angular

Create writable signals with signal(), derive values with computed(), and run side effects with effect(). For shared state, build a service exposing private writable signals and public readonly computed values, updating state through explicit action methods.

Use Signals for local component state, derived values, and side effects. Use RxJS for HTTP requests via HttpClient, event streams, and complex async flows requiring operators like switchMap or mergeMap.

Add provideZonelessChangeDetection() to the providers array in bootstrapApplication. Combine it with OnPush change detection and Signals so updates trigger rendering without zone.js patching async APIs.

Yes, Angular v20+ supports incremental hydration using @defer blocks with hydrate triggers like on viewport, on interaction, on idle, or on timer. Enable it with provideClientHydration(withEventReplay()) in the app config.

Signals must be called as functions in templates, like count(), and the component should use OnPush change detection. In zoneless apps, updates must go through signal set or update calls rather than mutating objects directly.

Avoid it for AngularJS 1.x migrations, which need a dedicated migration path, and for legacy apps that cannot upgrade. Gradual migration is recommended over big-bang rewrites for existing codebases.