Declare notifications and post an OS notification banner:
// app.json: { "capabilities": ["notifications"] }
const shown = await window.chatoss.notifications.send({ title: 'Build finished', body: 'All 42 tests passed.' });
// shown === true if dispatched, false if the user denied.
The first send prompts the user once (Allow once / Allow always / Deny); an app the user has marked Trusted in the Apps manager sends without prompting. On macOS the app also needs the system notification permission, which ChatOSS requests the first time.