bun

Bun v1.4.3, published October 10, 2026, adds bun check, a built-in type checker ported from typescript-go that Bun says matches tsc 7.0.2 output and runs 3x to 6.4x faster, plus --check flags for run, test and build.

GitHub says it rewrote the Copilot agent runtime into more than 800,000 lines of Rust using its own Copilot coding agents, at a roughly $120,000 token cost.

Bun 1.4, released August 20, is the first stable version built entirely on the runtime's contested Rust rewrite, delivering 30x faster package installs and 5x lower idle CPU usage.

Jarred Sumner merged PR

Anthropic's first major Bun release since acquiring the runtime tackles long-running-process leaks, adds isolate, parallel and shard test flags, and lands days after Pulumi made Bun a fully supported infrastructure-as-code runtime.