2026-01 Monthly Summary — tanstack/router Key deliverable: Server Function Error Handling Middleware for tanstack/router. Implemented a middleware layer that catches and transforms errors thrown by server function handlers, enabling consistent error responses and easier debugging across the server-to-client boundary. Major bugs fixed: Ensured middleware can catch server function handler errors, wiring through to client-facing error handling. This work is captured in commit 02839b313234ab3a1b8175c74a07ab087b38ac61, which fixes (#6392) and (#6381). Impact and accomplishments: Increased reliability and maintainability of error handling in server-function workflows. Provides unified error formats for downstream consumers, improved telemetry, and faster troubleshooting. Demonstrates end-to-end pipeline improvements within the tanstack/router repository. Technologies/skills demonstrated: Middleware design patterns, error handling and transformation, server function integration, cross-layer coordination, and commit-level traceability within a modern JavaScript/TypeScript codebase.