Feature: In-memory web audit log for the MFC server

Add a process-local security audit trail to the Windows server's web
console, mirroring the Go server's event names and reply shape. The ring
keeps the most recent 1000 events since process start and is never
persisted.

- New query_audit WebSocket command, admin-only, with time/event/actor/
  IP/device/keyword/warn-only filters and pagination; the reply is the
  audit_result payload the existing Audit Log page already understands.
  The challenge advertises caps.auditLog so browsers enable the button.
- Record logins (success, failure, throttling, salt probes), WebSocket
  connect/close, screen and terminal session start/stop/denials,
  clipboard transfers (byte counts only), RDP resets, and admin user
  mutations.
- Repeated failed logins and username probes are de-duplicated per
  connection so scanners cannot flood the ring.
- Audit writes never hold m_ClientsMutex: disconnect paths snapshot the
  client identity before the map entry is erased, and offline-device
  stops are audited after the clients lock is released.

Co-Authored-By: deepseek-flash

.gitignore

@@ -93,6 +93,7 @@ Bin/*
 nul
 server/go/web/assets/index.html
 server/go/users.json
+server/go/devices.json
 server/go/build/
 server/go/.claude/settings.json
 android/app/.cxx/

server/2015Remote/WebService.cpp

@@ -14,6 +14,8 @@
 #include <fstream>
 #include <shlobj.h>
 #include <set>
+#include <deque>
+#include <cstdio>
 
 // Algorithm constants (same as ScreenSpyDlg.cpp)
 #define ALGORITHM_H264 2
@@ -66,6 +68,165 @@ static std::string ParseReqField(const Json::Value& root) {
     return "";
 }
 
+//////////////////////////////////////////////////////////////////////////
+// Web audit trail (in-memory ring)
+//
+// Keeps the most recent kMaxAuditEntries security-relevant operations made
+// through the web console: logins, screen/terminal sessions, clipboard and
+// RDP actions, and admin mutations. The buffer starts empty when the server
+// process starts and is deliberately not persisted — it is a bounded live
+// view for spotting suspicious activity (failed logins, unexpected viewers).
+// Passwords, tokens and clipboard contents are never recorded.
+//////////////////////////////////////////////////////////////////////////
+
+namespace {
+
+constexpr size_t kMaxAuditEntries = 1000;
+
+struct AuditEntry {
+    int64_t  ts = 0;          // epoch seconds (UTC)
+    std::string time;         // "2026-10-18T16:44:17.000Z"
+    std::string level;        // "info" | "warn"
+    std::string event;
+    std::string actor;
+    std::string role;
+    std::string ip;
+    std::string device_id;
+    std::string conn;
+    std::vector<std::pair<std::string, std::string>> extra;
+};
+
+struct AuditQuery {
+    int64_t from = -1;        // epoch seconds, -1 = unset
+    int64_t to = -1;
+    std::string event;
+    std::string actor;
+    std::string ip;
+    std::string device_id;
+    std::string keyword;
+    bool warn_only = false;
+    int  limit = 100;
+    int  offset = 0;
+};
+
+struct AuditQueryResult {
+    std::vector<AuditEntry> events;  // newest first
+    int total = 0;                   // all matches in the ring
+};
+
+// Replace control characters and cap length so an attacker-controlled
+// username / keyword cannot corrupt the record or bloat memory.
+std::string SanitizeAuditString(const std::string& s, size_t maxBytes = 512) {
+    std::string out;
+    out.reserve(s.size() < maxBytes ? s.size() : maxBytes);
+    for (char ch : s) {
+        if (out.size() >= maxBytes) break;
+        unsigned char c = (unsigned char)ch;
+        out.push_back((c < 0x20 || c == 0x7f) ? ' ' : ch);
+    }
+    return out;
+}
+
+std::string FormatAuditTimeUtc(int64_t ts) {
+    time_t t = (time_t)ts;
+    struct tm tmv;
+    if (gmtime_s(&tmv, &t) != 0) return std::string();
+    char buf[40];
+    snprintf(buf, sizeof(buf), "%04d-%02d-%02dT%02d:%02d:%02d.000Z",
+             tmv.tm_year + 1900, tmv.tm_mon + 1, tmv.tm_mday,
+             tmv.tm_hour, tmv.tm_min, tmv.tm_sec);
+    return std::string(buf);
+}
+
+// Accepts the ISO-8601 forms the browser sends (Date.toISOString() or a
+// datetime-local converted in JS). Returns -1 when the value is unusable.
+int64_t ParseAuditTimeUtc(const std::string& s) {
+    int y = 0, mo = 0, d = 0, h = 0, mi = 0, se = 0;
+    // Width-limited conversions: a hostile caller cannot overflow the ints.
+    if (sscanf(s.c_str(), "%4d-%2d-%2dT%2d:%2d:%2d", &y, &mo, &d, &h, &mi, &se) != 6) return -1;
+    if (y < 1970 || mo < 1 || mo > 12 || d < 1 || d > 31 ||
+        h < 0 || h > 23 || mi < 0 || mi > 59 || se < 0 || se > 59) return -1;
+    struct tm tmv = {};
+    tmv.tm_year = y - 1900;
+    tmv.tm_mon  = mo - 1;
+    tmv.tm_mday = d;
+    tmv.tm_hour = h;
+    tmv.tm_min  = mi;
+    tmv.tm_sec  = se;
+    time_t t = _mkgmtime(&tmv);
+    return t == (time_t)-1 ? -1 : (int64_t)t;
+}
+
+std::string ToLowerAscii(std::string s) {
+    for (char& c : s) {
+        if (c >= 'A' && c <= 'Z') c = (char)(c - 'A' + 'a');
+    }
+    return s;
+}
+
+bool AuditEventMatches(const std::string& filter, const std::string& event) {
+    if (filter.empty()) return true;
+    // "web.*" and "web." are prefixes; anything else is an exact match.
+    if (filter.back() == '*') return event.rfind(filter.substr(0, filter.size() - 1), 0) == 0;
+    if (filter.back() == '.') return event.rfind(filter, 0) == 0;
+    return event == filter;
+}
+
+bool AuditEntryMatches(const AuditEntry& e, const AuditQuery& q) {
+    if (q.from >= 0 && e.ts < q.from) return false;
+    if (q.to >= 0 && e.ts > q.to) return false;
+    if (!AuditEventMatches(q.event, e.event)) return false;
+    if (!q.actor.empty() && ToLowerAscii(e.actor) != ToLowerAscii(q.actor)) return false;
+    if (!q.ip.empty() && e.ip != q.ip) return false;
+    if (!q.device_id.empty() && e.device_id != q.device_id) return false;
+    if (q.warn_only && e.level != "warn") return false;
+    if (!q.keyword.empty()) {
+        std::string hay = e.event + " " + e.actor + " " + e.role + " " + e.ip + " " +
+                          e.device_id + " " + e.conn;
+        for (const auto& kv : e.extra) hay += " " + kv.first + "=" + kv.second;
+        if (ToLowerAscii(hay).find(ToLowerAscii(q.keyword)) == std::string::npos) return false;
+    }
+    return true;
+}
+
+class WebAuditRing {
+public:
+    static WebAuditRing& Instance() {
+        static WebAuditRing ring;
+        return ring;
+    }
+
+    void Add(AuditEntry e) {
+        e.time = FormatAuditTimeUtc(e.ts);
+        std::lock_guard<std::mutex> lock(m_Mutex);
+        m_Entries.push_back(std::move(e));
+        while (m_Entries.size() > kMaxAuditEntries) {
+            m_Entries.pop_front();
+        }
+    }
+
+    AuditQueryResult Query(const AuditQuery& q) {
+        AuditQueryResult res;
+        std::lock_guard<std::mutex> lock(m_Mutex);
+        // Iterate newest-first; skip the first `offset` matches and collect
+        // up to `limit`, while still counting every match for the footer.
+        for (auto it = m_Entries.rbegin(); it != m_Entries.rend(); ++it) {
+            if (!AuditEntryMatches(*it, q)) continue;
+            if (res.total >= q.offset && (int)res.events.size() < q.limit) {
+                res.events.push_back(*it);
+            }
+            res.total++;
+        }
+        return res;
+    }
+
+private:
+    std::mutex m_Mutex;
+    std::deque<AuditEntry> m_Entries;
+};
+
+} // namespace
+
 // Challenge-response nonce storage (prevents replay attacks)
 static std::map<void*, std::string> s_ClientNonces;
 static std::mutex s_NonceMutex;
@@ -362,9 +523,12 @@ void CWebService::ServerThread(int port) {
         // 缺少这些字段的服务端（Go / 旧 C++ 二进制）会让新前端自动降级。
         challenge["caps"]["multiWatch"] = true;
         challenge["caps"]["keyframeRequest"] = true;
+        challenge["caps"]["auditLog"] = true;
         Json::StreamWriterBuilder builder;
         builder["indentation"] = "";
         SendText(ws_ptr, Json::writeString(builder, challenge));
+
+        AuditWeb("web.ws.connect", false, "", "", conn->clientIP(), ws_ptr, 0);
     });
 
     // WebSocket disconnect
@@ -443,6 +607,8 @@ void CWebService::ServerThread(int port) {
                 HandleTermResize(ws_ptr, msg);
             } else if (cmd == "term_close") {
                 HandleTermClose(ws_ptr, msg);
+            } else if (cmd == "query_audit") {
+                HandleQueryAudit(ws_ptr, msg);
             }
         }
     });
@@ -527,12 +693,27 @@ void CWebService::HandleLogin(void* ws_ptr, const std::string& msg, const std::s
     // Verify nonce matches (prevents replay)
     std::string storedNonce = ConsumeNonce(ws_ptr);
     if (storedNonce.empty() || storedNonce != clientNonce) {
+        AuditWeb("web.login.failure", true, username, "", client_ip, ws_ptr, 0,
+                 {{"reason", "invalid_challenge"}});
         SendText(ws_ptr, BuildJsonResponse("login_result", false, "Invalid or expired challenge"));
         return;
     }
 
     // Check rate limit
     if (!CheckRateLimit(client_ip)) {
+        bool first = false;
+        {
+            std::lock_guard<std::mutex> lock(m_ClientsMutex);
+            auto it = m_Clients.find(ws_ptr);
+            if (it != m_Clients.end() && !it->second.login_throttle_logged) {
+                it->second.login_throttle_logged = true;
+                first = true;
+            }
+        }
+        if (first) {
+            AuditWeb("web.login.throttled", true, username, "", client_ip, ws_ptr, 0,
+                     {{"reason", "rate_limited"}});
+        }
         SendText(ws_ptr, BuildJsonResponse("login_result", false, "Too many failed attempts. Try again later."));
         return;
     }
@@ -554,6 +735,8 @@ void CWebService::HandleLogin(void* ws_ptr, const std::string& msg, const std::s
 
     if (!user) {
         RecordFailedLogin(client_ip);
+        AuditWeb("web.login.failure", true, username, "", client_ip, ws_ptr, 0,
+                 {{"reason", "unknown_user"}});
         SendText(ws_ptr, BuildJsonResponse("login_result", false, "Invalid credentials"));
         return;
     }
@@ -562,6 +745,8 @@ void CWebService::HandleLogin(void* ws_ptr, const std::string& msg, const std::s
     std::string expectedResponse = WSAuth::ComputeSHA256(user->password_hash + clientNonce);
     if (response != expectedResponse) {
         RecordFailedLogin(client_ip);
+        AuditWeb("web.login.failure", true, username, "", client_ip, ws_ptr, 0,
+                 {{"reason", "bad_password"}});
         SendText(ws_ptr, BuildJsonResponse("login_result", false, "Invalid credentials"));
         return;
     }
@@ -581,6 +766,8 @@ void CWebService::HandleLogin(void* ws_ptr, const std::string& msg, const std::s
         }
     }
 
+    AuditWeb("web.login.success", false, username, user->role, client_ip, ws_ptr, 0);
+
     // Build response
     Json::Value res;
     res["cmd"] = "login_result";
@@ -628,6 +815,24 @@ void CWebService::HandleGetSalt(void* ws_ptr, const std::string& msg) {
     if (!userFound) {
         // Generate deterministic fake salt from username (won't match any real password)
         salt = WSAuth::ComputeSHA256("fake_salt_prefix_" + username).substr(0, 16);
+
+        // Username enumeration probe. Scanners can repeat this in a tight loop,
+        // so record at most one per connection.
+        bool first = false;
+        std::string ip;
+        {
+            std::lock_guard<std::mutex> lock(m_ClientsMutex);
+            auto it = m_Clients.find(ws_ptr);
+            if (it != m_Clients.end() && !it->second.salt_probe_logged) {
+                it->second.salt_probe_logged = true;
+                first = true;
+                ip = it->second.client_ip;
+            }
+        }
+        if (first) {
+            AuditWeb("web.salt.unknown_user", true, "", "", ip, ws_ptr, 0,
+                     {{"username", username}, {"reason", "unknown_user"}});
+        }
     }
 
     Json::Value res;
@@ -703,6 +908,8 @@ void CWebService::HandleConnect(void* ws_ptr, const std::string& token, uint64_t
             }
         }
         if (!hasAccess) {
+            AuditWeb("remote.screen.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                     {{"reason", "group_permission"}});
             send_error("Permission denied");
             return;
         }
@@ -713,6 +920,8 @@ void CWebService::HandleConnect(void* ws_ptr, const std::string& token, uint64_t
     // remote_open, cleared on session teardown), so AI input cannot be injected into a
     // picture a human is watching/controlling.
     if (IsMcpTriggered(device_id)) {
+        AuditWeb("remote.screen.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                 {{"reason", "mcp_session_active"}});
         send_error("Device busy: remote control session active");
         return;
     }
@@ -731,6 +940,8 @@ void CWebService::HandleConnect(void* ws_ptr, const std::string& token, uint64_t
     // Check max clients per device
     int current_count = GetWebClientCount(device_id);
     if (!already && current_count >= m_nMaxClientsPerDevice) {
+        AuditWeb("remote.screen.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                 {{"reason", "too_many_viewers"}});
         send_error("Too many viewers");
         return;
     }
@@ -760,12 +971,19 @@ void CWebService::HandleConnect(void* ws_ptr, const std::string& token, uint64_t
         }
     }
     if (too_many_watch) {
+        AuditWeb("remote.screen.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                 {{"reason", "too_many_watches"}});
         send_error("Too many devices on one connection");
         return;
     }
     // StopRemoteDesktop 会再次锁 m_ClientsMutex，必须在锁外调用。
+    if (!to_stop.empty()) {
+        std::string ip = ClientIP(ws_ptr);
         for (uint64_t id : to_stop) {
             StopRemoteDesktop(id);
+            AuditWeb("remote.screen.stop", false, username, role, ip, ws_ptr, id,
+                     {{"reason", "replaced"}});
+        }
     }
 
     // Start remote desktop session if this is the first web viewer. 若之前已订阅
@@ -782,11 +1000,20 @@ void CWebService::HandleConnect(void* ws_ptr, const std::string& token, uint64_t
                     it->second.watch_device_ids.erase(device_id);
                 }
             }
+            AuditWeb("remote.screen.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                     {{"reason", "start_failed"}});
             send_error("Failed to start remote desktop");
             return;
         }
     }
 
+    if (!already) {
+        AuditWeb("remote.screen.start", false, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                 {{"mode", need_start ? "started" : "attached"},
+                  {"viewers", std::to_string(current_count + 1)},
+                  {"multi_watch", multi_watch ? "true" : "false"}});
+    }
+
     // Get screen dimensions + audio state from device info cache (may not be ready)
     int width = 0, height = 0;
     int audio_enabled = -1;  // -1 = unknown yet (前端走 audio_state 事件兜底)
@@ -891,6 +1118,13 @@ void CWebService::HandleDisconnect(void* ws_ptr, const std::string& token, uint6
     for (uint64_t id : to_stop) {
         StopRemoteDesktop(id);
     }
+    if (!to_stop.empty()) {
+        std::string ip = ClientIP(ws_ptr);
+        for (uint64_t id : to_stop) {
+            AuditWeb("remote.screen.stop", false, username, role, ip, ws_ptr, id,
+                     {{"reason", "disconnect"}});
+        }
+    }
 
     send_reply(true, "");
 }
@@ -1086,6 +1320,10 @@ void CWebService::HandleClipboardSet(void* ws_ptr, const std::string& msg) {
     WideCharToMultiByte(936, 0, wide.c_str(), wlen, (char*)szData.data() + 1, glen, nullptr, nullptr);
 
     ctx->Send2Client(szData.data(), (ULONG)szData.size());
+
+    // Never record clipboard contents -- only the transferred size.
+    AuditWeb("remote.clipboard.set", false, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+             {{"bytes", std::to_string((size_t)glen)}});
 }
 
 void CWebService::HandleClipboardGet(void* ws_ptr, const std::string& token, uint64_t requested_device_id) {
@@ -1108,6 +1346,8 @@ void CWebService::HandleClipboardGet(void* ws_ptr, const std::string& token, uin
     // 单字节命令，客户端以 SendClientClipboard → TOKEN_CLIPBOARD_TEXT 回包
     BYTE bToken = COMMAND_SCREEN_GET_CLIPBOARD;
     ctx->Send2Client(&bToken, sizeof(BYTE));
+
+    AuditWeb("remote.clipboard.get", false, username, role, ClientIP(ws_ptr), ws_ptr, device_id);
 }
 
 void CWebService::HandleRdpReset(void* ws_ptr, const std::string& token, uint64_t requested_device_id) {
@@ -1136,8 +1376,12 @@ void CWebService::HandleRdpReset(void* ws_ptr, const std::string& token, uint64_
     BYTE bToken = CMD_RESTORE_CONSOLE;
     if (ctx->Send2Client(&bToken, 1)) {
         Mprintf("[WebService] Sent RDP reset command to device %llu\n", device_id);
+        AuditWeb("remote.rdp_reset", false, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                 {{"ok", "true"}});
         SendText(ws_ptr, BuildJsonResponse("rdp_reset_result", true));
     } else {
+        AuditWeb("remote.rdp_reset", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                 {{"ok", "false"}});
         SendText(ws_ptr, BuildJsonResponse("rdp_reset_result", false, "Failed to send command"));
     }
 }
@@ -1257,6 +1501,8 @@ void CWebService::HandleCreateUser(void* ws_ptr, const std::string& msg) {
 
     // Only admin can create users
     if (role != "admin") {
+        AuditWeb("web.authz.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, 0,
+                 {{"operation", "create_user"}});
         SendText(ws_ptr, BuildJsonResponse("create_user_result", false, "Permission denied"));
         return;
     }
@@ -1281,7 +1527,12 @@ void CWebService::HandleCreateUser(void* ws_ptr, const std::string& msg) {
         return;
     }
 
-    if (CreateUser(newUsername, newPassword, newRole, allowedGroups)) {
+    bool created = CreateUser(newUsername, newPassword, newRole, allowedGroups);
+    AuditWeb("admin.user.create", !created, username, role, ClientIP(ws_ptr), ws_ptr, 0,
+             {{"target_user", newUsername}, {"target_role", newRole},
+              {"groups", std::to_string(allowedGroups.size())},
+              {"ok", created ? "true" : "false"}});
+    if (created) {
         SendText(ws_ptr, BuildJsonResponse("create_user_result", true));
     } else {
         SendText(ws_ptr, BuildJsonResponse("create_user_result", false, "Failed to create user (may already exist)"));
@@ -1305,13 +1556,18 @@ void CWebService::HandleDeleteUser(void* ws_ptr, const std::string& msg) {
 
     // Only admin can delete users
     if (role != "admin") {
+        AuditWeb("web.authz.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, 0,
+                 {{"operation", "delete_user"}});
         SendText(ws_ptr, BuildJsonResponse("delete_user_result", false, "Permission denied"));
         return;
     }
 
     std::string targetUsername = root.get("username", "").asString();
 
-    if (DeleteUser(targetUsername)) {
+    bool deleted = DeleteUser(targetUsername);
+    AuditWeb("admin.user.delete", !deleted, username, role, ClientIP(ws_ptr), ws_ptr, 0,
+             {{"target_user", targetUsername}, {"ok", deleted ? "true" : "false"}});
+    if (deleted) {
         SendText(ws_ptr, BuildJsonResponse("delete_user_result", true));
     } else {
         SendText(ws_ptr, BuildJsonResponse("delete_user_result", false, "Failed to delete user"));
@@ -1327,6 +1583,8 @@ void CWebService::HandleListUsers(void* ws_ptr, const std::string& token) {
 
     // Only admin can list users
     if (role != "admin") {
+        AuditWeb("web.authz.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, 0,
+                 {{"operation", "list_users"}});
         SendText(ws_ptr, BuildJsonResponse("list_users_result", false, "Permission denied"));
         return;
     }
@@ -1370,6 +1628,8 @@ void CWebService::HandleGetGroups(void* ws_ptr, const std::string& token) {
 
     // Only admin can get groups list (for user management)
     if (role != "admin") {
+        AuditWeb("web.authz.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, 0,
+                 {{"operation", "get_groups"}});
         SendText(ws_ptr, BuildJsonResponse("groups", false, "Permission denied"));
         return;
     }
@@ -1403,6 +1663,132 @@ void CWebService::HandleGetGroups(void* ws_ptr, const std::string& token) {
     SendText(ws_ptr, json);
 }
 
+//////////////////////////////////////////////////////////////////////////
+// Security Audit Trail
+//////////////////////////////////////////////////////////////////////////
+
+std::string CWebService::ClientIP(void* ws_ptr) {
+    std::lock_guard<std::mutex> lock(m_ClientsMutex);
+    auto it = m_Clients.find(ws_ptr);
+    return it != m_Clients.end() ? it->second.client_ip : std::string();
+}
+
+void CWebService::AuditWeb(const std::string& event, bool warn,
+                           const std::string& actor, const std::string& role,
+                           const std::string& ip, void* ws_ptr, uint64_t device_id,
+                           std::initializer_list<std::pair<const char*, std::string>> extra) {
+    AuditEntry e;
+    e.ts = (int64_t)time(nullptr);
+    e.level = warn ? "warn" : "info";
+    e.event = SanitizeAuditString(event, 96);
+    e.actor = SanitizeAuditString(actor, 128);
+    e.role = SanitizeAuditString(role, 32);
+    e.ip = SanitizeAuditString(ip, 64);
+    if (device_id != 0) e.device_id = std::to_string(device_id);
+    if (ws_ptr != nullptr) {
+        char buf[32];
+        snprintf(buf, sizeof(buf), "%p", ws_ptr);
+        e.conn = buf;
+    }
+    for (const auto& kv : extra) {
+        std::string key = SanitizeAuditString(kv.first, 64);
+        if (key.empty()) continue;
+        // Never let a caller shadow the fixed schema fields.
+        if (key == "time" || key == "level" || key == "event" || key == "actor" ||
+            key == "role" || key == "ip" || key == "device_id" || key == "conn") {
+            continue;
+        }
+        e.extra.emplace_back(std::move(key), SanitizeAuditString(kv.second));
+    }
+    WebAuditRing::Instance().Add(std::move(e));
+}
+
+void CWebService::HandleQueryAudit(void* ws_ptr, const std::string& msg) {
+    static const char* replyCmd = "audit_result";
+
+    Json::Value root;
+    Json::Reader reader;
+    if (!reader.parse(msg, root)) {
+        SendText(ws_ptr, BuildJsonResponse(replyCmd, false, "Invalid JSON"));
+        return;
+    }
+
+    std::string token = root["token"].isString() ? root["token"].asString() : "";
+    std::string username, role;
+    if (!ValidateToken(token, username, role)) {
+        SendText(ws_ptr, BuildJsonResponse(replyCmd, false, "Invalid token"));
+        return;
+    }
+    if (role != "admin") {
+        AuditWeb("web.authz.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, 0,
+                 {{"operation", "query_audit"}, {"reason", "not_admin"}});
+        SendText(ws_ptr, BuildJsonResponse(replyCmd, false, "Permission denied"));
+        return;
+    }
+
+    AuditQuery q;
+    std::string from = root["from"].isString() ? root["from"].asString() : "";
+    std::string to = root["to"].isString() ? root["to"].asString() : "";
+    if (!from.empty()) q.from = ParseAuditTimeUtc(from);
+    if (!to.empty()) q.to = ParseAuditTimeUtc(to);
+    q.event     = root["event"].isString() ? root["event"].asString() : "";
+    q.actor     = root["actor"].isString() ? root["actor"].asString() : "";
+    q.ip        = root["ip"].isString() ? root["ip"].asString() : "";
+    q.device_id = root["device_id"].isString() ? root["device_id"].asString() : "";
+    q.keyword   = root["keyword"].isString() ? root["keyword"].asString() : "";
+    q.warn_only = root["warn_only"].isBool() && root["warn_only"].asBool();
+
+    // Read as double first: asInt() on a huge JSON number can throw.
+    double limit_d = root["limit"].isNumeric() ? root["limit"].asDouble() : 100.0;
+    double offset_d = root["offset"].isNumeric() ? root["offset"].asDouble() : 0.0;
+    q.limit = limit_d <= 0.0 ? 100 : (int)(limit_d > 500.0 ? 500.0 : limit_d);
+    q.offset = offset_d < 0.0 ? 0 : (int)(offset_d > 10000.0 ? 10000.0 : offset_d);
+
+    AuditQueryResult r = WebAuditRing::Instance().Query(q);
+
+    Json::Value events(Json::arrayValue);
+    for (const auto& e : r.events) {
+        Json::Value ev;
+        ev["time"] = e.time;
+        ev["level"] = e.level;
+        ev["event"] = e.event;
+        if (!e.actor.empty()) ev["actor"] = e.actor;
+        if (!e.role.empty()) ev["role"] = e.role;
+        if (!e.ip.empty()) ev["ip"] = e.ip;
+        if (!e.device_id.empty()) ev["device_id"] = e.device_id;
+        if (!e.conn.empty()) ev["conn"] = e.conn;
+        for (const auto& kv : e.extra) ev[kv.first] = kv.second;
+        events.append(ev);
+    }
+
+    // Reading the trail is itself an auditable action. This record is added
+    // after the snapshot, so it does not appear in this reply.
+    AuditWeb("admin.audit.query", false, username, role, ClientIP(ws_ptr), ws_ptr, 0,
+             {{"event_filter", q.event},
+              {"actor_filter", q.actor},
+              {"ip_filter", q.ip},
+              {"device_filter", q.device_id},
+              {"keyword", q.keyword},
+              {"warn_only", q.warn_only ? "true" : "false"},
+              {"matches", std::to_string(r.total)},
+              {"returned", std::to_string(r.events.size())},
+              {"offset", std::to_string(q.offset)}});
+
+    Json::Value res;
+    res["cmd"] = replyCmd;
+    res["ok"] = true;
+    res["events"] = events;
+    res["total"] = r.total;
+    res["offset"] = q.offset;
+    res["limit"] = q.limit;
+    res["file"] = "memory (last 1000 events since server startup)";
+    res["file_exists"] = true;
+    res["truncated"] = false;
+    Json::StreamWriterBuilder builder;
+    builder["indentation"] = "";
+    SendText(ws_ptr, Json::writeString(builder, res));
+}
+
 //////////////////////////////////////////////////////////////////////////
 // Token Management (delegated to WebServiceAuth module)
 //////////////////////////////////////////////////////////////////////////
@@ -1430,6 +1816,8 @@ void CWebService::RegisterClient(void* ws_ptr, const std::string& client_ip) {
 
 void CWebService::UnregisterClient(void* ws_ptr) {
     std::set<uint64_t> watched;
+    std::string username, role, ip;
+    uint64_t connected_at = 0;
 
