diff --git a/kagent-ui/CHANGELOG.md b/kagent-ui/CHANGELOG.md
index 7267008..933dc29 100644
--- a/kagent-ui/CHANGELOG.md
+++ b/kagent-ui/CHANGELOG.md
@@ -1,5 +1,16 @@
 # CHANGELOG
 
+## 2026-04-16
+
+- 修复聊天界面 assistant 回复重复显示：
+  - 为 assistant UI 消息补充 `turnId` 元信息，并在前端状态层归并同一 turn 中相邻的 assistant 气泡，避免 `item/started`、`item/agentMessage/delta`、`item/completed` 之间的消息 ID 不一致时留下重复回复。
+  - `thread/resume` 历史恢复沿用同样的相邻 assistant 归并规则，避免切换或重开线程后再次出现重复欢迎语。
+  - 新增 `messages.test.ts` 回归测试，覆盖相邻 assistant 合并、chunked assistant 片段重组、live delta 归并与历史恢复路径，并确保中间夹有其他 item 时不会误合并。
+- 修复聊天界面 SSE 增量消息累积问题：
+  - `use-codex-session` 改为为 `reasoning` 与 `mcpToolCall/progress` 使用按 turn 稳定的临时消息 ID，流式增量改为原地更新，不再为每个增量块堆出新的消息条目。
+  - `turn/completed` 与 `error` 事件现在会清理当前 turn 的临时思考/工具进度卡片，避免对话结束后残留重复占位消息。
+  - 新增 `messages.test.ts`，覆盖临时消息清理与流式占位原地更新的纯函数行为。
+
 ## 2026-02-24
 
 - 修复“查看沙箱日志”鉴权失败（401）：
diff --git a/kagent-ui/bun.lockb b/kagent-ui/bun.lockb
index 2814e3b..4fa654c 100755
Binary files a/kagent-ui/bun.lockb and b/kagent-ui/bun.lockb differ
diff --git a/kagent-ui/components/assistant-ui/thread.tsx b/kagent-ui/components/assistant-ui/thread.tsx
index cfc1fd9..9304297 100644
--- a/kagent-ui/components/assistant-ui/thread.tsx
+++ b/kagent-ui/components/assistant-ui/thread.tsx
@@ -14,7 +14,11 @@ import {
 import ReactMarkdown from "react-markdown";
 import remarkGfm from "remark-gfm";
 import { Button } from "@/components/ui/button";
-import { getProviderTypeMeta, PROVIDER_TYPE_ICON_MAP } from "@/lib/model-provider-type";
+import type { FileUpdateChange } from "@/lib/codex-app-server/v2/FileUpdateChange";
+import {
+  getProviderTypeMeta,
+  PROVIDER_TYPE_ICON_MAP,
+} from "@/lib/model-provider-type";
 import {
   Select,
   SelectContent,
@@ -28,7 +32,7 @@ export type UserAttachment = { type: "image" | "localImage"; src: string };
 
 export type UiMessage =
   | { id: string; kind: "user"; text: string; attachments: UserAttachment[] }
-  | { id: string; kind: "assistant"; text: string }
+  | { id: string; kind: "assistant"; text: string; turnId?: string }
   | { id: string; kind: "turnCompleted"; turnId: string; text: string }
   | { id: string; kind: "reasoning"; summary: string[]; content: string[] }
   | {
@@ -45,7 +49,7 @@ export type UiMessage =
       id: string;
       kind: "fileChange";
       status: string;
-      changes: Array<{ path: string; kind: string; diff: string }>;
+      changes: Array<FileUpdateChange>;
       output: string | null;
     }
   | {
@@ -469,7 +473,7 @@ function renderAssistantPayload(msg: Exclude<UiMessage, { kind: "user" }>) {
                 className="rounded-md border bg-background p-2"
               >
                 <div className="text-xs text-muted-foreground">
-                  {change.path} · {change.kind}
+                  {change.path} · {formatFileChangeKind(change.kind)}
                 </div>
                 {change.diff ? (
                   <pre className="mt-2 max-h-80 overflow-auto text-xs">
@@ -646,6 +650,19 @@ function formatDuration(ms: number) {
   return `${minutes}m ${rest.toFixed(0)}s`;
 }
 
