diff --git a/src/app/config.rs b/src/app/config.rs
index b22e28e70..6d1c8f0eb 100644
--- a/src/app/config.rs
+++ b/src/app/config.rs
@@ -460,7 +460,16 @@ impl AppConfig {
 
     /// Persist the config as JSON. Best-effort; silent on unavailable or
     /// read-only storage.
+    ///
+    /// Does nothing under `cfg(test)`. The path is the developer's own
+    /// settings file, and the suite builds whole applications and changes
+    /// preferences on them — without this, running `cargo test` rewrites the
+    /// settings of whoever ran it.
     pub fn save(&self) {
+        if cfg!(test) {
+            return;
+        }
+
         #[cfg(not(target_arch = "wasm32"))]
         {
             let Some(path) = config_path() else { return };
diff --git a/src/app/mod.rs b/src/app/mod.rs
index 9269c3b3d..eef45d546 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -3856,7 +3856,16 @@ impl OpenCADStudio {
 
     #[cfg(test)]
     pub(crate) fn new_for_test() -> Self {
-        Self::new()
+        let mut app = Self::new();
+        // `new` loads the real settings file, so without this every test runs
+        // against whatever the developer last set in the application — a suite
+        // that passes on a clean machine and fails on a used one. It surfaced
+        // when a persisted `GRIPOBJLIMIT` made the grip-limit test see 32767
+        // where it expected the default, and the number of persisted settings
+        // only grows.
+        app.apply_config(crate::app::config::AppConfig::default());
+        app.last_saved_config = Some(app.current_config());
+        app
     }
 
     /// Install `cmd` as the active interactive command for tab `tab`.