diff --git a/tools/cabana/streams/replaystream.cc b/tools/cabana/streams/replaystream.cc
index 18b0317d46..ac137434d3 100644
--- a/tools/cabana/streams/replaystream.cc
+++ b/tools/cabana/streams/replaystream.cc
@@ -53,6 +53,10 @@ bool ReplayStream::loadRoute(const QString &route, const QString &data_dir, uint
                           {}, nullptr, replay_flags, data_dir.toStdString(), this));
   replay->setSegmentCacheLimit(settings.max_cached_minutes);
   replay->installEventFilter(event_filter, this);
+
+  // Forward replay callbacks to corresponding Qt signals.
+  replay->onQLogLoaded = [this](std::shared_ptr<LogReader> qlog) { emit qLogLoaded(qlog); };
+
   QObject::connect(replay.get(), &Replay::seeking, this, &AbstractStream::seeking);
   QObject::connect(replay.get(), &Replay::seekedTo, this, &AbstractStream::seekedTo);
   QObject::connect(replay.get(), &Replay::segmentsMerged, this, &ReplayStream::mergeSegments);
diff --git a/tools/cabana/streams/replaystream.h b/tools/cabana/streams/replaystream.h
index 2a9f343645..1d1cdaec9e 100644
--- a/tools/cabana/streams/replaystream.h
+++ b/tools/cabana/streams/replaystream.h
@@ -10,6 +10,8 @@
 #include "tools/cabana/streams/abstractstream.h"
 #include "tools/replay/replay.h"
 
+Q_DECLARE_METATYPE(std::shared_ptr<LogReader>);
+
 class ReplayStream : public AbstractStream {
   Q_OBJECT
 
@@ -24,7 +26,7 @@ public:
   inline QString carFingerprint() const override { return replay->carFingerprint().c_str(); }
   double minSeconds() const override { return replay->minSeconds(); }
   double maxSeconds() const { return replay->maxSeconds(); }
-  inline QDateTime beginDateTime() const { return replay->routeDateTime(); }
+  inline QDateTime beginDateTime() const { return QDateTime::fromSecsSinceEpoch(replay->routeDateTime()); }
   inline uint64_t beginMonoTime() const override { return replay->routeStartNanos(); }
   inline void setSpeed(float speed) override { replay->setSpeed(speed); }
   inline float getSpeed() const { return replay->getSpeed(); }
@@ -32,6 +34,9 @@ public:
   inline bool isPaused() const override { return replay->isPaused(); }
   void pause(bool pause) override;
 
+signals:
+  void qLogLoaded(std::shared_ptr<LogReader> qlog);
+
 private:
   void mergeSegments();
   std::unique_ptr<Replay> replay = nullptr;
diff --git a/tools/cabana/videowidget.cc b/tools/cabana/videowidget.cc
index 66a6efe569..7f9e3d6960 100644
--- a/tools/cabana/videowidget.cc
+++ b/tools/cabana/videowidget.cc
@@ -13,8 +13,6 @@
 #include <QVBoxLayout>
 #include <QtConcurrent>
 
-#include "tools/cabana/streams/replaystream.h"
-
 const int MIN_VIDEO_HEIGHT = 100;
 const int THUMBNAIL_MARGIN = 3;
 
@@ -167,10 +165,7 @@ QWidget *VideoWidget::createCameraWidget() {
   QObject::connect(camera_tab, &QTabBar::currentChanged, [this](int index) {
     if (index != -1) cam_widget->setStreamType((VisionStreamType)camera_tab->tabData(index).toInt());
   });
-
-  auto replay = static_cast<ReplayStream*>(can)->getReplay();
-  QObject::connect(replay, &Replay::qLogLoaded, slider, &Slider::parseQLog, Qt::QueuedConnection);
-  QObject::connect(replay, &Replay::minMaxTimeChanged, this, &VideoWidget::timeRangeChanged, Qt::QueuedConnection);
+  QObject::connect(static_cast<ReplayStream*>(can), &ReplayStream::qLogLoaded, slider, &Slider::parseQLog, Qt::QueuedConnection);
   return w;
 }
 
@@ -248,11 +243,8 @@ Slider::Slider(QWidget *parent) : QSlider(Qt::Horizontal, parent) {
   setMouseTracking(true);
 }
 
-AlertInfo Slider::alertInfo(double seconds) {
-  uint64_t mono_time = can->toMonoTime(seconds);
-  auto alert_it = alerts.lower_bound(mono_time);
-  bool has_alert = (alert_it != alerts.end()) && ((alert_it->first - mono_time) <= 1e8);
-  return has_alert ? alert_it->second : AlertInfo{};
+std::optional<Timeline::Entry> Slider::alertInfo(double seconds) {
+  return getReplay()->findAlertAtTime(seconds);
 }
 
