diff --git a/docs/【编辑器】画布Agent对话面板-2026-07-03.md b/docs/【编辑器】画布Agent对话面板-2026-07-03.md
index 2526044dd..145305da9 100644
--- a/docs/【编辑器】画布Agent对话面板-2026-07-03.md
+++ b/docs/【编辑器】画布Agent对话面板-2026-07-03.md
@@ -60,8 +60,13 @@
 - 对话框与既有任务侧栏（`ImageCanvasTaskSidebarView`）**互斥展开**：展开一个自动收起另一个；各自收起后保留入口按钮。
 - 对话框与左侧素材 / 图层侧栏**不互斥**，允许同时展开，便于在对话中选取和核对画布素材；左侧栏切换不改变 Agent 面板开关状态。
 - 桌面端对话框固定宽约 360–400px；移动端抽屉式全宽覆盖；收起态为胶囊/圆形入口按钮。
+- 底部消息输入框随输入内容从单行高度自动增长，最大高度为
+  128px；输入框及其 Enter 提交、原生自适应和兼容降级统一封装在独立 `EditorAgentDraftTextarea` 组件中。支持 `field-sizing: content` 的浏览器使用原生内容尺寸自适应，不支持该属性的旧 Safari / iOS WebView 使用前端测量降级，并在宽度变化时重新计算换行高度。内容超过最大高度后停止增长并启用内部纵向滚动，内容缩短或清空后同步收缩。内部滚动条使用浅灰窄滑块和透明轨道，上下留白不得溢出输入框圆角边界；输入框在窄屏下允许收缩且不产生横向滚动。
+- Enter 发送必须同时排除 `isComposing` 和旧 Safari / WebKit 候选词确认事件的 `keyCode === 229`，避免输入法选词时误发送。
 - 会话管理入口在对话框头部：当前会话标题 + 历史会话下拉（按更新时间倒序）+ 新建对话按钮，全部包在对话框内。
-- 快速切换会话或会话轮询刷新产生并发详情请求时，前端只允许最后发起的请求更新当前会话、消息、错误和加载态；旧响应不得覆盖用户最新选择。
+- 当前会话没有任何已发送消息时，新建对话按钮置灰且不可点击；输入框草稿和未发送附件不算会话内容。当前会话已有消息时可新建，新建成功后只切换到返回的空白会话，输入文字、附件及附件选择状态与切换历史会话时一样原样保留，旧会话继续保留在历史会话下拉中；创建失败同样不修改草稿。
+- 新会话创建请求 pending 时禁用历史会话下拉和发送动作，但输入框与附件仍可编辑；会话列表或历史消息加载期间同样禁用发送。表单提交处理器必须复用相同门禁，不能先清空草稿再由 hook 静默跳过发送。
+- 快速切换会话或会话轮询刷新产生并发详情请求时，每个请求必须获得唯一且单调递增的请求序号；前端只允许最后发起且有权生效的请求更新当前会话、消息、错误和加载态。被正在进行的会话切换压制的旧会话 refresh 不得提前结束新切换的加载态，旧响应也不得覆盖用户最新选择。
 - 普通 JSON 消息请求的回包必须绑定发送时的会话：用户在等待期间切换到其他会话后，只更新原会话的列表摘要，不得把原会话的 `deltaMessages` 、错误或画布刷新副作用应用到当前面板。
 - 收起对话框只是隐藏面板，不卸载当前会话 hook；普通 JSON 消息请求的等待态和外部生成任务状态必须在收起 / 重新打开之间保持一致。
 
diff --git a/src/components/image-editor/EditorAgentConversation/EditorAgentConversationPanelView.test.tsx b/src/components/image-editor/EditorAgentConversation/EditorAgentConversationPanelView.test.tsx
index 576ce756b..77cf831f6 100644
--- a/src/components/image-editor/EditorAgentConversation/EditorAgentConversationPanelView.test.tsx
+++ b/src/components/image-editor/EditorAgentConversation/EditorAgentConversationPanelView.test.tsx
@@ -11,6 +11,7 @@ import {
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
 import type {
+  EditorAgentConversationDetail,
   EditorAgentMessage,
   EditorAgentMessageResponse,
 } from '@/packages/shared/src/contracts';
@@ -264,11 +265,13 @@ describe('EditorAgentConversationPanelView', () => {
       expect(screen.getByText('已经看到画布内容')).toBeTruthy();
     });
 
-    fireEvent.click(screen.getByRole('button', { name: '新建对话' }));
-    await waitFor(() => {
-      expect(client.createConversation).toHaveBeenCalledWith('project-1', {});
+    const newConversationButton = screen.getByRole('button', {
+      name: '新建对话',
+    }) as HTMLButtonElement;
+    expect(newConversationButton.disabled).toBe(false);
+    fireEvent.change(screen.getByLabelText('发送给画布 Agent'), {
+      target: { value: '应保留到新会话的草稿' },
     });
-
     fireEvent.click(screen.getByRole('button', { name: '添加附件' }));
     const attachmentDialog = screen.getByRole('dialog', {
       name: '选择图片附件',
@@ -294,6 +297,32 @@ describe('EditorAgentConversationPanelView', () => {
       screen.getByText('一二三四五六七八九十甲乙丙丁戊己庚辛壬癸子丑寅卯'),
     ).toBeTruthy();
 
+    fireEvent.click(newConversationButton);
+    await waitFor(() => {
+      expect(client.createConversation).toHaveBeenCalledWith('project-1', {});
+    });
+    await waitFor(() => {
+      expect(
+        (screen.getByLabelText('当前对话') as HTMLSelectElement).value,
+      ).toBe('conversation-2');
+      expect(newConversationButton.disabled).toBe(true);
+    });
+    expect(
+      (screen.getByLabelText('发送给画布 Agent') as HTMLTextAreaElement).value,
+    ).toBe('应保留到新会话的草稿');
+    expect(screen.getByText('角色图层')).toBeTruthy();
+    expect(
+      screen.getByRole('option', { name: '角色参考' }),
+    ).toBeTruthy();
+    expect(screen.getByRole('option', { name: '新对话' })).toBeTruthy();
+
+    fireEvent.change(screen.getByLabelText('发送给画布 Agent'), {
+      target: { value: '尚未发送的草稿' },
+    });
+    expect(newConversationButton.disabled).toBe(true);
+    fireEvent.click(newConversationButton);
+    expect(client.createConversation).toHaveBeenCalledTimes(1);
+
     fireEvent.change(screen.getByLabelText('发送给画布 Agent'), {
       target: { value: '参考附件做像素风' },
     });
@@ -415,6 +444,242 @@ describe('EditorAgentConversationPanelView', () => {
     });
   });
 
+  it('keeps new conversation disabled when the project has no conversation history', async () => {
+    const client = createClient();
+    vi.mocked(client.listConversations).mockResolvedValueOnce([]);
+
+    render(
+      <EditorAgentConversationPanelView
+        open
+        onToggleOpen={vi.fn()}
+        client={client}
+      />,
+    );
+
+    await waitFor(() => {
+      expect(client.listConversations).toHaveBeenCalledWith('project-1');
+      expect(screen.getByText('暂无消息')).toBeTruthy();
+    });
+    const newConversationButton = screen.getByRole('button', {
+      name: '新建对话',
+    }) as HTMLButtonElement;
+    expect(newConversationButton.disabled).toBe(true);
+
+    fireEvent.change(screen.getByLabelText('发送给画布 Agent'), {
+      target: { value: '未发送内容' },
+    });
+    expect(newConversationButton.disabled).toBe(true);
+    fireEvent.click(newConversationButton);
+    expect(client.createConversation).not.toHaveBeenCalled();
+  });
+
+  it('preserves the current conversation draft when creating a conversation fails', async () => {
+    const client = createClient();
+    vi.mocked(client.createConversation).mockRejectedValueOnce(
+      new Error('创建新会话失败'),
+    );
+
+    render(
+      <EditorAgentConversationPanelView
+        open
+        onToggleOpen={vi.fn()}
+        client={client}
+      />,
+    );
+
+    await waitFor(() => {
+      expect(screen.getByText('已经看到画布内容')).toBeTruthy();