     // Copy the watch set and remove the client under the lock.
     {
@@ -1437,6 +1825,10 @@ void CWebService::UnregisterClient(void* ws_ptr) {
         auto it = m_Clients.find(ws_ptr);
         if (it != m_Clients.end()) {
             watched = std::move(it->second.watch_device_ids);
+            username = it->second.username;
+            role = it->second.role;
+            ip = it->second.client_ip;
+            connected_at = it->second.connected_at;
             m_Clients.erase(it);
         }
     }
@@ -1445,6 +1837,8 @@ void CWebService::UnregisterClient(void* ws_ptr) {
     // StopRemoteDesktop re-locks m_ClientsMutex, so this must run outside the lock.
     for (uint64_t device_id : watched) {
         StopRemoteDesktop(device_id);
+        AuditWeb("remote.screen.stop", false, username, role, ip, ws_ptr, device_id,
+                 {{"reason", "ws_close"}});
     }
 
     // 关闭这个 web client 持有的所有终端会话（MVP 一个用户一台主机一个，但兜底全扫描）
@@ -1454,7 +1848,17 @@ void CWebService::UnregisterClient(void* ws_ptr) {
         for (auto& kv : m_TermSessions) {
             if (kv.second.ws_ptr == ws_ptr) to_close.push_back(kv.first);
         }
-        for (uint64_t did : to_close) CloseTermSessionLocked(did);
+        for (uint64_t did : to_close) CloseTermSessionLocked(did, "ws_close", username, role, ip);
+    }
+
+    // Anonymous connections and rejected scanners are noisy; only authenticated
+    // sessions get a close record (mirrors the Go server's policy). Written last
+    // so the trail reads connect -> ... -> stops -> close for one connection.
+    if (!username.empty()) {
+        uint64_t now = (uint64_t)time(nullptr);
+        AuditWeb("web.ws.close", false, username, role, ip, ws_ptr, 0,
+                 {{"duration_ms", std::to_string((now > connected_at ? now - connected_at : 0) * 1000)},
+                  {"screens", std::to_string(watched.size())}});
     }
 }
 
@@ -2123,6 +2527,8 @@ void CWebService::HandleTermOpen(void* ws_ptr, const std::string& msg) {
     }
     context* ctx = m_pParentDlg->FindHost(device_id);
     if (!ctx) {
+        AuditWeb("remote.terminal.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                 {{"reason", "device_offline"}});
         SendText(ws_ptr, BuildJsonResponse("term_closed", false, "Device offline"));
         return;
     }
@@ -2139,6 +2545,8 @@ void CWebService::HandleTermOpen(void* ws_ptr, const std::string& msg) {
             }
         }
         if (!ok) {
+            AuditWeb("remote.terminal.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                     {{"reason", "group_permission"}});
             SendText(ws_ptr, BuildJsonResponse("term_closed", false, "Permission denied"));
             return;
         }
@@ -2149,6 +2557,8 @@ void CWebService::HandleTermOpen(void* ws_ptr, const std::string& msg) {
         std::lock_guard<std::mutex> lk(m_TermMutex);
         if (m_TermSessions.find(device_id) != m_TermSessions.end() ||
             m_TermPending.find(device_id) != m_TermPending.end()) {
+            AuditWeb("remote.terminal.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                     {{"reason", "terminal_busy"}});
             SendText(ws_ptr, BuildJsonResponse("term_closed", false,
                 "Terminal already open by another viewer"));
             return;
@@ -2162,13 +2572,18 @@ void CWebService::HandleTermOpen(void* ws_ptr, const std::string& msg) {
     // 触发客户端：发 COMMAND_SHELL
     BYTE cmd = COMMAND_SHELL;
     if (!ctx->Send2Client(&cmd, 1)) {
+        {
             std::lock_guard<std::mutex> lk(m_TermMutex);
             m_TermSessions.erase(device_id);
             m_TermPending.erase(device_id);
+        }
+        AuditWeb("remote.terminal.denied", true, username, role, ClientIP(ws_ptr), ws_ptr, device_id,
+                 {{"reason", "send_failed"}});
         SendText(ws_ptr, BuildJsonResponse("term_closed", false, "Send failed"));
         return;
     }
     Mprintf("[WebService] term_open device=%llu user=%s\n", device_id, username.c_str());
+    AuditWeb("remote.terminal.start", false, username, role, ClientIP(ws_ptr), ws_ptr, device_id);
 }
 
 void CWebService::HandleTermInput(void* ws_ptr, const std::string& msg) {
@@ -2233,10 +2648,12 @@ void CWebService::HandleTermClose(void* ws_ptr, const std::string& msg) {
     std::lock_guard<std::mutex> lk(m_TermMutex);
     auto it = m_TermSessions.find(device_id);
     if (it == m_TermSessions.end() || it->second.ws_ptr != ws_ptr) return;
-    CloseTermSessionLocked(device_id);
+    CloseTermSessionLocked(device_id, "user");
 }
 
-void CWebService::CloseTermSessionLocked(uint64_t device_id) {
+void CWebService::CloseTermSessionLocked(uint64_t device_id, const char* reason,
+                                         const std::string& actor, const std::string& role,
+                                         const std::string& ip) {
     auto it = m_TermSessions.find(device_id);
     if (it == m_TermSessions.end()) return;
 
@@ -2253,6 +2670,20 @@ void CWebService::CloseTermSessionLocked(uint64_t device_id) {
     // 通知前端
     SendText(ws_ptr, BuildJsonResponse("term_closed", true, "closed"));
     Mprintf("[WebService] term_closed device=%llu\n", device_id);
+
+    // 身份可能已随 ws 断开被删除（UnregisterClient 路径），此时调用方会传入。
+    std::string username = actor, role_name = role, peer_ip = ip;
+    if (username.empty()) {
+        std::lock_guard<std::mutex> lk(m_ClientsMutex);
+        auto cit = m_Clients.find(ws_ptr);
+        if (cit != m_Clients.end()) {
+            username = cit->second.username;
+            role_name = cit->second.role;
+            peer_ip = cit->second.client_ip;
+        }
+    }
+    AuditWeb("remote.terminal.stop", false, username, role_name, peer_ip, ws_ptr, device_id,
+             {{"reason", reason ? reason : ""}});
 }
 
 bool CWebService::IsTermPending(uint64_t device_id) {
@@ -2329,7 +2760,7 @@ void CWebService::OnTerminalClosed(CONTEXT_OBJECT* ctx) {
     auto it = m_TermContextToDevice.find(ctx);
     if (it == m_TermContextToDevice.end()) return;
     uint64_t device_id = it->second;
-    CloseTermSessionLocked(device_id);
+    CloseTermSessionLocked(device_id, "remote_closed");
 }
 
 //////////////////////////////////////////////////////////////////////////
@@ -2392,6 +2823,8 @@ void CWebService::FlushDeviceChanges() {
     }
 
     // Notify clients watching offline devices
+    struct OfflineAudit { void* ws; std::string actor, role, ip; uint64_t id; };
+    std::vector<OfflineAudit> offline_audits;
     if (!offline.empty()) {
         std::lock_guard<std::mutex> lock(m_ClientsMutex);
         for (auto& [ws_ptr, client] : m_Clients) {
@@ -2409,9 +2842,15 @@ void CWebService::FlushDeviceChanges() {
                 SendText(ws_ptr, Json::writeString(builder, res));
                 client.watch_device_ids.erase(id);
                 client.keyframe_req_at.erase(id);
+                offline_audits.push_back({ws_ptr, client.username, client.role, client.client_ip, id});
             }
         }
     }
+    // AuditWeb 自身会锁 m_ClientsMutex，必须在释放后调用。
+    for (const auto& a : offline_audits) {
+        AuditWeb("remote.screen.stop", false, a.actor, a.role, a.ip, a.ws, a.id,
+                 {{"reason", "device_offline"}});
+    }
 
     // Clear offline devices from cache
     {

server/2015Remote/WebService.h

@@ -5,6 +5,8 @@
 #include <vector>
 #include <map>
 #include <set>
+#include <initializer_list>
+#include <utility>
 #include <atomic>
 #include <chrono>
 #include <mutex>
@@ -76,6 +78,10 @@ struct WebClient {
     uint64_t connected_at;
     uint64_t last_activity;     // Last message/pong received (for heartbeat timeout)
     std::string client_ip;
+    // Per-connection audit de-duplication: probes an attacker can repeat in a
+    // tight loop are recorded once per connection instead of flooding the ring.
+    bool salt_probe_logged = false;
+    bool login_throttle_logged = false;
 
     WebClient() : connected_at(0), last_activity(0) {}
 };
@@ -239,6 +245,15 @@ private:
     void HandleListUsers(void* ws_ptr, const std::string& token);
     void HandleGetGroups(void* ws_ptr, const std::string& token);
 
+    // Security audit trail: in-memory ring of the last 1000 events since
+    // startup (see WebService.cpp). query_audit is admin-only.
+    void HandleQueryAudit(void* ws_ptr, const std::string& msg);
+    std::string ClientIP(void* ws_ptr);
+    void AuditWeb(const std::string& event, bool warn,
+                  const std::string& actor, const std::string& role,
+                  const std::string& ip, void* ws_ptr, uint64_t device_id,
+                  std::initializer_list<std::pair<const char*, std::string>> extra = {});
+
     // Send to WebSocket
     void SendText(void* ws_ptr, const std::string& text);
     void SendBinary(void* ws_ptr, const uint8_t* data, size_t len);
@@ -388,8 +403,12 @@ private:
     std::set<uint64_t>                      m_TermPending;         // 已发 COMMAND_SHELL 待响应
     std::mutex                              m_TermMutex;
 
-    // 内部清理（已持锁版本）
+    // 内部清理（已持锁版本）。reason/actor/role/ip 仅用于审计日志；actor 为空时
-    void CloseTermSessionLocked(uint64_t device_id);
+    // 尝试从 m_Clients 反查（ws 已注销时需由调用方传入）。
+    void CloseTermSessionLocked(uint64_t device_id, const char* reason = "ws_close",
+                                const std::string& actor = std::string(),
+                                const std::string& role = std::string(),
+                                const std::string& ip = std::string());
 };
 
 // Global accessor

server/go/README.md

@@ -141,7 +141,7 @@ VSCode F5 调试时由 `sync-web-assets` preLaunchTask 自动同步。
 ./simpleremoter-server
 ```
 
-默认监听 TCP 端口 `6543`（被控设备），HTTP 端口 `8080`（浏览器 Web UI）。日志写到 `logs/server.log`。
+默认监听 TCP 端口 `6543`（被控设备），HTTP 端口 `8080`（浏览器 Web UI）。日志写到 `logs/server.log`，安全审计记录另写 `logs/audit.log`。
 
 ### 命令行参数
 
@@ -170,6 +170,7 @@ VSCode F5 调试时由 `sync-web-assets` preLaunchTask 自动同步。
 | `YAMA_USERS_FILE` | Path to the JSON file that persists non-admin web users (allowed_groups, password hash, salt). Default is `users.json` in the working directory. | `users.json` |
 | `YAMA_WEB_ALLOWED_ORIGINS` | Comma-separated WebSocket Origin allowlist for cross-origin upgrades. Empty (default) → only same-origin upgrades are accepted, which is correct when the web UI and `/ws` share a host. Add an entry per trusted PWA / dev origin. | `https://yama.example.com,https://yama-mobile.example.com` |
 | `YAMA_WEB_TRUST_PROXY` | Set to `1` only when running behind a reverse proxy you control (caddy / nginx / cloudflare). Switches client-IP extraction to use the last entry of `X-Forwarded-For` instead of `RemoteAddr`, so per-IP login rate limit sees the real client. Direct-exposure deployments MUST leave this unset — otherwise attackers can spoof the header to evade rate limits. | `1` |
+| `YAMA_AUDIT_LOG` | 安全审计日志路径（JSON lines）。默认 `logs/audit.log`；设为 `off` / `none` / `0` / `-` 关闭独立文件（审计记录仍会写入 `logs/server.log`）。审计记录带 `audit=true` 和稳定的 `event` 名，便于告警与检索。 | `/var/log/yama/audit.log` |
 | `YAMA_SSO_JWT_SECRET` | **[SSO]** Shared HS256 secret for bridging the parent portal's `auth_token` JWT into a YAMA web session via `/sso`. Must equal the upstream portal's signing key (FMS: `SERVER_PRIVATE_KEY`). **Only `admin` portal users are auto-logged-in**; other roles still need YAMA's own web login. Unset → SSO disabled, `/sso` returns 401. | `<shared-secret>` |
 
