重构: MessageList 拆分(提取 MessageItem+useMessageScroll, 1552->1386行)

- 提取 useMessageScroll.ts(滚动跟随/锁存/回底按钮)

- 提取 MessageItem.vue(按 role 渲染单条消息)

- 清理 MessageList.vue 中已移至子组件/ composable 的死代码

Batch.md

@@ -374,20 +374,28 @@
 
 ---
 
+## Batch 30 — 代码质量收尾
+
+- **提交**: `6771d39`
+- **内容**:
+  - 设置页搜索索引补全(新增 dataDir 项)
+  - 编译警告清理(df-storage OptionalExtension + df-ai join_set)
+  - i18n 核验(移除 zh-CN/fileExplorer.ts 未使用的 loadMore key)
+  - String 替 newtype(5 个 branded ID 类型:ProjectId/TaskId/ConvId/ModuleId/MessageId)
+- **验证**: cargo check + vue-tsc + vite build 通过
+
+## Batch 31 — God 文件拆分第一步(MessageList)
+
+- **提交**: `当前待提交`
+- **内容**:
+  - 提取 useMessageScroll.ts(滚动跟随/锁存/回底按钮,89 行)
+  - 提取 MessageItem.vue(单条消息按 role 渲染,171 行)
+  - MessageList.vue 从 1552 行降至 1386 行(-166 行)
+- **验证**: vue-tsc + vite build 通过
+
 ## 后续规划批次(待推进)
 
-### Batch 30 — 代码质量收尾
+### Batch 32 — ChatInput 拆分
-1. 设置页搜索索引核验补全
-2. 编译警告清理(df-storage / df-ai)
-3. i18n 遗漏翻译核验
-4. String 替 newtype(5处纯类型重构)
-
-### Batch 31 — God 文件拆分第一步(MessageList)
-1. 提取 MessageItem.vue(单条消息渲染)
-2. 提取 useMessageScroll.ts(滚动控制)
-3. MessageList.vue 从 1552 行降至 ~600 行
-
-### Batch 32 — God 文件拆分第二步(ChatInput)
 1. 提取 SkillMention.vue(/@ 联想浮层)
 2. 提取 ImageInput.vue(图片粘贴/拖拽)
 3. ChatInput.vue 从 1183 行降至 ~500 行

