diff --git a/backend/tests/wm_token_workspace_confinement.rs b/backend/tests/wm_token_workspace_confinement.rs
index 4dc379af3f..2e9957eb4f 100644
--- a/backend/tests/wm_token_workspace_confinement.rs
+++ b/backend/tests/wm_token_workspace_confinement.rs
@@ -250,5 +250,28 @@ async fn test_wm_token_is_confined_to_its_workspace(db: Pool<Postgres>) -> anyho
         resp.text().await?
     );
 
+    // 9. ...and the one write it keeps: the resource editor's object-storage "Test
+    //    connection" runs as a preview job that POSTs its config here. The route only
+    //    exists under `parquet`; without it every status would be a 404 and the
+    //    assertion would hold for the wrong reason. The body is deliberately not a
+    //    valid `ObjectSettings` — what matters is that the request reaches the
+    //    handler's own extractors (422) rather than the confinement guard.
+    #[cfg(feature = "parquet")]
+    {
+        let resp = authed(
+            client().post(format!("{api}/settings/test_object_storage_config")),
+            &user_wm,
+        )
+        .json(&json!({}))
+        .send()
+        .await?;
+        assert_ne!(
+            resp.status(),
+            403,
+            "WM_TOKEN must still reach the object-storage connection test: {}",
+            resp.text().await?
+        );
+    }
+
     Ok(())
 }
diff --git a/backend/windmill-api-auth/src/scopes.rs b/backend/windmill-api-auth/src/scopes.rs
index 937064067e..be19966532 100644
--- a/backend/windmill-api-auth/src/scopes.rs
+++ b/backend/windmill-api-auth/src/scopes.rs
@@ -892,11 +892,11 @@ fn scope_grants_access(
     Ok(true)
 }
 
-/// The workspace-less routes a job token (`$WM_TOKEN`) may still reach: each returns
+/// The workspace-less routes a job token (`$WM_TOKEN`) may still read: each returns
 /// only the caller's own identity or content identical for every workspace (the Hub
 /// proxy, the documentation). Read methods only — a mutating handler added on one of
 /// these paths must be reconsidered rather than inherit the grant.
-fn is_global_route_open_to_job_token(route_path: &str) -> bool {
+fn is_global_read_open_to_job_token(route_path: &str) -> bool {
     matches!(
         route_path,
         "/api/users/whoami"
@@ -909,6 +909,13 @@ fn is_global_route_open_to_job_token(route_path: &str) -> bool {
         || route_path.starts_with("/api/apps/hub/")
 }
 
+/// The one write a job token keeps. A resource editor's "Test connection" for an
+/// object-storage resource runs as a preview job that POSTs the storage config here
+/// (`TestConnection.svelte`), so this must stay reachable. The handler probes only the
+/// configuration in the request body and persists nothing, so it reads no state
+/// belonging to another workspace.
+const OBJECT_STORAGE_TEST_ROUTE: &str = "/api/settings/test_object_storage_config";
+
 /// Confines a job token (`$WM_TOKEN`) to routes that name a workspace. It is minted
 /// for one job in one workspace yet carries that job's full user privileges, so on an
 /// instance-wide route it would mint a permanent workspace-less API token, read
@@ -920,8 +927,9 @@ fn is_global_route_open_to_job_token(route_path: &str) -> bool {
 /// deliberately publishes instance-wide tools. Callers pass only routes whose path
 /// carries no workspace.
 pub fn check_job_token_for_global_route(route_path: &str, http_method: &str) -> Result<()> {
-    if map_http_method_to_action(http_method, route_path) == ScopeAction::Read
-        && is_global_route_open_to_job_token(route_path)
+    let is_read = map_http_method_to_action(http_method, route_path) == ScopeAction::Read;
+    if (is_read && is_global_read_open_to_job_token(route_path))
+        || (http_method.eq_ignore_ascii_case("POST") && route_path == OBJECT_STORAGE_TEST_ROUTE)
     {
         Ok(())
     } else {