diff --git a/src/anthropic/lib/streaming/_beta_messages.py b/src/anthropic/lib/streaming/_beta_messages.py
index 0348875b..eacd63a5 100644
--- a/src/anthropic/lib/streaming/_beta_messages.py
+++ b/src/anthropic/lib/streaming/_beta_messages.py
@@ -559,5 +559,7 @@ def accumulate_event(
             current_snapshot.usage.server_tool_use = event.usage.server_tool_use
         if event.usage.iterations is not None:
             current_snapshot.usage.iterations = event.usage.iterations
+        if event.usage.output_tokens_details is not None:
+            current_snapshot.usage.output_tokens_details = event.usage.output_tokens_details
 
     return current_snapshot
diff --git a/src/anthropic/lib/streaming/_messages.py b/src/anthropic/lib/streaming/_messages.py
index 5c0da999..9bc6d6c8 100644
--- a/src/anthropic/lib/streaming/_messages.py
+++ b/src/anthropic/lib/streaming/_messages.py
@@ -516,5 +516,7 @@ def accumulate_event(
             current_snapshot.usage.cache_read_input_tokens = event.usage.cache_read_input_tokens
         if event.usage.server_tool_use is not None:
             current_snapshot.usage.server_tool_use = event.usage.server_tool_use
+        if event.usage.output_tokens_details is not None:
+            current_snapshot.usage.output_tokens_details = event.usage.output_tokens_details
 
     return current_snapshot
diff --git a/tests/lib/streaming/fixtures/refusal_response.txt b/tests/lib/streaming/fixtures/refusal_response.txt
index ae47459f..762c78d6 100644
--- a/tests/lib/streaming/fixtures/refusal_response.txt
+++ b/tests/lib/streaming/fixtures/refusal_response.txt
@@ -8,7 +8,7 @@ event: content_block_stop
 data: {"type":"content_block_stop","index":0}
 
 event: message_delta
-data: {"type":"message_delta","delta":{"stop_reason":"refusal","stop_sequence":null,"stop_details":{"type":"refusal","category":"cyber","explanation":"This request was refused due to policy."}},"usage":{"output_tokens":0}}
+data: {"type":"message_delta","delta":{"stop_reason":"refusal","stop_sequence":null,"stop_details":{"type":"refusal","category":"cyber","explanation":"This request was refused due to policy."}},"usage":{"output_tokens":120,"output_tokens_details":{"thinking_tokens":67}}}
 
 event: message_stop
 data: {"type":"message_stop"}
diff --git a/tests/lib/streaming/test_beta_messages.py b/tests/lib/streaming/test_beta_messages.py
index e0f9b5b1..f9e21395 100644
--- a/tests/lib/streaming/test_beta_messages.py
+++ b/tests/lib/streaming/test_beta_messages.py
@@ -232,6 +232,9 @@ def assert_refusal_response(message: BetaMessage) -> None:
     assert message.stop_details.type == "refusal"
     assert message.stop_details.category == "cyber"
     assert message.stop_details.explanation == "This request was refused due to policy."
+    assert message.usage.output_tokens == 120
+    assert message.usage.output_tokens_details is not None
+    assert message.usage.output_tokens_details.thinking_tokens == 67
 
 
 EXPECTED_FALLBACK_EVENT_TYPES = [
diff --git a/tests/lib/streaming/test_messages.py b/tests/lib/streaming/test_messages.py
index b86a3906..0c22856e 100644
--- a/tests/lib/streaming/test_messages.py
+++ b/tests/lib/streaming/test_messages.py
@@ -111,6 +111,9 @@ def assert_refusal_response(message: Message) -> None:
     assert message.stop_details.type == "refusal"
     assert message.stop_details.category == "cyber"
     assert message.stop_details.explanation == "This request was refused due to policy."
+    assert message.usage.output_tokens == 120
+    assert message.usage.output_tokens_details is not None
+    assert message.usage.output_tokens_details.thinking_tokens == 67
 
 
 class TestSyncMessages: