Single-repository quality gates are blind to distributed system failures. A pull request that changes a REST endpoint signature can pass all local CI checks and unit tests while silently breaking three downstream consumer services in other repositories — failures that remain invisible until deployment. This paper presents the K11tech Microservice QA System (k11techlab-microservice-qa-system), a LangGraph-orchestrated agentic pipeline that extends single-repository quality assurance to distributed microservice systems by maintaining a cross-repository view of API contracts and service dependencies. The system extracts versioned API contracts from pull requests (OpenAPI 3.x, gRPC Protocol Buffers, GraphQL), stores them in a persistent Contract Registry MCP server, traverses a directed dependency graph to identify all downstream consumers of changed endpoints, and dispatches parallel ContractComplianceAgents to validate each consumer's compatibility before any code is merged. A cross-repository human-in-the-loop gate triggers on impact score thresholds and files GitHub issues in both the provider and consumer repositories when breaking changes are detected. Evaluation across two phases totalling 74 real-world pull requests demonstrates 100% precision, recall, and F1: Phase A achieves 100% P/R/F1 on 15 controlled scenarios across four k11techlab services across three pipeline tiers (diff-only, graph+diff, and LLM-validated), and Phase B achieves 100% P/R/F1 on 59 external OSS pull requests across four open-source repositories with zero false positives. Multi-model ablation identifies Claude Haiku 4.5 as the optimal backend: 31% faster than Sonnet 4.6 (8.9s vs 12.9s mean latency) and the only model achieving 100% accuracy on ambiguous consumer-impact scenarios. The system is open source and deployable alongside the K11tech Agentic AI QA System for Single-Repo QA Pipeline (k11techlab-agentic-ai-qa-system) as a complementary cross-repository quality gate.
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Kavita Jadhav (2026) studied this question.