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

# Overview

> Secure, isolated environments where coding agents execute sessions.

Every session runs in its own isolated sandbox. Sandboxes are ephemeral: spun up for the session, destroyed when it's done. No code or state persists after execution.

## Data handling

Your repository is cloned into the sandbox for the duration of a session and torn down when the session ends — no repository contents or working state persist afterward.

The one exception is snapshots. If you use the snapshot feature to speed up environment setup, your repository and pre-installed dependencies are cached into a reusable snapshot image so future sessions start faster. That cached copy persists until the snapshot is rebuilt or removed.

Model providers handle prompt data according to their own retention policies — see the retention table in [Max](/features/max) for Tembo-hosted models. With [BYOK](/features/models), model requests run against your own provider account, so provider-side retention follows that account's terms.

## Sandbox sizes

Tembo offers five sandbox sizes. Each session runs in a dedicated Linux VM, and no two sessions share the same VM.

| Size   | vCPU | Memory | Disk   |
| ------ | ---- | ------ | ------ |
| Micro  | 2    | 4 GB   | 50 GB  |
| Medium | 4    | 8 GB   | 50 GB  |
| Large  | 8    | 32 GB  | 100 GB |
| XL     | 16   | 64 GB  | 200 GB |
| Ultra  | 32   | 128 GB | 200 GB |

Micro and Medium are best for routine code analysis, fixes, features, and reviews. Large, XL, and Ultra are best for heavier builds, integration tests, Docker workloads, large repositories, or multi-container setups.

VM sandboxes include full nested virtualization for Docker-in-Docker and provide a stronger isolation boundary.

If your org requires that untrusted code only runs with a VM boundary, we can enforce a VM-only posture. Contact [support@tembo.io](mailto:support@tembo.io).

## Pre-installed tools

All sandbox sizes come with:

| Category       | Tools                          |
| -------------- | ------------------------------ |
| **JavaScript** | Node.js 22, Bun, pnpm, Yarn    |
| **Python**     | Python 3.12, pipx, uv, ruff    |
| **Ruby**       | Ruby 3.3, Bundler, RuboCop     |
| **.NET**       | .NET SDK 9                     |
| **Cloud**      | Google Cloud SDK               |
| **Containers** | Docker 28, Docker Compose 2.31 |
| **Other**      | Git, curl, ShellCheck, httpie  |

<Note>Go, Rust, Java, and Elixir are available through Nix dev shells. Add a `tembo.nix` to install language-specific tooling for your project.</Note>

## Add custom dependencies

Add a [`tembo.nix`](/features/sandbox/custom-dependencies) file to your repository when your project needs tools that are not pre-installed in the sandbox.