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

# Event reference

> How the Commission domain stays in sync with order changes.

The Commission domain does **not** emit its own domain events. Commission lines
are derived data, so instead of broadcasting changes, the module **subscribes**
to order lifecycle events and recomputes lines whenever an order's composition
changes.

## Events it reacts to

Mercur ships a subscriber (`order-commission-refresh-handler`) that re-runs
`refreshOrderCommissionLinesWorkflow` for the affected order on each of these
events:

| Event                                  | Emitted when               |
| -------------------------------------- | -------------------------- |
| `OrderEditWorkflowEvents.CONFIRMED`    | An order edit is confirmed |
| `OrderWorkflowEvents.RETURN_RECEIVED`  | A return is received       |
| `OrderWorkflowEvents.CLAIM_CREATED`    | A claim is created         |
| `OrderWorkflowEvents.EXCHANGE_CREATED` | An exchange is created     |

Because the refresh is idempotent (delete-then-insert), reacting to several
events for the same order never duplicates lines.

## Run your own side effects

To run logic when an order's commission changes, subscribe to the same order
events the module listens to, then read the refreshed lines from the commission
module.

```ts title="src/subscribers/commission-changed.ts" theme={null}
import type { SubscriberArgs, SubscriberConfig } from "@medusajs/framework"
import { OrderWorkflowEvents } from "@medusajs/framework/utils"

export default async function commissionChangedHandler({
  event,
  container,
}: SubscriberArgs<{ order_id?: string; id?: string }>) {
  const orderId = event.data.order_id ?? event.data.id
  if (!orderId) {
    return
  }
  // ...read commission lines for the order, notify, sync an external ledger, etc.
}

export const config: SubscriberConfig = {
  event: OrderWorkflowEvents.RETURN_RECEIVED,
}
```

<Note>
  Commission is also refreshed at checkout, as each per-seller order is created
  from the split cart. That refresh happens as a **step inside** the checkout
  workflow rather than via a separate event.
</Note>