 QPixmap Slider::thumbnail(double seconds)  {
@@ -277,14 +269,6 @@ void Slider::parseQLog(std::shared_ptr<LogReader> qlog) {
         std::lock_guard lk(mutex);
         thumbnails[thumb.getTimestampEof()] = scaled;
       }
-    } else if (e.which == cereal::Event::Which::SELFDRIVE_STATE) {
-      capnp::FlatArrayMessageReader reader(e.data);
-      auto cs = reader.getRoot<cereal::Event>().getSelfdriveState();
-      if (cs.getAlertType().size() > 0 && cs.getAlertText1().size() > 0 &&
-          cs.getAlertSize() != cereal::SelfdriveState::AlertSize::NONE) {
-        std::lock_guard lk(mutex);
-        alerts.emplace(e.mono_time, AlertInfo{cs.getAlertStatus(), cs.getAlertText1().cStr(), cs.getAlertText2().cStr()});
-      }
     }
   });
   update();
@@ -306,8 +290,8 @@ void Slider::paintEvent(QPaintEvent *ev) {
 
   auto replay = getReplay();
   if (replay) {
-    for (auto [begin, end, type] : replay->getTimeline()) {
-      fillRange(begin, end, timeline_colors[(int)type]);
+    for (const auto &entry: *replay->getTimeline()) {
+      fillRange(entry.start_time, entry.end_time, timeline_colors[(int)entry.type]);
     }
 
     QColor empty_color = palette().color(QPalette::Window);
@@ -372,7 +356,7 @@ InfoLabel::InfoLabel(QWidget *parent) : QWidget(parent, Qt::WindowStaysOnTopHint
   setVisible(false);
 }
 
-void InfoLabel::showPixmap(const QPoint &pt, const QString &sec, const QPixmap &pm, const AlertInfo &alert) {
+void InfoLabel::showPixmap(const QPoint &pt, const QString &sec, const QPixmap &pm, const std::optional<Timeline::Entry> &alert) {
   second = sec;
   pixmap = pm;
   alert_info = alert;
@@ -381,10 +365,10 @@ void InfoLabel::showPixmap(const QPoint &pt, const QString &sec, const QPixmap &
   update();
 }
 
-void InfoLabel::showAlert(const AlertInfo &alert) {
+void InfoLabel::showAlert(const std::optional<Timeline::Entry> &alert) {
   alert_info = alert;
   pixmap = {};
-  setVisible(!alert_info.text1.isEmpty());
+  setVisible(alert_info.has_value());
   update();
 }
 
@@ -396,18 +380,11 @@ void InfoLabel::paintEvent(QPaintEvent *event) {
     p.drawRect(rect());
     p.drawText(rect().adjusted(0, 0, 0, -THUMBNAIL_MARGIN), second, Qt::AlignHCenter | Qt::AlignBottom);
   }
-  if (alert_info.text1.size() > 0) {
-    QColor color = timeline_colors[(int)TimelineType::AlertInfo];
-    if (alert_info.status == cereal::SelfdriveState::AlertStatus::USER_PROMPT) {
-      color = timeline_colors[(int)TimelineType::AlertWarning];
-    } else if (alert_info.status == cereal::SelfdriveState::AlertStatus::CRITICAL) {
-      color = timeline_colors[(int)TimelineType::AlertCritical];
-    }
+  if (alert_info) {
+    QColor color = timeline_colors[int(alert_info->type)];
     color.setAlphaF(0.5);
-    QString text = alert_info.text1;
-    if (!alert_info.text2.isEmpty()) {
-      text += "\n" + alert_info.text2;
-    }
+    QString text = QString::fromStdString(alert_info->text1);
+    if (!alert_info->text2.empty()) text += "\n" + QString::fromStdString(alert_info->text2);
 
     if (!pixmap.isNull()) {
       QFont font;
diff --git a/tools/cabana/videowidget.h b/tools/cabana/videowidget.h
index 17bec78545..d3342c34d7 100644
--- a/tools/cabana/videowidget.h
+++ b/tools/cabana/videowidget.h
@@ -16,22 +16,17 @@
 #include "selfdrive/ui/qt/widgets/cameraview.h"
 #include "tools/cabana/utils/util.h"
 #include "tools/replay/logreader.h"
-
-struct AlertInfo {
-  cereal::SelfdriveState::AlertStatus status;
-  QString text1;
-  QString text2;
-};
+#include "tools/cabana/streams/replaystream.h"
 
 class InfoLabel : public QWidget {
 public:
   InfoLabel(QWidget *parent);
-  void showPixmap(const QPoint &pt, const QString &sec, const QPixmap &pm, const AlertInfo &alert);
-  void showAlert(const AlertInfo &alert);
+  void showPixmap(const QPoint &pt, const QString &sec, const QPixmap &pm, const std::optional<Timeline::Entry> &alert);
+  void showAlert(const std::optional<Timeline::Entry> &alert);
   void paintEvent(QPaintEvent *event) override;
   QPixmap pixmap;
   QString second;
-  AlertInfo alert_info;
+  std::optional<Timeline::Entry> alert_info;
 };
 
 class Slider : public QSlider {
@@ -42,7 +37,7 @@ public:
   double currentSecond() const { return value() / factor; }
   void setCurrentSecond(double sec) { setValue(sec * factor); }
   void setTimeRange(double min, double max);
-  AlertInfo alertInfo(double sec);
+  std::optional<Timeline::Entry> alertInfo(double sec);
   QPixmap thumbnail(double sec);
   void parseQLog(std::shared_ptr<LogReader> qlog);
 
