Node trace-events compatibility lands (
5b55beb)
Bun now implements Node’s trace_events subsystem end to end, including JSON trace output, the --trace-event-* / --trace-env / --trace-exit flags, per-subsystem events, worker thread tids, and the NodeTracing inspector domain. The change also ports 34 upstream v26.3.0 trace tests, so this is both a compatibility boost and a substantial new debugging capability.
SIMD-backed JSON parser rewrite (
6640fcf)
bun_parsers::json was rewritten around a SIMD structural index, replacing the old byte-at-a-time lexer and mutable AST builder with an immutable row AST. This affects core parsing paths like package.json, lockfiles, registry manifests, .jsonc, bundler loaders, and env/define parsing, so it’s a major performance and architecture change.
WebSocket receive/dispatch path no longer holds exclusive refs across callbacks (5124b0c)
The WebSocket client was refactored to use interior mutability instead of carrying an exclusive mutable borrow through user callbacks. That removes a large class of reentrancy/borrow hazards and makes the receive path more robust, but it is also a deep internal refactor with lots of touched code.
Sparse array inspection no longer walks every hole (
48a4b01)
Printing huge sparse arrays now skips hole runs in one step instead of probing index-by-index, which fixes a hang/CPU peg when inspecting arrays with enormous length and few or no elements. This is a user-visible bug fix for logging/inspection of pathological arrays.
MySQL caching_sha2_password fast auth fixed (2c62c01)
Bun now builds the fast-auth scramble in the correct operand order and keeps the connection in the authenticating state until the server’s concluding OK/ERR packet arrives. That restores compatibility with warmed MySQL 8 auth caches and fixes a real login path.
Windows process.env now behaves more like Node (5b55beb)
Windows environment proxying now preserves original key casing for enumeration/JSON output and falls back correctly for non-env properties and prototype methods. This matters for JSON.stringify(process.env), IPC env echoes, and Node-style property checks like hasOwnProperty.
bun pm pkg set fixed a use-after-free (b124ed3)
Bracketed key-path segments no longer reuse freed memory when writing nested package.json keys. This was a correctness and safety issue that could corrupt output JSON, so it’s a meaningful bug fix.
Archive UTF-8/non-ASCII entry names fixed (1773b96)
Archive read/write now handles non-ASCII entry names correctly across platforms, including Windows pathname conversion and libarchive’s warning-vs-failure behavior. That unblocks archives containing names like 日本.txt and prevents silent entry loss or creation failures.
Bun.spawn Windows stdin shutdown bug fixed (ae6051b)
A Windows-specific shutdown path now stops hanging when a spawned child dies while stdin is an async iterable. This resolves a real process-lifecycle bug and a CI-flaky spawn case.
bun:ffi preserves NaN, -0, and BigInt conversions (d816daf)
f64 argument conversion now passes the correct values through to native code instead of silently normalizing them first. That fixes observable ABI behavior for native interop.
bun install dependency resolution and file: handling fixed (56c514a, 5585f36, 253e487)
Local file: dependency graphs, lockfile migration, and auto-install name lookup all got correctness fixes. These address real install-time breakage in vendored or migrated projects, especially around transitive local packages and exact-version package resolution.
CSS selector parsing tightened (725f46e)
nth-child(... of ...) and :has() are now parsed non-forgivingly, rejecting invalid or empty selector lists instead of recovering into malformed output. This improves standards compliance and prevents silently emitting broken CSS.
inspect/WebKit stack of compatibility fixes and sync (00a93bd, eb6c0fe, d6a82e7, 7f33321, 570f857, 8973584, 3128951, 27009bf, eba370b)
A WebKit sync, a GC crash fix, a build-artifact type confusion fix, and several smaller runtime correctness tweaks landed together. These are important, but they’re narrower than the main feature and bug-fix work above.
Other misc changes
- WebKit sync and related compatibility adjustments (1 commit)
- Small GC/error-stack follow-up comment cleanup
- Docker image CA-certificate packaging fix
- Error/stack trace review nit cleanup
- Type declarations and internal builtins cleanup