> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ensync.cloud/llms.txt
> Use this file to discover all available pages before exploring further.

# Acknowledging Messages

> Confirm successful event processing

## Usage

<Tabs>
  <Tab title="Node.js">
    ```javascript theme={null}
    const subscription = await client.subscribe("payment/process", {
      autoAck: false
    });

    subscription.on(async (event) => {
      await processPayment(event.payload);
      await subscription.ack(event.idem, event.block);
    });
    ```
  </Tab>

  <Tab title="Python">
    ```python theme={null}
    subscription = await client.subscribe("payment/process", {
      "auto_ack": False
    })

    async def handle_payment(event):
        await process_payment(event.payload)
        await subscription.ack(event.idem, event.block)

    subscription.on(handle_payment)
    ```
  </Tab>
</Tabs>

## Parameters

| Parameter | Type     | Required | Description         |
| --------- | -------- | -------- | ------------------- |
| `idem`    | `string` | Yes      | Unique event ID     |
| `block`   | `string` | Yes      | Block ID from event |

## Auto vs Manual ACK

| Mode             | Behavior                            | Use Case                               |
| ---------------- | ----------------------------------- | -------------------------------------- |
| `autoAck: true`  | Events ACKed when handler completes | Simple processing                      |
| `autoAck: false` | Manual ACK required                 | Critical workflows, custom retry logic |