@@ -55,7 +50,6 @@ private:
   void paintEvent(QPaintEvent *ev) override;
 
   QMap<uint64_t, QPixmap> thumbnails;
-  std::map<uint64_t, AlertInfo> alerts;
   InfoLabel *thumbnail_label;
 };
 
diff --git a/tools/replay/SConscript b/tools/replay/SConscript
index 1f966d4372..179af69d42 100644
--- a/tools/replay/SConscript
+++ b/tools/replay/SConscript
@@ -9,7 +9,8 @@ if arch == "Darwin":
 else:
   base_libs.append('OpenCL')
 
-replay_lib_src = ["replay.cc", "consoleui.cc", "camera.cc", "filereader.cc", "logreader.cc", "framereader.cc", "route.cc", "util.cc"]
+replay_lib_src = ["replay.cc", "consoleui.cc", "camera.cc", "filereader.cc", "logreader.cc", "framereader.cc",
+                  "route.cc", "util.cc", "timeline.cc"]
 replay_lib = qt_env.Library("qt_replay", replay_lib_src, LIBS=base_libs, FRAMEWORKS=base_frameworks)
 Export('replay_lib')
 replay_libs = [replay_lib, 'avutil', 'avcodec', 'avformat', 'bz2', 'zstd', 'curl', 'yuv', 'ncurses'] + base_libs
diff --git a/tools/replay/consoleui.cc b/tools/replay/consoleui.cc
index 42c7238f7a..b5415ac808 100644
--- a/tools/replay/consoleui.cc
+++ b/tools/replay/consoleui.cc
@@ -1,5 +1,6 @@
 #include "tools/replay/consoleui.h"
 
+#include <time.h>
 #include <initializer_list>
 #include <string>
 #include <tuple>
@@ -152,7 +153,6 @@ void ConsoleUI::updateStatus() {
     add_str(win, unit.c_str());
   };
   static const std::pair<const char *, Color> status_text[] = {
-      {"loading...", Color::Red},
       {"playing", Color::Green},
       {"paused...", Color::Yellow},
   };
@@ -161,8 +161,10 @@ void ConsoleUI::updateStatus() {
 
   auto [status_str, status_color] = status_text[status];
   write_item(0, 0, "STATUS:    ", status_str, "      ", false, status_color);
+  auto cur_ts = replay->routeDateTime() + (int)replay->currentSeconds();
+  char *time_string = ctime(&cur_ts);
   std::string current_segment = " - " + std::to_string((int)(replay->currentSeconds() / 60));
-  write_item(0, 25, "TIME:  ", replay->currentDateTime().toString("ddd MMMM dd hh:mm:ss").toStdString(), current_segment, true);
+  write_item(0, 25, "TIME:  ", time_string, current_segment, true);
 
   auto p = sm["liveParameters"].getLiveParameters();
   write_item(1, 0, "STIFFNESS: ", util::string_format("%.2f %%", p.getStiffnessFactor() * 100), "  ");
@@ -247,18 +249,18 @@ void ConsoleUI::updateTimeline() {
   wattroff(win, COLOR_PAIR(Color::Disengaged));
 
   const int total_sec = replay->maxSeconds() - replay->minSeconds();
-  for (auto [begin, end, type] : replay->getTimeline()) {
-    int start_pos = ((begin - replay->minSeconds()) / total_sec) * width;
-    int end_pos = ((end - replay->minSeconds()) / total_sec) * width;
-    if (type == TimelineType::Engaged) {
+  for (const auto &entry : *replay->getTimeline()) {
+    int start_pos = ((entry.start_time - replay->minSeconds()) / total_sec) * width;
+    int end_pos = ((entry.end_time - replay->minSeconds()) / total_sec) * width;
+    if (entry.type == TimelineType::Engaged) {
       mvwchgat(win, 1, start_pos, end_pos - start_pos + 1, A_COLOR, Color::Engaged, NULL);
       mvwchgat(win, 2, start_pos, end_pos - start_pos + 1, A_COLOR, Color::Engaged, NULL);
-    } else if (type == TimelineType::UserFlag) {
+    } else if (entry.type == TimelineType::UserFlag) {
       mvwchgat(win, 3, start_pos, end_pos - start_pos + 1, ACS_S3, Color::Cyan, NULL);
     } else {
       auto color_id = Color::Green;
-      if (type != TimelineType::AlertInfo) {
-        color_id = type == TimelineType::AlertWarning ? Color::Yellow : Color::Red;
+      if (entry.type != TimelineType::AlertInfo) {
+        color_id = entry.type == TimelineType::AlertWarning ? Color::Yellow : Color::Red;
       }
       mvwchgat(win, 3, start_pos, end_pos - start_pos + 1, ACS_S3, color_id, NULL);
     }
diff --git a/tools/replay/replay.cc b/tools/replay/replay.cc
index a0ae90c079..82e231937c 100644
--- a/tools/replay/replay.cc
+++ b/tools/replay/replay.cc
@@ -1,7 +1,5 @@
 #include "tools/replay/replay.h"
 
-#include <QDebug>
-#include <QtConcurrent>
 #include <capnp/dynamic.h>
 #include <csignal>
 #include "cereal/services.h"
@@ -11,6 +9,14 @@
 
 static void interrupt_sleep_handler(int signal) {}
 
+// Helper function to notify events with safety checks
+template <typename Callback, typename... Args>
+void notifyEvent(Callback &callback, Args &&...args) {
+  if (callback) {
+    callback(std::forward<Args>(args)...);
+  }
+}
+
 Replay::Replay(const std::string &route, std::vector<std::string> allow, std::vector<std::string> block, SubMaster *sm_,
                uint32_t flags, const std::string &data_dir, QObject *parent) : sm(sm_), flags_(flags), QObject(parent) {
   // Register signal handler for SIGUSR1
@@ -40,7 +46,7 @@ Replay::Replay(const std::string &route, std::vector<std::string> allow, std::ve
     }
   }
 
-  rInfo("active services: %s", join(active_services, ',').c_str());
+  rInfo("active services: %s", join(active_services, ", ").c_str());
   rInfo("loading route %s", route.c_str());
 
   if (sm == nullptr) {
@@ -68,7 +74,6 @@ void Replay::stop() {
     stream_thread_ = nullptr;
     rInfo("shutdown: done");
   }
-  timeline_future.waitForFinished();
   camera_server_.reset(nullptr);
   segments_.clear();
 }
@@ -151,101 +156,11 @@ void Replay::checkSeekProgress() {
 }
 
 void Replay::seekToFlag(FindFlag flag) {
-  if (auto next = find(flag)) {
+  if (auto next = timeline_.find(currentSeconds(), flag)) {
     seekTo(*next - 2, false);  // seek to 2 seconds before next
   }
 }
 
