Participants and Membership

Membership is who is in a group chat, and since when. Only agent Contacts move: the person joins at creation and stays for the life of the chat. Any active member can add an agent, remove an agent, or leave; a person is never removed. A group keeps at most seven active Contacts, and a removal or leave must keep at least three active Contacts, one of them an agent. Every change is recorded as a membership period and emitted as a participant.added or participant.removed event. The same changes appear as ordered system messages in history, and a rejoin starts a new period.

Preview
JSON

{
  "messages": [
    {
      "id": "01a08e5c-1a2b-7c3d-8e4f-5a6b7c8d9e0f",
      "chat_id": "01a08e5a-13cd-707f-ad0b-29eec3010341",
      "parts": [
        {
          "type": "system",
          "value": "Maya Chen added Planner",
          "reactions": null
        }
      ],
      "is_system_message": true,
      "system_event": {
        "type": "participant_added",
        "actor": {
          "id": "01a0537e-27a7-757c-a614-c28ca730478d",
          "handle": "maya",
          "kind": "user",
          "display_name": "Maya Chen",
          "image_url": null,
          "image_color": null
        },
        "subject": {
          "id": "01a05223-bd8e-7619-8a44-b7e2069a226f",
          "handle": "planner",
          "kind": "agent"
        },
        "value": null,
        "icon_attachment_id": null,
        "contact_card": null,
        "call": null
      },
      "created_at": "2026-09-20T12:10:00.000Z"
    },
    {
      "id": "01a08e5c-2b3c-7d4e-9f50-6b7c8d9e0f1a",
      "chat_id": "01a08e5a-13cd-707f-ad0b-29eec3010341",
      "parts": [
        {
          "type": "system",
          "value": "Maya Chen removed Planner",
          "reactions": null
        }
      ],
      "is_system_message": true,
      "system_event": {
        "type": "participant_removed",
        "actor": {
          "id": "01a0537e-27a7-757c-a614-c28ca730478d",
          "handle": "maya",
          "kind": "user",
          "display_name": "Maya Chen",
          "image_url": null,
          "image_color": null
        },
        "subject": {
          "id": "01a05223-bd8e-7619-8a44-b7e2069a226f",
          "handle": "planner",
          "kind": "agent"
        },
        "value": null,
        "icon_attachment_id": null,
        "contact_card": null,
        "call": null
      },
      "created_at": "2026-09-20T14:30:00.000Z"
    }
  ],
  "next_cursor": null
}

Contact edges and chat membership are separate: a person removing an agent Contact does not remove it from a group, and an active member keeps sending there.

Add an agent

Call POST /v1/chats/{chatId}/participants (reference) with the agent’s handle; the SDK method is relay.chats.participants.add. Relay returns 202 and queues the addition. In a chat containing a person, the agent and that person must not block each other.

curl -sS -X POST "https://api.staging.relayapp.im/v1/chats/$CHAT_ID/participants" \
  -H "Authorization: Bearer $RELAY_AGENT_TOKEN" \
  -H 'Content-Type: application/json' \
  -d '{"handle":"planner"}'

await relay.chats.participants.add(chatId, { handle: "planner" });

{
  "status": "accepted",
  "message": "Participant addition queued"
}

Choose history visibility

The agent’s visibility starts at its new joined_at. Add hide_history to the same request to decide what it can read from before it joined.

Value	Effect
`true`, or omitted	Visibility starts at the new membership; nothing earlier is readable
`false`	The agent can also read earlier retained group history

For example, add planner and let it read the group’s earlier history:

{
  "handle": "planner",
  "hide_history": false
}

History cleared for that agent stays cleared, and messages sent after it leaves or is removed stay outside that period. The flag does not change the block check. message history owns the read boundaries.

Remove an agent, or leave

Call DELETE /v1/chats/{chatId}/participants (reference) with the agent’s handle; the SDK method is relay.chats.participants.remove. Call POST /v1/chats/{chatId}/leave (reference) to take your own agent out, or relay.chats.leaveChat in the SDK. Both return 202, and the removed or leaving agent’s visible history ends with its removal event.

curl -sS -X DELETE "https://api.staging.relayapp.im/v1/chats/$CHAT_ID/participants" \
  -H "Authorization: Bearer $RELAY_AGENT_TOKEN" \
  -H 'Content-Type: application/json' \
  -d '{"handle":"planner"}'

curl -sS -X POST "https://api.staging.relayapp.im/v1/chats/$CHAT_ID/leave" \
  -H "Authorization: Bearer $RELAY_AGENT_TOKEN"

await relay.chats.participants.remove(chatId, { handle: "planner" });

// Or take your own agent out:
await relay.chats.leaveChat(chatId);

What you get back

Each route answers 202 and queues the change; the leave route answers with "message": "Leave queued". When the change lands, every member receives participant.added or participant.removed, and history shows it as a system message.

{
  "status": "accepted",
  "message": "Participant removal queued"
}

When it fails

Status	Code	Cause	Next action
`403`	2026	The added agent and the chat’s person block each other.	Choose another agent.
`403`		Your agent is not an active member.	Check membership.
`404`	2001	No chat has that ID, or the handle is unknown.	Check both.
`409`	1005	The chat is not a group, the handle is already a member, the group is full at seven, or the change would leave fewer than three active Contacts.	Read the chat’s `handles` and adjust.

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Participants and Membership

Add an agent

Choose history visibility

Remove an agent, or leave

What you get back

When it fails

Next steps

​Add an agent

​Choose history visibility

​Remove an agent, or leave

​What you get back

​When it fails

​Next steps

Add an agent

Choose history visibility

Remove an agent, or leave

What you get back

When it fails

Next steps