 ```bash
@@ -327,6 +328,46 @@ func main() {
 {"level":"debug","module":"Handler","time":"2025-12-19T13:17:47+01:00","message":"Heartbeat from client 1 (DESKTOP-BI6RGEJ)"}
 ```
 
+### 安全审计日志
+
+Web 端与设备端的认证、授权、远程控制操作会额外写入**独立**的 `logs/audit.log`（可由 `YAMA_AUDIT_LOG` 改路径或关闭），同时镜像到 `logs/server.log`。每行是一个 JSON 对象，固定带 `audit=true` 与 `event`，其余字段按事件携带 `actor` / `role` / `ip` / `peer_ip` / `conn` / `device_id` / `reason` 等。
+
+网页暴露到公网后，优先关注这些事件：
+
+| 事件 | 含义 |
+| ---- | ---- |
+| `web.ws.connect` / `web.ws.reject` | WebSocket 建立 / 被拒（Origin 不允许、升级失败） |
+| `web.login.success` / `web.login.failure` / `web.login.throttled` | 登录成功、失败（含 `reason`、`user_exists`）、触发限流 |
+| `web.salt.unknown_user` | `get_salt` 探测不存在的用户名（用户名枚举信号，每连接记一次） |
+| `web.auth.invalid_token` / `web.authz.denied` | 无效 token、权限不足（非 admin 调用管理命令） |
+| `web.session.resume` | 浏览器用缓存的 token 在重连后恢复会话 |
+| `web.ws.close` | 连接关闭；带 `duration_ms`、`commands` 以及 `invalid_tokens` / `login_failures` / `admin_denied` 等可疑计数 |
+| `remote.screen.start` / `.stop` / `.denied` | 远程桌面开始 / 结束（`reason`：disconnect、device_offline、ws_close、replaced）/ 被拒 |
+| `remote.terminal.start` / `.stop` / `.denied` | 远程终端会话生命周期 |
+| `remote.clipboard.get` / `.set` | 剪贴板读取 / 写入（只记字节数，**不记内容**） |
+| `remote.rdp_reset` | 远程 RDP 会话归位操作 |
+| `admin.user.create` / `admin.user.delete` / `admin.device.delete` | 管理操作（`target` / `device_id` / `mode`） |
+| `admin.audit.query` | 管理员在网页查询审计日志（记录筛选条件与命中数） |
+| `device.online` / `device.offline` | 受控设备上线 / 下线 |
+| `device.auth.success` / `.failure` / `.throttled` / `.heartbeat.success` | 设备 TCP 授权结果（**只记 passcode 长度，不记 passcode**） |
+| `device.connauth.rejected` / `device.subconn.foreign_ip` | 子连接签名失败 / 子连接来源 IP 与主连接不一致 |
+
+管理员可以在网页里直接查询：设备页工具栏的 **Audit Log** 按钮（`admin` 角色且服务端在 `caps` 中声明 `auditLog` 时显示）打开审计页面，支持按时间范围、事件（精确值或前缀，如 `web.*`）、actor、IP、device_id、关键字筛选以及“仅警告”、分页。页面读取当前 `logs/audit.log`（超大文件只扫描末尾 32 MB，并会提示；已轮转的历史文件仍用下面的 grep/jq 排查），查询动作本身记为 `admin.audit.query`。
+
+常用排查命令：
+```bash
+# 最近的登录失败与被拒操作
+grep -E '"event":"web\.(login\.failure|login\.throttled|authz\.denied|salt\.unknown_user)"' logs/audit.log | tail -50
+
+# 按来源 IP 聚合失败次数（找爆破源）
+grep '"event":"web.login.failure"' logs/audit.log | jq -r '.ip' | sort | uniq -c | sort -rn | head
+
+# 谁在什么时候开了远程桌面
+grep '"event":"remote.screen.start"' logs/audit.log | jq -c '{time,actor,role,ip,device_id}'
+```
+
+注意：鼠标 / 键盘事件不逐条记录（频率太高，会把审计日志刷爆）；审计以会话粒度（`remote.screen.*`、`remote.terminal.*`）体现操作。审计记录中的字符串字段来自客户端（用户名、User-Agent、Origin、设备名等），已做控制字符清理与长度截断，避免伪造日志行。
+
 ## 协议格式
 
 数据包格式与 C++ 版本兼容：

server/go/cmd/main.go

@@ -18,6 +18,7 @@ import (
 
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/auth"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/connection"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/devicehistory"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/licensing"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/logger"
@@ -268,7 +269,12 @@ func (h *MyHandler) rejectConnAuth(ctx *connection.Context, status byte) {
 	if err := h.srv.Send(ctx, ack); err != nil {
 		h.log.Error("ConnAuth reject send failed for conn=%d: %v", ctx.ID, err)
 	}
-	h.log.Warn("ConnAuth rejected conn=%d ip=%s status=%d", ctx.ID, ctx.GetPeerIP(), status)
+	h.log.AuditWarn("device.connauth.rejected", map[string]any{
+		"conn":      ctx.ID,
+		"ip":        ctx.GetPeerIP(),
+		"status":    status,
+		"device_id": ctx.GetInfo().ClientID,
+	})
 	_ = ctx.Close()
 }
 
@@ -306,8 +312,13 @@ func (h *MyHandler) handleTerminalStart(ctx *connection.Context, isPTY bool) {
 		// closed term_close already), or a hijack attempt from a source IP
 		// other than the device's login conn. Log the latter distinctly.
 		if mc := h.hub.MainConn(devID); mc != nil && mc.GetPeerIP() != ctx.GetPeerIP() {
-			h.log.Warn("terminal sub-conn rejected (foreign source IP): device=%s conn=%d src=%s want=%s",
+			h.log.AuditWarn("device.subconn.foreign_ip", map[string]any{
-				devID, ctx.ID, ctx.GetPeerIP(), mc.GetPeerIP())
+				"kind":      "terminal",
+				"device_id": devID,
+				"conn":      ctx.ID,
+				"ip":        ctx.GetPeerIP(),
+				"want_ip":   mc.GetPeerIP(),
+			})
 		} else {
 			h.log.Warn("orphan terminal sub-conn: device=%s conn=%d isPTY=%v",
 				devID, ctx.ID, isPTY)
@@ -349,8 +360,13 @@ func (h *MyHandler) handleBitmapInfo(ctx *connection.Context, data []byte) {
 		// MasterID from a different source IP than the device's login conn.
 		// The latter is a security signal worth surfacing distinctly.
 		if mc := h.hub.MainConn(deviceID); mc != nil && mc.GetPeerIP() != ctx.GetPeerIP() {
-			h.log.Warn("screen sub-conn rejected (foreign source IP): device=%s conn=%d src=%s want=%s",
+			h.log.AuditWarn("device.subconn.foreign_ip", map[string]any{
-				deviceID, ctx.ID, ctx.GetPeerIP(), mc.GetPeerIP())
+				"kind":      "screen",
+				"device_id": deviceID,
+				"conn":      ctx.ID,
+				"ip":        ctx.GetPeerIP(),
+				"want_ip":   mc.GetPeerIP(),
+			})
 		} else {
 			h.log.Warn("orphan screen sub-conn %d for unknown device %s; closing", ctx.ID, deviceID)
 		}
@@ -613,7 +629,11 @@ func (h *MyHandler) handleAuth(ctx *connection.Context, data []byte) {
 	// definitive answer instead of hanging, while a brute-forcer is capped.
 	ip := ctx.GetPeerIP()
 	if !h.loginLimit.Allow(ip) {
-		h.log.Warn("TOKEN_AUTH rate-limited: ip=%s conn=%d", ip, ctx.ID)
+		h.log.AuditWarn("device.auth.throttled", map[string]any{
+			"conn":   ctx.ID,
+			"ip":     ip,
+			"reason": "rate_limited",
+		})
 		resp := h.auth.BuildResponse(&auth.AuthResult{Valid: false, Message: "尝试过于频繁，请稍后再试"})
 		if err := h.srv.Send(ctx, resp); err != nil {
 			h.log.Error("Failed to send rate-limit auth response to client %d: %v", ctx.ID, err)
@@ -629,12 +649,23 @@ func (h *MyHandler) handleAuth(ctx *connection.Context, data []byte) {
 		authType = "V2"
 	}
 
+	// Device auth records are audit events (not just debug logs): a flood of
+	// failures against one address is how passcode guessing looks. The
+	// submitted passcode is NEVER logged — only its presence and length.
+	fields := map[string]any{
+		"conn":         ctx.ID,
+		"ip":           ip,
+		"auth_version": authType,
+		"device_id":    info.ClientID,
+		"computer":     info.ComputerName,
+		"sn":           result.SN,
+		"passcode_len": len(result.Passcode),
+		"has_passcode": result.Passcode != "",
+	}
 	if result.Valid {
-		h.log.Info("Auth %s success: clientID=%s computer=%s ip=%s sn=%s passcode=%s",
+		h.log.Audit("device.auth.success", fields)
-			authType, info.ClientID, info.ComputerName, ctx.GetPeerIP(), result.SN, result.Passcode)
 	} else {
-		h.log.Warn("Auth %s failed: clientID=%s computer=%s ip=%s sn=%s passcode=%s",
+		h.log.AuditWarn("device.auth.failure", fields)
-			authType, info.ClientID, info.ComputerName, ctx.GetPeerIP(), result.SN, result.Passcode)
 	}
 
 	// Build and send response
@@ -706,15 +737,22 @@ func (h *MyHandler) handleHeartbeat(ctx *connection.Context, data []byte) {
 			if !ctx.IsAuthorized.Load() {
 				ctx.IsAuthorized.Store(true)
 				info := ctx.GetInfo()
+				version := "V1"
 				if authResult.IsV2 {
-					// V2 authorization
+					version = "V2"
-					h.log.Info("Heartbeat auth V2 success: clientID=%s computer=%s ip=%s sn=%s passcode=%s",
-						info.ClientID, info.ComputerName, ctx.GetPeerIP(), authResult.SN, authResult.Passcode)
-				} else {
-					// V1 authorization
-					h.log.Info("Heartbeat auth V1 success: clientID=%s computer=%s ip=%s sn=%s passcode=%s pwdHmac=%d",
-						info.ClientID, info.ComputerName, ctx.GetPeerIP(), authResult.SN, authResult.Passcode, authResult.PwdHmac)
 				}
+				// Same redaction rule as TOKEN_AUTH: never log the passcode
+				// or the password HMAC, only that they were supplied.
+				h.log.Audit("device.auth.heartbeat.success", map[string]any{
+					"conn":         ctx.ID,
+					"ip":           ctx.GetPeerIP(),
+					"auth_version": version,
+					"device_id":    info.ClientID,
+					"computer":     info.ComputerName,
+					"sn":           authResult.SN,
+					"passcode_len": len(authResult.Passcode),
+					"has_pwd_hmac": authResult.PwdHmac != 0,
+				})
 			}
 		}
 	}
@@ -901,8 +939,30 @@ func main() {
 	logCfg.MaxAge = 30     // 30 days
 	logCfg.Compress = true
 
+	// Security audit trail: a separate JSON-lines file so login attempts,
+	// authz denials, remote-control sessions and admin mutations are not
+	// buried in debug output and can be retained / shipped independently.
+	// YAMA_AUDIT_LOG overrides the path; "off"/"none"/"0"/"-" disables the
+	// separate file (records still reach server.log).
+	auditFile := strings.TrimSpace(os.Getenv("YAMA_AUDIT_LOG"))
+	if auditFile == "" {
+		auditFile = "logs/audit.log"
+	}
+	switch strings.ToLower(auditFile) {
+	case "off", "none", "0", "-":
+		auditFile = ""
+	}
+	logCfg.AuditFile = auditFile
+	logCfg.AuditMaxSize = 100
+	logCfg.AuditMaxBackups = 20
+	logCfg.AuditMaxAge = 90
+	logCfg.AuditCompress = true
+
 	log := logger.New(logCfg)
 	log.Info("====== Copyright (c) 2026 simpleremoter.com. All rights resvered. ======")
+	if auditFile != "" {
+		log.Info("Security audit log: %s", auditFile)
+	}
 
 	// Track env vars where we fell back to a built-in default. Printed once
 	// at the end of startup so the operator sees what's in effect — vars the
@@ -931,6 +991,34 @@ func main() {
 	// the HTTP server reads from it.
 	deviceHub := hub.New()
 
+	// Persistent device history: every device that has ever logged in, so the
+	// web UI can keep showing it after it goes offline. Same working-directory
+	// convention as users.json. Retention is capped by count (newest last_seen
+	// wins) so the file and the device_list payload stay bounded.
+	devicesFile := os.Getenv("YAMA_DEVICES_FILE")
+	if devicesFile == "" {
+		devicesFile = "devices.json"
+		rememberDefault("YAMA_DEVICES_FILE", devicesFile)
+	}
+	devicesMax := 1000
+	if v := os.Getenv("YAMA_DEVICES_MAX"); v != "" {
+		if n, convErr := strconv.Atoi(v); convErr == nil && n > 0 {
+			devicesMax = n
+		} else {
+			log.Warn("Invalid YAMA_DEVICES_MAX=%q (want a positive integer); using %d", v, devicesMax)
+		}
+	}
+	deviceHistory, histErr := devicehistory.Open(devicesFile, devicesMax,
+		log.WithPrefix("History"))
+	if histErr != nil {
+		// Keep the store: live recording still works, and the next flush
+		// replaces the unreadable file. Losing old history is preferable to
+		// refusing to start the server.
+		log.Warn("Failed to load %s: %v (starting with empty history)", devicesFile, histErr)
+	}
+	deviceHub.Subscribe(deviceHistory)
+	log.Info("Device history: %s (max %d)", devicesFile, devicesMax)
+
 	// Build the CMD_MASTERSETTING signer based on env vars:
 	//   - YAMA_SIGN_PASSWORD set            → LocalSigner   (operator's own deployment;
 	//                                                       HMAC master key lives here)
@@ -1154,6 +1242,7 @@ func main() {
 	// Start HTTP server for web UI. Hub gives it read-only access to the
 	// device registry; the authenticator owns user accounts and session tokens.
 	httpSrv := web.New(*httpPort, log.WithPrefix("Web"), deviceHub, webAuth).
+		WithDeviceHistory(deviceHistory).
 		WithConfig(webCfg)
 	if err := httpSrv.Start(); err != nil {
 		log.Fatal("Failed to start HTTP server: %v", err)
@@ -1227,5 +1316,20 @@ func main() {
 	for _, srv := range servers {
 		srv.Stop()
 	}
-	log.Info("Server stopped")
+	// Devices still connected at shutdown never fire OnDeviceOffline (their
+	// TCP handlers are stopped above), so stamp them now. Otherwise a device
+	// that had been online for days would show a stale "last seen" after the
+	// restart until it reconnects.
+	for _, d := range deviceHub.ListDevices() {
+		deviceHistory.OnDeviceOffline(d.ID)
+	}
+	// Last-chance flush: the debounce timer may hold the final offline
+	// timestamps from devices that dropped while we were shutting down.
+	if err := deviceHistory.Close(); err != nil {
+		log.Warn("device history flush: %v", err)
+	}
+	log.Info("Server stopped")
+	// Flush and release the rotated log handles. Without this the last audit
+	// records can sit in lumberjack's buffered writer on shutdown.
+	_ = log.Close()
 }

server/go/devicehistory/devicehistory.go

@@ -0,0 +1,373 @@
+// Package devicehistory persists the set of devices that have ever logged in
+// to the Go server, so the web UI can keep listing them after they go offline.
+//
+// It implements hub.EventHandler and is subscribed to the hub, which means the
+// only wiring needed at startup is hub.Subscribe(store). Online events upsert
+// the record (refreshing the display fields the client reports at login) and
+// offline events merely refresh last_seen.
+//
+// Storage is a small JSON file, mirroring the wsauth users.json convention:
+// atomic temp-file + fsync + rename, loaded once at startup and written back
+// on a short debounce so a burst of reconnects doesn't rewrite it per device.
+package devicehistory
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"sync"
+	"time"
+
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/logger"
+)
+
+const (
+	// fileVersion lets a future release migrate the on-disk shape. Unknown
+	// versions are still parsed best-effort; only structurally invalid JSON
+	// makes Open fail.
+	fileVersion = 1
+
+	// flushDelay coalesces updates. Device logins/disconnects are sparse, but
+	// a server restart makes every agent reconnect at once; without the
+	// debounce that would be one file write per device.
+	flushDelay = 500 * time.Millisecond
+)
+
+// Record is one persisted device. The fields mirror hub.DeviceInfo so the
+// offline list can be rendered with the same front-end card code; only the
+// fields that are stable across sessions are kept (RTT / active window are
+// live-only and would be stale noise on an offline card).
+type Record struct {
+	ID          string `json:"id"`
+	Name        string `json:"name"`
+	Group       string `json:"group,omitempty"`
+	Version     string `json:"version,omitempty"`
+	Capability  string `json:"capability,omitempty"`
+	OS          string `json:"os,omitempty"`
+	CPU         string `json:"cpu,omitempty"`
+	FilePath    string `json:"file_path,omitempty"`
+	InstallTime string `json:"install_time,omitempty"`
+	Location    string `json:"location,omitempty"`
+	PeerIP      string `json:"peer_ip,omitempty"`
+	IP          string `json:"ip,omitempty"`
+	Screen      string `json:"screen,omitempty"`
+
+	FirstSeen int64 `json:"first_seen"`
+	LastSeen  int64 `json:"last_seen"`
+}
+
+type fileShape struct {
+	Version int                `json:"version"`
+	Devices map[string]*Record `json:"devices"`
+}
+
+// Store is the in-memory device history plus its backing file. Safe for
+// concurrent use.
+type Store struct {
+	path string
+	max  int // 0 = unlimited
+	log  *logger.Logger
+
+	mu      sync.Mutex
+	devices map[string]*Record
+	// online is derived from hub events and used only by pruning: a device
+	// that is still connected must keep its record even if its last login is
+	// older than the 1000th offline device's. Not persisted — after a restart
+	// every device is offline until it reconnects.
+	online map[string]bool
+	dirty  bool
+	timer  *time.Timer
+}
+
+// Open loads the history at path. A missing file is an empty history, not an
+// error. If the file exists but cannot be parsed, the returned store is still
+// usable (empty) along with the error, so callers can log and continue — the
+// next flush will replace the corrupt file.
+func Open(path string, max int, log *logger.Logger) (*Store, error) {
+	s := newStore(path, max, log)
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return s, nil
+		}
+		return s, err
+	}
+	var f fileShape
+	if err := json.Unmarshal(data, &f); err != nil {
+		return s, fmt.Errorf("parse %s: %w", path, err)
+	}
+	for id, r := range f.Devices {
+		if r == nil {
+			continue
+		}
+		// The map key is authoritative; tolerate records written by a
+		// future/older shape that omitted or disagreed with the id field.
+		r.ID = id
+		s.devices[id] = r
+	}
+	s.pruneLocked()
+	return s, nil
+}
+
+// New returns an empty store for path without touching disk. Useful when Open
+// failed and the caller still wants live recording to work.
+func New(path string, max int, log *logger.Logger) *Store {
+	return newStore(path, max, log)
+}
+
+func newStore(path string, max int, log *logger.Logger) *Store {
+	return &Store{
+		path:    path,
+		max:     max,
+		log:     log,
+		devices: make(map[string]*Record),
+		online:  make(map[string]bool),
+	}
+}
+
+// OnDeviceOnline records a device that just logged in. It refreshes every
+// display field because the agent reports its current name/group/version at
+// each login, and preserves first_seen across reconnects.
+func (s *Store) OnDeviceOnline(d hub.DeviceInfo) {
+	s.upsertAt(d, time.Now())
+}
+
+func (s *Store) upsertAt(d hub.DeviceInfo, at time.Time) {
+	if d.ID == "" {
+		return
+	}
+	now := at.Unix()
+
+	s.mu.Lock()
+	rec, ok := s.devices[d.ID]
+	if !ok {
+		rec = &Record{ID: d.ID, FirstSeen: now}
+		s.devices[d.ID] = rec
+	}
+	if rec.FirstSeen == 0 {
+		rec.FirstSeen = now
+	}
+	rec.Name = d.Name
+	rec.Group = d.Group
+	rec.Version = d.Version
+	rec.Capability = d.Capability
+	rec.OS = d.OS
+	rec.CPU = d.CPU
+	rec.FilePath = d.FilePath
+	rec.InstallTime = d.InstallTime
+	rec.Location = d.Location
+	rec.PeerIP = d.PeerIP
+	rec.IP = d.IP
+	rec.Screen = d.Screen
+	rec.LastSeen = now
+	s.online[d.ID] = true
+
+	s.pruneLocked()
+	s.markDirtyLocked()
+	s.mu.Unlock()
+}
+
+// OnDeviceOffline refreshes last_seen. The record was created when the device
+// logged in; an unknown ID is ignored (e.g. a device rejected by signing never
+// reaches the hub).
+func (s *Store) OnDeviceOffline(id string) {
+	if id == "" {
+		return
+	}
+	s.offlineAt(id, time.Now())
+}
+
+func (s *Store) offlineAt(id string, at time.Time) {
+	s.mu.Lock()
+	delete(s.online, id)
+	if rec, ok := s.devices[id]; ok {
+		rec.LastSeen = at.Unix()
+		s.markDirtyLocked()
+	}
+	s.mu.Unlock()
+}
+
+// The remaining EventHandler methods are not relevant to device history.
+func (s *Store) OnDeviceUpdate(string, int, string)  {}
+func (s *Store) OnScreenFrame(string, []byte, bool)  {}
+func (s *Store) OnResolutionChange(string, int, int) {}
+func (s *Store) OnCursorChange(string, byte)         {}
+func (s *Store) OnClipboardText(string, string)      {}
+func (s *Store) OnTerminalReady(string, bool)        {}
+func (s *Store) OnTerminalData(string, []byte)       {}
+func (s *Store) OnTerminalClosed(string, string)     {}
+
+// Offline returns the records whose IDs are not in online, newest last_seen
+// first, converted to the hub's device payload shape with Online=false.
+//
+// Callers pass the hub's current online snapshot; the store deliberately does
+// not know which device is online, so a reconnect that re-registers the same
+// ID can never produce a duplicate row.
+func (s *Store) Offline(online map[string]struct{}) []hub.DeviceInfo {
+	s.mu.Lock()
+	out := make([]hub.DeviceInfo, 0, len(s.devices))
+	for id, rec := range s.devices {
+		if _, ok := online[id]; ok {
+			continue
+		}
+		out = append(out, hub.DeviceInfo{
+			ID:          rec.ID,
+			Name:        rec.Name,
+			Group:       rec.Group,
+			Version:     rec.Version,
+			Capability:  rec.Capability,
+			OS:          rec.OS,
+			CPU:         rec.CPU,
+			FilePath:    rec.FilePath,
+			InstallTime: rec.InstallTime,
+			Location:    rec.Location,
+			IP:          rec.IP,
+			PeerIP:      rec.PeerIP,
+			Screen:      rec.Screen,
+			LastSeen:    rec.LastSeen,
+			Online:      false,
+		})
+	}
+	s.mu.Unlock()
+
+	sort.Slice(out, func(i, j int) bool {
+		if out[i].LastSeen != out[j].LastSeen {
+			return out[i].LastSeen > out[j].LastSeen
+		}
+		return out[i].ID < out[j].ID
+	})
+	return out
+}
+
+// Remove deletes the persisted record for id and reports whether one existed.
+// This is the web UI's explicit "delete" for an offline device: an offline
+// record has no live agent to uninstall, so forgetting it is all "delete" can
+// mean. The caller decides when removal is appropriate; the store does not
+// refuse to drop a record that happens to be marked online.
+func (s *Store) Remove(id string) bool {
+	if id == "" {
+		return false
+	}
+	s.mu.Lock()
+	_, existed := s.devices[id]
+	if existed {
+		delete(s.devices, id)
+		delete(s.online, id)
+		s.markDirtyLocked()
+	}
+	s.mu.Unlock()
+	return existed
+}
+
+// Flush writes the current state synchronously. Normally the debounced timer
+// does this; Flush exists for tests and graceful shutdown.
+func (s *Store) Flush() error {
+	s.mu.Lock()
+	if s.timer != nil {
+		s.timer.Stop()
+		s.timer = nil
+	}
+	if !s.dirty {
+		s.mu.Unlock()
+		return nil
+	}
+	s.dirty = false
+	data, err := s.marshalLocked()
+	s.mu.Unlock()
+	if err != nil {
+		return err
+	}
+	if err := writeAtomic(s.path, data); err != nil {
+		s.mu.Lock()
+		s.dirty = true
+		s.mu.Unlock()
+		return err
+	}
+	return nil
+}
+
+// Close stops the debounce timer and flushes pending changes.
+func (s *Store) Close() error {
+	return s.Flush()
+}
+
+func (s *Store) markDirtyLocked() {
+	s.dirty = true
+	if s.timer == nil {
+		s.timer = time.AfterFunc(flushDelay, s.flush)
+	}
+}
+
+func (s *Store) flush() {
+	if err := s.Flush(); err != nil && s.log != nil {
+		s.log.Error("Failed to persist device history to %s: %v", s.path, err)
+	}
+}
+
+func (s *Store) marshalLocked() ([]byte, error) {
+	f := fileShape{Version: fileVersion, Devices: s.devices}
+	return json.MarshalIndent(f, "", "  ")
+}
+
+// pruneLocked keeps the max most-recently-seen records. It runs after every
+// online upsert, which is the only path that can grow the map; the O(n log n)
+// sort only happens when the cap is actually exceeded.
+func (s *Store) pruneLocked() {
+	if s.max <= 0 || len(s.devices) <= s.max {
+		return
+	}
+	ids := make([]string, 0, len(s.devices))
+	for id := range s.devices {
+		ids = append(ids, id)
+	}
+	sort.Slice(ids, func(i, j int) bool {
+		oi, oj := s.online[ids[i]], s.online[ids[j]]
+		if oi != oj {
+			return !oi // evict offline records before online ones
+		}
+		return s.devices[ids[i]].LastSeen < s.devices[ids[j]].LastSeen
+	})
+	for _, id := range ids[:len(ids)-s.max] {
+		delete(s.devices, id)
+	}
+}
+
+// writeAtomic mirrors wsauth.writeUsersFile: temp file in the same directory,
+// fsync, then rename over the destination.
+func writeAtomic(path string, data []byte) error {
+	dir := filepath.Dir(path)
+	if dir != "" {
+		if err := os.MkdirAll(dir, 0o755); err != nil {
+			return err
+		}
+	}
+	tmp, err := os.CreateTemp(dir, "devices-*.json.tmp")
+	if err != nil {
+		return err
+	}
+	tmpName := tmp.Name()
+	if _, err := tmp.Write(data); err != nil {
+		_ = tmp.Close()
+		_ = os.Remove(tmpName)
+		return err
+	}
+	if err := tmp.Sync(); err != nil {
+		_ = tmp.Close()
+		_ = os.Remove(tmpName)
+		return err
+	}
+	if err := tmp.Close(); err != nil {
+		_ = os.Remove(tmpName)
+		return err
+	}
+	if err := os.Rename(tmpName, path); err != nil {
+		_ = os.Remove(tmpName)
+		return err
+	}
+	return nil
+}

server/go/devicehistory/devicehistory_test.go

@@ -0,0 +1,263 @@
+package devicehistory
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/connection"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
+)
+
+func testDevice(id, name string) hub.DeviceInfo {
+	return hub.DeviceInfo{
+		ID:      id,
+		Name:    name,
+		Group:   "office",
+		Version: "1.2.3",
+		OS:      "Windows 11",
+		IP:      "203.0.113.7",
+		PeerIP:  "198.51.100.9",
+		Screen:  "1:1920*1080",
+		Online:  true,
+	}
+}
+
+func TestStoreRecordsLifecycleViaHub(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "devices.json")
+	s, err := Open(path, 1000, nil)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	t.Cleanup(func() { _ = s.Close() })
+
+	h := hub.New()
+	h.Subscribe(s)
+
+	h.Register(&hub.Device{ID: "dev-1", Name: "PC-1", Group: "office"},
+		&connection.Context{RemoteAddr: "198.51.100.9:5000"})
+
+	// The device is online, so it must not appear in the offline list.
+	if got := s.Offline(map[string]struct{}{"dev-1": {}}); len(got) != 0 {
+		t.Fatalf("offline while online = %d, want 0", len(got))
+	}
+
+	h.Unregister("dev-1")
+
+	off := s.Offline(nil)
+	if len(off) != 1 {
+		t.Fatalf("offline entries = %d, want 1", len(off))
+	}
+	d := off[0]
+	if d.ID != "dev-1" || d.Name != "PC-1" || d.Group != "office" {
+		t.Fatalf("offline device = %+v", d)
+	}
+	if d.Online {
+		t.Fatal("offline entry marked online")
+	}
+	if d.LastSeen == 0 {
+		t.Fatal("last_seen not set")
+	}
+}
+
+func TestStorePersistsAndPreservesFirstSeen(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "devices.json")
+	s, err := Open(path, 1000, nil)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+
+	first := time.Unix(1_700_000_000, 0)
+	s.upsertAt(testDevice("dev-1", "old-name"), first)
+	// A later login refreshes display fields and last_seen but keeps first_seen.
+	s.upsertAt(testDevice("dev-1", "new-name"), first.Add(time.Hour))
+	if err := s.Flush(); err != nil {
+		t.Fatalf("Flush: %v", err)
+	}
+	_ = s.Close()
+
+	reopened, err := Open(path, 1000, nil)
+	if err != nil {
+		t.Fatalf("reopen: %v", err)
+	}
+	t.Cleanup(func() { _ = reopened.Close() })
+
+	reopened.mu.Lock()
+	rec := reopened.devices["dev-1"]
+	reopened.mu.Unlock()
+	if rec == nil {
+		t.Fatal("record not persisted")
+	}
+	if rec.Name != "new-name" {
+		t.Fatalf("name = %q, want new-name", rec.Name)
+	}
+	if rec.FirstSeen != first.Unix() {
+		t.Fatalf("first_seen = %d, want %d", rec.FirstSeen, first.Unix())
+	}
+	if rec.LastSeen != first.Add(time.Hour).Unix() {
+		t.Fatalf("last_seen = %d, want %d", rec.LastSeen, first.Add(time.Hour).Unix())
+	}
+}
+
+func TestStorePrunesOldest(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "devices.json")
+	s, err := Open(path, 2, nil)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	t.Cleanup(func() { _ = s.Close() })
+
+	base := time.Unix(1_700_000_000, 0)
+	s.upsertAt(testDevice("a", "A"), base)
+	s.upsertAt(testDevice("b", "B"), base.Add(time.Minute))
+	s.upsertAt(testDevice("c", "C"), base.Add(2*time.Minute))
+
+	s.mu.Lock()
+	_, hasA := s.devices["a"]
+	_, hasC := s.devices["c"]
+	n := len(s.devices)
+	s.mu.Unlock()
+	if n != 2 || hasA || !hasC {
+		t.Fatalf("after prune: n=%d hasA=%v hasC=%v, want 2/false/true", n, hasA, hasC)
+	}
+}
+
+func TestPruneEvictsOfflineBeforeOnline(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "devices.json")
