Worked on the envoyproxy/ai-gateway repository to deliver per-backend header forwarding for MCPRouteBackendRef, enabling selective client header passthrough to explicitly opted-in MCP servers with optional header renaming. Designed a two-level header forwarding model at both route and backend levels to maintain backward compatibility while supporting additive per-backend behavior. Implemented comprehensive changes across the CRD, internal API, controller, proxy, and documentation, using Go and Kubernetes for backend development. Added extensive unit and integration tests, validating the feature with live deployments. This work improved security by ensuring headers are only forwarded to authorized backends, reducing reliance on OAuth-based authentication.