diff --git a/src/agentkit/server/frontend/src/components/chat/ChatInput.vue b/src/agentkit/server/frontend/src/components/chat/ChatInput.vue
index a84d260..9e6698a 100644
--- a/src/agentkit/server/frontend/src/components/chat/ChatInput.vue
+++ b/src/agentkit/server/frontend/src/components/chat/ChatInput.vue
@@ -70,9 +70,10 @@
           专家团
         </a-button>
         <a-button
+          ref="boardButtonRef"
           size="small"
           :disabled="disabled"
-          @click="showBoardModal = true"
+          @click="handleBoardClick"
           class="chat-input__action-btn chat-input__action-btn--board"
         >
           <template #icon><TeamOutlined /></template>
@@ -125,6 +126,16 @@
         <span class="chat-input__hint">Enter 发送，Shift + Enter 换行</span>
       </div>
     </div>
+    <a-modal
+      v-model:open="showBoardBlockModal"
+      title="当前会话已存在私董会"
+      ok-text="新建会话"
+      cancel-text="我知道了"
+      @ok="handleCreateNewConversationForBoard"
+      @cancel="handleBoardBlockCancel"
+    >
+      <p>请新建会话来创建新的私董会</p>
+    </a-modal>
     <BoardMeetingModal
       v-model:open="showBoardModal"
       @submit="handleBoardSubmit"
@@ -137,8 +148,8 @@
 </template>
 
 <script setup lang="ts">
-import { ref, computed, watch, onMounted, onUnmounted, type Component } from 'vue'
-import { Input as AInput, Button as AButton, Select as ASelect } from 'ant-design-vue'
+import { ref, computed, watch, onMounted, onUnmounted, nextTick, type Component } from 'vue'
+import { Input as AInput, Button as AButton, Select as ASelect, Modal as AModal } from 'ant-design-vue'
 import { SendOutlined, TeamOutlined, UsergroupAddOutlined, PaperClipOutlined, PoweroffOutlined, CommentOutlined } from '@ant-design/icons-vue'
 import ContextPill from './ContextPill.vue'
 import MentionDropdown from './MentionDropdown.vue'
@@ -198,6 +209,8 @@ const availableModels = ref<ModelInfo[]>([])
 const modelsLoading = ref(false)
 const showBoardModal = ref(false)
 const showTeamModal = ref(false)
+const showBoardBlockModal = ref(false)
+const boardButtonRef = ref<InstanceType<typeof AButton> | null>(null)
 const fileInputRef = ref<HTMLInputElement | null>(null)
 const fileUploading = ref(false)
 const isDragOver = ref(false)
@@ -329,6 +342,32 @@ function handleStop(): void {
   emit('stop')
 }
 
+function handleBoardClick(): void {
+  // U1: 拦截"当前会话已存在进行中的私董会"场景
+  const status = chatStore.boardState?.status
+  if (status === 'discussing' || status === 'concluding') {
+    showBoardBlockModal.value = true
+    return
+  }
+  showBoardModal.value = true
+}
+
+async function handleCreateNewConversationForBoard(): Promise<void> {
+  showBoardBlockModal.value = false
+  chatStore.createConversation()
+  await chatStore.selectConversation(chatStore.currentConversationId!, true)
+  // 不自动打开 BoardMeetingModal，由用户在新会话中再次点击"私董会"按钮继续
+}
+
+function handleBoardBlockCancel(): void {
+  // R4-D3: 焦点恢复 — a-modal 关闭后将焦点返回触发按钮（WAI-ARIA modal 对话模式）
+  showBoardBlockModal.value = false
+  nextTick(() => {
+    const el = boardButtonRef.value?.$el as HTMLElement | undefined
+    el?.focus()
+  })
+}
+
 function handleBoardSubmit(command: string): void {
   // The BoardMeetingModal constructs an @board:expert1,expert2 topic command.
   // Send it through the normal chat pipeline — the backend intercepts @board prefix.
diff --git a/src/agentkit/server/frontend/src/components/chat/ChatMessage.vue b/src/agentkit/server/frontend/src/components/chat/ChatMessage.vue
index d18a068..8d593bd 100644
--- a/src/agentkit/server/frontend/src/components/chat/ChatMessage.vue
+++ b/src/agentkit/server/frontend/src/components/chat/ChatMessage.vue
@@ -6,8 +6,9 @@
     :avatar="spec.shell.avatar"
     :color="spec.shell.color"
     :expert-name="message.expert_name"
-    :expert-color="message.expert_color"
     :streaming="message.status === 'streaming'"
+    :message-type="spec.type"
+    :is-empty="isBubbleEmpty"
   >
     <component
       :is="spec.component"
@@ -21,6 +22,7 @@
 import MessageShell from './messages/MessageShell.vue'
 import { computed } from 'vue'
 import { useMessageRenderer } from './helpers/useMessageRenderer'
+import { isAssistantBubbleEmpty } from './helpers/bubbleUtils'
 import { useChatStore } from '@/stores/chatStore'
 import type { IChatMessage } from '@/api/types'
 