+	s, err := Open(path, 2, nil)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	t.Cleanup(func() { _ = s.Close() })
+
+	base := time.Unix(1_700_000_000, 0)
+	s.upsertAt(testDevice("online-old", "Old"), base)
+	s.upsertAt(testDevice("offline-new", "Gone"), base.Add(time.Minute))
+	s.offlineAt("offline-new", base.Add(2*time.Minute))
+	// This upsert exceeds the cap; the offline record must be evicted before
+	// the still-connected device, even though its last_seen is newer.
+	s.upsertAt(testDevice("online-2", "New"), base.Add(3*time.Minute))
+
+	s.mu.Lock()
+	_, hasOld := s.devices["online-old"]
+	_, hasGone := s.devices["offline-new"]
+	_, hasNew := s.devices["online-2"]
+	n := len(s.devices)
+	s.mu.Unlock()
+	if n != 2 || !hasOld || hasGone || !hasNew {
+		t.Fatalf("after prune: n=%d hasOld=%v hasGone=%v hasNew=%v", n, hasOld, hasGone, hasNew)
+	}
+}
+
+func TestStoreOfflineSortedNewestFirst(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "devices.json")
+	s, err := Open(path, 1000, nil)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	t.Cleanup(func() { _ = s.Close() })
+
+	base := time.Unix(1_700_000_000, 0)
+	s.upsertAt(testDevice("old", "Old"), base)
+	s.upsertAt(testDevice("new", "New"), base.Add(time.Hour))
+
+	off := s.Offline(nil)
+	if len(off) != 2 || off[0].ID != "new" || off[1].ID != "old" {
+		t.Fatalf("offline order = %+v, want new then old", off)
+	}
+}
+
+func TestOpenCorruptFileStartsEmptyAndRecovers(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "devices.json")
+	if err := os.WriteFile(path, []byte("{not json"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	s, err := Open(path, 1000, nil)
+	if err == nil {
+		t.Fatal("Open corrupt file: want error, got nil")
+	}
+	if len(s.devices) != 0 {
+		t.Fatalf("corrupt load produced %d records, want 0", len(s.devices))
+	}
+	t.Cleanup(func() { _ = s.Close() })
+
+	s.upsertAt(testDevice("dev-1", "PC-1"), time.Unix(1_700_000_000, 0))
+	if err := s.Flush(); err != nil {
+		t.Fatalf("Flush after corrupt load: %v", err)
+	}
+
+	reopened, err := Open(path, 1000, nil)
+	if err != nil {
+		t.Fatalf("reopen: %v", err)
+	}
+	t.Cleanup(func() { _ = reopened.Close() })
+	if len(reopened.devices) != 1 {
+		t.Fatalf("records after recovery = %d, want 1", len(reopened.devices))
+	}
+}
+
+func TestStoreRemovePersistsDeletion(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "devices.json")
+	s, err := Open(path, 1000, nil)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+
+	base := time.Unix(1_700_000_000, 0)
+	s.upsertAt(testDevice("gone", "Gone"), base)
+	s.upsertAt(testDevice("kept", "Kept"), base.Add(time.Minute))
+
+	if !s.Remove("gone") {
+		t.Fatal("Remove existing record = false, want true")
+	}
+	if s.Remove("gone") {
+		t.Fatal("Remove missing record = true, want false")
+	}
+	if got := s.Offline(nil); len(got) != 1 || got[0].ID != "kept" {
+		t.Fatalf("offline after remove = %+v, want only kept", got)
+	}
+	if err := s.Flush(); err != nil {
+		t.Fatalf("Flush: %v", err)
+	}
+	_ = s.Close()
+
+	reopened, err := Open(path, 1000, nil)
+	if err != nil {
+		t.Fatalf("reopen: %v", err)
+	}
+	t.Cleanup(func() { _ = reopened.Close() })
+	if _, ok := reopened.devices["gone"]; ok {
+		t.Fatal("removed record came back after reload")
+	}
+	if _, ok := reopened.devices["kept"]; !ok {
+		t.Fatal("kept record missing after reload")
+	}
+}
+
+func TestFlushLeavesNoTempFiles(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "devices.json")
+	s, err := Open(path, 1000, nil)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	t.Cleanup(func() { _ = s.Close() })
+
+	s.upsertAt(testDevice("dev-1", "PC-1"), time.Unix(1_700_000_000, 0))
+	if err := s.Flush(); err != nil {
+		t.Fatalf("Flush: %v", err)
+	}
+
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, e := range entries {
+		if strings.HasSuffix(e.Name(), ".tmp") {
+			t.Fatalf("leftover temp file: %s", e.Name())
+		}
+	}
+}

server/go/hub/hub.go

@@ -165,6 +165,9 @@ type DeviceInfo struct {
 	ActiveWindow string `json:"activeWindow,omitempty"`
 	ConnectedAt  int64  `json:"connected_at"`
 	Online       bool   `json:"online"`
+	// LastSeen is unix seconds of the last login/disconnect. Only populated
+	// for offline entries in device_list; online devices leave it zero.
+	LastSeen int64 `json:"last_seen,omitempty"`
 }
 
 // EventHandler receives notifications about device lifecycle, per-tick live
@@ -240,6 +243,17 @@ func (h *Hub) SetSender(fn SendFunc) {
 	h.sender = fn
 }
 
+// IsOnline reports whether id is currently registered with a live main
+// connection. Callers that need to choose between an online-only command and
+// an offline bookkeeping action should check this first; SendToDevice can
+// still turn into ErrDeviceOffline if the device drops in between.
+func (h *Hub) IsOnline(id string) bool {
+	h.mu.RLock()
+	d, ok := h.devices[id]
+	h.mu.RUnlock()
+	return ok && d.conn != nil
+}
+
 // SendToDevice forwards an already-formed command payload to the device's
 // main connection. data should be the raw command bytes (the sender takes
 // care of framing / compression at the protocol layer).

server/go/logger/logger.go

@@ -1,10 +1,12 @@
 package logger
 
 import (
+	"fmt"
 	"io"
 	"os"
 	"path/filepath"
-	"time"
+	"strings"
+	"unicode/utf8"
 
 	"github.com/rs/zerolog"
 	"gopkg.in/natefinch/lumberjack.v2"
@@ -24,6 +26,13 @@ const (
 // Logger wraps zerolog.Logger
 type Logger struct {
 	zl zerolog.Logger
+	// audit is a second, file-only logger used for security audit records.
+	// It writes JSON lines to AuditFile so audit data is not buried in
+	// debug/operational output and can be retained independently.
+	audit        zerolog.Logger
+	auditEnabled bool
+	auditPath    string // "" when the separate audit file is disabled
+	closers      []io.Closer
 }
 
 // Config holds logger configuration
@@ -42,6 +51,19 @@ type Config struct {
 	MaxAge int
 	// Compress enables gzip compression for rotated files
 	Compress bool
+
+	// AuditFile is the dedicated security-audit log path ("" disables the
+	// separate audit file; audit records still go to the main log). Audit
+	// records are JSON lines with audit=true, event=<name>, and contextual
+	// fields such as actor/role/ip/device_id.
+	AuditFile string
+	// AuditMaxSize / AuditMaxBackups / AuditMaxAge tune audit rotation.
+	// Zero values pick 100 MB / 20 files / 90 days.
+	AuditMaxSize    int
+	AuditMaxBackups int
+	AuditMaxAge     int
+	// AuditCompress enables gzip compression for rotated audit files.
+	AuditCompress bool
 }
 
 // DefaultConfig returns default configuration
@@ -60,6 +82,7 @@ func DefaultConfig() Config {
 // New creates a new logger with config
 func New(cfg Config) *Logger {
 	var writers []io.Writer
+	var closers []io.Closer
 
 	// Console output with color
 	if cfg.Console {
@@ -87,6 +110,7 @@ func New(cfg Config) *Logger {
 			LocalTime:  true,
 		}
 		writers = append(writers, fileWriter)
+		closers = append(closers, fileWriter)
 	}
 
 	// Combine writers
@@ -106,14 +130,78 @@ func New(cfg Config) *Logger {
 		Timestamp().
 		Logger()
 
-	return &Logger{zl: zl}
+	l := &Logger{zl: zl, closers: closers}
+
+	if cfg.AuditFile != "" {
+		dir := filepath.Dir(cfg.AuditFile)
+		if dir != "" && dir != "." {
+			_ = os.MkdirAll(dir, 0755)
+		}
+		maxSize := cfg.AuditMaxSize
+		if maxSize <= 0 {
+			maxSize = 100
+		}
+		maxBackups := cfg.AuditMaxBackups
+		if maxBackups <= 0 {
+			maxBackups = 20
+		}
+		maxAge := cfg.AuditMaxAge
+		if maxAge <= 0 {
+			maxAge = 90
+		}
+		auditWriter := &lumberjack.Logger{
+			Filename:   cfg.AuditFile,
+			MaxSize:    maxSize,
+			MaxBackups: maxBackups,
+			MaxAge:     maxAge,
+			Compress:   cfg.AuditCompress,
+			LocalTime:  true,
+		}
+		l.audit = zerolog.New(auditWriter).
+			Level(zerolog.InfoLevel).
+			With().
+			Timestamp().
+			Logger()
+		l.auditEnabled = true
+		l.auditPath = cfg.AuditFile
+		l.closers = append(l.closers, auditWriter)
+	}
+
+	return l
+}
+
+// Close releases any file handles owned by the logger. Safe to call multiple
+// times. Loggers derived with WithPrefix share the base logger's files but do
+// not own them, so call Close on the logger returned by New.
+func (l *Logger) Close() error {
+	if l == nil {
+		return nil
+	}
+	for _, c := range l.closers {
+		_ = c.Close()
+	}
+	l.closers = nil
+	return nil
 }
 
 // WithPrefix returns a new logger with a prefix field
 func (l *Logger) WithPrefix(prefix string) *Logger {
-	return &Logger{
+	n := &Logger{zl: l.zl.With().Str("module", prefix).Logger(), auditPath: l.auditPath}
-		zl: l.zl.With().Str("module", prefix).Logger(),
+	if l.auditEnabled {
+		n.audit = l.audit.With().Str("module", prefix).Logger()
+		n.auditEnabled = true
 	}
+	return n
+}
+
+// AuditPath returns the path of the dedicated audit log file, or "" when the
+// separate audit file is disabled (audit records then only reach the main log).
+// Derived loggers (WithPrefix) report the same path.
+func (l *Logger) AuditPath() string {
+	if l == nil {
+		return ""
+	}
+	return l.auditPath
 }
 
 // Debug logs a debug message
@@ -151,21 +239,102 @@ func (l *Logger) GetLevel() Level {
 	return l.zl.GetLevel()
 }
 
-// ClientEvent logs client online/offline events
+// ClientEvent logs client online/offline events as audit records.
 func (l *Logger) ClientEvent(event string, clientID uint64, ip string, extra ...string) {
-	e := l.zl.Info().
+	// clientID is the TCP connection id; the device's stable YAMA id arrives
-		Str("event", event).
+	// as the "clientID" extra and is normalized to device_id so every audit
-		Uint64("client_id", clientID).
+	// record uses the same field names (conn / device_id).
-		Str("ip", ip).
+	fields := map[string]any{
-		Time("time", time.Now())
+		"conn": clientID,
-
+		"ip":   ip,
-	if len(extra) >= 2 {
+	}
 	for i := 0; i+1 < len(extra); i += 2 {
-			e = e.Str(extra[i], extra[i+1])
+		key := extra[i]
+		if key == "clientID" {
+			key = "device_id"
+		}
+		fields[key] = extra[i+1]
+	}
+	l.Audit("device."+event, fields)
+}
+
+// Audit writes one security-audit record at info level.
+func (l *Logger) Audit(event string, fields map[string]any) {
+	l.AuditAt(LevelInfo, event, fields)
+}
+
+// AuditWarn writes one security-audit record at warn level. Use it for
+// rejected / failed security-relevant operations.
+func (l *Logger) AuditWarn(event string, fields map[string]any) {
+	l.AuditAt(LevelWarn, event, fields)
+}
+
+// AuditAt writes a security-audit record to the dedicated audit file (when
+// configured) and mirrors it to the main logger so operators tailing
+// server.log still see security events. event is a stable dotted name such
+// as "web.login.failure"; fields carry actor/role/ip/device_id/reason.
+//
+// Untrusted string values (usernames, User-Agent, Origin, device strings)
+// are sanitized: control characters are replaced so they cannot forge log
+// lines, and long values are truncated.
+func (l *Logger) AuditAt(level Level, event string, fields map[string]any) {
+	if l == nil {
+		return
+	}
+	clean := make(map[string]any, len(fields)+2)
+	for k, v := range fields {
+		clean[k] = sanitizeAuditValue(v)
+	}
+	clean["audit"] = true
+	clean["event"] = event
+
+	if l.auditEnabled {
+		l.audit.WithLevel(level).Fields(clean).Msg("audit")
+	}
+	l.zl.WithLevel(level).Fields(clean).Msg("audit")
+}
+
+// maxAuditValueLen bounds untrusted log values (runes). A 1 MB WebSocket
+// frame could otherwise be reflected verbatim into every audit line.
+const maxAuditValueLen = 512
+
+// maxAuditValueBytes is the pre-sanitization byte cap. It keeps a single
+// hostile value from allocating an unbounded rune slice before truncation.
+const maxAuditValueBytes = 4096
+
+func sanitizeAuditValue(v any) any {
+	switch x := v.(type) {
+	case string:
+		return sanitizeAuditString(x)
+	case []byte:
+		return sanitizeAuditString(string(x))
+	case error:
+		return sanitizeAuditString(x.Error())
+	case fmt.Stringer:
+		return sanitizeAuditString(x.String())
+	default:
+		// Numeric/bool values are code-controlled and log-safe.
+		return v
 	}
 }
 
-	e.Msg("")
+func sanitizeAuditString(s string) string {
+	if len(s) > maxAuditValueBytes {
+		s = s[:maxAuditValueBytes]
+	}
+	s = strings.Map(func(r rune) rune {
+		// C0 controls, DEL, and Unicode line/paragraph separators can be
+		// used to forge or visually split log lines in console output.
+		if r < 0x20 || r == 0x7f || r == 0x2028 || r == 0x2029 {
+			return ' '
+		}
+		return r
+	}, s)
+	if utf8.RuneCountInString(s) > maxAuditValueLen {
+		r := []rune(s)
+		s = string(r[:maxAuditValueLen])
+	}
+	return s
 }
 
 // default global logger

server/go/logger/logger_test.go

@@ -0,0 +1,156 @@
+package logger
+
+import (
+	"bufio"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// readAuditLines parses logs/audit.log-style JSON lines. Callers assert on
+// individual records rather than raw text so field ordering is irrelevant.
+func readAuditLines(t *testing.T, path string) []map[string]any {
+	t.Helper()
+	f, err := os.Open(path)
+	if err != nil {
+		t.Fatalf("open audit log: %v", err)
+	}
+	defer f.Close()
+
+	var out []map[string]any
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		line := strings.TrimSpace(sc.Text())
+		if line == "" {
+			continue
+		}
+		var m map[string]any
+		if err := json.Unmarshal([]byte(line), &m); err != nil {
+			t.Fatalf("audit line is not JSON: %q: %v", line, err)
+		}
+		out = append(out, m)
+	}
+	if err := sc.Err(); err != nil {
+		t.Fatalf("scan audit log: %v", err)
+	}
+	return out
+}
+
+func TestAuditWritesDedicatedFileAndMirrorsMainLog(t *testing.T) {
+	dir := t.TempDir()
+	auditPath := filepath.Join(dir, "audit.log")
+	mainPath := filepath.Join(dir, "server.log")
+
+	l := New(Config{
+		Level:     LevelInfo,
+		Console:   false,
+		File:      mainPath,
+		AuditFile: auditPath,
+	})
+	t.Cleanup(func() { _ = l.Close() })
+
+	l.Audit("web.login.success", map[string]any{
+		"actor": "admin",
+		"role":  "admin",
+		"ip":    "203.0.113.9",
+	})
+
+	lines := readAuditLines(t, auditPath)
+	if len(lines) != 1 {
+		t.Fatalf("audit lines = %d, want 1", len(lines))
+	}
+	rec := lines[0]
+	if rec["audit"] != true {
+		t.Errorf("audit = %v, want true", rec["audit"])
+	}
+	if rec["event"] != "web.login.success" {
+		t.Errorf("event = %v", rec["event"])
+	}
+	if rec["actor"] != "admin" || rec["role"] != "admin" || rec["ip"] != "203.0.113.9" {
+		t.Errorf("fields = %+v", rec)
+	}
+	if _, ok := rec["time"]; !ok {
+		t.Error("record has no timestamp")
+	}
+
+	// The same record must reach server.log so operators tailing one file
+	// still see security events.
+	mainLines := readAuditLines(t, mainPath)
+	found := false
+	for _, m := range mainLines {
+		if m["event"] == "web.login.success" && m["audit"] == true {
+			found = true
+		}
+	}
+	if !found {
+		t.Errorf("audit record not mirrored to main log: %+v", mainLines)
+	}
+}
+
+func TestAuditSanitizesUntrustedValues(t *testing.T) {
+	dir := t.TempDir()
+	auditPath := filepath.Join(dir, "audit.log")
+	l := New(Config{Console: false, File: filepath.Join(dir, "server.log"), AuditFile: auditPath})
+	t.Cleanup(func() { _ = l.Close() })
+
+	l.Audit("web.login.failure", map[string]any{
+		// Newlines must not be able to forge extra log lines.
+		"username": "evil\n{\"audit\":true,\"event\":\"web.login.success\"}",
+		"ua":       strings.Repeat("A", maxAuditValueLen+50),
+	})
+
+	lines := readAuditLines(t, auditPath)
+	if len(lines) != 1 {
+		t.Fatalf("audit lines = %d, want 1 (newline forged a record?)", len(lines))
+	}
+	username, _ := lines[0]["username"].(string)
+	if strings.ContainsAny(username, "\n\r") {
+		t.Errorf("username still contains a newline: %q", username)
+	}
+	if !strings.Contains(username, `{"audit":true`) {
+		t.Errorf("username content lost: %q", username)
+	}
+	ua, _ := lines[0]["ua"].(string)
+	if got := len([]rune(ua)); got != maxAuditValueLen {
+		t.Errorf("ua rune length = %d, want %d", got, maxAuditValueLen)
+	}
+}
+
+func TestAuditDisabledFileStillLogsToMain(t *testing.T) {
+	dir := t.TempDir()
+	mainPath := filepath.Join(dir, "server.log")
+	l := New(Config{Console: false, File: mainPath}) // no AuditFile
+	t.Cleanup(func() { _ = l.Close() })
+
+	l.AuditWarn("web.authz.denied", map[string]any{"role": "viewer"})
+
+	lines := readAuditLines(t, mainPath)
+	if len(lines) != 1 || lines[0]["event"] != "web.authz.denied" {
+		t.Fatalf("main log lines = %+v", lines)
+	}
+	if _, err := os.Stat(filepath.Join(dir, "audit.log")); !os.IsNotExist(err) {
+		t.Errorf("audit.log unexpectedly created: %v", err)
+	}
+}
+
+func TestClientEventEmitsDeviceAudit(t *testing.T) {
+	dir := t.TempDir()
+	auditPath := filepath.Join(dir, "audit.log")
+	l := New(Config{Console: false, File: filepath.Join(dir, "server.log"), AuditFile: auditPath})
+	t.Cleanup(func() { _ = l.Close() })
+
+	l.ClientEvent("online", 42, "198.51.100.7", "clientID", "abc", "computer", "PC-01")
+
+	lines := readAuditLines(t, auditPath)
+	if len(lines) != 1 {
+		t.Fatalf("audit lines = %d, want 1", len(lines))
+	}
+	if lines[0]["event"] != "device.online" {
+		t.Errorf("event = %v, want device.online", lines[0]["event"])
+	}
+	if lines[0]["device_id"] != "abc" {
+		t.Errorf("device_id = %v", lines[0]["device_id"])
+	}
+}

server/go/protocol/commands.go

@@ -110,6 +110,7 @@ const (
 	CommandScreenSetClipboard byte = 25  // COMMAND_SCREEN_SET_CLIPBOARD - set remote clipboard [25][GBK text]
 	CommandNext               byte = 30  // COMMAND_NEXT - "control-side dialog is open, you may stream"
 	CommandShell              byte = 40  // COMMAND_SHELL - ask device to open a shell sub-connection
+	CommandUninstall          byte = 63  // TOKEN_UNINSTALL - uninstall the host agent (single byte)
 	CommandTerminalRsize      byte = 81  // CMD_TERMINAL_RESIZE - [cmd:1][cols:2 LE][rows:2 LE]
 	CmdRestoreConsole         byte = 82  // CMD_RESTORE_CONSOLE - RDP session "归位": switch back to the console session and restart capture
 	CommandScreenKeyframeReq  byte = 169 // COMMAND_SCREEN_KEYFRAME_REQ - force the client to emit an IDR immediately

server/go/web/audit.go

@@ -0,0 +1,171 @@
+package web
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"net/http"
+	"time"
+)
+
+// Stable audit event names. Keep these stable: operators build alerts and
+// dashboards on them. Every record also carries audit=true.
+const (
+	auditWSConnect  = "web.ws.connect"
+	auditWSReject   = "web.ws.reject"
+	auditWSClose    = "web.ws.close"
+	auditLoginOK    = "web.login.success"
+	auditLoginFail  = "web.login.failure"
+	auditLoginThrot = "web.login.throttled"
+	auditSession    = "web.session.resume"
+	auditBadToken   = "web.auth.invalid_token"
+	auditDenied     = "web.authz.denied"
+	auditUnknownCmd = "web.command.unknown"
+	auditSaltProbe  = "web.salt.unknown_user"
+
+	auditScreenStart  = "remote.screen.start"
+	auditScreenStop   = "remote.screen.stop"
+	auditScreenDenied = "remote.screen.denied"
+	auditTermStart    = "remote.terminal.start"
+	auditTermStop     = "remote.terminal.stop"
+	auditTermDenied   = "remote.terminal.denied"
+	auditClipSet      = "remote.clipboard.set"
+	auditClipGet      = "remote.clipboard.get"
+	auditRdpReset     = "remote.rdp_reset"
+
+	auditUserCreate  = "admin.user.create"
+	auditUserDelete  = "admin.user.delete"
+	auditDeviceAdmin = "admin.device.delete"
+	auditQuery       = "admin.audit.query"
+)
+
+// audit emits one audit record for a WebSocket client. Identity fields are
+// read under h.mu because requireAuth/handleLogin install them there and
+// broadcast goroutines may observe the same client concurrently.
+//
+// Callers MUST NOT hold h.mu when calling this method.
+func (h *wsHub) audit(c *wsClient, warn bool, event string, fields map[string]any) {
+	if fields == nil {
+		fields = make(map[string]any)
+	}
+	if c != nil {
+		h.mu.RLock()
+		connID := c.id
+		addr := c.addr
+		peer := c.peerAddr
+		user := c.user
+		role := c.role
+		h.mu.RUnlock()
+
+		if _, ok := fields["conn"]; !ok && connID != "" {
+			fields["conn"] = connID
+		}
+		if _, ok := fields["ip"]; !ok && addr != "" {
+			fields["ip"] = addr
+		}
+		if _, ok := fields["peer_ip"]; !ok && peer != "" && peer != addr {
+			fields["peer_ip"] = peer
+		}
+		if _, ok := fields["actor"]; !ok && user != "" {
+			fields["actor"] = user
+		}
+		if _, ok := fields["role"]; !ok && role != "" {
+			fields["role"] = role
+		}
+	}
+	if warn {
+		h.log.AuditWarn(event, fields)
+	} else {
+		h.log.Audit(event, fields)
+	}
+}
+
+// auditClose records the end of a browser WebSocket. Anonymous scanners that
+// connect and do nothing produce only the connect event; authenticated
+// sessions, failed-login probes, and command traffic always produce a close
+// record with counters that help spot brute-force / probing behavior.
+func (h *wsHub) auditClose(c *wsClient, screens int) {
+	suspicious := c.statInvalidToken > 0 ||
+		c.statLoginFailures > 0 ||
+		c.statAdminDenied > 0 ||
+		c.statUnknownSalt > 0 ||
+		c.statUnknownCmd > 0
+	if c.user == "" && c.statCommands == 0 && !suspicious {
+		return
+	}
+
+	fields := map[string]any{
+		"duration_ms": time.Since(c.connectedAt).Milliseconds(),
+		"commands":    c.statCommands,
+	}
+	if screens > 0 {
+		fields["screens"] = screens
+	}
+	if c.statInvalidToken > 0 {
+		fields["invalid_tokens"] = c.statInvalidToken
+	}
+	if c.statLoginFailures > 0 {
+		fields["login_failures"] = c.statLoginFailures
+	}
+	if c.statAdminDenied > 0 {
+		fields["admin_denied"] = c.statAdminDenied
+	}
+	if c.statUnknownSalt > 0 {
+		fields["unknown_salt"] = c.statUnknownSalt
+	}
+	if c.statUnknownCmd > 0 {
+		fields["unknown_commands"] = c.statUnknownCmd
+	}
+	h.audit(c, suspicious, auditWSClose, fields)
+}
+
+// requestFields builds the audit context available before a WebSocket client
+// exists (upgrade rejected) or for plain HTTP endpoints (SSO).
+func requestFields(r *http.Request, trustForwardedFor bool) map[string]any {
+	fields := make(map[string]any)
+	if r == nil {
+		return fields
+	}
+	ip := clientIP(r, trustForwardedFor)
+	if ip != "" {
+		fields["ip"] = ip
+	}
+	if peer := stripPort(r.RemoteAddr); peer != "" && peer != ip {
+		fields["peer_ip"] = peer
+	}
+	if origin := r.Header.Get("Origin"); origin != "" {
+		fields["origin"] = origin
+	}
+	if ua := r.UserAgent(); ua != "" {
+		fields["ua"] = ua
+	}
+	return fields
+}
+
+// wsRequestFields returns request metadata worth attaching to login events.
+func (c *wsClient) wsRequestFields() map[string]any {
+	fields := make(map[string]any)
+	if c.origin != "" {
+		fields["origin"] = c.origin
+	}
+	if c.userAgent != "" {
+		fields["ua"] = c.userAgent
+	}
+	return fields
+}
+
+func durationMs(start time.Time) int64 {
+	if start.IsZero() {
+		return 0
+	}
+	return time.Since(start).Milliseconds()
+}
+
+// newConnID returns a short random identifier used to correlate all audit
+// records belonging to one browser WebSocket connection.
+func newConnID() string {
+	var b [4]byte
+	if _, err := rand.Read(b[:]); err != nil {
+		return "conn"
+	}
+	return hex.EncodeToString(b[:])
+}

server/go/web/audit_query.go

@@ -0,0 +1,328 @@
+package web
+
+import (
+	"bufio"
+	"encoding/json"
+	"os"
+	"strings"
+	"time"
+)
+
+// Audit-log query support for the admin-only "Audit Log" page.
+//
+// The server reads its own JSON-lines audit file (logs/audit.log) back to the
+// browser. Records are already redacted at write time (see logger.AuditAt), so
+// returning raw lines is safe as long as we never widen what is written.
+//
+// Only the CURRENT audit file is searched. Rotated files (audit-*.log[.gz])
+// are deliberately out of scope: they need gzip support and a separate index,
+// and the UI is meant for recent-window triage ("what happened just now").
+const (
+	auditQueryDefaultLimit = 100
+	auditQueryMaxLimit     = 500
+	auditQueryMaxOffset    = 10000
+
+	// auditQueryScanBudget bounds how much of the audit file a single query
+	// reads. The tail is read when the file is larger, so the newest records
+	// (what operators actually triage) are always covered and a multi-GB log
+	// cannot stall the WS goroutine.
+	auditQueryScanBudget = 32 << 20 // 32 MB
+)
+
+// auditQueryRequest is the JSON body of the `query_audit` command.
+type auditQueryRequest struct {
+	From     string `json:"from"`  // RFC3339 ("2026-10-18T10:00:00Z"), optional
+	To       string `json:"to"`    // RFC3339, optional
+	Event    string `json:"event"` // exact ("web.login.failure"), prefix ("web." / "web.*"), or ""
+	Actor    string `json:"actor"` // exact, case-insensitive
+	IP       string `json:"ip"`    // exact
+	DeviceID string `json:"device_id"`
+	Keyword  string `json:"keyword"`   // case-insensitive substring of the raw record
+	WarnOnly bool   `json:"warn_only"` // only level=warn records
+	Limit    int    `json:"limit"`
+	Offset   int    `json:"offset"` // skip the newest N matching records
+}
+
+// auditQueryResult is the internal result of scanning the audit file.
+type auditQueryResult struct {
+	Events       []map[string]any
+	Total        int // matching records in the scanned window
+	FileExists   bool
+	FileSize     int64
+	ScannedBytes int64
+	Truncated    bool // the file was larger than auditQueryScanBudget
+}
+
+// handleQueryAudit implements the admin-only audit query command. The reply is
+// `{cmd:"audit_result", ok, events, total, ...}`; events are newest-first.
+func (h *wsHub) handleQueryAudit(c *wsClient, raw []byte) {
+	const replyCmd = "audit_result"
+	if !h.requireAdmin(c, raw, replyCmd) {
+		return
+	}
+	var in auditQueryRequest
+	if err := json.Unmarshal(raw, &in); err != nil {
+		c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": false, "msg": "Invalid request"}))
+		return
+	}
+	in.Limit = clampAuditLimit(in.Limit)
+	in.Offset = clampAuditOffset(in.Offset)
+
+	path := h.log.AuditPath()
+	if path == "" {
+		h.audit(c, true, auditQuery, map[string]any{
+			"ok":     false,
+			"reason": "audit_log_disabled",
+		})
+		c.queue(mustJSON(map[string]any{
+			"cmd": replyCmd, "ok": false,
+			"msg": "Audit log file is disabled on this server (YAMA_AUDIT_LOG=off)",
+		}))
+		return
+	}
+
+	res, err := queryAuditLog(path, in)
+	if err != nil {
+		h.audit(c, true, auditQuery, map[string]any{
+			"ok":     false,
+			"reason": "read_failed",
+			"error":  err.Error(),
+		})
+		c.queue(mustJSON(map[string]any{
+			"cmd": replyCmd, "ok": false,
+			"msg": "Failed to read audit log: " + err.Error(),
+		}))
+		return
