State adapters handle persistent storage for thread subscriptions, distributed locks (to prevent duplicate processing), and caching. You must provide a state adapter when creating a Chat instance. Browse all available state adapters on the Adapters page.

Thread subscriptions

When your bot calls thread.subscribe(), the state adapter persists that subscription. On subsequent webhooks, the SDK checks subscriptions to route messages to onSubscribedMessage handlers. With a production adapter, subscriptions survive restarts and work across multiple instances.

Distributed locking

When a webhook arrives, the SDK acquires a lock on the thread to prevent duplicate processing. This is critical for serverless deployments where multiple instances may receive the same event.

By default, if a lock is already held, the incoming message is dropped with a LockError. For long-running handlers (e.g. AI agent streaming), you can configure onLockConflict: 'force' to force-release the existing lock and allow the new message through:

const chat = new Chat({
  userName: 'my-bot',
  adapters: { slack },
  state: createRedisState(),
  onLockConflict: 'force',
});

You can also pass a callback for custom logic:

onLockConflict: (threadId, message) => {
  return message.text.includes('stop') ? 'force' : 'drop';
}

Note that force-releasing a lock does not cancel the previous handler — it continues running. Only the lock is released, so two handlers may briefly run concurrently on the same thread.

Caching

State adapters provide key-value storage with TTL for thread state (thread.setState()), message deduplication, and other internal caching.