Claude vs Codex chess match ends in draw: Opus 5.5 was winning but ran out of time
edgarpavlovsky · x · 2026-10-05
A developer had Claude and Codex play a 30-minute chess game against each other via the chess.com iOS app using only GUI computer use — the result was a draw, with Claude clearly winning before running out of time.
Key takeaways:
- The match quality was surprisingly high given the models were only clicking through a GUI; just one illegal move attempt, immediately self-corrected
- Opus 5.5 ignored the clock until the final minutes, then started pre-moving
- Both used default coding harnesses, the tapkit MCP, and high reasoning
- The long-tail bottleneck was sleep time between decisions; better prompting, skill hill climbing and MCP tuning could cut completion time substantially
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