+    });
+    fireEvent.change(screen.getByLabelText('发送给画布 Agent'), {
+      target: { value: '需要保留的草稿' },
+    });
+    fireEvent.click(screen.getByRole('button', { name: '新建对话' }));
+
+    await waitFor(() => {
+      expect(screen.getByText('创建新会话失败')).toBeTruthy();
+    });
+    expect(
+      (screen.getByLabelText('发送给画布 Agent') as HTMLTextAreaElement).value,
+    ).toBe('需要保留的草稿');
+    expect(screen.getByText('已经看到画布内容')).toBeTruthy();
+    expect(
+      (screen.getByLabelText('当前对话') as HTMLSelectElement).value,
+    ).toBe('conversation-1');
+  });
+
+  it('preserves newer draft edits while creating a conversation', async () => {
+    const client = createClient();
+    let resolveCreate!: (detail: EditorAgentConversationDetail) => void;
+    vi.mocked(client.createConversation).mockImplementationOnce(
+      () =>
+        new Promise<EditorAgentConversationDetail>((resolve) => {
+          resolveCreate = resolve;
+        }),
+    );
+
+    render(
+      <EditorAgentConversationPanelView
+        open
+        onToggleOpen={vi.fn()}
+        client={client}
+      />,
+    );
+
+    await waitFor(() => {
+      expect(screen.getByText('已经看到画布内容')).toBeTruthy();
+    });
+    const draftInput = screen.getByLabelText(
+      '发送给画布 Agent',
+    ) as HTMLTextAreaElement;
+    fireEvent.change(draftInput, {
+      target: { value: '旧项目草稿' },
+    });
+    fireEvent.click(screen.getByRole('button', { name: '新建对话' }));
+
+    await waitFor(() => {
+      expect(client.createConversation).toHaveBeenCalledWith('project-1', {});
+      expect(draftInput.disabled).toBe(false);
+    });
+    const conversationSelect = screen.getByLabelText(
+      '当前对话',
+    ) as HTMLSelectElement;
+    const sendButton = screen.getByRole('button', {
+      name: '发送',
+    }) as HTMLButtonElement;
+    expect(conversationSelect.disabled).toBe(true);
+    expect(sendButton.disabled).toBe(true);
+    expect(
+      (screen.getByRole('button', { name: '添加附件' }) as HTMLButtonElement)
+        .disabled,
+    ).toBe(false);
+    fireEvent.change(draftInput, {
+      target: { value: '创建期间更新的草稿' },
+    });
+    fireEvent.submit(draftInput.closest('form') as HTMLFormElement);
+    expect(client.sendMessage).not.toHaveBeenCalled();
+    expect(draftInput.value).toBe('创建期间更新的草稿');
+
+    await act(async () => {
+      resolveCreate({
+        conversationId: 'conversation-2',
+        projectId: 'project-1',
+        title: '新对话',
+        messages: [],
+        createdAt: '2026-07-03T00:01:00.000Z',
+        updatedAt: '2026-07-03T00:01:00.000Z',
+      });
+      await Promise.resolve();
+    });
+    expect(draftInput.value).toBe('创建期间更新的草稿');
+    expect(conversationSelect.value).toBe('conversation-2');
+    expect(conversationSelect.disabled).toBe(false);
+    expect(sendButton.disabled).toBe(false);
+  });
+
+  it('preserves the draft when submission is attempted during conversation loading', async () => {
+    const client = createClient();
+    let resolveConversationLoad!: (
+      detail: EditorAgentConversationDetail,
+    ) => void;
+    vi.mocked(client.listConversations).mockResolvedValueOnce([
+      {
+        conversationId: 'conversation-1',
+        projectId: 'project-1',
+        title: '角色参考',
+        updatedAt: '2026-07-03T00:01:00.000Z',
+      },
+      {
+        conversationId: 'conversation-2',
+        projectId: 'project-1',
+        title: '背景参考',
+        updatedAt: '2026-07-03T00:00:00.000Z',
+      },
+    ]);
+    vi.mocked(client.getConversation)
+      .mockResolvedValueOnce({
+        conversationId: 'conversation-1',
+        projectId: 'project-1',
+        title: '角色参考',
+        messages: [
+          {
+            id: 0,
+            role: 'assistant',
+            text: '已经看到画布内容',
+            attachments: [],
+            toolCall: null,
+            createdAt: '2026-07-03T00:00:10.000Z',
+          },
+        ],
+        createdAt: '2026-07-03T00:00:00.000Z',
+        updatedAt: '2026-07-03T00:00:10.000Z',
+      })
+      .mockImplementationOnce(
+        () =>
+          new Promise<EditorAgentConversationDetail>((resolve) => {
+            resolveConversationLoad = resolve;
+          }),
+      );
+
+    render(
+      <EditorAgentConversationPanelView
+        open
+        onToggleOpen={vi.fn()}
+        client={client}
+      />,
+    );
+
+    await waitFor(() => {
+      expect(screen.getByText('已经看到画布内容')).toBeTruthy();
+    });
+    const draftInput = screen.getByLabelText(
+      '发送给画布 Agent',
+    ) as HTMLTextAreaElement;
+    const conversationSelect = screen.getByLabelText(
+      '当前对话',
+    ) as HTMLSelectElement;
+    fireEvent.change(draftInput, {
+      target: { value: '切换期间必须保留的草稿' },
+    });
+    fireEvent.change(conversationSelect, {
+      target: { value: 'conversation-2' },
+    });
+
+    const sendButton = screen.getByRole('button', {
+      name: '发送',
+    }) as HTMLButtonElement;
+    await waitFor(() => {
+      expect(client.getConversation).toHaveBeenCalledWith('conversation-2');
+      expect(sendButton.disabled).toBe(true);
+    });
+    fireEvent.submit(draftInput.closest('form') as HTMLFormElement);
+    expect(client.sendMessage).not.toHaveBeenCalled();
+    expect(draftInput.value).toBe('切换期间必须保留的草稿');
+
+    await act(async () => {
+      resolveConversationLoad({
+        conversationId: 'conversation-2',
+        projectId: 'project-1',
+        title: '背景参考',
+        messages: [
+          {
+            id: 1,
+            role: 'assistant',
+            text: '背景会话内容',
+            attachments: [],
+            toolCall: null,
+            createdAt: '2026-07-03T00:02:00.000Z',
