Tenant isolation is a database rule, not a convention.
The product architecture uses tenant-scoped database sessions, row-level security on public tables, and per-transaction tenant/entity context. The design goal is that every tenant-scoped query is forced through the same isolation path.
Posted accounting data is immutable.
Once accounting data is posted, the intended correction path is reversal or adjustment. Silent mutation of posted entries is treated as a product defect because accounting systems need forensic history.
Reasoning and audit events are correlated.
Agent decisions write a reasoning log. Posting events carry the reasoning reference into the audit payload so a later reviewer can connect what was approved, why it was approved, and what changed in the books.
External approvals use signed, expiring tokens.
Channel approvals are designed around HMAC-signed, single-use, expiring HITL tokens so a user can approve from email or another channel without exposing the whole app session.