Major runtime and networking improvements
Async stack traces are now much more useful — Errors from native async APIs now keep async frames more consistently, and Error.captureStackTrace() matches new Error() for await-chain debugging.
Proxy and socket behavior got closer to Node/libuv — fetch() now picks up runtime HTTP_PROXY/HTTPS_PROXY/NO_PROXY changes, HTTPS proxy CONNECT tunnels are pooled and reused, and Unix socket lifecycle handling was fixed so Bun no longer steals live paths or leaves stale .sock files behind. macOS also gained a workaround for longer Unix socket paths.
File, stream, and protocol edge cases were hardened — ReadableStream.blob() now rejects cleanly on already-consumed bodies, process.stdout.end() waits for buffered writes, Linux statx fallbacks cover more real-world failures, UDP sockets surface ICMP/truncation metadata, and malformed multipart boundaries now error instead of crashing.
Build system and toolchain overhaul
Legacy CMake support was removed — Bun dropped the old CMake build path entirely, simplifying the repo and deleting a large amount of dead build infrastructure.
Local and release builds got faster and more flexible — The build system now supports IR PGO flags, shares caches across checkouts by default, preserves CPU targeting for local WebKit builds, and makes Zig checks first-class Ninja targets. Windows also fixed a codegen output mismatch that caused endless rebuilds.
Toolchain and CI workflows were modernized — The pinned Zig compiler was bumped, CI/build plumbing was updated around Buildkite, and the repo switched from a brittle scraper to bk-driven helpers for finding builds, logs, and failures.
Performance and safety fixes
Performance work landed in hot parsing paths — ANSI stripping and string-width helpers were sped up with SIMD/path optimizations.
Several correctness and security issues were fixed — MySQL query memory leaks were removed, DNS lookup no longer risks stack overflow on long hostnames, and tar extraction now skips absolute Windows paths during normalization.
Other misc changes
- Added in-process
Bun.cron(schedule, handler)with stop/unref-style lifecycle control - Updated bundled root CA trust store
- Numerous docs polish, CI test flake fixes, and small build-script cleanups