During June 2025, Bitprobe enhanced error handling in the fastify/fastify repository by aligning TypeScript error definitions with actual runtime errors. They addressed missing error codes in the errors.d.ts file and introduced corresponding tests in errors.test.js to verify type and runtime consistency. This work, implemented using TypeScript and JavaScript, focused on reducing discrepancies between type definitions and runtime behavior, thereby improving type safety for downstream users. By ensuring that error codes are accurately reflected in both type and runtime layers, Bitprobe contributed to a more stable and predictable developer experience, addressing potential regressions related to error handling in future releases.