Submatter/plans/Plan-workspace-communications/Epic-workspace-chat/Task-chat-realtime-delivery.md

kind	slug	title	plan_slug	epic_slug	status	priority	tenant_id	owner	cursor_todo_id	updated_at
task	chat-realtime-delivery	Deliver scalable realtime chat events	workspace-communications	workspace-chat	ready	P1	global	unassigned	null	2026-10-22

Task summary

Broadcast committed chat events over authenticated WebSockets and support horizontal fan-out and reconnect recovery.

Description

Use HTTP/tRPC for commands and Postgres as the source of truth. Consume the outbox contract and atomic writes established by the persistence task; do not create a second message transaction. A worker claims and publishes normalized events through Redis to authenticated WebSocket subscribers. Each channel uses its own (channel_id, sequence) cursor, and clients reconnect by replaying missed rows from Postgres per authorized channel. Reuse Hocuspocus/Yjs only for presence, typing, or drafts rather than canonical history.

Subtasks

• Finalize one versioned envelope for message, reply, tombstone, channel lifecycle, membership, and read-state events using the existing outbox contract.
• Add subscriptions/replay using workspace AND context AND channel access; recheck at delivery, close revoked subscriptions, and test that removed access never receives subsequent payloads. No same-workspace-only shortcut or unsupported-object fallback.
• Claim and publish outbox events through Redis with retry and idempotent consumption semantics.
• Add per-channel reconnect catch-up and cross-device read-state invalidation.
• Add heartbeat, backpressure, graceful-shutdown, outage, ordering, and authorization tests.

Owner or assignee

unassigned

Status

ready

Estimation

L

Acceptance criteria

• A message is visible through the query API even when Redis is unavailable.
• Multiple realtime instances deliver committed events to local subscribers.
• Clients recover each subscribed channel from its own sequence without duplicates or assumed cross-channel ordering.
• Subscription authorization matches public/private/direct/archived rules and is rechecked against current workspace/channel access.
• Durable mark-read events reconcile unread badges on another connected device.
• pnpm lint && pnpm type-check && pnpm test pass; pnpm build passes for changed server entry points.

Links to related Epic / Plan

• Epic: ./Epic-workspace-chat.md
• Plan: ../Plan-workspace-communications.md