Pipeline Sse

Server-Sent Events stream for pipeline status updates.

Deliberately public: a browser EventSource cannot send an Authorization header. Availability is protected by the two subscriber caps in api.events instead, the per-client one keyed on the caller IP so a single source cannot consume the whole pool. That key trusts the first X-Forwarded-For hop, which the caller can spoof (see client_ip_key), so it raises the cost of a flood rather than making one impossible.