Opus 5.5 proves software properties with about 40% fewer tokens than Opus 5

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Theorem's research pipeline uses Claude to turn existing fuzz tests into specifications and generate formal proofs for compiled production code. The Rocq kernel checks those proofs, and a subset is being published for independent verification and reuse.

Here is what makes this credible:

• The work covered 239 entry points across 123 OSS-Fuzz libraries, generating about 180 million lines of Rocq proofs.
• Opus 5.5 proved half of 36 verification tasks using about 40% fewer tokens than Opus 5.
• Sharing proof work cut token use by 17% compared with agents working alone.
• Theorem offers to run the pipeline on other open-source projects and is publishing a Claude skill.

One catch: Proofs can require hundreds of millions of tokens. Coverage is limited to specified crash properties for inputs up to 64 MB, under a single-threaded, static RISC-V Linux setup with a fixed memory budget. This does not establish that entire libraries are bug-free.

Sources: anthropic.com