+          },
+        ],
+        createdAt: '2026-07-03T00:00:00.000Z',
+        updatedAt: '2026-07-03T00:02:00.000Z',
+      });
+      await Promise.resolve();
+    });
+    expect(await screen.findByText('背景会话内容')).toBeTruthy();
+    expect(draftInput.value).toBe('切换期间必须保留的草稿');
+    expect(sendButton.disabled).toBe(false);
+  });
+
   it('disables sending while a message request is pending without showing stop', async () => {
     const client = createClient();
     let resolveSend!: (response: EditorAgentMessageResponse) => void;
diff --git a/src/components/image-editor/EditorAgentConversation/EditorAgentConversationPanelView.tsx b/src/components/image-editor/EditorAgentConversation/EditorAgentConversationPanelView.tsx
index 17a43090c..8d52c8c51 100644
--- a/src/components/image-editor/EditorAgentConversation/EditorAgentConversationPanelView.tsx
+++ b/src/components/image-editor/EditorAgentConversation/EditorAgentConversationPanelView.tsx
@@ -1,5 +1,6 @@
 import {
   Bot,
+  ChevronDown,
   Loader2,
   MessageCircle,
   Paperclip,
@@ -19,6 +20,7 @@ import { PlatformDangerConfirmDialog } from '@/src/components/common/PlatformDan
 import AttachmentChip from '@/src/components/image-editor/EditorAgentConversation/AttachmentChip.tsx';
 import { AttachmentPicker } from '@/src/components/image-editor/EditorAgentConversation/AttachmentPicker.tsx';
 import { attachmentKey } from '@/src/components/image-editor/EditorAgentConversation/common.ts';
+import { EditorAgentDraftTextarea } from '@/src/components/image-editor/EditorAgentConversation/EditorAgentDraftTextarea.tsx';
 import {
   MessageBubble,
   ThinkingBubble,
@@ -69,6 +71,7 @@ export function EditorAgentConversationPanelView({
   const effectiveProjectId = hasConversationMounted ? projectId : null;
   const {
     conversations,
+    activeConversation,
     activeConversationId,
     messages,
     isLoadingConversations,
@@ -118,13 +121,29 @@ export function EditorAgentConversationPanelView({
 
   const hasProject = Boolean(projectId?.trim());
   const isConversationBusy = isWaiting || isToolCallActionPending;
+  const hasCurrentConversationContent = messages.length > 0;
+  const isConversationSelectDisabled =
+    !conversations.length ||
+    isLoadingConversations ||
+    isCreatingConversation ||
+    isConversationBusy;
+  const isMessageSubmissionBlocked =
+    isCreatingConversation ||
+    isLoadingConversations ||
+    isLoadingMessages ||
+    isWaiting ||
+    isToolCallActionPending ||
+    isPastingAttachment ||
+    !hasProject;
+  const currentConversationTitle = activeConversation?.title ?? '新对话';
+
+  const handleCreateConversation = () => {
+    void createConversation().catch(() => undefined);
+  };
 
   const submitMessage = (event: FormEvent<HTMLFormElement>) => {
     event.preventDefault();
-    if (isWaiting) {
-      return;
-    }
-    if (isPastingAttachment) {
+    if (isMessageSubmissionBlocked) {
       return;
     }
     const text = draftText.trim();
@@ -164,43 +183,70 @@ export function EditorAgentConversationPanelView({
       >
         <header className="flex items-center gap-2 border-b border-slate-200 bg-white/90 px-3 py-3">
           <Bot className="h-5 w-5 text-slate-700" aria-hidden="true" />
-          <select
-            className="min-w-0 flex-1 rounded-full border border-slate-200 bg-white px-3 py-2 text-sm text-slate-800"
-            aria-label="当前对话"
-            value={activeConversationId ?? ''}
-            disabled={
-              !conversations.length ||
-              isLoadingConversations ||
-              isConversationBusy
-            }
-            onChange={(event) => {
-              const nextConversationId = event.currentTarget.value;
-              if (nextConversationId) {
-                void selectConversation(nextConversationId);
-              }
-            }}
+          <div
+            className="relative min-w-0 flex-1 rounded-full focus-within:ring-2 focus-within:ring-slate-300"
+            title={currentConversationTitle}
           >
-            {conversations.length ? (
-              conversations.map((conversation) => (
-                <option
-                  key={conversation.conversationId}
-                  value={conversation.conversationId}
-                >
-                  {conversation.title}
-                </option>
-              ))
-            ) : (
-              <option value="">新对话</option>
-            )}
-          </select>
+            <div
+              className={`pointer-events-none flex h-9 w-full items-center rounded-full border border-slate-200 bg-white px-3 pr-10 text-sm ${
+                isConversationSelectDisabled
+                  ? 'text-slate-400'
+                  : 'text-slate-800'
+              }`}
+              aria-hidden="true"
+            >
+              <span
+                className="min-w-0 overflow-hidden text-ellipsis whitespace-nowrap"
+                data-testid="active-conversation-title"
+              >
+                {currentConversationTitle}
+              </span>
+              <ChevronDown
+                className="absolute right-[10px] top-1/2 h-4 w-4 -translate-y-1/2"
+                data-testid="conversation-switch-chevron"
+                aria-hidden="true"
+              />
+            </div>
+            <select
+              className="absolute inset-0 z-10 h-full w-full cursor-pointer appearance-none opacity-0 disabled:cursor-not-allowed"
+              aria-label="当前对话"
+              value={activeConversationId ?? ''}
+              disabled={isConversationSelectDisabled}
+              onChange={(event) => {
