diff --git a/resources/wcdb/win32/x64/wcdb_api.dll b/resources/wcdb/win32/x64/wcdb_api.dll
index 07b4313..530f6ed 100644
Binary files a/resources/wcdb/win32/x64/wcdb_api.dll and b/resources/wcdb/win32/x64/wcdb_api.dll differ
diff --git a/src/main/services/chat-service.ts b/src/main/services/chat-service.ts
index 413f7b9..48adb79 100644
--- a/src/main/services/chat-service.ts
+++ b/src/main/services/chat-service.ts
@@ -86,6 +86,7 @@ export interface FormattedMessage {
 export interface GroupSnapshot {
   roomId: string
   memberCount: number
+  groupName?: string
   members: {
     wxid: string
     nickname: string
@@ -96,6 +97,15 @@ export interface GroupSnapshot {
   }[]
 }
 
+export interface GroupMembershipSnapshot {
+  roomId: string
+  memberIds: string[]
+}
+
+export interface GroupMembershipBatchSnapshot extends GroupMembershipSnapshot {
+  status: 'ok' | 'not_found'
+}
+
 const MSG_TYPE_DICT: Record<number, string> = {
   1: '普通文本',
   3: '图片',
@@ -236,6 +246,19 @@ export async function listContactsAsync(filter?: string): Promise<FormattedConta
   return listContacts(filter)
 }
 
+/** 读取已缓存/轻量 Session 群名，不执行成员、头像或联系人资料 hydration。 */
+export async function getGroupNamesAsync(): Promise<Record<string, string>> {
+  if (!dbRef) return {}
+  const sessions = await dbRef.getWcdb4Client().getSessionsAsync({ hydrateDisplayNames: false })
+  const names: Record<string, string> = {}
+  for (const session of sessions) {
+    if (!session.username.endsWith('@chatroom')) continue
+    const name = String(session.nickname || '').trim()
+    if (name) names[session.username] = name
+  }
+  return names
+}
+
 export async function getContactAvatars(usernames: string[]): Promise<Record<string, string>> {
   if (!dbRef) return {}
   const normalized = Array.from(
@@ -615,7 +638,40 @@ export async function getGroupSnapshotAsync(userMd5: string): Promise<GroupSnaps
       remark: member.remark || '',
       avatar: member.m_nsHeadImgUrl || ''
     }))
-  return { roomId, memberCount: members.length, members }
+  const session = wcdb4Client.getSessions().find((item) => item.username === roomId)
+  return {
+    roomId,
+    groupName: session?.nickname || undefined,
+    memberCount: members.length,
+    members
+  }
+}
+
+/** 退群检测专用轻量读取，不执行成员名称或头像 hydration。 */
+export async function getGroupMemberIdsAsync(
+  roomId: string
+): Promise<GroupMembershipSnapshot | null> {
+  if (!dbRef || !roomId.endsWith('@chatroom')) return null
+  const memberIds = await dbRef.getWcdb4Client().getGroupMemberIdsAsync(roomId)
+  return memberIds ? { roomId, memberIds } : null
+}
+
+export function isGroupMemberIdsBatchAvailable(): boolean {
+  return Boolean(dbRef?.getWcdb4Client().isGroupMemberIdsBatchAvailable())
+}
+
+export async function getGroupMemberIdsBatchAsync(
+  roomIds: string[]
+): Promise<GroupMembershipBatchSnapshot[] | null> {
+  if (!dbRef) return null
+  const results = await dbRef.getWcdb4Client().getGroupMemberIdsBatchAsync(roomIds)
+  return results
+    ? results.map((result) => ({
+        roomId: result.roomId,
+        status: result.status,
+        memberIds: result.memberWxids
+      }))
+    : null
 }
 
 export function searchMessages(keyword: string): string | null {
diff --git a/src/main/services/group-exit-monitor-service.ts b/src/main/services/group-exit-monitor-service.ts
index bfe44b4..06f4898 100644
--- a/src/main/services/group-exit-monitor-service.ts
+++ b/src/main/services/group-exit-monitor-service.ts
@@ -24,19 +24,37 @@ type StoredState = {
   monitoredRoomIds?: string[]
   notificationRoomIds?: string[]
   notificationTemplate?: unknown
+  snapshots?: Partial<StoredGroupSnapshot>[]
 }
 
 type GroupSnapshotRecord = {
   contactId: string
   roomId: string
   groupName: string
+  capturedAt: number
   members: GroupExitMonitorMember[]
   /** 查询失败时保留旧快照。 */
   membersValid?: boolean
 }
 
+type GroupMembershipRecord = Omit<GroupSnapshotRecord, 'members'> & {
+  memberIds: string[]
+}
+
+type MembershipMode = 'batch' | 'legacy'
+
+type MembershipReadResult = {
+  mode: MembershipMode
+  groupCount: number
+  groups: GroupMembershipRecord[] | null
+}
+
+type StoredGroupSnapshot = Pick<
+  GroupSnapshotRecord,
+  'contactId' | 'roomId' | 'groupName' | 'capturedAt' | 'members'
+>
+
 const DB_CHANGE_DEBOUNCE_MS = 350
-const GROUP_READ_CONCURRENCY = 8
 const DUPLICATE_WINDOW_MS = 2 * 60 * 1000
 const MAX_EVENTS = 500
 
@@ -58,6 +76,10 @@ class GroupExitMonitorService {
   private checking = false
   private checkQueued = false
   private initializing = false
+  private hydrating = false
+  private hydrationQueue = new Set<string>()
+  private hydrationBatchStartedAt: number | null = null
+  private hydrationBatchGroups = 0
   private lastCheckedAt: number | undefined
   private lastReadAt = 0
   private events: GroupExitMonitorEvent[] = []
@@ -66,8 +88,11 @@ class GroupExitMonitorService {
   private notificationRoomIds = new Set<string>()
   private loaded = false
   private accountRoot = ''
+  private groupNamesByRoomId = new Map<string, string>()
+  private groupNamesRefreshPending = true
   private eventSequence = 0
   private scopeGeneration = 0
+  private legacyFallbackLogged = false
   private notificationTemplate = normalizeGroupExitNotificationTemplate(undefined)
 
   constructor(deps: GroupExitMonitorServiceDependencies = {}) {
@@ -94,10 +119,15 @@ class GroupExitMonitorService {
   async start(nativeMonitorActive: boolean): Promise<void> {
     this.ensureLoaded()
     const currentRoot = chat.getCurrentAccountRoot()
+    if (!currentRoot) {
+      this.active = true
+      this.nativeMonitorActive = nativeMonitorActive
+      this.broadcast()
+      return
+    }
     if (
-      currentRoot &&
-      this.accountRoot &&
-      path.resolve(currentRoot) !== path.resolve(this.accountRoot)
+      (this.accountRoot && !sameAccountRoot(currentRoot, this.accountRoot)) ||
+      (!this.accountRoot && this.snapshots.size > 0)
     ) {
       this.actionGateway.clearMemberEvents?.()
       this.events = []
@@ -105,32 +135,31 @@ class GroupExitMonitorService {
       this.monitorSelectionConfigured = true
       this.monitoredRoomIds.clear()
       this.notificationRoomIds.clear()
+      this.snapshots.clear()
+      this.groupNamesByRoomId.clear()
     }
-    if (currentRoot) this.accountRoot = currentRoot
+    this.accountRoot = currentRoot
+    this.groupNamesRefreshPending = true
     this.active = true
     this.nativeMonitorActive = nativeMonitorActive
-    this.snapshots.clear()
     this.checkQueued = false
     this.initializing = true
     const scopeGeneration = ++this.scopeGeneration
-    const generation = this.eventSequence + 1
-    this.eventSequence = generation
+    this.eventSequence += 1
     try {
-      const groups = await this.readGroups()
-      if (
-        !this.active ||
-        this.eventSequence !== generation ||
-        this.scopeGeneration !== scopeGeneration
-      )
-        return
-      if (groups) this.replaceSnapshots(groups)
-      this.save()
-      this.broadcast()
+      const checked = await this.runMembershipCheck(scopeGeneration)
+      if (!this.active || this.scopeGeneration !== scopeGeneration) return
+      if (!checked) {
+        this.save()
+        this.broadcast()
+      }
     } finally {
       this.initializing = false
       if (this.checkQueued && this.active) {
         this.checkQueued = false
         void this.check()
+      } else {
+        this.startNextSnapshotHydration()
       }
     }
   }
@@ -140,8 +169,9 @@ class GroupExitMonitorService {
     this.nativeMonitorActive = false
     this.eventSequence += 1
     this.scopeGeneration += 1
-    this.snapshots.clear()
     this.checkQueued = false
+    this.hydrationQueue.clear()
+    this.groupNamesRefreshPending = true
     if (this.changeTimer) clearTimeout(this.changeTimer)
     this.changeTimer = null
     this.broadcast()
@@ -154,6 +184,7 @@ class GroupExitMonitorService {
     } catch {
       // 缓存清理失败时继续检查。
     }
+    this.groupNamesRefreshPending = true
     if (this.changeTimer) clearTimeout(this.changeTimer)
     this.changeTimer = setTimeout(() => {
       this.changeTimer = null
@@ -175,13 +206,19 @@ class GroupExitMonitorService {
     this.eventSequence += 1
     this.scopeGeneration += 1
     this.monitorSelectionConfigured = true
-    this.monitoredRoomIds = normalizeRoomIds(roomIds)
+    const nextMonitoredRoomIds = normalizeRoomIds(roomIds)
+    for (const roomId of this.snapshots.keys()) {
+      if (!nextMonitoredRoomIds.has(roomId)) this.snapshots.delete(roomId)
+    }
+    for (const roomId of this.hydrationQueue) {
+      if (!nextMonitoredRoomIds.has(roomId)) this.hydrationQueue.delete(roomId)
+    }
+    this.monitoredRoomIds = nextMonitoredRoomIds
+    this.groupNamesRefreshPending = true
     const requestedNotifications = normalizeRoomIds(notificationRoomIds)
     this.notificationRoomIds = new Set(
       Array.from(requestedNotifications).filter((roomId) => this.monitoredRoomIds.has(roomId))
     )
-    // 更换监控范围后重新建基线，避免旧快照误报。
-    this.snapshots.clear()
     this.lastCheckedAt = undefined
     this.save()
     this.broadcast()
@@ -221,8 +258,16 @@ class GroupExitMonitorService {
   }
 