-void Replay::buildTimeline() {
-  uint64_t engaged_begin = 0;
-  bool engaged = false;
-
-  auto alert_status = cereal::SelfdriveState::AlertStatus::NORMAL;
-  auto alert_size = cereal::SelfdriveState::AlertSize::NONE;
-  uint64_t alert_begin = 0;
-  std::string alert_type;
-
-  const TimelineType timeline_types[] = {
-    [(int)cereal::SelfdriveState::AlertStatus::NORMAL] = TimelineType::AlertInfo,
-    [(int)cereal::SelfdriveState::AlertStatus::USER_PROMPT] = TimelineType::AlertWarning,
-    [(int)cereal::SelfdriveState::AlertStatus::CRITICAL] = TimelineType::AlertCritical,
-  };
-
-  const auto &route_segments = route_->segments();
-  for (auto it = route_segments.cbegin(); it != route_segments.cend() && !exit_; ++it) {
-    std::shared_ptr<LogReader> log(new LogReader());
-    if (!log->load(it->second.qlog, &exit_, !hasFlag(REPLAY_FLAG_NO_FILE_CACHE), 0, 3) || log->events.empty()) continue;
-
-    std::vector<std::tuple<double, double, TimelineType>> timeline;
-    for (const Event &e : log->events) {
-      if (e.which == cereal::Event::Which::SELFDRIVE_STATE) {
-        capnp::FlatArrayMessageReader reader(e.data);
-        auto event = reader.getRoot<cereal::Event>();
-        auto cs = event.getSelfdriveState();
-
-        if (engaged != cs.getEnabled()) {
-          if (engaged) {
-            timeline.push_back({toSeconds(engaged_begin), toSeconds(e.mono_time), TimelineType::Engaged});
-          }
-          engaged_begin = e.mono_time;
-          engaged = cs.getEnabled();
-        }
-
-        if (alert_type != cs.getAlertType().cStr() || alert_status != cs.getAlertStatus()) {
-          if (!alert_type.empty() && alert_size != cereal::SelfdriveState::AlertSize::NONE) {
-            timeline.push_back({toSeconds(alert_begin), toSeconds(e.mono_time), timeline_types[(int)alert_status]});
-          }
-          alert_begin = e.mono_time;
-          alert_type = cs.getAlertType().cStr();
-          alert_size = cs.getAlertSize();
-          alert_status = cs.getAlertStatus();
-        }
-      } else if (e.which == cereal::Event::Which::USER_FLAG) {
-        timeline.push_back({toSeconds(e.mono_time), toSeconds(e.mono_time), TimelineType::UserFlag});
-      }
-    }
-
-    if (it->first == route_segments.rbegin()->first) {
-      if (engaged) {
-        timeline.push_back({toSeconds(engaged_begin), toSeconds(log->events.back().mono_time), TimelineType::Engaged});
-      }
-      if (!alert_type.empty() && alert_size != cereal::SelfdriveState::AlertSize::NONE) {
-        timeline.push_back({toSeconds(alert_begin), toSeconds(log->events.back().mono_time), timeline_types[(int)alert_status]});
-      }
-
-      max_seconds_ = std::ceil(toSeconds(log->events.back().mono_time));
-      emit minMaxTimeChanged(route_segments.cbegin()->first * 60.0, max_seconds_);
-    }
-    {
-      std::lock_guard lk(timeline_lock);
-      timeline_.insert(timeline_.end(), timeline.begin(), timeline.end());
-      std::sort(timeline_.begin(), timeline_.end(), [](auto &l, auto &r) { return std::get<2>(l) < std::get<2>(r); });
-    }
-    emit qLogLoaded(log);
-  }
-}
-
-std::optional<uint64_t> Replay::find(FindFlag flag) {
-  int cur_ts = currentSeconds();
-  for (auto [start_ts, end_ts, type] : getTimeline()) {
-    if (type == TimelineType::Engaged) {
-      if (flag == FindFlag::nextEngagement && start_ts > cur_ts) {
-        return start_ts;
-      } else if (flag == FindFlag::nextDisEngagement && end_ts > cur_ts) {
-        return end_ts;
-      }
-    } else if (start_ts > cur_ts) {
-      if ((flag == FindFlag::nextUserFlag && type == TimelineType::UserFlag) ||
-          (flag == FindFlag::nextInfo && type == TimelineType::AlertInfo) ||
-          (flag == FindFlag::nextWarning && type == TimelineType::AlertWarning) ||
-          (flag == FindFlag::nextCritical && type == TimelineType::AlertCritical)) {
-        return start_ts;
-      }
-    }
-  }
-  return std::nullopt;
-}
-
 void Replay::pause(bool pause) {
   if (user_paused_ != pause) {
     pauseStreamThread();
@@ -266,16 +181,15 @@ void Replay::pauseStreamThread() {
   }
 }
 
-void Replay::segmentLoadFinished(bool success) {
+void Replay::segmentLoadFinished(int seg_num, bool success) {
   if (!success) {
-    Segment *seg = qobject_cast<Segment *>(sender());
-    rWarning("failed to load segment %d, removing it from current replay list", seg->seg_num);
+    rWarning("failed to load segment %d, removing it from current replay list", seg_num);
     updateEvents([&]() {
-      segments_.erase(seg->seg_num);
+      segments_.erase(seg_num);
       return !segments_.empty();
     });
   }
-  updateSegmentsCache();
+  QMetaObject::invokeMethod(this, &Replay::updateSegmentsCache, Qt::QueuedConnection);
 }
 
 void Replay::updateSegmentsCache() {
@@ -306,8 +220,10 @@ void Replay::loadSegmentInRange(SegmentMap::iterator begin, SegmentMap::iterator
     auto it = std::find_if(first, last, [](const auto &seg_it) { return !seg_it.second || !seg_it.second->isLoaded(); });
     if (it != last && !it->second) {
       rDebug("loading segment %d...", it->first);
-      it->second = std::make_unique<Segment>(it->first, route_->at(it->first), flags_, filters_);
-      QObject::connect(it->second.get(), &Segment::loadFinished, this, &Replay::segmentLoadFinished);
+      it->second = std::make_unique<Segment>(it->first, route_->at(it->first), flags_, filters_,
+                                             [this](int seg_num, bool success) {
+                                               segmentLoadFinished(seg_num, success);
+                                             });
       return true;
     }
     return false;
@@ -373,7 +289,7 @@ void Replay::startStream(const Segment *cur_segment) {
     auto event = reader.getRoot<cereal::Event>();
     uint64_t wall_time = event.getInitData().getWallTimeNanos();
     if (wall_time > 0) {
-      route_date_time_ = QDateTime::fromMSecsSinceEpoch(wall_time / 1e6);
+      route_date_time_ = wall_time / 1e6;
     }
   }
 
