Automatic Textbook Formalization
arXiv cs.AI / 4/6/2026
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Key Points
- The paper presents an AI-driven case study that automatically formalizes a 500+ page graduate-level algebraic combinatorics textbook into Lean, producing a standalone formalization rather than only adapting existing library material.
- The output is substantial—about 130K lines of Lean code with roughly 5,900 Lean declarations—indicating a major step up in scale and proficiency compared with prior textbook formalization efforts.
- The formalization was completed in one week using 30K Claude 4.5 Opus agents operating in parallel on a shared version-controlled code base, and it reportedly sets a multi-agent software engineering record with usable results.
- The authors argue the inference cost is comparable to or lower than estimated salaries for human expert teams, suggesting potential near-term economic advantages and efficiency gains even without improved models.
- The resulting Lean codebase and a side-by-side blueprint website are released as open source, aiming to enable reproducibility and further progress by others.
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