   private async check(): Promise<void> {
-    if (!this.active || !chat.isReady()) return
-    if (this.initializing) {
+    const currentRoot = chat.getCurrentAccountRoot()
+    if (
+      !this.active ||
+      !chat.isReady() ||
+      !currentRoot ||
+      !this.accountRoot ||
+      !sameAccountRoot(currentRoot, this.accountRoot)
+    )
+      return
+    if (this.initializing || this.hydrating) {
       this.checkQueued = true
       return
     }
@@ -234,143 +279,240 @@ class GroupExitMonitorService {
     this.checking = true
     const scopeGeneration = this.scopeGeneration
     try {
-      const groups = await this.readGroups()
-      if (!groups || !this.active || scopeGeneration !== this.scopeGeneration) return
-
-      const currentRoomIds = new Set(groups.map((group) => group.roomId))
-      for (const roomId of this.snapshots.keys()) {
-        if (!currentRoomIds.has(roomId)) this.snapshots.delete(roomId)
-      }
-
-      const notificationTasks: Promise<void>[] = []
-      for (const next of groups) {
-        if (scopeGeneration !== this.scopeGeneration) return
-        if (next.membersValid === false) continue
-        const previous = this.snapshots.get(next.roomId)
-        if (previous?.membersValid === false) {
-          this.snapshots.set(next.roomId, next)
-          continue
-        }
-        // 空数组可能是查询失败，先保留旧基线，避免误报。
-        if (previous && previous.members.length > 0 && next.members.length === 0) continue
-
-        this.snapshots.set(next.roomId, next)
-        if (!previous) continue
-
-        // 只有群人数下降才记录退群。
-        if (next.members.length >= previous.members.length) continue
-
-        const removed = findRemovedGroupMembers(previous.members, next.members)
-        for (const member of removed) {
-          const event = this.recordExit(next, member, previous.members.length, next.members.length)
-          if (event && this.notificationRoomIds.has(next.roomId)) {
-            notificationTasks.push(this.notifyGroup(next, event))
-          }
-        }
-      }
-      if (notificationTasks.length) await Promise.all(notificationTasks)
-      if (!this.active || scopeGeneration !== this.scopeGeneration) return
-      this.lastCheckedAt = Date.now()
-      this.save()
-      this.broadcast()
+      await this.runMembershipCheck(scopeGeneration)
     } finally {
       this.checking = false
       if (this.checkQueued && this.active) {
         this.checkQueued = false
         void this.check()
+      } else {
+        this.startNextSnapshotHydration()
       }
     }
   }
 
-  private async readGroups(): Promise<GroupSnapshotRecord[] | null> {
+  private async runMembershipCheck(scopeGeneration: number): Promise<boolean> {
+    const startedAt = Date.now()
+    const result = await this.readMemberships()
+    const membershipCostMs = Date.now() - startedAt
+    let changedGroups = 0
+    if (result.groups && this.active && scopeGeneration === this.scopeGeneration) {
+      changedGroups = await this.applyCurrentMemberships(result.groups, scopeGeneration)
+    }
+    console.log(
+      `[GroupMonitor] check mode=${result.mode} groups=${result.groupCount} membershipCostMs=${membershipCostMs} changedGroups=${changedGroups} totalCostMs=${Date.now() - startedAt}`
+    )
+    return result.groups !== null
+  }
+
+  private async readMemberships(): Promise<MembershipReadResult> {
+    await this.refreshGroupNamesIfNeeded()
     const database = chat.getChatDb()
-    if (!database) return null
+    const roomIds = Array.from(this.monitoredRoomIds)
+    const batchAvailable = chat.isGroupMemberIdsBatchAvailable()
+    const mode: MembershipMode = batchAvailable ? 'batch' : 'legacy'
+    if (!database) return { mode, groupCount: roomIds.length, groups: null }
     try {
       const client = database.getWcdb4Client()
-      const rawSessions = await client.getSessionsAsync({ hydrateDisplayNames: true })
-      const sessions = Array.isArray(rawSessions) ? rawSessions : []
-      const groups = sessions.filter(
-        (session) =>
-          session.username?.endsWith('@chatroom') === true &&
-          (!this.monitorSelectionConfigured || this.monitoredRoomIds.has(session.username))
-      )
-      const records: Array<GroupSnapshotRecord | null> = new Array(groups.length).fill(null)
-      let nextIndex = 0
-      const workerCount = Math.min(GROUP_READ_CONCURRENCY, groups.length)
-      await Promise.all(
-        Array.from({ length: workerCount }, async () => {
-          while (true) {
-            const index = nextIndex++
-            if (index >= groups.length) return
-            const session = groups[index]
-            const contactId = client.md5(session.username)
-            try {
-              const snapshot = await chat.getGroupSnapshotAsync(contactId)
-              const groupName = cleanGroupName(session.nickname, session.username)
-              if (!snapshot || snapshot.roomId !== session.username) {
-                records[index] = {
-                  contactId,
-                  roomId: session.username,
-                  groupName,
-                  members: [],
-                  membersValid: false
-                }
-                continue
-              }
-              const rawMembers = (snapshot as { members?: unknown }).members
-              if (!Array.isArray(rawMembers)) {
-                console.warn(
-                  `[GroupMonitor] 群成员快照不是数组 roomId=${session.username}; 保留上一份基线`
-                )
-                records[index] = {
-                  contactId,
-                  roomId: session.username,
-                  groupName,
-                  members: [],
-                  membersValid: false
-                }
-                continue
-              }
-              records[index] = {
-                contactId,
-                roomId: snapshot.roomId,
-                groupName: cleanGroupName(session.nickname, snapshot.roomId),
-                members: rawMembers
-                  .filter((member) => member?.wxid)
-                  .map((member) => ({
-                    wxid: member.wxid,
-                    nickname: member.nickname,
-                    groupNickname: member.groupNickname,
-                    wechatNickname: member.wechatNickname,
-                    remark: member.remark,
-                    avatar: member.avatar
-                  })),
-                membersValid: true
-              }
-            } catch (error) {
-              console.warn(`[GroupMonitor] 读取群成员失败 roomId=${session.username}:`, error)
-              records[index] = {
-                contactId,
-                roomId: session.username,
-                groupName: cleanGroupName(session.nickname, session.username),
-                members: [],
-                membersValid: false
-              }
+      const capturedAt = Date.now()
+
+      if (batchAvailable) {
+        const snapshots = await chat.getGroupMemberIdsBatchAsync(roomIds)
+        if (!snapshots) return { mode, groupCount: roomIds.length, groups: null }
+        return {
+          mode,
+          groupCount: roomIds.length,
+          groups: snapshots.map((snapshot) => {
+            const previous = this.snapshots.get(snapshot.roomId)
+            return {
+              contactId: previous?.contactId || client.md5(snapshot.roomId),
+              roomId: snapshot.roomId,
+              groupName: resolveGroupName(snapshot.roomId, this.groupNamesByRoomId, previous),
+              capturedAt,
+              memberIds: normalizeMemberIds(snapshot.memberIds),
+              membersValid: snapshot.status === 'ok'
             }
-          }
+          })
+        }
+      }
+
+      if (!this.legacyFallbackLogged) {
+        this.legacyFallbackLogged = true
+        console.warn('[GroupMonitor] batch membership unavailable; using legacy fallback')
+      }
+      const groups: GroupMembershipRecord[] = []
+      for (const roomId of roomIds) {
+        const previous = this.snapshots.get(roomId)
+        const snapshot = await chat.getGroupMemberIdsAsync(roomId)
+        groups.push({
+          contactId: previous?.contactId || client.md5(roomId),
+          roomId,
+          groupName: resolveGroupName(roomId, this.groupNamesByRoomId, previous),
+          capturedAt,
+          memberIds: snapshot?.roomId === roomId ? normalizeMemberIds(snapshot.memberIds) : [],
+          membersValid: snapshot?.roomId === roomId
         })
-      )
-      return records.filter((record): record is GroupSnapshotRecord => Boolean(record))
+      }
+      return { mode, groupCount: roomIds.length, groups }
     } catch (error) {
-      console.warn('[GroupMonitor] 读取群成员快照失败:', error)
-      return null
+      console.warn('[GroupMonitor] 读取群成员状态失败:', error)
+      return { mode, groupCount: roomIds.length, groups: null }
     }
   }
 
