Anthropic Acquires Bun, Boosting AI Coding Infrastructure as Claude Code Hits $1 Billion Revenue Run-Rate
December 3, 2025 — Anthropic, a leading AI research and development lab, has completed the acquisition of Bun, the innovative JavaScript runtime that has become a core component of Anthropic’s AI coding system, Claude Code. This strategic move comes as Claude Code achieves a remarkable milestone, reaching a $1 billion annualized run-rate revenue just six months after its public launch.
Acquisition Details and Strategic Vision
Bun, founded by Jarred Sumner, is a modern JavaScript runtime known for fast performance and integrated bundling, package management, and testing capabilities. Previously a venture-backed startup with a $26 million raise but no revenue, Bun’s acquisition by Anthropic represents a significant transition from a standalone tooling project to a foundational part of an AI-driven software development ecosystem.
According to Sumner, joining Anthropic provides Bun with long-term stability and access to world-class AI research resources, enabling the team to focus on sharpening Bun as the premier platform for building, running, and testing AI-driven software applications. Anthropic plans to use Bun not just as a runtime but as the infrastructure backbone for key AI products including Claude Code, Claude Agent SDK, and future AI coding tools.
Claude Code’s Rapid Revenue Growth
Claude Code, Anthropic’s AI-powered coding assistant, has demonstrated exceptional market traction. First publicly available six months ago, it now supports a run-rate revenue exceeding $1 billion. This means current monthly revenues annualize to over $1 billion. More broadly, Anthropic’s annual revenue run rate escalated from $1 billion in January 2025 to $5 billion by August, then $7 billion by October, underscoring rapid growth fueled in part by Claude Code and associated API services.
A Structural Shift in AI Software Infrastructure
Industry analysts note that Anthropic’s acquisition of Bun marks a historic moment where a general-purpose language runtime is directly integrated into the engineering infrastructure of a leading large AI model company. Previously, large AI firms have acquired IDEs and plugins, but this is the first known example of a runtime like Bun becoming a central piece of a unified AI software development pipeline.
This integration reflects a paradigm shift: AI models now generate code that is built, run, and tested continuously within a runtime environment deeply coupled with the model’s logic. This sets the stage for a new era of “AI-native runtimes,” where the runtime semantics and tooling are co-designed to enhance AI programming efficiency, reliability, and scalability.
Looking Ahead
Anthropic’s commitment to Bun signals a long-term bet on evolving the JavaScript runtime into a best-in-class environment that serves broad software development needs while pioneering future AI coding paradigms. The acquisition also strengthens Anthropic’s competitive advantage in AI developer tools, enabling tighter integration between the Claude AI models and their supporting runtime infrastructure.
With Bun’s team now fully integrated but retaining operational independence similar to the relationship between browsers and their JavaScript engines (e.g., Google Chrome & V8), developers can expect rapid innovation in performance, tooling, and AI-assisted coding workflows fueled by this synergy.
As AI continues to reshape software development, Anthropic’s acquisition of Bun exemplifies how foundational engineering layers are being reinvented to support intelligent, automated programming at unprecedented scale.