+                const nextConversationId = event.currentTarget.value;
+                if (nextConversationId) {
+                  void selectConversation(nextConversationId);
+                }
+              }}
+            >
+              {conversations.length ? (
+                conversations.map((conversation) => (
+                  <option
+                    key={conversation.conversationId}
+                    value={conversation.conversationId}
+                  >
+                    {conversation.title}
+                  </option>
+                ))
+              ) : (
+                <option value="">新对话</option>
+              )}
+            </select>
+          </div>
           <button
             type="button"
             className="inline-flex h-9 w-9 items-center justify-center rounded-full bg-slate-900 text-white disabled:opacity-45"
             aria-label="新建对话"
             disabled={
-              !hasProject || isCreatingConversation || isConversationBusy
+              !hasProject ||
+              !hasCurrentConversationContent ||
+              isLoadingConversations ||
+              isLoadingMessages ||
+              isCreatingConversation ||
+              isConversationBusy ||
+              isPastingAttachment
             }
-            onClick={() => void createConversation()}
+            onClick={handleCreateConversation}
           >
             <Plus className="h-4 w-4" aria-hidden="true" />
           </button>
@@ -312,28 +358,17 @@ export function EditorAgentConversationPanelView({
             >
               <Paperclip className="h-4 w-4" aria-hidden="true" />
             </button>
-            <textarea
-              className="max-h-32 min-h-10 flex-1 resize-none overflow-y-auto overscroll-contain rounded-3xl border border-slate-200 bg-slate-50 px-3 py-2 text-sm text-slate-800 outline-none focus:border-slate-400"
-              aria-label="发送给画布 Agent"
+            <EditorAgentDraftTextarea
               value={draftText}
-              rows={1}
-              onChange={(event) => setDraftText(event.currentTarget.value)}
+              onChange={setDraftText}
               onPaste={handleInputPaste}
-              onKeyDown={(event) => {
-                if (event.key === 'Enter' && !event.shiftKey) {
-                  event.preventDefault();
-                  event.currentTarget.form?.requestSubmit();
-                }
-              }}
             />
             <button
               type="submit"
               className="inline-flex h-10 min-w-16 shrink-0 items-center justify-center gap-1.5 rounded-full bg-slate-900 px-3 text-sm font-semibold text-white disabled:opacity-45"
               disabled={
-                isWaiting ||
-                isToolCallActionPending ||
-                (!draftText.trim() && !attachments.length) ||
-                !hasProject
+                isMessageSubmissionBlocked ||
+                (!draftText.trim() && !attachments.length)
               }
             >
               <Send className="h-3.5 w-3.5" aria-hidden="true" />
diff --git a/src/components/image-editor/EditorAgentConversation/EditorAgentDraftTextarea.test.tsx b/src/components/image-editor/EditorAgentConversation/EditorAgentDraftTextarea.test.tsx
new file mode 100644
index 000000000..717718fc5
--- /dev/null
+++ b/src/components/image-editor/EditorAgentConversation/EditorAgentDraftTextarea.test.tsx
@@ -0,0 +1,132 @@
+/* @vitest-environment jsdom */
+
+import { act, fireEvent, render, screen } from '@testing-library/react';
+import type { FormEvent } from 'react';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import { EditorAgentDraftTextarea } from './EditorAgentDraftTextarea.tsx';
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+});
+
+describe('EditorAgentDraftTextarea', () => {
+  it('uses native field sizing when the browser supports it', () => {
+    const supports = vi.fn().mockReturnValue(true);
+    const resizeObserver = vi.fn();
+    const onChange = vi.fn();
+    vi.stubGlobal('CSS', { supports });
+    vi.stubGlobal('ResizeObserver', resizeObserver);
+
+    render(<EditorAgentDraftTextarea value="" onChange={onChange} />);
+
+    const input = screen.getByLabelText(
+      '发送给画布 Agent',
+    ) as HTMLTextAreaElement;
+    expect(supports).toHaveBeenCalledWith('field-sizing', 'content');
+    expect(resizeObserver).not.toHaveBeenCalled();
+    expect(input.className).toContain('[field-sizing:content]');
+    expect(input.className).toContain('min-h-10');
+    expect(input.className).toContain('max-h-32');
+    expect(input.className).toContain('overflow-y-auto');
+    expect(input.style.height).toBe('');
+
+    fireEvent.change(input, { target: { value: '新草稿' } });
+    expect(onChange).toHaveBeenCalledWith('新草稿');
+  });
+
+  it('falls back to measured sizing and remeasures when width changes', () => {
+    let resizeObserverCallback!: ResizeObserverCallback;
+    const observe = vi.fn();
+    const disconnect = vi.fn();
+    vi.stubGlobal('CSS', { supports: vi.fn().mockReturnValue(false) });
+    vi.stubGlobal(
+      'ResizeObserver',
+      vi.fn().mockImplementation((callback: ResizeObserverCallback) => {
+        resizeObserverCallback = callback;
+        return {
+          observe,
+          unobserve: vi.fn(),
+          disconnect,
+        };
+      }),
+    );
+
+    const { rerender, unmount } = render(
+      <EditorAgentDraftTextarea value="" onChange={vi.fn()} />,
+    );
+    const input = screen.getByLabelText(
+      '发送给画布 Agent',
+    ) as HTMLTextAreaElement;
+    expect(observe).toHaveBeenCalledWith(input);
+    let contentHeight = 92;
+    Object.defineProperty(input, 'offsetHeight', {
