diff --git a/litellm/llms/anthropic/chat/transformation.py b/litellm/llms/anthropic/chat/transformation.py
index e0e11be356c..feb26b19981 100644
--- a/litellm/llms/anthropic/chat/transformation.py
+++ b/litellm/llms/anthropic/chat/transformation.py
@@ -2134,9 +2134,10 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
         reasoning_content: str | None,
         completion_response: Mapping[str, object] | None,
     ) -> CompletionTokensDetailsWrapper:
+        iteration_thinking_tokens: Final = self._sum_iteration_thinking_tokens(iterations) if iterations else None
         reported_thinking_tokens: Final = (
-            self._sum_iteration_thinking_tokens(iterations)
-            if iterations
+            iteration_thinking_tokens
+            if iteration_thinking_tokens is not None
             else self._thinking_tokens_from_usage(usage_object)
         )
         if reported_thinking_tokens is not None:
@@ -2160,10 +2161,11 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
 
     def _sum_iteration_thinking_tokens(self, iterations: Sequence[object]) -> int | None:
         per_iteration: Final = tuple(
-            self._thinking_tokens_from_usage(iteration) for iteration in iterations if isinstance(iteration, Mapping)
+            self._thinking_tokens_from_usage(iteration) if isinstance(iteration, Mapping) else None
+            for iteration in iterations
         )
         reported: Final = tuple(tokens for tokens in per_iteration if tokens is not None)
-        return sum(reported) if reported else None
+        return sum(reported) if len(reported) == len(per_iteration) else None
 
     @staticmethod
     def is_anthropic_usage_object(usage_object: dict) -> bool:
diff --git a/litellm/responses/litellm_completion_transformation/transformation.py b/litellm/responses/litellm_completion_transformation/transformation.py
index fa2ce0d1505..f0614f1cacf 100644
--- a/litellm/responses/litellm_completion_transformation/transformation.py
+++ b/litellm/responses/litellm_completion_transformation/transformation.py
@@ -1763,18 +1763,15 @@ class LiteLLMCompletionResponsesConfig:
                                 choice.finish_reason
                             ),
                             role="assistant",
-                            content=(
-                                [
-                                    OutputText(
-                                        type="output_text",
-                                        text=reasoning_content,
-                                        annotations=[],
-                                    )
-                                ]
-                                if reasoning_content
-                                # mutable-ok: GenericResponseOutputItem.content is typed as a list
-                                else []
-                            ),
+                            content=[
+                                OutputText(
+                                    type="output_text",
+                                    text=text,
+                                    annotations=[],
+                                )
+                                for text in (reasoning_content,)
+                                if text
+                            ],
                             encrypted_content=encrypted_content,
                         )
                     ]
diff --git a/litellm/types/llms/anthropic.py b/litellm/types/llms/anthropic.py
index 7de383f6f13..f6b256ad5df 100644
--- a/litellm/types/llms/anthropic.py
+++ b/litellm/types/llms/anthropic.py
@@ -612,7 +612,7 @@ class AnthropicResponseUsageBlock(BaseModel):
 class AnthropicOutputTokensDetails(BaseModel):
     model_config = ConfigDict(extra="allow")
 
-    thinking_tokens: Optional[int] = None
+    thinking_tokens: int | None = None
 
 
 AnthropicFinishReason = Literal["end_turn", "max_tokens", "stop_sequence", "tool_use"]
diff --git a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
index 828a9c30fb9..de62c990f11 100644
--- a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
+++ b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
@@ -180,6 +180,50 @@ def test_calculate_usage_sums_provider_thinking_tokens_across_iterations():
     assert usage.completion_tokens_details.text_tokens == 150
 
 
+def test_calculate_usage_falls_back_when_only_some_iterations_report_thinking_tokens():
+    config = AnthropicConfig()
+
+    usage = config.calculate_usage(
+        usage_object={
+            "input_tokens": 10,
+            "output_tokens": 300,
+            "output_tokens_details": {"thinking_tokens": 240},
+            "iterations": [
+                {"input_tokens": 5, "output_tokens": 100, "output_tokens_details": {"thinking_tokens": 60}},
+                {"input_tokens": 5, "output_tokens": 200},
+            ],
+        },
+        reasoning_content=None,
+    )
+
+    assert usage.completion_tokens == 300
+    assert usage.completion_tokens_details is not None
+    assert usage.completion_tokens_details.reasoning_tokens == 240
+    assert usage.completion_tokens_details.text_tokens == 60
+
+
+def test_calculate_usage_reports_unknown_split_when_only_some_iterations_report_thinking_tokens():
+    config = AnthropicConfig()
+
+    usage = config.calculate_usage(
+        usage_object={
+            "input_tokens": 10,
+            "output_tokens": 300,
+            "iterations": [
+                {"input_tokens": 5, "output_tokens": 100, "output_tokens_details": {"thinking_tokens": 60}},
+                {"input_tokens": 5, "output_tokens": 200},
+            ],
+        },
+        reasoning_content="",
+        completion_response={"content": [{"type": "thinking", "thinking": "", "signature": "sig"}]},
+    )
+
+    assert usage.completion_tokens == 300
+    assert usage.completion_tokens_details is not None
+    assert usage.completion_tokens_details.reasoning_tokens is None
+    assert usage.completion_tokens_details.text_tokens is None
+
+
 def test_calculate_usage_reports_unknown_split_when_thinking_ran_without_a_count():
     config = AnthropicConfig()