> ## Documentation Index
> Fetch the complete documentation index at: https://docs.celesto.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Coding Agents in Sandbox

> Run Claude Code, Codex, Hermes, and Pi coding agents inside a SmolVM sandbox with full permissions — no accept-changes prompts and no host risk.

SmolVM lets you run coding agents like Claude, Codex, Hermes, and Pi inside an isolated sandbox. The agent gets a full development environment — git credentials, dev tools, terminal access — but nothing it does can affect your host machine.

No more pressing "accept changes" every few seconds. Let the agent work freely in its own computer.

<Tip>
  Want to keep Pi and its model credentials on your machine while its coding tools run in the cloud? Follow [Run Pi coding agent in the cloud](/celesto-sdk/guides/pi-coding-agent).
</Tip>

## Start a coding agent

<Tabs>
  <Tab title="Claude">
    ```bash theme={null}
    smolvm claude start
    ```
  </Tab>

  <Tab title="Codex">
    ```bash theme={null}
    smolvm codex start
    ```
  </Tab>

  <Tab title="Hermes">
    ```bash theme={null}
    smolvm hermes start
    ```
  </Tab>

  <Tab title="Pi">
    ```bash theme={null}
    smolvm pi start
    ```
  </Tab>
</Tabs>

Each command launches a sandbox with the respective coding agent pre-installed and configured. Your existing credentials (from `claude login`, `codex login`, etc.) are forwarded into the sandbox automatically — no re-authentication needed.

The first launch typically takes 5–10 seconds because SmolVM downloads a pre-built sandbox image instead of installing the agent on every run. See [Published images](/smolvm/concepts/published-images) for how the fast path works and how to opt out.

## What you get

Each coding agent sandbox comes with:

* **Isolated environment** — the agent runs in its own VM, separate from your host
* **Git credentials** — pre-configured so the agent can clone, commit, and push
* **Dev tools** — common development tooling ready to use
* **Terminal access** — full shell access for multi-step workflows

## Share folders with the sandbox

You can share folders from your machine so the coding agent can see your existing code. By default, shared folders are read-only — the agent can read your files but cannot modify the originals.

```bash theme={null}
smolvm claude start --mount ~/Projects/my-app
```

The agent sees your project files inside the sandbox at `/workspace`.

To let the agent write changes back to your machine, add `--writable-mounts`:

```bash theme={null}
smolvm claude start --mount ~/Projects/my-app --writable-mounts
```

<Warning>
  With `--writable-mounts`, the agent can modify and delete files in the shared folder. Only enable this when you trust the code the agent will run.
</Warning>

<Tip>
  See the [host mounts guide](/smolvm/features/host-mounts) for more options like sharing multiple folders and custom mount paths.
</Tip>