chore: import upstream snapshot with attribution

tests/extensions/experiemental/codex/test_payloads.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+import pytest
+
+from agents.extensions.experimental.codex.items import AgentMessageItem, TodoItem, TodoListItem
+
+
+def test_dict_like_supports_mapping_access_for_dataclass_fields() -> None:
+    item = AgentMessageItem(id="item-1", text="hello")
+
+    assert item["id"] == "item-1"
+    assert item["text"] == "hello"
+    assert item["type"] == "agent_message"
+    assert item.get("text") == "hello"
+    assert item.get("missing", "fallback") == "fallback"
+    assert "id" in item
+    assert "missing" not in item
+    assert object() not in item
+    assert list(item.keys()) == ["id", "text", "type"]
+
+
+def test_dict_like_raises_key_error_for_unknown_fields() -> None:
+    item = AgentMessageItem(id="item-1", text="hello")
+
+    with pytest.raises(KeyError, match="missing"):
+        _ = item["missing"]
+
+
+def test_dict_like_as_dict_recursively_converts_nested_dataclasses() -> None:
+    item = TodoListItem(
+        id="todo-list-1",
+        items=[
+            TodoItem(text="write tests", completed=True),
+            TodoItem(text="run tests", completed=False),
+        ],
+    )
+
+    assert item.as_dict() == {
+        "id": "todo-list-1",
+        "items": [
+            {"text": "write tests", "completed": True},
+            {"text": "run tests", "completed": False},
+        ],
+        "type": "todo_list",
+    }