AlabJS runs on Bun with no code changes — Bun is Node.js-compatible and the H3 server works as-is. You get faster cold starts, lower memory usage, and a built-in .env loader.

Requirements

• Bun ≥ 1.1
• Node.js ≥ 22 is not required when running on Bun

Build

Build is still done with the alab CLI (which uses Vite under the hood):

bunx alab build

Or via your package.json scripts:

bun run build

Start

bunx alab start
# or
PORT=3000 bun run .alabjs/dist/cli.js start

Bun reads .env files automatically — no dotenv package needed.

Environment variables

Bun loads .env, .env.local, .env.production automatically at startup. You can also pass variables inline:

PORT=8080 DATABASE_URL=postgres://... bunx alab start

Docker with Bun

FROM oven/bun:1-alpine
WORKDIR /app

COPY package.json bun.lockb ./
RUN bun install --frozen-lockfile --production

COPY . .
RUN bun run build

EXPOSE 3000
CMD ["bun", "run", ".alabjs/dist/cli.js", "start"]

The oven/bun image is ~95 MB — roughly half the size of the equivalent node:22-alpine image.

PM2 with Bun

pm2 start "bun run .alabjs/dist/cli.js start" --name my-alabjs-app --interpreter none
pm2 save

Performance notes

	Node.js 22	Bun 1.x
Cold start	~180 ms	~40 ms
Memory (idle)	~60 MB	~30 MB
HTTP throughput	Baseline	~1.5× faster

Cold start improvement is most noticeable on serverless-style deployments where the process restarts frequently.

Limitations

• The Rust @alabjs/compiler napi binary runs fine on Bun — napi-rs supports Bun since v1.0.
• Image optimization (/_alabjs/image) works normally on Bun.
• All AlabJS features are fully supported.