# Treatment Sessions are separate from Appointments

Multi-session treatments (laser courses, botox top-ups) need a session that keeps its number and its
clinical record across cancellations and reschedules, and they must not lock eight months of calendar
slots the moment a course starts. So a Treatment Session is its own record owning the clinical data,
holding an optional reference to an Appointment; booking a session creates the Appointment, and
rescheduling swaps it without disturbing the session.

## Considered Options

Making the Appointment itself the session was rejected: session numbering would break on every
cancellation, and pre-creating every future session as a real Appointment would occupy slots months
ahead for patients who may never attend.