+      configurable: true,
+      get: () => {
+        const styleHeight = Number.parseFloat(input.style.height);
+        return Number.isNaN(styleHeight) ? 42 : styleHeight;
+      },
+    });
+    Object.defineProperty(input, 'clientHeight', {
+      configurable: true,
+      get: () => input.offsetHeight - 2,
+    });
+    Object.defineProperty(input, 'scrollHeight', {
+      configurable: true,
+      get: () => contentHeight,
+    });
+
+    rerender(
+      <EditorAgentDraftTextarea
+        value="第一行\n第二行\n第三行\n第四行\n第五行"
+        onChange={vi.fn()}
+      />,
+    );
+    expect(input.style.height).toBe('94px');
+    expect(input.style.overflowY).toBe('hidden');
+    expect(input.scrollHeight).toBeLessThanOrEqual(input.clientHeight);
+
+    contentHeight = 180;
+    act(() => {
+      resizeObserverCallback(
+        [
+          {
+            target: input,
+            contentRect: { width: 180 },
+          } as unknown as ResizeObserverEntry,
+        ],
+        {} as ResizeObserver,
+      );
+    });
+    expect(input.style.height).toBe('128px');
+    expect(input.style.overflowY).toBe('auto');
+
+    unmount();
+    expect(disconnect).toHaveBeenCalledTimes(1);
+  });
+
+  it('submits on Enter and keeps line breaks or IME confirmation from submitting', () => {
+    const onSubmit = vi.fn((event: FormEvent<HTMLFormElement>) => {
+      event.preventDefault();
+    });
+    render(
+      <form onSubmit={onSubmit}>
+        <EditorAgentDraftTextarea value="草稿" onChange={vi.fn()} />
+      </form>,
+    );
+
+    const input = screen.getByLabelText('发送给画布 Agent');
+    fireEvent.keyDown(input, { key: 'Enter', shiftKey: true });
+    expect(onSubmit).not.toHaveBeenCalled();
+
+    fireEvent.keyDown(input, {
+      key: 'Enter',
+      isComposing: false,
+      keyCode: 229,
+    });
+    expect(onSubmit).not.toHaveBeenCalled();
+
+    fireEvent.keyDown(input, { key: 'Enter' });
+    expect(onSubmit).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/src/components/image-editor/EditorAgentConversation/EditorAgentDraftTextarea.tsx b/src/components/image-editor/EditorAgentConversation/EditorAgentDraftTextarea.tsx
new file mode 100644
index 000000000..74d57d75c
--- /dev/null
+++ b/src/components/image-editor/EditorAgentConversation/EditorAgentDraftTextarea.tsx
@@ -0,0 +1,113 @@
+import {
+  type ClipboardEventHandler,
+  type KeyboardEvent,
+  useLayoutEffect,
+  useRef,
+} from 'react';
+
+const DRAFT_MIN_HEIGHT_PX = 40;
+const DRAFT_MAX_HEIGHT_PX = 128;
+
+// for fallback on some browser
+function supportsNativeFieldSizing() {
+  return (
+    typeof CSS !== 'undefined' &&
+    typeof CSS.supports === 'function' &&
+    CSS.supports('field-sizing', 'content')
+  );
+}
+
+function resizeFallbackTextarea(textarea: HTMLTextAreaElement) {
+  textarea.style.height = 'auto';
+  const contentHeight = textarea.scrollHeight;
+  const borderHeight = Math.max(
+    0,
+    textarea.offsetHeight - textarea.clientHeight,
+  );
+  const borderBoxContentHeight = contentHeight + borderHeight;
+  const nextHeight = Math.min(
+    Math.max(borderBoxContentHeight, DRAFT_MIN_HEIGHT_PX),
+    DRAFT_MAX_HEIGHT_PX,
+  );
+  textarea.style.height = `${nextHeight}px`;
+  textarea.style.overflowY =
+    borderBoxContentHeight > DRAFT_MAX_HEIGHT_PX ? 'auto' : 'hidden';
+}
+
+export function EditorAgentDraftTextarea({
+  value,
+  onChange,
+  onPaste,
+}: {
+  value: string;
+  onChange: (value: string) => void;
+  onPaste?: ClipboardEventHandler<HTMLTextAreaElement>;
+}) {
+  const textareaRef = useRef<HTMLTextAreaElement>(null);
+
+  useLayoutEffect(() => {
+    const textarea = textareaRef.current;
+    if (!textarea || supportsNativeFieldSizing()) {
+      return;
+    }
+    resizeFallbackTextarea(textarea);
+  }, [value]);
+
+  useLayoutEffect(() => {
+    const textarea = textareaRef.current;
+    if (!textarea || supportsNativeFieldSizing()) {
+      return undefined;
+    }
+
+    let previousWidth = textarea.getBoundingClientRect().width;
+    const resizeWhenWidthChanges = (nextWidth: number) => {
+      if (Math.abs(nextWidth - previousWidth) < 0.5) {
+        return;
+      }
+      previousWidth = nextWidth;
+      resizeFallbackTextarea(textarea);
+    };
+
+    if (typeof ResizeObserver !== 'undefined') {
+      const observer = new ResizeObserver((entries) => {
+        const entry = entries[0];
+        if (entry) {
+          resizeWhenWidthChanges(entry.contentRect.width);
+        }
+      });
+      observer.observe(textarea);
+      return () => observer.disconnect();
+    }
+
+    const handleWindowResize = () => {
+      resizeWhenWidthChanges(textarea.getBoundingClientRect().width);
+    };
+    window.addEventListener('resize', handleWindowResize);
+    return () => window.removeEventListener('resize', handleWindowResize);
+  }, []);
+
+  const handleKeyDown = (event: KeyboardEvent<HTMLTextAreaElement>) => {
+    if (
+      event.key === 'Enter' &&
+      !event.shiftKey &&
+      !event.nativeEvent.isComposing &&
+      event.nativeEvent.keyCode !== 229
+    ) {
+      event.preventDefault();
+      event.currentTarget.form?.requestSubmit();
+    }
+  };
+
+  return (
+    <textarea
+      ref={textareaRef}
+      className="editor-agent-conversation__draft-input max-h-32 min-h-10 min-w-0 flex-1 resize-none overflow-x-hidden overflow-y-auto overscroll-contain rounded-3xl border border-slate-200 bg-slate-50 px-3 py-2 text-sm text-slate-800 outline-none [field-sizing:content] focus:border-slate-400"
+      aria-label="发送给画布 Agent"
+      value={value}
+      rows={1}
+      onChange={(event) => onChange(event.currentTarget.value)}
