# Capability boundaries & deal-breakers established

Learner finished lesson 4 (and earlier read the MDN APIs-available-to-workers inventory). Treat as known: no DOM in workers; fetch/IDB-class APIs often OK; bundler/origin/lifecycle/protocol risks; when not to worker; service worker as wrong tool for offline. Next ZPD: SharedWorker on the multi-context design map vs dedicated vs BroadcastChannel, then a closing decision playbook.