---
name: React State Management
description: Standards for managing local, global, and server state.
metadata:
  labels: [react, state, redux, zustand, context]
  triggers:
    files: ['**/*.tsx', '**/*.jsx']
    keywords: [state, useReducer, context, store, props]
---

# React State Management

## **Priority: P0 (CRITICAL)**

Choosing the right tool for state scope.

## Implementation Guidelines

- **Local**: `useState`. `useReducer` if complex (state machine).
- **Derived**: `const fullName = first + last`. No state sync.
- **Context**: DI, Theming, Auth. Not for high-freq data.
- **Global**: Zustand/Redux for app-wide complex flow.
- **Server Cache**: Use `React.cache` (RSC) to dedupe requests per render.
- **Server State**: React Query / SWR / Apollo. Cache != UI State.
- **URL**: Store filter/sort params in URL (Source of Truth).
- **Immutability**: Never mutate. Use spread or Immer.

## Anti-Patterns

- **No Prop Drilling > 2**: Use Context/Composition.
- **No Mirroring Refs**: Don't copy props to state.
- **No Multi-Source**: Single Source of Truth.
- **No Context Abuse**: Context causes full-tree re-render.

## Reference & Examples

For Zustand, Redux Toolkit, and TanStack Query patterns:
See [references/REFERENCE.md](references/REFERENCE.md).

## Related Topics

hooks | component-patterns | performance