clinicpro/docs/adr/0001-treatment-sessions-are-not-appointments.md

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.