---
title: "arkor build / start"
description: "Run a trainer without booting Studio."
---

`arkor build` bundles your project to a single ESM artifact. `arkor start` runs it. Together they are the headless equivalent of clicking **Run training** in Studio: use them in CI, on a server, or from any script that needs to drive a trainer without the UI.

## Run it

<CodeGroup labels={["pnpm","npm","yarn","bun"]}>

```bash
pnpm build
pnpm start
```

```bash
npm run build
npm start
```

```bash
yarn build
yarn start
```

```bash
bun run build
bun start
```

</CodeGroup>

`arkor build` writes `.arkor/build/index.mjs` from `src/arkor/index.ts`. `arkor start` imports that bundle, finds your trainer, and runs `start()` + `wait()` (the same pair Studio's button calls).

If you skip the explicit `build` step, `arkor start` auto-builds on first run. From a script you usually want both steps so a build failure surfaces before training spins up.

## Run a different entry once

<CodeGroup labels={["pnpm","npm","yarn","bun"]}>

```bash
pnpm start src/arkor/experiment.ts
```

```bash
npm start -- src/arkor/experiment.ts
```

```bash
yarn start src/arkor/experiment.ts
```

```bash
bun start src/arkor/experiment.ts
```

</CodeGroup>

Passing an entry to `arkor start` rebuilds with that entry first, then runs.

## Reference

For the full argument matrix, the auto-build-on-missing rules, the export shapes the runner accepts, and every error message, see the [`arkor build` / `arkor start` reference](/docs/framework/cli/build-and-start).