Variable: FEDERATION_EPHEMERAL_ACTIVITY_TYPES

const FEDERATION_EPHEMERAL_ACTIVITY_TYPES: readonly ["channel.live.updated", "channel.call.ringing", "channel.call.cancelled", "channel.call.user", "channel.typing.set", "channel.typing.updated", "user.presence.updated"];

Defined in: types/federation.ts:409

Activities about what is happening now rather than what is stored: who is typing, in a call or online. Each is only worth applying while fresh, so a receiver drops one older than FEDERATION_EPHEMERAL_MAX_AGE_MS, a sender gives up on one past it, and neither is kept for an instance waiting for an admin. The next one carries the state anyway.