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chore(event-gateway): clarify that we don't support multiple header v… #5601

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chore(event-gateway): clarify that we don't support multiple header v… #5601

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chore(event-gateway): clarify that we don't support multiple header v…
lahabana Jun 16, 2026
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Potential fix for pull request finding
lahabana Jun 17, 2026
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8 changes: 8 additions & 0 deletions app/event-gateway/known-limitations.md
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Expand Up @@ -29,4 +29,12 @@ breadcrumbs:

* [Compacted topics](https://docs.confluent.io/kafka/design/log_compaction.html#topic-compaction) used with policies and namespaces are untested

## Record headers

Kafka record headers are multi-valued: the [Kafka protocol](https://cwiki.apache.org/confluence/display/KAFKA/KIP-82+-+Add+Record+Headers) allows the same header key to appear more than once in a single record, and clients can read every occurrence.

{{site.event_gateway}} models record headers as a single value per key. When a record is processed by a policy that reads or transforms headers (for example, encryption, schema validation, or `modify_headers`), records that carry duplicate header keys are collapsed so that only the **last** value for each key is kept; earlier values with the same key are dropped.

This affects only records that {{site.event_gateway}} decodes to apply record-level policies. If your clients rely on multiple headers that share the same key, don't route those topics through header-transforming policies. See the [{{site.event_gateway}} headers reference](/event-gateway/headers/) for the headers {{site.event_gateway}} adds and interprets.


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