fix(images): stop forwarding the raw image[] and mask[] form keys

The /v1/images/edits handler binds the documented image[] and mask[] aliases
into their canonical parameters, then re-reads the multipart body, so the raw
bracketed keys rode along to the provider next to the values already built from
them. OpenAI rejected both: image[] as "Invalid type for 'image[0]'" and mask[]
as "Invalid parameter: 'mask'". Drop both aliases from what gets forwarded.

litellm/proxy/image_endpoints/endpoints.py

@@ -21,6 +21,10 @@ from litellm.types.llms.openai import ChatCompletionUserMessage
 
 router: Final = APIRouter()
 
+IMAGE_ARRAY_FIELD: Final = "image[]"
+MASK_ARRAY_FIELD: Final = "mask[]"
+BRACKETED_FILE_FIELDS: Final = frozenset({IMAGE_ARRAY_FIELD, MASK_ARRAY_FIELD})
+
 
 async def uploadfile_to_bytesio(upload: UploadFile) -> io.BytesIO:
     """
@@ -229,9 +233,9 @@ async def image_edit_api(
     fastapi_response: Response,
     user_api_key_dict: UserAPIKeyAuth = Depends(user_api_key_auth),
     image: list[UploadFile] | None = File(None),
-    image_array: list[UploadFile] | None = File(None, alias="image[]"),
+    image_array: list[UploadFile] | None = File(None, alias=IMAGE_ARRAY_FIELD),
     mask: list[UploadFile] | None = File(None),
-    mask_array: list[UploadFile] | None = File(None, alias="mask[]"),
+    mask_array: list[UploadFile] | None = File(None, alias=MASK_ARRAY_FIELD),
     model: str | None = None,
 ):
     """
@@ -279,7 +283,11 @@ async def image_edit_api(
     #########################################################
     # Read request body and convert UploadFiles to BytesIO
     #########################################################
-    data: Final = await _read_request_body(request=request)
+    data: Final = {
+        key: value
+        for key, value in (await _read_request_body(request=request)).items()
+        if key not in BRACKETED_FILE_FIELDS
+    }
     image_files: Final = await batch_to_bytesio(image)
     mask_files: Final = await batch_to_bytesio(mask)
     if image_files:

tests/test_litellm/proxy/image_endpoints/test_endpoints.py

@@ -5,10 +5,13 @@ from typing import Any, Dict
 
 import orjson
 import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
 from starlette.requests import Request
 from starlette.responses import Response
 
 from litellm.proxy._types import UserAPIKeyAuth
+from litellm.proxy.auth.user_api_key_auth import user_api_key_auth
 from litellm.proxy.image_endpoints import endpoints
 
 
@@ -115,3 +118,75 @@ async def test_image_generation_prompt_rerouting(monkeypatch):
     assert captured_route_request_data["prompt"] == "sanitized prompt"
     assert "messages" not in captured_route_request_data
     assert response.headers.get("x-callback-test") == "value"
+
+
+def _image_edit_client(monkeypatch, captured: Dict[str, Any]) -> TestClient:
+    class CaptureProcessing:
+        def __init__(self, data: Dict[str, Any]) -> None:
+            captured.update(data)
+
+        async def base_process_llm_request(self, **_: Any) -> Dict[str, Any]:
+            return {"data": [{"b64_json": "aGk="}]}
+
+    monkeypatch.setattr(endpoints, "ProxyBaseLLMRequestProcessing", CaptureProcessing)
+    monkeypatch.setattr("litellm.proxy.proxy_server.general_settings", {})
+    monkeypatch.setattr("litellm.proxy.proxy_server.user_model", None)
+
+    app = FastAPI()
+    app.include_router(endpoints.router)
+    app.dependency_overrides[user_api_key_auth] = lambda: UserAPIKeyAuth()
+    return TestClient(app)
+
+
+def test_image_edit_image_array_alias_is_not_forwarded(monkeypatch):
+    """The documented `image[]` alias must reach the provider only as `image`."""
+    captured: Dict[str, Any] = {}
+
+    response = _image_edit_client(monkeypatch, captured).post(
+        "/v1/images/edits",
+        files={"image[]": ("tree.png", b"\x89PNG\r\n\x1a\ntree", "image/png")},
+        data={"model": "gpt-image-1", "prompt": "add a hat"},
+    )
+
+    assert response.status_code == 200
+    assert "image[]" not in captured
+    assert [buffer.getvalue() for buffer in captured["image"]] == [b"\x89PNG\r\n\x1a\ntree"]
+    assert [buffer.name for buffer in captured["image"]] == ["tree.png"]
+
+
+def test_image_edit_mask_array_alias_is_not_forwarded(monkeypatch):
+    """`mask[]` has the same shape as `image[]` and must be dropped the same way."""
+    captured: Dict[str, Any] = {}
+
+    response = _image_edit_client(monkeypatch, captured).post(
+        "/v1/images/edits",
+        files={
+            "image": ("tree.png", b"\x89PNG\r\n\x1a\ntree", "image/png"),
+            "mask[]": ("mask.png", b"\x89PNG\r\n\x1a\nmask", "image/png"),
+        },
+        data={"model": "gpt-image-1", "prompt": "add a hat"},
+    )
+
+    assert response.status_code == 200
+    assert "mask[]" not in captured
+    assert [buffer.getvalue() for buffer in captured["mask"]] == [b"\x89PNG\r\n\x1a\nmask"]
+    assert [buffer.getvalue() for buffer in captured["image"]] == [b"\x89PNG\r\n\x1a\ntree"]
+
+
+def test_image_edit_canonical_file_fields_still_reach_the_provider(monkeypatch):
+    """Dropping the bracketed aliases must not touch the canonical fields."""
+    captured: Dict[str, Any] = {}
+
+    response = _image_edit_client(monkeypatch, captured).post(
+        "/v1/images/edits",
+        files={
+            "image": ("tree.png", b"\x89PNG\r\n\x1a\ntree", "image/png"),
+            "mask": ("mask.png", b"\x89PNG\r\n\x1a\nmask", "image/png"),
+        },
+        data={"model": "gpt-image-1", "prompt": "add a hat"},
+    )
+
+    assert response.status_code == 200
+    assert [buffer.getvalue() for buffer in captured["image"]] == [b"\x89PNG\r\n\x1a\ntree"]
+    assert [buffer.getvalue() for buffer in captured["mask"]] == [b"\x89PNG\r\n\x1a\nmask"]
+    assert captured["prompt"] == "add a hat"