Introduction

OpenAPI Drift Guard helps you catch breaking changes between OpenAPI/Swagger specs and implementation code before they reach production.

The Problem

API specs and implementation code drift apart:

• Missing endpoints in code
• Extra undocumented endpoints
• Schema mismatches
• Parameter type changes

The Solution

Three-layer validation:

1. Spec Parsing — Parse OpenAPI/Swagger into normalized endpoints
2. Code Analysis — Extract routes from Express/Fastify/Koa/NestJS
3. Drift Detection — Compare spec vs code, classify severity

Severity Levels

Level	Meaning
🔴 Breaking	Will break clients
🟡 Warning	May cause issues
🟢 Info	Non-breaking