+function formatFileChangeKind(kind: FileUpdateChange["kind"]) {
+  switch (kind.type) {
+    case "add":
+      return "add";
+    case "delete":
+      return "delete";
+    case "update":
+      return kind.move_path ? `update -> ${kind.move_path}` : "update";
+  }
+  const exhaustiveCheck: never = kind;
+  return exhaustiveCheck;
+}
+
 const markdownComponents: Components = {
   h1: ({ children }) => (
     <h1 className="mb-4 text-2xl font-bold tracking-tight">{children}</h1>
diff --git a/kagent-ui/hooks/use-codex-session.ts b/kagent-ui/hooks/use-codex-session.ts
index 3659855..348a313 100644
--- a/kagent-ui/hooks/use-codex-session.ts
+++ b/kagent-ui/hooks/use-codex-session.ts
@@ -40,6 +40,7 @@ import {
   appendReasoningContentDelta,
   appendReasoningSummaryDelta,
   extractMessagesFromThread,
+  removeMessagesByIds,
   threadItemToUiMessage,
   upsertMessage,
 } from "@/lib/assistant/messages";
@@ -128,7 +129,10 @@ function normalizeAndSortSessions(list: CodexThread[]): CodexThread[] {
 /**
  * 合并会话列表（以 incoming 为主，补充 local 中暂未同步到服务端的会话）
  */
-function mergeSessions(incoming: CodexThread[], local: CodexThread[]): CodexThread[] {
+function mergeSessions(
+  incoming: CodexThread[],
+  local: CodexThread[],
+): CodexThread[] {
   const map = new Map<string, CodexThread>();
   for (const item of incoming) {
     map.set(item.id, item);
@@ -140,6 +144,36 @@ function mergeSessions(incoming: CodexThread[], local: CodexThread[]): CodexThre
   return normalizeAndSortSessions([...map.values()]);
 }
 
+const TEMPORARY_STREAMING_ITEM_TYPES = ["reasoning", "mcpToolCall"] as const;
+
+type TemporaryStreamingItemType =
+  (typeof TEMPORARY_STREAMING_ITEM_TYPES)[number];
+
+function isTemporaryStreamingItemType(
+  type: string,
+): type is TemporaryStreamingItemType {
+  return TEMPORARY_STREAMING_ITEM_TYPES.includes(
+    type as TemporaryStreamingItemType,
+  );
+}
+
+function buildTemporaryMessageId(
+  threadId: string,
+  turnId: string,
+  type: TemporaryStreamingItemType,
+): string {
+  return `temp:${threadId}:${turnId}:${type}`;
+}
+
+function getTemporaryMessageIdsForTurn(
+  threadId: string,
+  turnId: string,
+): string[] {
+  return TEMPORARY_STREAMING_ITEM_TYPES.map((type) =>
+    buildTemporaryMessageId(threadId, turnId, type),
+  );
+}
+
 /**
  * Codex 会话管理 Hook
  * 提供会话列表、创建、恢复、消息发送、事件流处理等功能
@@ -170,8 +204,6 @@ export function useCodexSession({
   const [createSessionSubmitting, setCreateSessionSubmitting] = useState(false);
 
   const eventsAbortRef = useRef<AbortController | null>(null);
-  // 映射流式 item ID：key = `${threadId}:${turnId}:${type}`，value = 按顺序存储的 itemId 数组
-  const streamingItemRef = useRef<Record<string, string[]>>({});
 
   const activeWorkspaceId = activeWorkspace?.id ?? null;
 
@@ -441,11 +473,6 @@ export function useCodexSession({
             const p = msg.params as ErrorNotification | undefined;
             if (!p?.threadId || !p?.turnId || !p?.error?.message) return;
 
-            const prefix = `${p.threadId}:${p.turnId}:`;
-            for (const key of Object.keys(streamingItemRef.current)) {
-              if (key.startsWith(prefix)) delete streamingItemRef.current[key];
-            }
-
             setRunning((cur) => {
               if (!cur) return cur;
               if (cur.sessionId !== p.threadId) return cur;
@@ -463,11 +490,17 @@ export function useCodexSession({
 
             setMessagesBySession((prev) => ({
               ...prev,
-              [p.threadId]: upsertMessage(prev[p.threadId] ?? [], {
-                id: `error_${p.threadId}_${p.turnId}`,
-                kind: "assistant",
-                text: `**请求失败**\n\n${errorHint}`,
-              }),
+              [p.threadId]: upsertMessage(
+                removeMessagesByIds(
+                  prev[p.threadId] ?? [],
+                  getTemporaryMessageIdsForTurn(p.threadId, p.turnId),
+                ),
+                {
+                  id: `error_${p.threadId}_${p.turnId}`,
+                  kind: "assistant",
+                  text: `**请求失败**\n\n${errorHint}`,
+                },
+              ),
             }));
 