+      onPaste={onPaste}
+      onKeyDown={handleKeyDown}
+    />
+  );
+}
diff --git a/src/components/image-editor/EditorAgentConversation/useEditorAgentConversation.test.tsx b/src/components/image-editor/EditorAgentConversation/useEditorAgentConversation.test.tsx
index d50e29f2a..03ff1b3c8 100644
--- a/src/components/image-editor/EditorAgentConversation/useEditorAgentConversation.test.tsx
+++ b/src/components/image-editor/EditorAgentConversation/useEditorAgentConversation.test.tsx
@@ -265,6 +265,268 @@ describe('useEditorAgentConversation', () => {
     expect(result.current.isLoadingMessages).toBe(false);
   });
 
+  it('does not let a refresh supersede an in-flight conversation activation', async () => {
+    const client = createClient();
+    let resolveActivation!: (detail: EditorAgentConversationDetail) => void;
+    let resolveRefresh!: (detail: EditorAgentConversationDetail) => void;
+    const activationPromise = new Promise<EditorAgentConversationDetail>(
+      (resolve) => {
+        resolveActivation = resolve;
+      },
+    );
+    const refreshPromise = new Promise<EditorAgentConversationDetail>(
+      (resolve) => {
+        resolveRefresh = resolve;
+      },
+    );
+    const { result } = renderHook(() =>
+      useEditorAgentConversation({ projectId: 'project-1', client }),
+    );
+
+    await waitFor(() => {
+      expect(result.current.activeConversationId).toBe('conversation-1');
+    });
+    vi.mocked(client.getConversation).mockImplementation((conversationId) => {
+      if (conversationId === 'conversation-2') {
+        return activationPromise;
+      }
+      if (conversationId === 'conversation-1') {
+        return refreshPromise;
+      }
+      throw new Error(`Unexpected conversation: ${conversationId}`);
+    });
+
+    let pendingActivation!: Promise<EditorAgentConversationDetail | null>;
+    let pendingRefresh!: Promise<EditorAgentConversationDetail | null>;
+    act(() => {
+      pendingActivation = result.current.selectConversation('conversation-2');
+      pendingRefresh = result.current.refreshActiveConversation();
+    });
+
+    await act(async () => {
+      resolveRefresh({
+        conversationId: 'conversation-1',
+        projectId: 'project-1',
+        title: '旧会话刷新结果',
+        messages: [
+          {
+            id: 10,
+            role: 'assistant',
+            text: '旧会话刷新消息',
+            attachments: [],
+            toolCall: null,
+            createdAt: '2026-07-03T00:02:00.000Z',
+          },
+        ],
+        createdAt: '2026-07-03T00:00:00.000Z',
+        updatedAt: '2026-07-03T00:02:00.000Z',
+      });
+      await pendingRefresh;
+    });
+    expect(result.current.activeConversationId).toBe('conversation-1');
+    expect(result.current.messages).toEqual([]);
+
+    await act(async () => {
+      resolveActivation({
+        conversationId: 'conversation-2',
+        projectId: 'project-1',
+        title: '第二个会话',
+        messages: [
+          {
+            id: 20,
+            role: 'assistant',
+            text: '第二个会话消息',
+            attachments: [],
+            toolCall: null,
+            createdAt: '2026-07-03T00:03:00.000Z',
+          },
+        ],
+        createdAt: '2026-07-03T00:03:00.000Z',
+        updatedAt: '2026-07-03T00:03:00.000Z',
+      });
+      await pendingActivation;
+    });
+
+    expect(result.current.activeConversationId).toBe('conversation-2');
+    expect(result.current.messages[0]?.text).toBe('第二个会话消息');
+    expect(result.current.isLoadingMessages).toBe(false);
+  });
+
+  it('keeps the latest activation loading while an older suppressed refresh finishes', async () => {
+    const client = createClient();
+    let resolveConversation2!: (detail: EditorAgentConversationDetail) => void;
+    let resolveRefresh!: (detail: EditorAgentConversationDetail) => void;
+    let resolveConversation3!: (detail: EditorAgentConversationDetail) => void;
+    const conversation2Promise = new Promise<EditorAgentConversationDetail>(
+      (resolve) => {
+        resolveConversation2 = resolve;
+      },
+    );
+    const refreshPromise = new Promise<EditorAgentConversationDetail>(
+      (resolve) => {
+        resolveRefresh = resolve;
+      },
+    );
+    const conversation3Promise = new Promise<EditorAgentConversationDetail>(
+      (resolve) => {
+        resolveConversation3 = resolve;
+      },
+    );
+    const { result } = renderHook(() =>
+      useEditorAgentConversation({ projectId: 'project-1', client }),
+    );
+
+    await waitFor(() => {
+      expect(result.current.activeConversationId).toBe('conversation-1');
+    });
+    vi.mocked(client.getConversation).mockImplementation((conversationId) => {
+      if (conversationId === 'conversation-2') {
+        return conversation2Promise;
+      }
+      if (conversationId === 'conversation-1') {
+        return refreshPromise;
+      }
+      if (conversationId === 'conversation-3') {
+        return conversation3Promise;
+      }
+      throw new Error(`Unexpected conversation: ${conversationId}`);
+    });
+
+    let conversation2Load!: Promise<EditorAgentConversationDetail | null>;
+    let pendingRefresh!: Promise<EditorAgentConversationDetail | null>;
+    let conversation3Load!: Promise<EditorAgentConversationDetail | null>;
+    act(() => {
+      conversation2Load = result.current.selectConversation('conversation-2');
+      pendingRefresh = result.current.refreshActiveConversation();
+      conversation3Load = result.current.selectConversation('conversation-3');
+    });
+    expect(result.current.isLoadingMessages).toBe(true);
+
+    await act(async () => {
+      resolveRefresh({
