Designing a metadata-centric failure contract for distributed Rust environments. When people introduce a new Rust project, they usually begin with networking, storage, async orchestration, or protocol design. I didn’t. The first crate I put into NEXUS was an error-handling crate: nx-error (and its companion nx-error-macros ). That choice was not aesthetic. It was architectural. NEXUS is built around service boundaries, typed contracts, and execution environments where failures need to be represented consistently across layers. This post is the first in a series about the technical foundations of NEXUS. It explains why I built nx-error , what problems it was designed to solve, and which trade-offs mattered most: typed metadata, context separation, predictable propagation, and WASM-conscious ergonomics. A quick look at the API The surface API is intentionally small. The goal was to make domain errors easy to define, but also useful to downstream systems: HTTP layers, logs, metrics, dashboards, and operators.…