When pnpm Works Locally But Fails in CI: Three Undocumented Traps

pnpm workspaces is the leading solution for TypeScript monorepos, yet its documentation glosses over critical failures that only emerge in real CI environments like Railway. This analysis exposes three undocumented traps—phantom dependencies, version resolution conflicts, and hoisting misconfigurations—that transform stable local development into unpredictable CI failures. Understanding these edge cases is essential for teams deploying pnpm-based monorepos to production.