@@ -41,6 +43,12 @@ const componentListeners = computed(() =>
   spec.value.type === 'error' ? { retry: handleRetry } : {}
 )
 
+/**
+ * U3 G1: 检测消息内容是否为空 (pre-stream / tool-call-only)。
+ * 逻辑提取到 bubbleUtils.isAssistantBubbleEmpty 以支持单元测试。
+ */
+const isBubbleEmpty = computed(() => isAssistantBubbleEmpty(props.message))
+
 function handleRetry(): void {
   if (chatStore.isLoading) return
   chatStore.resendLastUserMessage()
diff --git a/src/agentkit/server/frontend/src/components/chat/helpers/bubbleUtils.ts b/src/agentkit/server/frontend/src/components/chat/helpers/bubbleUtils.ts
new file mode 100644
index 0000000..cf10356
--- /dev/null
+++ b/src/agentkit/server/frontend/src/components/chat/helpers/bubbleUtils.ts
@@ -0,0 +1,57 @@
+import type { IChatMessage } from '@/api/types'
+
+/**
+ * F4-A (Round 4 扩展): card-bearing assistant 类型排除气泡。
+ * 这些类型由各自 card 组件自带 chrome (ErrorCard full chrome + 其余 partial chrome)。
+ * 注: debate_started 对应 DebateBannerCard (plan 文档误记为 debate_banner)。
+ * ce-code-review P2: 加入 'error' — ErrorCard.vue 自带 full chrome，
+ *   不排除会导致 assistant 气泡嵌套 ErrorCard chrome 双层背景。
+ *
+ * 提取为纯函数以支持单元测试 (F4-A 是关键决策)，避免 leaky abstraction
+ * (ce-simplify-code P3) — MessageShell 通过函数调用而非暴露 Set。
+ */
+const CARD_BEARING_TYPES = new Set<string>([
+  'board_conclusion',
+  'team_plan',
+  'debate_started',
+  'debate_argument',
+  'debate_summary',
+  'debate_resolved',
+  'collaboration_graph',
+  'review_result',
+  'risk_flagged',
+  'error',
+])
+
+export function isCardBearingType(type?: string): boolean {
+  return type ? CARD_BEARING_TYPES.has(type) : false
+}
+
+/**
+ * U3 G1: 检测 assistant 消息内容是否为空 (pre-stream / tool-call-only)。
+ * AssistantText 总渲染根 div，:empty 选择器永不匹配，需 JS 判断。
+ * isEmpty = 无 content + 无 thinking + 无 tool_calls。
+ *
+ * 提取为纯函数以支持单元测试 (G1 是 P0 决策)。
+ */
+export function isAssistantBubbleEmpty(message: IChatMessage): boolean {
+  if (message.role !== 'assistant') return false
+  return (
+    !message.content &&
+    !message.thinking &&
+    (!message.tool_calls || message.tool_calls.length === 0)
+  )
+}
+
+/**
+ * U4: 判定用户消息是否为普通文本 (非文件附件且非 @board/@team 命令)。
+ * 仅普通文本应用深色气泡，command card / file attachment 保持浅色背景。
+ *
+ * 提取为纯函数以支持单元测试 (U4 是关键功能)。
+ */
+const FILE_MARKDOWN_RE = /^\[文件\]\s*\[(.+?)\]\((.+?)\)$/s
+const COMMAND_RE = /^@(board|team)(?::([^\s]+))?\s+([\s\S]+)$/
+
+export function isPlainUserText(content: string): boolean {
+  return !FILE_MARKDOWN_RE.test(content) && !COMMAND_RE.test(content)
+}
diff --git a/src/agentkit/server/frontend/src/components/chat/helpers/useMessageRenderer.ts b/src/agentkit/server/frontend/src/components/chat/helpers/useMessageRenderer.ts
index d094f61..8efb706 100644
--- a/src/agentkit/server/frontend/src/components/chat/helpers/useMessageRenderer.ts
+++ b/src/agentkit/server/frontend/src/components/chat/helpers/useMessageRenderer.ts
@@ -135,14 +135,12 @@ export function useMessageRenderer(message: IChatMessage) {
 