             if (shouldGuideNewThread) {
@@ -482,17 +515,15 @@ export function useCodexSession({
             const p = msg.params as ItemStartedNotification | undefined;
             if (!p?.threadId || !p?.turnId || !p?.item) return;
             const scopedId = buildScopedItemId(p.turnId, p.item.id);
+            const messageId = isTemporaryStreamingItemType(p.item.type)
+              ? buildTemporaryMessageId(p.threadId, p.turnId, p.item.type)
+              : scopedId;
             const ui = threadItemToUiMessage(
-              overrideThreadItemId(p.item, scopedId),
+              overrideThreadItemId(p.item, messageId),
+              p.turnId,
             );
             if (!ui) return;
             if (ui.kind === "user") return;
-            const key = `${p.threadId}:${p.turnId}:${p.item.type}`;
-            const arr = streamingItemRef.current[key] ?? [];
-            if (!arr.includes(scopedId)) {
-              arr.push(scopedId);
-            }
-            streamingItemRef.current[key] = arr;
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: upsertMessage(prev[p.threadId] ?? [], ui),
@@ -509,20 +540,14 @@ export function useCodexSession({
               typeof p.delta !== "string"
             )
               return;
-            const key = `${p.threadId}:${p.turnId}:agentMessage`;
-            const arr = streamingItemRef.current[key] ?? [];
-            const fallbackId = buildScopedItemId(p.turnId, p.itemId);
-            const mappedId = arr.length > 0 ? arr[0] : fallbackId;
-            if (arr.length === 0) {
-              arr.push(fallbackId);
-              streamingItemRef.current[key] = arr;
-            }
+            const itemId = buildScopedItemId(p.turnId, p.itemId);
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: appendAgentDelta(
                 prev[p.threadId] ?? [],
-                mappedId,
+                itemId,
                 p.delta,
+                p.turnId,
               ),
             }));
             return;
@@ -533,19 +558,16 @@ export function useCodexSession({
               | ReasoningSummaryPartAddedNotification
               | undefined;
             if (!p?.threadId || !p?.turnId || !p?.itemId) return;
-            const key = `${p.threadId}:${p.turnId}:reasoning`;
-            const arr = streamingItemRef.current[key] ?? [];
-            const fallbackId = buildScopedItemId(p.turnId, p.itemId);
-            const mappedId = arr.length > 0 ? arr[0] : fallbackId;
-            if (arr.length === 0) {
-              arr.push(fallbackId);
-              streamingItemRef.current[key] = arr;
-            }
+            const itemId = buildTemporaryMessageId(
+              p.threadId,
+              p.turnId,
+              "reasoning",
+            );
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: appendReasoningSummaryDelta(
                 prev[p.threadId] ?? [],
-                mappedId,
+                itemId,
                 p.summaryIndex,
                 "",
               ),
@@ -564,19 +586,16 @@ export function useCodexSession({
               typeof p.delta !== "string"
             )
               return;
-            const key = `${p.threadId}:${p.turnId}:reasoning`;
-            const arr = streamingItemRef.current[key] ?? [];
-            const fallbackId = buildScopedItemId(p.turnId, p.itemId);
-            const mappedId = arr.length > 0 ? arr[0] : fallbackId;
-            if (arr.length === 0) {
-              arr.push(fallbackId);
-              streamingItemRef.current[key] = arr;
-            }
+            const itemId = buildTemporaryMessageId(
+              p.threadId,
+              p.turnId,
+              "reasoning",
+            );
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: appendReasoningSummaryDelta(
                 prev[p.threadId] ?? [],
-                mappedId,
+                itemId,
                 p.summaryIndex,
                 p.delta,
               ),
@@ -593,19 +612,16 @@ export function useCodexSession({
               typeof p.delta !== "string"
             )
               return;
-            const key = `${p.threadId}:${p.turnId}:reasoning`;
-            const arr = streamingItemRef.current[key] ?? [];
-            const fallbackId = buildScopedItemId(p.turnId, p.itemId);
-            const mappedId = arr.length > 0 ? arr[0] : fallbackId;
-            if (arr.length === 0) {
-              arr.push(fallbackId);
-              streamingItemRef.current[key] = arr;
-            }
+            const itemId = buildTemporaryMessageId(
+              p.threadId,
+              p.turnId,
+              "reasoning",
+            );
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: appendReasoningContentDelta(
                 prev[p.threadId] ?? [],
-                mappedId,
+                itemId,
                 p.contentIndex,
                 p.delta,
               ),
@@ -624,19 +640,12 @@ export function useCodexSession({
               typeof p.delta !== "string"
             )
               return;
-            const key = `${p.threadId}:${p.turnId}:commandExecution`;
-            const arr = streamingItemRef.current[key] ?? [];
-            const fallbackId = buildScopedItemId(p.turnId, p.itemId);
-            const mappedId = arr.length > 0 ? arr[0] : fallbackId;
-            if (arr.length === 0) {
-              arr.push(fallbackId);
-              streamingItemRef.current[key] = arr;
-            }
+            const itemId = buildScopedItemId(p.turnId, p.itemId);
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: appendCommandOutputDelta(
                 prev[p.threadId] ?? [],
-                mappedId,
+                itemId,
                 p.delta,
               ),
             }));
@@ -646,21 +655,14 @@ export function useCodexSession({
           if (method === "item/commandExecution/terminalInteraction") {
             const p = msg.params as TerminalInteractionNotification | undefined;
             if (!p?.threadId || !p?.turnId || !p?.itemId) return;
-            const key = `${p.threadId}:${p.turnId}:commandExecution`;
-            const arr = streamingItemRef.current[key] ?? [];
-            const fallbackId = buildScopedItemId(p.turnId, p.itemId);
-            const mappedId = arr.length > 0 ? arr[0] : fallbackId;
-            if (arr.length === 0) {
-              arr.push(fallbackId);
-              streamingItemRef.current[key] = arr;
