diff --git a/src/components/chat/AgentWorkspace.test.tsx b/src/components/chat/AgentWorkspace.test.tsx
new file mode 100644
index 0000000..04b4c4f
--- /dev/null
+++ b/src/components/chat/AgentWorkspace.test.tsx
@@ -0,0 +1,97 @@
+/* eslint-disable @next/next/no-img-element */
+import "@testing-library/jest-dom";
+import React from "react";
+import { render } from "@testing-library/react";
+
+import { AgentWorkspace } from "./AgentWorkspace";
+import type { Message } from "./GlobalChatbox.types";
+
+const renderCounts = new Map<string, number>();
+
+jest.mock("next/image", () => ({
+  __esModule: true,
+  default: (props: React.ImgHTMLAttributes<HTMLImageElement>) => <img {...props} alt={props.alt ?? ""} />,
+}));
+
+jest.mock("framer-motion", () => ({
+  AnimatePresence: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+  motion: {
+    div: ({ children, ...props }: React.HTMLAttributes<HTMLDivElement>) => <div {...props}>{children}</div>,
+  },
+}));
+
+jest.mock("./GlobalChatbox.parts", () => ({
+  TypingIndicator: () => <div>typing</div>,
+}));
+
+jest.mock("./AgentTurn", () => ({
+  AgentTurn: ({ message }: { message: Message }) => {
+    renderCounts.set(message.id, (renderCounts.get(message.id) ?? 0) + 1);
+    return <div data-testid={`turn-${message.id}`}>{message.content}</div>;
+  },
+}));
+
+describe("AgentWorkspace", () => {
+  const defaultProps = {
+    branchGroups: [],
+    branchTransition: null,
+    bottomRef: { current: null },
+    speakingMessageId: null,
+    speechState: "idle" as const,
+    onSpeak: jest.fn(),
+    onPauseSpeech: jest.fn(),
+    onResumeSpeech: jest.fn(),
+    onStopSpeech: jest.fn(),
+    isTtsSupported: false,
+    onRegenerate: jest.fn(),
+    onEditResubmit: jest.fn(),
+    onCycleBranch: jest.fn(),
+  };
+
+  beforeEach(() => {
+    renderCounts.clear();
+  });
+
+  it("keeps stable history turns from re-rendering while the last assistant message streams", () => {
+    const userMessage: Message = {
+      id: "user-1",
+      role: "user",
+      content: "question",
+    };
+    const assistantHistoryMessage: Message = {
+      id: "assistant-1",
+      role: "assistant",
+      content: "stable answer",
+    };
+    const streamingMessage: Message = {
+      id: "assistant-2",
+      role: "assistant",
+      content: "partial",
+    };
+
+    const { rerender } = render(
+      <AgentWorkspace
+        {...defaultProps}
+        isStreaming
+        messages={[userMessage, assistantHistoryMessage, streamingMessage]}
+      />,
+    );
+
+    const updatedStreamingMessage: Message = {
+      ...streamingMessage,
+      content: "partial with more tokens",
+    };
+
+    rerender(
+      <AgentWorkspace
+        {...defaultProps}
+        isStreaming
+        messages={[userMessage, assistantHistoryMessage, updatedStreamingMessage]}
+      />,
+    );
+
+    expect(renderCounts.get("user-1")).toBe(1);
+    expect(renderCounts.get("assistant-1")).toBe(1);
+    expect(renderCounts.get("assistant-2")).toBe(2);
+  });
+});
diff --git a/src/components/chat/AgentWorkspace.tsx b/src/components/chat/AgentWorkspace.tsx
index 06eafb9..5f3e03f 100644
--- a/src/components/chat/AgentWorkspace.tsx
+++ b/src/components/chat/AgentWorkspace.tsx
@@ -13,6 +13,7 @@ import { AgentTurn } from "./AgentTurn";
 import { TypingIndicator } from "./GlobalChatbox.parts";
 import type {
   BranchGroup,
+  BranchState,
   BranchTransition,
   Message,
   SpeechState,
@@ -36,6 +37,96 @@ type AgentWorkspaceProps = {
   onCycleBranch: (rootMessageId: string, direction: -1 | 1) => void;
 };
 
