Allowing an LLM or AI agent to write directly to your production PostgreSQL database is an operational catastrophe waiting to trigger. Even with 99% accuracy, one hallucinated invoice total or inverted credit/debit will corrupt your double-entry trial balance.
The Core Architecture: Two Distinct Layers
Layer 1: The Model Proposes. The AI extracts invoice fields, parses PDF tables, or drafts inventory transfers into an uncommitted `staging_proposals` table. Layer 2: Deterministic Code Validates. A Python/TypeScript service executes strict mathematical reconciliation, foreign key checks, and duplicate detection. If all pass, the row commits. If any check fails, the record routes to a human review queue with the exact assertion error highlighted.