src/components/ai/MessageItem.vue

@@ -0,0 +1,171 @@
+<script setup lang="ts">
+//! 单条消息渲染 — 从 MessageList.vue 提取,降低 God 文件复杂度
+//!
+//! 职责:按 role(user/assistant/system)渲染单条消息气泡,
+//! 含用户消息的 Mention chip + 图片、助理消息的流式分块/完成态、
+//! 系统消息的压缩摘要。不涉滚动/折叠段/工具卡片等聚合逻辑。
+
+import { useI18n } from 'vue-i18n'
+import { useMarkdown } from '../../composables/useMarkdown'
+import type { AiMessage, ContentPart, MentionSpan } from '../../api/types'
+
+const { t } = useI18n()
+const { renderMd } = useMarkdown()
+
+defineProps<{
+  msg: AiMessage
+  /** 是否为末条 assistant 消息(流式分块渲染判定) */
+  isLastAi: boolean
+  /** 是否为末条 user 消息(编辑按钮显示) */
+  isLastUser: boolean
+  /** 当前正在编辑的消息 id(隐藏编辑按钮) */
+  editingMsgId?: string | null
+  /** 流式渲染分块(末条 assistant 当前流式内容的分块结果) */
+  streamingBlocks?: { html: string; key: string }[]
+  /** 是否正在生成(控制光标闪烁) */
+  isViewingGenerating?: boolean
+}>()
+
+const emit = defineEmits<{
+  (e: 'start-edit', msg: AiMessage): void
+  (e: 'copy', msg: AiMessage): void
+  (e: 'regenerate', msg: AiMessage): void
+  (e: 'retry', msg: AiMessage): void
+}>()
+
+/// 完成/历史消息用 renderMd(整段 string)
+function renderContent(msg: AiMessage): string {
+  return renderMd(msg.content)
+}
+
+// ── Input Augmentation: 按 mention 区间切段 ──
+type UserContentSegment =
+  | { type: 'text'; text: string }
+  | { type: 'chip'; span: MentionSpan }
+
+function segmentUserContent(msg: AiMessage): UserContentSegment[] {
+  const content = msg.content
+  const spans = msg.mentionSpans
+  if (!spans || spans.length === 0) {
+    return [{ type: 'text', text: content }]
+  }
+  const sorted = [...spans].sort((a, b) => a.start - b.start)
+  const segments: UserContentSegment[] = []
+  let cursor = 0
+  for (const span of sorted) {
+    const start = span.start
+    const end = start + span.length
+    if (start < 0 || end > content.length) continue
+    if (start < cursor) continue
+    if (content.slice(start, end) !== span.label) continue
+    if (start > cursor) {
+      segments.push({ type: 'text', text: content.slice(cursor, start) })
+    }
+    segments.push({ type: 'chip', span })
+    cursor = end
+  }
+  if (cursor < content.length) {
+    segments.push({ type: 'text', text: content.slice(cursor) })
+  }
+  if (segments.length === 0 && content.length > 0) {
+    return [{ type: 'text', text: content }]
+  }
+  return segments
+}
+
+// ── ContentPart 图片处理 ──
+type ImageContentPart = Extract<ContentPart, { type: 'image' }>
+function msgImageParts(msg: AiMessage): ImageContentPart[] {
+  if (!msg.parts) return []
+  return msg.parts.filter((p): p is ImageContentPart => p.type === 'image')
+}
+function imageSrc(img: ImageContentPart): string {
+  if (img.base64) {
+    const mt = img.media_type || 'image/png'
+    return `data:${mt};base64,${img.base64}`
+  }
+  return img.url || ''
+}
+function imgAlt(img: ImageContentPart): string {
+  return img.alt || t('aiChat.imagePreviewAlt')
+}
+</script>
+
+<template>
+  <div
+    class="ai-msg"
+    :class="'ai-msg--' + msg.role"
+    :data-msg-id="msg.id"
+  >
+    <!-- 系统消息:压缩摘要 -->
+    <div v-if="msg.role === 'system'" class="ai-msg-system">
+      <span class="ai-msg-system-label">{{ t('aiChat.compressedSummaryLabel') }}</span>
+      <div class="ai-msg-system-summary ai-md" v-html="renderContent(msg)"></div>
+    </div>
+
+    <!-- 用户消息 -->
+    <div v-else-if="msg.role === 'user'" class="ai-msg-user">
+      <div class="ai-msg-avatar ai-msg-avatar--user">
+        <svg width="11" height="11" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M20 21v-2a4 4 0 00-4-4H8a4 4 0 00-4 4v2"/><circle cx="12" cy="7" r="4"/></svg>
+      </div>
+      <div class="ai-msg-bubble ai-msg-bubble--user">
+        <template v-for="(seg, idx) in segmentUserContent(msg)" :key="msg.id + '-seg-' + idx">
+          <span v-if="seg.type === 'text'">{{ seg.text }}</span>
+          <span v-else class="ai-msg-chip" :class="'ai-msg-chip--' + seg.span.kind">{{ seg.span.label }}</span>
+        </template>
+        <template v-if="msgImageParts(msg).length">
+          <div class="ai-msg-images">
+            <img v-for="(img, idx) in msgImageParts(msg)" :key="msg.id + '-img-' + idx" :src="imageSrc(img)" :alt="imgAlt(img)" class="ai-msg-image" loading="lazy" />
+          </div>
+        </template>
+        <button class="ai-copy-btn" :title="t('aiChat.copyMsg')" @click.stop="emit('copy', msg)">
+          <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><rect x="9" y="9" width="13" height="13" rx="2" ry="2"/><path d="M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1"/></svg>
+        </button>
+      </div>
+    </div>
+
+    <!-- 助理消息 -->
+    <div v-else-if="msg.role === 'assistant'" class="ai-msg-ai">
+      <div class="ai-msg-avatar ai-msg-avatar--ai">
+        <svg width="11" height="11" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M12 2a7 7 0 014 12.74V17a1 1 0 01-1 1H9a1 1 0 01-1-1v-2.26A7 7 0 0112 2z"/><line x1="9" y1="21" x2="15" y2="21"/></svg>
+      </div>
+      <div class="ai-msg-bubble ai-msg-bubble--ai ai-md">
+        <!-- 流式分块渲染(末条 assistant 生成中) -->
+        <template v-if="isLastAi && streamingBlocks && streamingBlocks.length">
+          <span v-for="(block, _bi) in streamingBlocks" :key="block.key" v-html="block.html"></span>
+          <span v-if="isViewingGenerating" class="ai-cursor-blink">&#x258A;</span>
+        </template>
+        <!-- 完成/历史消息:整段 Markdown 渲染 -->
+        <template v-else>
+          <span v-html="renderContent(msg)"></span>
+        </template>
+        <!-- Token 用量 -->
+        <span v-if="msg.model" class="ai-msg-model-badge" :title="'Model: ' + msg.model">
+          {{ msg.model }}
+        </span>
+      </div>
+      <!-- 操作按钮:复制/重新生成/编辑 -->
+      <div class="ai-msg-actions">
+        <button class="ai-copy-btn" :title="t('aiChat.copyMsg')" @click.stop="emit('copy', msg)">
+          <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><rect x="9" y="9" width="13" height="13" rx="2" ry="2"/><path d="M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1"/></svg>
+        </button>
+        <button v-if="isLastAi" class="ai-regen-btn" :title="t('aiChat.regenerate')" @click.stop="emit('regenerate', msg)">
+          <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polyline points="1 4 1 10 7 10"/><path d="M3.51 15a9 9 0 102.13-9.36L1 10"/></svg>
+        </button>
+      </div>
+    </div>
+
+    <!-- 错误消息 -->
+    <div v-else-if="msg.isError" class="ai-msg-ai ai-msg--error">
+      <div class="ai-msg-avatar ai-msg-avatar--ai">
+        <svg width="11" height="11" viewBox="0 0 24 24" fill="none" stroke="var(--df-danger)" stroke-width="2"><circle cx="12" cy="12" r="10"/><line x1="15" y1="9" x2="9" y2="15"/><line x1="9" y1="9" x2="15" y2="15"/></svg>
+      </div>
+      <div class="ai-msg-bubble ai-msg-bubble--ai ai-msg-bubble--error">
+        <span>{{ msg.content }}</span>
+        <button class="ai-retry-btn" :title="t('aiChat.retry')" @click.stop="emit('retry', msg)">
+          <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polyline points="1 4 1 10 7 10"/><path d="M3.51 15a9 9 0 102.13-9.36L1 10"/></svg>
+        </button>
+      </div>
+    </div>
+  </div>
+</template>

