Technically, xref in AOSP raises interesting trade-offs. A comprehensive index must balance completeness against noise. Naive cross-referencing that surfaces every textual match will overwhelm; smarter systems require semantic awareness — symbol resolution, build-context sensitivity, and knowledge of generated artifacts. They must understand the build graph so references point not just to source files, but to the concrete artifact and configuration that matter at runtime. Performance matters too: a developer’s flow is broken if queries take minutes. So, engineering choices around incremental updates, caching, and language-aware parsers shape adoption.