How do OnPush and zoneless change detection change Angular design?

Explains the notification paths Angular relies on and designs components that do not depend on incidental global checks.

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TL;DR

OnPush lets Angular skip a component subtree until a relevant input, event, explicit mark, async-pipe emission, or template-read signal says it may need updating. Zoneless mode removes ZoneJS as the broad scheduler, so components must use Angular-aware notification paths consistently. Signals read in a template work well because updating them marks the owning view for a future check.

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OnPush, zoneless change detection, signals, async pipe, immutable inputs, rendering, and third-party integration.

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Core answer first, then checkpoints toward a stronger answer.

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Core answer
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Overview
Efficient Angular code makes state changes visible through supported notifications instead of relying on ZoneJS to notice arbitrary work.
OnPush lets Angular skip a component subtree until a relevant input, event, explicit mark, async-pipe emission, or template-read signal says it may need updating. Zoneless mode removes ZoneJS as the broad scheduler, so components must use Angular-aware notification paths consistently. Signals read in a template work well because updating them marks the owning view for a future check.
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Stronger answer
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I use immutable input updates, signals, the async pipe, and normal template listeners so state changes have an obvious path to rendering. A stale component often means code mutated an input in place or a third-party callback changed plain fields without notifying Angular. I repair that boundary instead of scattering detectChanges calls. OnPush is recommended preparation for zoneless compatibility, but library components hosting unknown children need additional care.

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Details

Treating OnPush as a guarantee that a component renders only once.
Mutating input objects and expecting reference-based notification.
Calling detectChanges everywhere after enabling zoneless mode.

How do OnPush and zoneless change detection change Angular design?

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