src/components/ai/MessageList.vue

@@ -19,9 +19,11 @@ import { useI18n } from 'vue-i18n'
 import { useAiStore } from '../../stores/ai'
 import { useMarkdown } from '../../composables/useMarkdown'
 import { useAppSettingsStore } from '../../stores/appSettings'
+import { useMessageScroll } from '../../composables/ai/useMessageScroll'
 import ToolCardList from '../ToolCardList.vue'
+import MessageItem from './MessageItem.vue'
 import { formatRelative, formatDate } from '../../utils/time'
-import type { AiMessage, ContentPart, MentionSpan } from '../../api/types'
+import type { AiMessage } from '../../api/types'
 
 defineProps<{
   /** UX-09:当前正在编辑的消息 id(父持有,经 ChatInput 透传);末条 user 编辑按钮据此隐藏 */
@@ -198,7 +200,7 @@ function scheduleStreamParse(text: string) {
       // B-260618-24: rAF 回调内 streamingBlocks 已赋值、DOM 高度就绪,跟随中则滚到真实底部。
       // 治 onContentChange 的 nextTick(scrollToBottom) 抢跑旧 scrollHeight(微任务先于 rAF,
       // 滚到渲染前高度)致"差一截"。
-      if (isFollowingBottom) scrollToBottom()
+      if (isFollowingBottom.value) scrollToBottom()
     })
   })
 }
@@ -210,62 +212,6 @@ function renderContent(msg: AiMessage): string {
   return renderMd(msg.content)
 }
 
