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

# Event streaming v3 application contract

> Event streaming documentation now records the v3 application-topic and producer-identity contracts.

<Badge stroke icon="calendar-days" iconType="regular">August 20, 2026</Badge> <Badge stroke icon="file-code" iconType="regular">Documentation correction</Badge> <Badge color="red" size="lg" stroke icon="triangle-exclamation" iconType="regular">Action required</Badge>

## Affects

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Teams that produce or consume event streams from Fetcher, Lender, Matcher, Midaz, Reporter, or Tracer.

## What changed

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Kafka producers publish to documented application topics such as `lerian.streaming.ledger`. Consumers subscribe to those topics and route individual facts by CloudEvents headers. Reporter uses AMQP instead: it publishes to the exchange named by `RABBITMQ_REPORT_EVENTS_EXCHANGE` and uses each event definition key as the routing key. Producers validate their roster source values, and CloudEvents types are source-qualified.

Matcher now publishes the topic consumed by Lender's enabled matcher handoff. Reporter events use the `reporter` source; their manifests carry event keys and do not define per-event topic or dead-letter-topic fields. Reporter consumers bind queues to the configured exchange and route by the manifest event key.

This is a documentation correction of implemented contracts. It does not announce a runtime release.

## Impact

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**Classification: Action required.** Topic derivation, source configuration, event routing, or Reporter manifest handling based on the former contract can prevent delivery or route events incorrectly.

## What you need to do

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<Steps>
  <Step>Kafka producers publish to the documented application topics. Kafka consumers subscribe to those topics and route facts by their CloudEvents headers. For Reporter, bind a queue to `RABBITMQ_REPORT_EVENTS_EXCHANGE` and route by the event definition key.</Step>
  <Step>Set each producer's documented source value and review consumer assumptions about source-qualified event types.</Step>
  <Step>Review Matcher-to-Lender and Reporter integrations before the next streaming deployment.</Step>
</Steps>

### Deadline

Complete the review before the next producer, consumer, or streaming-integration deployment.

## Resources

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* [Event streaming overview](/en/reference/events/overview)
* [Midaz events](/en/reference/events/midaz)
* [Reporter events](/en/products/reporter/reporter-events)