Wine's cmd.exe crashes (0xC0000005) when Kyber calls cmd /c start with
the EA auth URL, on native Linux Steam just as in Wolf. Fix:
1. Compile a minimal cmd shim with mingw-w64 (auto-installed if missing).
The shim intercepts cmd /c start <http url>, writes the URL to
C:\kyber_oauth_url.txt, and exits 0. All other cmd invocations are
passed through to the backed-up cmd-real.exe.
Installed into the Kyber prefix's system32 only — does not affect
other games or Proton globally.
2. Install a watcher script (~/.local/bin/kyber-oauth-watcher.sh) that
polls for the URL file and calls xdg-open to open it in the system
browser. Registered as a systemd user service so it starts on login.
Login flow: Kyber → cmd shim → URL file → watcher → xdg-open → browser
→ EA login → redirect to 127.0.0.1:PORT → Kyber loopback catches code.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D8ckUJQtj1pH8jtAddBDZs
Claude
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