ADR-005: Realtime topics, cursor/resume and whether OpenVibe.Realtime exists

Status: Accepted 2026-09-22: realtime runs inside OpenVibe.Events

Context and current evidence

The charter for OpenVibe.Realtime was frozen pending this decision. Browser realtime today is five product-local WebSocket servers in Live.

Decision

• Browser realtime is a delivery plane inside OpenVibe.Events (SSE /realtime/stream), authorised per topic and per event visibility (public, subject, internal never to browsers), with Last-Event-ID resume and an explicit gap message when history is gone.
• OpenVibe.Realtime is not created now. Revisit only when measured connection counts or fan-out latency need an independently scaled process; the move is mechanical because the protocol is fixed here.
• Media and game traffic never go through this plane.

Alternatives considered

• Separate Realtime service now: rejected, adds a deploy unit with no measured need.
• WebSockets instead of SSE: SSE suffices for server→browser fan-out and resumes natively; chat keeps its own WebSocket until Wave 6.

Migration consequences

Live's product WebSockets stay until their domains move (Chat in Wave 6).

Rollback

SSE is additive; disabling it leaves durable delivery untouched.

Acceptance tests

Guessed private topic yields nothing; reconnect from a cursor gets the complete authorised sequence or a gap marker.