-  private replaceSnapshots(groups: GroupSnapshotRecord[]): void {
-    this.snapshots = new Map(
-      groups.filter((group) => group.membersValid !== false).map((group) => [group.roomId, group])
+  private async applyCurrentMemberships(
+    groups: GroupMembershipRecord[],
+    scopeGeneration: number
+  ): Promise<number> {
+    const notifications: Array<{ group: GroupSnapshotRecord; event: GroupExitMonitorEvent }> = []
+    let changedGroups = 0
+    for (const membership of groups) {
+      if (!this.active || scopeGeneration !== this.scopeGeneration) return changedGroups
+      if (membership.membersValid === false) continue
+      const previous = this.snapshots.get(membership.roomId)
+      // 空数组可能是查询失败，先保留旧基线，避免误报和覆盖最后有效快照。
+      if (previous && previous.members.length > 0 && membership.memberIds.length === 0) continue
+
+      const previousMembers = new Map(previous?.members.map((member) => [member.wxid, member]))
+      const next: GroupSnapshotRecord = {
+        contactId: membership.contactId,
+        roomId: membership.roomId,
+        groupName:
+          membership.groupName === membership.roomId && previous
+            ? previous.groupName
+            : membership.groupName,
+        capturedAt: membership.capturedAt,
+        members: membership.memberIds.map(
+          (wxid) => previousMembers.get(wxid) || ({ wxid } satisfies GroupExitMonitorMember)
+        ),
+        membersValid: true
+      }
+      const membershipChanged = !previous || !sameMemberIds(previous.members, membership.memberIds)
+      if (membershipChanged) changedGroups += 1
+
+      if (previous && next.members.length < previous.members.length) {
+        const removed = findRemovedGroupMembers(previous.members, next.members)
+        for (const member of removed) {
+          const event = this.recordExit(next, member, previous.members.length, next.members.length)
+          if (event && this.notificationRoomIds.has(next.roomId)) {
+            notifications.push({ group: next, event })
+          }
+        }
+      }
+
+      // Last Good Snapshot 必须在 Diff 完成后才能替换。
+      this.snapshots.set(next.roomId, next)
+      if (next.members.some((member) => !hasMemberMetadata(member))) {
+        this.hydrationQueue.add(next.roomId)
+      }
+    }
+
+    if (!this.active || scopeGeneration !== this.scopeGeneration) return changedGroups
+    this.lastCheckedAt = Date.now()
+    // 先把事件和新基线作为同一检查点落盘，再执行可失败的通知动作。
+    this.save()
+    this.broadcast()
+    if (notifications.length) {
+      await Promise.all(notifications.map(({ group, event }) => this.notifyGroup(group, event)))
+    }
+    return changedGroups
+  }
+
+  private startNextSnapshotHydration(): void {
+    if (!this.active) {
+      this.finishHydrationBatch()
+      return
+    }
+    if (this.initializing || this.checking || this.hydrating) return
+    if (this.checkQueued || this.changeTimer) {
+      this.finishHydrationBatch()
+      return
+    }
+
+    const roomId = this.hydrationQueue.values().next().value as string | undefined
+    if (!roomId) {
+      this.finishHydrationBatch()
+      return
+    }
+    this.hydrationQueue.delete(roomId)
+    const baseline = this.snapshots.get(roomId)
+    if (!baseline || !this.monitoredRoomIds.has(roomId)) {
+      this.startNextSnapshotHydration()
+      return
+    }
+
+    this.hydrating = true
+    if (this.hydrationBatchStartedAt === null) this.hydrationBatchStartedAt = Date.now()
+    this.hydrationBatchGroups += 1
+    const scopeGeneration = this.scopeGeneration
+    void chat
+      .getGroupSnapshotAsync(baseline.contactId)
+      .then((snapshot) => {
+        const current = this.snapshots.get(roomId)
+        if (
+          !snapshot ||
+          snapshot.roomId !== roomId ||
+          !this.active ||
+          scopeGeneration !== this.scopeGeneration ||
+          !current ||
+          !sameMemberIds(
+            current.members,
+            snapshot.members.map((member) => member.wxid)
+          )
+        )
+          return
+
+        const hydrated = new Map(
+          normalizeSnapshotMembers(snapshot.members).map((member) => [member.wxid, member])
+        )
+        this.snapshots.set(roomId, {
+          ...current,
+          groupName: resolveGroupName(roomId, this.groupNamesByRoomId, current, snapshot.groupName),
+          members: current.members.map((member) => {
+            const refreshed = hydrated.get(member.wxid)
+            return refreshed ? { ...member, ...refreshed } : member
+          })
+        })
+        this.hydrationQueue.delete(roomId)
+        this.save()
+        this.broadcast()
+      })
+      .catch(() => undefined)
+      .finally(() => {
+        this.hydrating = false
+        if (this.checkQueued && this.active) {
+          this.finishHydrationBatch()
+          this.checkQueued = false
+          void this.check()
+        } else if (this.changeTimer) {
+          this.finishHydrationBatch()
+        } else {
+          this.startNextSnapshotHydration()
+        }
+      })
+  }
+
+  private finishHydrationBatch(): void {
+    if (this.hydrationBatchStartedAt === null || this.hydrationBatchGroups === 0) return
+    console.log(
+      `[GroupMonitor] hydration groups=${this.hydrationBatchGroups} costMs=${Date.now() - this.hydrationBatchStartedAt}`
     )
+    this.hydrationBatchStartedAt = null
+    this.hydrationBatchGroups = 0
+  }
+
+  private async refreshGroupNamesIfNeeded(): Promise<void> {
+    if (!this.groupNamesRefreshPending) return
+    this.groupNamesRefreshPending = false
+    try {
+      const names = await chat.getGroupNamesAsync()
+      for (const [roomId, name] of Object.entries(names || {})) {
+        const resolved = normalizeKnownGroupName(roomId, name)
+        if (resolved) this.groupNamesByRoomId.set(roomId, resolved)
+      }
+    } catch {
+      // Session 群名是展示信息；读取失败时继续使用快照中的已知群名。
+    }
   }
 
   private recordExit(
@@ -508,6 +650,7 @@ class GroupExitMonitorService {
       this.notificationTemplate = normalizeGroupExitNotificationTemplate(
         stored.notificationTemplate
       )
+      this.snapshots = normalizeSnapshots(stored.snapshots, this.monitoredRoomIds)
     } catch {
       // 首次启动或文件损坏时从空记录开始。
       this.events = []
@@ -516,6 +659,7 @@ class GroupExitMonitorService {
       this.monitoredRoomIds.clear()
       this.notificationRoomIds.clear()
       this.notificationTemplate = normalizeGroupExitNotificationTemplate(undefined)
+      this.snapshots.clear()
     }
   }
 
@@ -532,12 +676,13 @@ class GroupExitMonitorService {
           monitorSelectionConfigured: this.monitorSelectionConfigured,
           monitoredRoomIds: Array.from(this.monitoredRoomIds),
           notificationRoomIds: Array.from(this.notificationRoomIds),
-          notificationTemplate: this.notificationTemplate
+          notificationTemplate: this.notificationTemplate,
+          snapshots: Array.from(this.snapshots.values(), toStoredSnapshot)
         },
         { spaces: 2 }
       )
     } catch (error) {
-      console.warn('[GroupMonitor] 保存事件失败:', error)
+      console.warn('[GroupMonitor] 保存状态失败:', error)
     }
   }
 
@@ -557,6 +702,120 @@ function normalizeRoomIds(roomIds: string[]): Set<string> {
   )
 }
 