+        conversationId: 'conversation-1',
+        projectId: 'project-1',
+        title: '旧会话刷新结果',
+        messages: [],
+        createdAt: '2026-07-03T00:00:00.000Z',
+        updatedAt: '2026-07-03T00:02:00.000Z',
+      });
+      await pendingRefresh;
+    });
+
+    expect(result.current.activeConversationId).toBe('conversation-1');
+    expect(result.current.isLoadingMessages).toBe(true);
+    await act(async () => {
+      await result.current.sendMessage('切换期间不应发送');
+    });
+    expect(client.sendMessage).not.toHaveBeenCalled();
+
+    await act(async () => {
+      resolveConversation3({
+        conversationId: 'conversation-3',
+        projectId: 'project-1',
+        title: '第三个会话',
+        messages: [
+          {
+            id: 30,
+            role: 'assistant',
+            text: '第三个会话消息',
+            attachments: [],
+            toolCall: null,
+            createdAt: '2026-07-03T00:03:00.000Z',
+          },
+        ],
+        createdAt: '2026-07-03T00:03:00.000Z',
+        updatedAt: '2026-07-03T00:03:00.000Z',
+      });
+      await conversation3Load;
+    });
+    expect(result.current.activeConversationId).toBe('conversation-3');
+    expect(result.current.isLoadingMessages).toBe(false);
+
+    await act(async () => {
+      resolveConversation2({
+        conversationId: 'conversation-2',
+        projectId: 'project-1',
+        title: '第二个会话',
+        messages: [],
+        createdAt: '2026-07-03T00:02:00.000Z',
+        updatedAt: '2026-07-03T00:02:00.000Z',
+      });
+      await conversation2Load;
+    });
+    expect(result.current.activeConversationId).toBe('conversation-3');
+  });
+
+  it('does not let a silent refresh replace a newly created conversation', async () => {
+    const client = createClient();
+    let resolveRefresh!: (detail: EditorAgentConversationDetail) => void;
+    let resolveCreate!: (detail: EditorAgentConversationDetail) => void;
+    const refreshPromise = new Promise<EditorAgentConversationDetail>(
+      (resolve) => {
+        resolveRefresh = resolve;
+      },
+    );
+    const createPromise = new Promise<EditorAgentConversationDetail>(
+      (resolve) => {
+        resolveCreate = resolve;
+      },
+    );
+    const { result } = renderHook(() =>
+      useEditorAgentConversation({ projectId: 'project-1', client }),
+    );
+
+    await waitFor(() => {
+      expect(result.current.activeConversationId).toBe('conversation-1');
+    });
+    vi.mocked(client.getConversation).mockReturnValueOnce(refreshPromise);
+    vi.mocked(client.createConversation).mockReturnValueOnce(createPromise);
+
+    let pendingRefresh!: Promise<EditorAgentConversationDetail | null>;
+    let pendingCreate!: Promise<EditorAgentConversationDetail>;
+    act(() => {
+      pendingRefresh = result.current.refreshActiveConversation();
+      pendingCreate = result.current.createConversation();
+    });
+
+    await act(async () => {
+      resolveCreate({
+        conversationId: 'conversation-2',
+        projectId: 'project-1',
+        title: '新对话',
+        messages: [],
+        createdAt: '2026-07-03T00:01:00.000Z',
+        updatedAt: '2026-07-03T00:01:00.000Z',
+      });
+      await pendingCreate;
+    });
+    expect(result.current.activeConversationId).toBe('conversation-2');
+
+    await act(async () => {
+      resolveRefresh({
+        conversationId: 'conversation-1',
+        projectId: 'project-1',
+        title: '旧对话刷新结果',
+        messages: [
+          {
+            id: 10,
+            role: 'assistant',
+            text: '旧会话消息',
+            attachments: [],
+            toolCall: null,
+            createdAt: '2026-07-03T00:02:00.000Z',
+          },
+        ],
+        createdAt: '2026-07-03T00:00:00.000Z',
+        updatedAt: '2026-07-03T00:02:00.000Z',
+      });
+      await pendingRefresh;
+    });
+
+    expect(result.current.activeConversationId).toBe('conversation-2');
+    expect(result.current.messages).toEqual([]);
+  });
+
   it('appends a lazily reconciled tool message delta', async () => {
     const client = createClient();
     const pendingMessage: EditorAgentMessage = {
diff --git a/src/components/image-editor/EditorAgentConversation/useEditorAgentConversation.ts b/src/components/image-editor/EditorAgentConversation/useEditorAgentConversation.ts
index 765ba77bf..e8f610dd5 100644
--- a/src/components/image-editor/EditorAgentConversation/useEditorAgentConversation.ts
+++ b/src/components/image-editor/EditorAgentConversation/useEditorAgentConversation.ts
@@ -158,7 +158,9 @@ export function useEditorAgentConversation({
   const [errorMessage, setErrorMessage] = useState<string | null>(null);
   const normalizedProjectIdRef = useRef(normalizedProjectId);
   const activeConversationIdRef = useRef<string | null>(null);
+  const pendingActivationConversationIdRef = useRef<string | null>(null);
   const activeToolCallActionRef = useRef<EditorAgentToolCallActionState>(null);
+  const conversationLoadRequestSequenceRef = useRef(0);
   const conversationLoadRequestIdRef = useRef(0);
   const createConversationRequestIdRef = useRef(0);
   const isWaitingRef = useRef(false);
@@ -224,28 +226,57 @@ export function useEditorAgentConversation({
   );
 
   const loadConversation = useCallback(
-    async (conversationId: string, options: { showLoading?: boolean } = {}) => {
-      const requestId = conversationLoadRequestIdRef.current + 1;
-      conversationLoadRequestIdRef.current = requestId;
+    async (
+      conversationId: string,
+      options: {
+        // `activate` may make conversationId active; `refresh` may apply only
+        // while that same conversationId is still active.
