Directory process holding (SessionId, Subject, Client, Pid) rows. Answers
the SSO probe lookup(Subject, Client) and the fan-out sessions_for(Subject)
(one subject, many clients). Routes only — no grant state, decides nothing.
Integration-tested: register a live session, route to it, confirm active.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>