SKILL.md
Zustand State Management
Last Updated: 2026-01-21
Latest Version: zustand@5.0.10 (released 2026-01-12)
Dependencies: React 18-19, TypeScript 5+
Quick Start
npm install zustandTypeScript Store (CRITICAL: use create<T>()() double parentheses):
import { create } from 'zustand'interface BearStore {
bears: number
increase: (by: number) => void
}
const useBearStore = create()((set) => ({
bears: 0,
increase: (by) => set((state) => ({ bears: state.bears + by })),
}))
**Use in Components**:
const bears = useBearStore((state) => state.bears) // Only re-renders when bears changes
const increase = useBearStore((state) => state.increase)
## Core Patterns
**Basic Store** (JavaScript):
const useStore = create((set) => ({
count: 0,
increment: () => set((state) => ({ count: state.count + 1 })),
}))
**TypeScript Store** (Recommended):
interface CounterStore { count: number; increment: () => void }
const useStore = create<CounterStore>()((set) => ({
count: 0,
increment: () => set((state) => ({ count: state.count + 1 })),
}))
**Persistent Store** (survives page reloads):
import { persist, createJSONStorage } from 'zustand/middleware'
const useStore = create<UserPreferences>()(
persist(
(set) => ({ theme: 'system', setTheme: (theme) => set({ theme }) }),
{ name: 'user-preferences', storage: createJSONStorage(() => localStorage) },
),
)
## Critical Rules
### Always Do
✅ Use `create<T>()()` (double parentheses) in TypeScript for middleware compatibility
✅ Define separate interfaces for state and actions
✅ Use selector functions to extract specific state slices
✅ Use `set` with updater functions for derived state: `set((state) => ({ count: state.count + 1 }))`
✅ Use unique names for persist middleware storage keys
✅ Handle Next.js hydration with `hasHydrated` flag pattern
✅ Use `useShallow` hook for selecting multiple values
✅ Keep actions pure (no side effects except state updates)
### Never Do
❌ Use `create<T>(...)` (single parentheses) in TypeScript - breaks middleware types
❌ Mutate state directly: `set((state) => { state.count++; return state })` - use immutable updates
❌ Create new objects in selectors: `useStore((state) => ({ a: state.a }))` - causes infinite renders
❌ Use same storage name for multiple stores - causes data collisions
❌ Access localStorage during SSR without hydration check
❌ Use Zustand for server state - use TanStack Query instead
❌ Export store instance directly - always export the hook
## Known Issues Prevention
This skill prevents **6** documented issues:
### Issue #1: Next.js Hydration Mismatch
**Error**: `"Text content does not match server-rendered HTML"` or `"Hydration failed"`
**Source**:
- [DEV Community: Persist middleware in Next.js](https://dev.to/abdulsamad/how-to-use-zustands-persist-middleware-in-nextjs-4lb5)
- GitHub Discussions #2839
**Why It Happens**:
Persist middleware reads from localStorage on client but not on server, causing state mismatch.
**Prevention**:
import { create } from 'zustand'
import { persist } from 'zustand/middleware'
interface StoreWithHydration {
count: number
_hasHydrated: boolean
setHasHydrated: (hydrated: boolean) => void
increase: () => void
}
const useStore = create<StoreWithHydration>()(
persist(
(set) => ({
count: 0,
_hasHydrated: false,
setHasHydrated: (hydrated) => set({ _hasHydrated: hydrated }),
increase: () => set((state) => ({ count: state.count + 1 })),
}),
{
name: 'my-store',
onRehydrateStorage: () => (state) => {
state?.setHasHydrated(true)
},
},
),
)
// In component
function MyComponent() {
const hasHydrated = useStore((state) => state._hasHydrated)
if (!hasHydrated) {
return <div>Loading...</div>
}
// Now safe to render with persisted state
return <ActualContent />
}
### Issue #2: TypeScript Double Parentheses Missing
**Error**: Type inference fails, `StateCreator` types break with middleware
**Source**: [Official Zustand TypeScript Guide](https://zustand.docs.pmnd.rs/guides/typescript)
**Why It Happens**:
The currying syntax `create<T>()()` is required for middleware to work with TypeScript inference.
