zustand

name	zustand
description	Manages Zustand state stores with immer middleware, zundo undo/redo, slices pattern, and computed selectors for the EFIS Checklist Editor. Use when: creating or modifying Zustand stores, adding store actions, wiring undo/redo, splitting stores into slices, optimizing selectors, or connecting stores to React components.
allowed-tools	Read, Edit, Write, Glob, Grep, Bash, mcp__context7__resolve-library-id, mcp__context7__query-docs

Zustand Skill

Zustand manages all client-side state in the EFIS Checklist Editor. The project uses three stores: checklist-store (data + CRUD), ui-store (panel visibility), and undo/redo via zundo temporal middleware. All stores live in src/stores/ with a barrel export. Immer middleware enables mutable update syntax for deeply nested checklist structures.

Quick Start

Create a typed store

// src/stores/ui-store.ts
import { create } from "zustand";

interface UiState {
  propertiesPanelVisible: boolean;
  sidebarVisible: boolean;
  treePanelVisible: boolean;
  togglePropertiesPanel: () => void;
  toggleSidebar: () => void;
  toggleTreePanel: () => void;
}

export const useUiStore = create<UiState>()((set) => ({
  propertiesPanelVisible: true,
  sidebarVisible: true,
  treePanelVisible: true,
  togglePropertiesPanel: () =>
    set((s) => ({ propertiesPanelVisible: !s.propertiesPanelVisible })),
  toggleSidebar: () => set((s) => ({ sidebarVisible: !s.sidebarVisible })),
  toggleTreePanel: () =>
    set((s) => ({ treePanelVisible: !s.treePanelVisible })),
}));

Store with immer + zundo (undo/redo)

// src/stores/checklist-store.ts
import { create } from "zustand";
import { immer } from "zustand/middleware/immer";
import { temporal } from "zundo";
import type { ChecklistFile } from "@/types/checklist";

interface ChecklistState {
  files: Record<string, ChecklistFile>;
  activeFileId: string | null;
  addFile: (file: ChecklistFile) => void;
  removeFile: (id: string) => void;
}

export const useChecklistStore = create<ChecklistState>()(
  temporal(
    immer((set) => ({
      files: {},
      activeFileId: null,
      addFile: (file) =>
        set((state) => {
          state.files[file.id] = file;
          state.activeFileId = file.id;
        }),
      removeFile: (id) =>
        set((state) => {
          delete state.files[id];
          if (state.activeFileId === id) {
            state.activeFileId = null;
          }
        }),
    })),
    {
      partialize: (state) => {
        const { files, activeFileId } = state;
        return { files, activeFileId };
      },
    },
  ),
);

Use undo/redo in components

const { undo, redo, pastStates, futureStates } =
  useChecklistStore.temporal.getState();
const canUndo = pastStates.length > 0;
const canRedo = futureStates.length > 0;

Key Concepts

Concept	Usage	Example
Immer middleware	Mutable syntax for nested updates	set((s) => { s.files[id].name = n })
Zundo temporal	Undo/redo on data stores	temporal(immer(...), { partialize })
Partialize	Exclude actions from undo history	Return only state fields, not functions
Selectors	Prevent unnecessary re-renders	useStore((s) => s.activeFileId)
Separate stores	UI state vs data state	useUiStore vs useChecklistStore

Common Patterns

Selector with shallow equality

When: Selecting multiple fields from a store.

import { useShallow } from "zustand/shallow";

const { activeFileId, files } = useChecklistStore(
  useShallow((s) => ({ activeFileId: s.activeFileId, files: s.files })),
);

Derived/computed values

When: Deriving active file/checklist/item from IDs in the store.

// Compute during render — do NOT store derived state
function EditorHeader() {
  const activeFile = useChecklistStore((s) =>
    s.activeFileId ? s.files[s.activeFileId] : null,
  );
  // ...
}

Dependencies

pnpm add zustand immer zundo

See Also

• patterns — Store structure, slices, anti-patterns
• workflows — Adding stores, wiring undo/redo, testing

Related Skills

• See the react skill for component integration and hooks
• See the typescript skill for type definitions used in store state
• See the zod skill for validating data flowing into stores from IPC

Documentation Resources

Fetch latest Zustand documentation with Context7.

How to use Context7:

1. Use mcp__context7__resolve-library-id to search for "zustand"
2. Prefer website documentation (IDs starting with /websites/) over source code repositories
3. Query with mcp__context7__query-docs using the resolved library ID

Library IDs:

• Zustand docs: /websites/zustand_pmnd_rs
• Zustand source: /pmndrs/zustand
• Zundo (undo/redo): /charkour/zundo

Recommended Queries:

• "zustand store creation TypeScript middleware"
• "zustand immer middleware nested state updates"
• "zundo temporal middleware undo redo partialize"
• "zustand slices pattern compose stores"