Anthropic uses Claude to migrate Messages API to Rust

According to a report by InfoQ Chinese, Anthropic's platform engineering lead Katelyn Lesse revealed that the company recently completed an engineering overhaul in which a team that initially had no Rust developers migrated the Messages API from Python to Rust, with help from Claude. After the migration, CPU resource consumption for the relevant service dropped by roughly 40%–50%, and first token latency improved by around 10%–20%.

In this project, Claude handled the bulk of the coding, while human engineers focused on system architecture, migration strategy, and validation. Lesse also published a long post on X on October 26 titled "The new set of problems for engineers to solve," in which she argued that as Agents go beyond answering questions and executing simple tasks and begin to run autonomously for extended periods and collaborate with one another, new engineering challenges emerge around isolation, state persistence, and scheduling. She suggested that the value of engineers is shifting away from writing code toward defining problem boundaries and ensuring system reliability.

The migration is now complete, and the concrete results reported so far are the reductions in CPU usage and first token latency, along with a division of labor in which Claude does the mainline coding and humans focus on architecture, migration strategy, and verification.