+	}
+
+	// Record the query itself: an audit viewer is privileged, and reading the
+	// trail is itself an auditable action. Filter terms are included so an
+	// investigator can see what was searched for.
+	h.audit(c, false, auditQuery, map[string]any{
+		"ok":            true,
+		"event_filter":  in.Event,
+		"actor_filter":  in.Actor,
+		"ip_filter":     in.IP,
+		"device_filter": in.DeviceID,
+		"keyword":       in.Keyword,
+		"warn_only":     in.WarnOnly,
+		"matches":       res.Total,
+		"returned":      len(res.Events),
+		"offset":        in.Offset,
+	})
+
+	c.queue(mustJSON(map[string]any{
+		"cmd":           replyCmd,
+		"ok":            true,
+		"events":        res.Events,
+		"total":         res.Total,
+		"offset":        in.Offset,
+		"limit":         in.Limit,
+		"file":          path,
+		"file_exists":   res.FileExists,
+		"file_size":     res.FileSize,
+		"scanned_bytes": res.ScannedBytes,
+		"truncated":     res.Truncated,
+	}))
+}
+
+func clampAuditLimit(n int) int {
+	if n <= 0 {
+		return auditQueryDefaultLimit
+	}
+	if n > auditQueryMaxLimit {
+		return auditQueryMaxLimit
+	}
+	return n
+}
+
+func clampAuditOffset(n int) int {
+	if n < 0 {
+		return 0
+	}
+	if n > auditQueryMaxOffset {
+		return auditQueryMaxOffset
+	}
+	return n
+}
+
+// queryAuditLog scans path for audit records matching q. The returned events
+// are the newest limit records after skipping offset, in newest-first order.
+func queryAuditLog(path string, q auditQueryRequest) (auditQueryResult, error) {
+	res := auditQueryResult{Events: []map[string]any{}}
+
+	f, err := os.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			// No audit record has been written yet (lumberjack creates the file
+			// lazily). An empty result is correct, not an error.
+			return res, nil
+		}
+		return res, err
+	}
+	defer f.Close()
+
+	info, err := f.Stat()
+	if err != nil {
+		return res, err
+	}
+	res.FileExists = true
+	res.FileSize = info.Size()
+
+	// For very large files, scan only the tail; the newest matches live there.
+	start := int64(0)
+	if info.Size() > auditQueryScanBudget {
+		start = info.Size() - auditQueryScanBudget
+		if _, err := f.Seek(start, 0); err != nil {
+			return res, err
+		}
+		res.Truncated = true
+	}
+
+	from, hasFrom := parseAuditTime(q.From)
+	to, hasTo := parseAuditTime(q.To)
+
+	keep := q.Offset + q.Limit
+	ring := make([]map[string]any, keep)
+	filled := 0
+
+	sc := bufio.NewScanner(f)
+	// Sanitized values are capped at 4096 bytes each; a record with many
+	// fields stays well under 1 MB. Allow headroom rather than aborting the
+	// whole query on one long line.
+	sc.Buffer(make([]byte, 64*1024), 4*1024*1024)
+
+	first := true
+	for sc.Scan() {
+		line := sc.Text()
+		if start > 0 && first {
+			// Seeking into the middle of the file lands mid-line. Drop that
+			// partial record.
+			first = false
+			continue
+		}
+		first = false
+		res.ScannedBytes += int64(len(line)) + 1
+
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		var rec map[string]any
+		if err := json.Unmarshal([]byte(line), &rec); err != nil {
+			continue // tolerate a torn line instead of failing the page
+		}
+		if _, ok := rec["event"].(string); !ok {
+			continue
+		}
+		// Only audit records belong on the page. The dedicated file contains
+		// nothing else, but a hand-edited or mixed file must not surface
+		// ordinary operational lines here.
+		if rec["audit"] != true {
+			continue
+		}
+		if !auditRecordMatches(rec, line, q, from, hasFrom, to, hasTo) {
+			continue
+		}
+		// Ring buffer of the last `keep` matches (file order is chronological).
+		ring[res.Total%keep] = rec
+		if filled < keep {
+			filled++
+		}
+		res.Total++
+	}
+	if err := sc.Err(); err != nil {
+		return res, err
+	}
+
+	// Newest first, skipping Offset. The match with 0-based index i lives at
+	// ring[i%keep] as long as i >= Total-filled.
+	for i := res.Total - 1 - q.Offset; i >= 0 && i >= res.Total-filled; i-- {
+		res.Events = append(res.Events, ring[i%keep])
+		if len(res.Events) >= q.Limit {
+			break
+		}
+	}
+	return res, nil
+}
+
+// auditRecordMatches applies the non-time and time filters to one record.
+// line is the raw JSON line, used for the keyword substring search.
+func auditRecordMatches(rec map[string]any, line string, q auditQueryRequest, from time.Time, hasFrom bool, to time.Time, hasTo bool) bool {
+	if q.Event != "" && !auditEventFilterMatches(q.Event, auditStringField(rec, "event")) {
+		return false
+	}
+	if q.Actor != "" && !strings.EqualFold(auditStringField(rec, "actor"), q.Actor) {
+		return false
+	}
+	if q.IP != "" && auditStringField(rec, "ip") != q.IP {
+		return false
+	}
+	if q.DeviceID != "" && auditStringField(rec, "device_id") != q.DeviceID {
+		return false
+	}
+	if q.WarnOnly && auditStringField(rec, "level") != "warn" {
+		return false
+	}
+	if q.Keyword != "" && !strings.Contains(strings.ToLower(line), strings.ToLower(q.Keyword)) {
+		return false
+	}
+	if hasFrom || hasTo {
+		t, ok := parseAuditTime(auditStringField(rec, "time"))
+		if !ok {
+			return false // cannot prove it is in range
+		}
+		if hasFrom && t.Before(from) {
+			return false
+		}
+		if hasTo && t.After(to) {
+			return false
+		}
+	}
+	return true
+}
+
+// auditEventFilterMatches supports three forms so the UI stays simple:
+//
+//	"web.login.failure" exact
+//	"web.*"             prefix (trailing "*")
+//	"web."              prefix (trailing ".")
+func auditEventFilterMatches(filter, event string) bool {
+	switch {
+	case strings.HasSuffix(filter, "*"):
+		return strings.HasPrefix(event, strings.TrimSuffix(filter, "*"))
+	case strings.HasSuffix(filter, "."):
+		return strings.HasPrefix(event, filter)
+	default:
+		return event == filter
+	}
+}
+
+func auditStringField(rec map[string]any, key string) string {
+	s, _ := rec[key].(string)
+	return s
+}
+
+// parseAuditTime accepts the formats operators and browsers realistically send.
+// Layouts without an explicit zone are parsed as UTC; the frontend always sends
+// Date.toISOString(), so the RFC3339 path is what production uses.
+func parseAuditTime(s string) (time.Time, bool) {
+	s = strings.TrimSpace(s)
+	if s == "" {
+		return time.Time{}, false
+	}
+	layouts := []string{
+		time.RFC3339Nano,
+		time.RFC3339,
+		"2006-01-02T15:04:05",
+		"2006-01-02T15:04",
+		"2006-01-02 15:04:05",
+		"2006-01-02",
+	}
+	for _, layout := range layouts {
+		if t, err := time.Parse(layout, s); err == nil {
+			return t, true
+		}
+	}
+	return time.Time{}, false
+}

server/go/web/audit_query_test.go

@@ -0,0 +1,294 @@
+package web
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/logger"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/wsauth"
+)
+
+// newAuditTestHubWithoutAuditFile builds a hub whose logger has no dedicated
+// audit file, mirroring a server started with YAMA_AUDIT_LOG=off.
+func newAuditTestHubWithoutAuditFile(t *testing.T, dir string) (*wsHub, string) {
+	t.Helper()
+	lg := logger.New(logger.Config{
+		Level:   logger.LevelInfo,
+		Console: false,
+		File:    filepath.Join(dir, "server.log"),
+	})
+	t.Cleanup(func() { _ = lg.Close() })
+	wh := newWSHub(wsauth.New(), hub.New(), nil, lg)
+	t.Cleanup(wh.stop)
+	return wh, ""
+}
+
+func readQueuedJSON(t *testing.T, c *wsClient) map[string]any {
+	t.Helper()
+	select {
+	case m := <-c.send:
+		var v map[string]any
+		if err := json.Unmarshal(m.data, &v); err != nil {
+			t.Fatalf("queued reply is not JSON: %q: %v", m.data, err)
+		}
+		return v
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out waiting for a queued reply")
+		return nil
+	}
+}
+
+// writeAuditFixture writes JSON-lines audit records (oldest first) and returns
+// the file path. Times are UTC RFC3339 so the tests are timezone-independent.
+func writeAuditFixture(t *testing.T, records []map[string]any) string {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "audit.log")
+	var b strings.Builder
+	for _, rec := range records {
+		line, err := json.Marshal(rec)
+		if err != nil {
+			t.Fatalf("marshal fixture: %v", err)
+		}
+		b.Write(line)
+		b.WriteByte('\n')
+	}
+	if err := os.WriteFile(path, []byte(b.String()), 0o644); err != nil {
+		t.Fatalf("write fixture: %v", err)
+	}
+	return path
+}
+
+func auditFixtureRecords() []map[string]any {
+	at := func(hhmm string) string {
+		tm, err := time.Parse("2006-01-02T15:04", "2026-10-18T"+hhmm)
+		if err != nil {
+			panic(err)
+		}
+		return tm.Format(time.RFC3339)
+	}
+	return []map[string]any{
+		{"level": "info", "time": at("10:00"), "audit": true, "event": "web.login.success", "actor": "admin", "ip": "203.0.113.1"},
+		{"level": "warn", "time": at("10:01"), "audit": true, "event": "web.login.failure", "actor": "alice", "ip": "203.0.113.2", "reason": "invalid_credentials"},
+		{"level": "info", "time": at("10:02"), "audit": true, "event": "remote.screen.start", "actor": "admin", "role": "admin", "ip": "203.0.113.1", "device_id": "dev1"},
+		{"level": "info", "time": at("10:03"), "audit": true, "event": "admin.user.delete", "actor": "admin", "ip": "203.0.113.1", "target": "bob"},
+	}
+}
+
+func runAuditQuery(t *testing.T, path string, q auditQueryRequest) auditQueryResult {
+	t.Helper()
+	q.Limit = clampAuditLimit(q.Limit)
+	q.Offset = clampAuditOffset(q.Offset)
+	res, err := queryAuditLog(path, q)
+	if err != nil {
+		t.Fatalf("queryAuditLog: %v", err)
+	}
+	return res
+}
+
+func eventNames(res auditQueryResult) []string {
+	out := make([]string, 0, len(res.Events))
+	for _, e := range res.Events {
+		out = append(out, auditStringField(e, "event"))
+	}
+	return out
+}
+
+func TestAuditQueryNoFilterNewestFirst(t *testing.T) {
+	path := writeAuditFixture(t, auditFixtureRecords())
+	res := runAuditQuery(t, path, auditQueryRequest{Limit: 100})
+	if res.Total != 4 || len(res.Events) != 4 {
+		t.Fatalf("total=%d events=%d, want 4/4", res.Total, len(res.Events))
+	}
+	got := eventNames(res)
+	want := []string{"admin.user.delete", "remote.screen.start", "web.login.failure", "web.login.success"}
+	if strings.Join(got, ",") != strings.Join(want, ",") {
+		t.Fatalf("events = %v, want %v", got, want)
+	}
+}
+
+func TestAuditQueryEventFilters(t *testing.T) {
+	path := writeAuditFixture(t, auditFixtureRecords())
+	cases := []struct {
+		filter string
+		want   []string
+	}{
+		{"web.", []string{"web.login.failure", "web.login.success"}},
+		{"web.*", []string{"web.login.failure", "web.login.success"}},
+		{"web.login.failure", []string{"web.login.failure"}},
+		{"remote.*", []string{"remote.screen.start"}},
+	}
+	for _, tc := range cases {
+		res := runAuditQuery(t, path, auditQueryRequest{Event: tc.filter, Limit: 100})
+		got := eventNames(res)
+		if strings.Join(got, ",") != strings.Join(tc.want, ",") {
+			t.Errorf("filter %q → %v, want %v", tc.filter, got, tc.want)
+		}
+	}
+}
+
+func TestAuditQueryFieldFilters(t *testing.T) {
+	path := writeAuditFixture(t, auditFixtureRecords())
+	from, _ := time.Parse(time.RFC3339, "2026-10-18T10:01:00Z")
+	to, _ := time.Parse(time.RFC3339, "2026-10-18T10:02:00Z")
+
+	cases := []struct {
+		name string
+		q    auditQueryRequest
+		want []string
+	}{
+		{"actor case-insensitive", auditQueryRequest{Actor: "ALICE", Limit: 100}, []string{"web.login.failure"}},
+		{"ip", auditQueryRequest{IP: "203.0.113.2", Limit: 100}, []string{"web.login.failure"}},
+		{"device", auditQueryRequest{DeviceID: "dev1", Limit: 100}, []string{"remote.screen.start"}},
+		{"warn only", auditQueryRequest{WarnOnly: true, Limit: 100}, []string{"web.login.failure"}},
+		{"keyword target", auditQueryRequest{Keyword: "BOB", Limit: 100}, []string{"admin.user.delete"}},
+		{"time range", auditQueryRequest{
+			From: from.Format(time.RFC3339), To: to.Format(time.RFC3339), Limit: 100,
+		}, []string{"remote.screen.start", "web.login.failure"}},
+	}
+	for _, tc := range cases {
+		res := runAuditQuery(t, path, tc.q)
+		got := eventNames(res)
+		if strings.Join(got, ",") != strings.Join(tc.want, ",") {
+			t.Errorf("%s → %v, want %v", tc.name, got, tc.want)
+		}
+	}
+}
+
+func TestAuditQueryOffsetAndLimit(t *testing.T) {
+	path := writeAuditFixture(t, auditFixtureRecords())
+	res := runAuditQuery(t, path, auditQueryRequest{Limit: 2, Offset: 1})
+	if res.Total != 4 {
+		t.Fatalf("total = %d, want 4", res.Total)
+	}
+	got := eventNames(res)
+	want := []string{"remote.screen.start", "web.login.failure"}
+	if strings.Join(got, ",") != strings.Join(want, ",") {
+		t.Fatalf("events = %v, want %v", got, want)
+	}
+
+	// Offsetting past the end yields no events but keeps the total.
+	res = runAuditQuery(t, path, auditQueryRequest{Limit: 2, Offset: 4})
+	if res.Total != 4 || len(res.Events) != 0 {
+		t.Fatalf("offset past end: total=%d events=%v", res.Total, eventNames(res))
+	}
+}
+
+func TestAuditQuerySkipsNonAuditAndTornLines(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "audit.log")
+	content := `{"event":"device.online","actor":"x"}
+not json at all
+{"level":"info","time":"2026-10-18T10:00:00Z","audit":true,"event":"web.login.success","actor":"admin"}`
+	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	res := runAuditQuery(t, path, auditQueryRequest{Limit: 100})
+	if res.Total != 1 || len(res.Events) != 1 {
+		t.Fatalf("total=%d events=%v, want the single valid record", res.Total, eventNames(res))
+	}
+}
+
+func TestAuditQueryMissingFile(t *testing.T) {
+	res := runAuditQuery(t, filepath.Join(t.TempDir(), "does-not-exist.log"), auditQueryRequest{Limit: 10})
+	if res.FileExists {
+		t.Error("FileExists = true for a missing file")
+	}
+	if res.Total != 0 || len(res.Events) != 0 {
+		t.Errorf("total=%d events=%v, want empty", res.Total, eventNames(res))
+	}
+	if res.Events == nil {
+		t.Error("Events is nil; JSON would encode null instead of []")
+	}
+}
+
+func TestAuditQueryClampsPaging(t *testing.T) {
+	if got := clampAuditLimit(0); got != auditQueryDefaultLimit {
+		t.Errorf("limit(0) = %d, want default %d", got, auditQueryDefaultLimit)
+	}
+	if got := clampAuditLimit(-3); got != auditQueryDefaultLimit {
+		t.Errorf("limit(-3) = %d, want default %d", got, auditQueryDefaultLimit)
+	}
+	if got := clampAuditLimit(9999); got != auditQueryMaxLimit {
+		t.Errorf("limit(9999) = %d, want max %d", got, auditQueryMaxLimit)
+	}
+	if got := clampAuditLimit(50); got != 50 {
+		t.Errorf("limit(50) = %d, want 50", got)
+	}
+	if got := clampAuditOffset(-5); got != 0 {
+		t.Errorf("offset(-5) = %d, want 0", got)
+	}
+	if got := clampAuditOffset(1 << 30); got != auditQueryMaxOffset {
+		t.Errorf("offset(huge) = %d, want max %d", got, auditQueryMaxOffset)
+	}
+}
+
+func TestQueryAuditHandlerAdminOnly(t *testing.T) {
+	wh, _, _ := auditTestHub(t)
+	viewer, tok := auditTestClient(wh, "viewer")
+	raw, _ := json.Marshal(map[string]any{"token": tok})
+	wh.handleQueryAudit(viewer, raw)
+
+	msg := readQueuedJSON(t, viewer)
+	if msg["cmd"] != "audit_result" || msg["ok"] != false {
+		t.Fatalf("viewer reply = %+v", msg)
+	}
+	if _, ok := msg["events"]; ok {
+		t.Error("denied viewer got events")
+	}
+}
+
+func TestQueryAuditHandlerReturnsEvents(t *testing.T) {
+	wh, _, _ := auditTestHub(t)
+	// Two records written directly through the same logger the hub queries.
+	wh.log.Audit("web.login.success", map[string]any{"actor": "admin", "ip": "203.0.113.1"})
+	wh.log.Audit("remote.screen.start", map[string]any{"actor": "admin", "device_id": "dev1"})
+
+	admin, tok := auditTestClient(wh, "admin")
+	raw, _ := json.Marshal(map[string]any{"token": tok, "limit": 10})
+	wh.handleQueryAudit(admin, raw)
+
+	msg := readQueuedJSON(t, admin)
+	if msg["cmd"] != "audit_result" || msg["ok"] != true {
+		t.Fatalf("reply = %+v", msg)
+	}
+	events, ok := msg["events"].([]any)
+	if !ok || len(events) < 2 {
+		t.Fatalf("events = %#v, want at least the two written records", msg["events"])
+	}
+	// requireAuth writes a web.session.resume record for this same request, so
+	// that one legitimately appears newer. Assert the two written records are
+	// present and still newest-first relative to each other.
+	var names []string
+	for _, e := range events {
+		if m, ok := e.(map[string]any); ok {
+			names = append(names, auditStringField(m, "event"))
+		}
+	}
+	joined := strings.Join(names, ",")
+	if !strings.Contains(joined, "remote.screen.start") || !strings.Contains(joined, "web.login.success") {
+		t.Fatalf("events = %v, want both written records", names)
+	}
+	if strings.Index(joined, "remote.screen.start") > strings.Index(joined, "web.login.success") {
+		t.Fatalf("events = %v, want newest-first order", names)
+	}
+	if msg["truncated"] != false || msg["file_exists"] != true {
+		t.Errorf("meta = %+v", msg)
+	}
+}
+
+func TestQueryAuditHandlerDisabledFile(t *testing.T) {
+	dir := t.TempDir()
+	wh, _ := newAuditTestHubWithoutAuditFile(t, dir)
+	admin, tok := auditTestClient(wh, "admin")
+	raw, _ := json.Marshal(map[string]any{"token": tok})
+	wh.handleQueryAudit(admin, raw)
+
+	msg := readQueuedJSON(t, admin)
+	if msg["ok"] != false {
+		t.Fatalf("reply = %+v, want ok:false when the audit file is disabled", msg)
+	}
+}

server/go/web/audit_test.go

@@ -0,0 +1,195 @@
+package web
+
+import (
+	"bufio"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/connection"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/logger"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/wsauth"
+)
+
+// auditTestHub builds a wsHub whose logger writes both the main log and the
+// dedicated audit log to a temp directory.
+func auditTestHub(t *testing.T) (wh *wsHub, devices *hub.Hub, auditPath string) {
+	t.Helper()
+	dir := t.TempDir()
+	auditPath = filepath.Join(dir, "audit.log")
+	lg := logger.New(logger.Config{
+		Level:     logger.LevelInfo,
+		Console:   false,
+		File:      filepath.Join(dir, "server.log"),
+		AuditFile: auditPath,
+	})
+	t.Cleanup(func() { _ = lg.Close() })
+
+	devices = hub.New()
+	wh = newWSHub(wsauth.New(), devices, nil, lg)
+	t.Cleanup(wh.stop)
+	return wh, devices, auditPath
+}
+
+func auditTestClient(wh *wsHub, role string) (*wsClient, string) {
+	tok, err := wh.auth.IssueToken("tester", role)
+	if err != nil {
+		panic(err)
+	}
+	c := &wsClient{
+		send:           make(chan wsMsg, 64),
+		closed:         make(chan struct{}),
+		id:             newConnID(),
+		addr:           "203.0.113.5",
+		peerAddr:       "203.0.113.5",
+		connectedAt:    time.Now(),
+		watchIDs:       make(map[string]struct{}),
+		watchStartedAt: make(map[string]time.Time),
+		keyframeAt:     make(map[string]int64),
+	}
+	wh.register(c)
+	return c, tok
+}
+
+func readAuditEvents(t *testing.T, path string) []map[string]any {
+	t.Helper()
+	f, err := os.Open(path)
+	if err != nil {
+		t.Fatalf("open audit log: %v", err)
+	}
+	defer f.Close()
+
+	var out []map[string]any
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		line := strings.TrimSpace(sc.Text())
+		if line == "" {
+			continue
+		}
+		var m map[string]any
+		if err := json.Unmarshal([]byte(line), &m); err != nil {
+			t.Fatalf("bad audit line %q: %v", line, err)
+		}
+		out = append(out, m)
+	}
+	if err := sc.Err(); err != nil {
+		t.Fatalf("scan audit log: %v", err)
+	}
+	return out
+}
+
+func findAuditEvent(t *testing.T, path, event string) map[string]any {
+	t.Helper()
+	for _, m := range readAuditEvents(t, path) {
+		if m["event"] == event {
+			return m
+		}
+	}
+	t.Fatalf("audit event %q not found in %v", event, readAuditEvents(t, path))
+	return nil
+}
+
+func TestLoginFailureIsAudited(t *testing.T) {
+	wh, _, auditPath := auditTestHub(t)
+	wh.auth.AddAdminFromPlainPassword("admin", "hunter2")
+	c, _ := auditTestClient(wh, "viewer")
+
+	nonce, err := wsauth.NewNonce()
+	if err != nil {
+		t.Fatalf("NewNonce: %v", err)
+	}
+	c.nonce = nonce
+	raw, _ := json.Marshal(map[string]any{
+		"username": "admin",
+		"response": "not-the-right-response",
+		"nonce":    nonce,
+	})
+	wh.handleLogin(c, raw)
+
+	rec := findAuditEvent(t, auditPath, auditLoginFail)
+	if rec["reason"] != "invalid_credentials" {
+		t.Errorf("reason = %v", rec["reason"])
+	}
+	if rec["username"] != "admin" {
+		t.Errorf("username = %v", rec["username"])
+	}
+	if rec["user_exists"] != true {
+		t.Errorf("user_exists = %v, want true", rec["user_exists"])
+	}
+	if rec["ip"] != "203.0.113.5" {
+		t.Errorf("ip = %v", rec["ip"])
+	}
+	if _, ok := rec["response"]; ok {
+		t.Error("audit record leaked the login response")
+	}
+}
+
+func TestAdminDenialIsAudited(t *testing.T) {
+	wh, _, auditPath := auditTestHub(t)
+	c, tok := auditTestClient(wh, "viewer")
+	raw, _ := json.Marshal(map[string]any{"token": tok})
+
+	if wh.requireAdmin(c, raw, "delete_device_result") {
+		t.Fatal("viewer passed requireAdmin")
+	}
+	rec := findAuditEvent(t, auditPath, auditDenied)
+	if rec["operation"] != "delete_device" {
+		t.Errorf("operation = %v", rec["operation"])
+	}
+	if rec["role"] != "viewer" || rec["actor"] != "tester" {
+		t.Errorf("identity fields = %+v", rec)
+	}
+}
+
+func TestScreenStartAndOfflineStopAreAudited(t *testing.T) {
+	wh, devices, auditPath := auditTestHub(t)
+	devices.SetSender(func(*connection.Context, []byte) error { return nil })
+	hctx := &connection.Context{RemoteAddr: "10.0.0.9:1234"}
+	devices.Register(&hub.Device{ID: "dev1", Name: "Dev"}, hctx)
+
+	c, tok := auditTestClient(wh, "admin")
+	raw, _ := json.Marshal(map[string]any{
+		"token": tok, "id": "dev1", "multiWatch": true, "req": "1",
+	})
+	wh.handleConnect(c, raw)
+
+	start := findAuditEvent(t, auditPath, auditScreenStart)
+	if start["device_id"] != "dev1" || start["mode"] != "started" {
+		t.Errorf("screen start = %+v", start)
+	}
+
+	wh.OnDeviceOffline("dev1")
+
+	stop := findAuditEvent(t, auditPath, auditScreenStop)
+	if stop["device_id"] != "dev1" || stop["reason"] != "device_offline" {
+		t.Errorf("screen stop = %+v", stop)
+	}
+	if _, ok := stop["duration_ms"]; !ok {
+		t.Error("screen stop has no duration_ms")
+	}
+}
+
+func TestUnknownCommandRecordedOnce(t *testing.T) {
+	wh, _, auditPath := auditTestHub(t)
+	c, _ := auditTestClient(wh, "viewer")
+
+	for i := 0; i < 5; i++ {
+		wh.dispatch(c, "definitely_not_a_command", []byte(`{}`))
+	}
+	count := 0
+	for _, m := range readAuditEvents(t, auditPath) {
+		if m["event"] == auditUnknownCmd {
+			count++
+		}
+	}
+	if count != 1 {
+		t.Fatalf("unknown-command audit records = %d, want 1", count)
+	}
+	if c.statUnknownCmd != 5 {
+		t.Fatalf("statUnknownCmd = %d, want 5", c.statUnknownCmd)
+	}
+}

server/go/web/delete_device_test.go

@@ -0,0 +1,131 @@
+package web
+
+import (
+	"encoding/json"
+	"path/filepath"
+	"testing"
+
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/connection"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/devicehistory"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/logger"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/protocol"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/wsauth"
+)
+
+// deleteTestHub builds the minimal wsHub wiring handleDeleteDevice needs.
+func deleteTestHub(t *testing.T) (*wsHub, *hub.Hub, *devicehistory.Store) {
+	t.Helper()
+	h := hub.New()
+	hist, err := devicehistory.Open(filepath.Join(t.TempDir(), "devices.json"), 100, nil)
+	if err != nil {
+		t.Fatalf("Open history: %v", err)
+	}
+	t.Cleanup(func() { _ = hist.Close() })
+	h.Subscribe(hist)
+
+	auth := wsauth.New()
+	wh := &wsHub{
+		auth:    auth,
+		devices: h,
+		history: hist,
+		log:     logger.New(logger.Config{}),
+		clients: make(map[*wsClient]struct{}),
+	}
+	return wh, h, hist
+}
+
+func deleteTestClient(wh *wsHub, role string) (*wsClient, string) {
+	tok, err := wh.auth.IssueToken("tester", role)
+	if err != nil {
+		panic(err)
+	}
+	c := &wsClient{send: make(chan wsMsg, 8), closed: make(chan struct{})}
+	wh.register(c)
+	return c, tok
+}
+
+func deleteReply(t *testing.T, c *wsClient) map[string]any {
+	t.Helper()
+	for {
+		select {
+		case m := <-c.send:
+			var out map[string]any
+			if err := json.Unmarshal(m.data, &out); err != nil {
+				t.Fatalf("decode reply: %v", err)
+			}
+			if out["cmd"] == "delete_device_result" {
+				return out
+			}
+		default:
+			t.Fatal("no delete_device_result reply")
+			return nil
+		}
+	}
+}
+
+func TestDeleteDeviceOfflineRemovesHistoryRecord(t *testing.T) {
+	wh, h, hist := deleteTestHub(t)
+	h.Register(&hub.Device{ID: "gone", Name: "Gone"},
+		&connection.Context{RemoteAddr: "10.0.0.1:1000"})
+	h.Unregister("gone")
+
+	c, tok := deleteTestClient(wh, "admin")
+	raw, _ := json.Marshal(map[string]any{"token": tok, "id": "gone"})
+	wh.handleDeleteDevice(c, raw)
+
+	rep := deleteReply(t, c)
+	if rep["ok"] != true || rep["mode"] != "removed" {
+		t.Fatalf("reply = %+v, want ok/removed", rep)
+	}
+	if hist.Remove("gone") {
+		t.Fatal("history record still present after delete")
+	}
+}
+
+func TestDeleteDeviceOnlineSendsUninstall(t *testing.T) {
+	wh, h, hist := deleteTestHub(t)
+	var sent []byte
+	h.SetSender(func(_ *connection.Context, data []byte) error {
+		sent = append([]byte(nil), data...)
+		return nil
+	})
+	h.Register(&hub.Device{ID: "live", Name: "Live"},
+		&connection.Context{RemoteAddr: "10.0.0.2:1000"})
+
+	c, tok := deleteTestClient(wh, "admin")
+	raw, _ := json.Marshal(map[string]any{"token": tok, "id": "live"})
+	wh.handleDeleteDevice(c, raw)
+
+	rep := deleteReply(t, c)
+	if rep["ok"] != true || rep["mode"] != "uninstall" {
+		t.Fatalf("reply = %+v, want ok/uninstall", rep)
+	}
+	if len(sent) != 1 || sent[0] != protocol.CommandUninstall {
+		t.Fatalf("sent = %v, want single %d byte", sent, protocol.CommandUninstall)
+	}
+	// The history record is dropped along with the uninstall, so the device
+	// does not reappear as a dead offline entry after it disconnects.
+	if hist.Remove("live") {
+		t.Fatal("online device's history record survived the uninstall")
+	}
+}
+
+func TestDeleteDeviceRequiresAdmin(t *testing.T) {
+	wh, h, hist := deleteTestHub(t)
+	h.Register(&hub.Device{ID: "gone", Name: "Gone"},
+		&connection.Context{RemoteAddr: "10.0.0.3:1000"})
+	h.Unregister("gone")
+
+	c, tok := deleteTestClient(wh, "viewer")
+	raw, _ := json.Marshal(map[string]any{"token": tok, "id": "gone"})
+	wh.handleDeleteDevice(c, raw)
+
+	rep := deleteReply(t, c)
+	if rep["ok"] != false {
+		t.Fatalf("reply = %+v, want ok:false", rep)
+	}
+	if !hist.Remove("gone") {
+		t.Fatal("viewer delete removed the history record")
+	}
+}

server/go/web/device_list_test.go

@@ -0,0 +1,53 @@
+package web
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/connection"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/devicehistory"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