+function normalizeMemberIds(values: unknown[]): string[] {
+  return Array.from(
+    new Set(values.map((value) => String(value || '').trim()).filter((value) => Boolean(value)))
+  )
+}
+
+function sameMemberIds(previous: GroupExitMonitorMember[], nextIds: string[]): boolean {
+  if (previous.length !== nextIds.length) return false
+  const previousIds = new Set(previous.map((member) => member.wxid))
+  return nextIds.every((wxid) => previousIds.has(wxid))
+}
+
+function hasMemberMetadata(member: GroupExitMonitorMember): boolean {
+  return Boolean(
+    member.nickname?.trim() ||
+    member.groupNickname?.trim() ||
+    member.wechatNickname?.trim() ||
+    member.remark?.trim()
+  )
+}
+
+function sameAccountRoot(left: string, right: string): boolean {
+  const normalize = (value: string): string => {
+    const resolved = path.resolve(value)
+    return process.platform === 'win32' ? resolved.toLowerCase() : resolved
+  }
+  return normalize(left) === normalize(right)
+}
+
+function normalizeSnapshots(
+  values: Partial<StoredGroupSnapshot>[] | undefined,
+  monitoredRoomIds: Set<string>
+): Map<string, GroupSnapshotRecord> {
+  const snapshots = new Map<string, GroupSnapshotRecord>()
+  if (!Array.isArray(values)) return snapshots
+  for (const value of values) {
+    const roomId = String(value?.roomId || '').trim()
+    const capturedAt = Number(value?.capturedAt)
+    if (
+      !roomId.endsWith('@chatroom') ||
+      !monitoredRoomIds.has(roomId) ||
+      !Number.isFinite(capturedAt) ||
+      capturedAt <= 0 ||
+      !Array.isArray(value?.members)
+    ) {
+      continue
+    }
+    snapshots.set(roomId, {
+      contactId: String(value.contactId || ''),
+      roomId,
+      groupName: cleanGroupName(value.groupName, roomId),
+      capturedAt,
+      members: normalizeSnapshotMembers(value.members)
+    })
+  }
+  return snapshots
+}
+
+function normalizeSnapshotMembers(values: GroupExitMonitorMember[]): GroupExitMonitorMember[] {
+  const members: GroupExitMonitorMember[] = []
+  const seen = new Set<string>()
+  for (const value of values) {
+    const wxid = String(value?.wxid || '').trim()
+    if (!wxid || seen.has(wxid)) continue
+    seen.add(wxid)
+    members.push({
+      wxid,
+      ...optionalMemberField('nickname', value.nickname),
+      ...optionalMemberField('groupNickname', value.groupNickname),
+      ...optionalMemberField('wechatNickname', value.wechatNickname),
+      ...optionalMemberField('remark', value.remark),
+      ...optionalMemberField('avatar', value.avatar)
+    })
+  }
+  return members
+}
+
+function optionalMemberField<K extends keyof GroupExitMonitorMember>(
+  key: K,
+  value: unknown
+): Partial<Pick<GroupExitMonitorMember, K>> {
+  const normalized = String(value || '').trim()
+  return normalized ? ({ [key]: normalized } as Pick<GroupExitMonitorMember, K>) : {}
+}
+
+function normalizeKnownGroupName(roomId: string, value: unknown): string {
+  const name = String(value || '').trim()
+  return name && name !== roomId && !name.endsWith('@chatroom') ? name : ''
+}
+
+function resolveGroupName(
+  roomId: string,
+  namesByRoomId: Map<string, string>,
+  previous?: Pick<GroupSnapshotRecord, 'groupName'>,
+  hydratedName?: unknown
+): string {
+  return (
+    normalizeKnownGroupName(roomId, namesByRoomId.get(roomId)) ||
+    normalizeKnownGroupName(roomId, previous?.groupName) ||
+    normalizeKnownGroupName(roomId, hydratedName) ||
+    roomId
+  )
+}
+
+function toStoredSnapshot(snapshot: GroupSnapshotRecord): StoredGroupSnapshot {
+  return {
+    contactId: snapshot.contactId,
+    roomId: snapshot.roomId,
+    groupName: snapshot.groupName,
+    capturedAt: snapshot.capturedAt,
+    members: normalizeSnapshotMembers(snapshot.members)
+  }
+}
+
 function cleanGroupName(value: string | undefined, roomId: string): string {
   const name = String(value || '').trim()
   return name && name !== roomId && !name.startsWith('wxid_') ? name : roomId
diff --git a/src/main/wcdb4-client.ts b/src/main/wcdb4-client.ts
index de7f7fa..2632fd4 100644
--- a/src/main/wcdb4-client.ts
+++ b/src/main/wcdb4-client.ts
@@ -59,6 +59,46 @@ export interface Wcdb4GroupMember {
   m_nsHeadImgUrl: string
 }
 
+export type Wcdb4GroupMemberBatchStatus = 'ok' | 'not_found'
+
+export interface Wcdb4GroupMemberIdsBatchItem {
+  roomId: string
+  status: Wcdb4GroupMemberBatchStatus
+  memberWxids: string[]
+}
+
+function normalizeGroupMemberIdsBatch(
+  value: unknown,
+  requestedRoomIds: string[]
+): Wcdb4GroupMemberIdsBatchItem[] | null {
+  if (!Array.isArray(value) || value.length !== requestedRoomIds.length) return null
+  const requested = new Set(requestedRoomIds)
+  const results = new Map<string, Wcdb4GroupMemberIdsBatchItem>()
+  for (const rawItem of value) {
+    if (!rawItem || typeof rawItem !== 'object') return null
+    const item = rawItem as Record<string, unknown>
+    const roomId = typeof item.roomId === 'string' ? item.roomId.trim() : ''
+    const status = item.status
+    if (
+      !roomId ||
+      !requested.has(roomId) ||
+      results.has(roomId) ||
+      (status !== 'ok' && status !== 'not_found') ||
+      !Array.isArray(item.memberWxids) ||
+      item.memberWxids.some((memberWxid) => typeof memberWxid !== 'string' || !memberWxid.trim())
+    ) {
+      return null
+    }
+    results.set(roomId, {
+      roomId,
+      status,
+      memberWxids: Array.from(new Set(item.memberWxids.map((memberWxid) => memberWxid.trim())))
+    })
+  }
+  if (results.size !== requestedRoomIds.length) return null
+  return requestedRoomIds.map((roomId) => results.get(roomId)!)
+}
+
 /**
  * 联系人表中独立保存的成员名称字段。
  *
@@ -395,6 +435,9 @@ export class Wcdb4Client {
   private wcdbGetGroupMembers:
     | ((handle: number, chatroomId: string, outJson: WcdbVoidOut) => number)
     | null = null
+  private wcdbGetGroupMembersBatch:
+    | ((handle: number, chatroomIdsJson: string, outJson: WcdbVoidOut) => number)
+    | null = null
   private wcdbGetGroupNicknames:
     | ((handle: number, chatroomId: string, outJson: WcdbVoidOut) => number)
     | null = null
@@ -1900,6 +1943,55 @@ export class Wcdb4Client {
     }
   }
 
+  /**
+   * 退群检测热路径：只读取原始成员行并提取 wxid，不补群昵称、联系人资料或头像。
+   * null 表示读取失败，避免调用方把失败误判为成员列表为空。
+   */
+  async getGroupMemberIdsAsync(chatroomId: string): Promise<string[] | null> {
+    if (!this.wcdbGetGroupMembers || !chatroomId) return null
+
+    try {
+      const rows = await this.callJsonAsync<Record<string, unknown>[]>(
+        this.wcdbGetGroupMembers as unknown as KoffiAsyncFunction,
+        chatroomId
+      )
+      const memberRows = Array.isArray(rows) ? rows : []
+      return Array.from(new Set(this.groupMemberUsernames(memberRows)))
+    } catch (error) {
+      console.warn(`[WCDB4] async group member ids failed chatroom=${chatroomId}:`, error)
+      return null
+    }
+  }
+
+  isGroupMemberIdsBatchAvailable(): boolean {
+    return Boolean(this.wcdbGetGroupMembersBatch)
+  }
+
+  async getGroupMemberIdsBatchAsync(
+    roomIds: string[]
+  ): Promise<Wcdb4GroupMemberIdsBatchItem[] | null> {
+    const requestedRoomIds = Array.from(
+      new Set(
+        (Array.isArray(roomIds) ? roomIds : [])
+          .map((roomId) => String(roomId || '').trim())
+          .filter(Boolean)
+      )
+    )
+    if (requestedRoomIds.length === 0) return []
+    if (!this.wcdbGetGroupMembersBatch) return null
+
+    try {
+      const raw = await this.callJsonAsync<unknown>(
+        this.wcdbGetGroupMembersBatch as unknown as KoffiAsyncFunction,
+        JSON.stringify(requestedRoomIds)
+      )
+      return normalizeGroupMemberIdsBatch(raw, requestedRoomIds)
+    } catch (error) {
+      console.warn('[WCDB4] async group member ids batch failed:', error)
+      return null
+    }
+  }
+
   /**
    * 将群成员接口与联系人表组装为语义明确的成员快照。
    *
@@ -2390,6 +2482,14 @@ export class Wcdb4Client {
       this.wcdbGetGroupMembers = null
     }
 
+    try {
+      this.wcdbGetGroupMembersBatch = lib.func(
+        'int32 wcdb_get_group_members_batch(int64 handle, const char* chatroomIdsJson, _Out_ void** outJson)'
+      ) as (handle: number, chatroomIdsJson: string, outJson: WcdbVoidOut) => number
+    } catch {
+      this.wcdbGetGroupMembersBatch = null
+    }
+
     try {
       this.wcdbGetGroupNicknames = lib.func(
         'int32 wcdb_get_group_nicknames(int64 handle, const char* chatroomId, _Out_ void** outJson)'
diff --git a/tests/unit/group-exit-monitor-service.test.ts b/tests/unit/group-exit-monitor-service.test.ts
index c42e2a5..3c07571 100644
--- a/tests/unit/group-exit-monitor-service.test.ts
+++ b/tests/unit/group-exit-monitor-service.test.ts
@@ -9,6 +9,10 @@ const mocks = vi.hoisted(() => ({
     getChatDb: vi.fn(),
     getCurrentAccountRoot: vi.fn(() => 'fixture-account'),
     isReady: vi.fn(() => true),
+    getGroupNamesAsync: vi.fn(async () => ({})),
+    isGroupMemberIdsBatchAvailable: vi.fn(() => true),
+    getGroupMemberIdsBatchAsync: vi.fn(),
+    getGroupMemberIdsAsync: vi.fn(),
     getGroupSnapshotAsync: vi.fn()
   },
   capability: {
@@ -35,17 +39,39 @@ import { GroupExitMonitorService } from '../../src/main/services/group-exit-moni
 import { GROUP_EXIT_NOTIFICATION_TEMPLATE } from '../../src/shared/group-exit-monitor'
 
 const member = { wxid: 'wxid_member', wechatNickname: '微信名', groupNickname: '群内名' }
+const otherMember = { wxid: 'wxid_other', wechatNickname: '另一个人' }
 
 function installGroupDb(): void {
   const client = {
-    getSessionsAsync: vi
-      .fn()
-      .mockResolvedValue([{ username: 'room@chatroom', nickname: '测试群' }]),
-    md5: vi.fn(() => 'room-md5')
+    md5: vi.fn((roomId: string) => `${roomId}-md5`),
+    invalidateGroupNicknameCache: vi.fn()
   }
   mocks.chat.getChatDb.mockReturnValue({ getWcdb4Client: () => client })
 }
 
