On ARM64 Windows, Chocolatey installs x64 cmake and LLVM. x64 cmake
reads PROCESSOR_ARCHITECTURE=AMD64 (overridden by OS for x64 processes),
causing CMAKE_SYSTEM_PROCESSOR=AMD64 and -march=haswell to be passed to
ARM64 clang-cl.
- Add ARM64 detection to bootstrap.ps1
- Install cmake ARM64 MSI directly from GitHub on ARM64
- Install LLVM ARM64 (woa64) installer directly from GitHub on ARM64
- Skip nasm (x86 assembler) and mingw on ARM64
- Warn about bun ARM64 not being available via Chocolatey
cmake.exe is an x64 binary, so the OS sets PROCESSOR_ARCHITECTURE=AMD64
when it runs on ARM64 Windows. This causes cmake to misdetect as x64
and use -march=haswell. Explicitly set CMAKE_SYSTEM_PROCESSOR=ARM64.
VS dev shell with -HostArch amd64 sets PROCESSOR_ARCHITECTURE=AMD64,
causing CMake to misdetect the system as x64 and use -march=haswell
on ARM64. Restore PROCESSOR_ARCHITECTURE=ARM64 after VS dev shell.
## Summary
- Fix a use-after-free bug in the bindgen code generator where string
arguments with default values would have their underlying WTF::String
destroyed before the BunString was used
- The issue occurred because for optional string parameters with
defaults, a WTF::String was created inside an `if` block, converted to
BunString, then the if block closed and destroyed the WTF::String while
the BunString was still in use
- This manifested as a segfault in `Bun.stringWidth()` and potentially
other functions using optional string arguments
## Details
The crash stack trace showed:
```
Segmentation fault at address 0x31244B0F0
visible.zig:888: string.immutable.visible.visible.visibleUTF16WidthFn
BunObject.zig:1371: bindgen_BunObject_dispatchStringWidth1
GeneratedBindings.cpp:242: bindgen_BunObject_jsStringWidth
```
The generated code before this fix looked like:
```cpp
BunString argStr;
if (!arg0.value().isUndefinedOrNull()) {
WTF::String wtfString_0 = WebCore::convert<...>(...);
argStr = Bun::toString(wtfString_0);
} // <-- wtfString_0 destroyed here!
// ... argStr used later, pointing to freed memory
```
The fix declares the WTF::String holder outside the if block:
```cpp
BunString argStr;
WTF::String wtfStringHolder_0; // Lives until function returns
if (!arg0.value().isUndefinedOrNull()) {
wtfStringHolder_0 = WebCore::convert<...>(...);
}
if (!wtfStringHolder_0.isEmpty()) argStr = Bun::toString(wtfStringHolder_0);
// argStr now points to valid memory
```
This fix applies to both:
- Direct string function arguments with defaults (e.g.,
`t.DOMString.default("")`)
- Dictionary fields with string defaults
## Test plan
- [x] Existing `stringWidth.test.ts` tests pass (105 tests)
- [x] Manual testing with GC stress shows no crashes
- [x] `os.userInfo()` with encoding option works correctly
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
## Summary
- Update LLVM version references across build scripts, Dockerfiles, CI,
Nix configs, and documentation
- Fix LLVM 21 `-Wcharacter-conversion` errors in WebKit bindings:
- `EncodingTables.h`: pragma for intentional char32_t/char16_t
comparisons
- `TextCodecCJK.cpp`: widen `gb18030AsymmetricEncode` param to char32_t
- `URLPatternParser`: widen `isValidNameCodepoint` param to char32_t,
cast for `startsWith`
- Fix `__libcpp_verbose_abort` noexcept mismatch (LLVM 21 uses
`_NOEXCEPT`)
- Fix dangling pointer in `BunJSCModule.h` (`toCString` temporary
lifetime)
- Remove `useMathSumPreciseMethod` (removed upstream in JSC)
**Before merging:** Merge https://github.com/oven-sh/WebKit/pull/153
first, then update `WEBKIT_VERSION` in `cmake/tools/SetupWebKit.cmake`
to point to the merged commit.
## Test plan
- [ ] Build bun debug on macOS with LLVM 21
- [ ] Build bun on Linux (glibc)
- [ ] Build bun on Linux (musl)
- [ ] Build bun on Windows
- [ ] Run test suite
Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
## Summary
- Add `[Symbol.dispose]` to mock function prototype, aliased to
`mockRestore`
- Enables `using spy = spyOn(obj, "method")` to auto-restore when
leaving scope
- Works for both `spyOn()` and `mock()`
Addresses #6040 — gives users a clean way to scope spy lifetimes instead
of manually calling `mockRestore()` or relying on `afterEach`.