+)
+
+func TestListDevicesWithOffline(t *testing.T) {
+	h := hub.New()
+	hist, err := devicehistory.Open(filepath.Join(t.TempDir(), "devices.json"), 100, nil)
+	if err != nil {
+		t.Fatalf("Open history: %v", err)
+	}
+	t.Cleanup(func() { _ = hist.Close() })
+	h.Subscribe(hist)
+
+	h.Register(&hub.Device{ID: "online", Name: "Online"},
+		&connection.Context{RemoteAddr: "10.0.0.1:1000"})
+	h.Register(&hub.Device{ID: "gone", Name: "Gone"},
+		&connection.Context{RemoteAddr: "10.0.0.2:1000"})
+	h.Unregister("gone")
+
+	wh := &wsHub{devices: h, history: hist}
+	got := wh.listDevicesWithOffline()
+	if len(got) != 2 {
+		t.Fatalf("devices = %d, want 2 (1 online + 1 offline)", len(got))
+	}
+	if got[0].ID != "online" || !got[0].Online {
+		t.Fatalf("first = %+v, want online device", got[0])
+	}
+	if got[1].ID != "gone" || got[1].Online {
+		t.Fatalf("second = %+v, want offline device", got[1])
+	}
+	if got[1].LastSeen == 0 {
+		t.Fatal("offline device missing last_seen")
+	}
+}
+
+func TestListDevicesWithoutHistoryIsOnlineOnly(t *testing.T) {
+	h := hub.New()
+	h.Register(&hub.Device{ID: "online", Name: "Online"},
+		&connection.Context{RemoteAddr: "10.0.0.1:1000"})
+
+	wh := &wsHub{devices: h}
+	got := wh.listDevicesWithOffline()
+	if len(got) != 1 || got[0].ID != "online" {
+		t.Fatalf("devices = %+v, want just the online device", got)
+	}
+}

server/go/web/server.go

@@ -16,6 +16,7 @@ import (
 	"unicode"
 	"unicode/utf8"
 
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/devicehistory"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/logger"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/wsauth"
@@ -30,6 +31,7 @@ type Server struct {
 	srv               *http.Server
 	hub               *hub.Hub
 	auth              *wsauth.Authenticator
+	history           *devicehistory.Store // nil → no offline devices
 	ws                *wsHub
 	allowedOrigins    []string // for WS Origin allowlist; empty = same-origin only
 	loginIPLimit      *wsauth.RateLimiter
@@ -86,6 +88,14 @@ func New(port int, log *logger.Logger, h *hub.Hub, auth *wsauth.Authenticator) *
 	return &Server{port: port, log: log, hub: h, auth: auth}
 }
 
+// WithDeviceHistory attaches the persistent device-history store. When set,
+// device_list also returns devices that have logged in before but are offline
+// now. Passing nil keeps the online-only behaviour. Safe to call before Start.
+func (s *Server) WithDeviceHistory(h *devicehistory.Store) *Server {
+	s.history = h
+	return s
+}
+
 // WithConfig applies hardening configuration. Returns the receiver for
 // chainable setup. Safe to call before Start; ignored thereafter.
 func (s *Server) WithConfig(cfg Config) *Server {
@@ -107,7 +117,7 @@ func (s *Server) Start() error {
 		return nil
 	}
 
-	s.ws = newWSHub(s.auth, s.hub, s.log).
+	s.ws = newWSHub(s.auth, s.hub, s.history, s.log).
 		withOriginAllowlist(s.allowedOrigins).
 		withLoginRateLimiters(s.loginIPLimit, s.loginUserLimit).
 		withTrustForwardedFor(s.trustForwardedFor)

server/go/web/sso.go

@@ -33,26 +33,47 @@ func (s *Server) handleSSO(w http.ResponseWriter, r *http.Request) {
 	}
 	username, role, ok := s.sso.Detect(r)
 	if !ok {
+		// No usable portal credential: the normal fallback to the login form.
+		// Not audited — portal users without YAMA access hit this routinely.
 		s.unauthorized(w)
 		return
 	}
 	// Only the "admin" role may skip the login form via SSO. Every other role
 	// (viewer, unknown) must authenticate against YAMA's own login, even with
-	// a valid portal session.
+	// a valid portal session. A valid portal identity being refused here is
+	// worth an audit record: it is an authorization decision, not a login-form
+	// fallback.
 	if role != "admin" {
+		fields := requestFields(r, s.trustForwardedFor)
+		fields["method"] = "sso"
+		fields["actor"] = username
+		fields["role"] = role
+		fields["reason"] = "role_not_allowed"
+		s.log.AuditWarn(auditLoginFail, fields)
 		s.unauthorized(w)
 		return
 	}
 
 	token, err := s.auth.IssueToken(username, role)
 	if err != nil {
+		fields := requestFields(r, s.trustForwardedFor)
+		fields["method"] = "sso"
+		fields["actor"] = username
+		fields["role"] = role
+		fields["reason"] = "token_issue_failed"
+		fields["error"] = err.Error()
+		s.log.AuditWarn(auditLoginFail, fields)
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusInternalServerError)
 		_, _ = w.Write([]byte(`{"error":"internal error"}`))
 		return
 	}
 
-	s.log.Info("sso: user=%s role=%s", username, role)
+	fields := requestFields(r, s.trustForwardedFor)
+	fields["method"] = "sso"
+	fields["actor"] = username
+	fields["role"] = role
+	s.log.Audit(auditLoginOK, fields)
 	w.Header().Set("Content-Type", "application/json; charset=utf-8")
 	w.Header().Set("Cache-Control", "no-store")
 	_ = json.NewEncoder(w).Encode(map[string]string{

server/go/web/ws.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/gorilla/websocket"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/devicehistory"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/logger"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/wsauth"
@@ -47,11 +48,19 @@ type wsClient struct {
 	closed chan struct{}
 	once   sync.Once
 
+	// Immutable connection metadata (set once in serve).
+	id          string // short random id for audit correlation
+	addr        string // resolved client IP for logs / rate limits
+	peerAddr    string // actual TCP peer (differs from addr behind a proxy)
+	origin      string
+	userAgent   string
+	connectedAt time.Time
+
 	// Mutated under wsHub.mu (or only by the read loop owning this client).
 	nonce        string // outstanding challenge — cleared after a successful login
 	token        string // set once authenticated
 	role         string // mirrors session role after login
-	addr         string // client address for logs
+	user         string // mirrors session username after login/resume
 	termWatching string // device ID for an open web terminal session, "" otherwise
 
 	// watchIDs is the set of devices this browser is streaming (the screen
@@ -59,9 +68,30 @@ type wsClient struct {
 	// Guarded by wsHub.mu.
 	watchIDs map[string]struct{}
 
+	// watchStartedAt records when each watch began so stop events can carry a
+	// duration. Guarded by wsHub.mu.
+	watchStartedAt map[string]time.Time
+
 	// keyframeAt throttles keyframe requests to one per device per second.
 	// Unix seconds, guarded by wsHub.mu.
 	keyframeAt map[string]int64
+
+	// Terminal session bookkeeping. Guarded by wsHub.mu.
+	termStartedAt   time.Time
+	termCloseReason string
+
+	// Audit counters, owned by the read-loop goroutine and read in unregister
+	// after that goroutine returns.
+	statCommands      int
+	statInvalidToken  int
+	statLoginFailures int
+	statAdminDenied   int
+	statUnknownSalt   int
+	statUnknownCmd    int
+
+	auditInvalidTokenLogged bool
+	auditUnknownSaltLogged  bool
+	auditUnknownCmdLogged   bool
 }
 
 // queue writes a JSON text frame onto the send buffer. Drops silently if the
@@ -96,7 +126,7 @@ func (c *wsClient) close() {
 // challengeCaps advertises optional protocol features. It is appended to every
 // challenge, including the rotation after a failed login, because the browser
 // overwrites its capability state on each challenge. Old frontends ignore it.
-const challengeCaps = `,"caps":{"multiWatch":true,"keyframeRequest":true}`
+const challengeCaps = `,"caps":{"multiWatch":true,"keyframeRequest":true,"offlineDevices":true,"auditLog":true}`
 
 // maxWatchPerClient bounds the number of devices one WebSocket may stream at
 // once. The wall tops out at 25 tiles; the slack covers a focus switch racing
@@ -116,6 +146,7 @@ func (c *wsClient) isWatching(deviceID string) bool {
 type wsHub struct {
 	auth    *wsauth.Authenticator
 	devices *hub.Hub
+	history *devicehistory.Store // nil → device_list stays online-only
 	log     *logger.Logger
 
 	mu      sync.RWMutex
@@ -138,10 +169,11 @@ type wsHub struct {
 	trustForwardedFor bool // honor X-Forwarded-For (only when behind a trusted proxy)
 }
 
-func newWSHub(auth *wsauth.Authenticator, devices *hub.Hub, log *logger.Logger) *wsHub {
+func newWSHub(auth *wsauth.Authenticator, devices *hub.Hub, history *devicehistory.Store, log *logger.Logger) *wsHub {
 	h := &wsHub{
 		auth:              auth,
 		devices:           devices,
+		history:           history,
 		log:               log,
 		clients:           make(map[*wsClient]struct{}),
 		screenCloseTimers: make(map[string]*time.Timer),
@@ -283,8 +315,12 @@ func (h *wsHub) OnDeviceOffline(id string) {
 	// connection no longer holds a subscription for it. The browser does the
 	// same with its local refcount. Without this, a stale entry would keep
 	// countWatchers non-zero and later block the screen teardown.
+	type viewer struct {
+		c     *wsClient
+		start time.Time
+	}
+	var stopped []viewer
 	h.mu.Lock()
-	defer h.mu.Unlock()
 	for c := range h.clients {
 		if !c.isWatching(id) {
 			continue
@@ -294,6 +330,19 @@ func (h *wsHub) OnDeviceOffline(id string) {
 		if c.token != "" {
 			c.queue(msg)
 		}
+		if !c.watchStartedAt[id].IsZero() {
+			stopped = append(stopped, viewer{c, c.watchStartedAt[id]})
+		}
+		delete(c.watchStartedAt, id)
+	}
+	h.mu.Unlock()
+	// Audit outside h.mu: h.audit takes h.mu.RLock.
+	for _, v := range stopped {
+		h.audit(v.c, false, auditScreenStop, map[string]any{
+			"device_id":   id,
+			"duration_ms": durationMs(v.start),
+			"reason":      "device_offline",
+		})
 	}
 }
 
@@ -412,14 +461,35 @@ func (h *wsHub) OnTerminalClosed(deviceID string, reason string) {
 		"ok":     true,
 		"reason": reason,
 	})
+	type closed struct {
+		c     *wsClient
+		start time.Time
+		why   string
+	}
+	var done []closed
 	h.mu.Lock()
-	defer h.mu.Unlock()
 	for c := range h.clients {
 		if c.termWatching == deviceID && c.token != "" {
+			why := c.termCloseReason
+			if why == "" {
+				why = reason
+			}
+			done = append(done, closed{c, c.termStartedAt, why})
 			c.termWatching = ""
+			c.termStartedAt = time.Time{}
+			c.termCloseReason = ""
 			c.queue(msg)
 		}
 	}
+	h.mu.Unlock()
+	// Audit outside h.mu: h.audit takes h.mu.RLock.
+	for _, d := range done {
+		h.audit(d.c, false, auditTermStop, map[string]any{
+			"device_id":   deviceID,
+			"duration_ms": durationMs(d.start),
+			"reason":      d.why,
+		})
+	}
 }
 
 // OnDeviceUpdate forwards heartbeat-derived liveness data so the device-list
@@ -464,26 +534,49 @@ func (h *wsHub) unregister(c *wsClient) {
 	// below must run OUTSIDE the lock: countWatchers takes h.mu.RLock and
 	// deferredCloseScreen takes h.mu.Lock.
 	watched := make([]string, 0, len(c.watchIDs))
+	started := make(map[string]time.Time, len(c.watchIDs))
 	for id := range c.watchIDs {
 		watched = append(watched, id)
+		started[id] = c.watchStartedAt[id]
 	}
 	c.watchIDs = nil
+	c.watchStartedAt = nil
 	c.keyframeAt = nil
+
+	termDevice := c.termWatching
+	termStart := c.termStartedAt
+	c.termWatching = ""
+	c.termStartedAt = time.Time{}
+	c.termCloseReason = ""
 	h.mu.Unlock()
+
 	// If this client was the last viewer of a device, tear down the screen
 	// session so the device stops encoding.
 	for _, id := range watched {
+		if !started[id].IsZero() {
+			h.audit(c, false, auditScreenStop, map[string]any{
+				"device_id":   id,
+				"duration_ms": durationMs(started[id]),
+				"reason":      "ws_close",
+			})
+		}
 		if h.countWatchers(id) == 0 {
 			h.deferredCloseScreen(id)
 		}
 	}
 	// Terminal sessions are single-viewer by design, so any open session
 	// belongs to this client. Tear it down so the next viewer doesn't
-	// hit ErrTerminalBusy from an abandoned session.
+	// hit ErrTerminalBusy from an abandoned session. The client is already
-	if c.termWatching != "" {
+	// out of h.clients, so OnTerminalClosed won't reach it — audit here.
-		h.devices.CloseTerminalSession(c.termWatching)
+	if termDevice != "" {
-		c.termWatching = ""
+		h.devices.CloseTerminalSession(termDevice)
+		h.audit(c, false, auditTermStop, map[string]any{
+			"device_id":   termDevice,
+			"duration_ms": durationMs(termStart),
+			"reason":      "ws_close",
+		})
 	}
+	h.auditClose(c, len(watched))
 	// Do NOT revoke the token: tokens are session-scoped, not WS-scoped.
 	// Frontend may close+reopen the WS at any time (visibilitychange handler,
 	// brief network blip, reload) and must be able to resume with the same
@@ -518,6 +611,16 @@ func (h *wsHub) deferredCloseScreen(deviceID string) {
 // ----- HTTP handler -------------------------------------------------------
 
 func (h *wsHub) serve(w http.ResponseWriter, r *http.Request) {
+	// Reject disallowed origins explicitly so the rejection is auditable.
+	// Upgrader.CheckOrigin below is kept as defense in depth.
+	if !h.checkOrigin(r) {
+		fields := requestFields(r, h.trustForwardedFor)
+		fields["reason"] = "origin_not_allowed"
+		h.log.AuditWarn(auditWSReject, fields)
+		http.Error(w, "origin not allowed", http.StatusForbidden)
+		return
+	}
+
 	// Build a per-call upgrader so CheckOrigin closes over this hub's
 	// allowlist instead of a package-level mutable.
 	upgrader := baseUpgrader
@@ -525,7 +628,10 @@ func (h *wsHub) serve(w http.ResponseWriter, r *http.Request) {
 
 	conn, err := upgrader.Upgrade(w, r, nil)
 	if err != nil {
-		h.log.Error("ws upgrade: %v", err)
+		fields := requestFields(r, h.trustForwardedFor)
+		fields["reason"] = "upgrade_failed"
+		fields["error"] = err.Error()
+		h.log.AuditWarn(auditWSReject, fields)
 		return
 	}
 	conn.SetReadLimit(wsReadLimit)
@@ -541,12 +647,19 @@ func (h *wsHub) serve(w http.ResponseWriter, r *http.Request) {
 		conn:           conn,
 		send:           make(chan wsMsg, wsSendBuffer),
 		closed:         make(chan struct{}),
-		nonce:      nonce,
+		id:             newConnID(),
 		addr:           clientIP(r, h.trustForwardedFor),
+		peerAddr:       stripPort(r.RemoteAddr),
+		origin:         r.Header.Get("Origin"),
+		userAgent:      r.UserAgent(),
+		connectedAt:    time.Now(),
+		nonce:          nonce,
 		watchIDs:       make(map[string]struct{}),
+		watchStartedAt: make(map[string]time.Time),
 		keyframeAt:     make(map[string]int64),
 	}
 	h.register(client)
+	h.audit(client, false, auditWSConnect, client.wsRequestFields())
 	defer h.unregister(client)
 
 	go h.writeLoop(client)

server/go/web/ws_handlers.go

@@ -2,7 +2,9 @@ package web
 
 import (
 	"encoding/json"
+	"errors"
 	"sort"
+	"strings"
 	"time"
 
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
@@ -37,6 +39,9 @@ func (h *wsHub) rotateChallenge(c *wsClient) {
 // Phase 6 adds: term_open / term_input / term_resize / term_close (PTY relay).
 // Phase 7 covers admin: create_user / delete_user / list_users / get_groups.
 func (h *wsHub) dispatch(c *wsClient, cmd string, raw []byte) {
+	// Connection-scoped counters feed the web.ws.close audit summary, which
+	// is what turns a silent port scan into a visible event.
+	c.statCommands++
 	switch cmd {
 	case "get_salt":
 		h.handleGetSalt(c, raw)
@@ -82,6 +87,8 @@ func (h *wsHub) dispatch(c *wsClient, cmd string, raw []byte) {
 		h.handleTermClose(c, raw)
 
 	// Admin operations (Phase 7).
+	case "delete_device":
+		h.handleDeleteDevice(c, raw)
 	case "create_user":
 		h.handleCreateUser(c, raw)
 	case "delete_user":
@@ -90,6 +97,19 @@ func (h *wsHub) dispatch(c *wsClient, cmd string, raw []byte) {
 		h.handleListUsers(c, raw)
 	case "get_groups":
 		h.handleGetGroups(c, raw)
+	case "query_audit":
+		h.handleQueryAudit(c, raw)
+	default:
+		// Unknown commands are attacker-controlled and can be sent in a tight
+		// loop. Count them for the close summary and record only the first
+		// one per connection so the audit trail cannot be flooded.
+		c.statUnknownCmd++
+		if !c.auditUnknownCmdLogged {
+			c.auditUnknownCmdLogged = true
+			h.audit(c, true, auditUnknownCmd, map[string]any{
+				"command": cmd,
+			})
+		}
 	}
 }
 
@@ -102,6 +122,11 @@ func (h *wsHub) requireAdmin(c *wsClient, raw []byte, replyCmd string) (ok bool)
 	}
 	// c.role is cached on first successful requireAuth; safe to read here.
 	if c.role != "admin" {
+		c.statAdminDenied++
+		h.audit(c, true, auditDenied, map[string]any{
+			"operation": strings.TrimSuffix(replyCmd, "_result"),
+			"reason":    "not_admin",
+		})
 		c.queue(mustJSON(map[string]any{
 			"cmd": replyCmd, "ok": false, "msg": "Permission denied",
 		}))
@@ -130,7 +155,21 @@ func (h *wsHub) handleGetSalt(c *wsClient, raw []byte) {
 	}
 	_ = json.Unmarshal(raw, &in)
 
-	salt, _ := h.auth.GetSalt(in.Username)
+	salt, exists := h.auth.GetSalt(in.Username)
+	// The response deliberately hides whether the user exists (fake salt),
+	// but the audit trail should not: repeated probes for a nonexistent
+	// account are a strong signal of username enumeration. Record the first
+	// probe per connection only; the close summary carries the total.
+	if !exists {
+		c.statUnknownSalt++
+		if !c.auditUnknownSaltLogged {
+			c.auditUnknownSaltLogged = true
+			h.audit(c, true, auditSaltProbe, map[string]any{
+				"username": in.Username,
+				"reason":   "unknown_user",
+			})
+		}
+	}
 	// GetSalt now returns a deterministic fake salt (16 hex chars) for
 	// unknown users — same shape as a real salt — so an attacker can't
 	// tell from this response alone whether the username exists.
@@ -148,6 +187,8 @@ func (h *wsHub) handleLogin(c *wsClient, raw []byte) {
 		Nonce    string `json:"nonce"`
 	}
 	if err := json.Unmarshal(raw, &in); err != nil {
+		c.statLoginFailures++
+		h.audit(c, true, auditLoginFail, map[string]any{"reason": "malformed_request"})
 		c.queue(mustJSON(map[string]any{"cmd": "login_result", "ok": false, "msg": "Invalid request"}))
 		return
 	}
@@ -158,7 +199,11 @@ func (h *wsHub) handleLogin(c *wsClient, raw []byte) {
 	// known account (admin). Either dimension tripping rejects the call
 	// with a uniform "credentials" error so the limit is not detectable.
 	if !h.allowLoginByIP(c) || !h.allowLoginByUsername(in.Username) {
-		h.log.Warn("ws login throttled: user=%s addr=%s", in.Username, c.addr)
+		c.statLoginFailures++
+		h.audit(c, true, auditLoginThrot, map[string]any{
+			"username": in.Username,
+			"reason":   "rate_limited",
+		})
 		time.Sleep(500 * time.Millisecond)
 		c.queue(mustJSON(map[string]any{"cmd": "login_result", "ok": false, "msg": "Invalid credentials"}))
 		// Rotate the challenge: burns the previous nonce (replay protection)
@@ -171,6 +216,11 @@ func (h *wsHub) handleLogin(c *wsClient, raw []byte) {
 	// Bind the response to the challenge we issued at connect time so that
 	// replays from a different connection can't reuse a captured response.
 	if in.Nonce == "" || in.Nonce != c.nonce {
+		c.statLoginFailures++
+		h.audit(c, true, auditLoginFail, map[string]any{
+			"username": in.Username,
+			"reason":   "invalid_challenge",
+		})
 		c.queue(mustJSON(map[string]any{"cmd": "login_result", "ok": false, "msg": "Invalid challenge"}))
 		h.rotateChallenge(c)
 		return
@@ -178,6 +228,16 @@ func (h *wsHub) handleLogin(c *wsClient, raw []byte) {
 
 	token, role, err := h.auth.VerifyLogin(in.Username, in.Response, in.Nonce)
 	if err != nil {
+		// Record whether the account exists — an attack that keeps hammering
+		// a real account (or scans for names) reads very differently from a
+		// user mistyping their own password.
+		_, exists := h.auth.GetSalt(in.Username)
+		c.statLoginFailures++
+		h.audit(c, true, auditLoginFail, map[string]any{
+			"username":    in.Username,
+			"reason":      "invalid_credentials",
+			"user_exists": exists,
+		})
 		// Fixed delay on failure: makes online brute force impractical
 		// even within the rate-limit budget, and erases the timing
 		// difference between "wrong password" and "wrong nonce".
@@ -190,10 +250,20 @@ func (h *wsHub) handleLogin(c *wsClient, raw []byte) {
 	// user who fat-fingered a few times doesn't stay throttled.
 	h.resetLoginThrottle(c, in.Username)
 
+	// Identity fields are read by audit() from hub goroutines, so publish
+	// them under h.mu.
+	h.mu.Lock()
 	c.nonce = ""
 	c.token = token
 	c.role = role
-	h.log.Info("ws login: user=%s role=%s addr=%s", in.Username, role, c.addr)
+	c.user = in.Username
+	h.mu.Unlock()
+
+	fields := c.wsRequestFields()
+	fields["method"] = "password"
+	fields["actor"] = in.Username
+	fields["role"] = role
+	h.audit(c, false, auditLoginOK, fields)
 
 	c.queue(mustJSON(map[string]any{
 		"cmd":   "login_result",
@@ -254,6 +324,7 @@ func (h *wsHub) handleDisconnect(c *wsClient, raw []byte) {
 	// Take h.mu so event-handler readers (OnResolutionChange/OnScreenFrame)
 	// get a consistent view of the watch set.
 	var closed []string
+	starts := make(map[string]time.Time)
 	h.mu.Lock()
 	if in.MultiWatch && in.ID != "" {
 		// New frontend: drop only this device; the other wall tiles keep
@@ -261,6 +332,8 @@ func (h *wsHub) handleDisconnect(c *wsClient, raw []byte) {
 		if c.isWatching(in.ID) {
 			delete(c.watchIDs, in.ID)
 			delete(c.keyframeAt, in.ID)
+			starts[in.ID] = c.watchStartedAt[in.ID]
+			delete(c.watchStartedAt, in.ID)
 			closed = append(closed, in.ID)
 		}
 	} else {
@@ -268,9 +341,11 @@ func (h *wsHub) handleDisconnect(c *wsClient, raw []byte) {
 		// one device, so clear everything.
 		for id := range c.watchIDs {
 			closed = append(closed, id)
+			starts[id] = c.watchStartedAt[id]
 		}
 		c.watchIDs = make(map[string]struct{})
 		c.keyframeAt = make(map[string]int64)
+		c.watchStartedAt = make(map[string]time.Time)
 	}
 	h.mu.Unlock()
 
@@ -285,6 +360,13 @@ func (h *wsHub) handleDisconnect(c *wsClient, raw []byte) {
 
 	// deferredCloseScreen takes h.mu, so it must run outside the lock above.
 	for _, id := range closed {
+		if !starts[id].IsZero() {
+			h.audit(c, false, auditScreenStop, map[string]any{
+				"device_id":   id,
+				"duration_ms": durationMs(starts[id]),
+				"reason":      "disconnect",
+			})
+		}
 		if h.countWatchers(id) == 0 {
 			h.deferredCloseScreen(id)
 		}
@@ -390,8 +472,10 @@ func (h *wsHub) handleConnect(c *wsClient, raw []byte) {
 	}
 
 	var stopped []string
-	var tooMany bool
+	starts := make(map[string]time.Time)
+	var tooMany, already bool
 	h.mu.Lock()
+	_, already = c.watchIDs[in.ID]
 	stopped, tooMany = applyConnectWatch(c, in.ID, in.MultiWatch)
 	// A pending deferred close means the previous session is still alive for
 	// a few seconds; cancel it so the cached resolution + IDR hot path wins.
@@ -403,10 +487,24 @@ func (h *wsHub) handleConnect(c *wsClient, raw []byte) {
 			t.Stop()
 			delete(h.screenCloseTimers, in.ID)
 		}
+		// Repeated connect (focus switch / wall re-subscribe) keeps the
+		// original start time so its audit duration covers the whole watch.
+		if _, ok := c.watchStartedAt[in.ID]; !ok {
+			c.watchStartedAt[in.ID] = time.Now()
+		}
+		for _, id := range stopped {
+			starts[id] = c.watchStartedAt[id]
+			delete(c.watchStartedAt, id)
+			delete(c.keyframeAt, id)
+		}
 	}
 	h.mu.Unlock()
 
 	if tooMany {
+		h.audit(c, true, auditScreenDenied, map[string]any{
+			"device_id": in.ID,
+			"reason":    "too_many_watches",
+		})
 		c.queue(mustJSON(reply(false, "Too many devices on one connection")))
 		return
 	}
@@ -414,6 +512,13 @@ func (h *wsHub) handleConnect(c *wsClient, raw []byte) {
 	// screen sessions are torn down outside the lock; deferredCloseScreen is
 	// a no-op while another browser still watches the device.
 	for _, id := range stopped {
+		if !starts[id].IsZero() {
+			h.audit(c, false, auditScreenStop, map[string]any{
+				"device_id":   id,
+				"duration_ms": durationMs(starts[id]),
+				"reason":      "replaced",
+			})
+		}
 		if h.countWatchers(id) == 0 {
 			h.deferredCloseScreen(id)
 		}
@@ -426,6 +531,15 @@ func (h *wsHub) handleConnect(c *wsClient, raw []byte) {
 	// next IDR (~15 s).
 	cache := h.devices.ScreenState(in.ID)
 	if cache.Active {
+		if !already {
+			h.audit(c, false, auditScreenStart, map[string]any{
+				"device_id":   in.ID,
+				"mode":        "cached",
+				"multi_watch": in.MultiWatch,
+				"width":       cache.Width,
+				"height":      cache.Height,
+			})
+		}
 		m := reply(true, "")
 		m["width"] = cache.Width
 		m["height"] = cache.Height
@@ -458,16 +572,30 @@ func (h *wsHub) handleConnect(c *wsClient, raw []byte) {
 		h.mu.Lock()
 		delete(c.watchIDs, in.ID)
 		delete(c.keyframeAt, in.ID)
+		delete(c.watchStartedAt, in.ID)
 		h.mu.Unlock()
 		msg := "Device offline"
+		reason := "device_offline"
 		if err != hub.ErrDeviceOffline {
 			msg = "Failed to start screen capture"
+			reason = "start_failed"
 			h.log.Error("SendToDevice(%s): %v", in.ID, err)
 		}
+		h.audit(c, true, auditScreenDenied, map[string]any{
+			"device_id": in.ID,
+			"reason":    reason,
+		})
 		c.queue(mustJSON(reply(false, msg)))
 		return
 	}
 	h.log.Debug("[timing] COMMAND_SCREEN_SPY sent to device=%s (cold start)", in.ID)
+	if !already {
+		h.audit(c, false, auditScreenStart, map[string]any{
+			"device_id":   in.ID,
+			"mode":        "started",
+			"multi_watch": in.MultiWatch,
+		})
+	}
 
 	c.queue(mustJSON(reply(true, "")))
 }
@@ -558,7 +686,10 @@ func (h *wsHub) handleRdpReset(c *wsClient, raw []byte) {
 	}
 	deviceID := h.resolveWatchDevice(c, raw)
 	if deviceID == "" {
-		h.log.Warn("rdp_reset: no device watched (addr=%s role=%s)", c.addr, c.role)
+		h.audit(c, true, auditRdpReset, map[string]any{
+			"ok":     false,
+			"reason": "no_device",
+		})
 		return
 	}
 	// CMD_RESTORE_CONSOLE must go through the screen sub-conn — the client
@@ -566,24 +697,47 @@ func (h *wsHub) handleRdpReset(c *wsClient, raw []byte) {
 	// the screen sub-conn (see client/ScreenManager.cpp:996). Sending on the
 	// main conn would silently no-op.
 	if err := h.devices.SendToScreen(deviceID, []byte{protocol.CmdRestoreConsole}); err != nil {
-		h.log.Warn("rdp_reset: device=%s: %v", deviceID, err)
+		h.audit(c, true, auditRdpReset, map[string]any{
+			"device_id": deviceID,
+			"ok":        false,
+			"reason":    "send_failed",
+			"error":     err.Error(),
+		})
 		return
 	}
-	h.log.Info("rdp_reset sent: device=%s", deviceID)
+	h.audit(c, false, auditRdpReset, map[string]any{
+		"device_id": deviceID,
+		"ok":        true,
+	})
 }
 
 func (h *wsHub) handleGetDevices(c *wsClient, raw []byte) {
 	if !h.requireAuth(c, raw, "device_list") {
 		return
 	}
-	devices := h.devices.ListDevices()
 	c.queue(mustJSON(map[string]any{
 		"cmd":     "device_list",
 		"ok":      true,
-		"devices": devices,
+		"devices": h.listDevicesWithOffline(),
