RetroChessBench found frontier models failing 22 of 24 attempts at reconstructing legal chess histories
AspireAI community · arXiv
Retrograde chess asks a solver to reconstruct legal histories and distinguish events that are merely possible from those that are forced, which the authors treat as a clean test of pure reasoning under explicit rules. RetroChessBench provides 12 tasks covering exact-length constructions, unique endings and exhaustive answer sets, with references, rubrics and a terminal-reward reinforcement learning environment. In two trials per task and condition, GPT 6 Astra High failed to produce the required final answer in 22 of 24 attempts without tools and 18 of 24 with code execution, with mean terminal RL rewards of 14.75 percent and 27.19 percent respectively. The failed responses reject legal histories and treat temporary obstructions as permanent, and the authors hypothesize that web-derived training data rarely contains the missing detailed derivations, which points at training coverage rather than reasoning architecture.
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