# Sandbox Providers

Blekline is **Layer 4** — mask, enforce, and audit MCP tool calls. These providers are **Layer 1** — isolated runtimes where agents execute code. Wire any of them through `@blekline/mcp-proxy` using `BLEKLINE_DOWNSTREAM_MCP_COMMAND`.

## Comparison

| Provider | Best for | MCP / wiring | GPU | Edge / global |
|----------|----------|--------------|-----|---------------|
| [Daytona](/docs/integrations/daytona-stack) | Dev/agent workspaces, fast startup | `@daytona/mcp-server` | — | Multi-region |
| [Modal](/docs/integrations/modal-stack) | Serverless sandboxes, ML/GPU workloads | Community MCP servers | Yes | Cloud |
| [Vercel Sandbox](/docs/integrations/vercel-sandbox-stack) | Next.js / Vercel stack, Firecracker microVMs | `@vercel/sandbox` SDK + optional MCP | — | Vercel network |
| [Cloudflare](/docs/integrations/cloudflare-stack) | Edge agents, Containers + Sandbox SDK | Sandbox SDK, Container MCP | — | Global edge |
| [E2B](/docs/integrations/e2b-stack) | Firecracker microVMs, Fortune-500 scale | `@e2b/mcp-server` / E2B MCP | — | Cloud |

## Universal proxy env

```bash
BLEKLINE_WORKSPACE_TOKEN=blw_...
BLEKLINE_DOWNSTREAM_MCP_COMMAND=npx,-y,@daytona/mcp-server   # provider-specific
BLEKLINE_DOWNSTREAM_SERVER=daytona                           # telemetry label
```

Set `BLEKLINE_MCP_PROXY_MOCK=1` for local dev without provider API keys.

## Smoke tests

From [blekline-oss](https://github.com/Blekline/blekline-oss):

```bash
SANDBOX_PROVIDER=daytona pnpm demo:sandbox-smoke
SANDBOX_PROVIDER=e2b pnpm demo:sandbox-smoke
# modal, vercel, cloudflare — see demo/README.md
```

## When to pick which

- **Daytona** — default for coding agents, MCP-native, sub-90ms sandboxes, strong dev UX.
- **Modal** — GPU inference, Python-heavy agents, 50k+ concurrent sandboxes.
- **Vercel Sandbox** — already on Vercel; AI-generated code in isolated microVMs alongside Next.js apps.
- **Cloudflare** — edge-first agents, Workers + Containers, Code Mode MCP pattern.
- **E2B** — mature Firecracker isolation, broad enterprise adoption.

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**Next steps:** [AI Enablement Stack](/docs/introduction/ai-enablement-stack) · [MCP proxy](/docs/mcp/proxy) · [Quick start](/docs/introduction/quick-start) · [Open workspace](https://app.blekline.com)