       case 'board_banner': {
         const data = message.board_started
-        const experts = data?.experts ?? []
         return {
           type,
           shell: { name: '私董会', meta: time },
           component: BoardBannerCard,
           props: {
             topic: data?.topic || message.content || '未命名主题',
-            experts,
             maxRounds: data?.max_rounds ?? 5,
             currentRound: message.board_round ?? 1,
           },
diff --git a/src/agentkit/server/frontend/src/components/chat/messages/BoardBannerCard.vue b/src/agentkit/server/frontend/src/components/chat/messages/BoardBannerCard.vue
index 59ffb2e..93dec02 100644
--- a/src/agentkit/server/frontend/src/components/chat/messages/BoardBannerCard.vue
+++ b/src/agentkit/server/frontend/src/components/chat/messages/BoardBannerCard.vue
@@ -1,138 +1,37 @@
 <template>
   <div class="board-banner-card">
-    <div class="board-banner-card__bar" />
-    <div class="board-banner-card__body">
-      <div class="board-banner-card__title">
-        <BankOutlined class="board-banner-card__icon" />
-        <span>私董会 — {{ topic }}</span>
-      </div>
-      <div class="board-banner-card__experts">
-        <span
-          v-for="(expert, idx) in experts"
-          :key="`${expert.name}-${idx}`"
-          class="board-banner-card__chip"
-          :class="{ 'board-banner-card__chip--moderator': expert.is_moderator }"
-        >
-          <span class="board-banner-card__chip-avatar">{{ expert.avatar }}</span>
-          <span>{{ expert.name }}</span>
-        </span>
-      </div>
-      <div class="board-banner-card__meta">
-        <span>轮次：第 {{ currentRound }} / {{ maxRounds }} 轮</span>
-        <div class="board-banner-card__progress">
-          <div
-            class="board-banner-card__progress-fill"
-            :style="{ width: progressPercent + '%' }"
-          />
-        </div>
-      </div>
-    </div>
+    <div class="board-banner-card__title">私董会 — {{ topic }}</div>
+    <div class="board-banner-card__meta">轮次：第 {{ currentRound }} / {{ maxRounds }} 轮</div>
   </div>
 </template>
 
 <script setup lang="ts">
-import { computed } from 'vue'
-import { BankOutlined } from '@ant-design/icons-vue'
-import type { IBoardExpert } from '@/api/types'
-
 interface Props {
   topic: string
-  experts: IBoardExpert[]
   maxRounds: number
   currentRound?: number
 }
 
-const props = withDefaults(defineProps<Props>(), {
+withDefaults(defineProps<Props>(), {
   currentRound: 1,
 })
-
-const progressPercent = computed(() => {
-  if (props.maxRounds <= 0) return 0
-  return Math.min((props.currentRound / props.maxRounds) * 100, 100)
-})
 </script>
 
 <style scoped>
 .board-banner-card {
-  width: 100%;
-  background: var(--bg-primary);
-  border: 1px solid var(--border-color);
-  border-radius: var(--radius-card);
-  box-shadow: var(--shadow-card);
-  overflow: hidden;
-}
-
-.board-banner-card__bar {
-  height: 4px;
-  background: var(--accent-board);
-}
-
-.board-banner-card__body {
-  padding: var(--space-3) var(--space-4);
-  display: flex;
-  flex-direction: column;
-  gap: var(--space-3);
+  margin-bottom: var(--space-3);
+  padding: var(--space-2) 0;
 }
 
 .board-banner-card__title {
-  display: flex;
-  align-items: center;
-  gap: var(--space-2);
   font-size: var(--font-md);
   font-weight: var(--font-weight-semibold);
   color: var(--text-primary);
-}
-
-.board-banner-card__icon {
-  font-size: var(--font-lg);
-}
-
-.board-banner-card__experts {
-  display: flex;
-  flex-wrap: wrap;
-  gap: var(--space-2);
-}
-
-.board-banner-card__chip {
-  display: inline-flex;
-  align-items: center;
-  gap: 4px;
-  padding: 2px 8px;
-  background: var(--accent-board-soft);
-  color: var(--accent-board);
-  border-radius: var(--radius-full);
-  font-size: var(--font-xs);
-}
-
-.board-banner-card__chip--moderator {
-  background: var(--accent-board);
-  color: var(--text-inverse);
-}
-
-.board-banner-card__chip-avatar {
-  font-size: 12px;
+  margin-bottom: var(--space-1);
 }
 
