fix: reasoning LM dump_state

dspy/clients/lm.py

@@ -280,7 +280,12 @@ def dump_state(self):
             "launch_kwargs",
             "train_kwargs",
         ]
-        return {key: getattr(self, key) for key in state_keys} | self.kwargs
+
+        kwargs = self.kwargs
+        if "max_completion_tokens" in kwargs:
+            kwargs["max_tokens"] = kwargs.pop("max_completion_tokens")
+
+        return {key: getattr(self, key) for key in state_keys} | kwargs
 
     def _check_truncation(self, results):
         if self.model_type != "responses" and any(c.finish_reason == "length" for c in results["choices"]):

tests/clients/test_lm.py

@@ -326,6 +326,30 @@ def test_dump_state():
     }
 
 
+def test_dump_state_with_reasoning_model():
+    lm = dspy.LM(
+        model="openai/gpt-5",
+        model_type="chat",
+        temperature=1,
+        max_tokens=32000,
+        num_retries=10,
+        launch_kwargs={"temperature": 1},
+        train_kwargs={"temperature": 5},
+    )
+
+    assert lm.dump_state() == {
+        "model": "openai/gpt-5",
+        "model_type": "chat",
+        "temperature": 1,
+        "max_tokens": 32000,
+        "num_retries": 10,
+        "cache": True,
+        "finetuning_model": None,
+        "launch_kwargs": {"temperature": 1},
+        "train_kwargs": {"temperature": 5},
+    }
+
+
 def test_exponential_backoff_retry():
     time_counter = []