diff --git a/src/agents/memory/openai_conversations_session.py b/src/agents/memory/openai_conversations_session.py
index 6a14e81a0..e74871bef 100644
--- a/src/agents/memory/openai_conversations_session.py
+++ b/src/agents/memory/openai_conversations_session.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from typing import Any, cast
+
 from openai import AsyncOpenAI
 
 from agents.models._openai_shared import get_default_openai_client
@@ -12,8 +14,9 @@ async def start_openai_conversations_session(openai_client: AsyncOpenAI | None =
     _maybe_openai_client = openai_client
     if openai_client is None:
         _maybe_openai_client = get_default_openai_client() or AsyncOpenAI()
-    # this never be None here
-    _openai_client: AsyncOpenAI = _maybe_openai_client  # type: ignore [assignment]
+    # ensure non-None for type checkers and readers
+    assert _maybe_openai_client is not None
+    _openai_client: AsyncOpenAI = _maybe_openai_client
 
     response = await _openai_client.conversations.create(items=[])
     return response.id
@@ -43,13 +46,13 @@ async def _clear_session_id(self) -> None:
 
     async def get_items(self, limit: int | None = None) -> list[TResponseInputItem]:
         session_id = await self._get_session_id()
-        all_items = []
+        all_items: list[dict[str, Any]] = []
         if limit is None:
             async for item in self._openai_client.conversations.items.list(
                 conversation_id=session_id,
                 order="asc",
             ):
-                # calling model_dump() to make this serializable
+                # model_dump for serialization; shape matches TResponseInputItem at runtime
                 all_items.append(item.model_dump(exclude_unset=True))
         else:
             async for item in self._openai_client.conversations.items.list(
@@ -57,13 +60,14 @@ async def get_items(self, limit: int | None = None) -> list[TResponseInputItem]:
                 limit=limit,
                 order="desc",
             ):
-                # calling model_dump() to make this serializable
+                # model_dump for serialization; shape matches TResponseInputItem at runtime
                 all_items.append(item.model_dump(exclude_unset=True))
                 if limit is not None and len(all_items) >= limit:
                     break
             all_items.reverse()
 
-        return all_items  # type: ignore
+        # The Conversations API guarantees this shape; narrow once for type checkers
+        return cast(list[TResponseInputItem], all_items)
 
     async def add_items(self, items: list[TResponseInputItem]) -> None:
         session_id = await self._get_session_id()
@@ -77,7 +81,7 @@ async def pop_item(self) -> TResponseInputItem | None:
         items = await self.get_items(limit=1)
         if not items:
             return None
-        item_id: str = str(items[0]["id"])  # type: ignore [typeddict-item]
+        item_id: str = str(items[0]["id"])  # type: ignore[typeddict-item]
         await self._openai_client.conversations.items.delete(
             conversation_id=session_id, item_id=item_id
         )