simstudioai--sim/.claude/rules/sim-stores.md

paths

paths
apps/sim/**/store.ts apps/sim/**/stores/**/*.ts

Zustand Store Patterns

Stores live in stores/. Complex stores split into store.ts + types.ts.

Basic Store

import { create } from 'zustand'
import { devtools } from 'zustand/middleware'
import type { FeatureState } from '@/stores/feature/types'

const initialState = { items: [] as Item[], activeId: null as string | null }

export const useFeatureStore = create<FeatureState>()(
  devtools(
    (set, get) => ({
      ...initialState,
      setItems: (items) => set({ items }),
      addItem: (item) => set((state) => ({ items: [...state.items, item] })),
      reset: () => set(initialState),
    }),
    { name: 'feature-store' }
  )
)

Persisted Store

import { create } from 'zustand'
import { persist } from 'zustand/middleware'

export const useFeatureStore = create<FeatureState>()(
  persist(
    (set) => ({
      width: 300,
      setWidth: (width) => set({ width }),
      _hasHydrated: false,
      setHasHydrated: (v) => set({ _hasHydrated: v }),
    }),
    {
      name: 'feature-state',
      partialize: (state) => ({ width: state.width }),
      onRehydrateStorage: () => (state) => state?.setHasHydrated(true),
    }
  )
)

Rules

1. Use devtools middleware (named stores)
2. Use persist only when data should survive reload
3. persist MUST use partialize with an explicit whitelist of the durable fields. Exclude transient flags (isResizing, drag/hover state) and _hasHydrated from the whitelist, and never spread the whole state ({ ...state }) — it leaks actions and transient state into storage
4. _hasHydrated pattern for persisted stores needing hydration tracking
5. Immutable updates only
6. set((state) => ...) when depending on previous state
7. Provide reset() action

Outside React

const items = useFeatureStore.getState().items
useFeatureStore.setState({ items: newItems })