### Example
```ts
import { spyOn, expect, test } from "bun:test";
test("auto-restores spy", () => {
const obj = { method: () => "original" };
{
using spy = spyOn(obj, "method").mockReturnValue("mocked");
expect(obj.method()).toBe("mocked");
}
// automatically restored
expect(obj.method()).toBe("original");
});
```
## Test plan
- `bun bd test test/js/bun/test/mock-disposable.test.ts` — 3 tests pass
- Verified tests fail with `USE_SYSTEM_BUN=1`
## Summary
- Make `defaultRemainingRunsUntilSkipReleaseAccess` configurable at
runtime instead of a compile-time constant
- Add `BUN_GC_RUNS_UNTIL_SKIP_RELEASE_ACCESS` environment variable to
control how many idle event loop iterations pass before skipping JSC
heap `releaseAccess` calls in `onBeforeWait`
- Default remains 10, matching the previous hardcoded value
## Test plan
- [ ] Verify default behavior is unchanged (no env var set, value is 10)
- [ ] Verify `BUN_GC_RUNS_UNTIL_SKIP_RELEASE_ACCESS=0` causes release
access to be skipped every iteration
- [ ] Verify `BUN_GC_RUNS_UNTIL_SKIP_RELEASE_ACCESS=100` delays skipping
for 100 idle iterations
- [ ] Verify negative values are ignored (default is preserved)
- [ ] Verify non-numeric values are ignored (default is preserved)
## Changelog
<!-- CHANGELOG:START -->
<!-- CHANGELOG:END -->
🤖 Generated with [Claude Code](https://claude.com/claude-code) (0%
3-shotted by claude)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
## Summary
This is a tiny optimization that skips creating and dispatching an Event
object when `AbortSignal.abort()` is called with no registered
listeners.
## Changes
When there are no listeners (no `addEventListener` or `onabort`), we now
check `hasEventListeners()` before creating the Event, avoiding:
- Event object allocation (~112 bytes)
- EventPath creation
- dispatchEvent overhead (hash map lookups, method calls)
## Performance
Improvement for the no-listener case:
- **~6% faster** in micro-benchmarks
- ~16ms saved per 1M `abort()` calls (271ms → 255ms)
| Case | Before | After | Improvement |
|------|--------|-------|-------------|
| no listener | 271 ms | 255 ms | ~6% |
| with listener | 368 ms | 370 ms | (same) |
## Why this is safe
The optimization has no observable side effects because:
- `dispatchEvent` is called from C++, not observable via JS
monkey-patching
- Without listeners, no code can obtain a reference to the Event object
- All internal state (`aborted`, `reason`) is set correctly regardless
## Test Plan
- Existing AbortController/AbortSignal tests pass
- Added mitata benchmark: `bench/snippets/abort-signal.mjs`
## Summary
- Fix path normalization for "." on Windows where `normalizeStringBuf`
was incorrectly stripping it to an empty string
- This caused `existsSync('.')`, `statSync('.')`, and other fs
operations to fail on Windows
## Test plan
- Added regression test `test/regression/issue/26631.test.ts` that tests
`existsSync`, `exists`, `statSync`, and `stat` for both `.` and `..`
paths
- All tests pass locally with `bun bd test
test/regression/issue/26631.test.ts`
- Verified code compiles on all platforms with `bun run zig:check-all`
Fixes#26631🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
## Summary
- Add validation to require `--compile` when using ESM bytecode
- Update documentation to clarify ESM bytecode requirements
## Why
ESM module resolution is two-phase: (1) analyze imports/exports, (2)
evaluate. Without `--compile`, there's no `module_info` embedded, so JSC
must still parse the file for module analysis even with bytecode -
causing a double-parse deopt.
## Changes
- **CLI**: Error when `--bytecode --format=esm` is used without
`--compile`
- **JS API**: Error when `bytecode: true, format: 'esm'` is used without
`compile: true`
- **Docs**: Update bytecode.mdx, executables.mdx, index.mdx to clarify
requirements
- **Types**: Update JSDoc for bytecode option in bun.d.ts
## Test plan
```bash
# Should error
bun build ./test.js --bytecode --format=esm --outdir=./out
# error: ESM bytecode requires --compile. Use --format=cjs for bytecode without --compile.
# Should work
bun build ./test.js --bytecode --format=esm --compile --outfile=./mytest
bun build ./test.js --bytecode --format=cjs --outdir=./out
```
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Adds `--cpu-prof-interval` to configure the CPU profiler sampling
interval in microseconds (default: 1000), matching Node.js's
`--cpu-prof-interval` flag.
```sh
bun --cpu-prof --cpu-prof-interval 500 index.js
```
- Parsed as `u32`, truncated to `c_int` when passed to JSC's
`SamplingProfiler::setTimingInterval`
- Invalid values silently fall back to the default (1000μs)
- Warns if used without `--cpu-prof` or `--cpu-prof-md`
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
## Summary
Fixes#26625
This fixes a segmentation fault that occurred on Windows x64 when the GC
finalizer tried to free shell interpreter resources that were already
partially freed during normal shell completion.
