fix: #3357 AgentOutputSchema.name() crash on Literal output types

src/agents/agent_output.py

@@ -180,15 +180,25 @@ def _is_subclass_of_base_model_or_dict(t: Any) -> bool:
     return issubclass(t, BaseModel | dict)
 
 
-def _type_to_str(t: type[Any]) -> str:
+def _type_to_str(t: Any) -> str:
     origin = get_origin(t)
     args = get_args(t)
 
     if origin is None:
-        # It's a simple type like `str`, `int`, etc.
-        return t.__name__
+        # Plain type (str, int, MyModel, ...) or a non-type value supplied as a
+        # type argument — e.g. the "ok" inside `Literal["ok"]` is a str instance,
+        # not a class, so `t.__name__` would raise. Fall back to repr() in that
+        # case so nested forms like `list[Literal["ok"]]` still format cleanly.
+        if isinstance(t, type):
+            return t.__name__
+        return repr(t)
     elif args:
         args_str = ", ".join(_type_to_str(arg) for arg in args)
-        return f"{origin.__name__}[{args_str}]"
+        # `typing.Literal`/`typing.Union`/etc. expose `_name` rather than
+        # `__name__` on some Python versions.
+        origin_name = (
+            getattr(origin, "__name__", None) or getattr(origin, "_name", None) or str(origin)
+        )
+        return f"{origin_name}[{args_str}]"
     else:
         return str(t)

tests/test_output_tool.py

@@ -1,5 +1,5 @@
 import json
-from typing import Any
+from typing import Any, Literal, cast
 
 import pytest
 from pydantic import BaseModel
@@ -94,6 +94,33 @@ def test_structured_output_generic_dict_rejects_wrapper_shape():
         output_schema.validate_json(json.dumps({"response": {"foo": 1}}))
 
 
+def test_structured_output_literal_name_does_not_crash():
+    # `AgentOutputSchema.name()` used to raise `AttributeError` on `Literal["ok"]`
+    # because the Literal value "ok" is a `str` instance rather than a class, and
+    # the name formatter unconditionally read `__name__`. See issue #3357.
+    schema = AgentOutputSchema(cast(type[Any], Literal["ok"]))
+    assert schema.name() == "Literal['ok']"
+
+    # Multiple Literal members format cleanly.
+    schema_multi = AgentOutputSchema(cast(type[Any], Literal["ok", "done"]))
+    assert schema_multi.name() == "Literal['ok', 'done']"
+
+    # Literal nested inside a generic still works.
+    schema_nested = AgentOutputSchema(
+        cast(type[Any], list[Literal["ok", "done"]]),
+        strict_json_schema=False,
+    )
+    assert schema_nested.name() == "list[Literal['ok', 'done']]"
+
+    # Non-string Literal values use repr() so they keep their original literal form.
+    schema_int = AgentOutputSchema(cast(type[Any], Literal[1, 2]))
+    assert schema_int.name() == "Literal[1, 2]"
+
+    # Plain and other generic types are unchanged by the fix.
+    assert AgentOutputSchema(str).name() == "str"
+    assert AgentOutputSchema(list[int]).name() == "list[int]"
+
+
 def test_bad_json_raises_error(mocker):
     agent = Agent(name="test", output_type=Foo)
     output_schema = get_output_schema(agent)