Bun v1.3.10 introduces a host of new features and substantial performance enhancements aimed at improving user experience and expanding compatibility. This release includes a fully rewritten native REPL implemented in Zig, which enhances JavaScript and TypeScript interactions with the command <code>bun repl</code>. Moreover, it introduces a new compilation feature, <code>--compile --target=browser</code>, that enables users to produce self-contained HTML outputs. Enhanced support for ECMAScript features is highlighted by the introduction of TC39 stage-3 ES decorators.
Windows ARM64 support marks a significant compatibility milestone, broadening Bun’s accessibility across different environments. Additionally, the update boasts barrel import optimization, reducing the complexity and improving efficiency of module imports.
Performance improvements are a significant focus of this release. Users can expect up to 25 times faster performance for <code>structuredClone</code> on arrays, approximately 1.8 times faster execution of <code>Buffer.slice()</code>, and up to 7 times enhanced speed with <code>path.parse()</code>. String slicing operations have seen substantial acceleration, with deep rope string slicing now 168 times faster, thanks to an upgrade incorporating JavaScriptCore. In terms of the bundling process, fewer closures are produced, contributing to streamlined and efficient output processing.
Alongside these enhancements, Bun v1.3.10 extensively addresses issues from previous versions, with 155 resolved fixes. This includes critical Node.js compatibility fixes and crucial security patches, specifically targeting HTTP header injection vulnerabilities, path traversal risks, and timing attacks in the SCRAM protocol. Additionally, it tackles memory leaks and resolves numerous crashes across various components like the bundler, shell, and Windows platform.
A noteworthy fix addresses the instability caused in Python’s asyncio-based MCP servers when they were spawned via Bun.spawn(). With this release, Bun continues to solidify its position as a robust, high-performance tool in the development ecosystem.

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Bun v1.3.10 ships with a fully rewritten native REPL in Zig, a new `--compile --target=browser` flag for self-contained HTML outputs, TC39 stage-3 ES decorators support, and Windows ARM64 compatibility. Performance highlights include up to 25x faster `structuredClone` on arrays, 168x faster deep rope string slicing via a JavaScriptCore upgrade, and 7x faster `path.parse()`. The release also resolves 155 bugs including Node.js compatibility fixes, security patches for HTTP header injection, path traversal, and SCRAM timing attacks, plus memory leaks and crash fixes across the bundler, shell, and Windows platform.

Bun v1.3.10 Release: New Features and Performance Improvements