-            }
+            const itemId = buildScopedItemId(p.turnId, p.itemId);
             const delta = p.stdin ? `\n> ${p.stdin}` : "";
             if (!delta) return;
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: appendCommandOutputDelta(
                 prev[p.threadId] ?? [],
-                mappedId,
+                itemId,
                 delta,
               ),
             }));
@@ -678,19 +680,12 @@ export function useCodexSession({
               typeof p.delta !== "string"
             )
               return;
-            const key = `${p.threadId}:${p.turnId}:fileChange`;
-            const arr = streamingItemRef.current[key] ?? [];
-            const fallbackId = buildScopedItemId(p.turnId, p.itemId);
-            const mappedId = arr.length > 0 ? arr[0] : fallbackId;
-            if (arr.length === 0) {
-              arr.push(fallbackId);
-              streamingItemRef.current[key] = arr;
-            }
+            const itemId = buildScopedItemId(p.turnId, p.itemId);
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: appendFileChangeOutputDelta(
                 prev[p.threadId] ?? [],
-                mappedId,
+                itemId,
                 p.delta,
               ),
             }));
@@ -706,19 +701,16 @@ export function useCodexSession({
               typeof p.message !== "string"
             )
               return;
-            const key = `${p.threadId}:${p.turnId}:mcpToolCall`;
-            const arr = streamingItemRef.current[key] ?? [];
-            const fallbackId = buildScopedItemId(p.turnId, p.itemId);
-            const mappedId = arr.length > 0 ? arr[0] : fallbackId;
-            if (arr.length === 0) {
-              arr.push(fallbackId);
-              streamingItemRef.current[key] = arr;
-            }
+            const itemId = buildTemporaryMessageId(
+              p.threadId,
+              p.turnId,
+              "mcpToolCall",
+            );
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: appendMcpToolProgress(
                 prev[p.threadId] ?? [],
-                mappedId,
+                itemId,
                 p.message,
               ),
             }));
@@ -728,15 +720,12 @@ export function useCodexSession({
           if (method === "item/completed") {
             const p = msg.params as ItemCompletedNotification | undefined;
             if (!p?.threadId || !p?.turnId || !p?.item) return;
-            const key = `${p.threadId}:${p.turnId}:${p.item.type}`;
-            const arr = streamingItemRef.current[key] ?? [];
-            const mappedId = arr.shift();
-            streamingItemRef.current[key] = arr;
-            const scopedId = mappedId ?? buildScopedItemId(p.turnId, p.item.id);
+            const scopedId = buildScopedItemId(p.turnId, p.item.id);
             const item = overrideThreadItemId(p.item, scopedId);
-            const ui = threadItemToUiMessage(item);
+            const ui = threadItemToUiMessage(item, p.turnId);
             if (!ui) return;
             if (ui.kind === "user") return;
+            if (p.item.type === "reasoning") return;
             setMessagesBySession((prev) => ({
               ...prev,
               [p.threadId]: upsertMessage(prev[p.threadId] ?? [], ui),
@@ -750,17 +739,19 @@ export function useCodexSession({
             const dividerId = `turn_completed_${p.threadId}_${p.turn.id}`;
             setMessagesBySession((prev) => ({
               ...prev,
-              [p.threadId]: upsertMessage(prev[p.threadId] ?? [], {
-                id: dividerId,
-                kind: "turnCompleted",
-                turnId: p.turn.id,
-                text: "This round of conversation has ended",
-              }),
+              [p.threadId]: upsertMessage(
+                removeMessagesByIds(
+                  prev[p.threadId] ?? [],
+                  getTemporaryMessageIdsForTurn(p.threadId, p.turn.id),
+                ),
+                {
+                  id: dividerId,
+                  kind: "turnCompleted",
+                  turnId: p.turn.id,
+                  text: "This round of conversation has ended",
+                },
+              ),
             }));
-            const prefix = `${p.threadId}:${p.turn.id}:`;
-            for (const key of Object.keys(streamingItemRef.current)) {
-              if (key.startsWith(prefix)) delete streamingItemRef.current[key];
-            }
             setRunning((cur) => {
               if (!cur) return cur;
               if (cur.sessionId !== p.threadId) return cur;
diff --git a/kagent-ui/lib/assistant/messages.test.js b/kagent-ui/lib/assistant/messages.test.js
new file mode 100644
index 0000000..968b19b
--- /dev/null
+++ b/kagent-ui/lib/assistant/messages.test.js
@@ -0,0 +1,83 @@
+import { describe, expect, test } from "bun:test";
+import {
+  appendMcpToolProgress,
+  appendReasoningContentDelta,
+  removeMessagesByIds,
+} from "./messages";
+
+describe("assistant message helpers", () => {
+  test("removeMessagesByIds only removes matching temporary messages", () => {
+    const messages = [
+      { id: "user-1", kind: "user", text: "hello", attachments: [] },
+      {
+        id: "temp:thread:turn:reasoning",
+        kind: "reasoning",
+        summary: [],
+        content: ["thinking"],
+      },
+      {
+        id: "tool-1",
+        kind: "mcpToolCall",
+        server: "demo",
+        tool: "search",
+        status: "completed",
+        args: null,
+        result: { ok: true },
+        error: null,
+        durationMs: 12,
+        progress: [],
+      },
+      { id: "assistant-1", kind: "assistant", text: "done" },
+    ];
+
+    const filtered = removeMessagesByIds(messages, [
+      "temp:thread:turn:reasoning",
+      "temp:thread:turn:mcpToolCall",
+    ]);
+
+    expect(filtered).toHaveLength(3);
+    expect(filtered.map((msg) => msg.id)).toEqual([
+      "user-1",
+      "tool-1",
+      "assistant-1",
+    ]);
+  });
+
+  test("streaming deltas update the same temporary placeholder in place", () => {
+    const first = appendReasoningContentDelta(
+      [],
+      "temp:thread:turn:reasoning",
+      0,
+      "step 1",
+    );
+    const second = appendReasoningContentDelta(
+      first,
+      "temp:thread:turn:reasoning",
+      0,
+      " + step 2",
+    );
+    const third = appendMcpToolProgress(
+      second,
+      "temp:thread:turn:mcpToolCall",