-// ── Input Augmentation: 用户消息按 mention 区间切段(弃正则,纯元数据驱动) ──
-// 解决 🔴HIGH-2:正则误匹配(用户手打 [项目: x] 格式 / AI 模仿格式 / 项目名含 ] / 嵌套)。
-// 按 msg.mentionSpans(无则纯文本一段)按 start 升序切段:text → chip 替换。
-// 每 span 安全校验:content.slice(start, start+length) === span.label 否则降级为 text
-// (用户编辑破坏区间,如改了项目名/删了字符致偏移失效)。重叠/越界 span 也降级。
-type UserContentSegment =
-  | { type: 'text'; text: string }
-  | { type: 'chip'; span: MentionSpan }
-
-function segmentUserContent(msg: AiMessage): UserContentSegment[] {
-  const content = msg.content
-  const spans = msg.mentionSpans
-  // 无 mentionSpans(历史消息/纯文本)→ 一段 text 零回归
-  if (!spans || spans.length === 0) {
-    return [{ type: 'text', text: content }]
-  }
-
-  // 按 start 升序排序(稳定;不影响原数组)
-  const sorted = [...spans].sort((a, b) => a.start - b.start)
-
-  const segments: UserContentSegment[] = []
-  let cursor = 0 // 已消费到的字符偏移
-
-  for (const span of sorted) {
-    const start = span.start
-    const end = start + span.length
-
-    // 越界:起点/终点超出 content 长度 → 降级跳过(区间已失效)
-    if (start < 0 || end > content.length) continue
-    // 与前段重叠:起点在已消费 cursor 之前 → 降级跳过(防区间相互覆盖产生错乱)
-    if (start < cursor) continue
-    // 安全校验:切片内容必须 === span.label(用户编辑破坏区间则不等 → 降级跳过该 span)
-    if (content.slice(start, end) !== span.label) continue
-
-    // 前导 text(若有)
-    if (start > cursor) {
-      segments.push({ type: 'text', text: content.slice(cursor, start) })
-    }
-    // chip 段
-    segments.push({ type: 'chip', span })
-    cursor = end
-  }
-
-  // 收尾 tail text(末个 span 之后剩余)
-  if (cursor < content.length) {
-    segments.push({ type: 'text', text: content.slice(cursor) })
-  }
-
-  // 极端:所有 span 全降级且 content 非空 → segments 可能为空(无前导/tail),补一段完整 text
-  if (segments.length === 0 && content.length > 0) {
-    return [{ type: 'text', text: content }]
-  }
-
-  return segments
-}
-
 // ── UX-2025-20: 空状态示例问题 ──
 // 示例问题卡片(点击自动填入并发送);文案走 i18n key 数组,模板按 key 翻译。
 const examplePrompts = [
@@ -325,91 +271,20 @@ function isLastUser(msg: AiMessage): boolean {
   return false
 }
 
-/** ContentPart 图片片类型(discriminator type==='image' 的联合成员) */
-type ImageContentPart = Extract<ContentPart, { type: 'image' }>
-
-/** 取消息的图片 ContentPart 片(仅 type==='image');空数组=无图 */
-function msgImageParts(msg: AiMessage): ImageContentPart[] {
-  if (!msg.parts) return []
-  return msg.parts.filter((p): p is ImageContentPart => p.type === 'image')
-}
-
-/** ContentPart.image → <img src>:base64 模式拼 data URI,url 模式原样 */
-function imageSrc(img: ImageContentPart): string {
-  if (img.base64) {
-    // media_type 缺失兜底 image/png(provider 转发端点需完整 data URI)
-    const mt = img.media_type || 'image/png'
-    return `data:${mt};base64,${img.base64}`
-  }
-  return img.url || ''
-}
-
-/** ContentPart.image → alt 文案 */
-function imgAlt(img: ImageContentPart): string {
-  return img.alt || t('aiChat.imagePreviewAlt')
-}
-
 /** token 数格式化:<1000 原值,≥1000 用 k(如 1234→1.2k) */
 function formatTokens(n: number): string {
   return n >= 1000 ? `${(n / 1000).toFixed(1)}k` : String(n)
 }
 
