abpai Bun Runtime Development Guide
This skill is intentionally grounded in official Bun documentation. Bun moves quickly, so prefer current docs over hard-coded release timelines or benchmark claims.
Recent Capability Radar
Bun ships new built-ins constantly. This list covers what landed roughly
between Bun 1.3 (Oct 2025) and Bun 1.3.14 (May 2026) — the kind of thing a
model's training data likely predates. For anything newer, check
https://bun.com/blog before assuming a capability doesn't exist.
Reach for these instead of the dependency you'd otherwise install:
Bun.SQL: one client for Postgres, MySQL/MariaDB, and SQLite — skippg,mysql2, orpostgres.Bun.redis: native Redis/Valkey client — skipioredis/node-redis.Bun.secrets: OS-keychain-backed credential storage — skipkeytar.Bun.YAML.parse/.stringify: built-in YAML — skipjs-yaml/yaml.CompressionStream/DecompressionStreamnow support"brotli"and"zstd"formats, not just gzip/deflate.Bun.stripANSI,URLPattern, andDisposableStack/AsyncDisposableStackare built in — skipstrip-ansiand userland URL-pattern/cleanup helpers.Bun.markdown(.html/.render/.react): built-in CommonMark+GFM parser;bun ./file.mdrenders Markdown in the terminal — skipmarkdown-it/markedfor common cases.- Fake timers landed in
bun:test(useFakeTimers,advanceTimersByTime,setSystemTime,useRealTimers) — skipsinon/@sinonjs/fake-timers. - HTML-entrypoint dev server gained hot module replacement via
import.meta.hot— skip a separate Vite/webpack dev server for simple frontends. bun install --linker=isolatedwithglobalStore = true(orBUN_INSTALL_GLOBAL_STORE=1): still-experimental global virtual store for much faster warm installs.- Still experimental, don't default to these in production:
Bun.WebView(browser automation without Puppeteer/Playwright) and HTTP/3 over QUIC in bothBun.serve({ http3: true })andfetch({ protocol: "h3" }).
Built-in API Map
| Need | Bun API |
|---|---|
| HTTP server + WebSockets | Bun.serve() |
| SQL databases | sql, SQL, Bun.sql, Bun.SQL |
| S3-compatible storage | s3, S3Client |
| Redis | redis, RedisClient |
| Scheduled tasks (cron) | Bun.cron, Bun.cron.parse |
| Image processing | Bun.Image, Blob#image(), Bun.file().image() |
| Browser automation | Bun.WebView |
| Markdown rendering | Bun.markdown.html, Bun.markdown.render, Bun.markdown.react |
| Shell scripting | Bun.$ / $ |
| Local files | Bun.file, Bun.write |
| SQLite (embedded) | bun:sqlite |
| Password hashing | Bun.password |
| PTY-backed subprocesses | Bun.Terminal, Bun.spawn({ terminal }) |
Deep-Dive References
| Reference | Contents |
|---|---|
| references/builtin-apis.md | Bun.serve, HTTP/3, WebSockets, SQL, S3, Redis, Bun.Image, Bun.WebView, Markdown, cron, shell, PTY, filesystem, and crypto APIs |
| references/package-management.md | Installs, lockfiles, isolated linker, global virtual store, catalogs, and lifecycle-script security |
| references/testing-and-bundling.md | bun test usage, suite-splitting flags, mocking patterns, bun build CLI and API |
| references/node-migration.md | Practical Node-to-Bun migration steps and compatibility guidance |