diff --git a/studio/frontend/src/components/assistant-ui/reasoning.tsx b/studio/frontend/src/components/assistant-ui/reasoning.tsx
index 387f8cd458..fe913baf2a 100644
--- a/studio/frontend/src/components/assistant-ui/reasoning.tsx
+++ b/studio/frontend/src/components/assistant-ui/reasoning.tsx
@@ -316,15 +316,28 @@ const ReasoningGroupImpl: ReasoningGroupComponent = ({
     if (message.status?.type !== "running") {
       return false;
     }
-    const lastIndex = message.parts.length - 1;
-    if (lastIndex < 0) {
+    const parts = message.parts;
+    const len = parts.length;
+    if (len === 0) {
       return false;
     }
-    const lastType = message.parts[lastIndex]?.type;
-    if (lastType !== "reasoning") {
+
+    let groupHasReasoning = false;
+    for (let i = startIndex; i <= endIndex && i < len; i += 1) {
+      if (parts[i]?.type === "reasoning") {
+        groupHasReasoning = true;
+        break;
+      }
+    }
+    if (!groupHasReasoning) {
       return false;
     }
-    return lastIndex >= startIndex && lastIndex <= endIndex;
+    for (let i = endIndex + 1; i < len; i += 1) {
+      if (parts[i]?.type !== "tool-call") {
+        return false;
+      }
+    }
+    return true;
   });
 
   const persistedDuration = useAuiState(({ message }) => {