Group conversations

People create groups in the Relay app and add agents to them. Your backend receives an event only when a human explicitly invokes your agent, and replies to that invocation with the ID Relay supplied.

The invocation boundary

Group membership is not transcript authority. This is the single rule that shapes everything else on this page.

Your backend receives	Your backend does not receive
Messages that explicitly invoke your agent	Ambient group conversation
Your agent’s own replies, in history	Messages between other participants
Membership and metadata lifecycle events	Any message from before it was added

An agent added to a group yesterday cannot read what the group said this morning. Only invocations reach you.

Receive an invocation

A group message.received carries an extra data.invocation_id alongside the usual message envelope.

{
  "event_type": "message.received",
  "agent_id": "agt_01JZRELAY",
  "data": {
    "invocation_id": "inv_01JZC7INVOKE",
    "message": {
      "id": "msg_01JZM3T8AH",
      "conversation_id": "cnv_01JZC7K4RQ",
      "sequence": 12,
      "sender": { "kind": "user", "id": "usr_01JZU1F0BD" },
      "parts": [{ "part_index": 0, "type": "text", "text": "@scheduler when are we free?" }],
      "status": "sent",
      "created_at": "2026-07-17T12:00:00.000Z"
    }
  }
}

Treat invocation_id as required state for the reply. Store it with the event_id you are already deduplicating on.

Reply to an invocation

Reply exactly as you would in a direct conversation, and pass the invocation_id through.

curl -sS -X POST "$RELAY_API_URL/v1/messages" \
  -H "Authorization: Bearer $RELAY_AGENT_TOKEN" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: reply-evt_01JZE9M2XW" \
  -d '{
    "conversation_id": "cnv_01JZC7K4RQ",
    "invocation_id": "inv_01JZC7INVOKE",
    "parts": [{ "type": "text", "text": "Thursday after 4pm works for everyone." }]
  }'

A streaming reply carries it as a query parameter, not a body field:

curl -sS -X POST \
  "$RELAY_API_URL/v1/messages?stream=true&conversation_id=cnv_01JZC7K4RQ&invocation_id=inv_01JZC7INVOKE" \
  -H "Authorization: Bearer $RELAY_AGENT_TOKEN" \
  -H "Idempotency-Key: reply-evt_01JZE9M2XW" \
  -H "Content-Type: text/event-stream" \
  -H "x-vercel-ai-ui-message-stream: v1" \
  --data-binary @reply.sse

Invocation errors

Status	Message	Cause
`403 forbidden`	`group agent replies require invocation_id`	A group reply omitted it
`403 forbidden`	`group agent streams require invocation_id`	A group stream omitted the query parameter
`403 forbidden`	`invocation is invalid, completed, or belongs to another agent`	The invocation was already consumed, or is not yours
`403 forbidden`	`invocation belongs to an ended membership period`	Your agent was removed and re-added since
`403 forbidden`	`message is outside this agent's invocation scope`	The reply targets content you were never invoked on
`422 invalid_request`	`invocation_id must be a Relay invocation id`	Malformed ID

An invocation is consumed once. Reuse the same Idempotency-Key to retry a reply safely; do not reuse the invocation_id for a second, different message.

Membership and metadata events

Relay emits lifecycle events to every active group agent.

Event	Emitted when
`conversation.added`	A human adds your agent to a group
`conversation.updated`	A human renames the group or changes its avatar
`conversation.removed`	A human removes your agent

Each payload is typed and self-contained: conversation_id, the human actor, the affected participant when the mutation targets one, the current membership_version, a structured system_mutation with old and new values, and the canonical system message. Full payloads are in event types.

A lifecycle event grants no transcript access. conversation.added tells you that you are a member, not what the group has been saying.

Limits

Limit	Value
Participants per group	25, including every human and agent
Historical participants tracked	100
Group title	1 to 100 characters
Agents required per group	At least 1
Invocation stream claim	5 minutes

What people do, and what backends cannot

Group creation and membership are first-party app actions, authenticated with a person’s Relay session. There is no Agent Token route for them.

Action	Who
Create a group, set its title	A person, in the app
Add or remove a participant	A person, in the app
Rename the group or change its avatar	A person, in the app
Leave the group	A person, in the app
Invoke an agent	A person, in the app
Reply to an invocation	Your backend
Send a group invite card	Your backend, via `POST /v1/groups/invites`; the person consents in the app

Direct membership writes stay human. A backend can propose with an invite card, and group.invite.completed or group.invite.expired reports the terminal state, but only a person’s consent changes who is in a group. Fuller agent-initiated management is on the roadmap.

Next steps

Event types for the exact lifecycle payloads
Sending messages for every part type
Streaming replies
Developer data access and retention

Overview

Get started

Messages

Message components

Conversations

Webhooks & events

Reference

Group conversations

The invocation boundary

Receive an invocation

Reply to an invocation

Invocation errors

Membership and metadata events

Limits

What people do, and what backends cannot

Next steps

​The invocation boundary

​Receive an invocation

​Reply to an invocation

​Invocation errors

​Membership and metadata events

​Limits

​What people do, and what backends cannot

​Next steps

The invocation boundary

Receive an invocation

Reply to an invocation

Invocation errors

Membership and metadata events

Limits

What people do, and what backends cannot

Next steps