-// ── 滚动跟随 / 回到底部(B-260618-24 跟随意图锁存) ──
+// ── 滚动跟随 / 回到底部(B-260618-24 跟随意图锁存,已抽取至 useMessageScroll) ──
-// 用户是否已在底部附近(上滑查看历史时不强制拉回)
+const {
-function isNearBottom(): boolean {
+  showBackToBottom,
-  const el = messagesContainer.value
+  isFollowingBottom,
-  if (!el) return true
+  onMessagesScroll,
-  return el.scrollHeight - el.scrollTop - el.clientHeight < 80
+  scrollToBottom,
-}
+  onContentChange,
-
+  setFollowing,
-// 回到底部按钮：内容溢出且不在底部时显示
+} = useMessageScroll(messagesContainer)
-const showBackToBottom = ref(false)
-// UX-260616-03: 跟随阅读位置自动收起 —— 用户滚近底部(在读最新内容)时,
-// 收起不再活跃的旧卡(视为已读)。用 wasNearBottom 边沿检测避免每个 scroll tick 都触发:
-// 仅在"远离底部 → 滚近底部"的转换瞬间收起一次,已在底部继续滚动不重复触发。
-let wasNearBottom = true
-// B-260618-24: 跟随意图锁存。原 onContentChange 仅靠 isNearBottom() 瞬时测量,流式 rAF 高频
-// 渲染下单帧增量 >80px 即判不在底 → 跟随意图一帧丢失(点回到底部后又失跟)。锁存解耦
-// "意图"与"瞬时测量":点回到底部/滚到底/发新消息→true;用户上滑→false。
-let isFollowingBottom = true
-function refreshBackToBottom() {
-  const el = messagesContainer.value
-  if (!el) { showBackToBottom.value = false; return }
-  const overflow = el.scrollHeight - el.clientHeight > 100
-  showBackToBottom.value = overflow && !isNearBottom()
-}
-function onMessagesScroll() {
-  refreshBackToBottom()
-  // UX-260616-03: 滚近底部 → 收起已读旧卡(边沿触发,防抖)
-  const near = isNearBottom()
-  if (near && !wasNearBottom) {
-    collapseAllToolLists(buildActiveToolIds(store.state.messages))
-  }
-  wasNearBottom = near
-  // B-260618-24: 用户主动滚离底部 = 放弃跟随;滚回底部 = 恢复跟随
-  isFollowingBottom = near
-}
-
-function scrollToBottom(smooth = false) {
-  if (messagesContainer.value) {
-    isFollowingBottom = true // 显式回底 = 跟随意图
-    messagesContainer.value.scrollTo({
-      top: messagesContainer.value.scrollHeight,
-      behavior: smooth ? 'smooth' : 'instant',
-    })
-    showBackToBottom.value = false
-  }
-}
-
-// 消息/流式变化时:跟随意图则自动滚;否则只刷新回底按钮(不强制打断)
-// 用 isFollowingBottom 锁存而非 isNearBottom 瞬时测量,避免流式高频下单帧突破阈值误判失跟
-function onContentChange() {
-  if (isFollowingBottom) {
-    nextTick(scrollToBottom)
-  } else {
-    refreshBackToBottom()
-  }
-}
 watch(() => store.state.messages.length, onContentChange)
 // SW-260618-07: currentText → onContentChange 合并到下方 scheduleStreamParse watch(同源 currentText,单 callback 顺序执行)
 
@@ -840,10 +715,8 @@ const renderItems = computed<RenderItem[]>(() => {
 
 // UX-09:切换对话/新对话时由父取消编辑态;滚动边沿/跟随意图重置在此自管(SW-260618-18/B-260618-24)。
 watch(() => store.state.activeConversationId, () => {
-  // SW-260618-18: 切会话重置滚动边沿检测,防会话 A 上滑残留 wasNearBottom=false 致切到 B 后首滚误触发 collapseAllToolLists
+  // SW-260618-18: 切会话重置滚动边沿检测 + 跟随意图(新会话默认跟随底部)
-  wasNearBottom = true
+  setFollowing(true)
-  // B-260618-24: 切会话重置跟随意图(新会话默认跟随底部,防 A 上滑残留 isFollowingBottom=false)
-  isFollowingBottom = true
   // BUG-260624-01(消息重叠根治·论证 workflow 完整性高优):MessageList 是持久单实例(AiChat.vue
   // 无 :key/v-if 卸载),实例级 streamingBlocks(:69)跨会话/跨轮残留是消息重叠主根因之一。
   // 钉在「会话切换」这一确切时机清,根治两条残留路径:① switchConversation(useAiConversations)
@@ -875,7 +748,7 @@ defineExpose({
 
