Bun Runtime

Bun replaces Node.js, npm/yarn/pnpm, esbuild, and Jest with a single binary — delivering 3-10x faster package installation, native TypeScript execution (no transpile step), and significantly higher HTTP server throughput vs. Node.js. Built-in APIs eliminate common runtime dependencies: Bun.sqlite for SQLite without better-sqlite3, Bun.serve for HTTP/WebSocket without Express, $`shell command` for shell operations without child_process. For agents deploying TypeScript services: Bun's official Docker images enable drop-in replacement of Node.js in container-based deployments. Package manager (bun install) is a direct drop-in for npm/yarn with 10-100x speed improvements. Compatible with most npm packages (Node.js API compatibility is high but not 100%). Confidence is docs-derived.

Runtime APIs: Bun.serve({port: 3000, fetch(req) { return new Response("hi") }}) starts HTTP server. Bun.file(path) reads files lazily. await Bun.write(path, content) writes files. const db = new Database("mydb.sqlite"); db.query("SELECT * FROM users").all() — built-in SQLite. $`git status` — shell templating. Bun.password.hash/verify for bcrypt/argon2. Bun.randomUUIDv4() — fast UUID. Bun.env.MY_VAR — environment variables. WebSocket: Bun.serve({websocket: {message, open, close}}). package.json scripts: bun run script-name. bun build: bundler (esm, cjs, iife output). bun test: built-in test runner (Jest-compatible API).

No Bun-specific authentication — Bun is a runtime, not a hosted service. Authentication in Bun apps: implemented in application code (same patterns as Node.js: JWT, sessions, API keys). Bun.serve supports HTTPS natively with TLS key/cert files: Bun.serve({tls: {key: file, cert: file}, ...}). No external auth service dependency. Secret management: standard env var pattern (process.env / Bun.env).

Bun is production-stable (v1.x+). Node.js compatibility: 99%+ of npm packages work; rare incompatibilities with native addons (node-gyp compiled modules). Error messages: standard JavaScript exceptions with stack traces. Crash recovery: use PM2, systemd, or Docker restart policies — Bun has no built-in process management. Memory usage: typically lower than Node.js for equivalent workloads. SQLite: uses system SQLite or Bun-bundled SQLite; concurrent write limit (WAL mode recommended). Bun.serve: handles thousands of concurrent connections. Bun stability: v1.x LTS track. Updates tracked at bun.sh/releases.

bun.sh/docs is excellent — comprehensive API reference, guides for HTTP servers, SQLite, WebSocket, bundler, test runner, and package manager. Getting started: curl -fsSL https://bun.sh/install | bash — installed in 10 seconds. First HTTP server in 3 lines of TypeScript. Official Docker images (oven/bun) for containerized deployment. Bun Discord community (50k+ members) is very active. GitHub (oven-sh/bun, 73k+ stars) for bug reports and feature requests. Bun blog covers performance benchmarks and release notes. Bun team is responsive to community feedback.