diff --git a/CMakeLists.txt b/CMakeLists.txt
index 874aaaa8..8c29c49d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -50,6 +50,7 @@ add_custom_target(
 set(SOURCES
     ${CMAKE_CURRENT_SOURCE_DIR}/src/Revision.cc
     src/Account.cc
+    src/AccountSync.cc
     src/AddressTranslator.cc
     src/AFSArchive.cc
     src/AsyncHTTPServer.cc
diff --git a/src/Account.cc b/src/Account.cc
index 7df886a8..a3fc939c 100644
--- a/src/Account.cc
+++ b/src/Account.cc
@@ -9,6 +9,7 @@
 #include <phosg/Time.hh>
 
 #include "Account.hh"
+#include "AccountSync.hh"
 
 std::shared_ptr<DCNTELicense> DCNTELicense::from_json(const phosg::JSON& json) {
   auto ret = std::make_shared<DCNTELicense>();
@@ -400,6 +401,8 @@ void Account::save() const {
         phosg::JSON::SerializeOption::FORMAT | phosg::JSON::SerializeOption::HEX_INTEGERS);
     std::string filename = std::format("system/licenses/{:010}.json", this->account_id);
     phosg::save_file(filename, json_data);
+
+    AccountSync::notify_account_saved(this->account_id, filename);
   }
 }
 
