⚠️ Experimental endpoint — not yet a stable contract. This action ships as experimental / beta. While experimental, its schema and behaviour may change without a version bump — including breaking changes within v1.0 itself. Anyone consuming it does so for evaluation only, or by coordinating adoption with their account manager so changes can be sequenced with them. It graduates to a stable, version-locked contract (where the normal breaking-change rules apply) only when this experimental notice is removed.

Set the applicable custom field values of a session without changing any other session properties. This action requires permission to view the session and the Sessions.update-custom-fields permission.

Send a JSON object containing the required customFields object. Omitted identifiers remain unchanged, while null clears the corresponding value. When custom fields are enabled for sessions, an empty object succeeds as a no-op. Invalid or unavailable identifiers and invalid values return 422 validation errors. If custom fields are disabled for the tenant or sessions, the action returns 412 Precondition Failed. Neither rejection changes submitted values. A 404 response means the session was not found.