+      "fetching",
+    );
+    const fourth = appendMcpToolProgress(
+      third,
+      "temp:thread:turn:mcpToolCall",
+      "done",
+    );
+
+    expect(second).toHaveLength(1);
+    expect(second[0]).toMatchObject({
+      id: "temp:thread:turn:reasoning",
+      kind: "reasoning",
+      content: ["step 1 + step 2"],
+    });
+    expect(fourth).toHaveLength(2);
+    expect(fourth[1]).toMatchObject({
+      id: "temp:thread:turn:mcpToolCall",
+      kind: "mcpToolCall",
+      progress: ["fetching", "done"],
+    });
+  });
+});
diff --git a/kagent-ui/lib/assistant/messages.test.ts b/kagent-ui/lib/assistant/messages.test.ts
new file mode 100644
index 0000000..72f6bd0
--- /dev/null
+++ b/kagent-ui/lib/assistant/messages.test.ts
@@ -0,0 +1,209 @@
+import assert from "node:assert/strict";
+import { describe, test } from "node:test";
+import type { Thread } from "@/lib/codex-app-server/v2/Thread";
+import type { UiMessage } from "@/components/assistant-ui/thread";
+import {
+  appendAgentDelta,
+  extractMessagesFromThread,
+  upsertMessage,
+} from "@/lib/assistant/messages";
+
+describe("assistant message merging", () => {
+  test("merges adjacent assistant messages from the same turn", () => {
+    const started = upsertMessage([], {
+      id: "turn-1:item-1",
+      kind: "assistant",
+      text: "你好！很高兴见到你。",
+      turnId: "turn-1",
+    } as UiMessage);
+
+    const completed = upsertMessage(started, {
+      id: "turn-1:item-2",
+      kind: "assistant",
+      text: "你好！很高兴见到你。",
+      turnId: "turn-1",
+    } as UiMessage);
+
+    assert.deepStrictEqual(completed, [
+      {
+        id: "turn-1:item-1",
+        kind: "assistant",
+        text: "你好！很高兴见到你。",
+        turnId: "turn-1",
+      },
+    ]);
+  });
+
+  test("merges a live assistant delta into the adjacent assistant bubble", () => {
+    const started = upsertMessage([], {
+      id: "turn-1:item-1",
+      kind: "assistant",
+      text: "",
+      turnId: "turn-1",
+    } as UiMessage);
+
+    const streamed = appendAgentDelta(
+      started,
+      "turn-1:item-2",
+      "你好！很高兴见到你。",
+      "turn-1",
+    );
+
+    assert.deepStrictEqual(streamed, [
+      {
+        id: "turn-1:item-1",
+        kind: "assistant",
+        text: "你好！很高兴见到你。",
+        turnId: "turn-1",
+      },
+    ]);
+  });
+
+  test("rebuilds history without reintroducing adjacent assistant duplicates", () => {
+    const thread = {
+      id: "thread-1",
+      preview: "",
+      modelProvider: "",
+      createdAt: Date.now(),
+      path: "",
+      cwd: "",
+      cliVersion: "",
+      source: "unknown",
+      gitInfo: null,
+      turns: [
+        {
+          id: "turn-1",
+          status: "completed",
+          error: null,
+          items: [
+            {
+              type: "agentMessage",
+              id: "item-1",
+              text: "你好！很高兴见到你。",
+            },
+            {
+              type: "agentMessage",
+              id: "item-2",
+              text: "你好！很高兴见到你。",
+            },
+          ],
+        },
+        {
+          id: "turn-2",
+          status: "completed",
+          error: null,
+          items: [
+            {
+              type: "agentMessage",
+              id: "item-1",
+              text: "第二轮回复",
+            },
+          ],
+        },
+      ],
+    } as Thread;
+
+    assert.deepStrictEqual(extractMessagesFromThread(thread), [
+      {
+        id: "turn-1:item-1",
+        kind: "assistant",
+        text: "你好！很高兴见到你。",
+        turnId: "turn-1",
+      },
+      {
+        id: "turn-2:item-1",
+        kind: "assistant",
+        text: "第二轮回复",
+        turnId: "turn-2",
+      },
+    ]);
+  });
+
+  test("merges chunked adjacent assistant segments from the same turn", () => {
+    const messages = upsertMessage(
+      [
+        {
+          id: "turn-1:item-1",
+          kind: "assistant",
+          text: "你",
+          turnId: "turn-1",
+        } as UiMessage,
+      ],
+      {
+        id: "turn-1:item-2",
+        kind: "assistant",
+        text: "好！很高兴见到你。",
+        turnId: "turn-1",
+      } as UiMessage,
+    );
+
+    assert.deepStrictEqual(messages, [
+      {
+        id: "turn-1:item-1",
+        kind: "assistant",
+        text: "你好！很高兴见到你。",
+        turnId: "turn-1",
+      },
+    ]);
+  });
+
+  test("keeps assistant messages separated when another item is between them", () => {
+    const thread = {
+      id: "thread-2",
+      preview: "",
+      modelProvider: "",
+      createdAt: Date.now(),
+      path: "",
+      cwd: "",
+      cliVersion: "",
+      source: "unknown",
+      gitInfo: null,
+      turns: [
+        {
+          id: "turn-1",
+          status: "completed",
+          error: null,
+          items: [
+            {
+              type: "agentMessage",
+              id: "item-1",
+              text: "先说明一下接下来要做什么。",
+            },
+            {
+              type: "reasoning",
+              id: "item-2",
+              summary: ["思考过程"],
+              content: [],
+            },
+            {
+              type: "agentMessage",
+              id: "item-3",
+              text: "下面是最终答复。",
+            },
+          ],
+        },
+      ],
+    } as Thread;
+
+    assert.deepStrictEqual(extractMessagesFromThread(thread), [
+      {
+        id: "turn-1:item-1",
+        kind: "assistant",
+        text: "先说明一下接下来要做什么。",
+        turnId: "turn-1",
+      },
+      {
+        id: "turn-1:item-2",
+        kind: "reasoning",
+        summary: ["思考过程"],
+        content: [],
+      },
+      {
+        id: "turn-1:item-3",
+        kind: "assistant",
+        text: "下面是最终答复。",
+        turnId: "turn-1",
+      },
+    ]);
+  });
+});
diff --git a/kagent-ui/lib/assistant/messages.ts b/kagent-ui/lib/assistant/messages.ts
index 637fd85..8e3745d 100644
--- a/kagent-ui/lib/assistant/messages.ts
+++ b/kagent-ui/lib/assistant/messages.ts
@@ -3,7 +3,10 @@
 import type { Thread as CodexThread } from "@/lib/codex-app-server/v2/Thread";
 import type { ThreadItem } from "@/lib/codex-app-server/v2/ThreadItem";
 import type { UserInput } from "@/lib/codex-app-server/v2/UserInput";
-import type { UiMessage, UserAttachment } from "@/components/assistant-ui/thread";
+import type {
+  UiMessage,
+  UserAttachment,
+} from "@/components/assistant-ui/thread";
 import { buildScopedItemId, overrideThreadItemId } from "@/lib/assistant/utils";
 