**Prevention**:
// ❌ WRONG - Single parentheses
const useStore = create<MyStore>((set) => ({
// ...
}))
// ✅ CORRECT - Double parentheses
const useStore = create<MyStore>()((set) => ({
// ...
}))
**Rule**: Always use `create<T>()()` in TypeScript, even without middleware (future-proof).
### Issue #3: Persist Middleware Import Error
**Error**: `"Attempted import error: 'createJSONStorage' is not exported from 'zustand/middleware'"`
**Source**: GitHub Discussion #2839
**Why It Happens**:
Wrong import path or version mismatch between zustand and build tools.
**Prevention**:
// ✅ CORRECT imports for v5
import { create } from 'zustand'
import { persist, createJSONStorage } from 'zustand/middleware'
// Verify versions
// zustand@5.0.9 includes createJSONStorage
// zustand@4.x uses different API
// Check your package.json
// "zustand": "^5.0.9"
### Issue #4: Infinite Render Loop
**Error**: Component re-renders infinitely, browser freezes
Uncaught Error: Maximum update depth exceeded. This can happen when a component repeatedly calls setState inside componentWillUpdate or componentDidUpdate.
**Source**:
- GitHub Discussions #2642
- [Issue #2863](https://github.com/pmndrs/zustand/issues/2863)
**Why It Happens**:
Creating new object references in selectors causes Zustand to think state changed.
**v5 Breaking Change**: Zustand v5 made this error MORE explicit compared to v4. In v4, this behavior was "non-ideal" but could go unnoticed. In v5, you'll immediately see the "Maximum update depth exceeded" error.
**Prevention**:
import { useShallow } from 'zustand/shallow'
// ❌ WRONG - Creates new object every time
const { bears, fishes } = useStore((state) => ({
bears: state.bears,
fishes: state.fishes,
}))
// ✅ CORRECT Option 1 - Select primitives separately
const bears = useStore((state) => state.bears)
const fishes = useStore((state) => state.fishes)
// ✅ CORRECT Option 2 - Use useShallow hook for multiple values
const { bears, fishes } = useStore(
useShallow((state) => ({ bears: state.bears, fishes: state.fishes }))
)
### Issue #5: Slices Pattern TypeScript Complexity
**Error**: `StateCreator` types fail to infer, complex middleware types break
**Source**: [Official Slices Pattern Guide](https://github.com/pmndrs/zustand/blob/main/docs/guides/slices-pattern.md)
**Why It Happens**:
Combining multiple slices requires explicit type annotations for middleware compatibility.
**Prevention**:
import { create, StateCreator } from 'zustand'
// Define slice types
interface BearSlice {
bears: number
addBear: () => void
}
interface FishSlice {
fishes: number
addFish: () => void
}
// Create slices with proper types
const createBearSlice: StateCreator<
BearSlice & FishSlice, // Combined store type
[], // Middleware mutators (empty if none)
[], // Chained middleware (empty if none)
BearSlice // This slice's type
= (set) => ({
bears: 0,
addBear: () => set((state) => ({ bears: state.bears + 1 })),
})
const createFishSlice: StateCreator<
BearSlice & FishSlice,
[],
[],
FishSlice
= (set) => ({
fishes: 0,
addFish: () => set((state) => ({ fishes: state.fishes + 1 })),
})
// Combine slices
const useStore = create<BearSlice & FishSlice>()((...a) => ({
...createBearSlice(...a),
...createFishSlice(...a),
}))
### Issue #6: Persist Middleware Race Condition (Fixed v5.0.10+)
**Error**: Inconsistent state during concurrent rehydration attempts
**Source**:
- [GitHub PR #3336](https://github.com/pmndrs/zustand/pull/3336)
- [Release v5.0.10](https://github.com/pmndrs/zustand/releases/tag/v5.0.10)
**Why It Happens**:
In Zustand v5.0.9 and earlier, concurrent calls to rehydrate during persist middleware initialization could cause a race condition where multiple hydration attempts would interfere with each other, leading to inconsistent state.