 .board-banner-card__meta {
-  display: flex;
-  align-items: center;
-  gap: var(--space-3);
   font-size: var(--font-xs);
   color: var(--text-tertiary);
 }
-
-.board-banner-card__progress {
-  flex: 1;
-  height: 4px;
-  background: var(--bg-tertiary);
-  border-radius: 2px;
-  overflow: hidden;
-}
-
-.board-banner-card__progress-fill {
-  height: 100%;
-  background: var(--accent-board);
-  border-radius: 2px;
-  transition: width 0.3s ease;
-}
 </style>
diff --git a/src/agentkit/server/frontend/src/components/chat/messages/MessageShell.vue b/src/agentkit/server/frontend/src/components/chat/messages/MessageShell.vue
index 0a692a4..29cd728 100644
--- a/src/agentkit/server/frontend/src/components/chat/messages/MessageShell.vue
+++ b/src/agentkit/server/frontend/src/components/chat/messages/MessageShell.vue
@@ -1,5 +1,11 @@
 <template>
-  <div class="message-shell" :class="[`message-shell--${role}`]">
+  <div
+    class="message-shell"
+    :class="[
+      `message-shell--${role}`,
+      { 'message-shell--card': isCardBearing, 'message-shell--empty': isEmpty },
+    ]"
+  >
     <div class="message-shell__avatar">
       <slot name="avatar">
         <div
@@ -42,9 +48,11 @@
 </template>
 
 <script setup lang="ts">
+import { computed } from 'vue'
 import { Avatar as AAvatar } from 'ant-design-vue'
 import { RobotOutlined, UserOutlined } from '@ant-design/icons-vue'
 import type { Component } from 'vue'
+import { isCardBearingType } from '../helpers/bubbleUtils'
 
 interface Props {
   role: 'user' | 'assistant'
@@ -52,23 +60,28 @@ interface Props {
   meta?: string
   avatar?: string | Component
   color?: string
-  /** U4 R10: 专家身份 badge 名称 — 存在时渲染为彩色 badge 替代普通 name 文本 */
+  /** U4 R10: 专家身份 badge 名称 — 存在时渲染为粗体文本替代普通 name */
   expertName?: string
-  /** U4 R10: 专家身份 badge 颜色 */
-  expertColor?: string
   /** U4: 流式进行中 — 显示省略号指示器 */
   streaming?: boolean
+  /** U3 F4-A: 消息类型 — card-bearing 类型不加气泡 (由 card 自带 chrome) */
+  messageType?: string
+  /** U3 G1: 消息内容为空 (pre-stream / tool-call-only) — 隐藏空气泡矩形 */
+  isEmpty?: boolean
 }
 
-withDefaults(defineProps<Props>(), {
+const props = withDefaults(defineProps<Props>(), {
   name: undefined,
   meta: undefined,
   avatar: undefined,
   color: undefined,
   expertName: undefined,
-  expertColor: undefined,
   streaming: false,
+  messageType: undefined,
+  isEmpty: false,
 })
+
+const isCardBearing = computed(() => isCardBearingType(props.messageType))
 </script>
 
 <style scoped>
@@ -186,4 +199,33 @@ withDefaults(defineProps<Props>(), {
 .message-shell--user .message-shell__content {
   align-items: flex-end;
 }
+
+/* U3: assistant 浅灰圆角气泡 (方案B) — 仅 role=assistant 生效，user 不加气泡。
+   F1-A: 用独立 token --bg-message-bubble (与 inline code/table 的 --bg-secondary 解耦)。
+   不使用 !important，让 AssistantText 内部 pre/hljs/code/table 自然继承。 */
+.message-shell--assistant .message-shell__content {
+  background: var(--bg-message-bubble);
+  border: 1px solid var(--border-color);
+  border-radius: var(--radius-md);
+  padding: var(--space-3) var(--space-4);
+  color: var(--text-primary);
+}
+
+/* F4-A: card-bearing assistant 类型不加气泡 (共 9 种，Round 4 扩展)。
+   这些类型由各自 card 组件自带 chrome (BoardConclusionCard/TeamPlanCard full chrome，
+   其余 7 种 partial chrome)，避免气泡嵌套冲突。 */
+.message-shell--assistant.message-shell--card .message-shell__content {
+  background: transparent;
+  border: none;
+  border-radius: 0;
+  padding: 0;
+}
+
+/* G1: 空内容 (pre-stream / tool-call-only) 隐藏气泡矩形，仅显示 thinking dots。
+   替代 Round 1 D4-方案1 的 :empty (AssistantText 总渲染根 div 导致 :empty 永不匹配)。 */
+.message-shell--assistant.message-shell--empty .message-shell__content {
+  background: transparent;
+  border: none;
+  padding: 0;
+}
 </style>
diff --git a/src/agentkit/server/frontend/src/components/chat/messages/UserBubble.vue b/src/agentkit/server/frontend/src/components/chat/messages/UserBubble.vue
index d8a1908..f6e8649 100644
--- a/src/agentkit/server/frontend/src/components/chat/messages/UserBubble.vue
+++ b/src/agentkit/server/frontend/src/components/chat/messages/UserBubble.vue
@@ -2,7 +2,10 @@
   <div
     ref="rootRef"
     class="user-bubble"
-    :class="{ 'user-bubble--focusable': msgId }"
+    :class="{
+      'user-bubble--focusable': msgId,
+      'user-bubble--text': isPlainText,
+    }"
     :tabindex="msgId ? 0 : undefined"
     @mouseenter="onBubbleMouseEnter"
     @mouseleave="onBubbleMouseLeave"
@@ -157,6 +160,14 @@ const fileAttachment = computed(() => {
   }
 })
 
