pubsub is the one shared Redis subscriber — reuse it

pubsub (packages/server/api/src/app/helper/pubsub.ts) is the app's single shared Redis subscriber connection. Use it for all in-process fan-out over Redis pub/sub — do not open your own redisConnections.create() subscriber per wait/request (that churns connections and can hit managed-Redis client caps).

How it works (as of Jul 2026): one connection, one on('message') dispatcher registered at connection creation, and a Map<channel, Set<listener>>. subscribe(channel, listener) adds to the set (Redis SUBSCRIBE only on the first listener of a channel); unsubscribe(channel, listener?) removes one listener (or the whole channel if no listener passed) and Redis UNSUBSCRIBEs when the set empties.

Gotcha it used to have: the old subscribe registered a fresh on('message') handler every call and unsubscribe never removed it — a listener leak. Safe then only because every caller subscribed once at startup to a fixed channel. That's fixed now, so churny/dynamic-channel use (subscribe+unsubscribe per turn) is fine — pass the listener to unsubscribe for per-waiter cleanup. Reference caller: chatApprovalGate.waitForDecision in ee/chat/chat-approval-gate.ts.