⚠️ 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 vehicle without changing any other vehicle properties. This action requires permission to view the vehicle and the Vehicles.update-custom-fields permission.

Send a JSON object containing only the required customFields property. Query parameters and additional body properties are rejected. When custom fields are enabled for vehicles, the customFields object may be empty and succeeds as a no-op without creating a value audit. Omitted identifiers remain unchanged, while an explicit null clears the corresponding value. Every submitted identifier is validated against the vehicle, the current custom field configuration and the acting administrator's access. Unknown, inaccessible, inapplicable or currently disabled identifiers return 422 validation errors keyed as customFields.<identifier>. If custom fields are disabled for the tenant or for vehicles, the action returns 412 Precondition Failed and changes no submitted values. Malformed request bodies and invalid values for available fields return 422 validation errors keyed to the relevant request property. No submitted values are changed when the action is rejected. A 404 response means the vehicle was not found or is not accessible to the caller.