**Prevention**:
Upgrade to Zustand v5.0.10 or later. No code changes needed - the fix is internal to the persist middleware.
npm install zustand@latest # Ensure v5.0.10+
**Note**: This was fixed in v5.0.10 (January 2026). If you're using v5.0.9 or earlier and experiencing state inconsistencies with persist middleware, upgrade immediately.
## Middleware
**Persist** (localStorage):
import { persist, createJSONStorage } from 'zustand/middleware'
const useStore = create<MyStore>()(
persist(
(set) => ({ data: [], addItem: (item) => set((state) => ({ data: [...state.data, item] })) }),
{
name: 'my-storage',
partialize: (state) => ({ data: state.data }), // Only persist 'data'
},
),
)
**Devtools** (Redux DevTools):
import { devtools } from 'zustand/middleware'
const useStore = create<CounterStore>()(
devtools(
(set) => ({ count: 0, increment: () => set((s) => ({ count: s.count + 1 }), undefined, 'increment') }),
{ name: 'CounterStore' },
),
)
**v4→v5 Migration Note**: In Zustand v4, devtools was imported from `'zustand/middleware/devtools'`. In v5, use `'zustand/middleware'` (as shown above). If you see "Module not found: Can't resolve 'zustand/middleware/devtools'", update your import path.
**Combining Middlewares** (order matters):
const useStore = create<MyStore>()(devtools(persist((set) => ({ / ... / }), { name: 'storage' }), { name: 'MyStore' }))
## Common Patterns
**Computed/Derived Values** (in selector, not stored):
const count = useStore((state) => state.items.length) // Computed on read
**Async Actions**:
const useAsyncStore = create<AsyncStore>()((set) => ({
data: null,
isLoading: false,
fetchData: async () => {
set({ isLoading: true })
const response = await fetch('/api/data')
set({ data: await response.text(), isLoading: false })
},
}))
**Resetting Store**:
const initialState = { count: 0, name: '' }
const useStore = create<ResettableStore>()((set) => ({
...initialState,
reset: () => set(initialState),
}))
**Selector with Params**:
const todo = useStore((state) => state.todos.find((t) => t.id === id))
## Bundled Resources
**Templates**: `basic-store.ts`, `typescript-store.ts`, `persist-store.ts`, `slices-pattern.ts`, `devtools-store.ts`, `nextjs-store.ts`, `computed-store.ts`, `async-actions-store.ts`
**References**: `middleware-guide.md` (persist/devtools/immer/custom), `typescript-patterns.md` (type inference issues), `nextjs-hydration.md` (SSR/hydration), `migration-guide.md` (from Redux/Context/v4)
**Scripts**: `check-versions.sh` (version compatibility)
## Advanced Topics
**Vanilla Store** (Without React):
import { createStore } from 'zustand/vanilla'
const store = createStore<CounterStore>()((set) => ({ count: 0, increment: () => set((s) => ({ count: s.count + 1 })) }))
const unsubscribe = store.subscribe((state) => console.log(state.count))
store.getState().increment()
**Custom Middleware**:
const logger: Logger = (f, name) => (set, get, store) => {
const loggedSet: typeof set = (...a) => { set(...a); console.log([${name}]:, get()) }
return f(loggedSet, get, store)
}
**Immer Middleware** (Mutable Updates):
import { immer } from 'zustand/middleware/immer'
const useStore = create<TodoStore>()(immer((set) => ({
todos: [],
addTodo: (text) => set((state) => { state.todos.push({ id: Date.now().toString(), text }) }),
})))
**v5.0.3→v5.0.4 Migration Note**: If upgrading from v5.0.3 to v5.0.4+ and immer middleware stops working, verify you're using the import path shown above (`zustand/middleware/immer`). Some users reported issues after the v5.0.4 update that were resolved by confirming the correct import.
**Experimental SSR Safe Middleware** (v5.0.9+):
**Status**: Experimental (API may change)
Zustand v5.0.9 introduced experimental `unstable_ssrSafe` middleware for Next.js usage. This provides an alternative approach to the `_hasHydrated` pattern (see Issue #1).
import { unstable_ssrSafe } from 'zustand/middleware'
const useStore = create<Store>()(
unstable_ssrSafe(
persist(
(set) => ({ / state / }),
{ name: 'my-store' }
)
)
)