+/**
+ * U4: 普通文本消息判定 — 非 file attachment 且非 @board/@team command card。
+ * 仅普通文本应用深色气泡，command card / file attachment 保持浅色 --bg-tertiary。
+ * 核心正则逻辑提取到 bubbleUtils.isPlainUserText 以支持单元测试；
+ * 此处保留对 fileAttachment/commandBubble computed 的引用以维持响应性。
+ */
+const isPlainText = computed(() => !fileAttachment.value && !commandBubble.value)
+
 // --- Action toolbar visibility ---
 // Three independent reasons the toolbar can stay open; the toolbar shows
 // while ANY is active. This avoids the classic hover-toolbar bug where
@@ -301,10 +312,20 @@ onUnmounted(() => {
 }
 
 .user-bubble--focusable:focus-visible {
-  outline: 2px solid var(--accent-primary, #1a1a1a);
+  outline: 2px solid var(--color-primary, #1a1a1a);
   outline-offset: 2px;
 }
 
+/* U4: 普通文本消息参考 demo 深色气泡 (--color-primary + --text-inverse)。
+   command card / file attachment 保持 .user-bubble 默认 --bg-tertiary 浅色背景。
+   --color-primary / --text-inverse 在 light/dark mode 下自动反转。 */
+.user-bubble--text {
+  background: var(--color-primary);
+  color: var(--text-inverse);
+  padding: var(--space-3) var(--space-4);
+  max-width: 70%;
+}
+
 .user-bubble__text {
   white-space: pre-wrap;
 }
diff --git a/src/agentkit/server/frontend/src/components/preview/scenes/Scene4BoardDiscussion.vue b/src/agentkit/server/frontend/src/components/preview/scenes/Scene4BoardDiscussion.vue
index 04337dd..d5d9346 100644
--- a/src/agentkit/server/frontend/src/components/preview/scenes/Scene4BoardDiscussion.vue
+++ b/src/agentkit/server/frontend/src/components/preview/scenes/Scene4BoardDiscussion.vue
@@ -8,7 +8,6 @@
       <MessageShell role="assistant" name="私董会" meta="11:00">
         <BoardBannerCard
           topic="是否将订单服务拆分为独立微服务"
-          :experts="boardExperts"
           :max-rounds="3"
           :current-round="1"
         />
@@ -41,13 +40,7 @@ import {
   BoardRoundCard,
   BoardConclusionCard,
 } from '@/components/chat/messages'
-import type { IChatMessage, IBoardConcludedData, IBoardExpert } from '@/api/types'
-
-const boardExperts: IBoardExpert[] = [
-  { name: '架构师老张', avatar: '张', color: 'var(--accent-board)', is_moderator: false, persona: '架构' },
-  { name: '后端负责人小李', avatar: '李', color: 'var(--accent-board)', is_moderator: false, persona: '后端' },
-  { name: '主持人', avatar: '主', color: 'var(--accent-board)', is_moderator: true, persona: '主持' },
-]
+import type { IChatMessage, IBoardConcludedData } from '@/api/types'
 
 const speech1: IChatMessage = {
   id: 's4-speech-1',
diff --git a/src/agentkit/server/frontend/src/styles/tokens.css b/src/agentkit/server/frontend/src/styles/tokens.css
index 2f56572..fa7956d 100644
--- a/src/agentkit/server/frontend/src/styles/tokens.css
+++ b/src/agentkit/server/frontend/src/styles/tokens.css
@@ -66,6 +66,8 @@
   --bg-tertiary: #f7f7f5;
   --bg-elevated: #ffffff;
   --bg-code: #1e1e2e;
+  /* 消息气泡背景，与 inline code/table 背景解耦 (F1-A) */
+  --bg-message-bubble: #ffffff;
 