+type TurnListProps = {
+  messages: Message[];
+  branchGroups: BranchGroup[];
+  speakingMessageId: string | null;
+  speechState: SpeechState;
+  onSpeak: (messageId: string, text: string) => void;
+  onPauseSpeech: () => void;
+  onResumeSpeech: () => void;
+  onStopSpeech: () => void;
+  isTtsSupported: boolean;
+  onRegenerate: () => void;
+  onEditResubmit: (messageId: string, newContent: string) => void;
+  onCycleBranch: (rootMessageId: string, direction: -1 | 1) => void;
+};
+
+const sameMessages = (left: Message[], right: Message[]) =>
+  left.length === right.length &&
+  left.every((message, index) => message === right[index]);
+
+const TurnListInner = ({
+  messages,
+  branchGroups,
+  speakingMessageId,
+  speechState,
+  onSpeak,
+  onPauseSpeech,
+  onResumeSpeech,
+  onStopSpeech,
+  isTtsSupported,
+  onRegenerate,
+  onEditResubmit,
+  onCycleBranch,
+}: TurnListProps) => {
+  const branchStateByRootId = React.useMemo(() => {
+    const next = new Map<string, BranchState>();
+    branchGroups.forEach((group) => {
+      if (group.branches.length > 1) {
+        next.set(group.rootMessageId, {
+          activeIndex: group.activeIndex,
+          total: group.branches.length,
+        });
+      }
+    });
+    return next;
+  }, [branchGroups]);
+
+  return (
+    <>
+      {messages.map((message) => {
+        const rootMessageId = message.branchRootId ?? message.id;
+        return (
+          <AgentTurn
+            key={rootMessageId}
+            message={message}
+            branchState={branchStateByRootId.get(rootMessageId)}
+            messageSpeechState={speakingMessageId === message.id ? speechState : "idle"}
+            onSpeak={onSpeak}
+            onPause={onPauseSpeech}
+            onResume={onResumeSpeech}
+            onStopSpeech={onStopSpeech}
+            isTtsSupported={isTtsSupported}
+            onRegenerate={onRegenerate}
+            onEditResubmit={onEditResubmit}
+            onCycleBranch={onCycleBranch}
+          />
+        );
+      })}
+    </>
+  );
+};
+
+const TurnList = React.memo(
+  TurnListInner,
+  (prevProps, nextProps) =>
+    sameMessages(prevProps.messages, nextProps.messages) &&
+    prevProps.branchGroups === nextProps.branchGroups &&
+    prevProps.speakingMessageId === nextProps.speakingMessageId &&
+    prevProps.speechState === nextProps.speechState &&
+    prevProps.onSpeak === nextProps.onSpeak &&
+    prevProps.onPauseSpeech === nextProps.onPauseSpeech &&
+    prevProps.onResumeSpeech === nextProps.onResumeSpeech &&
+    prevProps.onStopSpeech === nextProps.onStopSpeech &&
+    prevProps.isTtsSupported === nextProps.isTtsSupported &&
+    prevProps.onRegenerate === nextProps.onRegenerate &&
+    prevProps.onEditResubmit === nextProps.onEditResubmit &&
+    prevProps.onCycleBranch === nextProps.onCycleBranch,
+);
+
+TurnList.displayName = "TurnList";
+
 const EmptyState = () => {
   const theme = useTheme();
   const capabilities = [
@@ -182,37 +273,12 @@ export const AgentWorkspace = ({
   const transitionMessages = branchTransition
     ? messages.slice(branchTransition.parentCount)
     : [];
-
-  const renderTurn = (message: Message) => {
-    const rootMessageId = message.branchRootId ?? message.id;
-    const branchGroup = branchGroups.find(
-      (group) => group.rootMessageId === rootMessageId,
-    );
-
-    return (
-      <AgentTurn
-        key={rootMessageId}
-        message={message}
-        branchState={
-          branchGroup && branchGroup.branches.length > 1
-            ? {
-                activeIndex: branchGroup.activeIndex,
-                total: branchGroup.branches.length,
-              }
-            : undefined
-        }
-        messageSpeechState={speakingMessageId === message.id ? speechState : "idle"}
-        onSpeak={onSpeak}
-        onPause={onPauseSpeech}
-        onResume={onResumeSpeech}
-        onStopSpeech={onStopSpeech}
-        isTtsSupported={isTtsSupported}
-        onRegenerate={onRegenerate}
-        onEditResubmit={onEditResubmit}
-        onCycleBranch={onCycleBranch}
-      />
-    );
-  };
+  const streamingMessage =
+    !branchTransition && isStreaming && messages.at(-1)?.role === "assistant"
+      ? messages.at(-1)
+      : undefined;
+  const historyMessages =
+    streamingMessage !== undefined ? messages.slice(0, -1) : stableMessages;
 
   return (
     <Box
@@ -232,7 +298,37 @@ export const AgentWorkspace = ({
 
       {messages.length > 0 ? (
         <Box sx={{ display: "flex", flexDirection: "column", gap: 2 }}>
-          {stableMessages.map(renderTurn)}
+          <TurnList
+            messages={historyMessages}
+            branchGroups={branchGroups}
+            speakingMessageId={speakingMessageId}
+            speechState={speechState}
+            onSpeak={onSpeak}
+            onPauseSpeech={onPauseSpeech}
+            onResumeSpeech={onResumeSpeech}
+            onStopSpeech={onStopSpeech}
+            isTtsSupported={isTtsSupported}
+            onRegenerate={onRegenerate}
+            onEditResubmit={onEditResubmit}
+            onCycleBranch={onCycleBranch}
+          />
+
+          {streamingMessage ? (
+            <TurnList
+              messages={[streamingMessage]}
+              branchGroups={branchGroups}
+              speakingMessageId={speakingMessageId}
+              speechState={speechState}
+              onSpeak={onSpeak}
+              onPauseSpeech={onPauseSpeech}
+              onResumeSpeech={onResumeSpeech}
+              onStopSpeech={onStopSpeech}
+              isTtsSupported={isTtsSupported}
+              onRegenerate={onRegenerate}
+              onEditResubmit={onEditResubmit}
+              onCycleBranch={onCycleBranch}
+            />
+          ) : null}
 
           {branchTransition ? (
             <AnimatePresence initial={false} mode="wait">
@@ -244,7 +340,20 @@ export const AgentWorkspace = ({
                 transition={{ duration: 0.18, ease: "easeOut" }}
                 style={{ display: "flex", flexDirection: "column", gap: 16 }}
               >
-                {transitionMessages.map(renderTurn)}
+                <TurnList
+                  messages={transitionMessages}
+                  branchGroups={branchGroups}
+                  speakingMessageId={speakingMessageId}
+                  speechState={speechState}
+                  onSpeak={onSpeak}
+                  onPauseSpeech={onPauseSpeech}
+                  onResumeSpeech={onResumeSpeech}
+                  onStopSpeech={onStopSpeech}
+                  isTtsSupported={isTtsSupported}
+                  onRegenerate={onRegenerate}
+                  onEditResubmit={onEditResubmit}
+                  onCycleBranch={onCycleBranch}
+                />
               </motion.div>
             </AnimatePresence>
           ) : null}