> ## Documentation Index
> Fetch the complete documentation index at: https://arkor-92aeef0e-eng-716.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# arkor dev

> Launch Studio in the browser.

# `arkor dev`

`arkor dev` boots [Studio](/concepts/studio) on `http://localhost:4000`. Studio is the local web UI where you trigger training runs, watch the run stream, and chat with the resulting model in the Playground.

## Run it

<CodeGroup>
  ```bash pnpm theme={null}
  pnpm dev
  ```

  ```bash npm theme={null}
  npm run dev
  ```

  ```bash yarn theme={null}
  yarn dev
  ```

  ```bash bun theme={null}
  bun dev
  ```
</CodeGroup>

Open the URL the CLI prints. Click **Run training** to spawn a training run against `src/arkor/index.ts`. Live metrics stream in; once a checkpoint lands, the Playground lets you chat with it.

`arkor dev` does **not** start a training run on its own. It only serves the UI plus the small loopback API the SPA talks to. Training is triggered from the UI.

## Need a different port?

Pass `--port`:

<CodeGroup>
  ```bash pnpm theme={null}
  pnpm dev --port 5000
  ```

  ```bash npm theme={null}
  npm run dev -- --port 5000
  ```

  ```bash yarn theme={null}
  yarn dev --port 5000
  ```

  ```bash bun theme={null}
  bun dev --port 5000
  ```
</CodeGroup>

Add `--open` to open the browser automatically.

## Reference

For the full flag list, the loopback / CSRF security model, and the troubleshooting catalog (port collisions, anonymous bootstrap, token expiry, 403 reasons), see the [`arkor dev` reference](/cli/dev).