@@ -405,12 +321,16 @@ void Replay::startStream(const Segment *cur_segment) {
   }
 
   emit segmentsMerged();
+
+  timeline_.initialize(*route_, route_start_ts_, !(flags_ & REPLAY_FLAG_NO_FILE_CACHE),
+                       [this](std::shared_ptr<LogReader> log) {
+                         notifyEvent(onQLogLoaded, log);
+                       });
   // start stream thread
   stream_thread_ = new QThread();
   QObject::connect(stream_thread_, &QThread::started, [=]() { streamThread(); });
   stream_thread_->start();
 
-  timeline_future = QtConcurrent::run(this, &Replay::buildTimeline);
   emit streamStarted();
 }
 
diff --git a/tools/replay/replay.h b/tools/replay/replay.h
index e828b369aa..d3f5425308 100644
--- a/tools/replay/replay.h
+++ b/tools/replay/replay.h
@@ -6,7 +6,6 @@
 #include <optional>
 #include <set>
 #include <string>
-#include <tuple>
 #include <vector>
 #include <utility>
 
@@ -14,6 +13,7 @@
 
 #include "tools/replay/camera.h"
 #include "tools/replay/route.h"
+#include "tools/replay/timeline.h"
 
 #define DEMO_ROUTE "a2a0ccea32023010|2023-07-27--13-01-19"
 
@@ -32,19 +32,8 @@ enum REPLAY_FLAGS {
   REPLAY_FLAG_ALL_SERVICES = 0x0800,
 };
 
-enum class FindFlag {
-  nextEngagement,
-  nextDisEngagement,
-  nextUserFlag,
-  nextInfo,
-  nextWarning,
-  nextCritical
-};
-
-enum class TimelineType { None, Engaged, AlertInfo, AlertWarning, AlertCritical, UserFlag };
 typedef bool (*replayEventFilter)(const Event *, void *);
 typedef std::map<int, std::unique_ptr<Segment>> SegmentMap;
-Q_DECLARE_METATYPE(std::shared_ptr<LogReader>);
 
 class Replay : public QObject {
   Q_OBJECT
@@ -75,8 +64,7 @@ public:
   inline void removeFlag(REPLAY_FLAGS flag) { flags_ &= ~flag; }
   inline const Route* route() const { return route_.get(); }
   inline double currentSeconds() const { return double(cur_mono_time_ - route_start_ts_) / 1e9; }
-  inline QDateTime routeDateTime() const { return route_date_time_; }
-  inline QDateTime currentDateTime() const { return route_date_time_.addSecs(currentSeconds()); }
+  inline std::time_t routeDateTime() const { return route_date_time_; }
   inline uint64_t routeStartNanos() const { return route_start_ts_; }
   inline double toSeconds(uint64_t mono_time) const { return (mono_time - route_start_ts_) / 1e9; }
   inline double minSeconds() const { return !segments_.empty() ? segments_.begin()->first * 60 : 0; }
@@ -85,22 +73,20 @@ public:
   inline float getSpeed() const { return speed_; }
   inline const SegmentMap &segments() const { return segments_; }
   inline const std::string &carFingerprint() const { return car_fingerprint_; }
-  inline const std::vector<std::tuple<double, double, TimelineType>> getTimeline() {
-    std::lock_guard lk(timeline_lock);
-    return timeline_;
-  }
+  inline const std::shared_ptr<std::vector<Timeline::Entry>> getTimeline() const { return timeline_.get(); }
+  inline const std::optional<Timeline::Entry> findAlertAtTime(double sec) const { return timeline_.findAlertAtTime(sec); }
+
+  // Event callback functions
+  std::function<void(std::shared_ptr<LogReader>)> onQLogLoaded = nullptr;
+
 
 signals:
   void streamStarted();
   void segmentsMerged();
   void seeking(double sec);
   void seekedTo(double sec);
-  void qLogLoaded(std::shared_ptr<LogReader> qlog);
   void minMaxTimeChanged(double min_sec, double max_sec);
 
-protected slots:
-  void segmentLoadFinished(bool success);
-
 protected:
   std::optional<uint64_t> find(FindFlag flag);
   void pauseStreamThread();
@@ -108,16 +94,18 @@ protected:
   void streamThread();
   void updateSegmentsCache();
   void loadSegmentInRange(SegmentMap::iterator begin, SegmentMap::iterator cur, SegmentMap::iterator end);
+  void segmentLoadFinished(int seg_num, bool success);
   void mergeSegments(const SegmentMap::iterator &begin, const SegmentMap::iterator &end);
   void updateEvents(const std::function<bool()>& update_events_function);
   std::vector<Event>::const_iterator publishEvents(std::vector<Event>::const_iterator first,
                                                    std::vector<Event>::const_iterator last);
   void publishMessage(const Event *e);
   void publishFrame(const Event *e);
-  void buildTimeline();
   void checkSeekProgress();
   inline bool isSegmentMerged(int n) const { return merged_segments_.count(n) > 0; }
 
