When configuration has multiple sources (env vars, CLI flags, socket overrides) and/or platform-specific test compilation, treat only the *effective* configuration as authoritative. Apply this standard: - Precedence first: codify which source wins (e.g., CLI `--session` > `HERDR_SESSION` unless `HERDR_SOCKET_PATH` overrides socket selection). - Validate conditionally: only validate/parse config values if they will actually be used. Don’t fail early on values that are overridden. - Lock it with tests: add regression tests for precedence edge cases. - Platform gating: if a module is already compile-gated for a target, avoid redundant per-test `#[cfg]`; if needed, gate at the narrowest helper/function scope. Example (precedence regression shape): ```rust // If no explicit --session is provided and HERDR_SOCKET_PATH is set, // skip HERDR_SESSION validation because it is not authoritative. #[test] fn socket_path_wins_over_invalid_session_env() { std::env::set_var("HERDR_SOCKET_PATH", "/tmp/herdr.sock"); std::env::set_var("HERDR_SESSION", "bad/name"); // invoke: `herdr workspace list` (or the function that reads config) // assert: command proceeds (no validation error), and uses /tmp/herdr.sock } ``` This prevents confusing failures from overridden settings and keeps tests compiling cleanly across platforms.