The infrastructure layer just became the new battleground for AI coding tools.
Yesterday, Anthropic announced it has acquired Bun—the JavaScript runtime, bundler, and package manager that's been steadily gaining traction as a Node.js alternative. This isn't a typical acqui-hire or talent grab. Anthropic is betting on Bun as core infrastructure for Claude Code, Claude Agent SDK, and future AI coding products.
For mid-career developers watching the AI tooling space evolve, this acquisition marks a significant shift in how AI companies think about their technical stack—and what that means for the tools we choose.
Why Bun? Why Now?
The acquisition makes immediate practical sense when you understand the distribution problem AI coding tools face.
Claude Code ships as a Bun single-file executable. This compilation feature lets you package any JavaScript project into a self-contained binary that runs anywhere—no runtime installation required, native addon support included, fast startup guaranteed. For a CLI tool that needs to work across developer environments without friction, this solves a real deployment headache.
But the deeper story is about alignment between where JavaScript tooling is headed and where AI-assisted development is going.
Jarred Sumner, Bun's creator, shared a revealing detail in the announcement: over the last several months, the GitHub username with the most merged PRs in Bun's repository is a Claude Code bot. They've set it up in their internal Discord to help fix bugs—opening PRs with failing tests, responding to review comments, handling the full contribution workflow.
This isn't a future scenario. It's current practice at the company that built the runtime.