Anthropic said during pre-release testing, 1,000 Fable 5.2 agents formalized the proof of Fermat's Last Theorem in Lean in 30 hours, compared to 26% completion in 18 hours by Opus 5.5

Autonomous systems that use large language models to plan, reason, and take actions — including browsing the web, writing code, calling APIs, and completing multi-step tasks with minimal human intervention.

AI research advances and the benchmarks used to measure progress.