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Architecture: WebSocket / Realtime Architecture ​

Structure for reliable realtime features. See skills/networking/ios/websocket.md and the WebSocket Expert.

Overview ​

An actor-isolated transport manages the socket lifecycle and exposes typed domain events as an AsyncStream. A repository adapts the stream for features; the ViewModel consumes events and reflects connection state in the UI.

Connection State Machine ​

Message Flow with Backpressure ​

Reliability Building Blocks ​

  • State machine — no ad-hoc booleans; every transition explicit.
  • Heartbeat + read timeout — detect dead connections proactively.
  • Backoff + jitter reconnection — capped; never a hot loop.
  • Re-auth on (re)connect — refresh expired tokens first.
  • De-duplication by id — at-least-once delivery assumed.
  • Bounded buffer — explicit overflow policy (drop oldest / coalesce / suspend).

UI State Contract ​

swift
enum RealtimeState { case connecting, connected, reconnecting, disconnected }

The header/status view renders this so users understand degraded connectivity.

Sample (abridged) ​

swift
actor ChatSocket {
    private(set) var state: ConnectionState = .disconnected
    let events: AsyncStream<ChatEvent>
    // connect() authenticates, starts heartbeat, runs receiveLoop(),
    // scheduleReconnect() uses min(pow(2, attempt), 30) + jitter.
    // Full implementation in skills/networking/ios/websocket.md
}