Anthropic acquires Bun as Claude Code passes $1 billion run-rate

Anthropic announced it had acquired Bun, the team behind the open-source JavaScript runtime founded by Jarred Sumner in 2021, to work on infrastructure underpinning Claude Code. Anthropic said Bun would remain open source and MIT-licensed.

Bun functions as an all-in-one runtime, package manager, bundler and test runner, and had reached about 7 million monthly downloads and more than 82,000 GitHub stars. Anthropic said the tool had already been “key” to scaling Claude Code’s infrastructure, and that the acquisition would let the combined team build on that momentum to deliver faster performance, improved stability and new capabilities. Deal terms and the size of the Bun team joining Anthropic were not disclosed.

Alongside the acquisition, Anthropic reported that Claude Code, its coding-agent product, had passed $1 billion in annualised run-rate revenue as of November 2025 — roughly six months after its general release in May — with adopters including Netflix, Spotify, KPMG, L’Oréal and Salesforce.

Acquiring the maintaining team of a widely used open-source project is an unusual move for a foundation-model company, most of which build or license developer tooling rather than acquire it outright. Taken together with Claude Code’s reported revenue and Anthropic’s expanded partnership with Snowflake announced the following day, the announcement underlined how coding-agent and enterprise-agent revenue, rather than chat subscriptions alone, had become a fast-growing line of Anthropic’s business.