+function writeBaseline(
+  snapshots: Array<{
+    roomId: string
+    groupName: string
+    members: Array<{ wxid: string; [key: string]: string }>
+  }>,
+  notificationRoomIds: string[] = []
+): void {
+  writeJsonSync(join(mocks.userData, 'group-exit-monitor.json'), {
+    accountRoot: 'fixture-account',
+    events: [],
+    monitoredRoomIds: snapshots.map((snapshot) => snapshot.roomId),
+    notificationRoomIds,
+    snapshots: snapshots.map((snapshot) => ({
+      contactId: `${snapshot.roomId}-md5`,
+      roomId: snapshot.roomId,
+      groupName: snapshot.groupName,
+      capturedAt: Date.now() - 1_000,
+      members: snapshot.members
+    }))
+  })
+}
+
 describe('GroupExitMonitorService', () => {
   const temporaryDirectories: string[] = []
 
@@ -55,7 +81,11 @@ describe('GroupExitMonitorService', () => {
     mocks.chat.getChatDb.mockReset()
     mocks.chat.getCurrentAccountRoot.mockReset().mockReturnValue('fixture-account')
     mocks.chat.isReady.mockReset().mockReturnValue(true)
-    mocks.chat.getGroupSnapshotAsync.mockReset()
+    mocks.chat.getGroupNamesAsync.mockReset().mockResolvedValue({})
+    mocks.chat.isGroupMemberIdsBatchAvailable.mockReset().mockReturnValue(true)
+    mocks.chat.getGroupMemberIdsBatchAsync.mockReset()
+    mocks.chat.getGroupMemberIdsAsync.mockReset()
+    mocks.chat.getGroupSnapshotAsync.mockReset().mockResolvedValue(null)
     mocks.capability.getPersonalWechatSendCapability.mockReset()
     mocks.sender.send.mockReset()
   })
@@ -89,38 +119,418 @@ describe('GroupExitMonitorService', () => {
     expect(service.getState().notificationTemplate).toBe(GROUP_EXIT_NOTIFICATION_TEMPLATE)
   })
 
-  it('keeps the previous baseline when a native snapshot contains null members', async () => {
+  it('uses the Session nickname when establishing a new group baseline', async () => {
     installGroupDb()
+    const callOrder: string[] = []
+    mocks.chat.getGroupNamesAsync.mockImplementation(async () => {
+      callOrder.push('names')
+      return { 'A@chatroom': '测试群A' }
+    })
+    mocks.chat.getGroupMemberIdsBatchAsync.mockImplementation(async () => {
+      callOrder.push('batch')
+      return [{ roomId: 'A@chatroom', status: 'ok', memberIds: [member.wxid] }]
+    })
+    mocks.chat.getGroupSnapshotAsync.mockImplementation(async () => {
+      callOrder.push('hydration')
+      return null
+    })
+    const service = new GroupExitMonitorService()
+    await service.setMonitoredRoomIds(['A@chatroom'])
+    await service.start(true)
+
+    const stored = readJsonSync(join(mocks.userData, 'group-exit-monitor.json'))
+    expect(stored.snapshots[0]).toMatchObject({ roomId: 'A@chatroom', groupName: '测试群A' })
+    expect(callOrder.indexOf('batch')).toBeGreaterThan(callOrder.indexOf('names'))
+    expect(callOrder.indexOf('hydration')).toBeGreaterThan(callOrder.indexOf('batch'))
+  })
+
+  it('preserves existing member metadata during a Batch membership refresh', async () => {
+    installGroupDb()
+    const richMember = {
+      wxid: 'wxid_rich',
+      nickname: 'Shinven',
+      groupNickname: '群内 Shinven',
+      wechatNickname: 'Shinven',
+      remark: '小号',
+      avatar: 'data:image/png;base64,known'
+    }
+    writeBaseline([{ roomId: 'A@chatroom', groupName: '测试群A', members: [richMember] }])
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'A@chatroom', status: 'ok', memberIds: [richMember.wxid] }
+    ])
+    const service = new GroupExitMonitorService()
+
+    await service.start(true)
+
+    expect(
+      readJsonSync(join(mocks.userData, 'group-exit-monitor.json')).snapshots[0].members
+    ).toEqual([richMember])
+  })
+
+  it('keeps hydrated member metadata across the next Batch refresh', async () => {
+    installGroupDb()
+    writeBaseline([
+      { roomId: 'A@chatroom', groupName: '测试群A', members: [{ wxid: 'wxid_rich' }] }
+    ])
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'A@chatroom', status: 'ok', memberIds: ['wxid_rich'] }
+    ])
+    mocks.chat.getGroupSnapshotAsync.mockResolvedValue({
+      roomId: 'A@chatroom',
+      groupName: '测试群A',
+      members: [
+        {
+          wxid: 'wxid_rich',
+          nickname: 'Shinven',
+          groupNickname: '群内 Shinven',
+          wechatNickname: 'Shinven',
+          remark: '小号',
+          avatar: ''
+        }
+      ]
+    })
+    const service = new GroupExitMonitorService()
+    await service.start(true)
+    await vi.waitFor(() => {
+      expect(
+        readJsonSync(join(mocks.userData, 'group-exit-monitor.json')).snapshots[0].members[0]
+      ).toMatchObject({ wxid: 'wxid_rich', nickname: 'Shinven', remark: '小号' })
+    })
+
+    await service.checkNow()
+
+    expect(
+      readJsonSync(join(mocks.userData, 'group-exit-monitor.json')).snapshots[0].members[0]
+    ).toMatchObject({ wxid: 'wxid_rich', nickname: 'Shinven', remark: '小号' })
+  })
+
+  it('preserves old member metadata while allowing a new member to start wxid-only', async () => {
+    installGroupDb()
+    const existing = { wxid: 'wxid_existing', nickname: 'Shinven', remark: '小号' }
+    writeBaseline([{ roomId: 'A@chatroom', groupName: '测试群A', members: [existing] }])
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'A@chatroom', status: 'ok', memberIds: [existing.wxid, 'wxid_new'] }
+    ])
+    mocks.chat.getGroupSnapshotAsync.mockResolvedValue({
+      roomId: 'A@chatroom',
+      groupName: '测试群A',
+      members: [{ wxid: existing.wxid }, { wxid: 'wxid_new', nickname: '新成员' }]
+    })
+    const service = new GroupExitMonitorService()
+
+    await service.start(true)
+
+    await vi.waitFor(() => {
+      expect(
+        readJsonSync(join(mocks.userData, 'group-exit-monitor.json')).snapshots[0].members
+      ).toEqual([existing, { wxid: 'wxid_new', nickname: '新成员' }])
+    })
+  })
+
+  it('repairs a persisted room id fallback when Session metadata becomes available', async () => {
+    installGroupDb()
+    writeBaseline([{ roomId: 'A@chatroom', groupName: 'A@chatroom', members: [member] }])
+    mocks.chat.getGroupNamesAsync.mockResolvedValue({ 'A@chatroom': '测试群A' })
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'A@chatroom', status: 'ok', memberIds: [member.wxid] }
+    ])
+    const service = new GroupExitMonitorService()
+    await service.start(true)
+
+    expect(
+      readJsonSync(join(mocks.userData, 'group-exit-monitor.json')).snapshots[0]
+    ).toMatchObject({ roomId: 'A@chatroom', groupName: '测试群A' })
+  })
+
+  it('keeps the previous resolved group name when Session metadata is temporarily unavailable', async () => {
+    installGroupDb()
+    writeBaseline([{ roomId: 'A@chatroom', groupName: '测试群A', members: [member] }])
+    mocks.chat.getGroupNamesAsync.mockResolvedValue({})
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'A@chatroom', status: 'ok', memberIds: [member.wxid] }
+    ])
+    const service = new GroupExitMonitorService()
+    await service.start(true)
+
+    expect(
+      readJsonSync(join(mocks.userData, 'group-exit-monitor.json')).snapshots[0]
+    ).toMatchObject({ roomId: 'A@chatroom', groupName: '测试群A' })
+  })
+
+  it('uses one resolved group name for both 3-to-1 events and Gateway notification recipients', async () => {
+    installGroupDb()
+    const departed = { wxid: 'wxid_departed', groupNickname: '离群一' }
+    const secondDeparted = { wxid: 'wxid_second_departed', groupNickname: '离群二' }
+    writeBaseline(
+      [
+        {
+          roomId: 'A@chatroom',
+          groupName: 'A@chatroom',
+          members: [member, departed, secondDeparted]
+        }
+      ],
+      ['A@chatroom']
+    )
+    mocks.chat.getGroupNamesAsync.mockResolvedValue({ 'A@chatroom': '测试群A' })
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'A@chatroom', status: 'ok', memberIds: [member.wxid] }
+    ])
+    const requests: Array<{ recipient?: { name?: string } }> = []
+    const actionGateway = {
+      execute: vi.fn(async (request: { recipient?: { name?: string } }) => {
+        requests.push(request)
+        return { status: 'sent', actionId: 'action-1', decision: 'allow' }
+      }),
+      registerMemberEvent: vi.fn()
+    }
+    const service = new GroupExitMonitorService({ actionGateway })
+
+    await service.start(true)
+
+    expect(service.getState().events).toHaveLength(2)
+    expect(service.getState().events).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          memberWxid: departed.wxid,
+          groupName: '测试群A',
+          message: '离群一退出了测试群A',
+          previousCount: 3,
+          currentCount: 1
+        }),
+        expect.objectContaining({
+          memberWxid: secondDeparted.wxid,
+          groupName: '测试群A',
+          message: '离群二退出了测试群A',
+          previousCount: 3,
+          currentCount: 1
+        })
+      ])
+    )
+    expect(requests).toHaveLength(2)
+    expect(requests.every((request) => request.recipient?.name === '测试群A')).toBe(true)
+    expect(mocks.chat.getGroupSnapshotAsync).not.toHaveBeenCalled()
+  })
+
+  it('persists a compact last good snapshot and recovers offline exits after restart', async () => {
+    installGroupDb()
+    const departed = {
+      wxid: 'wxid_departed',
+      nickname: '旧昵称',
+      wechatNickname: '离群成员',
+      groupNickname: '群内昵称',
+      remark: '通讯录备注',
+      avatar: 'data:image/png;base64,not-persisted'
+    }
+    const secondDeparted = {
+      wxid: 'wxid_second_departed',
+      nickname: '另一个旧昵称',
+      wechatNickname: '第二位离群成员',
+      groupNickname: '第二位群内昵称',
+      remark: '第二位通讯录备注'
+    }
     mocks.chat.getGroupSnapshotAsync.mockResolvedValueOnce({
       roomId: 'room@chatroom',
-      members: [member]
+      members: [member, departed, secondDeparted]
     })
+    mocks.chat.getGroupMemberIdsBatchAsync
+      .mockResolvedValueOnce([
+        {
+          roomId: 'room@chatroom',
+          status: 'ok',
+          memberIds: [member.wxid, departed.wxid, secondDeparted.wxid]
+        }
+      ])
+      .mockResolvedValue([{ roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] }])
     const service = new GroupExitMonitorService()
     service.setMonitoredRoomIds(['room@chatroom'])
     await service.start(true)
 