+        mode: 'activate' | 'refresh';
+        showLoading?: boolean;
+      },
+    ) => {
+      const requestId = conversationLoadRequestSequenceRef.current + 1;
+      conversationLoadRequestSequenceRef.current = requestId;
+      const maySupersedeCurrentLoad =
+        options.mode === 'activate' ||
+        pendingActivationConversationIdRef.current === null;
+      if (maySupersedeCurrentLoad) {
+        conversationLoadRequestIdRef.current = requestId;
+      }
+      if (options.mode === 'activate') {
+        pendingActivationConversationIdRef.current = conversationId;
+      }
       const showLoading = options.showLoading ?? true;
-      if (showLoading) {
+      const canApplyResult = () =>
+        conversationLoadRequestIdRef.current === requestId &&
+        (options.mode === 'activate' ||
+          (pendingActivationConversationIdRef.current === null &&
+            activeConversationIdRef.current === conversationId));
+      if (showLoading && maySupersedeCurrentLoad) {
         setIsLoadingMessages(true);
       }
       setErrorMessage(null);
       try {
         const detail = await client.getConversation(conversationId);
-        if (conversationLoadRequestIdRef.current === requestId) {
+        if (canApplyResult()) {
           applyConversationDetail(detail);
         }
         return detail;
       } catch (error) {
-        if (conversationLoadRequestIdRef.current === requestId) {
+        if (canApplyResult()) {
           setErrorMessage(
             error instanceof Error ? error.message : '读取画布 Agent 会话失败',
           );
         }
         throw error;
       } finally {
+        if (
+          options.mode === 'activate' &&
+          conversationLoadRequestIdRef.current === requestId &&
+          pendingActivationConversationIdRef.current === conversationId
+        ) {
+          pendingActivationConversationIdRef.current = null;
+        }
         if (conversationLoadRequestIdRef.current === requestId) {
           setIsLoadingMessages(false);
         }
@@ -255,7 +286,11 @@ export function useEditorAgentConversation({
   );
 
   useEffect(() => {
-    conversationLoadRequestIdRef.current += 1;
+    const invalidationRequestId =
+      conversationLoadRequestSequenceRef.current + 1;
+    conversationLoadRequestSequenceRef.current = invalidationRequestId;
+    conversationLoadRequestIdRef.current = invalidationRequestId;
+    pendingActivationConversationIdRef.current = null;
     setIsLoadingMessages(false);
     if (!normalizedProjectId) {
       setConversations([]);
@@ -326,6 +361,12 @@ export function useEditorAgentConversation({
         createConversationRequestIdRef.current === requestId &&
         normalizedProjectIdRef.current === requestedProjectId
       ) {
+        const invalidationRequestId =
+          conversationLoadRequestSequenceRef.current + 1;
+        conversationLoadRequestSequenceRef.current = invalidationRequestId;
+        conversationLoadRequestIdRef.current = invalidationRequestId;
+        pendingActivationConversationIdRef.current = null;
+        setIsLoadingMessages(false);
         applyConversationDetail(detail);
       }
       return detail;
@@ -354,7 +395,7 @@ export function useEditorAgentConversation({
       if (conversationId === activeConversationId) {
         return null;
       }
-      return loadConversation(conversationId);
+      return loadConversation(conversationId, { mode: 'activate' });
     },
     [activeConversationId, loadConversation],
   );
@@ -364,7 +405,10 @@ export function useEditorAgentConversation({
     if (!conversationId) {
       return null;
     }
-    return loadConversation(conversationId, { showLoading: false });
+    return loadConversation(conversationId, {
+      mode: 'refresh',
+      showLoading: false,
+    });
   }, [loadConversation]);
 
   const requestCanvasRefreshForMessages = useCallback(
@@ -374,9 +418,9 @@ export function useEditorAgentConversation({
           const toolCall = message.toolCall;
           return Boolean(
             toolCall?.externalJobId &&
-              (toolCall.images.length > 0 ||
-                (toolCall.videos?.length ?? 0) > 0 ||
-                (toolCall.audios?.length ?? 0) > 0),
+            (toolCall.images.length > 0 ||
+              (toolCall.videos?.length ?? 0) > 0 ||
+              (toolCall.audios?.length ?? 0) > 0),
           );
         })
       ) {
@@ -541,6 +585,7 @@ export function useEditorAgentConversation({
         }
 
         const detail = await loadConversation(conversationId, {
+          mode: 'refresh',
           showLoading: false,
         });
         const updatedMessage = detail.messages.find(
@@ -596,7 +641,9 @@ export function useEditorAgentConversation({
       setConversations(remainingConversations);
       const nextConversation = remainingConversations[0] ?? null;
       if (nextConversation) {
-        await loadConversation(nextConversation.conversationId);
+        await loadConversation(nextConversation.conversationId, {
+          mode: 'activate',
+        });
         return;
       }
       activeConversationIdRef.current = null;
diff --git a/src/index.css b/src/index.css
index 7941510e9..6c057a37b 100644
--- a/src/index.css
+++ b/src/index.css
@@ -16708,6 +16708,31 @@ button {
   background: #3f3f46;
 }
 
+.editor-agent-conversation__draft-input {
+  scrollbar-color: #cbd5e1 transparent;
+  scrollbar-width: thin;
+}
+
+.editor-agent-conversation__draft-input::-webkit-scrollbar {
+  width: 6px;
+}
+
+.editor-agent-conversation__draft-input::-webkit-scrollbar-track {
+  margin-block: 10px;
+  background-color: transparent;
+}
+
+.editor-agent-conversation__draft-input::-webkit-scrollbar-thumb {
+  border: 1px solid transparent;
+  border-radius: 999px;
+  background-color: #cbd5e1;
+  background-clip: padding-box;
+}
+
+.editor-agent-conversation__draft-input::-webkit-scrollbar-thumb:hover {
+  background-color: #94a3b8;
+}
+
 .image-canvas-editor__metadata-dialog.platform-modal-shell {
   border-color: rgba(226, 232, 240, 0.92) !important;
   background: #ffffff !important;