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Engine hangs and forces tournament restart loop in Arena when "Restart modules after each game" is enabled #1116

Description

@BernardBourbaki

Bug description

Environment

  • Reckless version: 0.10.0-dev-7300f044
  • GUI: Arena Chess GUI 3.5.1 (Windows)

Bug description
When running Reckless in an Arena tournament with the option "Restart engines after each game" enabled, any game involving Reckless fails to start/complete. Arena then restarts the whole tournament, which resumes at the same pairing and fails again — creating an infinite loop (the tournament counter keeps incrementing while stuck on the same pairing). This happens regardless of the opponent engine, the time control (tested at both 5+3 and 1+1), and regardless of whether an opening book/PGN start position is imposed.

What works

  • Reckless plays normally in single games (human vs Reckless, and Reckless vs another engine) launched manually outside tournament mode.
  • Restarting the whole Arena application periodically during a tournament (tested every 2 games via Arena's "Restart Arena after this many games" option) causes no problem at all.

What doesn't work

  • Enabling Arena's "Restart modules after each game" tournament option reliably causes the failure described above, on the first game involving Reckless.

Workaround
Disabling "Restart modules after each game" in Arena's tournament settings resolves the issue completely; the tournament then runs normally.

Hypothesis
Since a full Arena restart (which also relaunches the engine process) works fine, but the fast per-game module restart doesn't, the issue seems specific to how Reckless handles being killed and immediately relaunched in quick succession — possibly a race condition or an issue with stdin/stdout pipe handling during that rapid respawn cycle, rather than a general problem with cold starts.

Happy to provide the raw Arena debug/UCI log if useful.

Expected behavior

No response

Reproduction steps

No response

Operating system

Windows

Version

Win11

Activity

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