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ADR 002: Standalone Angular Components Only

Status: Accepted
Date: 2026-05-23

Context​

Angular has transitioned fully to standalone components as the default pattern (v19+, reinforced in v21). Synapse UI is a greenfield library targeting the latest stable Angular (21.x).

We must decide whether to ship components as standalone or wrap them in NgModule for backward compatibility with older Angular apps.

Decision​

All Synapse UI components will be standalone only. No NgModule wrappers will be provided or maintained.

Every component will use:

  • standalone: true
  • ChangeDetectionStrategy.OnPush
  • Signal-based input() and output() APIs

Consequences​

Positive​

  • Aligns with Angular's current and future direction.
  • Simpler consumer imports: imports: [AiPromptBarComponent].
  • Better tree-shaking — no module indirection.
  • Cleaner Storybook setup (no wrapper modules).

Negative​

  • Consumers on Angular 14–17 must upgrade to use the library (acceptable — we target latest).
  • No barrel SynapseUiModule for one-line import of all components (by design — tree-shaking priority).

Alternatives Considered​

AlternativeWhy rejected
NgModule + standalone dual exportDoubles maintenance; modules are deprecated path
NgModule onlyAgainst Angular direction; worse DX for modern apps
Minimum Angular 17Still behind current; no compelling reason to support older