fix(azure_ai): encode mid-position reference streams from offset 0

a seekable stream read from its current cursor shipped truncated base64
that azure rejected; read from offset 0 to match how httpx rewinds
multipart parts

litellm/llms/azure_ai/image_edit/flux2_transformation.py

@@ -1,6 +1,5 @@
 import base64
 from collections.abc import Mapping, Sequence
-from io import BufferedReader
 from types import MappingProxyType
 from typing import Any, Final
 
@@ -123,12 +122,11 @@ class AzureFoundryFlux2ImageEditConfig(OpenAIImageEditConfig):
 
     def _convert_image_to_base64(self, image: Any) -> str:
         """Convert image file to base64 string"""
-        if isinstance(image, BufferedReader):
-            image_bytes = image.read()
-            image.seek(0)  # Reset file pointer for potential reuse
-        elif isinstance(image, bytes):
+        if isinstance(image, bytes):
             image_bytes = image
         elif hasattr(image, "read"):
+            if image.seekable():
+                image.seek(0)
             image_bytes = image.read()
         else:
             raise ValueError(f"Unsupported image type: {type(image)}")

tests/unit/llms/azure_ai/image_edit/test_azure_ai_image_edit_transformation.py

@@ -3,6 +3,7 @@ import json
 import struct
 import zlib
 from collections.abc import Mapping
+from io import BytesIO
 from typing import Final
 
 import httpx
@@ -184,6 +185,22 @@ def test_flux2_image_edit_preserves_controls_and_pixel_cost(dimensions: Mapping[
     assert response._hidden_params["response_cost"] == pytest.approx(catalog_rate * 2048 * 1024 * 2)
 
 
+def test_flux2_image_edit_encodes_a_mid_position_stream_from_the_start():
+    stream: Final = BytesIO(b"prefix" + b"image")
+    stream.seek(6)
+
+    request, files = AzureFoundryFlux2ImageEditConfig().transform_image_edit_request(
+        model="FLUX.2-flex",
+        prompt="Blend every reference",
+        image=[stream],
+        image_edit_optional_request_params={},
+        litellm_params={},
+        headers={},
+    )
+
+    assert request["input_image"] == base64.b64encode(b"prefiximage").decode()
+
+
 def _png_bytes(width: int, height: int) -> bytes:
     """Smallest well-formed PNG carrying real IHDR dimensions."""