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Anthropic says Claude proved crash-free properties on 123 open-source libraries
Anthropic said Thursday that Claude, working with Theorem, produced assembly-level formal proofs covering 123 OSS-Fuzz libraries, a scale the lab called newly practical for production software.
- New headline Was: “LLMs are making formal software verification feasible at a much larger scale”
- Our desk filed its story
- anthropic.com is now reporting this
Anthropic said Thursday that its Claude model, in a collaboration with Theorem, produced formal proofs of crash-free behavior for 239 fuzz-test entry points across 123 open-source libraries drawn from Google's OSS-Fuzz program1.
The lab said the proofs operate on compiled RISC-V assembly and cover every input smaller than 64 MB, under assumptions that include a single-threaded static binary, a fixed memory budget, a RISC-V CPU and a Linux operating system1. It described the work as, to its knowledge, the first large-scale effort to use AI to apply formal verification to production software at the assembly level1.
Formal verification translates code into a mathematical model and tries to prove it always follows stated rules, Anthropic wrote1. The lab said that historically took years of specialist effort, citing seL4 as taking two person-years to implement and 20 to verify1.
Anthropic said Claude converted existing fuzz tests into a specification that the test never crashes, then proved that specification1. The proofs comprise about 180 million lines of Rocq, with a typical proof about 600,000 lines covering binaries whose median length is about 18,000 RISC-V instructions, the post said1.
The company said it is publishing a subset of the proofs and RISC-V and Linux process semantics on GitHub, and that Theorem is offering the same pipeline to other open-source projects and publishing a Claude skill for developers1. While writing proofs, Claude also found bugs that had gone undetected despite heavy fuzzing, Anthropic said1.
The post stressed that verified does not mean bug-free1. Remaining bugs could sit in the RISC-V and Linux models, the theorem statements, the Rocq checker, or outside the spec, including on x86 or ARM, with glibc, or in callers of the libraries1. AddressSanitizer, which the fuzz tests used, also does not catch every memory-safety bug, Anthropic wrote1.
Named authors include Keane Lucas, Aengus Lynch, Luna Tong, Luke Champine, Nicholas Carlini and others1. Independent confirmation of the proofs was not in the record reviewed here beyond Anthropic's own post and linked repositories1.