> ## Documentation Index
> Fetch the complete documentation index at: https://arkor-92aeef0e-eng-615.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# arkor build / start

> Run a trainer without booting Studio.

# `arkor build` and `arkor start`

`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>
  ```bash pnpm theme={null}
  pnpm build
  pnpm start
  ```

  ```bash npm theme={null}
  npm run build
  npm start
  ```

  ```bash yarn theme={null}
  yarn build
  yarn start
  ```

  ```bash bun theme={null}
  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>
  ```bash pnpm theme={null}
  pnpm start src/arkor/experiment.ts
  ```

  ```bash npm theme={null}
  npm start -- src/arkor/experiment.ts
  ```

  ```bash yarn theme={null}
  yarn start src/arkor/experiment.ts
  ```

  ```bash bun theme={null}
  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](/cli/build-and-start).