Jarred Sumner. Creator of the Bun JavaScript runtime and software engineer at Anthropic. Sumner built Bun as a fast, all-in-one JavaScript toolkit designed to replace Node.js in development and production environments, writing large portions of it in Zig before a 2026 migration to Rust conducted almost entirely with Claude Code agents. His work sits at the intersection of systems programming and AI-augmented software development, where the constraints are real: a million-line codebase, a 1.386-million-assertion conformance test suite, and a correctness bar set by what a production runtime requires.
Operating themes
- Test-suite-as-ground-truth Sumner's agent workflows treat the conformance test suite as the deterministic arbiter of correctness, allowing neither implementer nor reviewer agents to hallucinate a passing result.
- Adversarial reviewer pairing Runs separate reviewer agent instances against implementer outputs to break shared-blind-spot failure modes, a practice that caught three categories of bugs the implementers missed.
- Scale by decomposition Distributes work across 64 simultaneous agent instances in four worktrees, one per file or error type, to prevent context drift across large codebases.