# Bun (/docs/runtimes/bun)

Bun imports `.toml`, `.yaml` and a few other formats natively, without layering or placeholders. Preloading `tyfigo/bun`
registers a Bun plugin that takes over `*.config.*` files and the files of a
[`.config` directory](/docs/config-files#a-config-directory), and leaves every other `.yaml` or `.toml` file to Bun:

```toml title="bunfig.toml"
preload = ["tyfigo/bun"]

[test]
preload = ["tyfigo/bun"]
```

```toml title="config/app.config.toml"
name = "tyfigo-bun-example"
log_level = "debug"

[server]
port = "${PORT:-3000}"
idle_timeout = 10

[redis]
url = "${REDIS_URL}"
ttl = 60
```

```ts title="src/main.ts"
import config from '../config/app.config.toml';

const listen: { port: number; idleTimeout: number } = {
	port: config.server.port,
	idleTimeout: config.server.idle_timeout,
};
```

For types, use `"types": ["bun"]` and `"skipLibCheck": true` alongside `contentMappers` in `tsconfig.json`, and type-check with
`tsc --noEmit --runExternalCode`.

## Bun.build [#bunbuild]

Pass the plugin to `Bun.build`:

```ts title="build.ts"
import { tyfigo } from 'tyfigo/bun';

await Bun.build({
	entrypoints: ['src/main.ts'],
	outdir: 'dist',
	target: 'bun',
	plugins: [tyfigo()],
});
```

A `browser` target inlines the base and environment files ([Browser builds](/docs/browser-builds)). Other targets inline the
layer files of every environment, pick them by `NODE_ENV` and read `.env` files and environment variables when the bundle runs
([Server bundles](/docs/browser-builds#server-bundles)). `tyfigo({ environment: 'production' })` fixes the environment.

Bun loads `.env` files into `process.env` on its own; tyfigo reads them itself either way and never writes `process.env`.
See the [bun example](https://github.com/imranbarbhuiya/tyfigo/tree/main/examples/bun).