 	}))
 }
 
+// listDevicesWithOffline returns the online snapshot followed by historical
+// devices that are not currently online. The online-ID set is derived from the
+// same snapshot, so a device reconnecting between the two lookups cannot appear
+// twice. With no history store wired up this is just the online list.
+func (h *wsHub) listDevicesWithOffline() []hub.DeviceInfo {
+	devices := h.devices.ListDevices()
+	if h.history == nil {
+		return devices
+	}
+	online := make(map[string]struct{}, len(devices))
+	for _, d := range devices {
+		online[d.ID] = struct{}{}
+	}
+	return append(devices, h.history.Offline(online)...)
+}
+
 // requireAuth validates the token embedded in raw against the authenticator's
 // session store (not against c.token). Tokens live independently of WS
 // connections — the browser may reconnect after a visibility/network blip and
@@ -596,21 +750,46 @@ func (h *wsHub) requireAuth(c *wsClient, raw []byte, replyCmd string) bool {
 	}
 	_ = json.Unmarshal(raw, &in)
 	if in.Token == "" {
+		h.auditBadToken(c, replyCmd, "missing_token")
 		c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": false}))
 		return false
 	}
 	sess, err := h.auth.ValidateToken(in.Token)
 	if err != nil {
+		h.auditBadToken(c, replyCmd, "invalid_token")
 		c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": false}))
 		return false
 	}
+	resumed := false
+	h.mu.Lock()
 	if c.token == "" {
 		c.token = in.Token
 		c.role = sess.Role
+		c.user = sess.Username
+		resumed = true
+	}
+	h.mu.Unlock()
+	if resumed {
+		h.audit(c, false, auditSession, map[string]any{"method": "token"})
 	}
 	return true
 }
 
+// auditBadToken counts rejected tokens and records only the first one per
+// connection: an attacker can loop protected commands with garbage tokens,
+// and one line plus the close-summary count is enough to see it.
+func (h *wsHub) auditBadToken(c *wsClient, replyCmd, reason string) {
+	c.statInvalidToken++
+	if c.auditInvalidTokenLogged {
+		return
+	}
+	c.auditInvalidTokenLogged = true
+	h.audit(c, true, auditBadToken, map[string]any{
+		"command": strings.TrimSuffix(replyCmd, "_result"),
+		"reason":  reason,
+	})
+}
+
 // handleMouse forwards one mouse event from the browser to the device's
 // screen sub-connection as a COMMAND_SCREEN_CONTROL packet carrying a
 // single MSG64. Mirrors the C++ CWebService::HandleMouse path
@@ -778,19 +957,39 @@ func (h *wsHub) handleClipboardSet(c *wsClient, raw []byte) {
 	}
 	deviceID := h.resolveWatchDevice(c, raw)
 	if deviceID == "" {
+		h.audit(c, true, auditClipSet, map[string]any{
+			"ok":     false,
+			"reason": "no_device",
+		})
 		return
 	}
 	gbk, err := simplifiedchinese.GBK.NewEncoder().Bytes([]byte(in.Text))
 	if err != nil {
-		h.log.Warn("clipboard_set: GBK encode failed: %v", err)
+		h.audit(c, true, auditClipSet, map[string]any{
+			"device_id": deviceID,
+			"ok":        false,
+			"reason":    "encode_failed",
+			"error":     err.Error(),
+		})
 		return
 	}
 	payload := append([]byte{protocol.CommandScreenSetClipboard}, gbk...)
 	if err := h.devices.SendToScreen(deviceID, payload); err != nil {
-		h.log.Warn("clipboard_set: device=%s: %v", deviceID, err)
+		h.audit(c, true, auditClipSet, map[string]any{
+			"device_id": deviceID,
+			"ok":        false,
+			"reason":    "send_failed",
+			"error":     err.Error(),
+		})
 		return
 	}
-	h.log.Info("clipboard_set sent: device=%s len=%d", deviceID, len(gbk))
+	// Record the size only — clipboard contents may be sensitive.
+	h.audit(c, false, auditClipSet, map[string]any{
+		"device_id":   deviceID,
+		"ok":          true,
+		"bytes":       len(gbk),
+		"source_utf8": len(in.Text),
+	})
 }
 
 // handleClipboardGet asks the remote device for its clipboard text via
@@ -802,12 +1001,25 @@ func (h *wsHub) handleClipboardGet(c *wsClient, raw []byte) {
 	}
 	deviceID := h.resolveWatchDevice(c, raw)
 	if deviceID == "" {
+		h.audit(c, true, auditClipGet, map[string]any{
+			"ok":     false,
+			"reason": "no_device",
+		})
 		return
 	}
 	if err := h.devices.SendToScreen(deviceID, []byte{protocol.CommandScreenGetClipboard}); err != nil {
-		h.log.Warn("clipboard_get: device=%s: %v", deviceID, err)
+		h.audit(c, true, auditClipGet, map[string]any{
+			"device_id": deviceID,
+			"ok":        false,
+			"reason":    "send_failed",
+			"error":     err.Error(),
+		})
 		return
 	}
+	h.audit(c, false, auditClipGet, map[string]any{
+		"device_id": deviceID,
+		"ok":        true,
+	})
 }
 
 // handleCreateUser provisions a new web account. Admin-only. Mirrors the
@@ -826,6 +1038,10 @@ func (h *wsHub) handleCreateUser(c *wsClient, raw []byte) {
 		AllowedGroups []string `json:"allowed_groups"`
 	}
 	if err := json.Unmarshal(raw, &in); err != nil {
+		h.audit(c, true, auditUserCreate, map[string]any{
+			"ok":     false,
+			"reason": "invalid_json",
+		})
 		c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": false, "msg": "Invalid JSON"}))
 		return
 	}
@@ -833,14 +1049,116 @@ func (h *wsHub) handleCreateUser(c *wsClient, raw []byte) {
 		in.Role = "viewer"
 	}
 	if err := h.auth.CreateUser(in.Username, in.Password, in.Role, in.AllowedGroups); err != nil {
+		h.audit(c, true, auditUserCreate, map[string]any{
+			"target":      in.Username,
+			"target_role": in.Role,
+			"ok":          false,
+			"reason":      "create_failed",
+			"error":       err.Error(),
+		})
 		c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": false, "msg": err.Error()}))
 		return
 	}
-	h.log.Info("user created by %s: name=%s role=%s groups=%d",
+	h.audit(c, false, auditUserCreate, map[string]any{
-		c.role, in.Username, in.Role, len(in.AllowedGroups))
+		"target":      in.Username,
+		"target_role": in.Role,
+		"groups":      len(in.AllowedGroups),
+		"ok":          true,
+	})
 	c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": true}))
 }
 
+// handleDeleteDevice implements the device list's "Delete" action.
+//
+// The meaning depends on liveness, matching the MFC client's
+// OnOnlineUninstall: an online agent is told to uninstall itself with the
+// single-byte TOKEN_UNINSTALL command; an offline device has no agent to
+// talk to. Either way the persisted history record is removed as well, so
+// the deleted device does not linger in the offline list.
+//
+// Admin-only: this is destructive and irreversible.
+func (h *wsHub) handleDeleteDevice(c *wsClient, raw []byte) {
+	const replyCmd = "delete_device_result"
+	if !h.requireAdmin(c, raw, replyCmd) {
+		return
+	}
+	var in struct {
+		ID string `json:"id"`
+	}
+	if err := json.Unmarshal(raw, &in); err != nil || in.ID == "" {
+		h.audit(c, true, auditDeviceAdmin, map[string]any{
+			"ok":     false,
+			"reason": "invalid_id",
+		})
+		c.queue(mustJSON(map[string]any{
+			"cmd": replyCmd, "ok": false, "msg": "Invalid device id",
+		}))
+		return
+	}
+
+	if h.devices.IsOnline(in.ID) {
+		err := h.devices.SendToDevice(in.ID, []byte{protocol.CommandUninstall})
+		if err == nil {
+			// Drop the record too: after the agent uninstalls itself it will
+			// never log in again, so keeping it would leave a dead entry in
+			// the offline list. The disconnect event that follows finds no
+			// record and is a no-op.
+			if h.history != nil {
+				h.history.Remove(in.ID)
+			}
+			h.audit(c, false, auditDeviceAdmin, map[string]any{
+				"device_id": in.ID,
+				"mode":      "uninstall",
+				"ok":        true,
+			})
+			h.broadcastAuthenticated(`{"cmd":"devices_changed"}`)
+			c.queue(mustJSON(map[string]any{
+				"cmd": replyCmd, "ok": true, "id": in.ID, "mode": "uninstall",
+			}))
+			return
+		}
+		// Lost the race with a disconnect between IsOnline and the send:
+		// fall through to removing the (now offline) history record.
+		if !errors.Is(err, hub.ErrDeviceOffline) {
+			h.audit(c, true, auditDeviceAdmin, map[string]any{
+				"device_id": in.ID,
+				"mode":      "uninstall",
+				"ok":        false,
+				"reason":    "uninstall_failed",
+				"error":     err.Error(),
+			})
+			c.queue(mustJSON(map[string]any{
+				"cmd": replyCmd, "ok": false, "msg": err.Error(),
+			}))
+			return
+		}
+	}
+
+	if h.history == nil || !h.history.Remove(in.ID) {
+		h.audit(c, true, auditDeviceAdmin, map[string]any{
+			"device_id": in.ID,
+			"mode":      "removed",
+			"ok":        false,
+			"reason":    "not_found",
+		})
+		c.queue(mustJSON(map[string]any{
+			"cmd": replyCmd, "ok": false, "msg": "Device not found",
+		}))
+		return
+	}
+	h.audit(c, false, auditDeviceAdmin, map[string]any{
+		"device_id": in.ID,
+		"mode":      "removed",
+		"ok":        true,
+	})
+	// Other browsers (and this one) refresh their lists; the reply below
+	// still gives the initiator a precise result/toast.
+	h.broadcastAuthenticated(`{"cmd":"devices_changed"}`)
+	c.queue(mustJSON(map[string]any{
+		"cmd": replyCmd, "ok": true, "id": in.ID, "mode": "removed",
+	}))
+}
+
 // handleDeleteUser removes an account and revokes any of its live sessions.
 // Admin-only. The bootstrap "admin" account is rejected at the wsauth layer.
 func (h *wsHub) handleDeleteUser(c *wsClient, raw []byte) {
@@ -852,14 +1170,27 @@ func (h *wsHub) handleDeleteUser(c *wsClient, raw []byte) {
 		Username string `json:"username"`
 	}
 	if err := json.Unmarshal(raw, &in); err != nil {
+		h.audit(c, true, auditUserDelete, map[string]any{
+			"ok":     false,
+			"reason": "invalid_json",
+		})
 		c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": false, "msg": "Invalid JSON"}))
 		return
 	}
 	if err := h.auth.DeleteUser(in.Username); err != nil {
+		h.audit(c, true, auditUserDelete, map[string]any{
+			"target": in.Username,
+			"ok":     false,
+			"reason": "delete_failed",
+			"error":  err.Error(),
+		})
 		c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": false, "msg": err.Error()}))
 		return
 	}
-	h.log.Info("user deleted by %s: name=%s", c.role, in.Username)
+	h.audit(c, false, auditUserDelete, map[string]any{
+		"target": in.Username,
+		"ok":     true,
+	})
 	c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": true}))
 }
 
@@ -949,34 +1280,57 @@ func (h *wsHub) handleTermOpen(c *wsClient, raw []byte) {
 	// screen path in handleConnect.
 	h.mu.Lock()
 	if c.termWatching != "" && c.termWatching != in.ID {
+		active := c.termWatching
 		h.mu.Unlock()
+		h.audit(c, true, auditTermDenied, map[string]any{
+			"device_id": in.ID,
+			"reason":    "other_terminal_open",
+			"active":    active,
+		})
 		c.queue(mustJSON(map[string]any{
 			"cmd": replyCmd, "ok": false,
 			"msg": "Close current terminal before opening another",
 		}))
 		return
 	}
+	newSession := c.termWatching != in.ID
 	c.termWatching = in.ID
+	c.termCloseReason = ""
+	if newSession || c.termStartedAt.IsZero() {
+		c.termStartedAt = time.Now()
+	}
 	h.mu.Unlock()
 
 	if err := h.devices.OpenTerminalSession(in.ID); err != nil {
 		h.mu.Lock()
 		c.termWatching = ""
+		c.termStartedAt = time.Time{}
 		h.mu.Unlock()
 		msg := "Device offline"
+		reason := "device_offline"
 		switch err {
 		case hub.ErrTerminalBusy:
 			msg = "Terminal already open by another viewer"
+			reason = "terminal_busy"
 		case hub.ErrDeviceOffline:
 			msg = "Device offline"
 		default:
 			msg = "Failed to start terminal"
+			reason = "start_failed"
 			h.log.Error("OpenTerminalSession(%s): %v", in.ID, err)
 		}
+		h.audit(c, true, auditTermDenied, map[string]any{
+			"device_id": in.ID,
+			"reason":    reason,
+		})
 		c.queue(mustJSON(map[string]any{"cmd": replyCmd, "ok": false, "msg": msg}))
 		return
 	}
-	h.log.Info("term_open: device=%s role=%s", in.ID, c.role)
+	if newSession {
+		h.audit(c, false, auditTermStart, map[string]any{
+			"device_id": in.ID,
+		})
+	}
 }
 
 // handleTermInput forwards xterm.js keystrokes to the device's shell
@@ -997,7 +1351,10 @@ func (h *wsHub) handleTermInput(c *wsClient, raw []byte) {
 	if in.ID == "" || in.Data == "" {
 		return
 	}
-	if c.termWatching != in.ID {
+	h.mu.RLock()
+	watching := c.termWatching == in.ID
+	h.mu.RUnlock()
+	if !watching {
 		return // someone else's session, or no session
 	}
 	_ = h.devices.SendToTerminal(in.ID, []byte(in.Data))
@@ -1021,7 +1378,10 @@ func (h *wsHub) handleTermResize(c *wsClient, raw []byte) {
 	if in.ID == "" || in.Cols <= 0 || in.Rows <= 0 {
 		return
 	}
-	if c.termWatching != in.ID {
+	h.mu.RLock()
+	watching := c.termWatching == in.ID
+	h.mu.RUnlock()
+	if !watching {
 		return
 	}
 	if !h.devices.TerminalIsPTY(in.ID) {
@@ -1043,7 +1403,15 @@ func (h *wsHub) handleTermClose(c *wsClient, raw []byte) {
 	if err := json.Unmarshal(raw, &in); err != nil || in.ID == "" {
 		return
 	}
-	if c.termWatching != in.ID {
+	h.mu.Lock()
+	watching := c.termWatching == in.ID
+	if watching {
+		// Consumed by OnTerminalClosed for the remote.terminal.stop audit
+		// record (it fires synchronously inside CloseTerminalSession).
+		c.termCloseReason = "user"
+	}
+	h.mu.Unlock()
+	if !watching {
 		return
 	}
 	h.devices.CloseTerminalSession(in.ID)

server/web/index.html

@@ -374,6 +374,107 @@
         .user-msg.success { background: rgba(39, 174, 96, 0.2); color: #2ecc71; }
         .user-msg.error { background: rgba(231, 76, 60, 0.2); color: #e74c3c; }
 
+        /* ===== Audit Log page ===== */
+        .icon-btn.audit { background: linear-gradient(135deg, #b9770e 0%, #e67e22 100%); display: none; }
+        .icon-btn.audit.visible { display: inline-flex; }
+        .icon-btn.audit:hover { box-shadow: 0 4px 12px rgba(230, 126, 34, 0.4); }
+
+        #audit-page { max-width: 1500px; margin: 0 auto; }
+        .audit-title-wrap { display: flex; align-items: center; gap: 12px; }
+        .audit-filters {
+            display: grid;
+            grid-template-columns: repeat(auto-fit, minmax(170px, 1fr));
+            gap: 10px 14px;
+            background: rgba(22, 33, 62, 0.8);
+            border: 1px solid rgba(255,255,255,0.06);
+            border-radius: 12px;
+            padding: 16px;
+            margin-bottom: 14px;
+        }
+        .audit-filters label {
+            display: flex;
+            flex-direction: column;
+            gap: 5px;
+            font-size: 12px;
+            color: #9aa4b2;
+        }
+        .audit-filters input[type="text"],
+        .audit-filters input[type="datetime-local"],
+        .audit-filters select {
+            padding: 8px 10px;
+            border: 1px solid rgba(255,255,255,0.1);
+            border-radius: 6px;
+            background: rgba(15, 52, 96, 0.7);
+            color: #fff;
+            font-size: 13px;
+            outline: none;
+            min-width: 0;
+        }
+        .audit-filters input:focus, .audit-filters select:focus { border-color: #e67e22; }
+        .audit-filters label.audit-warn {
+            flex-direction: row;
+            align-items: center;
+            padding-top: 18px;
+        }
+        .audit-filters label.audit-warn input { width: 15px; height: 15px; margin-right: 6px; }
+        .audit-actions { display: flex; gap: 10px; align-items: flex-end; }
+        .audit-actions button {
+            padding: 9px 18px;
+            border: none;
+            border-radius: 6px;
+            font-size: 13px;
+            font-weight: 600;
+            cursor: pointer;
+        }
+        .audit-search-btn { background: linear-gradient(135deg, #b9770e 0%, #e67e22 100%); color: #fff; }
+        .audit-search-btn:hover { transform: translateY(-1px); }
+        .audit-reset-btn { background: rgba(255,255,255,0.08); color: #ccc; }
+        .audit-reset-btn:hover { background: rgba(255,255,255,0.15); }
+        .audit-status { color: #888; font-size: 12px; margin-bottom: 10px; min-height: 16px; }
+        .audit-status.warn { color: #e67e22; }
+        .audit-table-wrap {
+            overflow-x: auto;
+            border: 1px solid rgba(255,255,255,0.06);
+            border-radius: 12px;
+            background: rgba(22, 33, 62, 0.8);
+        }
+        .audit-table { width: 100%; border-collapse: collapse; font-size: 12.5px; }
+        .audit-table th {
+            text-align: left;
+            padding: 10px 12px;
+            color: #9aa4b2;
+            font-weight: 600;
+            white-space: nowrap;
+            border-bottom: 1px solid rgba(255,255,255,0.1);
+            background: rgba(15, 52, 96, 0.5);
+        }
+        .audit-table td {
+            padding: 9px 12px;
+            border-bottom: 1px solid rgba(255,255,255,0.04);
+            color: #d5dbe3;
+            vertical-align: top;
+            white-space: nowrap;
+        }
+        .audit-table tr:last-child td { border-bottom: none; }
+        .audit-table tr:hover td { background: rgba(230, 126, 34, 0.06); }
+        .audit-table td.audit-details {
+            white-space: normal;
+            word-break: break-all;
+            color: #8f9aa8;
+            min-width: 220px;
+            font-family: ui-monospace, Consolas, monospace;
+            font-size: 11.5px;
+        }
+        .audit-level { padding: 2px 8px; border-radius: 10px; font-size: 11px; }
+        .audit-level.info { background: rgba(76, 175, 80, 0.15); color: #4caf50; }
+        .audit-level.warn { background: rgba(230, 126, 34, 0.18); color: #e67e22; }
+        .audit-empty { padding: 40px; text-align: center; color: #666; }
+        @media (max-width: 640px) {
+            .audit-filters { grid-template-columns: 1fr 1fr; }
+            .audit-actions { grid-column: 1 / -1; }
+            .audit-table td, .audit-table th { padding: 8px; }
+        }
+
         /* Generic confirmation modal (compact yes/no dialog, e.g. logout) —— 复用 .modal-overlay
            做遮罩，自带一套紧凑布局 + 危险/取消双按钮风格。 */
         .confirm-modal-content {
@@ -455,11 +556,43 @@
             border-color: rgba(233, 69, 96, 0.3);
         }
         .device-card:hover::before { opacity: 1; }
-        /* 终端图标按钮：右上角，独立于卡片本体点击事件（onclick stopPropagation） */
+        /* 离线设备：只展示，无点击/终端操作。虚线边框 + 灰显与在线卡片区分。 */
-        .device-card .card-term-btn {
+        .device-card.offline {
+            opacity: 0.55;
+            cursor: not-allowed;
+            border-style: dashed;
+        }
+        .device-card.offline:hover {
+            transform: none;
+            box-shadow: none;
+            border-color: rgba(255,255,255,0.05);
+        }
+        .device-card.offline::before { display: none; }
+        .device-card.offline h3 { color: #999; }
+        .device-card .last-seen {
+            margin-top: 8px;
+            font-size: 12px;
+            color: #777;
+            white-space: nowrap;
+            overflow: hidden;
+            text-overflow: ellipsis;
+        }
+        .device-grid.list-view .device-card .last-seen {
+            margin-top: 0;
+            max-width: 200px;
+            flex-shrink: 1;
+        }
+        /* 卡片操作图标（终端 / 删除）：右上角，独立于卡片本体点击事件
+           （onclick stopPropagation）。List 视图卡片是一行，改为垂直居中。 */
+        .device-card .card-actions {
             position: absolute;
             top: 12px;
             right: 12px;
+            display: flex;
+            gap: 6px;
+            z-index: 1;
+        }
+        .device-card .card-icon-btn {
             width: 32px;
             height: 32px;
             border: none;
@@ -471,11 +604,16 @@
             align-items: center;
             justify-content: center;
             transition: all 0.15s;
-            z-index: 1;
         }
+        .device-card .card-icon-btn:hover { background: rgba(255,255,255,0.14); color: #fff; }
+        .device-card .card-icon-btn:active { transform: scale(0.92); }
         .device-card .card-term-btn:hover { background: rgba(76, 175, 80, 0.25); color: #4caf50; }
-        .device-card .card-term-btn:active { transform: scale(0.92); }
+        .device-card .card-del-btn:hover { background: rgba(231, 76, 60, 0.25); color: #e74c3c; }
-        .device-card h3 { padding-right: 40px; }   /* 给终端图标让位 */
+        .device-card h3 { padding-right: 86px; }   /* 给右上角两个操作图标让位 */
+        .device-grid.list-view .device-card .card-actions {
+            top: 50%;
+            transform: translateY(-50%);
+        }
 
         /* ====== 终端页面 ====== */
         #term-page {
@@ -605,9 +743,11 @@
             display: flex;
             align-items: center;
             padding: 12px 16px;
+            padding-right: 100px;   /* 给垂直居中的操作图标列让位 */
             gap: 20px;
         }
         .device-grid.list-view .device-card::before { display: none; }
+        .device-grid.list-view .device-card h3 { padding-right: 0; }
         .device-grid.list-view .device-card h3 {
             min-width: 180px;
             margin-bottom: 0;
@@ -669,6 +809,20 @@
         }
         .stats-bar .stat { color: #888; }
         .stats-bar .stat strong { color: #e94560; }
+        /* 离线设备开关：服务端宣告 offlineDevices 能力后才显示（C++ 服务端没有该能力位）。 */
+        .stats-bar .stat.offline-toggle {
+            display: none;
+            align-items: center;
+            gap: 6px;
+            margin-left: auto;
+            cursor: pointer;
+            user-select: none;
+        }
+        .stats-bar .stat.offline-toggle.visible { display: flex; }
+        .stats-bar .stat.offline-toggle input {
+            accent-color: #e94560;
+            cursor: pointer;
+        }
 
         #screen-page {
             position: fixed;
@@ -1464,6 +1618,14 @@
                         <path d="M16 3.13a4 4 0 0 1 0 7.75"/>
                     </svg>
                 </button>
+                <button class="icon-btn audit" id="audit-btn" onclick="openAuditPage()" title="Audit Log" aria-label="Audit Log">
+                    <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+                        <path d="M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z"/>
+                        <polyline points="14 2 14 8 20 8"/>
+                        <line x1="8" y1="13" x2="16" y2="13"/>
+                        <line x1="8" y1="17" x2="16" y2="17"/>
+                    </svg>
+                </button>
                 <button class="icon-btn logout" onclick="logout()" title="Logout" aria-label="Logout">
                     <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
                         <path d="M9 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h4"/>
@@ -1476,6 +1638,11 @@
         <div id="stats-bar" class="stats-bar">
             <div class="stat">Total: <strong id="stat-total">0</strong></div>
             <div class="stat">Showing: <strong id="stat-showing">0</strong></div>
+            <label class="stat offline-toggle" id="offline-toggle"
+                   title="Show devices that have connected before but are offline now">
+                <input type="checkbox" id="show-offline" onchange="onOfflineToggle(this.checked)">
+                Offline
+            </label>
         </div>
         <div id="device-list" class="device-grid"></div>
         <div id="pagination" class="pagination"></div>
@@ -1612,6 +1779,72 @@
         </div>
     </div>
 
+    <!-- Audit Log Page (admin only) -->
+    <div id="audit-page" class="page">
+        <div class="page-header">
+            <div class="audit-title-wrap">
+                <button class="back-btn" onclick="showPage('devices-page')" title="Back to devices">&#8592;</button>
+                <h2>Audit Log <span id="audit-count" class="device-count">0</span></h2>
+            </div>
+            <div class="toolbar">
+                <button class="view-btn" onclick="queryAudit(0)" title="Reload newest records">Refresh</button>
+            </div>
+        </div>
+        <div class="audit-filters">
+            <label>From
+                <input type="datetime-local" id="audit-from" onkeydown="if(event.key==='Enter')queryAudit(0)">
+            </label>
+            <label>To
+                <input type="datetime-local" id="audit-to" onkeydown="if(event.key==='Enter')queryAudit(0)">
+            </label>
+            <label>Event (exact or prefix)
+                <input type="text" id="audit-event" list="audit-event-options" placeholder="e.g. web.* or web.login.failure"
+                       onkeydown="if(event.key==='Enter')queryAudit(0)">
+            </label>
+            <datalist id="audit-event-options"></datalist>
+            <label>Actor
+                <input type="text" id="audit-actor" placeholder="username" onkeydown="if(event.key==='Enter')queryAudit(0)">
+            </label>
+            <label>IP
+                <input type="text" id="audit-ip" placeholder="203.0.113.1" onkeydown="if(event.key==='Enter')queryAudit(0)">
+            </label>
+            <label>Device ID
+                <input type="text" id="audit-device" placeholder="device id" onkeydown="if(event.key==='Enter')queryAudit(0)">
+            </label>
+            <label>Keyword
+                <input type="text" id="audit-keyword" placeholder="reason, target, ..." onkeydown="if(event.key==='Enter')queryAudit(0)">
+            </label>
+            <label>Limit
+                <select id="audit-limit">
+                    <option value="50">50</option>
+                    <option value="100" selected>100</option>
+                    <option value="200">200</option>
+                    <option value="500">500</option>
+                </select>
+            </label>
+            <label class="audit-warn">
+                <input type="checkbox" id="audit-warn-only"> Warnings only
+            </label>
+            <div class="audit-actions">
+                <button class="audit-search-btn" onclick="queryAudit(0)">Search</button>
+                <button class="audit-reset-btn" onclick="resetAuditFilters()">Reset</button>
+            </div>
+        </div>
+        <div id="audit-status" class="audit-status"></div>
+        <div class="audit-table-wrap">
+            <table class="audit-table">
+                <thead>
+                    <tr>
+                        <th>Time</th><th>Level</th><th>Event</th><th>Actor</th>
+                        <th>Role</th><th>IP</th><th>Device</th><th>Details</th>
+                    </tr>
+                </thead>
+                <tbody id="audit-rows"></tbody>
+            </table>
+        </div>
+        <div id="audit-pagination" class="pagination"></div>
+    </div>
+
     <!-- User Management Modal -->
     <div class="modal-overlay" id="users-modal">
         <div class="modal-content">
@@ -1660,6 +1893,26 @@
         </div>
     </div>
 
+    <!-- Delete Device Confirmation Modal（离线=删除历史记录；在线=下发卸载主机） -->
