Cross-Repository Contract Testing and Change Impact Analysis in Microservice CI/CD: An Agentic AI Approach
Single-repository quality gates are blind to API contract violations across microservice boundaries: a pull request that changes a REST endpoint can pass all local CI checks while silently breaking downstream consumer services in other repositories. This paper presents the K11tech Microservice QA System, a LangGraph-orchestrated agentic pipeline that extends CI/CD quality assurance to distributed microservice ecosystems. The system maintains a cross-repository dependency graph, extracts versioned API contracts from pull requests (OpenAPI 3.x, gRPC Protocol Buffers, GraphQL, and AsyncAPI 2.x), identifies all downstream consumers of changed endpoints, and dispatches parallel ContractComplianceAgents to validate compatibility before merge. A cross-repository HITL gate triggers on impact score thresholds, filing GitHub issues in both provider and consumer repositories when breaking changes are detected. Evaluation across four phases (90 scenarios) achieves 100% precision, recall, and F1 throughout, including external validation on 59 OSS pull requests across four repositories with zero false positives and transitive consumer discovery at depth-2. Multi-model ablation identifies Claude Haiku 4.5 as the optimal backend: 31% faster than Sonnet 4.6 (8.9 s vs. 12.9 s) while maintaining perfect accuracy on ambiguous consumer-impact scenarios. The system is publicly available under the Apache 2.0 licence.