diff --git a/web/pages/Assistants.tsx b/web/pages/Assistants.tsx
index 73bac32..3b3eb3b 100644
--- a/web/pages/Assistants.tsx
+++ b/web/pages/Assistants.tsx
@@ -2007,7 +2007,19 @@ export const DebugDrawer: React.FC<{
           const delta = String(payload.text || '');
           if (!delta) return;
           setMessages((prev) => {
-            const idx = assistantDraftIndexRef.current;
+            let idx = assistantDraftIndexRef.current;
+            if (idx === null || !prev[idx] || prev[idx].role !== 'model') {
+              // Tool records can be appended between assistant chunks; recover the
+              // latest model row instead of creating a duplicate assistant row.
+              for (let i = prev.length - 1; i >= 0; i -= 1) {
+                if (prev[i]?.role === 'model') {
+                  idx = i;
+                  assistantDraftIndexRef.current = i;
+                  break;
+                }
+                if (prev[i]?.role === 'user') break;
+              }
+            }
             if (idx === null || !prev[idx] || prev[idx].role !== 'model') {
               const last = prev[prev.length - 1];
               if (last?.role === 'model' && last.text === delta) {
@@ -2027,8 +2039,17 @@ export const DebugDrawer: React.FC<{
         if (type === 'assistant.response.final') {
           const finalText = String(payload.text || '');
           setMessages((prev) => {
-            const idx = assistantDraftIndexRef.current;
+            let idx = assistantDraftIndexRef.current;
             assistantDraftIndexRef.current = null;
+            if (idx === null || !prev[idx] || prev[idx].role !== 'model') {
+              for (let i = prev.length - 1; i >= 0; i -= 1) {
+                if (prev[i]?.role === 'model') {
+                  idx = i;
+                  break;
+                }
+                if (prev[i]?.role === 'user') break;
+              }
+            }
             if (idx !== null && prev[idx] && prev[idx].role === 'model') {
               const next = [...prev];
               next[idx] = { ...next[idx], text: finalText || next[idx].text };