   /* ── Foreground / Text ── */
   --text-primary: #1a1a1a;
@@ -224,6 +226,8 @@
   --bg-tertiary: #2a2a2a;
   --bg-elevated: #252525;
   --bg-code: #11111b;
+  /* 消息气泡背景，与 inline code/table 背景解耦 (F1-A) */
+  --bg-message-bubble: #1f1f1f;
 
   /* ── Foreground / Text ── */
   --text-primary: #fbfbfa;
diff --git a/src/agentkit/server/frontend/tests/unit/components/BoardBannerCard.test.ts b/src/agentkit/server/frontend/tests/unit/components/BoardBannerCard.test.ts
new file mode 100644
index 0000000..c751aa8
--- /dev/null
+++ b/src/agentkit/server/frontend/tests/unit/components/BoardBannerCard.test.ts
@@ -0,0 +1,87 @@
+/**
+ * Unit tests for BoardBannerCard (U2 — simplified banner).
+ *
+ * Covers the P1 testing gap flagged by ce-code-review. Verifies:
+ * - Renders "私董会 — {topic}" title
+ * - Renders "轮次：第 N / M 轮" meta
+ * - currentRound defaults to 1 when not provided
+ * - Custom currentRound renders correctly
+ * - No icons, borders, purple bars, progress bars, or expert chips (U2 simplification)
+ *
+ * Mount strategy: native Vue createApp + h (no @vue/test-utils dependency),
+ * consistent with AssistantText.test.ts / ThinkingBlock.test.ts pattern.
+ */
+
+import { afterEach, describe, expect, it } from 'vitest'
+import { createApp, h, type App } from 'vue'
+import BoardBannerCard from '@/components/chat/messages/BoardBannerCard.vue'
+
+interface Mounted {
+  container: HTMLElement
+  root: HTMLElement
+  app: App
+  unmount: () => void
+}
+
+function mountBoardBannerCard(props: Record<string, unknown>): Mounted {
+  const container = document.createElement('div')
+  document.body.appendChild(container)
+  const app = createApp({
+    render: () => h(BoardBannerCard as never, props as never),
+  })
+  app.mount(container)
+  const root = container.querySelector('.board-banner-card') as HTMLElement
+  return { container, root, app, unmount: () => { app.unmount(); container.remove() } }
+}
+
+describe('BoardBannerCard — U2 simplified banner', () => {
+  let mounted: Mounted | null = null
+
+  afterEach(() => {
+    mounted?.unmount()
+    mounted = null
+  })
+
+  it('renders "私董会 — {topic}" as title', () => {
+    mounted = mountBoardBannerCard({ topic: '技术选型讨论', maxRounds: 5 })
+    const title = mounted.container.querySelector('.board-banner-card__title') as HTMLElement
+    expect(title).toBeTruthy()
+    expect(title.textContent).toBe('私董会 — 技术选型讨论')
+  })
+
+  it('renders "轮次：第 N / M 轮" as meta', () => {
+    mounted = mountBoardBannerCard({ topic: '架构评审', maxRounds: 3, currentRound: 2 })
+    const meta = mounted.container.querySelector('.board-banner-card__meta') as HTMLElement
+    expect(meta).toBeTruthy()
+    expect(meta.textContent).toBe('轮次：第 2 / 3 轮')
+  })
+
+  it('defaults currentRound to 1 when not provided', () => {
+    mounted = mountBoardBannerCard({ topic: '新产品方向', maxRounds: 5 })
+    const meta = mounted.container.querySelector('.board-banner-card__meta') as HTMLElement
+    expect(meta.textContent).toBe('轮次：第 1 / 5 轮')
+  })
+
+  it('renders only title and meta — no icons, bars, progress, or expert chips', () => {
+    mounted = mountBoardBannerCard({ topic: '精简测试', maxRounds: 4, currentRound: 2 })
+    // Only two child elements: __title and __meta
+    const children = mounted.root.children
+    expect(children.length).toBe(2)
+    expect(children[0].className).toBe('board-banner-card__title')
+    expect(children[1].className).toBe('board-banner-card__meta')
+    // No icon elements, progress bars, or expert chips
+    expect(mounted.root.querySelector('svg, .anticon, .board-banner-card__bar, .board-banner-card__progress, .board-banner-card__experts, .board-banner-card__chip')).toBeNull()
+  })
+
+  it('handles CJK topic correctly', () => {
+    mounted = mountBoardBannerCard({ topic: '人工智能伦理边界探讨', maxRounds: 6 })
