# React hooks

Run a Kortix session in React with the useSession hook.

Canonical page: https://kortix.com/docs/sdk/react

`@kortix/sdk/react` adds React hooks on top of the SDK. This page covers
`useSession`, the hook that runs a session end to end, and the other hooks
confirmed stable for React apps.

## useSession(projectId, sessionId, options?)

`useSession` starts the session, opens the server-selected event transport, and
syncs messages, status, and pending prompts. Call it once per session view.

```tsx
import { useSession } from '@kortix/sdk/react';

function Chat({ projectId, sessionId }: { projectId: string; sessionId: string }) {
  const s = useSession(projectId, sessionId);

  if (s.phase !== 'ready') return <Booting stage={s.stage} onRetry={s.retry} />;

  return (
    <>
      {s.messages.map(({ info, parts }) => (
        <Message key={info.id} info={info} parts={parts} />
      ))}
      <Composer busy={s.isBusy} onSend={s.send} onStop={s.cancel} />
    </>
  );
}
```

Readiness is server truth. The runtime is ready when `POST /start` returns
`stage: 'ready'`. `useSession` does not run a separate client-side health check.

### Returns

| Field | Type | What it holds |
|---|---|---|
| `phase` | `'starting' \| 'ready' \| 'error'` | Overall state. Render a boot screen until `ready`. |
| `messages` | `{ info, parts }[]` | The message list. Parts stream in live. |
| `status` | `SessionStatus` | The session status. |
| `isBusy` | `boolean` | The agent is generating a reply. |
| `questions`, `permissions` | array | Pending agent questions and permission requests. |
| `diffs`, `todos` | array | Live file diffs and todo items. |
| `sendError` | `KortixSendError \| null` | The last `send` failure: `billing`, `runtime-not-ready`, or `runtime-error`. |
| `rewindMessageId` | `string \| null` | The selected user message while a reversible rewind is staged. |
| `rewindPending` | `boolean` | A rewind or restore request is in progress. |
| `rewindError` | `KortixSendError \| null` | The last rewind or restore failure. |
| `models`, `agents`, `defaultAgent`, `commands` | — | Selectable models, selectable agents, the default agent, and slash commands. Available before the runtime starts. |
| `retry` | `() => void` | Force a re-check of `/start`. |

### Actions

| Action | What it does |
|---|---|
| `send(text, override?)` | Send a prompt. `override` sets `{ model?, agent? }` for this message only. |
| `sendParts(parts, override?)` | Send text and file prompt parts through the selected transport. |
| `rewind(messageId)` | Rewind this canonical session to a user message. The selected message and later path become hidden and recoverable. |
| `restoreRewind()` | Restore the removed path before another prompt commits its replacement. |
| `cancel()` | Stop the current run and clear pending questions and permissions. |
| `runCommand(command, args)` | Run a project slash command. |
| `answerQuestion(id, answers)` | Answer a pending agent question. |
| `rejectQuestion(id)` | Reject a pending agent question. |
| `answerPermission(id, reply, message?)` | Answer a permission request. `reply` is `'once'`, `'always'`, or `'reject'`. |

`useSession` also returns `removeQuestion` and `removePermission`. Do not use
them. They clear the prompt from local state but never notify the agent, so
the run stays blocked. Use `answerQuestion`, `rejectQuestion`, or
`answerPermission` instead.

### Options

| Option | Default | What it does |
|---|---|---|
| `waitMs` | `15000` | The long-poll budget sent to `/start`. |
| `replayStartStash` | `true` | Replay a prompt saved before the session existed, once the session is ready. |
| `enabled` | `true` | Set `false` to delay the hook, for example until a billing check passes. |
| `chatEngine` | `true` | Set `false` if your app mounts its own chat surface for this session, to avoid syncing messages twice. |

Sending is optimistic. `send` shows your message right away, then stream
events fill in the agent's reply.

`rewind(messageId)` never creates a session. It uses the canonical session from
`POST /start`. The runtime restores file state and keeps the removed transcript
path recoverable. The next accepted prompt commits the replacement path.

## Other stable hooks

`@kortix/sdk/react` also exports React Query hooks for data that does not
need a running session. Each mirrors a method on the
[client](/docs/sdk/reference) and needs no provider.

| Hook | Reads |
|---|---|
| `useProjectModels(projectId)` | Selectable models for the project. |
| `useVisibleAgents({ projectId })` | The project's visible agents. |
| `useProjectConfig(projectId)` | The project's runtime config: default agent, commands. |
| `useProjectSecrets(projectId)` | Secrets: list, add, remove, and personal overrides. |
| `useProjectTriggers(projectId)` | Triggers: list, create, update, remove, fire. |
| `useChangeRequests(projectId, status?)` | Change requests: list, open, merge, close, request changes. |

## Next

- [Sessions](/docs/sdk/sessions) — the session handle `useSession` wraps, and the `KortixSendError` kinds.
- [Reference](/docs/sdk/reference) — the full REST surface these hooks read from.