+  Timeline timeline_;
+
   pthread_t stream_thread_id = 0;
   QThread *stream_thread_ = nullptr;
   std::mutex stream_lock_;
@@ -130,7 +118,7 @@ protected:
   std::atomic<bool> exit_ = false;
   std::atomic<bool> paused_ = false;
   bool events_ready_ = false;
-  QDateTime route_date_time_;
+  std::time_t route_date_time_;
   uint64_t route_start_ts_ = 0;
   std::atomic<uint64_t> cur_mono_time_ = 0;
   std::atomic<double> max_seconds_ = 0;
@@ -146,9 +134,6 @@ protected:
   std::unique_ptr<CameraServer> camera_server_;
   std::atomic<uint32_t> flags_ = REPLAY_FLAG_NONE;
 
-  std::mutex timeline_lock;
-  QFuture<void> timeline_future;
-  std::vector<std::tuple<double, double, TimelineType>> timeline_;
   std::string car_fingerprint_;
   std::atomic<float> speed_ = 1.0;
   replayEventFilter event_filter = nullptr;
diff --git a/tools/replay/route.cc b/tools/replay/route.cc
index e298b88b79..0d8d6d8fb7 100644
--- a/tools/replay/route.cc
+++ b/tools/replay/route.cc
@@ -1,10 +1,8 @@
 #include "tools/replay/route.h"
 
-#include <QDir>
 #include <QEventLoop>
 #include <QJsonArray>
 #include <QJsonDocument>
-#include <QtConcurrent>
 #include <array>
 #include <filesystem>
 #include <regex>
@@ -53,7 +51,11 @@ bool Route::load() {
     rInfo("invalid route format");
     return false;
   }
-  date_time_ = QDateTime::fromString(route_.timestamp.c_str(), "yyyy-MM-dd--HH-mm-ss");
+
+  struct tm tm_time = {0};
+  strptime(route_.timestamp.c_str(), "%Y-%m-%d--%H-%M-%S", &tm_time);
+  date_time_ = mktime(&tm_time);
+
   bool ret = data_dir_.empty() ? loadFromServer() : loadFromLocal();
   if (ret) {
     if (route_.begin_segment == -1) route_.begin_segment = segments_.rbegin()->first;
@@ -151,8 +153,9 @@ void Route::addFileToSegment(int n, const std::string &file) {
 
 // class Segment
 
-Segment::Segment(int n, const SegmentFile &files, uint32_t flags, const std::vector<bool> &filters)
-    : seg_num(n), flags(flags), filters_(filters) {
+Segment::Segment(int n, const SegmentFile &files, uint32_t flags, const std::vector<bool> &filters,
+                 std::function<void(int, bool)> callback)
+    : seg_num(n), flags(flags), filters_(filters), onLoadFinished_(callback) {
   // [RoadCam, DriverCam, WideRoadCam, log]. fallback to qcamera/qlog
   const std::array file_list = {
       (flags & REPLAY_FLAG_QCAMERA) || files.road_cam.empty() ? files.qcamera : files.road_cam,
@@ -163,16 +166,20 @@ Segment::Segment(int n, const SegmentFile &files, uint32_t flags, const std::vec
   for (int i = 0; i < file_list.size(); ++i) {
     if (!file_list[i].empty() && (!(flags & REPLAY_FLAG_NO_VIPC) || i >= MAX_CAMERAS)) {
       ++loading_;
-      synchronizer_.addFuture(QtConcurrent::run(this, &Segment::loadFile, i, file_list[i]));
+      threads_.emplace_back(&Segment::loadFile, this, i, file_list[i]);
     }
   }
 }
 
 Segment::~Segment() {
-  disconnect();
+  {
+    std::lock_guard lock(mutex_);
+    onLoadFinished_ = nullptr;  // Prevent callback after destruction
+  }
   abort_ = true;
-  synchronizer_.setCancelOnWait(true);
-  synchronizer_.waitForFinished();
+  for (auto &thread : threads_) {
+    if (thread.joinable()) thread.join();
+  }
 }
 
 void Segment::loadFile(int id, const std::string file) {
@@ -192,6 +199,9 @@ void Segment::loadFile(int id, const std::string file) {
   }
 
   if (--loading_ == 0) {
-    emit loadFinished(!abort_);
+    std::lock_guard lock(mutex_);
+    if (onLoadFinished_) {
+      onLoadFinished_(seg_num, !abort_);
+    }
   }
 }
diff --git a/tools/replay/route.h b/tools/replay/route.h
index 9c1cc37e2a..a2a8121de7 100644
--- a/tools/replay/route.h
+++ b/tools/replay/route.h
@@ -2,11 +2,12 @@
 
 #include <map>
 #include <memory>
+#include <mutex>
 #include <string>
+#include <thread>
 #include <vector>
 