 export function extractMessagesFromThread(thread: CodexThread): UiMessage[] {
@@ -11,8 +14,11 @@ export function extractMessagesFromThread(thread: CodexThread): UiMessage[] {
   for (const turn of thread.turns ?? []) {
     const items = sortThreadItemsById(turn.items ?? []);
     for (const item of items) {
-      const scoped = overrideThreadItemId(item, buildScopedItemId(turn.id, item.id));
-      const msg = threadItemToUiMessage(scoped);
+      const scoped = overrideThreadItemId(
+        item,
+        buildScopedItemId(turn.id, item.id),
+      );
+      const msg = threadItemToUiMessage(scoped, turn.id);
       if (!msg) continue;
       appendMergedAssistantMessage(msgs, msg);
     }
@@ -20,7 +26,10 @@ export function extractMessagesFromThread(thread: CodexThread): UiMessage[] {
   return msgs;
 }
 
-export function threadItemToUiMessage(item: ThreadItem): UiMessage | null {
+export function threadItemToUiMessage(
+  item: ThreadItem,
+  turnId?: string,
+): UiMessage | null {
   switch (item.type) {
     case "userMessage": {
       const { text, attachments } = userInputToText(item.content);
@@ -28,9 +37,14 @@ export function threadItemToUiMessage(item: ThreadItem): UiMessage | null {
       return { id: item.id, kind: "user", text, attachments };
     }
     case "agentMessage":
-      return { id: item.id, kind: "assistant", text: item.text ?? "" };
+      return { id: item.id, kind: "assistant", text: item.text ?? "", turnId };
     case "reasoning":
-      return { id: item.id, kind: "reasoning", summary: item.summary ?? [], content: item.content ?? [] };
+      return {
+        id: item.id,
+        kind: "reasoning",
+        summary: item.summary ?? [],
+        content: item.content ?? [],
+      };
     case "commandExecution":
       return {
         id: item.id,
@@ -78,18 +92,44 @@ export function threadItemToUiMessage(item: ThreadItem): UiMessage | null {
 
