Streaming Chat API (WebSocket)

[antiv]

Summary

WebSocket-based streaming chat API alongside existing SSE. Better suited for real-time bidirectional communication, multi-turn rapid exchanges, and mobile clients.

Motivation

SSE works for one-way streaming but WebSocket is the standard for chat applications. Mobile SDKs and most frontend frameworks have better WebSocket support. Enables features like typing indicators, read receipts, and real-time presence.

Scope

• WebSocket endpoint (/ws/chat)
• Auth handshake (token-based, compatible with existing auth)
• Message protocol: JSON frames for user messages, agent responses, events
• Connection management: heartbeat, auto-reconnect, session resume
• Typing indicators and presence (optional)
• Backward compatible: SSE continues to work

Acceptance Criteria

• WebSocket chat endpoint working with auth
• Streaming agent responses via WebSocket
• Reconnection with session continuity
• SSE endpoint unchanged (backward compatible)