diff --git a/docs/chat-chain-changes/2026-10-24-assistant-avatar-layout.md b/docs/chat-chain-changes/2026-10-24-assistant-avatar-layout.md
new file mode 100644
index 0000000..4648ffd
--- /dev/null
+++ b/docs/chat-chain-changes/2026-10-24-assistant-avatar-layout.md
@@ -0,0 +1,11 @@
+---
+date: 2026-10-24
+pr: pending
+feature: Assistant reply layout
+impact: Assistant reply content starts on a new row below an avatar/profile-name header with aligned left edges on desktop and mobile. Chat events and data are unchanged.
+---
+
+The assistant message body now shows its avatar and profile name on one row,
+with reply content below that header. Long names truncate with a full-name tooltip. Existing
+message width limits, Markdown rendering and actions are retained. Browser checks
+cover vertical placement, left alignment and overflow at 1440, 900 and 390 pixels.
diff --git a/packages/client/src/components/hermes/chat/MessageItem.vue b/packages/client/src/components/hermes/chat/MessageItem.vue
index 809afb5..bf55fff 100644
--- a/packages/client/src/components/hermes/chat/MessageItem.vue
+++ b/packages/client/src/components/hermes/chat/MessageItem.vue
@@ -1012,13 +1012,15 @@ onBeforeUnmount(() => {
     </template>
     <template v-else>
       <div class="msg-body">
-        <ProfileAvatar
-          v-if="message.role === 'assistant'"
-          class="msg-avatar"
-          :name="assistantProfileName"
-          :avatar="assistantProfileAvatar"
-          :size="40"
-        />
+        <div v-if="message.role === 'assistant'" class="msg-agent-header">
+          <ProfileAvatar
+            class="msg-avatar"
+            :name="assistantProfileName"
+            :avatar="assistantProfileAvatar"
+            :size="40"
+          />
+          <span class="msg-profile-name" :title="assistantProfileName">{{ assistantProfileName }}</span>
+        </div>
         <div class="msg-content" :class="message.role">
           <div
             class="message-bubble"
@@ -1317,11 +1319,30 @@ onBeforeUnmount(() => {
     gap: 8px;
 
     .msg-body {
+      flex-direction: column;
       max-width: 80%;
       position: relative;
       z-index: 1;
     }
 
+    .msg-agent-header {
+      display: flex;
+      align-items: center;
+      gap: 10px;
+      min-width: 0;
+      max-width: 100%;
+    }
+
+    .msg-profile-name {
+      min-width: 0;
+      overflow: hidden;
+      text-overflow: ellipsis;
+      white-space: nowrap;
+      color: $text-secondary;
+      font-size: 13px;
+      font-weight: 600;
+    }
+
     .msg-avatar {
       width: 40px;
       height: 40px;
diff --git a/tests/e2e/chat-rendering-smoke.spec.ts b/tests/e2e/chat-rendering-smoke.spec.ts
index 96fd347..aecad8b 100644
--- a/tests/e2e/chat-rendering-smoke.spec.ts
+++ b/tests/e2e/chat-rendering-smoke.spec.ts
@@ -102,3 +102,45 @@ test('opens the session model dialog and the session search from the chat header
   await page.getByRole('button', { name: /search/i }).first().click()
   await expect(page.getByPlaceholder(/search/i).first()).toBeVisible()
 })
+
+
+test('assistant replies start below the avatar and profile name on desktop and mobile', async ({ page }, testInfo) => {
+  await authenticate(page, TEST_ACCESS_KEY, 'research')
+  await mockHermesApi(page)
+  await mockChatSocket(page)
+  await page.goto('/#/hermes/chat')
+  await sendChatMessage(page, '检查一下服务状态')
+  const { sessionId } = await waitForRunSessionId(page)
+  await page.evaluate((sid) => {
+    const socket = (window as any).__PW_CHAT_SOCKET__.latest
+    socket.__trigger('message.delta', {
+      event: 'message.delta', session_id: sid, run_id: 'avatar-layout',
+      delta: 'UI 收到，通信正常。\n\n这台机器状态：Hermes Web UI 跑在 8648 端口，一切照旧。有活直接说，我随时待命。',
+    })
+    socket.__trigger('run.completed', { event: 'run.completed', session_id: sid, run_id: 'avatar-layout' })
+  }, sessionId)
+  const message = page.locator('.message.assistant').last()
+  const avatar = message.locator('.msg-avatar')
+  const profileName = message.locator('.msg-profile-name')
+  await expect(profileName).toHaveText('research')
+  const bubble = message.locator('.message-bubble')
+  await expect(bubble).toContainText('UI 收到，通信正常。')
+  for (const width of [1440, 900, 390]) {
+    await page.setViewportSize({ width, height: 900 })
+    await expect.poll(async () => {
+      const image = await avatar.boundingBox()
+      const reply = await bubble.boundingBox()
+      return image && reply ? reply.y - (image.y + image.height) : -1
+    }).toBeGreaterThanOrEqual(6)
+    const image = (await avatar.boundingBox())!
+    const reply = (await bubble.boundingBox())!
+    const name = (await profileName.boundingBox())!
+    expect(name.x).toBeGreaterThanOrEqual(image.x + image.width + 6)
+    expect(Math.abs(name.y + name.height / 2 - image.y - image.height / 2)).toBeLessThan(2)
+    expect(name.y + name.height).toBeLessThan(reply.y)
+    expect(Math.abs(reply.x - image.x)).toBeLessThan(1)
+    expect(reply.x + reply.width).toBeLessThanOrEqual(width)
+    expect(await message.evaluate(element => element.scrollWidth <= element.clientWidth + 1)).toBe(true)
+    if (width === 1440) await message.screenshot({ path: testInfo.outputPath('assistant-below-avatar.png'), animations: 'disabled' })
+  }
+})