-    mocks.chat.getGroupSnapshotAsync.mockResolvedValueOnce({
-      roomId: 'room@chatroom',
-      members: null
+    const statePath = join(mocks.userData, 'group-exit-monitor.json')
+    await vi.waitFor(() => {
+      expect(readJsonSync(statePath).snapshots[0].members[1]).toMatchObject({
+        wxid: departed.wxid,
+        wechatNickname: departed.wechatNickname
+      })
     })
-    const state = await service.checkNow()
+    const baseline = readJsonSync(statePath)
+    expect(baseline.events).toEqual([])
+    expect(baseline.snapshots).toEqual([
+      expect.objectContaining({
+        roomId: 'room@chatroom',
+        groupName: 'room@chatroom',
+        capturedAt: expect.any(Number),
+        members: [
+          member,
+          expect.objectContaining({ wxid: 'wxid_departed' }),
+          expect.objectContaining({ wxid: 'wxid_second_departed' })
+        ]
+      })
+    ])
+    expect(baseline.snapshots[0].members[1]).toHaveProperty('avatar', departed.avatar)
+
+    service.stop()
+    const restarted = new GroupExitMonitorService()
+    await restarted.start(true)
+
+    expect(restarted.getState().events).toHaveLength(2)
+    expect(restarted.getState().events).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          memberWxid: 'wxid_departed',
+          memberName: departed.groupNickname,
+          previousCount: 3,
+          currentCount: 1
+        }),
+        expect.objectContaining({
+          memberWxid: 'wxid_second_departed',
+          memberName: secondDeparted.groupNickname,
+          previousCount: 3,
+          currentCount: 1
+        })
+      ])
+    )
+    expect(mocks.chat.getGroupMemberIdsBatchAsync).toHaveBeenCalledTimes(2)
+    expect(mocks.chat.getGroupMemberIdsAsync).not.toHaveBeenCalled()
+    expect(readJsonSync(statePath).snapshots[0].members).toEqual([member])
+
+    await restarted.start(true)
+    expect(restarted.getState().events).toHaveLength(2)
+
+    restarted.clearEvents()
+    expect(readJsonSync(statePath).snapshots[0].members).toEqual([member])
+  })
+
+  it('keeps every previous baseline when a batch result is invalid or incomplete', async () => {
+    installGroupDb()
+    writeBaseline([
+      { roomId: 'room@chatroom', groupName: '测试群', members: [member] },
+      { roomId: 'other@chatroom', groupName: '其他群', members: [otherMember] }
+    ])
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue(null)
+    const service = new GroupExitMonitorService()
+    await service.start(true)
+    const state = service.getState()
 
     expect(state.events).toEqual([])
-    expect(state.monitoredGroupCount).toBe(1)
+    expect(state.monitoredGroupCount).toBe(2)
+    expect(readJsonSync(join(mocks.userData, 'group-exit-monitor.json')).snapshots).toEqual([
+      expect.objectContaining({ roomId: 'room@chatroom', members: [member] }),
+      expect.objectContaining({ roomId: 'other@chatroom', members: [otherMember] })
+    ])
+  })
+
+  it('treats not_found as unavailable and preserves the last good snapshot', async () => {
+    installGroupDb()
+    writeBaseline([
+      { roomId: 'room@chatroom', groupName: '测试群', members: [member, otherMember] }
+    ])
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'room@chatroom', status: 'not_found', memberIds: [] }
+    ])
+    const service = new GroupExitMonitorService()
+
+    await service.start(true)
+
+    expect(service.getState().events).toEqual([])
+    expect(
+      readJsonSync(join(mocks.userData, 'group-exit-monitor.json')).snapshots[0].members
+    ).toEqual([member, otherMember])
+  })
+
+  it('uses the legacy member reader only when the batch symbol is unavailable', async () => {
+    installGroupDb()
+    writeBaseline([
+      { roomId: 'room@chatroom', groupName: '测试群', members: [member, otherMember] },
+      {
+        roomId: 'other@chatroom',
+        groupName: '其他群',
+        members: [{ wxid: 'wxid_stays', nickname: '保留成员' }]
+      }
+    ])
+    mocks.chat.isGroupMemberIdsBatchAvailable.mockReturnValue(false)
+    mocks.chat.getGroupMemberIdsAsync.mockImplementation(async (roomId: string) => ({
+      roomId,
+      memberIds: roomId === 'room@chatroom' ? [member.wxid] : ['wxid_stays']
+    }))
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => undefined)
+    const service = new GroupExitMonitorService()
+
+    await service.start(true)
+    await service.checkNow()
+
+    expect(service.getState().events).toHaveLength(1)
+    expect(mocks.chat.getGroupMemberIdsBatchAsync).not.toHaveBeenCalled()
+    expect(mocks.chat.getGroupMemberIdsAsync).toHaveBeenCalledTimes(4)
+    expect(warn).toHaveBeenCalledTimes(1)
+    expect(warn).toHaveBeenCalledWith(
+      '[GroupMonitor] batch membership unavailable; using legacy fallback'
+    )
+    warn.mockRestore()
+  })
+
+  it('keeps snapshots when only notification settings change', async () => {
+    writeBaseline([{ roomId: 'room@chatroom', groupName: '测试群', members: [member] }])
+    const service = new GroupExitMonitorService()
+    service.getState()
+
+    await service.setMonitoredRoomIds(['room@chatroom'], ['room@chatroom'])
+
+    const stored = readJsonSync(join(mocks.userData, 'group-exit-monitor.json'))
+    expect(stored.notificationRoomIds).toEqual(['room@chatroom'])
+    expect(stored.snapshots).toHaveLength(1)
+    expect(stored.snapshots[0].members).toEqual([member])
+  })
+
+  it('retains existing baselines and only establishes a baseline for a newly monitored group', async () => {
+    installGroupDb()
+    writeBaseline([{ roomId: 'room@chatroom', groupName: '测试群', members: [member] }])
+    const service = new GroupExitMonitorService()
+    await service.setMonitoredRoomIds(['room@chatroom', 'new-room@chatroom'])
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] },
+      { roomId: 'new-room@chatroom', status: 'ok', memberIds: ['wxid_new_group_member'] }
+    ])
+    await service.start(true)
+
+    expect(service.getState().events).toEqual([])
+    const stored = readJsonSync(join(mocks.userData, 'group-exit-monitor.json'))
+    expect(stored.snapshots.map((snapshot: { roomId: string }) => snapshot.roomId).sort()).toEqual([
+      'new-room@chatroom',
+      'room@chatroom'
+    ])
+  })
+
+  it('does not diff persisted snapshots across account roots', async () => {
+    installGroupDb()
+    writeBaseline([
+      {
+        roomId: 'room@chatroom',
+        groupName: '测试群',
+        members: [member, { wxid: 'wxid_account_a_member' }]
+      }
+    ])
+
+    mocks.chat.getCurrentAccountRoot.mockReturnValue('different-account')
+    const switched = new GroupExitMonitorService()
+    await switched.start(true)
+
+    expect(switched.getState().events).toEqual([])
+    const stored = readJsonSync(join(mocks.userData, 'group-exit-monitor.json'))
+    expect(stored.accountRoot).toBe('different-account')
+    expect(stored.snapshots).toEqual([])
   })
 
