The shared real-world entity

Subjects

A Subject is the real-world entity services act on — a company, person, policy, or other typed record in an account-level registry. Subjects are shared across Services so "everything for Acme" is one query.

How subjects appear

As the header entity on an engagement ("Company", "Client", …)
In subject-centric views that stack engagements across services
In triggers that resolve or mint the right engagement for an inbound event

Subjects are not a separate product surface to learn first; they are the shared spine under engagements.