diff --git a/src/AccountSync.cc b/src/AccountSync.cc
new file mode 100644
index 00000000..a6680947
--- /dev/null
+++ b/src/AccountSync.cc
@@ -0,0 +1,298 @@
+#include "AccountSync.hh"
+
+#include <chrono>
+#include <cstdio>
+#include <filesystem>
+#include <format>
+#include <fstream>
+#include <mutex>
+#include <stdexcept>
+#include <string>
+
+namespace AccountSync {
+
+static std::mutex config_mutex;
+static std::mutex spool_mutex;
+static Config current_config;
+
+static uint64_t now_usecs() {
+  using namespace std::chrono;
+  return duration_cast<microseconds>(system_clock::now().time_since_epoch()).count();
+}
+
+static Config get_config() {
+  std::lock_guard<std::mutex> g(config_mutex);
+  return current_config;
+}
+
+static std::string source_label(const Config& cfg) {
+  if (!cfg.source.empty()) {
+    return cfg.source;
+  }
+  if (!cfg.source_region.empty() && !cfg.source_ship.empty()) {
+    return cfg.source_region + "-" + cfg.source_ship;
+  }
+  if (!cfg.source_region.empty()) {
+    return cfg.source_region;
+  }
+  if (!cfg.source_ship.empty()) {
+    return cfg.source_ship;
+  }
+  return "unknown";
+}
+
+static std::string json_escape(const std::string& s) {
+  std::string ret;
+  ret.reserve(s.size() + 8);
+  for (unsigned char ch : s) {
+    switch (ch) {
+      case '\\':
+        ret += "\\\\";
+        break;
+      case '"':
+        ret += "\\\"";
+        break;
+      case '\b':
+        ret += "\\b";
+        break;
+      case '\f':
+        ret += "\\f";
+        break;
+      case '\n':
+        ret += "\\n";
+        break;
+      case '\r':
+        ret += "\\r";
+        break;
+      case '\t':
+        ret += "\\t";
+        break;
+      default:
+        if (ch < 0x20) {
+          char buf[8];
+          std::snprintf(buf, sizeof(buf), "\\u%04X", ch);
+          ret += buf;
+        } else {
+          ret += static_cast<char>(ch);
+        }
+    }
+  }
+  return ret;
+}
+
+static void append_spool_line(const Config& cfg, const std::string& line) {
+  if (cfg.spool_directory.empty()) {
+    return;
+  }
+
+  try {
+    std::lock_guard<std::mutex> g(spool_mutex);
+    std::filesystem::create_directories(cfg.spool_directory);
+    std::filesystem::path path = std::filesystem::path(cfg.spool_directory) / "events.jsonl";
+
+    std::ofstream f(path, std::ios::app);
+    if (!f) {
+      throw std::runtime_error("failed to open spool file");
+    }
+    f << line << '\n';
+
+  } catch (const std::exception& e) {
+    std::fprintf(stderr,
+        "[AccountSync] warning failed_to_write_spool directory=%s error=%s\n",
+        cfg.spool_directory.c_str(),
+        e.what());
+  }
+}
+
+static std::string base_event_json(const Config& cfg, const char* event, uint32_t account_id) {
+  return std::format(
+      "{{\"timestamp_usecs\":{},\"producer\":\"newserv\",\"source\":\"{}\",\"source_region\":\"{}\",\"source_ship\":\"{}\",\"account_store\":\"{}\",\"event\":\"{}\",\"account_id\":{},\"account_id_str\":\"{:010}\"",
+      now_usecs(),
+      json_escape(source_label(cfg)),
+      json_escape(cfg.source_region),
+      json_escape(cfg.source_ship),
+      json_escape(cfg.account_store),
+      json_escape(event),
+      static_cast<unsigned int>(account_id),
+      static_cast<unsigned int>(account_id));
+}
+
+void configure(const Config& cfg) {
+  {
+    std::lock_guard<std::mutex> g(config_mutex);
+    current_config = cfg;
+  }
+
+  if (cfg.enabled) {
+    std::fprintf(stderr,
+        "[AccountSync] config enabled source=%s source_region=%s source_ship=%s account_store=%s coordinator_url=%s notify_bb_sessions=%s spool_directory=%s login_locks=%s\n",
+        source_label(cfg).c_str(),
+        cfg.source_region.c_str(),
+        cfg.source_ship.c_str(),
+        cfg.account_store.c_str(),
+        cfg.coordinator_url.c_str(),
+        cfg.notify_bb_sessions ? "true" : "false",
+        cfg.spool_directory.c_str(),
+        cfg.enable_login_locks ? "true" : "false");
+  }
+}
+
+void configure_from_json(const phosg::JSON& json) {
+  Config cfg;
+  cfg.enabled = json.get_bool("Enabled", false);
+
+  const std::string legacy_region = json.get_string("Region", "");
+  cfg.source = json.get_string("Source", legacy_region);
+  cfg.source_region = json.get_string("SourceRegion", "");
+  cfg.source_ship = json.get_string("SourceShip", "");
+  cfg.account_store = json.get_string("AccountStore", "shared");
+
+  if (cfg.source_region.empty() && cfg.source_ship.empty() && !legacy_region.empty()) {
+    size_t dash_offset = legacy_region.find('-');
+    if (dash_offset != std::string::npos) {
+      cfg.source_region = legacy_region.substr(0, dash_offset);
+      cfg.source_ship = legacy_region.substr(dash_offset + 1);
+    } else {
+      cfg.source_region = legacy_region;
+    }
+  }
+
+  cfg.coordinator_url = json.get_string("CoordinatorURL", "");
+  cfg.shared_secret = json.get_string("SharedSecret", "");
+  cfg.request_timeout_usecs = json.get_int("RequestTimeoutUsecs", 3000000);
+  cfg.fail_open = json.get_bool("FailOpen", false);
+  cfg.notify_account_saves = json.get_bool("NotifyAccountSaves", true);
+  cfg.notify_player_saves = json.get_bool("NotifyPlayerSaves", true);
+  cfg.notify_backup_saves = json.get_bool("NotifyBackupSaves", true);
+  cfg.enable_login_locks = json.get_bool("EnableLoginLocks", false);
+  cfg.notify_bb_sessions = json.get_bool("NotifyBBSessions", cfg.enable_login_locks);
+  cfg.spool_directory = json.get_string("SpoolDirectory", "system/account-sync-spool");
+  configure(cfg);
+}
+
+void notify_account_saved(uint32_t account_id, const std::string& filename) {
+  auto cfg = get_config();
+  if (!cfg.enabled || !cfg.notify_account_saves) {
+    return;
+  }
+
+  std::fprintf(stderr,
+      "[AccountSync] event=account_saved source=%s source_region=%s source_ship=%s account_store=%s account_id=%010u filename=%s\n",
+      source_label(cfg).c_str(),
+      cfg.source_region.c_str(),
+      cfg.source_ship.c_str(),
+      cfg.account_store.c_str(),
+      static_cast<unsigned int>(account_id),
+      filename.c_str());
+
+  auto line = base_event_json(cfg, "account_saved", account_id) +
+      std::format(",\"filename\":\"{}\"}}", json_escape(filename));
