# React bindings

> CardProvider and the hooks of @neurosquad/card-sdk/react — context, settings, storage, agents, ports, tools, theme, language and visibility.

Source: https://docs.neurosquad.ai/en/card-sdk/react

`@neurosquad/card-sdk/react` wraps the card in a provider and exposes its live state as hooks.
React 18.2+ or 19 is a peer dependency; the React template sets everything up.

```tsx
import { createRoot } from 'react-dom/client'
import { CardProvider, useCardContext, useStorage } from '@neurosquad/card-sdk/react'

function App() {
  const { instance, workspace } = useCardContext()
  const [count, setCount] = useStorage('count', 0)
  return (
    <button className="ns-btn ns-btn--primary" onClick={() => setCount(count + 1)}>
      {instance.displayName} in {workspace.name}: {count}
    </button>
  )
}

createRoot(document.getElementById('root')!).render(
  <CardProvider fallback={<p>Connecting…</p>}>
    <App />
  </CardProvider>
)
```

## `CardProvider`

| Prop | Meaning |
| --- | --- |
| `card` | A card you connected yourself — for example from the [mock host](https://docs.neurosquad.ai/en/card-sdk/testing). Without it the provider calls `connect()`. |
| `connectOptions` | Options for `connect()`. |
| `fallback` | Rendered while connecting. |
| `errorFallback` | `(error) => ReactNode`, rendered if connecting fails. Default: the error message. |

The React template connects first and then passes `card` — so the same entry works inside the app
and, with the mock host, in a browser preview.

## Hooks

| Hook | Returns |
| --- | --- |
| `useCard()` | The [`Card`](https://docs.neurosquad.ai/en/card-sdk/api#the-card-object) — for anything without a dedicated hook. |
| `useCardContext()` | The live [`HostContext`](https://docs.neurosquad.ai/en/card-sdk/api#context); re-renders on any change. |
| `useSettings()` | `[settings, setSettings]` — `settings.values`, `settings.secrets`; the setter changes non-secret values. |
| `useStorage(key, initial, { scope? })` | `[value, setValue, { loading, error }]` — like `useState`, persisted. The setter updates at once and writes in the background; accepts a function. `scope: 'package'` follows writes from other copies of the card. |
| `useAgents()` | `{ agents, loading, error, refresh }` — kept current from status and change events. Needs `agents.read`. |
| `useAgentStatus(agentId)` | One agent's status, or `undefined`. |
| `usePort(input?)` | `{ data, message }` — the last value that arrived on an input (or any input). |
| `useEmit(output)` | A stable `(data) => Promise<number>` that emits on an output. |
| `usePortRequest(input, handler)` | Answers a request input while mounted. |
| `usePeers()` | Connected cards and their ports, live. |
| `useTool(name, handler)` | Implements a manifest tool while mounted; always calls the latest handler. |
| `useCardEvent(event, handler)` | Any event while mounted; always calls the latest handler. |
| `useTheme()` | The `ThemeSnapshot`, live (the CSS variables are applied already). |
| `useLanguage()` | `{ language, locale }`, live. |
| `useTranslator(catalog)` | A [translator](https://docs.neurosquad.ai/en/card-sdk/api/environment#i18n) that re-renders on a language switch. Define the catalog outside the component. |
| `useVisibility()` | `visible`, `offscreen`, `overview` or `hidden`. |
| `usePaused()` | `true` when nobody can see the card's body — pause animations and polling. |
| `useExpanded()` | Whether the card is expanded. |

## A fuller example

```tsx
import type { Catalog } from '@neurosquad/card-sdk'
import {
  useAgents,
  useCard,
  useEmit,
  usePaused,
  usePort,
  useTool,
  useTranslator
} from '@neurosquad/card-sdk/react'
import { useEffect } from 'react'

const catalog: Catalog = {
  en: { waiting_one: '{{count}} agent waits for you', waiting_other: '{{count}} agents wait for you' },
  ru: {
    waiting_one: '{{count}} агент ждёт вас',
    waiting_few: '{{count}} агента ждут вас',
    waiting_many: '{{count}} агентов ждут вас',
    waiting_other: '{{count}} агента ждут вас'
  },
  zh: { waiting_other: '{{count}} 个智能体在等你' }
}

export function Waiting() {
  const card = useCard()
  const t = useTranslator(catalog)
  const paused = usePaused()
  const { agents } = useAgents()
  const waiting = agents.filter((a) => a.status === 'needs-input')
  const { data: note } = usePort<string>('notes')
  const emit = useEmit<string>('digest')

  // Keep the overview tile and attention in step with the data.
  useEffect(() => {
    void card.setOverview({ primary: t('waiting', { count: waiting.length }), icon: 'bell' })
    void card.attention(waiting.length > 0 ? 'needs-input' : 'none').catch(() => undefined)
  }, [card, t, waiting.length])

  useTool('list_waiting', () => waiting.map((a) => a.name))

  return (
    <div className="ns-stack">
      <p className={paused ? '' : 'pulse'}>{t('waiting', { count: waiting.length })}</p>
      {note ? <pre className="ns-mono">{note}</pre> : null}
      <button className="ns-btn" onClick={() => void emit(waiting.map((a) => `- ${a.name}`).join('\n'))}>
        Send digest
      </button>
    </div>
  )
}
```

> Hooks that call the app (`useAgents`, `useStorage`) report failures in their `error` field instead
> of throwing — a missing permission shows up there as a `CardSdkError` with `PERMISSION_DENIED`.

## Using a local SDK checkout

If your card depends on the SDK through a `file:` link, npm creates a symlink and Vite may load a
second copy of React next to the SDK — hooks then fail with "Invalid hook call". The React template's
`vite.config.ts` already has `resolve: { dedupe: ['react', 'react-dom'] }`; in your own setup, add it,
or set `install-links=true` in the card's `.npmrc`.