diff --git a/DOCS/superpowers/plans/2026-06-09-spacesh-m4.md b/DOCS/superpowers/plans/2026-06-09-spacesh-m4.md
index b1361b1..58583cf 100644
--- a/DOCS/superpowers/plans/2026-06-09-spacesh-m4.md
+++ b/DOCS/superpowers/plans/2026-06-09-spacesh-m4.md
@@ -275,18 +275,18 @@ pub fn socket_path() -> Result<PathBuf> {
     Ok(spacesh_dir()?.join("sock"))
 }
 ```
-Add a test in `lifecycle.rs` tests module:
+Add a test in `lifecycle.rs` tests module. It mutates the process-global `SPACESH_SOCK`, so it MUST hold `crate::test_support::serial()` for its duration; ALSO add the same guard to the existing `paths_live_under_spacesh_dir` test (the only other test that calls `socket_path()`), or it will intermittently observe the override var and fail:
 ```rust
     #[test]
     fn socket_path_honors_env_override() {
-        // Note: set/remove around the assertion; tests in this module run serially enough,
-        // but guard by restoring afterwards.
+        let _serial = crate::test_support::serial();
         std::env::set_var("SPACESH_SOCK", "/tmp/spacesh-test-override.sock");
         let p = socket_path().unwrap();
         std::env::remove_var("SPACESH_SOCK");
         assert_eq!(p, std::path::PathBuf::from("/tmp/spacesh-test-override.sock"));
     }
 ```
+And prepend `let _serial = crate::test_support::serial();` as the first line of the existing `paths_live_under_spacesh_dir` test.
 
 - [ ] **Step 4: Initialize idle on every spawn; drop on exit; dispatch SetState**