Credit Gate Stops Trial Balance Races

The important idea is treating credit checks as reservations, not read-only balance queries.

• –Atomic database writes close the check-then-act race that lets concurrent requests consume the same allowance.
• –Stable request keys make retries replayable instead of charging twice, a pattern demonstrated by similar SQLite idempotency labs ([GitHub](https://github.com/fabioffigueiredo/agent-retry-idempotency-lab)).
• –Uncertain outcomes should remain unresolved rather than triggering blind retries; comparable credit systems settle reservations after work completes ([Schematic](https://github.com/SchematicHQ/schematic-python)).
• –SQLite is a strong local teaching and prototype substrate, but distributed deployments still need provider-side idempotency, reconciliation, and durable operational controls ([Allerin](https://www.allerin.com/resources/agentic-ai-guardrails-evals-hitl)).