---
title: "Bun v1.3.9"
url: https://daily.dev/posts/bun-v1-3-9-s5ryyjjxd
source_url: https://bun.com/blog/bun-v1.3.9
type: article
source: "Bun"
published: 2026-02-08T09:19:56.986Z
updated: 2026-02-08T09:20:19.685Z
tags: ["javascript", "performance", "testing", "nodejs", "bun"]
reading_time: 9
upvotes: 67
comments: 0
language: en
---

> ## Documentation Index
> Fetch the complete documentation index at: https://daily.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Bun v1.3.9

**[Bun](https://daily.dev/sources/bun)** · 9 min read · 67 upvotes · 0 comments

## Summary

Bun v1.3.9 introduces parallel and sequential script execution with `--parallel` and `--sequential` flags, supporting workspace filtering and Foreman-style output. Testing improvements include `Symbol.dispose` support for automatic mock cleanup. Performance enhancements include SIMD-accelerated RegExp matching, faster string operations (trim, startsWith), optimized Markdown rendering, and ESM bytecode compilation support. HTTP/2 connection upgrades via net.Server now work correctly. Bug fixes address ARM64 crashes, Windows filesystem operations, WebSocket stability, and HTTP proxy keep-alive issues.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://bun.com/blog/bun-v1.3.9>

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---

Tags: [#javascript](https://daily.dev/tags/javascript), [#performance](https://daily.dev/tags/performance), [#testing](https://daily.dev/tags/testing), [#nodejs](https://daily.dev/tags/nodejs), [#bun](https://daily.dev/tags/bun)

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