+    const title = mounted.container.querySelector('.board-banner-card__title') as HTMLElement
+    expect(title.textContent).toBe('私董会 — 人工智能伦理边界探讨')
+  })
+
+  it('handles empty topic gracefully', () => {
+    mounted = mountBoardBannerCard({ topic: '', maxRounds: 5 })
+    const title = mounted.container.querySelector('.board-banner-card__title') as HTMLElement
+    expect(title.textContent).toBe('私董会 — ')
+  })
+})
diff --git a/src/agentkit/server/frontend/tests/unit/helpers/bubbleUtils.test.ts b/src/agentkit/server/frontend/tests/unit/helpers/bubbleUtils.test.ts
new file mode 100644
index 0000000..a3030cf
--- /dev/null
+++ b/src/agentkit/server/frontend/tests/unit/helpers/bubbleUtils.test.ts
@@ -0,0 +1,180 @@
+/**
+ * Unit tests for bubbleUtils — pure functions extracted from MessageShell /
+ * ChatMessage / UserBubble to support testing of key decisions:
+ *
+ *   - isCardBearingType (F4-A): card-bearing assistant types skip bubble chrome
+ *   - isAssistantBubbleEmpty (G1): empty content detection replaces :empty selector
+ *   - isPlainUserText (U4): plain text vs file-attachment / @board/@team command
+ *
+ * These cover the P0/P1 testing gaps flagged by ce-code-review: G1 is a P0
+ * decision (:empty never matches), F4-A is a P0 regression guard (double
+ * bubble), U4 is a P0 feature (dark bubble only for plain text).
+ */
+
+import { describe, expect, it } from 'vitest'
+import {
+  isCardBearingType,
+  isAssistantBubbleEmpty,
+  isPlainUserText,
+} from '@/components/chat/helpers/bubbleUtils'
+import type { IChatMessage } from '@/api/types'
+
+function makeMsg(overrides: Partial<IChatMessage> = {}): IChatMessage {
+  return {
+    id: 'm1',
+    role: 'assistant',
+    content: '',
+    timestamp: '2026-07-01T00:00:00Z',
+    ...overrides,
+  }
+}
+
+// ── isCardBearingType (F4-A) ────────────────────────────────────────
+
+describe('isCardBearingType — F4-A card-bearing exclusion', () => {
+  const cardBearingTypes = [
+    'board_conclusion',
+    'team_plan',
+    'debate_started',
+    'debate_argument',
+    'debate_summary',
+    'debate_resolved',
+    'collaboration_graph',
+    'review_result',
+    'risk_flagged',
+    'error',
+  ]
+
+  it.each(cardBearingTypes)('returns true for card-bearing type "%s"', (type) => {
+    expect(isCardBearingType(type)).toBe(true)
+  })
+
+  it('returns false for plain assistant type', () => {
+    expect(isCardBearingType('assistant')).toBe(false)
+  })
+
+  it('returns false for user type', () => {
+    expect(isCardBearingType('user')).toBe(false)
+  })
+
+  it('returns false for milestone type (not card-bearing)', () => {
+    expect(isCardBearingType('milestone')).toBe(false)
+  })
+
+  it('returns false for board_banner / board_speech / board_summary (partial chrome, no own bubble chrome)', () => {
+    // These use BoardRoundCard which relies on the assistant bubble chrome,
+    // so they must NOT be excluded.
+    expect(isCardBearingType('board_banner')).toBe(false)
+    expect(isCardBearingType('board_speech')).toBe(false)
+    expect(isCardBearingType('board_summary')).toBe(false)
+  })
+
+  it('returns false for undefined type', () => {
+    expect(isCardBearingType(undefined)).toBe(false)
+  })
+
+  it('returns false for empty string', () => {
+    expect(isCardBearingType('')).toBe(false)
+  })
+
+  it('returns false for unknown type', () => {
+    expect(isCardBearingType('unknown_type')).toBe(false)
+  })
+})
+
+// ── isAssistantBubbleEmpty (G1) ─────────────────────────────────────
+
+describe('isAssistantBubbleEmpty — G1 empty content detection', () => {
+  it('returns true for assistant with no content, no thinking, no tool_calls', () => {
+    const msg = makeMsg({ role: 'assistant', content: '' })
+    expect(isAssistantBubbleEmpty(msg)).toBe(true)
+  })
+
