When to use Lab

Good fit

• Chainable guest JavaScript on the edge with per-step permission sets.
• Receipt-first debugging: you want a persisted document per run with inputs/outputs for inspection and sharing.
• HTTP or agent control planes: HTTP API, MCP / catalog, or both.

Poor fit

• Long-running task queues where jobs churn for minutes or run in the background. Workers CPU limits and the sandbox model are the wrong shape. Try Chomp for agent task queues.
• Full system access (filesystem, raw sockets, shell commands, browser automation). Lab runs in a locked-down sandbox on purpose. Try Cloudshell for terminal access or Filepath for a full dev environment.
• Persistent memory across runs. Lab runs are stateless — each one starts fresh. If agents need to learn from previous runs and recall that knowledge later, use Deja alongside Lab.
• E2E browser testing with assertions against live UI. Lab proves code ran correctly; Gateproof proves the UI works correctly.
• One large trusted monolith with no need for untrusted code or per-step permissions — plain Cloudflare Workers or your existing stack may be simpler.

Relationship to “plain” Workers

Lab orchestrates Loader isolates, capabilities, and receipts. It does not replace Workers; it depends on them. See Architecture for loaders, KV snapshots, spawn, and /invoke/*.