Claude Code v2.1.181 and later ship with a Rust port of Bun, according to Jarred Sumner. Inspection of local installations confirms version "Bun v1.4.0" and 563 Rust source files embedded in the binary, supporting the claim that the unreleased Rust-based Bun runs in production across millions of devices. Sumner noted startup improved 10% on Linux with otherwise minimal visible impact.
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