+  it('returns true for assistant with undefined content and thinking', () => {
+    const msg = makeMsg({ role: 'assistant', content: undefined, thinking: undefined })
+    expect(isAssistantBubbleEmpty(msg)).toBe(true)
+  })
+
+  it('returns true for assistant with empty tool_calls array', () => {
+    const msg = makeMsg({ role: 'assistant', content: '', tool_calls: [] })
+    expect(isAssistantBubbleEmpty(msg)).toBe(true)
+  })
+
+  it('returns false for assistant with content', () => {
+    const msg = makeMsg({ role: 'assistant', content: 'hello' })
+    expect(isAssistantBubbleEmpty(msg)).toBe(false)
+  })
+
+  it('returns false for assistant with thinking content', () => {
+    const msg = makeMsg({ role: 'assistant', content: '', thinking: '思考中' })
+    expect(isAssistantBubbleEmpty(msg)).toBe(false)
+  })
+
+  it('returns false for assistant with non-empty tool_calls', () => {
+    const msg = makeMsg({
+      role: 'assistant',
+      content: '',
+      tool_calls: [{ id: 't1', name: 'search', arguments: '{}' } as never],
+    })
+    expect(isAssistantBubbleEmpty(msg)).toBe(false)
+  })
+
+  it('returns false for user role even when content is empty', () => {
+    const msg = makeMsg({ role: 'user', content: '' })
+    expect(isAssistantBubbleEmpty(msg)).toBe(false)
+  })
+
+  it('returns false for user role with content', () => {
+    const msg = makeMsg({ role: 'user', content: 'hi' })
+    expect(isAssistantBubbleEmpty(msg)).toBe(false)
+  })
+})
+
+// ── isPlainUserText (U4) ────────────────────────────────────────────
+
+describe('isPlainUserText — U4 plain text detection', () => {
+  it('returns true for plain text', () => {
+    expect(isPlainUserText('你好，帮我重构这个函数')).toBe(true)
+  })
+
+  it('returns true for empty string (no command, no file)', () => {
+    expect(isPlainUserText('')).toBe(true)
+  })
+
+  it('returns true for text with @ mention that is not board/team', () => {
+    expect(isPlainUserText('@user hello')).toBe(true)
+  })
+
+  it('returns false for @board command', () => {
+    expect(isPlainUserText('@board 讨论技术选型')).toBe(false)
+  })
+
+  it('returns false for @team command', () => {
+    expect(isPlainUserText('@team 完成需求分析')).toBe(false)
+  })
+
+  it('returns false for @board with expert list', () => {
+    expect(isPlainUserText('@board:expert1,expert2 讨论架构')).toBe(false)
+  })
+
+  it('returns false for @team with template', () => {
+    expect(isPlainUserText('@team:dev_team 实现登录功能')).toBe(false)
+  })
+
+  it('returns false for @board with rounds param', () => {
+    expect(isPlainUserText('@board rounds=3 讨论方案')).toBe(false)
+  })
+
+  it('returns false for file attachment markdown', () => {
+    expect(isPlainUserText('[文件] [report.pdf](https://example.com/report.pdf)')).toBe(false)
+  })
+
+  it('returns true for text containing @board in the middle (not a prefix)', () => {
+    // Only prefix @board/@team commands are recognized; mid-text @ is plain.
+    expect(isPlainUserText('请帮我 @board 这个问题')).toBe(true)
+  })
+
+  it('returns true for multiline plain text', () => {
+    expect(isPlainUserText('第一行\n第二行\n第三行')).toBe(true)
+  })
+})
diff --git a/src/agentkit/server/static/index.html b/src/agentkit/server/static/index.html
index 54441be..c9a7f66 100644
--- a/src/agentkit/server/static/index.html
+++ b/src/agentkit/server/static/index.html
@@ -5,8 +5,8 @@
     <link rel="icon" type="image/svg+xml" href="/vite.svg" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Fischer AgentKit</title>
-    <script type="module" crossorigin src="/assets/index-CHN0ThS0.js"></script>
-    <link rel="stylesheet" crossorigin href="/assets/index-DC_0XUg6.css">
+    <script type="module" crossorigin src="/assets/index-N9Dybwcy.js"></script>
+    <link rel="stylesheet" crossorigin href="/assets/index-BgFZbme0.css">
   </head>
   <body>
     <div id="app"></div>