diff --git a/backend/python/diffusers/backend.py b/backend/python/diffusers/backend.py
index 00b292292..0299b9b4c 100755
--- a/backend/python/diffusers/backend.py
+++ b/backend/python/diffusers/backend.py
@@ -864,8 +864,13 @@ class BackendServicer(backend_pb2_grpc.BackendServicer):
                 **kwargs
             ).images[0]
 
-        # save the result
-        image.save(request.dst)
+        # save the result. Save as PNG explicitly instead of letting Pillow
+        # infer the encoder from the extension: the core passes an absolute
+        # staging path ending in .tmp (e.g. /staging/localai-output-*.tmp),
+        # which Pillow can't map to a format and would raise
+        # "unknown file extension: .tmp". LocalAI serves generated images as
+        # PNG regardless of the temp path.
+        image.save(request.dst, format="PNG")
 
         return backend_pb2.Result(message="Media generated", success=True)
 
diff --git a/backend/python/tinygrad/backend.py b/backend/python/tinygrad/backend.py
index bb09e9e49..fa643568c 100644
--- a/backend/python/tinygrad/backend.py
+++ b/backend/python/tinygrad/backend.py
@@ -670,7 +670,10 @@ class BackendServicer(backend_pb2_grpc.BackendServicer):
             arr = img_tensor.numpy()
             image = Image.fromarray(arr)
             dst = request.dst or os.path.join(tempfile.gettempdir(), "tinygrad_image.png")
-            image.save(dst)
+            # Force PNG rather than letting Pillow guess from the extension: the
+            # core passes a staging path ending in .tmp, which Pillow can't map
+            # to a format ("unknown file extension: .tmp").
+            image.save(dst, format="PNG")
             return backend_pb2.Result(success=True, message=dst)
         except Exception as exc:
             import traceback
diff --git a/backend/python/vllm-omni/backend.py b/backend/python/vllm-omni/backend.py
index e03c6c6d4..c0e47b25a 100644
--- a/backend/python/vllm-omni/backend.py
+++ b/backend/python/vllm-omni/backend.py
@@ -337,9 +337,11 @@ class BackendServicer(backend_pb2_grpc.BackendServicer):
             if not images or len(images) == 0:
                 return backend_pb2.Result(success=False, message="Empty images list")
 
-            # Save image
+            # Save image. Force PNG rather than letting Pillow guess from the
+            # extension: the core passes a staging path ending in .tmp, which
+            # Pillow can't map to a format ("unknown file extension: .tmp").
             output_image = images[0]
-            output_image.save(request.dst)
+            output_image.save(request.dst, format="PNG")
             return backend_pb2.Result(message="Image generated successfully", success=True)
 
         except Exception as err: