test(chat): 覆盖系统撤回/群名片/实时会话同步相关用例

- 新增系统撤回消息 replacemsg 解析与导出语义测试

- 新增群聊会话预览格式化与群名片 ext_buffer 解析测试

- 新增 realtime 会话列表与 sync_all 落库 last_sender_display_name 测试

frontend/pages/chat/[[username]].vue

@@ -242,14 +242,20 @@
               @click="selectContact(contact)">
               <div class="flex items-center space-x-3 w-full">
                 <!-- 联系人头像 -->
-                <div class="w-[calc(45px/var(--dpr))] h-[calc(45px/var(--dpr))] rounded-md overflow-hidden bg-gray-300 flex-shrink-0" :class="{ 'privacy-blur': privacyMode }">
-                  <div v-if="contact.avatar" class="w-full h-full">
-                    <img :src="contact.avatar" :alt="contact.name" class="w-full h-full object-cover" referrerpolicy="no-referrer" @error="onAvatarError($event, contact)">
-                  </div>
-                  <div v-else class="w-full h-full flex items-center justify-center text-white text-xs font-bold"
-                    :style="{ backgroundColor: contact.avatarColor || '#4B5563' }">
-                    {{ contact.name.charAt(0) }}
+                <div class="relative flex-shrink-0" :class="{ 'privacy-blur': privacyMode }">
+                  <div class="w-[calc(45px/var(--dpr))] h-[calc(45px/var(--dpr))] rounded-md overflow-hidden bg-gray-300">
+                    <div v-if="contact.avatar" class="w-full h-full">
+                      <img :src="contact.avatar" :alt="contact.name" class="w-full h-full object-cover" referrerpolicy="no-referrer" @error="onAvatarError($event, contact)">
+                    </div>
+                    <div v-else class="w-full h-full flex items-center justify-center text-white text-xs font-bold"
+                      :style="{ backgroundColor: contact.avatarColor || '#4B5563' }">
+                      {{ contact.name.charAt(0) }}
+                    </div>
                   </div>
+                  <span
+                    v-if="contact.unreadCount > 0"
+                    class="absolute z-10 -top-[calc(4px/var(--dpr))] -right-[calc(4px/var(--dpr))] w-[calc(10px/var(--dpr))] h-[calc(10px/var(--dpr))] bg-[#ed4d4d] rounded-full"
+                  ></span>
                 </div>
                 
                 <!-- 联系人信息 -->
@@ -257,13 +263,12 @@
                   <div class="flex items-center justify-between">
                     <h3 class="text-sm font-medium text-gray-900 truncate" :class="{ 'privacy-blur': privacyMode }">{{ contact.name }}</h3>
                     <div class="flex items-center flex-shrink-0 ml-2">
-                      <span v-if="contact.unreadCount > 0" class="text-[10px] text-white bg-red-500 rounded-full min-w-[18px] h-[18px] px-1 flex items-center justify-center mr-2">
-                        {{ contact.unreadCount > 99 ? '99+' : contact.unreadCount }}
-                      </span>
                       <span class="text-xs text-gray-500">{{ contact.lastMessageTime }}</span>
                     </div>
                   </div>
-                  <p class="text-xs text-gray-500 truncate mt-0.5 leading-tight" :class="{ 'privacy-blur': privacyMode }">{{ contact.lastMessage }}</p>
+                  <p class="text-xs text-gray-500 truncate mt-0.5 leading-tight" :class="{ 'privacy-blur': privacyMode }">
+                    {{ contact.unreadCount > 0 ? `[${contact.unreadCount > 99 ? '99+' : contact.unreadCount}条] ` : '' }}{{ contact.lastMessage }}
+                  </p>
                 </div>
               </div>
             </div>
@@ -616,15 +621,15 @@
                         <img v-else :src="seg.emojiSrc" :alt="seg.content" class="inline-block w-[1.25em] h-[1.25em] align-text-bottom mx-px">
                       </span>
                     </div>
-                    <div
-                      v-if="message.quoteTitle || message.quoteContent"
-                      class="mt-[5px] px-2 text-xs text-neutral-600 rounded max-w-[404px] max-h-[61px] flex items-center bg-[#e1e1e1]">
-                      <div class="py-2 min-w-0 w-full">
-                        <div v-if="isQuotedVoice(message)" class="flex items-center gap-1 min-w-0">
-                          <span v-if="message.quoteTitle" class="truncate flex-shrink-0">{{ message.quoteTitle }}:</span>
-                          <button
-                            type="button"
-                            class="flex items-center gap-1 min-w-0 hover:opacity-80"
+                      <div
+                        v-if="message.quoteTitle || message.quoteContent"
+                       class="mt-[5px] px-2 text-xs text-neutral-600 rounded max-w-[404px] max-h-[65px] overflow-hidden flex items-start bg-[#e1e1e1]">
+                       <div class="py-2 min-w-0 flex-1">
+                         <div v-if="isQuotedVoice(message)" class="flex items-center gap-1 min-w-0">
+                           <span v-if="message.quoteTitle" class="truncate flex-shrink-0">{{ message.quoteTitle }}:</span>
+                           <button
+                             type="button"
+                             class="flex items-center gap-1 min-w-0 hover:opacity-80"
                             :disabled="!message.quoteVoiceUrl"
                             :class="!message.quoteVoiceUrl ? 'opacity-60 cursor-not-allowed' : ''"
                             @click.stop="message.quoteVoiceUrl && playQuoteVoice(message)"
@@ -647,13 +652,35 @@
                             :ref="el => setVoiceRef(getQuoteVoiceId(message), el)"
                             :src="message.quoteVoiceUrl"
                             preload="none"
-                            class="hidden"
-                          ></audio>
-                        </div>
-                        <div v-else class="line-clamp-2">{{ message.quoteTitle ? (message.quoteTitle + ': ') : '' }}{{ message.quoteContent }}</div>
-                      </div>
-                    </div>
-                  </template>
+                             class="hidden"
+                           ></audio>
+                         </div>
+                         <div v-else class="line-clamp-2">
+                           <span v-if="message.quoteTitle">{{ message.quoteTitle }}:</span>
+                           <span
+                             v-if="message.quoteContent && !(isQuotedImage(message) && message.quoteTitle && message.quoteImageUrl && !message._quoteImageError)"
+                             :class="message.quoteTitle ? 'ml-1' : ''"
+                           >
+                             {{ message.quoteContent }}
+                           </span>
+                         </div>
+                       </div>
+                       <div
+                         v-if="isQuotedImage(message) && message.quoteImageUrl && !message._quoteImageError"
+                         class="ml-2 my-2 flex-shrink-0 w-[45px] h-[45px] rounded overflow-hidden cursor-pointer"
+                         @click.stop="openImagePreview(message.quoteImageUrl)"
+                       >
+                         <img
+                           :src="message.quoteImageUrl"
+                           alt="引用图片"
+                           class="w-full h-full object-contain"
+                           loading="lazy"
+                           decoding="async"
+                           @error="onQuoteImageError(message)"
+                         />
+                       </div>
+                     </div>
+                   </template>
                   <!-- 合并转发聊天记录（Chat History） -->
                   <div
                     v-else-if="message.renderType === 'chatHistory'"
@@ -3464,6 +3491,19 @@ const isQuotedVoice = (message) => {
   return false
 }
 
+const isQuotedImage = (message) => {
+  const t = String(message?.quoteType || '').trim()
+  if (t === '3') return true
+  if (String(message?.quoteContent || '').trim() === '[图片]' && String(message?.quoteServerId || '').trim()) return true
+  return false
+}
+
+const onQuoteImageError = (message) => {
+  try {
+    if (message) message._quoteImageError = true
+  } catch {}
+}
+
 const playQuoteVoice = (message) => {
   playVoice({ id: getQuoteVoiceId(message) })
 }
@@ -4665,6 +4705,23 @@ const normalizeMessage = (msg) => {
     }
   }
 
+  const quoteServerIdStr = String(msg.quoteServerId || '').trim()
+  const quoteTypeStr = String(msg.quoteType || '').trim()
+  const quoteVoiceUrl = quoteServerIdStr
+    ? `${mediaBase}/api/chat/media/voice?account=${encodeURIComponent(selectedAccount.value || '')}&server_id=${encodeURIComponent(quoteServerIdStr)}`
+    : ''
+  const quoteImageUrl = (() => {
+    if (!quoteServerIdStr) return ''
+    if (quoteTypeStr !== '3' && String(msg.quoteContent || '').trim() !== '[图片]') return ''
+    const convUsername = String(selectedContact.value?.username || '').trim()
+    const parts = [
+      `account=${encodeURIComponent(selectedAccount.value || '')}`,
+      `server_id=${encodeURIComponent(quoteServerIdStr)}`,
+      convUsername ? `username=${encodeURIComponent(convUsername)}` : ''
+    ].filter(Boolean)
+    return parts.length ? `${mediaBase}/api/chat/media/image?${parts.join('&')}` : ''
+  })()
+
   return {
     id: msg.id,
     serverId: msg.serverId || 0,
@@ -4701,12 +4758,12 @@ const normalizeMessage = (msg) => {
     quoteTitle: msg.quoteTitle || '',
     quoteContent,
     quoteUsername: msg.quoteUsername || '',
-    quoteServerId: String(msg.quoteServerId || '').trim(),
-    quoteType: String(msg.quoteType || '').trim(),
+    quoteServerId: quoteServerIdStr,
+    quoteType: quoteTypeStr,
     quoteVoiceLength: msg.quoteVoiceLength || '',
-    quoteVoiceUrl: String(msg.quoteServerId || '').trim()
-      ? `${mediaBase}/api/chat/media/voice?account=${encodeURIComponent(selectedAccount.value || '')}&server_id=${encodeURIComponent(String(msg.quoteServerId || '').trim())}`
-      : '',
+    quoteVoiceUrl,
+    quoteImageUrl: quoteImageUrl || '',
+    _quoteImageError: false,
     amount: msg.amount || '',
     coverUrl: msg.coverUrl || '',
     fileSize: msg.fileSize || '',

src/wechat_decrypt_tool/chat_export_service.py

@@ -28,6 +28,7 @@ from .chat_helpers import (
     _load_contact_rows,
     _lookup_resource_md5,
     _parse_app_message,
+    _parse_system_message_content,
     _parse_pat_message,
     _pick_display_name,
     _quote_ident,
@@ -954,13 +955,7 @@ def _parse_message_for_export(
 
     if local_type == 10000:
         render_type = "system"
-        if "revokemsg" in raw_text:
-            content_text = "撤回了一条消息"
-        else:
-            import re as _re
-
-            content_text = _re.sub(r"</?[_a-zA-Z0-9]+[^>]*>", "", raw_text)
-            content_text = _re.sub(r"\\s+", " ", content_text).strip() or "[系统消息]"
+        content_text = _parse_system_message_content(raw_text)
     elif local_type == 49:
         parsed = _parse_app_message(raw_text)
         render_type = str(parsed.get("renderType") or "text")

src/wechat_decrypt_tool/chat_helpers.py

@@ -645,6 +645,43 @@ def _extract_xml_tag_or_attr(xml_text: str, name: str) -> str:
     return _extract_xml_attr(xml_text, name)
 
 
+def _parse_system_message_content(raw_text: str) -> str:
+    text = str(raw_text or "").strip()
+    if not text:
+        return "[系统消息]"
+
+    def _clean_system_text(value: str) -> str:
+        candidate = str(value or "").strip()
+        if not candidate:
+            return ""
+
+        nested_content = _extract_xml_tag_text(candidate, "content")
+        if nested_content:
+            candidate = nested_content
+
+        candidate = re.sub(r"<!\[CDATA\[", "", candidate, flags=re.IGNORECASE)
+        candidate = re.sub(r"\]\]>", "", candidate)
+        candidate = re.sub(r"</?[_a-zA-Z0-9]+[^>]*>", "", candidate)
+        candidate = re.sub(r"\s+", " ", candidate).strip()
+        return candidate
+
+    if "revokemsg" in text.lower():
+        replace_msg = _extract_xml_tag_text(text, "replacemsg")
+        cleaned_replace_msg = _clean_system_text(replace_msg)
+        if cleaned_replace_msg:
+            return cleaned_replace_msg
+
+        revoke_msg = _extract_xml_tag_text(text, "revokemsg")
+        cleaned_revoke_msg = _clean_system_text(revoke_msg)
+        if cleaned_revoke_msg:
+            return cleaned_revoke_msg
+
+        return "撤回了一条消息"
+
+    content_text = _clean_system_text(text)
+    return content_text or "[系统消息]"
+
+
 def _extract_refermsg_block(xml_text: str) -> str:
     if not xml_text:
         return ""
@@ -1053,11 +1090,7 @@ def _build_latest_message_preview(
 
     content_text = ""
     if local_type == 10000:
-        if "revokemsg" in raw_text:
-            content_text = "撤回了一条消息"
-        else:
-            content_text = re.sub(r"</?[_a-zA-Z0-9]+[^>]*>", "", raw_text)
-            content_text = re.sub(r"\s+", " ", content_text).strip() or "[系统消息]"
+        content_text = _parse_system_message_content(raw_text)
     elif local_type == 244813135921:
         parsed = _parse_app_message(raw_text)
         qt = str(parsed.get("quoteTitle") or "").strip()
@@ -1093,7 +1126,7 @@ def _build_latest_message_preview(
     elif local_type == 43 or local_type == 62:
         content_text = "[视频]"
     elif local_type == 47:
-        content_text = "[表情]"
+        content_text = "[动画表情]"
     else:
         if raw_text and (not raw_text.startswith("<")) and (not raw_text.startswith('"<')):
             content_text = raw_text
@@ -1107,6 +1140,101 @@ def _build_latest_message_preview(
     return content_text
 
 
+def _extract_group_preview_sender_username(preview_text: str) -> str:
+    text = str(preview_text or "").strip()
+    if not text:
+        return ""
+
+    match = re.match(r"^([^:\s]{1,128}):\s*.+$", text)
+    if not match:
+        return ""
+
+    sender = str(match.group(1) or "").strip()
+    if not sender:
+        return ""
+
+    if sender.startswith("wxid_") or sender.endswith("@chatroom") or ("@" in sender):
+        return sender
+    if re.fullmatch(r"[A-Za-z][A-Za-z0-9_-]{1,127}", sender):
+        return sender
+    return ""
+
+
+def _normalize_session_preview_text(
+    preview_text: str,
+    *,
+    is_group: bool,
+    sender_display_names: Optional[dict[str, str]] = None,
+) -> str:
+    text = re.sub(r"\s+", " ", str(preview_text or "").strip()).strip()
+    if not text:
+        return ""
+
+    text = text.replace("[表情]", "[动画表情]")
+    if (not is_group) or text.startswith("[草稿]"):
+        return text
+
+    match = re.match(r"^([^:\s]{1,128}):\s*(.+)$", text)
+    if not match:
+        return text
+
+    sender_username = str(match.group(1) or "").strip()
+    body = str(match.group(2) or "").strip()
+    if (not sender_username) or (not body):
+        return text
+
+    display_name = str((sender_display_names or {}).get(sender_username) or "").strip()
+    if display_name and display_name != sender_username:
+        return f"{display_name}: {body}"
+    return text
+
+
+def _replace_preview_sender_prefix(preview_text: str, sender_display_name: str) -> str:
+    text = re.sub(r"\s+", " ", str(preview_text or "").strip()).strip()
+    if not text:
+        return ""
+
+    display_name = str(sender_display_name or "").strip()
+    if (not display_name) or text.startswith("[草稿]"):
+        return text
+
+    match = re.match(r"^([^:\n]{1,128}):\s*(.+)$", text)
+    if not match:
+        return text
+
+    body = re.sub(r"\s+", " ", str(match.group(2) or "").strip()).strip()
+    if not body:
+        return text
+    return f"{display_name}: {body}"
+
+
+def _build_group_sender_display_name_map(
+    contact_db_path: Path,
+    previews: dict[str, str],
+) -> dict[str, str]:
+    group_sender_usernames: set[str] = set()
+    for conv_username, preview_text in previews.items():
+        if not str(conv_username or "").endswith("@chatroom"):
+            continue
+        sender_username = _extract_group_preview_sender_username(preview_text)
+        if sender_username:
+            group_sender_usernames.add(sender_username)
+
+    if not group_sender_usernames:
+        return {}
+
+    display_names: dict[str, str] = {}
+    sender_contact_rows = _load_contact_rows(contact_db_path, list(group_sender_usernames))
+    for sender_username in group_sender_usernames:
+        row = sender_contact_rows.get(sender_username)
+        if row is None:
+            continue
+        display_name = _pick_display_name(row, sender_username)
+        if display_name and display_name != sender_username:
+            display_names[sender_username] = display_name
+    return display_names
+
+
 def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> dict[str, str]:
     if not usernames:
         return {}
@@ -1338,6 +1466,208 @@ def _load_contact_rows(contact_db_path: Path, usernames: list[str]) -> dict[str,
         conn.close()
 
 
+def _load_group_nickname_map_from_contact_db(
+    contact_db_path: Path,
+    chatroom_id: str,
+    sender_usernames: list[str],
+) -> dict[str, str]:
+    """Best-effort mapping for group member nickname (aka group card) from contact.db.
+
+    WeChat stores per-chatroom member nicknames in `contact.db.chat_room.ext_buffer` as a protobuf-like blob.
+    This helper parses that blob and returns { sender_username -> group_nickname } for the requested senders.
+
+    Notes:
+    - Best-effort: never raises; returns {} on any failure.
+    - Only resolves usernames included in `sender_usernames` to keep parsing cheap.
+    """
+
+    chatroom = str(chatroom_id or "").strip()
+    if not chatroom.endswith("@chatroom"):
+        return {}
+
+    targets = list(dict.fromkeys([str(x or "").strip() for x in sender_usernames if str(x or "").strip()]))
+    if not targets:
+        return {}
+    target_set = set(targets)
+
+    def decode_varint(raw: bytes, offset: int) -> tuple[Optional[int], int]:
+        value = 0
+        shift = 0
+        pos = int(offset)
+        n = len(raw)
+        while pos < n:
+            byte = raw[pos]
+            pos += 1
+            value |= (byte & 0x7F) << shift
+            if (byte & 0x80) == 0:
+                return value, pos
+            shift += 7
+            if shift > 63:
+                return None, n
+        return None, n
+
+    def iter_fields(raw: bytes):
+        idx = 0
+        n = len(raw)
+        while idx < n:
+            tag, idx_next = decode_varint(raw, idx)
+            if tag is None or idx_next <= idx:
+                break
+            idx = idx_next
+            field_no = int(tag) >> 3
+            wire_type = int(tag) & 0x7
+
+            if wire_type == 0:
+                _, idx_next = decode_varint(raw, idx)
+                if idx_next <= idx:
+                    break
+                idx = idx_next
+                continue
+
+            if wire_type == 2:
+                size, idx_next = decode_varint(raw, idx)
+                if size is None or idx_next <= idx:
+                    break
+                idx = idx_next
+                end = idx + int(size)
+                if end > n:
+                    break
+                chunk = raw[idx:end]
+                idx = end
+                yield field_no, wire_type, chunk
+                continue
+
+            if wire_type == 1:
+                idx += 8
+                continue
+            if wire_type == 5:
+                idx += 4
+                continue
+            break
+
+    def is_strong_username_hint(s: str) -> bool:
+        v = str(s or "").strip()
+        return v.startswith("wxid_") or v.endswith("@chatroom") or v.startswith("gh_") or ("@" in v)
+
+    def looks_like_username(s: str) -> bool:
+        v = str(s or "").strip()
+        if not v:
+            return False
+        if is_strong_username_hint(v):
+            return True
+        # Common alias-style WeChat IDs are ASCII-ish and do not contain whitespace.
+        if len(v) < 6 or len(v) > 32:
+            return False
+        if re.search(r"\s", v):
+            return False
+        if not re.match(r"^[A-Za-z][A-Za-z0-9_-]+$", v):
+            return False
+        if v.isdigit():
+            return False
+        return True
+
+    def pick_display(strings: list[tuple[int, str]], target: str) -> str:
+        best_score = -1
+        best = ""
+        for i, (fno, value) in enumerate(strings):
+            v = str(value or "").strip()
+            if (not v) or v == target:
+                continue
+            if is_strong_username_hint(v):
+                continue
+            if "\n" in v or "\r" in v:
+                continue
+            if len(v) > 64:
+                continue
+
+            score = 0
+            if int(fno) == 2:
+                score += 100
+            if not looks_like_username(v):
+                score += 20
+            score += max(0, 32 - len(v))
+            # Stable tie-breaker: prefer earlier appearance.
+            score = score * 1000 - i
+            if score > best_score:
+                best_score = score
+                best = v
+        return best
+
+    try:
+        conn = sqlite3.connect(str(contact_db_path))
+    except Exception:
+        return {}
+
+    try:
+        row = conn.execute(
+            "SELECT ext_buffer FROM chat_room WHERE username = ? LIMIT 1",
+            (chatroom,),
+        ).fetchone()
+        if row is None:
+            return {}
+
+        ext = row[0]
+        if ext is None:
+            return {}
+        if isinstance(ext, memoryview):
+            ext_buf = ext.tobytes()
+        elif isinstance(ext, (bytes, bytearray)):
+            ext_buf = bytes(ext)
+        else:
+            return {}
+        if not ext_buf:
+            return {}
+
+        out: dict[str, str] = {}
+        for _, wire_type, chunk in iter_fields(ext_buf):
+            if wire_type != 2 or (not chunk):
+                continue
+
+            # Parse submessage and collect UTF-8 strings.
+            strings: list[tuple[int, str]] = []
+            try:
+                for sfno, swire, sval in iter_fields(chunk):
+                    if swire != 2:
+                        continue
+                    if not sval:
+                        continue
+                    if len(sval) > 256:
+                        continue
+                    try:
+                        txt = bytes(sval).decode("utf-8", errors="strict")
+                    except Exception:
+                        continue
+                    txt = txt.strip()
+                    if not txt:
+                        continue
+                    strings.append((int(sfno), txt))
+            except Exception:
+                continue
+
+            if not strings:
+                continue
+
+            present = [v for _, v in strings if v in target_set and v not in out]
+            if not present:
+                continue
+
+            for target in present:
+                disp = pick_display(strings, target)
+                if disp:
+                    out[target] = disp
+            if len(out) >= len(target_set):
+                break
+
+        return out
+    except Exception:
+        return {}
+    finally:
+        try:
+            conn.close()
+        except Exception:
+            pass
+
+
 def _load_usernames_by_display_names(contact_db_path: Path, names: list[str]) -> dict[str, str]:
     """Best-effort mapping from display name -> username using contact.db.
 
@@ -1515,11 +1845,7 @@ def _row_to_search_hit(
 
     if local_type == 10000:
         render_type = "system"
-        if "revokemsg" in raw_text:
-            content_text = "撤回了一条消息"
-        else:
-            content_text = re.sub(r"</?[_a-zA-Z0-9]+[^>]*>", "", raw_text)
-            content_text = re.sub(r"\s+", " ", content_text).strip() or "[系统消息]"
+        content_text = _parse_system_message_content(raw_text)
     elif local_type == 49:
         parsed = _parse_app_message(raw_text)
         render_type = str(parsed.get("renderType") or "text")

src/wechat_decrypt_tool/media_helpers.py

@@ -23,17 +23,17 @@ logger = get_logger(__name__)
 
 
 # 运行时输出目录（桌面端可通过 WECHAT_TOOL_DATA_DIR 指向可写目录）
-_OUTPUT_DATABASES_DIR = get_output_databases_dir()
 _PACKAGE_ROOT = Path(__file__).resolve().parent
 
 
 def _list_decrypted_accounts() -> list[str]:
     """列出已解密输出的账号目录名（仅保留包含 session.db + contact.db 的账号）"""
-    if not _OUTPUT_DATABASES_DIR.exists():
+    output_db_dir = get_output_databases_dir()
+    if not output_db_dir.exists():
         return []
 
     accounts: list[str] = []
-    for p in _OUTPUT_DATABASES_DIR.iterdir():
+    for p in output_db_dir.iterdir():
         if not p.is_dir():
             continue
         if (p / "session.db").exists() and (p / "contact.db").exists():
@@ -45,6 +45,7 @@ def _list_decrypted_accounts() -> list[str]:
 
 def _resolve_account_dir(account: Optional[str]) -> Path:
     """解析账号目录，并进行路径安全校验（防止路径穿越）"""
+    output_db_dir = get_output_databases_dir()
     accounts = _list_decrypted_accounts()
     if not accounts:
         raise HTTPException(
@@ -53,8 +54,8 @@ def _resolve_account_dir(account: Optional[str]) -> Path:
         )
 
     selected = account or accounts[0]
-    base = _OUTPUT_DATABASES_DIR.resolve()
-    candidate = (_OUTPUT_DATABASES_DIR / selected).resolve()
+    base = output_db_dir.resolve()
+    candidate = (output_db_dir / selected).resolve()
 
     if candidate != base and base not in candidate.parents:
         raise HTTPException(status_code=400, detail="Invalid account path.")

src/wechat_decrypt_tool/routers/chat.py

@@ -39,11 +39,17 @@ from ..chat_helpers import (
     _make_snippet,
     _match_tokens,
     _load_contact_rows,
+    _load_group_nickname_map_from_contact_db,
     _load_usernames_by_display_names,
     _load_latest_message_previews,
+    _build_group_sender_display_name_map,
+    _normalize_session_preview_text,
+    _extract_group_preview_sender_username,
+    _replace_preview_sender_prefix,
     _lookup_resource_md5,
     _normalize_xml_url,
     _parse_app_message,
+    _parse_system_message_content,
     _parse_pat_message,
     _pick_display_name,
     _query_head_image_usernames,
@@ -69,6 +75,8 @@ from ..wcdb_realtime import (
     WCDB_REALTIME,
     get_avatar_urls as _wcdb_get_avatar_urls,
     get_display_names as _wcdb_get_display_names,
+    get_group_members as _wcdb_get_group_members,
+    get_group_nicknames as _wcdb_get_group_nicknames,
     get_messages as _wcdb_get_messages,
     get_sessions as _wcdb_get_sessions,
 )
@@ -97,6 +105,142 @@ def _avatar_url_unified(
     return _build_avatar_url(str(account_dir.name or ""), u)
 
 
+def _load_group_nickname_map_from_wcdb(
+    *,
+    account_dir: Path,
+    chatroom_id: str,
+    sender_usernames: list[str],
+    rt_conn=None,
+) -> dict[str, str]:
+    chatroom = str(chatroom_id or "").strip()
+    if not chatroom.endswith("@chatroom"):
+        return {}
+
+    targets = list(dict.fromkeys([str(x or "").strip() for x in sender_usernames if str(x or "").strip()]))
+    if not targets:
+        return {}
+
+    try:
+        wcdb_conn = rt_conn or WCDB_REALTIME.ensure_connected(account_dir)
+    except Exception:
+        return {}
+
+    target_set = set(targets)
+    out: dict[str, str] = {}
+
+    try:
+        with wcdb_conn.lock:
+            nickname_map = _wcdb_get_group_nicknames(wcdb_conn.handle, chatroom)
+        for username, nickname in (nickname_map or {}).items():
+            su = str(username or "").strip()
+            nn = str(nickname or "").strip()
+            if su and nn and su in target_set:
+                out[su] = nn
+    except Exception:
+        pass
+
+    unresolved = [u for u in targets if u not in out]
+    if not unresolved:
+        return out
+
+    try:
+        with wcdb_conn.lock:
+            members = _wcdb_get_group_members(wcdb_conn.handle, chatroom)
+    except Exception:
+        return out
+
+    if not members:
+        return out
+
+    unresolved_set = set(unresolved)
+    for member in members:
+        try:
+            username = str(member.get("username") or "").strip()
+        except Exception:
+            username = ""
+        if (not username) or (username not in unresolved_set):
+            continue
+
+        nickname = ""
+        for key in ("nickname", "displayName", "remark", "originalName"):
+            try:
+                candidate = str(member.get(key) or "").strip()
+            except Exception:
+                candidate = ""
+            if candidate:
+                nickname = candidate
+                break
+        if nickname:
+            out[username] = nickname
+
+    return out
+
+
+def _load_group_nickname_map(
+    *,
+    account_dir: Path,
+    contact_db_path: Path,
+    chatroom_id: str,
+    sender_usernames: list[str],
+    rt_conn=None,
+) -> dict[str, str]:
+    """Resolve group member nickname (group card) via WCDB and contact.db ext_buffer (best-effort)."""
+
+    contact_map: dict[str, str] = {}
+    try:
+        contact_map = _load_group_nickname_map_from_contact_db(
+            contact_db_path,
+            chatroom_id,
+            sender_usernames,
+        )
+    except Exception:
+        contact_map = {}
+
+    wcdb_map: dict[str, str] = {}
+    try:
+        wcdb_map = _load_group_nickname_map_from_wcdb(
+            account_dir=account_dir,
+            chatroom_id=chatroom_id,
+            sender_usernames=sender_usernames,
+            rt_conn=rt_conn,
+        )
+    except Exception:
+        wcdb_map = {}
+
+    if not contact_map and not wcdb_map:
+        return {}
+
+    # Merge: WCDB wins (newer DLLs may provide higher-quality group nicknames).
+    merged: dict[str, str] = {}
+    merged.update(contact_map)
+    merged.update(wcdb_map)
+    return merged
+
+
+def _resolve_sender_display_name(
+    *,
+    sender_username: str,
+    sender_contact_rows: dict[str, sqlite3.Row],
+    wcdb_display_names: dict[str, str],
+    group_nicknames: Optional[dict[str, str]] = None,
+) -> str:
+    su = str(sender_username or "").strip()
+    if not su:
+        return ""
+
+    gn = str((group_nicknames or {}).get(su) or "").strip()
+    if gn:
+        return gn
+
+    row = sender_contact_rows.get(su)
+    display_name = _pick_display_name(row, su)
+    if display_name == su:
+        wd = str(wcdb_display_names.get(su) or "").strip()
+        if wd and wd != su:
+            display_name = wd
+    return display_name
+
+
 def _realtime_sync_lock(account: str, username: str) -> threading.Lock:
     key = (str(account or "").strip(), str(username or "").strip())
     with _REALTIME_SYNC_MU:
@@ -557,8 +701,11 @@ def _upsert_session_table_rows(conn: sqlite3.Connection, rows: list[dict[str, An
         "draft",
         "last_timestamp",
         "sort_timestamp",
+        "last_msg_locald_id",
         "last_msg_type",
         "last_msg_sub_type",
+        "last_msg_sender",
+        "last_sender_display_name",
     ]
     update_cols = [c for c in desired_cols if c in cols]
     if not update_cols:
@@ -583,7 +730,15 @@ def _upsert_session_table_rows(conn: sqlite3.Connection, rows: list[dict[str, An
             continue
         values: list[Any] = []
         for c in update_cols:
-            if c in {"unread_count", "is_hidden", "last_timestamp", "sort_timestamp", "last_msg_type", "last_msg_sub_type"}:
+            if c in {
+                "unread_count",
+                "is_hidden",
+                "last_timestamp",
+                "sort_timestamp",
+                "last_msg_locald_id",
+                "last_msg_type",
+                "last_msg_sub_type",
+            }:
                 values.append(_int((r or {}).get(c)))
             else:
                 values.append(_text((r or {}).get(c)))
@@ -1510,8 +1665,17 @@ def sync_chat_realtime_messages_all(
                     "sort_timestamp",
                     item.get("sortTimestamp", item.get("last_timestamp", item.get("lastTimestamp", 0))),
                 ),
+                "last_msg_locald_id": item.get(
+                    "last_msg_locald_id",
+                    item.get("lastMsgLocaldId", item.get("lastMsgLocalId", 0)),
+                ),
                 "last_msg_type": item.get("last_msg_type", item.get("lastMsgType", 0)),
                 "last_msg_sub_type": item.get("last_msg_sub_type", item.get("lastMsgSubType", 0)),
+                "last_msg_sender": item.get("last_msg_sender", item.get("lastMsgSender", "")),
+                "last_sender_display_name": item.get(
+                    "last_sender_display_name",
+                    item.get("lastSenderDisplayName", ""),
+                ),
             }
             # Prefer the row with the newer sort timestamp for the same username.
             prev = realtime_rows_by_user.get(uname)
@@ -2137,11 +2301,7 @@ def _append_full_messages_from_rows(
 
         if local_type == 10000:
             render_type = "system"
-            if "revokemsg" in raw_text:
-                content_text = "撤回了一条消息"
-            else:
-                content_text = re.sub(r"</?[_a-zA-Z0-9]+[^>]*>", "", raw_text)
-                content_text = re.sub(r"\s+", " ", content_text).strip() or "[系统消息]"
+            content_text = _parse_system_message_content(raw_text)
         elif local_type == 49:
             parsed = _parse_app_message(raw_text)
             render_type = str(parsed.get("renderType") or "text")
@@ -2598,6 +2758,13 @@ def _postprocess_full_messages(
         wcdb_display_names = {}
         wcdb_avatar_urls = {}
 
+    group_nicknames = _load_group_nickname_map(
+        account_dir=account_dir,
+        contact_db_path=contact_db_path,
+        chatroom_id=username,
+        sender_usernames=uniq_senders,
+    )
+
     for m in merged:
         # If appmsg doesn't provide sourcedisplayname, try mapping sourceusername to display name.
         if (not str(m.get("from") or "").strip()) and str(m.get("fromUsername") or "").strip():
@@ -2613,13 +2780,12 @@ def _postprocess_full_messages(
         su = str(m.get("senderUsername") or "")
         if not su:
             continue
-        row = sender_contact_rows.get(su)
-        display_name = _pick_display_name(row, su)
-        if display_name == su:
-            wd = str(wcdb_display_names.get(su) or "").strip()
-            if wd and wd != su:
-                display_name = wd
-        m["senderDisplayName"] = display_name
+        m["senderDisplayName"] = _resolve_sender_display_name(
+            sender_username=su,
+            sender_contact_rows=sender_contact_rows,
+            wcdb_display_names=wcdb_display_names,
+            group_nicknames=group_nicknames,
+        )
         avatar_url = base_url + _avatar_url_unified(
             account_dir=account_dir,
             username=su,
@@ -2836,6 +3002,17 @@ def list_chat_sessions(
                     "sort_timestamp": item.get("sort_timestamp", item.get("sortTimestamp", item.get("last_timestamp", 0))),
                     "last_msg_type": item.get("last_msg_type", item.get("lastMsgType", 0)),
                     "last_msg_sub_type": item.get("last_msg_sub_type", item.get("lastMsgSubType", 0)),
+                    # Keep these fields so group session previews can render "sender: content" without
+                    # crashing (realtime rows are dicts, not sqlite Rows).
+                    "last_msg_sender": item.get("last_msg_sender", item.get("lastMsgSender", "")),
+                    "last_sender_display_name": item.get(
+                        "last_sender_display_name",
+                        item.get("lastSenderDisplayName", ""),
+                    ),
+                    "last_msg_locald_id": item.get(
+                        "last_msg_locald_id",
+                        item.get("lastMsgLocaldId", item.get("lastMsgLocalId", 0)),
+                    ),
                 }
             )
 
@@ -2923,12 +3100,16 @@ def list_chat_sessions(
     try:
         need_display: list[str] = []
         need_avatar: list[str] = []
+        if source_norm == "realtime":
+            # In realtime mode, always ask WCDB for display names: decrypted contact.db can be stale.
+            need_display = [str(u or "").strip() for u in usernames if str(u or "").strip()]
         for u in usernames:
             if not u:
                 continue
-            row = contact_rows.get(u)
-            if _pick_display_name(row, u) == u:
-                need_display.append(u)
+            if source_norm != "realtime":
+                row = contact_rows.get(u)
+                if _pick_display_name(row, u) == u:
+                    need_display.append(u)
             if source_norm == "realtime":
                 # In realtime mode, prefer WCDB-resolved avatar URLs (contact.db can be stale).
                 if u not in local_avatar_usernames:
@@ -2983,14 +3164,40 @@ def list_chat_sessions(
                 if v:
                     last_previews[u] = v
 
+    group_sender_display_names: dict[str, str] = _build_group_sender_display_name_map(
+        contact_db_path,
+        last_previews,
+    )
+    unresolved = []
+    for conv_username, preview_text in last_previews.items():
+        if not str(conv_username or "").endswith("@chatroom"):
+            continue
+        sender_username = _extract_group_preview_sender_username(preview_text)
+        if sender_username and sender_username not in group_sender_display_names:
+            unresolved.append(sender_username)
+    unresolved = list(dict.fromkeys(unresolved))
+    if unresolved:
+        try:
+            wcdb_conn = rt_conn or WCDB_REALTIME.ensure_connected(account_dir)
+            with wcdb_conn.lock:
+                wcdb_names = _wcdb_get_display_names(wcdb_conn.handle, unresolved)
+            for sender_username in unresolved:
+                wcdb_name = str(wcdb_names.get(sender_username) or "").strip()
+                if wcdb_name and wcdb_name != sender_username:
+                    group_sender_display_names[sender_username] = wcdb_name
+        except Exception:
+            pass
+
     sessions: list[dict[str, Any]] = []
     for r in filtered:
         username = r["username"]
         c_row = contact_rows.get(username)
 
         display_name = _pick_display_name(c_row, username)
-        if display_name == username:
-            wd = str(wcdb_display_names.get(username) or "").strip()
+        wd = str(wcdb_display_names.get(username) or "").strip()
+        if source_norm == "realtime" and wd and wd != username:
+            display_name = wd
+        elif display_name == username:
             if wd and wd != username:
                 display_name = wd
 
@@ -3046,6 +3253,37 @@ def list_chat_sessions(
             if last_msg_type == 81604378673 or (last_msg_type == 49 and last_msg_sub_type == 19):
                 last_message = "[聊天记录]"
 
+        last_message = _normalize_session_preview_text(
+            last_message,
+            is_group=bool(str(username or "").endswith("@chatroom")),
+            sender_display_names=group_sender_display_names,
+        )
+        if str(username or "").endswith("@chatroom") and str(last_message or "") and not str(last_message).startswith("[草稿]"):
+            # Prefer group card nickname when available. In realtime mode, WCDB session rows can provide
+            # `last_sender_display_name`, but we may still get a summary that doesn't include "sender:".
+            # Also guard against URL schemes like "https://..." being mis-parsed as "https: //...".
+            raw_sender_display = ""
+            try:
+                raw_sender_display = r["last_sender_display_name"]
+            except Exception:
+                try:
+                    raw_sender_display = r.get("last_sender_display_name", "")
+                except Exception:
+                    raw_sender_display = ""
+            sender_display = _decode_sqlite_text(raw_sender_display).strip()
+            if sender_display:
+                text = re.sub(r"\s+", " ", str(last_message or "").strip()).strip()
+                match = re.match(r"^([^:\n]{1,128}):\s*(.+)$", text)
+                if match:
+                    prefix = str(match.group(1) or "").strip()
+                    body = re.sub(r"\s+", " ", str(match.group(2) or "").strip()).strip()
+                    if prefix.lower() in {"http", "https"} and body.startswith("//"):
+                        last_message = f"{sender_display}: {text}"
+                    else:
+                        last_message = f"{sender_display}: {body}"
+                else:
+                    last_message = f"{sender_display}: {text}"
+
         last_time = _format_session_time(r["sort_timestamp"] or r["last_timestamp"])
 
         sessions.append(
@@ -3248,13 +3486,7 @@ def _collect_chat_messages(
 
                 if local_type == 10000:
                     render_type = "system"
-                    if "revokemsg" in raw_text:
-                        content_text = "撤回了一条消息"
-                    else:
-                        import re
-
-                        content_text = re.sub(r"</?[_a-zA-Z0-9]+[^>]*>", "", raw_text)
-                        content_text = re.sub(r"\s+", " ", content_text).strip() or "[系统消息]"
+                    content_text = _parse_system_message_content(raw_text)
                 elif local_type == 49:
                     parsed = _parse_app_message(raw_text)
                     render_type = str(parsed.get("renderType") or "text")
@@ -3957,13 +4189,7 @@ def list_chat_messages(
 
                 if local_type == 10000:
                     render_type = "system"
-                    if "revokemsg" in raw_text:
-                        content_text = "撤回了一条消息"
-                    else:
-                        import re
-
-                        content_text = re.sub(r"</?[_a-zA-Z0-9]+[^>]*>", "", raw_text)
-                        content_text = re.sub(r"\s+", " ", content_text).strip() or "[系统消息]"
+                    content_text = _parse_system_message_content(raw_text)
                 elif local_type == 49:
                     parsed = _parse_app_message(raw_text)
                     render_type = str(parsed.get("renderType") or "text")
@@ -4412,6 +4638,13 @@ def list_chat_messages(
         wcdb_display_names = {}
         wcdb_avatar_urls = {}
 
+    group_nicknames = _load_group_nickname_map(
+        account_dir=account_dir,
+        contact_db_path=contact_db_path,
+        chatroom_id=username,
+        sender_usernames=uniq_senders,
+    )
+
     for m in merged:
         # If appmsg doesn't provide sourcedisplayname, try mapping sourceusername to display name.
         if (not str(m.get("from") or "").strip()) and str(m.get("fromUsername") or "").strip():
@@ -4427,13 +4660,12 @@ def list_chat_messages(
         su = str(m.get("senderUsername") or "")
         if not su:
             continue
-        row = sender_contact_rows.get(su)
-        display_name = _pick_display_name(row, su)
-        if display_name == su:
-            wd = str(wcdb_display_names.get(su) or "").strip()
-            if wd and wd != su:
-                display_name = wd
-        m["senderDisplayName"] = display_name
+        m["senderDisplayName"] = _resolve_sender_display_name(
+            sender_username=su,
+            sender_contact_rows=sender_contact_rows,
+            wcdb_display_names=wcdb_display_names,
+            group_nicknames=group_nicknames,
+        )
         avatar_url = base_url + _avatar_url_unified(
             account_dir=account_dir,
             username=su,
@@ -4930,19 +5162,24 @@ async def _search_chat_messages_via_fts(
             username=username,
             local_avatar_usernames=local_avatar_usernames,
         )
+        group_nicknames = _load_group_nickname_map(
+            account_dir=account_dir,
+            contact_db_path=contact_db_path,
+            chatroom_id=username,
+            sender_usernames=[str(x.get("senderUsername") or "") for x in hits],
+        )
 
         for h in hits:
             su = str(h.get("senderUsername") or "").strip()
             h["conversationName"] = conv_name
             h["conversationAvatar"] = conv_avatar
             if su:
-                row = contact_rows.get(su)
-                display_name = _pick_display_name(row, su) if row is not None else (conv_name if su == username else su)
-                if display_name == su:
-                    wd = str(wcdb_display_names.get(su) or "").strip()
-                    if wd and wd != su:
-                        display_name = wd
-                h["senderDisplayName"] = display_name
+                h["senderDisplayName"] = _resolve_sender_display_name(
+                    sender_username=su,
+                    sender_contact_rows=contact_rows,
+                    wcdb_display_names=wcdb_display_names,
+                    group_nicknames=group_nicknames,
+                )
                 avatar_url = base_url + _avatar_url_unified(
                     account_dir=account_dir,
                     username=su,
@@ -4986,6 +5223,23 @@ async def _search_chat_messages_via_fts(
             wcdb_display_names = {}
             wcdb_avatar_urls = {}
 
+        group_senders_by_room: dict[str, list[str]] = {}
+        for h in hits:
+            cu = str(h.get("username") or "").strip()
+            su = str(h.get("senderUsername") or "").strip()
+            if (not cu.endswith("@chatroom")) or (not su):
+                continue
+            group_senders_by_room.setdefault(cu, []).append(su)
+
+        group_nickname_cache: dict[str, dict[str, str]] = {}
+        for cu, senders in group_senders_by_room.items():
+            group_nickname_cache[cu] = _load_group_nickname_map(
+                account_dir=account_dir,
+                contact_db_path=contact_db_path,
+                chatroom_id=cu,
+                sender_usernames=senders,
+            )
+
         for h in hits:
             cu = str(h.get("username") or "").strip()
             su = str(h.get("senderUsername") or "").strip()
@@ -5003,13 +5257,12 @@ async def _search_chat_messages_via_fts(
             )
             h["conversationAvatar"] = conv_avatar
             if su:
-                row = contact_rows.get(su)
-                display_name = _pick_display_name(row, su) if row is not None else (conv_name if su == cu else su)
-                if display_name == su:
-                    wd = str(wcdb_display_names.get(su) or "").strip()
-                    if wd and wd != su:
-                        display_name = wd
-                h["senderDisplayName"] = display_name
+                h["senderDisplayName"] = _resolve_sender_display_name(
+                    sender_username=su,
+                    sender_contact_rows=contact_rows,
+                    wcdb_display_names=wcdb_display_names,
+                    group_nicknames=group_nickname_cache.get(cu, {}),
+                )
                 avatar_url = base_url + _avatar_url_unified(
                     account_dir=account_dir,
                     username=su,
@@ -5272,13 +5525,23 @@ async def search_chat_messages(
         contact_rows = _load_contact_rows(contact_db_path, uniq_usernames)
         conv_row = contact_rows.get(username)
         conv_name = _pick_display_name(conv_row, username)
+        group_nicknames = _load_group_nickname_map(
+            account_dir=account_dir,
+            contact_db_path=contact_db_path,
+            chatroom_id=username,
+            sender_usernames=[str(x.get("senderUsername") or "") for x in page],
+        )
 
         for h in page:
             su = str(h.get("senderUsername") or "").strip()
             h["conversationName"] = conv_name
             if su:
-                row = contact_rows.get(su)
-                h["senderDisplayName"] = _pick_display_name(row, su) if row is not None else (conv_name if su == username else su)
+                h["senderDisplayName"] = _resolve_sender_display_name(
+                    sender_username=su,
+                    sender_contact_rows=contact_rows,
+                    wcdb_display_names={},
+                    group_nicknames=group_nicknames,
+                )
 
         return {
             "status": "success",
@@ -5360,6 +5623,23 @@ async def search_chat_messages(
     )
     contact_rows = _load_contact_rows(contact_db_path, uniq_contacts)
 
+    group_senders_by_room: dict[str, list[str]] = {}
+    for h in page:
+        cu = str(h.get("username") or "").strip()
+        su = str(h.get("senderUsername") or "").strip()
+        if (not cu.endswith("@chatroom")) or (not su):
+            continue
+        group_senders_by_room.setdefault(cu, []).append(su)
+
+    group_nickname_cache: dict[str, dict[str, str]] = {}
+    for cu, senders in group_senders_by_room.items():
+        group_nickname_cache[cu] = _load_group_nickname_map(
+            account_dir=account_dir,
+            contact_db_path=contact_db_path,
+            chatroom_id=cu,
+            sender_usernames=senders,
+        )
+
     for h in page:
         cu = str(h.get("username") or "").strip()
         su = str(h.get("senderUsername") or "").strip()
@@ -5367,8 +5647,12 @@ async def search_chat_messages(
         conv_name = _pick_display_name(crow, cu) if cu else ""
         h["conversationName"] = conv_name or cu
         if su:
-            row = contact_rows.get(su)
-            h["senderDisplayName"] = _pick_display_name(row, su) if row is not None else (conv_name if su == cu else su)
+            h["senderDisplayName"] = _resolve_sender_display_name(
+                sender_username=su,
+                sender_contact_rows=contact_rows,
+                wcdb_display_names={},
+                group_nicknames=group_nickname_cache.get(cu, {}),
+            )
 
     return {
         "status": "success",

src/wechat_decrypt_tool/routers/chat_media.py

@@ -688,6 +688,83 @@ def _lookup_resource_md5_by_server_id(account_dir_str: str, server_id: int, want
             pass
 
 
+@lru_cache(maxsize=4096)
+def _lookup_image_md5_by_server_id_from_messages(account_dir_str: str, server_id: int, username: str) -> str:
+    account_dir_str = str(account_dir_str or "").strip()
+    username = str(username or "").strip()
+    if not account_dir_str or not username:
+        return ""
+
+    try:
+        sid = int(server_id or 0)
+    except Exception:
+        sid = 0
+    if not sid:
+        return ""
+
+    try:
+        chat_hash = hashlib.md5(username.encode()).hexdigest()
+    except Exception:
+        return ""
+    if not chat_hash:
+        return ""
+
+    table_name = f"Msg_{chat_hash}"
+    account_dir = Path(account_dir_str)
+
+    db_paths: list[Path] = []
+    try:
+        for p in account_dir.glob("message_*.db"):
+            try:
+                if p.is_file():
+                    db_paths.append(p)
+            except Exception:
+                continue
+    except Exception:
+        db_paths = []
+
+    if not db_paths:
+        return ""
+    db_paths.sort(key=lambda p: p.name)
+
+    for db_path in db_paths:
+        try:
+            conn = sqlite3.connect(str(db_path))
+        except Exception:
+            continue
+
+        try:
+            row = conn.execute(
+                f"SELECT local_type, packed_info_data FROM {table_name} "
+                "WHERE server_id = ? ORDER BY create_time DESC LIMIT 1",
+                (sid,),
+            ).fetchone()
+        except Exception:
+            row = None
+        finally:
+            try:
+                conn.close()
+            except Exception:
+                pass
+
+        if not row:
+            continue
+
+        try:
+            local_type = int(row[0] or 0)
+        except Exception:
+            local_type = 0
+        if local_type != 3:
+            continue
+
+        md5 = _extract_md5_from_packed_info(row[1])
+        md5_norm = str(md5 or "").strip().lower()
+        if _is_valid_md5(md5_norm):
+            return md5_norm
+
+    return ""
+
+
 def _is_safe_http_url(url: str) -> bool:
     u = str(url or "").strip()
     if not u:
@@ -1062,6 +1139,12 @@ async def get_chat_image(
         resource_md5 = _lookup_resource_md5_by_server_id(str(account_dir), int(server_id), want_local_type=3)
         if resource_md5:
             md5 = resource_md5
+        elif username:
+            md5_from_msg = _lookup_image_md5_by_server_id_from_messages(
+                str(account_dir), int(server_id), str(username)
+            )
+            if md5_from_msg:
+                md5 = md5_from_msg
 
     # md5 模式：优先从解密资源目录读取（更快）
     if md5:

src/wechat_decrypt_tool/wcdb_realtime.py

@@ -102,6 +102,17 @@ def _load_wcdb_lib() -> ctypes.CDLL:
         lib.wcdb_get_group_members.argtypes = [ctypes.c_int64, ctypes.c_char_p, ctypes.POINTER(ctypes.c_char_p)]
         lib.wcdb_get_group_members.restype = ctypes.c_int
 
+        # Optional (newer DLLs): wcdb_get_group_nicknames(handle, chatroom_id, out_json)
+        try:
+            lib.wcdb_get_group_nicknames.argtypes = [
+                ctypes.c_int64,
+                ctypes.c_char_p,
+                ctypes.POINTER(ctypes.c_char_p),
+            ]
+            lib.wcdb_get_group_nicknames.restype = ctypes.c_int
+        except Exception:
+            pass
+
         # Optional: execute arbitrary SQL on a selected database kind/path.
         # Signature: wcdb_exec_query(handle, kind, path, sql, out_json)
         try:
@@ -355,6 +366,41 @@ def get_avatar_urls(handle: int, usernames: list[str]) -> dict[str, str]:
     return {}
 
 
+def get_group_members(handle: int, chatroom_id: str) -> list[dict[str, Any]]:
+    _ensure_initialized()
+    lib = _load_wcdb_lib()
+    cid = str(chatroom_id or "").strip()
+    if not cid:
+        return []
+    out_json = _call_out_json(lib.wcdb_get_group_members, ctypes.c_int64(int(handle)), cid.encode("utf-8"))
+    decoded = _safe_load_json(out_json)
+    if isinstance(decoded, list):
+        out: list[dict[str, Any]] = []
+        for x in decoded:
+            if isinstance(x, dict):
+                out.append(x)
+        return out
+    return []
+
+
+def get_group_nicknames(handle: int, chatroom_id: str) -> dict[str, str]:
+    _ensure_initialized()
+    lib = _load_wcdb_lib()
+    fn = getattr(lib, "wcdb_get_group_nicknames", None)
+    if not fn:
+        return {}
+
+    cid = str(chatroom_id or "").strip()
+    if not cid:
+        return {}
+
+    out_json = _call_out_json(fn, ctypes.c_int64(int(handle)), cid.encode("utf-8"))
+    decoded = _safe_load_json(out_json)
+    if isinstance(decoded, dict):
+        return {str(k): str(v) for k, v in decoded.items()}
+    return {}
+
+
 def exec_query(handle: int, *, kind: str, path: Optional[str], sql: str) -> list[dict[str, Any]]:
     """Execute raw SQL on a specific db kind/path via WCDB.
 

tests/test_chat_export_message_types_semantics.py

@@ -122,6 +122,16 @@ class TestChatExportMessageTypesSemantics(unittest.TestCase):
                 (3, 1003, 49, 3, 2, 1735689603, '<msg><appmsg><type>2000</type><des>收到转账0.01元</des></appmsg></msg>', None),
                 (4, 1004, 1, 4, 2, 1735689604, '普通文本消息', None),
                 (5, 1005, 10000, 5, 2, 1735689605, '系统提示消息', None),
+                (
+                    6,
+                    1006,
+                    10000,
+                    6,
+                    2,
+                    1735689606,
+                    '<sysmsg type="revokemsg"><revokemsg><replacemsg><![CDATA[“测试好友”撤回了一条消息]]></replacemsg></revokemsg></sysmsg>',
+                    None,
+                ),
             ]
             conn.executemany(
                 f"INSERT INTO {table_name} (local_id, server_id, local_type, sort_seq, real_sender_id, create_time, message_content, compress_content) VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
@@ -413,6 +423,37 @@ class TestChatExportMessageTypesSemantics(unittest.TestCase):
                 else:
                     os.environ["WECHAT_TOOL_DATA_DIR"] = prev_data
 
+    def test_system_revoke_exports_readable_revoker_content(self):
+        with TemporaryDirectory() as td:
+            root = Path(td)
+            account = "wxid_test"
+            username = "wxid_friend"
+            self._prepare_account(root, account=account, username=username)
+
+            prev_data = os.environ.get("WECHAT_TOOL_DATA_DIR")
+            try:
+                os.environ["WECHAT_TOOL_DATA_DIR"] = str(root)
+                svc = self._reload_export_modules()
+                job = self._create_job(
+                    svc.CHAT_EXPORT_MANAGER,
+                    account=account,
+                    username=username,
+                    message_types=["system"],
+                    include_media=False,
+                )
+                self.assertEqual(job.status, "done", msg=job.error)
+
+                payload, _, _ = self._load_export_payload(job.zip_path)
+                revoke_msg = next((m for m in payload.get("messages", []) if int(m.get("serverId") or 0) == 1006), None)
+                self.assertIsNotNone(revoke_msg)
+                self.assertEqual(str(revoke_msg.get("renderType") or ""), "system")
+                self.assertEqual(str(revoke_msg.get("content") or ""), "“测试好友”撤回了一条消息")
+            finally:
+                if prev_data is None:
+                    os.environ.pop("WECHAT_TOOL_DATA_DIR", None)
+                else:
+                    os.environ["WECHAT_TOOL_DATA_DIR"] = prev_data
+
 
 if __name__ == "__main__":
     unittest.main()

tests/test_chat_realtime_sync_all_updates_sender_display_name.py

@@ -0,0 +1,111 @@
+import sqlite3
+import sys
+import threading
+import unittest
+from pathlib import Path
+from tempfile import TemporaryDirectory
+from unittest.mock import patch
+
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / "src"))
+
+from wechat_decrypt_tool.routers import chat as chat_router
+
+
+class _DummyRequest:
+    base_url = "http://testserver/"
+
+
+class _DummyConn:
+    def __init__(self) -> None:
+        self.handle = 1
+        self.lock = threading.Lock()
+
+
+def _seed_session_db(session_db_path: Path) -> None:
+    conn = sqlite3.connect(str(session_db_path))
+    try:
+        conn.execute(
+            """
+            CREATE TABLE SessionTable (
+                username TEXT PRIMARY KEY,
+                unread_count INTEGER DEFAULT 0,
+                is_hidden INTEGER DEFAULT 0,
+                summary TEXT DEFAULT '',
+                draft TEXT DEFAULT '',
+                last_timestamp INTEGER DEFAULT 0,
+                sort_timestamp INTEGER DEFAULT 0,
+                last_msg_locald_id INTEGER DEFAULT 0,
+                last_msg_type INTEGER DEFAULT 0,
+                last_msg_sub_type INTEGER DEFAULT 0,
+                last_msg_sender TEXT DEFAULT '',
+                last_sender_display_name TEXT DEFAULT ''
+            )
+            """
+        )
+        conn.commit()
+    finally:
+        conn.close()
+
+
+class TestChatRealtimeSyncAllUpdatesSenderDisplayName(unittest.TestCase):
+    def test_sync_all_upserts_last_sender_display_name(self):
+        with TemporaryDirectory() as td:
+            account_dir = Path(td) / "acc"
+            account_dir.mkdir(parents=True, exist_ok=True)
+            _seed_session_db(account_dir / "session.db")
+
+            conn = _DummyConn()
+            sessions_rows = [
+                {
+                    "username": "demo@chatroom",
+                    "unread_count": 0,
+                    "is_hidden": 0,
+                    "summary": "hello",
+                    "draft": "",
+                    "last_timestamp": 123,
+                    "sort_timestamp": 123,
+                    "last_msg_type": 1,
+                    "last_msg_sub_type": 0,
+                    "last_msg_sender": "wxid_demo",
+                    "last_sender_display_name": "群名片A",
+                    "last_msg_locald_id": 777,
+                }
+            ]
+
+            with (
+                patch.object(chat_router, "_resolve_account_dir", return_value=account_dir),
+                patch.object(chat_router.WCDB_REALTIME, "ensure_connected", return_value=conn),
+                patch.object(chat_router, "_wcdb_get_sessions", return_value=sessions_rows),
+                patch.object(chat_router, "_ensure_decrypted_message_tables", return_value={}),
+                patch.object(chat_router, "_should_keep_session", return_value=True),
+            ):
+                resp = chat_router.sync_chat_realtime_messages_all(
+                    _DummyRequest(),
+                    account="acc",
+                    max_scan=20,
+                    include_hidden=True,
+                    include_official=True,
+                )
+
+            self.assertEqual(resp.get("status"), "success")
+
+            db = sqlite3.connect(str(account_dir / "session.db"))
+            try:
+                row = db.execute(
+                    "SELECT last_sender_display_name, last_msg_sender, last_msg_locald_id FROM SessionTable WHERE username = ? LIMIT 1",
+                    ("demo@chatroom",),
+                ).fetchone()
+            finally:
+                db.close()
+
+            self.assertIsNotNone(row)
+            self.assertEqual(str(row[0] or ""), "群名片A")
+            self.assertEqual(str(row[1] or ""), "wxid_demo")
+            self.assertEqual(int(row[2] or 0), 777)
+
+
+if __name__ == "__main__":
+    unittest.main()
+

tests/test_chat_session_preview_formatting.py

@@ -0,0 +1,68 @@
+import sqlite3
+import sys
+import unittest
+from pathlib import Path
+from tempfile import TemporaryDirectory
+
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / "src"))
+
+from wechat_decrypt_tool.chat_helpers import (
+    _build_group_sender_display_name_map,
+    _normalize_session_preview_text,
+    _replace_preview_sender_prefix,
+)
+
+
+class TestChatSessionPreviewFormatting(unittest.TestCase):
+    def test_normalize_session_preview_emoji_label(self):
+        out = _normalize_session_preview_text("[表情]", is_group=False, sender_display_names={})
+        self.assertEqual(out, "[动画表情]")
+
+    def test_normalize_group_preview_sender_display_name(self):
+        out = _normalize_session_preview_text(
+            "wxid_u3gwceqvne2m22: [表情]",
+            is_group=True,
+            sender_display_names={"wxid_u3gwceqvne2m22": "食神"},
+        )
+        self.assertEqual(out, "食神: [动画表情]")
+
+    def test_build_group_sender_display_name_map_from_contact_db(self):
+        with TemporaryDirectory() as td:
+            contact_db_path = Path(td) / "contact.db"
+            conn = sqlite3.connect(str(contact_db_path))
+            try:
+                conn.execute(
+                    """
+                    CREATE TABLE contact (
+                        username TEXT,
+                        remark TEXT,
+                        nick_name TEXT,
+                        alias TEXT,
+                        big_head_url TEXT,
+                        small_head_url TEXT
+                    )
+                    """
+                )
+                conn.execute(
+                    "INSERT INTO contact VALUES (?, ?, ?, ?, ?, ?)",
+                    ("wxid_u3gwceqvne2m22", "", "食神", "", "", ""),
+                )
+                conn.commit()
+            finally:
+                conn.close()
+
+            mapping = _build_group_sender_display_name_map(
+                contact_db_path,
+                {"demo@chatroom": "wxid_u3gwceqvne2m22: [动画表情]"},
+            )
+            self.assertEqual(mapping.get("wxid_u3gwceqvne2m22"), "食神")
+
+    def test_replace_preview_sender_prefix_uses_group_nickname(self):
+        out = _replace_preview_sender_prefix("去码头整点🍟: [动画表情]", "麻辣香锅")
+        self.assertEqual(out, "麻辣香锅: [动画表情]")
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_chat_sessions_realtime_sender_preview.py

@@ -0,0 +1,103 @@
+import sys
+import threading
+import unittest
+from pathlib import Path
+from tempfile import TemporaryDirectory
+from unittest.mock import patch
+
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / "src"))
+
+
+from wechat_decrypt_tool.routers import chat as chat_router
+
+
+class _DummyRequest:
+    base_url = "http://testserver/"
+
+
+class _DummyConn:
+    def __init__(self) -> None:
+        self.handle = 1
+        self.lock = threading.Lock()
+
+
+class TestChatSessionsRealtimeSenderPreview(unittest.TestCase):
+    def _run(self, sessions_rows: list[dict]) -> dict:
+        with TemporaryDirectory() as td:
+            account_dir = Path(td) / "acc"
+            account_dir.mkdir(parents=True, exist_ok=True)
+
+            conn = _DummyConn()
+            with (
+                patch.object(chat_router, "_resolve_account_dir", return_value=account_dir),
+                patch.object(chat_router.WCDB_REALTIME, "ensure_connected", return_value=conn),
+                patch.object(chat_router, "_wcdb_get_sessions", return_value=sessions_rows),
+                patch.object(chat_router, "_wcdb_get_display_names", return_value={}),
+                patch.object(chat_router, "_wcdb_get_avatar_urls", return_value={}),
+                patch.object(chat_router, "_load_contact_rows", return_value={}),
+                patch.object(chat_router, "_query_head_image_usernames", return_value=set()),
+                patch.object(chat_router, "_should_keep_session", return_value=True),
+                patch.object(chat_router, "_avatar_url_unified", return_value="/avatar"),
+            ):
+                return chat_router.list_chat_sessions(
+                    _DummyRequest(),
+                    account="acc",
+                    limit=50,
+                    include_hidden=True,
+                    include_official=True,
+                    preview="latest",
+                    source="realtime",
+                )
+
+    def test_realtime_sessions_group_summary_prefixed_by_sender_display_name(self):
+        resp = self._run(
+            [
+                {
+                    "username": "demo@chatroom",
+                    "summary": "hello",
+                    "draft": "",
+                    "unread_count": 0,
+                    "is_hidden": 0,
+                    "last_timestamp": 123,
+                    "sort_timestamp": 123,
+                    "last_msg_type": 1,
+                    "last_msg_sub_type": 0,
+                    "last_msg_sender": "wxid_demo",
+                    "last_sender_display_name": "群名片A",
+                }
+            ]
+        )
+        self.assertEqual(resp.get("status"), "success")
+        sessions = resp.get("sessions") or []
+        self.assertEqual(len(sessions), 1)
+        self.assertEqual(sessions[0].get("lastMessage"), "群名片A: hello")
+
+    def test_realtime_sessions_group_url_summary_keeps_scheme(self):
+        resp = self._run(
+            [
+                {
+                    "username": "url@chatroom",
+                    "summary": "https://example.com/x",
+                    "draft": "",
+                    "unread_count": 0,
+                    "is_hidden": 0,
+                    "last_timestamp": 123,
+                    "sort_timestamp": 123,
+                    "last_msg_type": 1,
+                    "last_msg_sub_type": 0,
+                    "last_msg_sender": "wxid_demo",
+                    "last_sender_display_name": "群名片B",
+                }
+            ]
+        )
+        self.assertEqual(resp.get("status"), "success")
+        sessions = resp.get("sessions") or []
+        self.assertEqual(len(sessions), 1)
+        self.assertEqual(sessions[0].get("lastMessage"), "群名片B: https://example.com/x")
+
+
+if __name__ == "__main__":
+    unittest.main()
+

tests/test_chat_system_message_parsing.py

@@ -0,0 +1,42 @@
+import sys
+import unittest
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / "src"))
+
+from wechat_decrypt_tool.chat_helpers import _parse_system_message_content
+
+
+class TestChatSystemMessageParsing(unittest.TestCase):
+    def test_extract_replacemsg_for_revoke(self):
+        raw_text = (
+            '<sysmsg type="revokemsg"><revokemsg><replacemsg><![CDATA[“张三”撤回了一条消息]]>'
+            "</replacemsg></revokemsg></sysmsg>"
+        )
+        self.assertEqual(_parse_system_message_content(raw_text), "“张三”撤回了一条消息")
+
+    def test_extract_nested_content_in_replacemsg(self):
+        raw_text = (
+            '<sysmsg type="revokemsg"><revokemsg><replacemsg><![CDATA['
+            '<content>"黄智欢" 撤回了一条消息</content><revoketime>0</revoketime>'
+            ']]></replacemsg></revokemsg></sysmsg>'
+        )
+        self.assertEqual(_parse_system_message_content(raw_text), '"黄智欢" 撤回了一条消息')
+
+    def test_extract_revokemsg_text_when_replacemsg_missing(self):
+        raw_text = "<revokemsg>你撤回了一条消息</revokemsg>"
+        self.assertEqual(_parse_system_message_content(raw_text), "你撤回了一条消息")
+
+    def test_revoke_fallback_when_no_readable_text(self):
+        raw_text = '<sysmsg type="revokemsg"></sysmsg>'
+        self.assertEqual(_parse_system_message_content(raw_text), "撤回了一条消息")
+
+    def test_normal_system_message_still_cleaned(self):
+        raw_text = "<sysmsg><template><![CDATA[ 张三  加入了群聊 ]]></template></sysmsg>"
+        self.assertEqual(_parse_system_message_content(raw_text), "张三 加入了群聊")
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_group_nickname_ext_buffer_parsing.py

@@ -0,0 +1,114 @@
+import sqlite3
+import sys
+import unittest
+from pathlib import Path
+from tempfile import TemporaryDirectory
+
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / "src"))
+
+from wechat_decrypt_tool.chat_helpers import _load_group_nickname_map_from_contact_db
+
+
+def _enc_varint(n: int) -> bytes:
+    v = int(n)
+    out = bytearray()
+    while True:
+        b = v & 0x7F
+        v >>= 7
+        if v:
+            out.append(b | 0x80)
+        else:
+            out.append(b)
+            break
+    return bytes(out)
+
+
+def _enc_tag(field_no: int, wire_type: int) -> bytes:
+    return _enc_varint((int(field_no) << 3) | int(wire_type))
+
+
+def _enc_len(field_no: int, data: bytes) -> bytes:
+    b = bytes(data or b"")
+    return _enc_tag(field_no, 2) + _enc_varint(len(b)) + b
+
+
+def _member_entry(*, inner: bytes) -> bytes:
+    # contact.db ext_buffer uses repeated length-delimited submessages; the top-level field number is not important
+    # for our best-effort parser, so we use field 1.
+    return _enc_len(1, inner)
+
+
+class TestGroupNicknameExtBufferParsing(unittest.TestCase):
+    def test_parse_pattern_a_field1_username_field2_display(self):
+        chatroom = "demo@chatroom"
+        username = "wxid_demo_123456"
+        display = "群名片A"
+
+        inner = _enc_len(1, username.encode("utf-8")) + _enc_len(2, display.encode("utf-8"))
+        ext_buffer = _member_entry(inner=inner)
+
+        with TemporaryDirectory() as td:
+            contact_db_path = Path(td) / "contact.db"
+            conn = sqlite3.connect(str(contact_db_path))
+            try:
+                conn.execute(
+                    "CREATE TABLE chat_room(id INTEGER PRIMARY KEY, username TEXT, owner TEXT, ext_buffer BLOB)"
+                )
+                conn.execute(
+                    "INSERT INTO chat_room(id, username, owner, ext_buffer) VALUES (?, ?, ?, ?)",
+                    (1, chatroom, "", ext_buffer),
+                )
+                conn.commit()
+            finally:
+                conn.close()
+
+            out = _load_group_nickname_map_from_contact_db(contact_db_path, chatroom, [username])
+            self.assertEqual(out.get(username), display)
+
+    def test_parse_pattern_b_field4_username_field1_display(self):
+        chatroom = "demo2@chatroom"
+        username = "wxid_demo_abcdef"
+        display = "hjlbingo"
+
+        inner = _enc_len(4, username.encode("utf-8")) + _enc_len(1, display.encode("utf-8"))
+        ext_buffer = _member_entry(inner=inner)
+
+        with TemporaryDirectory() as td:
+            contact_db_path = Path(td) / "contact.db"
+            conn = sqlite3.connect(str(contact_db_path))
+            try:
+                conn.execute(
+                    "CREATE TABLE chat_room(id INTEGER PRIMARY KEY, username TEXT, owner TEXT, ext_buffer BLOB)"
+                )
+                conn.execute(
+                    "INSERT INTO chat_room(id, username, owner, ext_buffer) VALUES (?, ?, ?, ?)",
+                    (1, chatroom, "", ext_buffer),
+                )
+                conn.commit()
+            finally:
+                conn.close()
+
+            out = _load_group_nickname_map_from_contact_db(contact_db_path, chatroom, [username])
+            self.assertEqual(out.get(username), display)
+
+    def test_non_chatroom_returns_empty(self):
+        with TemporaryDirectory() as td:
+            contact_db_path = Path(td) / "contact.db"
+            conn = sqlite3.connect(str(contact_db_path))
+            try:
+                conn.execute(
+                    "CREATE TABLE chat_room(id INTEGER PRIMARY KEY, username TEXT, owner TEXT, ext_buffer BLOB)"
+                )
+                conn.commit()
+            finally:
+                conn.close()
+
+            out = _load_group_nickname_map_from_contact_db(contact_db_path, "wxid_not_chatroom", ["wxid_xxx"])
+            self.assertEqual(out, {})
+
+
+if __name__ == "__main__":
+    unittest.main()
+