- Added explicit `cleanup_state` enum to track resource ownership state
- `needs_full_cleanup`: Nothing cleaned up yet, finalizer must clean
everything
- `runtime_cleaned`: `finish()` already cleaned IO/shell, finalizer
skips those
- Early return in `#derefRootShellAndIOIfNeeded()` when already cleaned
- Explicit state-based cleanup in `deinitFromFinalizer()`
The vulnerability existed on all platforms but was most reliably
triggered on Windows with high GC pressure (many concurrent shell
commands).
## Test plan
- [x] Build passes (`bun bd`)
- [x] New regression test added (`test/regression/issue/26625.test.ts`)
- [x] Existing shell tests pass (same 4 pre-existing failures, no new
failures)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
## Summary
- `bun run build:local` now handles everything: configuring JSC,
building JSC, and building Bun in a single command on all platforms
(macOS, Linux, Windows). Previously required manually running `bun run
jsc:build:debug`, deleting a duplicate `InspectorProtocolObjects.h`
header, and then running the Bun build separately.
- Incremental JSC rebuilds: JSC is built via `add_custom_target` that
delegates to JSC's inner Ninja, which tracks WebKit source file changes
and only rebuilds what changed. `ninja -Cbuild/debug-local` also works
after the first build.
- Cross-platform support:
- macOS: Uses system ICU automatically
- Linux: Uses system ICU via find_package instead of requiring bundled
static libs
- Windows: Builds ICU from source automatically (only when libs don't
already exist), sets up static CRT and ICU naming conventions
### Changes
- cmake/tools/SetupWebKit.cmake: Replace the old WEBKIT_LOCAL block
(which just set include paths and assumed JSC was pre-built) with full
JSC configure + build integration for all platforms
- cmake/targets/BuildBun.cmake: Add jsc as a build dependency, use
system ICU on Linux for local builds, handle bmalloc linking for local
builds
- CONTRIBUTING.md / docs/project/contributing.mdx: Simplify "Building
WebKit locally" docs from ~15 lines of manual steps to 3 lines
## Test plan
- [x] macOS arm64: clean build, incremental rebuild, WebKit source
change rebuild
- [x] Windows x64: clean build with ICU, incremental rebuild with ICU
skip
- [x] Linux x64: build with system ICU via find_package
- [x] No duplicate InspectorProtocolObjects.h errors
- [x] build/debug-local/bun-debug --version works
Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude <noreply@anthropic.com>
### What does this PR do?
Extract NO_PROXY checking logic from getHttpProxyFor into a reusable
isNoProxy method on the env Loader. This allows both fetch() and
WebSocket to check NO_PROXY even when a proxy is explicitly provided via
the proxy option (not just via http_proxy env var).
Changes:
- env_loader.zig: Extract isNoProxy() from getHttpProxyFor()
- FetchTasklet.zig: Check isNoProxy() before using explicit proxy
- WebSocket.cpp: Check Bun__isNoProxy() before using explicit proxy
- virtual_machine_exports.zig: Export Bun__isNoProxy for C++ access
- Add NO_PROXY tests for both fetch and WebSocket proxy paths
### How did you verify your code works?
Tests
---------
Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
## Summary
- Fix type definition for `Socket.reload()` to match runtime behavior
- The runtime expects `{ socket: handler }` but types previously
accepted just `handler`
## Test plan
- [x] Added regression test `test/regression/issue/26290.test.ts`
- [x] Verified test passes with `bun bd test`
Fixes#26290🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Alistair Smith <hi@alistair.sh>
## Summary
- Adds missing SIMD variants to the `Build.Target` TypeScript type
- The runtime accepts targets like `bun-linux-x64-modern` but TypeScript
was rejecting them
- Generalized the type to use `${Architecture}` template where possible
## Test plan
- [x] Added regression test in `test/regression/issue/26247.test.ts`
that validates all valid target combinations type-check correctly
- [x] Verified with `bun bd test test/regression/issue/26247.test.ts`
Fixes#26247🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Alistair Smith <hi@alistair.sh>
## Summary
- Adds missing `bun-linux-x64-baseline` and `bun-linux-x64-modern`
compile target types
- These targets are supported by the Bun CLI but were missing from the
TypeScript type definitions
## Changes
Added `bun-linux-x64-${SIMD}` to the `CompileTarget` type union, which
expands to:
- `bun-linux-x64-baseline`
- `bun-linux-x64-modern`
## Test plan
- [x] TypeScript should now accept `target: 'bun-linux-x64-modern'`
without type errors
Closes#26247🤖 Generated with [Claude Code](https://claude.com/claude-code)
### What does this PR do?
### How did you verify your code works?
---------
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
## Summary
- Improve handling of fragmented chunk data in the HTTP parser
- Add test coverage for edge cases
## Test plan
- [x] New tests pass
- [x] Existing tests pass
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
### What does this PR do?
fixes https://github.com/oven-sh/bun/issues/26597
### How did you verify your code works?
---------
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