 export function upsertMessage(list: UiMessage[], msg: UiMessage): UiMessage[] {
   const idx = list.findIndex((m) => m.id === msg.id);
-  if (idx === -1) return [...list, msg];
-  const next = list.slice();
-  next[idx] = msg;
-  return next;
+  const next = idx === -1 ? [...list, msg] : list.slice();
+  if (idx !== -1) {
+    next[idx] = msg;
+  }
+  return normalizeAdjacentAssistantMessages(next);
 }
 
-export function appendAgentDelta(list: UiMessage[], itemId: string, delta: string): UiMessage[] {
-  return updateMessage(
-    list,
-    itemId,
-    () => ({ id: itemId, kind: "assistant", text: delta }),
-    (msg) => (msg.kind === "assistant" ? { ...msg, text: `${msg.text}${delta}` } : msg),
+export function removeMessagesByIds(
+  list: UiMessage[],
+  ids: Iterable<string>,
+): UiMessage[] {
+  const idSet = new Set(ids);
+  if (idSet.size === 0) return list;
+  return normalizeAdjacentAssistantMessages(
+    list.filter((msg) => !idSet.has(msg.id)),
+  );
+}
+
+export function appendAgentDelta(
+  list: UiMessage[],
+  itemId: string,
+  delta: string,
+  turnId?: string,
+): UiMessage[] {
+  return normalizeAdjacentAssistantMessages(
+    updateMessage(
+      list,
+      itemId,
+      () => ({ id: itemId, kind: "assistant", text: delta, turnId }),
+      (msg) =>
+        msg.kind === "assistant"
+          ? {
+              ...msg,
+              text: `${msg.text}${delta}`,
+              turnId: msg.turnId ?? turnId,
+            }
+          : msg,
+    ),
   );
 }
 