   it('returns from scope saving before the background baseline read completes', async () => {
     installGroupDb()
-    mocks.chat.getGroupSnapshotAsync.mockResolvedValueOnce({
-      roomId: 'room@chatroom',
-      members: [member]
-    })
+    writeBaseline([{ roomId: 'room@chatroom', groupName: '测试群', members: [member] }])
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValueOnce([
+      { roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] }
+    ])
     const service = new GroupExitMonitorService()
-    service.setMonitoredRoomIds(['room@chatroom'])
     await service.start(true)
 
     let release!: (snapshot: unknown) => void
-    mocks.chat.getGroupSnapshotAsync.mockReturnValueOnce(
+    mocks.chat.getGroupMemberIdsBatchAsync.mockReturnValueOnce(
       new Promise((resolve) => {
         release = resolve
       })
@@ -130,27 +540,148 @@ describe('GroupExitMonitorService', () => {
 
     expect(Date.now() - startedAt).toBeLessThan(250)
     expect(state.monitoredRoomIds).toEqual(['room@chatroom'])
-    release({ roomId: 'room@chatroom', members: [member] })
+    release([{ roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] }])
+  })
+
+  it('detects a removed member across multiple groups without full snapshot hydration', async () => {
+    installGroupDb()
+    const departed = {
+      wxid: 'wxid_departed',
+      wechatNickname: 'Previous Snapshot 姓名',
+      groupNickname: 'Previous Snapshot 群昵称',
+      remark: 'Previous Snapshot 备注'
+    }
+    writeBaseline([
+      { roomId: 'room@chatroom', groupName: '目标群', members: [member, departed] },
+      {
+        roomId: 'other-1@chatroom',
+        groupName: '其他群 1',
+        members: [{ wxid: 'wxid_other_1', nickname: '成员 1' }]
+      },
+      {
+        roomId: 'other-2@chatroom',
+        groupName: '其他群 2',
+        members: [{ wxid: 'wxid_other_2', nickname: '成员 2' }]
+      }
+    ])
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] },
+      { roomId: 'other-1@chatroom', status: 'ok', memberIds: ['wxid_other_1'] },
+      { roomId: 'other-2@chatroom', status: 'ok', memberIds: ['wxid_other_2'] }
+    ])
+
+    const service = new GroupExitMonitorService()
+    await service.start(true)
+
+    expect(service.getState().events[0]).toMatchObject({
+      memberWxid: departed.wxid,
+      memberName: departed.groupNickname,
+      wechatName: departed.wechatNickname,
+      groupRemark: departed.groupNickname,
+      contactRemark: departed.remark
+    })
+    expect(mocks.chat.getGroupMemberIdsBatchAsync).toHaveBeenCalledOnce()
+    expect(mocks.chat.getGroupMemberIdsBatchAsync).toHaveBeenCalledWith([
+      'room@chatroom',
+      'other-1@chatroom',
+      'other-2@chatroom'
+    ])
+    expect(mocks.chat.getGroupMemberIdsAsync).not.toHaveBeenCalled()
+    expect(mocks.chat.getGroupSnapshotAsync).not.toHaveBeenCalled()
+  })
+
+  it('logs one summary for a membership check and one for a hydration batch', async () => {
+    installGroupDb()
+    const log = vi.spyOn(console, 'log').mockImplementation(() => undefined)
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] }
+    ])
+    mocks.chat.getGroupSnapshotAsync.mockResolvedValue({
+      roomId: 'room@chatroom',
+      members: [member]
+    })
+    const service = new GroupExitMonitorService()
+    service.setMonitoredRoomIds(['room@chatroom'])
+
+    await service.start(true)
+    await vi.waitFor(() => {
+      expect(log).toHaveBeenCalledWith(
+        expect.stringMatching(/^\[GroupMonitor\] hydration groups=1 costMs=\d+$/)
+      )
+    })
+
+    expect(log).toHaveBeenCalledWith(
+      expect.stringMatching(
+        /^\[GroupMonitor\] check mode=batch groups=1 membershipCostMs=\d+ changedGroups=1 totalCostMs=\d+$/
+      )
+    )
+    log.mockRestore()
+  })
+
+  it('pauses queued hydration as soon as a contact change is pending', async () => {
+    vi.useFakeTimers()
+    installGroupDb()
+    let membershipCalls = 0
+    let finishPriorityCheck!: () => void
+    const priorityCheckFinished = new Promise<void>((resolve) => {
+      finishPriorityCheck = resolve
+    })
+    mocks.chat.getGroupMemberIdsBatchAsync.mockImplementation(async (roomIds: string[]) => {
+      membershipCalls += 1
+      if (membershipCalls === 2) finishPriorityCheck()
+      return roomIds.map((roomId) => ({
+        roomId,
+        status: 'ok',
+        memberIds: [roomId === 'room@chatroom' ? 'wxid_room' : 'wxid_other']
+      }))
+    })
+    let finishFirstHydration!: (snapshot: unknown) => void
+    mocks.chat.getGroupSnapshotAsync
+      .mockReturnValueOnce(
+        new Promise((resolve) => {
+          finishFirstHydration = resolve
+        })
+      )
+      .mockReturnValue(new Promise(() => undefined))
+    const service = new GroupExitMonitorService()
+    service.setMonitoredRoomIds(['room@chatroom', 'other@chatroom'])
+    await service.start(true)
+    expect(mocks.chat.getGroupSnapshotAsync).toHaveBeenCalledOnce()
+
+    service.notifyDatabaseChanged('{"table":"contact","action":"update"}')
+    finishFirstHydration({
+      roomId: 'room@chatroom',
+      members: [{ wxid: 'wxid_room', nickname: '成员 1' }]
+    })
+    await Promise.resolve()
+    await Promise.resolve()
+
+    expect(mocks.chat.getGroupSnapshotAsync).toHaveBeenCalledOnce()
+    expect(mocks.chat.getGroupMemberIdsBatchAsync).toHaveBeenCalledOnce()
+    await vi.advanceTimersByTimeAsync(350)
+    await priorityCheckFinished
+    expect(mocks.chat.getGroupMemberIdsBatchAsync).toHaveBeenCalledTimes(2)
+    service.stop()
+    vi.useRealTimers()
   })
 
   it('renders the saved template before sending a group notification', async () => {
     installGroupDb()
+    writeBaseline(
+      [{ roomId: 'room@chatroom', groupName: '测试群', members: [member, otherMember] }],
+      ['room@chatroom']
+    )
     mocks.capability.getPersonalWechatSendCapability.mockResolvedValue({
       ready: true,
       capabilities: { text: true }
     })
     mocks.sender.send.mockResolvedValue({ success: true })
-    mocks.chat.getGroupSnapshotAsync
-      .mockResolvedValueOnce({
-        roomId: 'room@chatroom',
-        members: [member, { wxid: 'wxid_other', wechatNickname: '另一个人' }]
-      })
-      .mockResolvedValueOnce({ roomId: 'room@chatroom', members: [member] })
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] }
+    ])
     const service = new GroupExitMonitorService()
     service.setNotificationTemplate('退群: {user}/{groupRemark}/{wxid}')
-    service.setMonitoredRoomIds(['room@chatroom'], ['room@chatroom'])
     await service.start(true)
-    await service.checkNow()
 
     expect(mocks.sender.send).toHaveBeenCalledWith({
       type: 'text',
@@ -162,16 +693,15 @@ describe('GroupExitMonitorService', () => {
 
   it('records an exit without creating a send action when notification is disabled', async () => {
     installGroupDb()
-    mocks.chat.getGroupSnapshotAsync
-      .mockResolvedValueOnce({
-        roomId: 'room@chatroom',
-        members: [member, { wxid: 'wxid_other', wechatNickname: '另一个人' }]
-      })
-      .mockResolvedValueOnce({ roomId: 'room@chatroom', members: [member] })
+    writeBaseline([
+      { roomId: 'room@chatroom', groupName: '测试群', members: [member, otherMember] }
+    ])
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] }
+    ])
     const service = new GroupExitMonitorService()
-    service.setMonitoredRoomIds(['room@chatroom'])
     await service.start(true)
-    const state = await service.checkNow()
+    const state = service.getState()
 
     expect(state.events[0]).toMatchObject({
       memberWxid: 'wxid_other',
@@ -183,6 +713,10 @@ describe('GroupExitMonitorService', () => {
 
