diff --git a/src/agents/models/default_models.py b/src/agents/models/default_models.py
index 0259534ac4..3a8a122e8b 100644
--- a/src/agents/models/default_models.py
+++ b/src/agents/models/default_models.py
@@ -17,6 +17,16 @@
     reasoning=Reasoning(effort="low"),
     verbosity="low",
 )
+_GPT_5_NONE_DEFAULT_MODEL_SETTINGS: ModelSettings = ModelSettings(
+    reasoning=Reasoning(effort="none"),
+    verbosity="low",
+)
+
+_GPT_5_NONE_EFFORT_MODELS = {"gpt-5.1", "gpt-5.2"}
+
+
+def _is_gpt_5_none_effort_model(model_name: str) -> bool:
+    return model_name in _GPT_5_NONE_EFFORT_MODELS
 
 
 def gpt_5_reasoning_settings_required(model_name: str) -> bool:
@@ -54,5 +64,7 @@ def get_default_model_settings(model: Optional[str] = None) -> ModelSettings:
     """
     _model = model if model is not None else get_default_model()
     if gpt_5_reasoning_settings_required(_model):
+        if _is_gpt_5_none_effort_model(_model):
+            return copy.deepcopy(_GPT_5_NONE_DEFAULT_MODEL_SETTINGS)
         return copy.deepcopy(_GPT_5_DEFAULT_MODEL_SETTINGS)
     return ModelSettings()
diff --git a/tests/models/test_default_models.py b/tests/models/test_default_models.py
index ae8abdda53..d291aac1e3 100644
--- a/tests/models/test_default_models.py
+++ b/tests/models/test_default_models.py
@@ -26,6 +26,30 @@ def test_default_model_env_gpt_5():
     assert get_default_model_settings().reasoning.effort == "low"  # type: ignore[union-attr]
 
 
+@patch.dict(os.environ, {"OPENAI_DEFAULT_MODEL": "gpt-5.1"})
+def test_default_model_env_gpt_5_1():
+    assert get_default_model() == "gpt-5.1"
+    assert is_gpt_5_default() is True
+    assert gpt_5_reasoning_settings_required(get_default_model()) is True
+    assert get_default_model_settings().reasoning.effort == "none"  # type: ignore[union-attr]
+
+
+@patch.dict(os.environ, {"OPENAI_DEFAULT_MODEL": "gpt-5.2"})
+def test_default_model_env_gpt_5_2():
+    assert get_default_model() == "gpt-5.2"
+    assert is_gpt_5_default() is True
+    assert gpt_5_reasoning_settings_required(get_default_model()) is True
+    assert get_default_model_settings().reasoning.effort == "none"  # type: ignore[union-attr]
+
+
+@patch.dict(os.environ, {"OPENAI_DEFAULT_MODEL": "gpt-5.2-codex"})
+def test_default_model_env_gpt_5_2_codex():
+    assert get_default_model() == "gpt-5.2-codex"
+    assert is_gpt_5_default() is True
+    assert gpt_5_reasoning_settings_required(get_default_model()) is True
+    assert get_default_model_settings().reasoning.effort == "low"  # type: ignore[union-attr]
+
+
 @patch.dict(os.environ, {"OPENAI_DEFAULT_MODEL": "gpt-5-mini"})
 def test_default_model_env_gpt_5_mini():
     assert get_default_model() == "gpt-5-mini"