Hi @Layfando , good catch! At the moment, the custom_type and custom_type_status_option properties are conciosly gated on POST (task creation) and are only supported via PUT (task update).
The behavior is expected to be aligned so that creating a custom type task can be done seamlessly, but there’s still some dependency work to complete before that can happen. Until then, the supported pattern is to create the task via POST /tasks (without custom_type fields) and then update it via PUT /tasks/{task_gid} with intended custom_type / custom_type_status_option.