diff --git a/langextract/providers/patterns.py b/langextract/providers/patterns.py
index 9fd18cab..40d8912a 100644
--- a/langextract/providers/patterns.py
+++ b/langextract/providers/patterns.py
@@ -24,10 +24,12 @@
 
 # OpenAI provider patterns
 OPENAI_PATTERNS = (
+    r'^gpt-3\.5',
     r'^gpt-4',
     r'^gpt4\.',
     r'^gpt-5',
     r'^gpt5\.',
+    r'^o[1-9]',
 )
 OPENAI_PRIORITY = 10
 
diff --git a/tests/registry_test.py b/tests/registry_test.py
index fa907067..c3563296 100644
--- a/tests/registry_test.py
+++ b/tests/registry_test.py
@@ -29,6 +29,7 @@
 from langextract.core import base_model
 from langextract.core import types
 from langextract.providers import builtin_registry
+from langextract.providers import patterns
 from langextract.providers import router
 
 
@@ -88,6 +89,14 @@ def test_multiple_patterns(self):
     self.assertEqual(router.resolve("gemini-pro"), FakeProvider)
     self.assertEqual(router.resolve("palm-2"), FakeProvider)
 
+  def test_openai_patterns_include_reasoning_and_gpt_3_5_models(self):
+    """OpenAI reasoning and GPT-3.5 model IDs resolve automatically."""
+    router.register(*patterns.OPENAI_PATTERNS)(FakeProvider)
+
+    for model_id in ("o1", "o3-mini", "o4-mini", "gpt-3.5-turbo"):
+      with self.subTest(model_id=model_id):
+        self.assertEqual(router.resolve(model_id), FakeProvider)
+
   def test_priority_resolution(self):
     """Test that higher priority wins on conflicts."""
     # Use direct registration to avoid module path issues in Bazel