When Anthropic bought the JavaScript runtime Bun in December 2025, the community breathed a sigh of relief. The deal promised open‑source continuity, the same core team, and a roadmap aimed at faster installs, tighter bundling, and Node.js compatibility. Those assurances matched the hopes of developers who rely on Bun’s built‑in TypeScript support and rapid package management every day for teams.

The worry grew when Claude Code, Anthropic’s AI coding assistant that ships as a Bun executable, started degrading. By April 2026 users reported flaky reasoning, surprise billing tied to a stray OpenClaw reference, and slower response times. Anthropic’s post‑mortem admitted product‑layer bugs, marking the first public admission of fault and shaking confidence in the runtime’s stability for developers worldwide.

Facing uncertainty, the author migrated active projects from Bun to pnpm, keeping the install speed and low disk usage while avoiding runtime regressions. pnpm only replaces Node’s package manager, not the entire toolchain, so developers still pull in separate bundlers and test runners. Until Anthropic demonstrates that Bun can stay independent of Claude Code’s missteps, pnpm remains the safer default.