fixing cancel training

studio/backend/core/training/training.py

@@ -226,6 +226,20 @@ class TrainingBackend:
             )
         return True
 
+    def force_terminate(self) -> None:
+        """Force-kill the training subprocess so state can be reset immediately."""
+        with self._lock:
+            if self._proc is not None and self._proc.is_alive():
+                logger.info("Force-terminating training subprocess (pid=%s)", self._proc.pid)
+                self._proc.terminate()
+            proc = self._proc
+
+        if proc is not None:
+            proc.join(timeout=5.0)
+            if proc.is_alive():
+                proc.kill()
+                proc.join(timeout=2.0)
+
     def is_training_active(self) -> bool:
         """Check if training is currently active."""
         with self._lock:

studio/backend/routes/training.py

@@ -309,11 +309,16 @@ async def reset_training(
         is_active = backend.is_training_active()
 
         if is_active:
-            logger.warning("Rejected reset while training active: is_active=%s", is_active)
-            raise HTTPException(
-                status_code=409,
-                detail="Training is still running. Stop training and wait for it to finish before resetting.",
-            )
+            if backend._should_stop:
+                # Stop was already requested — force-terminate so we can reset immediately
+                logger.info("Force-terminating subprocess for immediate reset")
+                backend.force_terminate()
+            else:
+                logger.warning("Rejected reset while training active: is_active=%s", is_active)
+                raise HTTPException(
+                    status_code=409,
+                    detail="Training is still running. Stop training and wait for it to finish before resetting.",
+                )
 
         logger.info("Reset training state: clearing runtime + metric history")
         backend._should_stop = False  # Clear stop flag so status returns to idle

studio/frontend/src/features/studio/training-start-overlay.tsx

@@ -31,7 +31,7 @@ export function TrainingStartOverlay({
   message,
   currentStep,
 }: TrainingStartOverlayProps): ReactElement {
-  const { stopTrainingRun } = useTrainingActions();
+  const { stopTrainingRun, dismissTrainingRun } = useTrainingActions();
   const isStarting = useTrainingRuntimeStore((s) => s.isStarting);
   const [cancelDialogOpen, setCancelDialogOpen] = useState(false);
   const [cancelRequested, setCancelRequested] = useState(false);
@@ -77,7 +77,11 @@ export function TrainingStartOverlay({
                     setCancelDialogOpen(false);
                     useTrainingRuntimeStore.getState().setStopRequested(true);
                     void stopTrainingRun(false).then((ok) => {
-                      if (!ok) setCancelRequested(false);
+                      if (ok) {
+                        void dismissTrainingRun();
+                      } else {
+                        setCancelRequested(false);
+                      }
                     });
                   }}
                 >

studio/frontend/src/features/training/hooks/use-training-actions.ts

@@ -105,6 +105,12 @@ export function useTrainingActions() {
         }
       }
 
+      // Abort if cancel was requested during dataset check
+      if (useTrainingRuntimeStore.getState().stopRequested) {
+        runtimeStore.setStarting(false);
+        return false;
+      }
+
       // Re-read config after potential store updates from dataset check
       const payload = buildTrainingStartPayload(useTrainingConfigStore.getState());
       const response = await startTraining(payload);