diff --git a/api/onnx_web/chain/blend_img2img.py b/api/onnx_web/chain/blend_img2img.py
index 2766bdf1..9078e63c 100644
--- a/api/onnx_web/chain/blend_img2img.py
+++ b/api/onnx_web/chain/blend_img2img.py
@@ -30,12 +30,12 @@ def blend_img2img(
     prompt: str = None,
     **kwargs,
 ) -> Image.Image:
-    logger.info('generating image using img2img, %s steps: %s', params.steps, params.prompt)
+    prompt = prompt or params.prompt
+    logger.info('generating image using img2img, %s steps: %s', params.steps, prompt)
 
     pipe = load_pipeline(OnnxStableDiffusionImg2ImgPipeline,
                             params.model, params.provider, params.scheduler)
 
-    prompt = prompt or params.prompt
     rng = np.random.RandomState(params.seed)
 
     result = pipe(
diff --git a/api/onnx_web/chain/upscale_stable_diffusion.py b/api/onnx_web/chain/upscale_stable_diffusion.py
index a189663d..ddbd156e 100644
--- a/api/onnx_web/chain/upscale_stable_diffusion.py
+++ b/api/onnx_web/chain/upscale_stable_diffusion.py
@@ -67,9 +67,11 @@ def upscale_stable_diffusion(
     source: Image.Image,
     *,
     upscale: UpscaleParams,
+    prompt: str = None,
     **kwargs,
 ) -> Image.Image:
-    logger.info('upscaling with Stable Diffusion')
+    prompt = prompt or params.prompt
+    logger.info('upscaling with Stable Diffusion, %s steps: %s', params.steps, prompt)
 
     pipeline = load_stable_diffusion(ctx, upscale)
     generator = torch.manual_seed(params.seed)
diff --git a/api/onnx_web/serve.py b/api/onnx_web/serve.py
index ac9ab487..de8b82b6 100644
--- a/api/onnx_web/serve.py
+++ b/api/onnx_web/serve.py
@@ -72,6 +72,7 @@ from .utils import (
     get_from_list,
     get_from_map,
     get_not_empty,
+    get_size,
     make_output_name,
     base_join,
     ServerContext,
@@ -577,8 +578,8 @@ def chain():
 
         stage = StageParams(
             stage_data.get('name', callback.__name__),
-            tile_size=int(kwargs.get('tile_size', SizeChart.auto)),
-            outscale=int(kwargs.get('outscale', 1)),
+            tile_size=get_size(kwargs.get('tile_size')),
+            outscale=get_and_clamp_int(kwargs,'outscale', 1, 4),
         )
 
         # TODO: create Border from border
diff --git a/api/onnx_web/utils.py b/api/onnx_web/utils.py
index c35bf735..64c0be9d 100644
--- a/api/onnx_web/utils.py
+++ b/api/onnx_web/utils.py
@@ -3,12 +3,13 @@ from logging import getLogger
 from os import environ, path
 from struct import pack
 from time import time
-from typing import Any, Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional, Union, Tuple
 
 from .params import (
     ImageParams,
     Param,
     Size,
+    SizeChart,
 )
 
 logger = getLogger(__name__)
@@ -92,6 +93,22 @@ def get_not_empty(args: Any, key: str, default: Any) -> Any:
     return val
 
 
+def get_size(val: Union[int, str, None]) -> SizeChart:
+    if val is None:
+        return SizeChart.auto
+
+    if type(val) is str:
+        if val in SizeChart:
+            return SizeChart[val]
+        else:
+            return int(val)
+
+    if type(val) is int:
+        return val
+
+    raise Exception('invalid size')
+
+
 def hash_value(sha, param: Param):
     if param is None:
         return
diff --git a/common/pipelines/example.json b/common/pipelines/example.json
index 85dc6475..f059c599 100644
--- a/common/pipelines/example.json
+++ b/common/pipelines/example.json
@@ -23,13 +23,15 @@
         "prompt": "a magical wizard in a robe fighting a dragon",
         "scale": 4,
         "outscale": 4,
-        "tile_size": 128
+        "tile_size": "mini"
       }
     },
     {
       "name": "save-local",
       "type": "persist-disk",
-      "params": {}
+      "params": {
+        "tile_size": "8k"
+      }
     },
     {
       "name": "save-ceph",
@@ -37,7 +39,8 @@
       "params": {
         "bucket": "storage-stable-diffusion",
         "endpoint_url": "http://scylla.home.holdmyran.ch:8000",
-        "profile_name": "ceph"
+        "profile_name": "ceph",
+        "tile_size": "8k"
       }
     }
   ]