Why AI Coding Agents Silently Break Full-Stack Apps (And How We Solved It in 0.75ms)

A developer has released StackBridge-MCP, an open-source Model Context Protocol server that tracks cross-boundary contracts in full-stack codebases to prevent AI coding agents from silently breaking frontend code. The tool reduces context window size by 99.74% and speeds up blast radius traversal from ~150 ms to 0.75 ms, with all 56 tests passing. It is available via uvx or pip on GitHub and PyPI.

When AI coding agents Cursor, Claude Code, Windsurf edit backend models or API routes in full-stack codebases, backend unit tests frequently pass while the frontend silently breaks in production: backend/routes.py .I built StackBridge-MCP , an open-source Model Context Protocol server that tracks cross-boundary contracts locally without running heavy test VMs. fetch , Axios, React Query ↔ FastAPI routes ↔ SQLAlchemy ORM models without heavy LSP sidecars or runtime imports.Measured on fastapi-realworld-example-app 44 files, 23 AST dependency nodes, 10 cross-boundary edges : | Metric | Raw Codebase Dump | StackBridge Compact Slice | Improvement / Latency | |---|---|---|---| Context Window Size | 19,705 tokens | 51 tokens | 📉 99.74% Token Reduction | Blast Radius Traversal | Full-repo search: ~150 ms | SQLite Recursive CTE: 0.75 ms | ⚡ 200x Faster Traversal | Compiler Verification | Global linter: ~3,500 ms | Baseline-Diffed Engine: 312 ms | 🛡️ Zero False Positives | Automated Tests | — | 56 / 56 passing | ✅ 100% Passing | Run via uvx with zero local configuration: bash uvx stackbridge serve Or install via pip: Bash pip install stackbridge GitHub: https://github.com/ZainUlAbideen02/StackBridge-MCP PyPI: https://pypi.org/project/stackbridge/0.1.0/