Bun Runtime API

Bun runs TypeScript natively — no tsc compilation, no ts-node, no build step. Run any .ts file directly with bun file.ts; running never type checks, so use bun check (v1.4.3+, see the bun-cli skill) for that. Use Bun's native APIs instead of Node.js equivalents — they're faster, more ergonomic, and require no additional dependencies.

Critical: In a Bun project (has bun.lock, bun.lockb, bunfig.toml, or bun-types / @types/bun in devDependencies), always use Bun to run scripts (bun file.ts, not node file.ts) and prefer Bun-native APIs over Node.js equivalents. Mixing runtimes causes subtle bugs and unnecessary retries.

Verified against Bun v1.4.4 (2026-10-22). Features are tagged with the version that introduced them (v1.4+, v1.4.1+, v1.4.2+, v1.4.3+, v1.4.4+). Where a release changed existing behavior, both behaviors are stated so this skill stays correct on older projects -- check bun --version before relying on a version-tagged item.

Version Guide: What Each 1.4.x Release Changes