BetterAuth expects Web API Request objects (Fetch API standard) with headers.get(), but NestJS/Express passes IncomingMessage objects with headers[] property access. Use better-auth/node's toNodeHandler to properly convert between Express req/res and BetterAuth's Web API handler. Also fixes vitest SWC config to read the correct tsconfig for NestJS decorator metadata emission, which was causing DI injection failures in tests. Fixes #410 Co-Authored-By: Claude Opus 4.6 <[email protected]>