Refactor image content to use a shared ImageReference type (#45543)

## What changed

Represent images in `ContentItem` and `FunctionCallOutputContentItem` with `ImageReference::Inline`, flattened to preserve the existing `image_url` wire format. Update image producers and consumers and regenerate app-server schemas and SDK artifacts.

Preserve the Python SDK's `InputImageContentItem` and `InputImageFunctionCallOutputContentItem` class names during generation.

## Testing

Add a regression test for stable Python image class names and adapt existing image tests to the shared representation.

GitOrigin-RevId: c38a780ac3314c2ac2deb3afc1b93b94b6f93fec

sdk/python/scripts/update_sdk_artifacts.py

@@ -575,6 +575,7 @@ def generate_v2_all(schema_dir: Path) -> None:
             ],
             cwd=sdk_root(),
         )
+    _preserve_inline_image_class_names(out_path)
     _require_nullable_chatgpt_account_email(out_path)
     _preserve_reasoning_effort_enum(out_path)
     _preserve_thread_source_enum(out_path)
@@ -582,6 +583,23 @@ def generate_v2_all(schema_dir: Path) -> None:
     _normalize_generated_timestamps(out_path)
 
 
+def _preserve_inline_image_class_names(out_path: Path) -> None:
+    """Keep the public class names used before ImageReference was introduced."""
+    source = out_path.read_text()
+    stable_names = {
+        "ImageUrlContentItem": "InputImageContentItem",
+        "ImageUrlFunctionCallOutputContentItem": "InputImageFunctionCallOutputContentItem",
+    }
+    for generated_name, stable_name in stable_names.items():
+        if source.count(f"class {generated_name}(") != 1:
+            raise RuntimeError(f"Generated SDK is missing a unique {generated_name} class")
+        if re.search(rf"\b{re.escape(stable_name)}\b", source):
+            raise RuntimeError(f"Generated SDK already defines {stable_name}")
+        source = re.sub(rf"\b{re.escape(generated_name)}\b", stable_name, source)
+
+    out_path.write_text(source)
+
+
 def _require_nullable_chatgpt_account_email(out_path: Path) -> None:
     """Preserve required-but-nullable email semantics in the generated SDK model."""
     source = out_path.read_text()

sdk/python/src/openai_codex/generated/v2_all.py

@@ -7784,8 +7784,8 @@ class InputImageContentItem(BaseModel):
         populate_by_name=True,
     )
     detail: ImageDetail | None = None
-    image_url: str
     type: Annotated[Literal["input_image"], Field(title="InputImageContentItemType")]
+    image_url: str
 
 
 class ContentItem(
@@ -7796,9 +7796,7 @@ class ContentItem(
     model_config = ConfigDict(
         populate_by_name=True,
     )
-    root: (
-        InputTextContentItem | InputImageContentItem | InputAudioContentItem | OutputTextContentItem
-    )
+    root: InputTextContentItem | InputImageContentItem | InputAudioContentItem | OutputTextContentItem
 
 
 class ExperimentalFeature(BaseModel):
@@ -7980,10 +7978,10 @@ class InputImageFunctionCallOutputContentItem(BaseModel):
         populate_by_name=True,
     )
     detail: ImageDetail | None = None
-    image_url: str
     type: Annotated[
         Literal["input_image"], Field(title="InputImageFunctionCallOutputContentItemType")
     ]
+    image_url: str
 
 
 class FunctionCallOutputContentItem(

sdk/python/tests/test_artifact_workflow_and_binaries.py

@@ -536,6 +536,20 @@ def test_generated_chatgpt_account_email_is_required_nullable() -> None:
         ChatgptAccount.model_validate({"planType": "pro", "type": "chatgpt"})
 
 
+def test_generated_inline_image_class_names_remain_stable() -> None:
+    """Keep the existing Python class names when image references expand."""
+    from openai_codex.generated.v2_all import (
+        InputImageContentItem,
+        InputImageFunctionCallOutputContentItem,
+    )
+
+    assert InputImageContentItem.__name__ == "InputImageContentItem"
+    assert (
+        InputImageFunctionCallOutputContentItem.__name__
+        == "InputImageFunctionCallOutputContentItem"
+    )
+
+
 def test_runtime_package_template_has_no_checked_in_binaries() -> None:
     runtime_root = ROOT.parent / "python-runtime" / "src" / "codex_cli_bin"
     assert sorted(