+  append_spool_line(cfg, line);
+}
+
+void notify_backup_saved(uint32_t account_id, size_t slot, const std::string& filename) {
+  auto cfg = get_config();
+  if (!cfg.enabled || !cfg.notify_backup_saves) {
+    return;
+  }
+
+  std::fprintf(stderr,
+      "[AccountSync] event=backup_saved source=%s source_region=%s source_ship=%s account_store=%s account_id=%010u slot=%zu filename=%s\n",
+      source_label(cfg).c_str(),
+      cfg.source_region.c_str(),
+      cfg.source_ship.c_str(),
+      cfg.account_store.c_str(),
+      static_cast<unsigned int>(account_id),
+      slot,
+      filename.c_str());
+
+  auto line = base_event_json(cfg, "backup_saved", account_id) +
+      std::format(",\"slot\":{},\"filename\":\"{}\"}}", slot, json_escape(filename));
+  append_spool_line(cfg, line);
+}
+
+void notify_player_state_saved(
+    const char* reason,
+    uint32_t account_id,
+    const std::string& bb_username,
+    const std::string& filename) {
+  auto cfg = get_config();
+  if (!cfg.enabled || !cfg.notify_player_saves) {
+    return;
+  }
+
+  std::fprintf(stderr,
+      "[AccountSync] event=player_state_saved source=%s source_region=%s source_ship=%s account_store=%s reason=%s account_id=%010u bb_username=%s filename=%s\n",
+      source_label(cfg).c_str(),
+      cfg.source_region.c_str(),
+      cfg.source_ship.c_str(),
+      cfg.account_store.c_str(),
+      reason,
+      static_cast<unsigned int>(account_id),
+      bb_username.c_str(),
+      filename.c_str());
+
+  auto line = base_event_json(cfg, "player_state_saved", account_id) +
+      std::format(",\"reason\":\"{}\",\"bb_username\":\"{}\",\"filename\":\"{}\"}}",
+          json_escape(reason),
+          json_escape(bb_username),
+          json_escape(filename));
+  append_spool_line(cfg, line);
+}
+
+void notify_bb_login_start(
+    uint32_t account_id,
+    const std::string& bb_username,
+    int64_t character_slot,
+    uint8_t connection_phase) {
+  auto cfg = get_config();
+  if (!cfg.enabled || !cfg.notify_bb_sessions) {
+    return;
+  }
+
+  std::fprintf(stderr,
+      "[AccountSync] event=bb_login_start source=%s source_region=%s source_ship=%s account_store=%s account_id=%010u bb_username=%s character_slot=%lld connection_phase=%u\n",
+      source_label(cfg).c_str(),
+      cfg.source_region.c_str(),
+      cfg.source_ship.c_str(),
+      cfg.account_store.c_str(),
+      static_cast<unsigned int>(account_id),
+      bb_username.c_str(),
+      static_cast<long long>(character_slot),
+      static_cast<unsigned int>(connection_phase));
+
+  auto line = base_event_json(cfg, "bb_login_start", account_id) +
+      std::format(",\"bb_username\":\"{}\",\"character_slot\":{},\"connection_phase\":{}}}",
+          json_escape(bb_username),
+          static_cast<long long>(character_slot),
+          static_cast<unsigned int>(connection_phase));
+  append_spool_line(cfg, line);
+}
+
+void notify_bb_login_end(
+    uint32_t account_id,
+    const std::string& bb_username,
+    int64_t character_slot) {
+  auto cfg = get_config();
+  if (!cfg.enabled || !cfg.notify_bb_sessions) {
+    return;
+  }
+
+  std::fprintf(stderr,
+      "[AccountSync] event=bb_login_end source=%s source_region=%s source_ship=%s account_store=%s account_id=%010u bb_username=%s character_slot=%lld\n",
+      source_label(cfg).c_str(),
+      cfg.source_region.c_str(),
+      cfg.source_ship.c_str(),
+      cfg.account_store.c_str(),
+      static_cast<unsigned int>(account_id),
+      bb_username.c_str(),
+      static_cast<long long>(character_slot));
+
+  auto line = base_event_json(cfg, "bb_login_end", account_id) +
+      std::format(",\"bb_username\":\"{}\",\"character_slot\":{}}}",
+          json_escape(bb_username),
+          static_cast<long long>(character_slot));
+  append_spool_line(cfg, line);
+}
+
+} // namespace AccountSync
diff --git a/src/AccountSync.hh b/src/AccountSync.hh
new file mode 100644
index 00000000..cbfeb78d
--- /dev/null
+++ b/src/AccountSync.hh
@@ -0,0 +1,56 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+
+#include <phosg/JSON.hh>
+
+namespace AccountSync {
+
+struct Config {
+  bool enabled = false;
+
+  // Source identity. Region is no longer enough because account JSON is shared
+  // across live/test/hardcore in a region.
+  std::string source;
+  std::string source_region;
+  std::string source_ship;
+  std::string account_store = "shared";
+
+  std::string coordinator_url;
+  std::string shared_secret;
+  uint64_t request_timeout_usecs = 3000000;
+  bool fail_open = false;
+  bool notify_account_saves = true;
+  bool notify_player_saves = true;
+  bool notify_backup_saves = true;
+  bool notify_bb_sessions = false;
+  bool enable_login_locks = false; // Reserved for future blocking lock behavior
+  std::string spool_directory = "system/account-sync-spool";
+};
+
+void configure(const Config& cfg);
+void configure_from_json(const phosg::JSON& json);
+
+void notify_account_saved(uint32_t account_id, const std::string& filename);
+void notify_backup_saved(uint32_t account_id, size_t slot, const std::string& filename);
+
+void notify_player_state_saved(
+    const char* reason,
+    uint32_t account_id,
+    const std::string& bb_username,
+    const std::string& filename);
+
+void notify_bb_login_start(
+    uint32_t account_id,
+    const std::string& bb_username,
+    int64_t character_slot,
+    uint8_t connection_phase);
+
+void notify_bb_login_end(
+    uint32_t account_id,
+    const std::string& bb_username,
+    int64_t character_slot);
+
+} // namespace AccountSync
diff --git a/src/ChatCommands.cc b/src/ChatCommands.cc
index 2a911c20..7ca6f917 100644
--- a/src/ChatCommands.cc
+++ b/src/ChatCommands.cc
@@ -22,6 +22,7 @@
 #include "Server.hh"
 #include "StaticGameData.hh"
 #include "Text.hh"
+#include "AccountSync.hh"
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 // Tools
@@ -491,12 +492,22 @@ static asio::awaitable<void> server_command_bbchar_savechar(const Args& a, bool
       ? Client::character_filename(dest_bb_license->username, dest_character_index)
       : Client::backup_character_filename(dest_account->account_id, dest_character_index, is_ep3(a.c->version()));
 
