add explicit sync for vae preview

Signed-off-by: Vladimir Mandic <mandic00@live.com>

CHANGELOG.md

@@ -167,6 +167,7 @@ Highlight are:
   - fix hf token with extra chars  
   - image viewer refocus on gallery after returning from full screen mode  
   - fix attention guidance metadata save/restore  
+  - vae preview add explicity cuda.sync  
 
 ## Update for 2025-09-15
 

modules/processing_callbacks.py

@@ -56,7 +56,7 @@ def diffusers_callback(pipe, step: int = 0, timestep: int = 0, kwargs: dict = {}
     t0 = time.time()
     if devices.backend == "ipex": # xe driver on linux needs this
         torch.xpu.synchronize(devices.device)
-    elif devices.backend == "zluda" or (devices.backend == "rocm" and sys.platform == "win32"):
+    elif (devices.backend == "zluda") or (devices.backend == "rocm") or (devices.backend == "cuda"):
         torch.cuda.synchronize(devices.device)
     latents = kwargs.get('latents', None)
     if debug: