fix(images): return 400 when /images/edits omits image

aimage_edit required a positional image, so the proxy returned HTTP 500
with a raw TypeError when multipart files were absent. Make image optional
and raise BadRequestError so OpenAI-compatible clients get HTTP 400.

Fixes #42185

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

litellm/images/main.py

@@ -965,9 +965,9 @@ def image_edit(
 
 @client
 async def aimage_edit(
-    image: FileTypes | list[FileTypes],
-    model: str,
-    prompt: str,
+    image: FileTypes | list[FileTypes] | None = None,
+    model: str | None = None,
+    prompt: str | None = None,
     mask: str | None = None,
     n: int | None = None,
     quality: str | ImageGenerationRequestQuality | None = None,
@@ -999,10 +999,24 @@ async def aimage_edit(
         loop: Final = asyncio.get_event_loop()
         kwargs["async_call"] = True
 
+        if image is None or (isinstance(image, list) and len(image) == 0):
+            message = "Missing required parameter: 'image'."
+            raise litellm.BadRequestError(
+                message=message,
+                model=model or "unknown",
+                llm_provider=custom_llm_provider or "openai",
+                body={
+                    "message": message,
+                    "type": "invalid_request_error",
+                    "param": "image",
+                    "code": "missing_required_parameter",
+                },
+            )
+
         # get custom llm provider so we can use this for mapping exceptions
         if custom_llm_provider is None:
             _, custom_llm_provider, _, _ = litellm.get_llm_provider(
-                model=model, api_base=local_vars.get("base_url", None)
+                model=model or DEFAULT_IMAGE_ENDPOINT_MODEL, api_base=local_vars.get("base_url", None)
             )
 
         images: Final = image if isinstance(image, list) else [image]

tests/test_litellm/images/test_aimage_edit_missing_image.py

@@ -0,0 +1,64 @@
+"""Regression tests for https://github.com/BerriAI/litellm/issues/42185
+
+POST /v1/images/edits without a multipart `image` used to TypeError inside
+aimage_edit (required positional arg) and surface as HTTP 500. A missing client
+field must be BadRequestError 400.
+"""
+
+from collections.abc import Mapping
+
+import pytest
+
+import litellm
+from litellm.images.main import aimage_edit
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "kwargs",
+    [
+        {"model": "openai/gpt-image-1", "prompt": "add a hat"},
+        {"model": "openai/gpt-image-1", "prompt": "add a hat", "image": None},
+        {"model": "openai/gpt-image-1", "prompt": "add a hat", "image": []},
+    ],
+    ids=["omitted", "none", "empty_list"],
+)
+async def test_aimage_edit_missing_image_raises_bad_request(kwargs: Mapping[str, object]) -> None:
+    with pytest.raises(litellm.BadRequestError) as exc_info:
+        await litellm.aimage_edit(**kwargs)
+
+    err = exc_info.value
+    message = str(err)
+    assert err.status_code == 400
+    assert "Missing required parameter: 'image'" in message
+    assert "positional argument" not in message
+    assert "TypeError" not in message
+    assert getattr(err, "param", None) == "image"
+    assert err.model == "openai/gpt-image-1"
+    assert err.llm_provider == "openai"
+
+
+@pytest.mark.asyncio
+async def test_aimage_edit_direct_import_missing_image_raises_bad_request() -> None:
+    with pytest.raises(litellm.BadRequestError) as exc_info:
+        await aimage_edit(model="gpt-image-1", prompt="add a hat")
+
+    err = exc_info.value
+    assert err.status_code == 400
+    assert "Missing required parameter: 'image'" in str(err)
+    assert "positional argument" not in str(err)
+
+
+@pytest.mark.asyncio
+async def test_aimage_edit_missing_image_keeps_custom_llm_provider() -> None:
+    with pytest.raises(litellm.BadRequestError) as exc_info:
+        await litellm.aimage_edit(
+            model="gpt-image-1",
+            prompt="add a hat",
+            custom_llm_provider="azure",
+        )
+
+    err = exc_info.value
+    assert err.status_code == 400
+    assert err.llm_provider == "azure"
+    assert err.model == "gpt-image-1"