   it('微信发送能力不可用时仍保留退群事件', async () => {
     installGroupDb()
+    writeBaseline(
+      [{ roomId: 'room@chatroom', groupName: '测试群', members: [member, otherMember] }],
+      ['room@chatroom']
+    )
     mocks.capability.getPersonalWechatSendCapability.mockResolvedValue({
       ready: false,
       supported: true,
@@ -191,16 +725,12 @@ describe('GroupExitMonitorService', () => {
       senderStatus: {},
       message: '当前微信发送能力不可用'
     })
-    mocks.chat.getGroupSnapshotAsync
-      .mockResolvedValueOnce({
-        roomId: 'room@chatroom',
-        members: [member, { wxid: 'wxid_other', wechatNickname: '另一个人' }]
-      })
-      .mockResolvedValueOnce({ roomId: 'room@chatroom', members: [member] })
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] }
+    ])
     const service = new GroupExitMonitorService()
-    service.setMonitoredRoomIds(['room@chatroom'], ['room@chatroom'])
     await service.start(true)
-    const state = await service.checkNow()
+    const state = service.getState()
 
     expect(state.events[0]).toMatchObject({
       notificationStatus: 'failed',
@@ -214,6 +744,10 @@ describe('GroupExitMonitorService', () => {
 
   it('does not send twice when the same snapshot diff is checked again', async () => {
     installGroupDb()
+    writeBaseline(
+      [{ roomId: 'room@chatroom', groupName: '测试群', members: [member, otherMember] }],
+      ['room@chatroom']
+    )
     mocks.capability.getPersonalWechatSendCapability.mockResolvedValue({
       ready: true,
       capabilities: { text: true, image: false, voice: false },
@@ -223,15 +757,10 @@ describe('GroupExitMonitorService', () => {
       message: 'ready'
     })
     mocks.sender.send.mockResolvedValue({ success: true })
-    mocks.chat.getGroupSnapshotAsync
-      .mockResolvedValueOnce({
-        roomId: 'room@chatroom',
-        members: [member, { wxid: 'wxid_other', wechatNickname: '另一个人' }]
-      })
-      .mockResolvedValueOnce({ roomId: 'room@chatroom', members: [member] })
-      .mockResolvedValueOnce({ roomId: 'room@chatroom', members: [member] })
+    mocks.chat.getGroupMemberIdsBatchAsync.mockResolvedValue([
+      { roomId: 'room@chatroom', status: 'ok', memberIds: [member.wxid] }
+    ])
     const service = new GroupExitMonitorService()
-    service.setMonitoredRoomIds(['room@chatroom'], ['room@chatroom'])
     await service.start(true)
     await service.checkNow()
     await service.checkNow()
diff --git a/tests/unit/wcdb-group-members.test.ts b/tests/unit/wcdb-group-members.test.ts
index 6f721c3..e28c34f 100644
--- a/tests/unit/wcdb-group-members.test.ts
+++ b/tests/unit/wcdb-group-members.test.ts
@@ -87,6 +87,35 @@ describe('WCDB group member names', () => {
     )
   })
 
+  it('reads only member ids without hydrating names or avatars', async () => {
+    const getGroupMembers = vi.fn()
+    const callJsonAsync = vi.fn(async () => [
+      ...groupMemberRows,
+      { username: 'wxid-other' },
+      { username: 'wxid-member' },
+      { username: '' }
+    ])
+    const getGroupNicknamesAsync = vi.fn()
+    const readContactMemberNamesAsync = vi.fn()
+    const hydrateAvatarUrlsAsync = vi.fn()
+    const client = Object.assign(Object.create(Wcdb4Client.prototype), {
+      wcdbGetGroupMembers: getGroupMembers,
+      callJsonAsync,
+      getGroupNicknamesAsync,
+      readContactMemberNamesAsync,
+      hydrateAvatarUrlsAsync
+    }) as Wcdb4Client
+
+    await expect(client.getGroupMemberIdsAsync('fixture@chatroom')).resolves.toEqual([
+      'wxid-member',
+      'wxid-other'
+    ])
+    expect(callJsonAsync).toHaveBeenCalledOnce()
+    expect(getGroupNicknamesAsync).not.toHaveBeenCalled()
+    expect(readContactMemberNamesAsync).not.toHaveBeenCalled()
+    expect(hydrateAvatarUrlsAsync).not.toHaveBeenCalled()
+  })
+
   it('falls back to the group nickname without leaking an ambiguous member nickname', () => {
     const getGroupMembers = vi.fn(() => 0)
     const executeQuery = vi.fn(() => 0)
@@ -121,12 +150,14 @@ describe('WCDB group member names', () => {
       wxid: ''
     }) as Wcdb4Client
 
-    const finalizeMessages = (client as unknown as {
-      finalizeMessages: (
-        username: string,
-        rows: Record<string, unknown>[]
-      ) => Array<{ senderNickname?: string }>
-    }).finalizeMessages
+    const finalizeMessages = (
+      client as unknown as {
+        finalizeMessages: (
+          username: string,
+          rows: Record<string, unknown>[]
+        ) => Array<{ senderNickname?: string }>
+      }
+    ).finalizeMessages
 
     expect(
       finalizeMessages.call(client, 'fixture@chatroom', [
@@ -142,3 +173,110 @@ describe('WCDB group member names', () => {
     expect(client.getGroupNicknames).toHaveBeenCalledWith('fixture@chatroom')
   })
 })
+
+describe('WCDB group member batch', () => {
+  it('reads 200 rooms with one batch call and no legacy member call', async () => {
+    const roomIds = Array.from({ length: 200 }, (_, index) => `room-${index}@chatroom`)
+    const batchResult = roomIds.map((roomId, index) => ({
+      roomId,
+      status: 'ok',
+      memberWxids: [`wxid_${index}`]
+    }))
+    const batchAsync = vi.fn(
+      (
+        _handle: number,
+        _roomIdsJson: string,
+        outJson: [unknown],
+        callback: (error: unknown, result: number) => void
+      ) => {
+        outJson[0] = 'batch-json-pointer'
+        callback(null, 0)
+      }
+    )
+    const legacyAsync = vi.fn()
+    const batchBinding = Object.assign(vi.fn(), { async: batchAsync })
+    const legacyBinding = Object.assign(vi.fn(), { async: legacyAsync })
+    const client = Object.assign(Object.create(Wcdb4Client.prototype), {
+      wcdbGetGroupMembersBatch: batchBinding,
+      wcdbGetGroupMembers: legacyBinding,
+      handle: 42,
+      closing: false,
+      nativeCallsInFlight: new Set<Promise<unknown>>(),
+      koffi: { decode: vi.fn(() => JSON.stringify(batchResult)) },
+      wcdbFreeString: vi.fn()
+    }) as Wcdb4Client
+
+    await expect(client.getGroupMemberIdsBatchAsync(roomIds)).resolves.toEqual(batchResult)
+    expect(batchAsync).toHaveBeenCalledOnce()
+    expect(batchAsync).toHaveBeenCalledWith(
+      42,
+      JSON.stringify(roomIds),
+      expect.any(Array),
+      expect.any(Function)
+    )
+    expect(legacyAsync).not.toHaveBeenCalled()
+  })
+
+  it('trims and deduplicates room ids while preserving request order', async () => {
+    const batchBinding = vi.fn()
+    const requestedRoomIds = ['b@chatroom', 'a@chatroom']
+    const callJsonAsync = vi.fn(async () =>
+      requestedRoomIds.map((roomId) => ({ roomId, status: 'ok', memberWxids: [] }))
+    )
+    const client = Object.assign(Object.create(Wcdb4Client.prototype), {
+      wcdbGetGroupMembersBatch: batchBinding,
+      callJsonAsync
+    }) as Wcdb4Client
+
+    await expect(
+      client.getGroupMemberIdsBatchAsync([
+        ' b@chatroom ',
+        'a@chatroom',
+        'b@chatroom',
+        '',
+        ' a@chatroom '
+      ])
+    ).resolves.toEqual([
+      { roomId: 'b@chatroom', status: 'ok', memberWxids: [] },
+      { roomId: 'a@chatroom', status: 'ok', memberWxids: [] }
+    ])
+    expect(callJsonAsync).toHaveBeenCalledWith(batchBinding, JSON.stringify(requestedRoomIds))
+  })
+
+  it.each([
+    ['non-array result', { roomId: 'a@chatroom' }],
+    ['missing room result', [{ roomId: 'a@chatroom', status: 'ok', memberWxids: ['wxid_a'] }]],
+    [
+      'duplicate room result',
+      [
+        { roomId: 'a@chatroom', status: 'ok', memberWxids: ['wxid_a'] },
+        { roomId: 'a@chatroom', status: 'ok', memberWxids: ['wxid_b'] }
+      ]
+    ],
+    [
+      'unknown status',
+      [
+        { roomId: 'a@chatroom', status: 'stale', memberWxids: ['wxid_a'] },
+        { roomId: 'b@chatroom', status: 'ok', memberWxids: ['wxid_b'] }
+      ]
+    ],
+    [
+      'malformed member list',
+      [
+        { roomId: 'a@chatroom', status: 'ok', memberWxids: ['wxid_a'] },
+        { roomId: 'b@chatroom', status: 'ok', memberWxids: [null] }
+      ]
+    ]
+  ])('rejects an invalid batch: %s', async (_name, rawResult) => {
+    const batchBinding = vi.fn()
+    const callJsonAsync = vi.fn(async () => rawResult)
+    const client = Object.assign(Object.create(Wcdb4Client.prototype), {
+      wcdbGetGroupMembersBatch: batchBinding,
+      callJsonAsync
+    }) as Wcdb4Client
+
+    await expect(
+      client.getGroupMemberIdsBatchAsync(['a@chatroom', 'b@chatroom'])
+    ).resolves.toBeNull()
+  })
+})