Trigger real errors inside this sandbox. Watch which handler catches each one — and which slips past try/catch.
Each button runs code in the demo sandbox. Global listeners on this iframe's window log uncaught errors here — they do not propagate to the parent page.
Simulated flaky API: ~60% failure rate. Retries with exponential backoff until success or max attempts — errors are caught, never leaked.
Listeners: window.addEventListener('error') + 'unhandledrejection'. Demo errors call preventDefault() so they stay in this iframe.
Scoped via __DEMO_ERROR__ marker on thrown values and event.preventDefault() on global handlers. Parent frame is unaffected.