Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[Unreleased]

SubType matching is now case-insensitive (BREAKING) — All subType values accepted via the rule and limit APIs are trimmed and normalized to lowercase canonical form before storage and matching. API responses now return subType fields in lowercase. Clients that relied on the original casing in API responses (for display, diffing, or equality checks) must update. Downstream validation requests matching on subType no longer need to preserve caller casing.
Rule and limit lifecycle mutations are now transactional with their audit events (BREAKING) — When a rule or limit lifecycle mutation is requested (create, update, activate, deactivate, draft, delete — including partial PATCH edits via UpdateLimitCommand and Rule.Update), the repository mutation and the corresponding audit_events row now commit atomically inside a single PostgreSQL transaction. Operations that previously succeeded with a warn-logged audit failure now return HTTP 5xx and roll the mutation back, including ordinary field edits that do not change status. The post-commit rule cache update is guarded by a panic-safe closure so cache-layer faults do not convert successful commits into 5xx. Operator run-books that treated audit-failure-as-success must be updated; SOX/GLBA audit-chain integrity is now enforced at the persistence boundary for every write path.

Limit merchant scope enforcement — CheckLimitsInput now propagates MerchantID from ValidationRequest through the limit evaluation pipeline. Limits scoped to a specific merchant are now correctly enforced only on transactions matching that merchant. Previously the merchant identifier was silently dropped, causing scoped limits to either over-enforce (matching all merchants) or under-enforce (matching none), depending on downstream wiring.

This is the first public release of Tracer, a real-time transaction validation and fraud prevention API for financial systems.

Transaction Validation API - Real-time ALLOW/DENY/REVIEW decisions with <80ms p99 latency
Expression-based Rules - Type-safe rule engine using CEL (Common Expression Language)
Flexible Spending Limits - Daily, monthly, and per-transaction limits with scope-based application (account, segment, portfolio, merchant, transaction type)
Complete Audit Trail - SOX/GLBA compliant with hash chain integrity and 7-year retention policy
Rule Management - Create, activate, deactivate, update, and delete validation rules with draft/active status workflow
Limit Management - Configure and manage spending limits with real-time usage tracking
REST API - Comprehensive OpenAPI 3.0 documented endpoints for all operations
Authentication - API key-based authentication with secure key management
PostgreSQL Persistence - Robust data storage with database migrations and connection pooling
Observability - Structured logging with slog, OpenTelemetry tracing, and Prometheus metrics
Health Checks - Liveness and readiness endpoints for orchestration integration
Docker Support - Production-ready containerization with distroless base images

Input validation on all API endpoints with detailed error messages (TRC-* error codes)
SQL injection protection via parameterized queries
TLS 1.2+ enforcement for encrypted communications
Rate limiting and request size constraints (100KB max payload)
Audit trail immutability with PostgreSQL rules preventing UPDATE/DELETE operations
Hash chain integrity for tamper detection in audit logs