The last active admin cannot be demoted or deactivated: 409 urn:six-minute:problem:last-admin. Deactivating a member of a firm whose practice system each person signs in to deletes that member's own session there and their binding; nothing is sent to the practice system. Deactivating a member also deletes their calendar account with its stored events and marks, and asks the provider to revoke where it allows. This is also how a former member comes back. The interval is the firm's (PATCH /v1/tenant/settings).

Operator mount: an operator acting for the firm named in the path, as its oldest active admin, else its oldest active billing member; X-Six-Minute-Acting-As names them. 404 for no such firm, 409 urn:six-minute:problem:no-acting-member for one with neither.