fix(v9): 5 bugs — GUI deferred until VST loaded (no white window), fixed retry 8x500ms, VST3 folder resolve for auto-load, sustain-CC64 dropped after STOP, taskkill process tree on exit, Synth+GUI same row in TCP

src-tauri/src/lib.rs

@@ -48,20 +48,31 @@ fn kill_bridge(app: &AppHandle) -> bool {
         Err(_) => return false,
     };
     match guard.take() {
-        Some(child) => match child.kill() {
-            Ok(()) => {
+        Some(child) => {
+            let ok = kill_process_tree(&child) || child.kill().is_ok();
+            if ok {
                 println!("Native Host Bridge killed (restart)");
-                true
+            } else {
+                println!("Bridge kill failed");
             }
-            Err(e) => {
-                println!("Bridge kill failed: {e}");
-                false
-            }
-        },
+            ok
+        }
         None => false,
     }
 }
 
+/// Kill a child plus its whole process tree via taskkill /T /F. The engine
+/// (PyInstaller ONEDIR) and bridge are direct children, but /T guarantees no
+/// orphan subprocess stays behind when the DAW window closes.
+fn kill_process_tree(child: &CommandChild) -> bool {
+    let pid = child.pid();
+    std::process::Command::new("taskkill")
+        .args(["/PID", &pid.to_string(), "/T", "/F"])
+        .status()
+        .map(|s| s.success())
+        .unwrap_or(false)
+}
+
 /// Audio frame pushed to the WebView (bridge SHM -> `bridge-audio` event).
 #[derive(Clone, serde::Serialize)]
 struct AudioFrame {
@@ -479,6 +490,7 @@ pub fn run() {
                     .ok()
                     .and_then(|mut lock| lock.take());
                 if let Some(child) = child {
+                    kill_process_tree(&child);
                     let _ = child.kill();
                     println!("daw_engine sidecar terminated.");
                 }
@@ -490,6 +502,7 @@ pub fn run() {
                     .ok()
                     .and_then(|mut lock| lock.take());
                 if let Some(child) = bridge_child {
+                    kill_process_tree(&child);
                     let _ = child.kill();
                     println!("daw_vst_bridge sidecar terminated.");
                 }