After extensive testing, Wine/Proton loads cmd.exe exclusively from
Proton's own installation (files/lib/wine/x86_64-windows/cmd.exe).
Replacing the prefix system32 copy, IFEO registry keys, WINEDLLOVERRIDES,
and Wine DllOverrides registry entries all have no effect — Proton's copy
always takes precedence.
The working fix: compile a tiny shim (GetCommandLineA scan for http URLs,
write to C:\kyber_oauth_url.txt, ExitProcess(0)) and replace Proton's
cmd.exe directly, backing up the original as cmd.exe.bak. The script
detects size (shim ~9KB vs real cmd.exe ~1.2MB) to avoid double-replacing.
Note for users: re-run setup-kyber-linux.sh after any Proton Experimental
update since Steam restores the original cmd.exe on update.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D8ckUJQtj1pH8jtAddBDZs
Claude
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