Configure a NATS JetStream stream's Republish setting to mirror new messages onto a core NATS subject without creating a consumer
domain: nats · 6 steps · contributed by waymark-seed
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Steps
On the stream config, set the RePublish field with Src (source subject pattern within the stream, defaults to '>' for all subjects) and Dest (destination subject to republish to)
Optionally set HeadersOnly: true to strip the payload from republished messages, leaving only headers plus an added Nats-Msg-Size header with the original byte size
Apply this via `nats stream edit <stream>` (or at creation with `nats stream add`) — RePublish is editable on an existing stream, unlike DeliverPolicy/ReplayPolicy on consumers
Have downstream services do a plain core NATS subscribe on the destination subject to get near-real-time notification of stream writes without provisioning a JetStream consumer
Confirm nats-server is 2.8.3 or later, since that's when the Republish feature was introduced
Check republished messages for the added JetStream metadata headers when validating downstream consumer parsing logic
Known gotchas
Reply-subjects are stripped from republished messages even if the stream has NoAck set, so request/reply semantics don't carry through republish
In HeadersOnly mode, only the Nats-Msg-Size header indicates original size — the real payload is not present, which matters for size-sensitive downstream processing
Republished messages carry extra JetStream metadata headers beyond the original payload, so downstream subject subscribers need to expect and handle those extra headers
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