 <template>
   <!-- Messages -->
-  <div class="ai-messages" ref="messagesContainer" @scroll="onMessagesScroll">
+  <div class="ai-messages" ref="messagesContainer" @scroll="onMessagesScroll(() => collapseAllToolLists(buildActiveToolIds(store.state.messages)))">
     <!-- 空状态 (UX-2025-20: 示例问题卡片 + 无 provider 引导跳 Settings) -->
     <div class="ai-empty" v-if="store.state.messages.length === 0 && !store.state.streaming">
       <template v-if="store.state.providers.length === 0">
@@ -959,56 +832,17 @@ defineExpose({
         <span class="ai-msg-system-label">{{ $t('aiChat.compressedSummaryLabel') }}</span>
         <div class="ai-msg-system-summary ai-md" v-html="renderContent(item.msg)"></div>
       </div>
-      <!-- 用户消息 -->
+      <!-- 用户消息(提取至 MessageItem.vue) -->
-      <div v-else-if="item.msg.role === 'user'" class="ai-msg-user">
+      <MessageItem
-        <div class="ai-msg-avatar ai-msg-avatar--user">
+        v-else-if="item.msg.role === 'user'"
-          <svg width="11" height="11" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M20 21v-2a4 4 0 00-4-4H8a4 4 0 00-4 4v2"/><circle cx="12" cy="7" r="4"/></svg>
+        :msg="item.msg"
-        </div>
+        :is-last-ai="isLastAi(item.msg)"
-        <div class="ai-msg-bubble ai-msg-bubble--user">
+        :is-last-user="isLastUser(item.msg)"
-          <!-- Input Augmentation: 按 mention 区间切段渲染(chip 精确替换 [类型: 名] 标记,弃正则)。
+        :editing-msg-id="editingMsgId"
-               无 mentionSpans 时 segmentUserContent 返回单段 text(零回归,等同原 {{ content }})。 -->
+        :is-viewing-generating="isViewingGenerating"
-          <template v-for="(seg, i) in segmentUserContent(item.msg)" :key="(item.msg.id) + '-seg-' + i">
+        @copy="copyMsgContent"
-            <span v-if="seg.type === 'text'">{{ seg.text }}</span>
+        @start-edit="(m) => emit('start-edit', m)"
-            <span
+      />
-              v-else
-              class="ai-msg-chip"
-              :class="'ai-msg-chip--' + seg.span.kind"
-            >{{ seg.span.label }}</span>
-          </template>
-          <!-- F-260614-05 Phase 2b: 多模态图片渲染(随消息气泡挂载/卸载;
-               B-260618-01 虚拟滚动已移除,气泡内 <img> 随消息恒渲染无裁剪) -->
-          <template v-if="msgImageParts(item.msg).length">
-            <div class="ai-msg-images">
-              <img
-                v-for="(img, i) in msgImageParts(item.msg)"
-                :key="(item.msg.id) + '-img-' + i"
-                :src="imageSrc(img)"
-                :alt="imgAlt(img)"
-                class="ai-msg-image"
-                loading="lazy"
-              />
-            </div>
-          </template>
-          <button
-            class="ai-copy-btn"
-            :title="$t('aiChat.copyMsg')"
-            @click.stop="copyMsgContent(item.msg)"
-          >
-            <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><rect x="9" y="9" width="13" height="13" rx="2" ry="2"/><path d="M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1"/></svg>
-          </button>
-        </div>
-        <!-- UX-09:末条 user 消息编辑按钮(非生成中、非当前编辑态)hover 显示 -->
-        <button
-          v-if="isLastUser(item.msg) && !store.state.streaming && !editingMsgId"
-          class="ai-msg-edit-btn"
-          :title="$t('aiChat.editMessage')"
-          @click.stop="emit('start-edit', item.msg)"
-        >
-          <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M11 4H4a2 2 0 00-2 2v14a2 2 0 002 2h14a2 2 0 002-2v-7"/><path d="M18.5 2.5a2.121 2.121 0 013 3L12 15l-4 1 1-4 9.5-9.5z"/></svg>
-        </button>
-        <!-- UX-2025-13:消息时间戳(相对时间+hover绝对时间) -->
-        <span class="ai-msg-time ai-msg-time--user" :title="formatDate(item.msg.timestamp)">{{ formatRelative(item.msg.timestamp) }}</span>
-      </div>
 
