7 parts, in order.
The delegated-access series treated the authenticated login as the whole security principal. It isn't quite. The same real person routinely holds more than one login, and an authorisation model that can't tell them apart ends up merging blast radii it shouldn't.
It's easy to claim an authorisation model is generic. It's more convincing to run the exact same model, unmodified, across media, healthcare, financial services, telco, retail and legal case management, and show the tests passing every time.
A company registry needs three things a subscription service doesn't: a public entry anyone can search, a governance role distinct from day-to-day admin, and proof that whoever holds that role is who they say they are.
Every delegation in this series so far has been bounded by time. This post covers the other kind: bounded by a dollar figure, or a dollar figure and a category together, checked fresh against every attempted spend rather than a stored running total.
The model from this series has humans and businesses as principals, but not agents, and no way to represent a delegation that's been requested but not yet approved. Both turned out to need real additions, not workarounds.
An adversarial review across two different AI models caught a real OpenFGA semantics bug in the model behind this series, and also produced confident, specific-sounding nonsense that didn't survive being checked. Both outcomes are worth writing up.
Verification level answers who a persona provably is, established once and true forever. Session assurance answers something else entirely - how strongly the current login just proved it - and it has no business being stored as a fact at all.