diff --git a/crates/engine/src/devinspect.rs b/crates/engine/src/devinspect.rs
index 16f4bbdc..8d9b1e2e 100644
--- a/crates/engine/src/devinspect.rs
+++ b/crates/engine/src/devinspect.rs
@@ -224,9 +224,11 @@ pub struct DevItem {
 /// Revert to saved, which isn't an undo step but throws the design's unsaved edits away.
 pub fn dev_mode_allows(id: &str) -> bool {
     const OWN: [&str; 5] = ["annotation.", "dev.", "devResource.", "codeConnect.", "comment."];
+    // Edits recorded as one grouped undo step, so their spec says no history of its own.
+    const GROUPED: [&str; 1] = ["data.fill"];
     match id.strip_prefix("tool.") {
         Some(t) => matches!(t, "move" | "hand" | "comment"),
-        None if id == "file.revert" => false,
+        None if id == "file.revert" || GROUPED.contains(&id) => false,
         None => OWN.iter().any(|p| id.starts_with(p)) || crate::cmd::find_command(id).is_none_or(|c| !c.history),
     }
 }
diff --git a/crates/engine/src/devmode_behaviour_tests.rs b/crates/engine/src/devmode_behaviour_tests.rs
index 3d85fdb1..38d1a9fb 100644
--- a/crates/engine/src/devmode_behaviour_tests.rs
+++ b/crates/engine/src/devmode_behaviour_tests.rs
@@ -124,6 +124,7 @@ fn dev_mode_runs_its_own_edits_and_refuses_design_edits_from_menus_and_shortcuts
         "tool.place",
         "file.import",
         "file.revert",
+        "data.fill",
     ] {
         assert!(!dev_mode_allows(id), "{id} edits the design");
     }