Cloudflare Sandbox SDK vs Together Code Sandbox

Cloudflare Sandbox SDK

Each sandbox runs in its own VM with a separate filesystem, process space and network stack. No hosted API. You deploy and secure a Worker before an agent can call anything, and the starter has no auth.

Together Code Sandbox

Two public OpenAPI documents, MIT clients for Python and TypeScript, cursor pagination and built-in retries make the surface easy for an agent to drive. Access is the limit. Together enables the SDK per organisation on request, publishes no rate limits or SLA, and neither status page names the sandbox service.

Cloudflare Sandbox SDK

1. Derive the sandbox ID from the authenticated user, as the docs advise. IDs aren't secrets
2. Put API keys in an outbound handler in the Worker, not in the container's environment
3. Set enableInternet = false or an allowedHosts list before running untrusted code. Internet access is on by default
4. Check that a restored backup has every directory you expect. Backups of 10 MB or more have open bugs
5. Start new projects on 1.0. The 0.x library only gets fixes until 31 December 2026

Together Code Sandbox

1. Confirm the organisation is on Together's allowlist before installing. A valid TOGETHER_API_KEY alone is not enough
2. Build a snapshot first with snapshots.create. No default image exists, and every sandbox needs snapshot_id or snapshot_alias
3. Set ttl at creation or call terminate(). Nothing stops a sandbox otherwise, and closing the Python client leaves it running
4. Store the snapshot alias, not the sandbox ID. A terminated sandbox can't restart, and its state lives at sandbox:<id>
5. Exclude snapshots.create from retries with should_retry, and set experimental.network_policy before serving anything private on a port