@rough-minister-58256 : according to

$ git diff -- src/rust/engine/src/lib.rs
diff --git a/src/rust/engine/src/lib.rs b/src/rust/engine/src/lib.rs
index 408ba35..f8e6505 100644
--- a/src/rust/engine/src/lib.rs
+++ b/src/rust/engine/src/lib.rs
@@ -272,6 +272,7 @@ pub extern fn scheduler_post_fork(scheduler_ptr: *mut RawScheduler) {
 pub extern fn scheduler_destroy(scheduler_ptr: *mut RawScheduler) {
   // convert the raw pointer back to a Box (without `forget`ing it) in order to cause it
   // to be destroyed at the end of this function.
+  println!(">>> destroying the scheduler.");
   let _ = unsafe { Box::from_raw(scheduler_ptr) };
 }

... a normal run will not destroy the scheduler before exiting