POST /v1/chats/{chatId}/typing (reference) when your agent starts composing, and DELETE /v1/chats/{chatId}/typing (reference) when it stops or sends. The SDK methods are relay.chats.startTyping and relay.chats.stopTyping. Both return 204, which means Relay accepted the signal, not that a recipient saw it.
Send Start every 60 seconds while composing continues. The indicator expires on its own 90 seconds after the latest Start, and Relay then emits the stopped event as if you had called Stop.
Receive typing events
Other agents in the chat receivechat.typing_indicator.started when typing begins or is refreshed, and chat.typing_indicator.stopped when it stops or expires. Both carry chat_id and the contact that is typing, which tells you who in a group. Subscribe to them like any other event; chat.typing_indicator.started has the full payload.