AdderBoard challenge: smallest transformer that adds two 10-digit numbers, records keep falling

DimitrisPapail · x · 2026-11-07

AdderBoard is a community challenge on GitHub (397 stars): train the smallest transformer that adds two 10-digit numbers with ≥99% accuracy on a held-out 10K test set. It started when the same prompt given to Claude Code yielded a 6,080-param model and Codex squeezed out 1,644 params; the community has pushed the number far lower. Two leaderboard categories track generic training algorithms, with verify.py and a submission template for entries.

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