+  auto log_account_sync_backup_saved = [&]() -> void {
+    if (!is_bb_conversion) {
+      AccountSync::notify_backup_saved(
+          dest_account->account_id,
+          dest_character_index,
+          filename);
+    }
+  };
+
   if (ch.is_full_info) {
     // Client sent 30; ch contains the verbatim save file from the client
     if (ch.ep3_character) {
       try {
         Client::save_ep3_character_file(filename, *ch.ep3_character);
         send_text_message(a.c, "$C7Character data saved\n(full save file)");
+        log_account_sync_backup_saved();
       } catch (const std::exception& e) {
         send_text_message_fmt(a.c, "$C6Character data could\nnot be saved:\n{}", e.what());
       }
@@ -505,6 +516,7 @@ static asio::awaitable<void> server_command_bbchar_savechar(const Args& a, bool
       try {
         Client::save_character_file(filename, a.c->system_file(), ch.character);
         send_text_message(a.c, "$C7Character data saved\n(full save file)");
+        log_account_sync_backup_saved();
       } catch (const std::exception& e) {
         send_text_message_fmt(a.c, "$C6Character data could\nnot be saved:\n{}", e.what());
       }
@@ -546,6 +558,7 @@ static asio::awaitable<void> server_command_bbchar_savechar(const Args& a, bool
       try {
         Client::save_character_file(filename, a.c->system_file(), bb_player);
         send_text_message(a.c, "$C7Character data saved\n(basic only)");
+        log_account_sync_backup_saved();
       } catch (const std::exception& e) {
         send_text_message_fmt(a.c, "$C6Character data could\nnot be saved:\n{}", e.what());
       }
diff --git a/src/Client.cc b/src/Client.cc
index a27c682c..fad4c7c7 100644
--- a/src/Client.cc
+++ b/src/Client.cc
@@ -15,6 +15,7 @@
 #include "SendCommands.hh"
 #include "Server.hh"
 #include "Version.hh"
+#include "AccountSync.hh"
 
