group.members_synced

project_id is always null for group events.

When this fires

The membership of a group is replaced and the result differs from what was there before — via PUT /v1/groups/{group}/members or the dashboard's group editor.

A group carries permissions, so who is in it decides who can do what. Until this event existed, renaming a group announced itself with group.updated while changing who it granted access to announced nothing at all — an integration mirroring access control could see the label change and miss the membership.

A no-op sync is silent

Syncing the same set that is already there emits nothing. This event means the membership actually moved, so receiving one always implies at least one id in added_ids or removed_ids.

Required ability

group:view — the token must carry this at mint time to subscribe an endpoint to this event.

Payload

{
  "id": "evt_01HX...",
  "type": "group.members_synced",
  "created_at": "2026-08-31T10:05:00Z",
  "api_version": "2026-05-01",
  "project_id": null,
  "data": {
    "group_id": "1f68d92a-04c5-4e83-97b1-3d6a05e2f847",
    "team_id": "a83f0d51-4c92-4b7e-8615-2fd9e70a3c86",
    "code": "core-community",
    "name": "Core Community",
    "member_ids": [
      "2a91c4e7-6f38-4b52-8e0d-9c1a7b3f5d80",
      "6f9b2e37-c184-4a05-8d72-30e16bc9f458"
    ],
    "added_ids": ["6f9b2e37-c184-4a05-8d72-30e16bc9f458"],
    "removed_ids": ["d05e1a83-7c46-4f29-b613-8ae407c9d251"],
    "member_count": 2
  }
}

Field reference

Field	Type	Notes
`id`	string ULID	Unique event id, prefixed `evt_`. Use for idempotent processing.
`type`	string	Always `group.members_synced` for this event.
`created_at`	ISO 8601 timestamp	Server-side emission time.
`api_version`	string	Webhook API contract version.
`project_id`	null	Always `null` — account-level event.
`data.group_id`	string UUID	The group whose membership changed.
`data.team_id`	string UUID	Team that owns the group.
`data.code`	string	Stable group code, immutable across renames.
`data.name`	string	Display name at the time of the sync.
`data.member_ids`	array of UUID	The membership after the sync — the complete list, not a page of it.
`data.added_ids`	array of UUID	Users who gained the group in this sync. Possibly empty.
`data.removed_ids`	array of UUID	Users who lost it. Possibly empty.
`data.member_count`	integer	`member_ids.length`, carried so a consumer can size the change without parsing the array.

Why the deltas are in the payload

An access-control mirror needs to know who lost the group, and diffing two snapshots on the far side is work it should not have to do — it requires having stored the previous state, and gets the answer wrong the first time it sees a group. added_ids and removed_ids are computed where the truth is, from the membership read immediately before the write and the list written immediately after it.

member_ids is still there for consumers that would rather replace their copy than apply a patch. Both are consistent with each other.

Caveats

This is a replace, not an add. Anyone absent from the request is removed. An empty list empties the group.
Permissions are not in the payload. What the group grants is a property of the group, not of this event — read it from GET /v1/groups/{group} if your mirror needs the effective permission set.
Users, not projects. A group clusters collaborators. It is not a way to bundle projects.
Removal from a group does not remove anyone from the team.

group.updated — the group was renamed or re-permissioned.
group.created — predecessor.
group.deleted — terminal state; everyone loses what it granted at once.
Group events overview — back to family overview.