By Jarred Sumner · December 2, 2025
Bun has officially been acquired by Anthropic. This partnership marks a significant moment for both the JavaScript ecosystem and the rapidly evolving world of AI-powered software development. Anthropic is betting on Bun to become the infrastructure layer behind Claude Code, the Claude Agent SDK, and a new generation of AI coding tools.
The heart of this announcement is simple: Bun stays open-source, remains MIT-licensed, continues to be built in public, and the same team keeps building it—just with far more resources and a much bigger mission.
Below is a breakdown of what changes, what does not, and why this acquisition makes strategic sense for the future of software development.
What Stays the Same
Bun remains open-source and MIT-licensed
No licensing shifts. No paywalls. No closed-source pivot.
Bun continues to be actively maintained
Development velocity stays high. The same engineers, same core contributors.
The Bun team stays intact
Everyone working on Bun continues full-time—now with the backing of one of the world’s leading AI labs.
Bun stays public on GitHub
Issues, PRs, discussions, commits—everything remains transparent.
The roadmap remains focused
Bun will continue improving:
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High-performance JavaScript and TypeScript tooling
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Node.js compatibility
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Becoming the default server-side runtime for JavaScript
Claude Code depends directly on Bun
Claude Code ships as a Bun executable to millions of users. If Bun breaks, Claude Code breaks—so Anthropic is fully aligned in keeping Bun robust, fast, and reliable.
What Changes
1. Bun becomes the backbone of AI coding tools
Bun will power and accelerate:
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Claude Code
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Claude Agent SDK
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Future Anthropic developer tools
2. Bun improves faster than ever
With more engineers, deep AI integration, and direct feedback loops from Anthropic’s internal usage.
3. Bun’s infrastructure becomes fundamental to AI-generated software
Anthropic is betting big on fast, lightweight runtimes that AI agents can use to write, test, debug, and ship code autonomously.
How Bun Started
Nearly five years ago, Bun began as a side-quest while building a voxel-based browser game. Development iterations took 45 seconds due to slow JavaScript tooling, which pushed Jarred to rewrite parts of esbuild’s JSX/TS transpiler in Zig.
That experiment quickly grew into:
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A transpiler
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A bundler
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A runtime
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A test runner
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A package manager
All delivered as a single, ultra-performant tool.
By July 2022, Bun v0.1 launched and reached 20,000 GitHub stars in its first week, followed by a $7M seed round that helped assemble the founding team.
Bun’s Road to 1.x
v1.0 (September 2023)
Stable. Production-ready. Gained significant adoption.
v1.1
Introduced long-awaited Windows support.
v1.2
Major Node.js compatibility improvements and added:
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A PostgreSQL client
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An S3 client
Companies like X and Midjourney began using Bun in production.
v1.3
Introduced:
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A built-in frontend dev server
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Redis client
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MySQL client
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Improved
bun install -
Better Node.js compatibility
This version marked major growth in real-world enterprise usage.
The Turning Point: AI Gets Really Good
By late 2024, AI coding tools went from experimental to indispensable—and many of them were built with Bun. Its ability to compile JavaScript projects into a single self-contained executable made it ideal for distributing AI CLIs and agents. No runtime install required. Fast startup. Works everywhere.
Tools built with Bun included:
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Claude Code
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FactoryAI
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OpenCode
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Many others
Bun became the natural foundation for AI-native developer tooling.
Claude Code’s Impact
Internally, Anthropic’s Claude Code contributed more PRs to Bun than any other source. It fixed bugs, wrote tests, responded to reviews, and validated builds.
This was a preview of where AI coding is heading—fast.
The Sustainability Question
Despite massive growth—7.2 million monthly downloads and 25% month-over-month growth—Bun made $0 in revenue. With four years of runway, monetization wasn’t urgent, but long-term sustainability still mattered.
User questions were becoming louder:
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“Will Bun still be around in 10 years?”
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“Is Bun safe to bet my company’s tech stack on?”
A cloud hosting product was the original plan, but the world had changed. AI coding tools reshaped developer workflows and made the runtime layer more critical than ever.
Building a business on the old model felt misaligned with where software engineering was going.
The Walk That Changed Everything
Several long walks and deep conversations with the Claude Code team—and even Anthropic’s competitors—made one thing clear:
Anthropic has the best chance of defining the future of AI-assisted software development.
Bun could either:
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Build tooling from the outside, guessing where AI coding is heading
or -
Join Anthropic and shape that future from the inside
The choice became obvious.
Why Joining Anthropic Makes Sense
1. Long-Term Stability
Companies can trust Bun as a foundation for the next decade.
2. Direct Influence on the Future of AI Coding
Bun becomes the runtime aligned with the workflows AI agents will use to write, test, optimize, and deploy software.
3. Resources to Scale
More engineers, deeper integration, and the ability to ship faster.
4. No Distraction From Monetization
Anthropic frees Bun from the typical VC pressure to convert users into revenue.
The Road Ahead
Bun will become the best environment for building, running, and testing AI-driven software, while still excelling as a general-purpose JavaScript runtime.
Anthropic gets:
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A runtime perfectly aligned with AI coding workflows
Bun gets:
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Stability
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Resources
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A seat at the center of the next major evolution in software engineering
This partnership unlocks a future where:
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Code is written at machine speed
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AI agents manage entire development workflows
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The runtime is optimized for speed, consistency, predictability, and portability
Bun will be that runtime.
FAQs
Is Bun still open-source & MIT-licensed?
Yes.
Is Bun still developed publicly on GitHub?
Yes.
Does Bun still care about Node.js compatibility?
Yes. That mission continues.
Is the same team continuing full-time?
Yes—now with Anthropic’s resources behind them.
What does this mean for the roadmap?
Expect tighter integration with Claude Code and the Claude Agent SDK, similar to how:
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Chrome works with V8
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Safari works with JavaScriptCore
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Firefox works with SpiderMonkey
But with independence to continue serving the broader JavaScript community.
Conclusion
Bun’s mission has always been to make developers faster. AI coding tools share that mission—but on an even larger scale. Joining Anthropic brings Bun into the core of this transformation, helping shape the future of how software is written.
The next chapter of Bun is not just about being fast JavaScript tooling—it’s about being the infrastructure that powers AI-native development.
And it’s going to be fun.
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