parameterized config mismatch in Firebase Functions v4 between emulator and production deployment

Firebase Functions v4 introduces parameterized configuration via defineString, defineInt, and defineSecret, which supersedes the legacy functions.config() API. A function configured with defineString('MY_VAR') may execute successfully in the local emulator when a corresponding .env entry exists, but production deployment fails if the parameter is not explicitly set via firebase functions:config:set or Cloud Secret Manager. This discrepancy creates a validation gap where local development masks configuration omissions that become blocking errors in CI/CD pipelines. Additionally, TypeScript implementations of params.MY_VAR.value() exhibit environment-dependent return types, with locally available string | undefined contrasting with production behavior that may throw on undefined values when the parameter is unmarked as optional.

What mechanisms does the Firebase CLI use to enforce parameter presence during production deployment that the emulator omits? How should teams refactor existing functions.config() call sites to align with v4 declaration requirements without introducing runtime branching? Is there a recommended pattern to synchronize local .env configuration with production parameter declarations across monorepo function boundaries?