diff --git a/crates/engine/src/cmd/edit.rs b/crates/engine/src/cmd/edit.rs
index aaf44a7..4b2dc2d 100644
--- a/crates/engine/src/cmd/edit.rs
+++ b/crates/engine/src/cmd/edit.rs
@@ -33,7 +33,17 @@ pub fn specs() -> Vec<CommandSpec> {
     ]
 }
 
+/// A programmatic undo/redo (`engine.execute`, MCP, control channel, scripts) first ends a running
+/// command the way Esc does, exactly as `Session::start` does for Cmd+Z, the menu or the command
+/// line. Otherwise it would swap the drawing under the command and pop the previous command's step.
+fn end_running_command(s: &mut Session) {
+    if s.running.is_some() {
+        s.cancel();
+    }
+}
+
 fn run_undo(s: &mut Session, p: &Value) -> Result<Value> {
+    end_running_command(s);
     let n = p.get("count").and_then(Value::as_u64).unwrap_or(1).clamp(1, 1000);
     let mut labels = Vec::new();
     for _ in 0..n {
@@ -49,6 +59,7 @@ fn run_undo(s: &mut Session, p: &Value) -> Result<Value> {
 }
 
 fn run_redo(s: &mut Session, p: &Value) -> Result<Value> {
+    end_running_command(s);
     let n = p.get("count").and_then(Value::as_u64).unwrap_or(1).clamp(1, 1000);
     let mut labels = Vec::new();
     for _ in 0..n {
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index 8296141..934954e 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -34,6 +34,28 @@ fn line_undo_option_and_aliases() {
     assert!(s.running.is_none());
 }
 
+#[test]
+fn programmatic_undo_during_a_command_ends_it_first() {
+    let mut s = Session::new();
+    s.execute("line", &json!({"points": [[0, 0], [10, 0]]})).unwrap();
+    // TEXT stays active, waiting for the next line.
+    s.script("TEXT 0,0 5 0 HELLO\n").unwrap();
+    assert!(s.running.is_some());
+    assert_eq!(kinds(&s), vec!["Line", "Text"]);
+    // Like Ctrl+Z during a command: end it (as Esc does), then undo it, not the line.
+    s.execute("undo", &json!({})).unwrap();
+    assert!(s.running.is_none());
+    assert_eq!(kinds(&s), vec!["Line"]);
+    s.execute("redo", &json!({})).unwrap();
+    assert_eq!(kinds(&s), vec!["Line", "Text"]);
+    // Redo while a command runs ends it the same way and leaves the drawing alone.
+    s.script("TEXT 0,-10 5 0\n").unwrap();
+    assert!(s.running.is_some());
+    s.execute("redo", &json!({})).unwrap();
+    assert!(s.running.is_none());
+    assert_eq!(kinds(&s), vec!["Line", "Text"]);
+}
+
 #[test]
 fn polar_and_direct_distance() {
     let mut s = Session::new();