       <!-- AI 消息 -->
       <div v-else class="ai-msg-ai">

src/composables/ai/useMessageScroll.ts

@@ -0,0 +1,89 @@
+//! 消息列表滚动控制 — 跟随/锁存/回底按钮
+//!
+//! 职责:悬浮底部按钮显隐、跟随意图锁存(isFollowingBottom)、
+//! scrollToBottom 回底操作、onContentChange 内容变化滚动策略。
+//!
+//! 不涉及工具卡片折叠逻辑(父组件注入 onNearBottom 回调解耦)。
+
+import { ref, nextTick, type Ref } from 'vue'
+
+/** 底部阈值:距底部 <80px 视为"在底部" */
+const NEAR_BOTTOM_PX = 80
+/** 内容溢出阈值:scrollHeight - clientHeight >100px 认为内容溢出容器 */
+const OVERFLOW_PX = 100
+
+export function useMessageScroll(containerRef: Ref<HTMLDivElement | undefined>) {
+  // 回到底部按钮：内容溢出且不在底部时显示
+  const showBackToBottom = ref(false)
+
+  // B-260618-24: 跟随意图锁存。点回到底部/滚到底/发新消息→true;用户上滑→false。
+  const isFollowingBottom = ref(true)
+  // 边沿检测:上一帧是否在底部(用于触发 onNearBottom 回调)
+  let wasNearBottom = true
+
+  /** 用户是否在底部附近(上滑查看历史时不强制拉回) */
+  function isNearBottom(): boolean {
+    const el = containerRef.value
+    if (!el) return true
+    return el.scrollHeight - el.scrollTop - el.clientHeight < NEAR_BOTTOM_PX
+  }
+
+  /** 刷新回到底部按钮状态 */
+  function refreshBackToBottom(): void {
+    const el = containerRef.value
+    if (!el) { showBackToBottom.value = false; return }
+    const overflow = el.scrollHeight - el.clientHeight > OVERFLOW_PX
+    showBackToBottom.value = overflow && !isNearBottom()
+  }
+
+  /**
+   * 滚动事件处理:刷新回底按钮 + 底部边沿检测触发回调。
+   * @param onNearBottom 滚近底部时的回调(父组件传入,如收起工具卡片)
+   */
+  function onMessagesScroll(onNearBottom?: () => void): void {
+    refreshBackToBottom()
+    const near = isNearBottom()
+    if (near && !wasNearBottom) {
+      onNearBottom?.()
+    }
+    wasNearBottom = near
+    isFollowingBottom.value = near
+  }
+
+  /** 滚动到容器底部 */
+  function scrollToBottom(smooth = false): void {
+    const el = containerRef.value
+    if (!el) return
+    isFollowingBottom.value = true // 显式回底 = 跟随意图
+    el.scrollTo({
+      top: el.scrollHeight,
+      behavior: smooth ? 'smooth' : 'instant',
+    })
+    showBackToBottom.value = false
+  }
+
+  /** 消息/流式内容变化时:跟随意图则自动滚,否则只刷新回底按钮 */
+  function onContentChange(): void {
+    if (isFollowingBottom.value) {
+      nextTick(scrollToBottom)
+    } else {
+      refreshBackToBottom()
+    }
+  }
+
+  /** 显式标记跟随意图(发新消息/切换对话时调用) */
+  function setFollowing(v: boolean): void {
+    isFollowingBottom.value = v
+  }
+
+  return {
+    showBackToBottom,
+    isFollowingBottom,
+    isNearBottom,
+    refreshBackToBottom,
+    onMessagesScroll,
+    scrollToBottom,
+    onContentChange,
+    setFollowing,
+  }
+}