+    <div class="modal-overlay" id="delete-device-modal" onclick="if(event.target===this)cancelDeleteDevice()">
+        <div class="confirm-modal-content">
+            <div class="confirm-modal-icon">
+                <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+                    <polyline points="3 6 5 6 21 6"/>
+                    <path d="M19 6l-1 14a2 2 0 0 1-2 2H8a2 2 0 0 1-2-2L5 6"/>
+                    <path d="M10 11v6"/><path d="M14 11v6"/>
+                    <path d="M9 6V4a1 1 0 0 1 1-1h4a1 1 0 0 1 1 1v2"/>
+                </svg>
+            </div>
+            <h3 id="delete-device-title">Delete Device</h3>
+            <p id="delete-device-msg"></p>
+            <div class="confirm-modal-actions">
+                <button class="cancel-btn" onclick="cancelDeleteDevice()">Cancel</button>
+                <button class="danger-btn" id="delete-device-confirm" onclick="confirmDeleteDevice()">Delete</button>
+            </div>
+        </div>
+    </div>
+
     <script src="__BASE_PATH__/static/xterm.js"></script>
     <script src="__BASE_PATH__/static/xterm-fit.js"></script>
 
@@ -1703,7 +1956,15 @@
         };
 
         // 服务端能力协商：旧 C++ / Go 服务端没有 caps，前端隐藏 Wall。
-        let serverCaps = { multiWatch: false, keyframeRequest: false };
+        let serverCaps = { multiWatch: false, keyframeRequest: false, offlineDevices: false, auditLog: false };
+
+        // 离线设备开关：localStorage 只保存用户偏好，是否可用由服务端能力位决定。
+        // 关闭时只影响 Grid/List；Wall 侧边栏始终列出离线设备（灰显、不可操作）。
+        const SHOW_OFFLINE_STORAGE_KEY = 'showOfflineDevices';
+        let showOffline = false;
+        try {
+            showOffline = localStorage.getItem(SHOW_OFFLINE_STORAGE_KEY) === '1';
+        } catch (e) { /* 隐私模式下 localStorage 可能不可用 */ }
         let wall = {
             active: false,
             layout: isTouchDevice ? 4 : 9,
@@ -2120,9 +2381,13 @@
                     // 能力协商：旧 C++ / Go 服务端没有 caps → 隐藏 Wall，保持单设备行为。
                     serverCaps = {
                         multiWatch: !!(msg.caps && msg.caps.multiWatch),
-                        keyframeRequest: !!(msg.caps && msg.caps.keyframeRequest)
+                        keyframeRequest: !!(msg.caps && msg.caps.keyframeRequest),
+                        offlineDevices: !!(msg.caps && msg.caps.offlineDevices),
+                        auditLog: !!(msg.caps && msg.caps.auditLog)
                     };
                     updateWallAvailability();
+                    applyOfflineCapability();
+                    updateAdminButtons();
                     console.log('Received challenge nonce; caps=', serverCaps);
                     break;
                 case 'salt':
@@ -2140,24 +2405,25 @@
                         localStorage.setItem('token', token);
                         localStorage.setItem('role', currentUserRole);
                         document.getElementById('login-error').textContent = '';
-                        // Show Users button for admin only
+                        // Show Users / Audit Log buttons for admin only
-                        const usersBtn = document.getElementById('users-btn');
+                        updateAdminButtons();
-                        if (currentUserRole === 'admin') {
-                            usersBtn.classList.add('visible');
-                        } else {
-                            usersBtn.classList.remove('visible');
-                        }
                         showPage('devices-page');
                         getDevices();
                     } else {
                         document.getElementById('login-error').textContent = msg.msg || 'Login failed';
                     }
                     break;
+                case 'audit_result':
+                    handleAuditResult(msg);
+                    break;
                 case 'device_list':
                     if (msg.ok === false) {
                         // Token invalid (e.g., server restarted), go back to login
                         token = null;
                         localStorage.removeItem('token');
+                        localStorage.removeItem('role');
+                        currentUserRole = 'viewer';
+                        updateAdminButtons();
                         showPage('login-page');
                         break;
                     }
@@ -2370,6 +2636,15 @@
                         showUserMsg(msg.msg || 'Failed to delete user', true);
                     }
                     break;
+                case 'delete_device_result':
+                    if (msg.ok) {
+                        // mode=uninstall：命令已下发，设备稍后自行断开；
+                        // mode=removed：历史记录已删除，刷新后卡片消失。
+                        getDevices();
+                    } else {
+                        alert(msg.msg || 'Failed to delete device');
+                    }
+                    break;
                 case 'list_users_result':
                     if (msg.ok) {
                         renderUsersList(msg.users);
@@ -3091,6 +3366,7 @@
 
         function wallTooltipHtml(d) {
             // 与 Grid 模式 device-card 的字段/顺序保持一致。
+            const offline = d.online === false;
             const screenInfo = escapeHtml(d.screen || '-');
             const rtt = d.rtt || '-';
             const activeWin = d.activeWindow || '';
@@ -3101,11 +3377,14 @@
                 '</div>' +
                 '<div class="info"><span class="info-label">OS:</span> ' + escapeHtml(d.os || '-') + '</div>' +
                 '<div class="meta-row">' +
-                    '<span class="meta-item rtt ' + getRttClass(rtt) + '">RTT: ' + escapeHtml(rtt) + '</span>' +
+                    (offline
+                        ? '<span class="meta-item offline-badge">Offline</span>'
+                        : '<span class="meta-item rtt ' + getRttClass(rtt) + '">RTT: ' + escapeHtml(rtt) + '</span>') +
                     '<span class="meta-item">Ver: ' + escapeHtml(d.version || '-') + '</span>' +
                     '<span class="meta-item">' + screenInfo + '</span>' +
                 '</div>' +
-                (activeWin ? '<div class="active-window' + (isWindowBusy(activeWin) ? ' busy' : '') + '">' +
+                (offline ? '<div class="last-seen">Last seen: ' + escapeHtml(formatLastSeen(d.last_seen)) + '</div>' : '') +
+                (!offline && activeWin ? '<div class="active-window' + (isWindowBusy(activeWin) ? ' busy' : '') + '">' +
                     escapeHtml(activeWin) + '</div>' : '');
         }
 
@@ -3749,8 +4028,14 @@
             }
         }
 
+        function scopeDevices() {
+            // Total / Showing 都基于当前范围：未勾选 Offline 时只统计在线设备。
+            if (showOffline) return devices;
+            return devices.filter(d => d.online !== false);
+        }
+
         function getFilteredDevices() {
-            let filtered = devices;
+            let filtered = scopeDevices();
             if (searchQuery) {
                 const q = searchQuery.toLowerCase();
                 filtered = filtered.filter(d =>
@@ -3766,6 +4051,37 @@
             return filtered;
         }
 
+        function applyOfflineCapability() {
+            const label = document.getElementById('offline-toggle');
+            const cb = document.getElementById('show-offline');
+            if (!label || !cb) return;
+            const supported = !!serverCaps.offlineDevices;
+            label.classList.toggle('visible', supported);
+            if (!supported) showOffline = false;
+            cb.checked = showOffline;
+            renderDeviceList();
+        }
+
+        function onOfflineToggle(checked) {
+            showOffline = !!checked;
+            try {
+                localStorage.setItem(SHOW_OFFLINE_STORAGE_KEY, showOffline ? '1' : '0');
+            } catch (e) { /* ignore */ }
+            currentPage = 1;
+            renderDeviceList();
+        }
+
+        function formatLastSeen(ts) {
+            if (!ts) return 'unknown';
+            const secs = Math.max(0, Math.floor(Date.now() / 1000 - ts));
+            if (secs < 60) return 'just now';
+            if (secs < 3600) return Math.floor(secs / 60) + 'm ago';
+            if (secs < 86400) return Math.floor(secs / 3600) + 'h ago';
+            const days = Math.floor(secs / 86400);
+            if (days < 30) return days + 'd ago';
+            return new Date(ts * 1000).toLocaleDateString();
+        }
+
         function onSearchChange() {
             searchQuery = document.getElementById('search-input').value;
             document.getElementById('search-clear').style.display = searchQuery ? 'block' : 'none';
@@ -3865,9 +4181,11 @@
             const start = (currentPage - 1) * ps;
             const pageDevices = filtered.slice(start, start + ps);
 
-            // Update stats
+            // Update stats. Total is the current scope (online-only unless the
-            document.getElementById('device-count').textContent = devices.length;
+            // Offline toggle is on); Showing is after the search filter.
-            document.getElementById('stat-total').textContent = devices.length;
+            const scope = scopeDevices();
+            document.getElementById('device-count').textContent = scope.length;
+            document.getElementById('stat-total').textContent = scope.length;
             document.getElementById('stat-showing').textContent = filtered.length;
 
             // Render devices
@@ -3876,18 +4194,42 @@
                 list.innerHTML = '<div class="no-devices"><h3>No devices found</h3><p>Try adjusting your search or filter</p></div>';
             } else {
                 list.innerHTML = pageDevices.map(d => {
+                    const offline = d.online === false;
                     const screenInfo = d.screen || '-';  // e.g. "2:3840x1080"
                     const loc = d.location || '-';
                     const rtt = d.rtt || '-';
                     const ver = d.version || '-';
                     const activeWin = d.activeWindow || '';
-                    return '<div class="device-card" onclick="connectDevice(\'' + d.id + '\')">' +
+                    // 操作图标：在线卡片有终端；删除对所有卡片开放（离线=删记录，
-                        '<button class="card-term-btn" title="Open Terminal" aria-label="Terminal" ' +
+                    // 在线=卸载主机），仅管理员可用。Wall 模式不提供删除。
+                    const actions = [];
+                    if (!offline) {
+                        actions.push(
+                            '<button class="card-icon-btn card-term-btn" title="Open Terminal" aria-label="Terminal" ' +
                               'onclick="event.stopPropagation();openTerminal(\'' + d.id + '\')">' +
                               '<svg viewBox="0 0 24 24" width="18" height="18" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">' +
                                 '<polyline points="4 17 10 11 4 5"/><line x1="12" y1="19" x2="20" y2="19"/>' +
                               '</svg>' +
-                        '</button>' +
+                            '</button>');
+                    }
+                    if (canDeleteDevices()) {
+                        actions.push(
+                            '<button class="card-icon-btn card-del-btn" title="' +
+                              (offline ? 'Delete record' : 'Uninstall host') + '" aria-label="Delete" ' +
+                              'onclick="event.stopPropagation();askDeleteDevice(\'' + d.id + '\')">' +
+                              '<svg viewBox="0 0 24 24" width="18" height="18" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">' +
+                                '<polyline points="3 6 5 6 21 6"/>' +
+                                '<path d="M19 6l-1 14a2 2 0 0 1-2 2H8a2 2 0 0 1-2-2L5 6"/>' +
+                                '<path d="M10 11v6"/><path d="M14 11v6"/>' +
+                                '<path d="M9 6V4a1 1 0 0 1 1-1h4a1 1 0 0 1 1 1v2"/>' +
+                              '</svg>' +
+                            '</button>');
+                    }
+                    const actionsHtml = actions.length
+                        ? '<div class="card-actions">' + actions.join('') + '</div>' : '';
+                    return '<div class="device-card' + (offline ? ' offline' : '') + '"' +
+                        (offline ? '' : ' onclick="connectDevice(\'' + d.id + '\')"') + '>' +
+                        actionsHtml +
                         '<h3>' + escapeHtml(displayName(d)) + '</h3>' +
                         '<div class="info-row">' +
                             '<div class="info"><span class="info-label">IP:</span> ' + escapeHtml(d.ip || '-') + '</div>' +
@@ -3895,11 +4237,14 @@
                         '</div>' +
                         '<div class="info"><span class="info-label">OS:</span> ' + escapeHtml(d.os || '-') + '</div>' +
                         '<div class="meta-row">' +
-                            '<span class="meta-item rtt ' + getRttClass(rtt) + '">RTT: ' + escapeHtml(rtt) + '</span>' +
+                            (offline
+                                ? '<span class="meta-item offline-badge">Offline</span>'
+                                : '<span class="meta-item rtt ' + getRttClass(rtt) + '">RTT: ' + escapeHtml(rtt) + '</span>') +
                             '<span class="meta-item">Ver: ' + escapeHtml(ver) + '</span>' +
                             '<span class="meta-item">' + screenInfo + '</span>' +
                         '</div>' +
-                        (activeWin ? '<div class="active-window' + (isWindowBusy(activeWin) ? ' busy' : '') + '" title="' + escapeHtml(activeWin) + '">' + escapeHtml(activeWin) + '</div>' : '') +
+                        (offline ? '<div class="last-seen">Last seen: ' + escapeHtml(formatLastSeen(d.last_seen)) + '</div>' : '') +
+                        (!offline && activeWin ? '<div class="active-window' + (isWindowBusy(activeWin) ? ' busy' : '') + '" title="' + escapeHtml(activeWin) + '">' + escapeHtml(activeWin) + '</div>' : '') +
                     '</div>';
                 }).join('');
             }
@@ -4035,11 +4380,55 @@
             challengeNonce = '';
             connectWebSocket();  // Reconnect immediately
             token = null;
+            currentUserRole = 'viewer';
             localStorage.removeItem('token');
+            localStorage.removeItem('role');
             devices = [];
             showPage('login-page');
-            // Hide users button
+            // Hide admin-only buttons
-            document.getElementById('users-btn').classList.remove('visible');
+            updateAdminButtons();
+        }
+
+        // ===== 删除设备 =====
+        // 两种情况都删除服务端 devices.json 中的历史记录；在线设备额外按 MFC
+        // 的做法发送单字节 TOKEN_UNINSTALL（卸载主机）。都先弹二次确认。
+        // 仅管理员可见/可用。
+        let pendingDeleteDeviceId = null;
+
+        function canDeleteDevices() {
+            return currentUserRole === 'admin';
+        }
+
+        function askDeleteDevice(id) {
+            if (!canDeleteDevices()) return;
+            const d = devices.find(x => String(x.id) === String(id));
+            if (!d) { alert('Device not found'); return; }
+            const offline = d.online === false;
+            const name = displayName(d);
+            pendingDeleteDeviceId = String(id);
+            document.getElementById('delete-device-title').textContent =
+                offline ? 'Delete Device Record' : 'Uninstall Host';
+            document.getElementById('delete-device-msg').innerHTML = offline
+                ? 'Remove <strong>' + escapeHtml(name) + '</strong> from the server\'s device history?' +
+                  '<br>This cannot be undone.'
+                : 'Send the uninstall command to <strong>' + escapeHtml(name) + '</strong>?' +
+                  '<br>The remote agent will uninstall itself, disconnect, and its record will be deleted.';
+            document.getElementById('delete-device-confirm').textContent =
+                offline ? 'Delete' : 'Uninstall';
+            document.getElementById('delete-device-modal').classList.add('active');
+        }
+
+        function cancelDeleteDevice() {
+            pendingDeleteDeviceId = null;
+            document.getElementById('delete-device-modal').classList.remove('active');
+        }
+
+        function confirmDeleteDevice() {
+            const id = pendingDeleteDeviceId;
+            document.getElementById('delete-device-modal').classList.remove('active');
+            pendingDeleteDeviceId = null;
+            if (!id || !ws || ws.readyState !== WebSocket.OPEN) return;
+            ws.send(JSON.stringify({ cmd: 'delete_device', token, id }));
         }
 
         // User Management Functions
@@ -4122,6 +4511,181 @@
             }
         }
 
+        // ===== Audit Log (admin only) =====
+        // Server-side handler: query_audit -> audit_result (see web/audit_query.go).
+        // Records are newest-first and already redacted at write time.
+        const AUDIT_EVENTS = [
+            'web.ws.connect', 'web.ws.reject', 'web.ws.close',
+            'web.login.success', 'web.login.failure', 'web.login.throttled',
+            'web.session.resume', 'web.auth.invalid_token', 'web.authz.denied',
+            'web.command.unknown', 'web.salt.unknown_user',
+            'remote.screen.start', 'remote.screen.stop', 'remote.screen.denied',
+            'remote.terminal.start', 'remote.terminal.stop', 'remote.terminal.denied',
+            'remote.clipboard.set', 'remote.clipboard.get', 'remote.rdp_reset',
+            'admin.user.create', 'admin.user.delete', 'admin.device.delete', 'admin.audit.query',
+            'device.online', 'device.offline',
+            'device.auth.success', 'device.auth.failure', 'device.auth.throttled',
+            'device.auth.heartbeat.success',
+            'device.connauth.rejected', 'device.subconn.foreign_ip'
+        ];
+        let auditState = { offset: 0, limit: 100, total: 0, loaded: false };
+
+        // Show the admin-only toolbar buttons (Users / Audit Log). Called after
+        // login, SSO restore, logout and capability negotiation. The audit
+        // button also requires the server capability (auditLog); servers that
+        // do not implement query_audit simply never advertise it.
+        function updateAdminButtons() {
+            const admin = currentUserRole === 'admin';
+            const usersBtn = document.getElementById('users-btn');
+            if (usersBtn) usersBtn.classList.toggle('visible', admin);
+            const auditBtn = document.getElementById('audit-btn');
+            if (auditBtn) auditBtn.classList.toggle('visible', admin && !!serverCaps.auditLog);
+        }
+
+        function openAuditPage() {
+            if (currentUserRole !== 'admin' || !serverCaps.auditLog) return;
+            fillAuditEventOptions();
+            showPage('audit-page');
+            queryAudit(0);
+        }
+
+        function fillAuditEventOptions() {
+            const dl = document.getElementById('audit-event-options');
+            if (!dl || dl.children.length > 0) return;
+            dl.innerHTML = AUDIT_EVENTS.map(e => '<option value="' + e + '"></option>').join('');
+        }
+
+        // datetime-local values are in the browser's local zone; the server
+        // compares against RFC3339 audit timestamps, so convert explicitly.
+        function isoFromLocalInput(id) {
+            const v = document.getElementById(id).value;
+            if (!v) return '';
+            const d = new Date(v);
+            return isNaN(d.getTime()) ? '' : d.toISOString();
+        }
+
+        function queryAudit(offset) {
+            if (!ws || ws.readyState !== WebSocket.OPEN || !token) return;
+            if (currentUserRole !== 'admin') return;
+            const payload = {
+                cmd: 'query_audit',
+                token,
+                limit: parseInt(document.getElementById('audit-limit').value, 10) || 100,
+                offset: Math.max(0, offset | 0),
+                event: document.getElementById('audit-event').value.trim(),
+                actor: document.getElementById('audit-actor').value.trim(),
+                ip: document.getElementById('audit-ip').value.trim(),
+                device_id: document.getElementById('audit-device').value.trim(),
+                keyword: document.getElementById('audit-keyword').value.trim(),
+                warn_only: document.getElementById('audit-warn-only').checked
+            };
+            const from = isoFromLocalInput('audit-from');
+            if (from) payload.from = from;
+            const to = isoFromLocalInput('audit-to');
+            if (to) payload.to = to;
+            setAuditStatus('Querying...', false);
+            ws.send(JSON.stringify(payload));
+        }
+
+        function resetAuditFilters() {
+            ['audit-from', 'audit-to', 'audit-event', 'audit-actor', 'audit-ip', 'audit-device', 'audit-keyword']
+                .forEach(id => { document.getElementById(id).value = ''; });
+            document.getElementById('audit-warn-only').checked = false;
+            queryAudit(0);
+        }
+
+        function setAuditStatus(text, warn) {
+            const el = document.getElementById('audit-status');
+            el.textContent = text || '';
+            el.className = 'audit-status' + (warn ? ' warn' : '');
+        }
+
+        function handleAuditResult(msg) {
+            if (!msg.ok) {
+                setAuditStatus(msg.msg || 'Query failed', true);
+                return;
+            }
+            auditState.total = msg.total || 0;
+            auditState.offset = msg.offset || 0;
+            auditState.limit = msg.limit || auditState.limit;
+            auditState.loaded = true;
+
+            renderAuditRows(msg.events || []);
+            renderAuditPagination();
+
+            const parts = [];
+            if (!msg.file_exists) {
+                parts.push('No audit file yet — no security events have been recorded.');
+            } else {
+                parts.push(auditState.total + ' matching record(s)');
+                const shown = (msg.events || []).length;
+                if (shown !== auditState.total) parts.push('showing ' + shown);
+                if (msg.file) parts.push('file: ' + msg.file);
+            }
+            if (msg.truncated) {
+                parts.push('only the newest ' +
+                    Math.round((msg.scanned_bytes || 0) / 1048576) + ' MB of the file was scanned');
+            }
+            setAuditStatus(parts.join(' · '), !!msg.truncated);
+        }
+
+        function formatAuditTime(s) {
+            if (!s) return '';
+            const d = new Date(s);
+            return isNaN(d.getTime()) ? escapeHtml(s) : d.toLocaleString();
+        }
+
+        const AUDIT_STD_FIELDS = new Set(['time', 'level', 'event', 'actor', 'role', 'ip', 'device_id', 'audit', 'message', 'module']);
+        function formatAuditDetails(rec) {
+            return Object.keys(rec)
+                .filter(k => !AUDIT_STD_FIELDS.has(k))
+                .sort()
+                .map(k => {
+                    let v = rec[k];
+                    if (v !== null && typeof v === 'object') v = JSON.stringify(v);
+                    return escapeHtml(k) + '=' + escapeHtml(String(v));
+                })
+                .join('  ');
+        }
+
+        function renderAuditRows(events) {
+            document.getElementById('audit-count').textContent = auditState.total;
+            const tbody = document.getElementById('audit-rows');
+            if (!events.length) {
+                tbody.innerHTML = '<tr><td colspan="8" class="audit-empty">No audit records match the filters</td></tr>';
+                return;
+            }
+            tbody.innerHTML = events.map(rec => {
+                const level = rec.level === 'warn' ? 'warn' : 'info';
+                return '<tr>' +
+                    '<td title="' + escapeHtml(rec.time || '') + '">' + formatAuditTime(rec.time) + '</td>' +
+                    '<td><span class="audit-level ' + level + '">' + level + '</span></td>' +
+                    '<td>' + escapeHtml(rec.event || '') + '</td>' +
+                    '<td>' + escapeHtml(rec.actor || '') + '</td>' +
+                    '<td>' + escapeHtml(rec.role || '') + '</td>' +
+                    '<td>' + escapeHtml(rec.ip || '') + '</td>' +
+                    '<td>' + escapeHtml(rec.device_id || '') + '</td>' +
+                    '<td class="audit-details">' + formatAuditDetails(rec) + '</td>' +
+                    '</tr>';
+            }).join('');
+        }
+
+        function renderAuditPagination() {
+            const container = document.getElementById('audit-pagination');
+            if (auditState.total <= auditState.limit) {
+                container.innerHTML = '';
+                return;
+            }
+            const page = Math.floor(auditState.offset / auditState.limit) + 1;
+            const pages = Math.ceil(auditState.total / auditState.limit);
+            const prev = Math.max(0, auditState.offset - auditState.limit);
+            const next = auditState.offset + auditState.limit;
+            container.innerHTML =
+                '<button onclick="queryAudit(' + prev + ')" ' + (page <= 1 ? 'disabled' : '') + '>Prev</button>' +
+                '<span class="page-info">Page ' + page + ' of ' + pages + '</span>' +
+                '<button onclick="queryAudit(' + next + ')" ' + (page >= pages ? 'disabled' : '') + '>Next</button>';
+        }
+
         function renderUsersList(users) {
             const container = document.getElementById('users-list');
             if (!users || users.length === 0) {
@@ -6191,10 +6755,9 @@
             // (not logged in, or SSO disabled) fall back to the restored
             // session or the built-in login form.
             trySSO().then(() => {
-                // Show Users button for admin only (final role known after SSO).
+                // Show admin-only buttons once the final role is known (SSO or local login).
-                if (token && currentUserRole === 'admin') {
+                if (!token) currentUserRole = 'viewer';
-                    document.getElementById('users-btn').classList.add('visible');
+                updateAdminButtons();
-                }
                 connectWebSocket();
             });
         };