@@ -133,7 +173,11 @@ export function appendReasoningContentDelta(
   );
 }
 
-export function appendCommandOutputDelta(list: UiMessage[], itemId: string, delta: string): UiMessage[] {
+export function appendCommandOutputDelta(
+  list: UiMessage[],
+  itemId: string,
+  delta: string,
+): UiMessage[] {
   return updateMessage(
     list,
     itemId,
@@ -155,11 +199,21 @@ export function appendCommandOutputDelta(list: UiMessage[], itemId: string, delt
   );
 }
 
-export function appendFileChangeOutputDelta(list: UiMessage[], itemId: string, delta: string): UiMessage[] {
+export function appendFileChangeOutputDelta(
+  list: UiMessage[],
+  itemId: string,
+  delta: string,
+): UiMessage[] {
   return updateMessage(
     list,
     itemId,
-    () => ({ id: itemId, kind: "fileChange", status: "inProgress", changes: [], output: delta }),
+    () => ({
+      id: itemId,
+      kind: "fileChange",
+      status: "inProgress",
+      changes: [],
+      output: delta,
+    }),
     (msg) => {
       if (msg.kind !== "fileChange") return msg;
       const output = `${msg.output ?? ""}${delta}`;
@@ -168,7 +222,11 @@ export function appendFileChangeOutputDelta(list: UiMessage[], itemId: string, d
   );
 }
 
-export function appendMcpToolProgress(list: UiMessage[], itemId: string, message: string): UiMessage[] {
+export function appendMcpToolProgress(
+  list: UiMessage[],
+  itemId: string,
+  message: string,
+): UiMessage[] {
   return updateMessage(
     list,
     itemId,
@@ -205,7 +263,10 @@ function updateMessage(
   return next;
 }
 
-function userInputToText(content: Array<UserInput>): { text: string; attachments: UserAttachment[] } {
+function userInputToText(content: Array<UserInput>): {
+  text: string;
+  attachments: UserAttachment[];
+} {
   const attachments: UserAttachment[] = [];
   const text = content
     .map((c) => {
@@ -231,14 +292,63 @@ function appendMergedAssistantMessage(list: UiMessage[], msg: UiMessage): void {
     return;
   }
   const last = list[list.length - 1];
-  if (last && last.kind === "assistant") {
-    // 恢复历史记录时将拆分的 assistant 消息按顺序拼接
-    last.text = `${last.text}${msg.text}`;
+  if (
+    last &&
+    last.kind === "assistant" &&
+    shouldCoalesceAssistantMessages(last, msg)
+  ) {
+    // 恢复历史记录时将同一 turn 中相邻的 assistant 消息归并成一个气泡
+    list[list.length - 1] = mergeAssistantMessages(last, msg);
     return;
   }
   list.push(msg);
 }
 
+function normalizeAdjacentAssistantMessages(list: UiMessage[]): UiMessage[] {
+  const normalized: UiMessage[] = [];
+  for (const msg of list) {
+    const last = normalized[normalized.length - 1];
+    if (
+      last &&
+      last.kind === "assistant" &&
+      msg.kind === "assistant" &&
+      shouldCoalesceAssistantMessages(last, msg)
+    ) {
+      normalized[normalized.length - 1] = mergeAssistantMessages(last, msg);
+      continue;
+    }
+    normalized.push(msg);
+  }
+  return normalized;
+}
+
+function mergeAssistantMessages(
+  current: Extract<UiMessage, { kind: "assistant" }>,
+  incoming: Extract<UiMessage, { kind: "assistant" }>,
+): Extract<UiMessage, { kind: "assistant" }> {
+  return {
+    ...current,
+    text: mergeAssistantText(current.text, incoming.text),
+    turnId: current.turnId ?? incoming.turnId,
+  };
+}
+
+function shouldCoalesceAssistantMessages(
+  current: Extract<UiMessage, { kind: "assistant" }>,
+  incoming: Extract<UiMessage, { kind: "assistant" }>,
+): boolean {
+  return !!current.turnId && current.turnId === incoming.turnId;
+}
+
+function mergeAssistantText(current: string, incoming: string): string {
+  if (!incoming) return current;
+  if (!current) return incoming;
+  if (current === incoming) return current;
+  if (incoming.startsWith(current)) return incoming;
+  if (current.startsWith(incoming)) return current;
+  return `${current}${incoming}`;
+}
+
 function sortThreadItemsById(items: Array<ThreadItem>): Array<ThreadItem> {
   if (items.length <= 1) return items;
   const parsed = items.map((item, idx) => {