fix(callbacks): take only a pil image in step callback kwargs as a preview

sd and sdxl txt2img controlnet pipelines pass their control tensors as image; the callback took them as a preview and returned before the interrupt check.

CHANGELOG.md

@@ -39,6 +39,7 @@
   - control: controlnet with *init image same as control* uses the unit's processed image
   - control: multiple units on controlnet-union
   - control: t2i-adapter, controlnet-xs and controllite model lists follow the loaded model type
+  - control: live preview and interrupt for sd and sdxl controlnet without an init image
 
 ## Update for 2026-10-01
 

modules/processing_callbacks.py

@@ -2,6 +2,7 @@ import os
 import time
 import torch
 import numpy as np
+from PIL import Image
 from modules import shared, devices, processing_correction, timer, prompt_parser_diffusers
 from modules.logger import log
 from modules.attention import context as attention_context
@@ -83,7 +84,7 @@ def diffusers_callback(pipe, step: int = 0, timestep: int = 0, kwargs: dict | No
             time.sleep(0.1)
 
     image = kwargs.get('image', None)
-    if image is not None:
+    if isinstance(image, Image.Image): # decoded preview; controlnet pipelines pass control tensors as image
         shared.state.current_image = image
         shared.state.current_latent = None
         shared.state.step() # increase step