Bun v1.3.10 ships a major set of features and performance improvements. Highlights include a fully rewritten native REPL in Zig, `--compile --target=browser` for self-contained HTML output, TC39 stage-3 ES decorators support, Windows ARM64 support, and barrel import optimization. Performance gains are extensive: structuredClone up to 25x faster for arrays, Buffer.slice() ~1.8x faster, path.parse() up to 7x faster, deep rope string slicing 168x faster via JavaScriptCore upgrade, and fewer closures in bundled output. A critical fix resolves Python asyncio-based MCP servers breaking when spawned via Bun.spawn(). The release also addresses 155 issues including Node.js compatibility fixes, security patches (HTTP header injection, path traversal, SCRAM timing attack), memory leaks, and numerous crash fixes across the bundler, shell, and Windows.
Table of contents
New REPL--compile --target=browser for self-contained HTML outputTC39 Standard ES DecoratorsFaster event loop on macOS & LinuxWindows ARM64 SupportBarrel Import OptimizationFewer closures in bundled output--retry flag for bun testArrayBuffer output for Bun.generateHeapSnapshot("v8")TLS keepalive for custom SSL configs (mTLS)Updated Root CertificatesUpgraded JavaScriptCore EnginestructuredClone is up to 25x faster for arraysstructuredClone is faster for arrays of objectsFaster structuredClone for numeric arraysBuffer.slice() / Buffer.subarray() is ~1.8x fasterpath.parse() is 2.2–7x fasterFixed: Bun.spawn() stdio pipes breaking Python asyncio-based MCP serversBugfixes3 Comments
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