 const uint64_t CLIENT_CONFIG_MAGIC = 0x8399AC32;
 
@@ -232,6 +233,13 @@ Client::~Client() {
 
   if ((this->version() == Version::BB_V4) && (this->character_data.get())) {
     this->save_all();
+
+    if (this->login && this->login->account && this->login->bb_license) {
+      AccountSync::notify_bb_login_end(
+          this->login->account->account_id,
+          this->login->bb_license->username,
+          this->bb_character_index);
+    }
   }
   this->log.info_f("Deleted");
 }
@@ -503,6 +511,13 @@ void Client::save_system_file() const {
   std::string filename = this->system_filename();
   phosg::save_object_file(filename, *this->system_data);
   this->log.info_f("Saved system file {}", filename);
+  if (this->login && this->login->account && this->login->bb_license) {
+    AccountSync::notify_player_state_saved(
+        "system_saved",
+        this->login->account->account_id,
+        this->login->bb_license->username,
+        filename);
+  }
 }
 
 // Guild Card file
@@ -542,6 +557,13 @@ void Client::save_guild_card_file() const {
   std::string filename = this->guild_card_filename();
   phosg::save_object_file(filename, *this->guild_card_data);
   this->log.info_f("Saved Guild Card file {}", filename);
+  if (this->login && this->login->account && this->login->bb_license) {
+    AccountSync::notify_player_state_saved(
+        "guild_card_saved",
+        this->login->account->account_id,
+        this->login->bb_license->username,
+        filename);
+  }
 }
 
 // Character file
@@ -634,6 +656,13 @@ void Client::save_character_file() {
   auto filename = this->character_filename();
   this->save_character_file(filename, this->system_data, this->character_data);
   this->log.info_f("Saved character file {}", filename);
+  if (this->login && this->login->account && this->login->bb_license) {
+    AccountSync::notify_player_state_saved(
+        "character_saved",
+        this->login->account->account_id,
+        this->login->bb_license->username,
+        filename);
+  }
 }
 
 void Client::create_character_file(
@@ -834,6 +863,13 @@ void Client::save_bank_file() const {
   auto filename = this->bank_filename();
   this->save_bank_file(filename, *this->bank_data);
   this->log.info_f("Saved bank file {}", filename);
+  if (this->login && this->login->account && this->login->bb_license) {
+    AccountSync::notify_player_state_saved(
+        "bank_saved",
+        this->login->account->account_id,
+        this->login->bb_license->username,
+        filename);
+  }
 }
 
 void Client::change_bank(ssize_t index) {
diff --git a/src/ReceiveCommands.cc b/src/ReceiveCommands.cc
index 79aeeb8e..acf99d35 100644
--- a/src/ReceiveCommands.cc
+++ b/src/ReceiveCommands.cc
@@ -27,6 +27,7 @@
 #include "StaticGameData.hh"
 #include "Text.hh"
 #include "BrutalPeeps.hh"
+#include "AccountSync.hh"
 
 const char* BATTLE_TABLE_DISCONNECT_HOOK_NAME = "battle_table_state";
 const char* QUEST_BARRIER_DISCONNECT_HOOK_NAME = "quest_barrier";
@@ -1672,6 +1673,14 @@ static asio::awaitable<void> on_93_BB(std::shared_ptr<Client> c, Channel::Messag
     co_return;
   }
 
+  if (c->login->account && c->login->bb_license) {
+    AccountSync::notify_bb_login_start(
+        c->login->account->account_id,
+        c->login->bb_license->username,
+        c->bb_character_index,
+        c->bb_connection_phase);
+  }
+
   std::string version_string = c->bb_client_config.as_string();
   phosg::strip_trailing_zeroes(version_string);
   // If the version std::string starts with "Ver.", assume it's Sega and apply the normal version encoding logic. Otherwise,
diff --git a/src/ServerState.cc b/src/ServerState.cc
index c56f3477..0384ede7 100644
--- a/src/ServerState.cc
+++ b/src/ServerState.cc
@@ -18,6 +18,7 @@
 #include "SendCommands.hh"
 #include "Text.hh"
 #include "TextIndex.hh"
+#include "AccountSync.hh"
 
 #ifdef PHOSG_WINDOWS
 static constexpr bool IS_WINDOWS = true;
@@ -879,6 +880,7 @@ void ServerState::load_config_early() {
   this->client_ping_interval_usecs = this->config_json->get_int("ClientPingInterval", 30000000);
   this->client_idle_timeout_usecs = this->config_json->get_int("ClientIdleTimeout", 60000000);
   this->patch_client_idle_timeout_usecs = this->config_json->get_int("PatchClientIdleTimeout", 300000000);
+  AccountSync::configure_from_json(this->config_json->get("AccountSync", phosg::JSON::dict()));
   this->psopeeps_dcv2_exp_multiplier = this->config_json->get_int("PsoPeepsDCV2EXPMultiplier", 5);
   if ((this->psopeeps_dcv2_exp_multiplier != 5) && (this->psopeeps_dcv2_exp_multiplier != 10)) {
     throw std::runtime_error("PsoPeepsDCV2EXPMultiplier must be 5 or 10");