicit CREATE_NEW_CONSOLE. No-op on macOS/Linux. Unit-tested.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