-#include <QDateTime>
-#include <QFutureSynchronizer>
+#include <QString>
 
 #include "tools/replay/framereader.h"
 #include "tools/replay/logreader.h"
@@ -43,7 +44,7 @@ public:
   bool load();
   RouteLoadError lastError() const { return err_; }
   inline const std::string &name() const { return route_.str; }
-  inline const QDateTime datetime() const { return date_time_; }
+  inline const std::time_t datetime() const { return date_time_; }
   inline const std::string &dir() const { return data_dir_; }
   inline const RouteIdentifier &identifier() const { return route_; }
   inline const std::map<int, SegmentFile> &segments() const { return segments_; }
@@ -58,15 +59,14 @@ protected:
   RouteIdentifier route_ = {};
   std::string data_dir_;
   std::map<int, SegmentFile> segments_;
-  QDateTime date_time_;
+  std::time_t date_time_;
   RouteLoadError err_ = RouteLoadError::None;
 };
 
-class Segment : public QObject {
-  Q_OBJECT
-
+class Segment {
 public:
-  Segment(int n, const SegmentFile &files, uint32_t flags, const std::vector<bool> &filters = {});
+  Segment(int n, const SegmentFile &files, uint32_t flags, const std::vector<bool> &filters,
+          std::function<void(int, bool)> callback);
   ~Segment();
   inline bool isLoaded() const { return !loading_ && !abort_; }
 
@@ -74,15 +74,14 @@ public:
   std::unique_ptr<LogReader> log;
   std::unique_ptr<FrameReader> frames[MAX_CAMERAS] = {};
 
-signals:
-  void loadFinished(bool success);
-
 protected:
   void loadFile(int id, const std::string file);
 
   std::atomic<bool> abort_ = false;
   std::atomic<int> loading_ = 0;
-  QFutureSynchronizer<void> synchronizer_;
+  std::mutex mutex_;
+  std::vector<std::thread> threads_;
+  std::function<void(int, bool)> onLoadFinished_ = nullptr;
   uint32_t flags;
   std::vector<bool> filters_;
 };
diff --git a/tools/replay/tests/test_replay.cc b/tools/replay/tests/test_replay.cc
index 2fe468e726..d350df570a 100644
--- a/tools/replay/tests/test_replay.cc
+++ b/tools/replay/tests/test_replay.cc
@@ -72,9 +72,9 @@ TEST_CASE("LogReader") {
 }
 
 void read_segment(int n, const SegmentFile &segment_file, uint32_t flags) {
-  QEventLoop loop;
-  Segment segment(n, segment_file, flags);
-  QObject::connect(&segment, &Segment::loadFinished, [&]() {
+  std::mutex mutex;
+  std::condition_variable cv;
+  Segment segment(n, segment_file, flags, {}, [&](int, bool) {
     REQUIRE(segment.isLoaded() == true);
     REQUIRE(segment.log != nullptr);
     REQUIRE(segment.frames[RoadCam] != nullptr);
@@ -105,10 +105,11 @@ void read_segment(int n, const SegmentFile &segment_file, uint32_t flags) {
         REQUIRE(fr->get(i, &buf));
       }
     }
-
-    loop.quit();
+    cv.notify_one();
   });
-  loop.exec();
+
+  std::unique_lock lock(mutex);
+  cv.wait(lock);
 }
 
 std::string download_demo_route() {
diff --git a/tools/replay/timeline.cc b/tools/replay/timeline.cc
new file mode 100644
index 0000000000..5a4f58a46f
--- /dev/null
+++ b/tools/replay/timeline.cc
@@ -0,0 +1,109 @@
+#include "tools/replay/timeline.h"
+
+#include <array>
+
+#include "cereal/gen/cpp/log.capnp.h"
+
+Timeline::~Timeline() {
+  should_exit_.store(true);
+  if (thread_.joinable()) {
+    thread_.join();
+  }
+}
+
+void Timeline::initialize(const Route &route, uint64_t route_start_ts, bool local_cache,
+                          std::function<void(std::shared_ptr<LogReader>)> callback) {
+  thread_ = std::thread(&Timeline::buildTimeline, this, route, route_start_ts, local_cache, callback);
+}
+
+std::optional<uint64_t> Timeline::find(double cur_ts, FindFlag flag) const {
+  for (const auto &entry : *get()) {
+    if (entry.type == TimelineType::Engaged) {
+      if (flag == FindFlag::nextEngagement && entry.start_time > cur_ts) {
+        return entry.start_time;
+      } else if (flag == FindFlag::nextDisEngagement && entry.end_time > cur_ts) {
+        return entry.end_time;
+      }
+    } else if (entry.start_time > cur_ts) {
+      if ((flag == FindFlag::nextUserFlag && entry.type == TimelineType::UserFlag) ||
+          (flag == FindFlag::nextInfo && entry.type == TimelineType::AlertInfo) ||
+          (flag == FindFlag::nextWarning && entry.type == TimelineType::AlertWarning) ||
+          (flag == FindFlag::nextCritical && entry.type == TimelineType::AlertCritical)) {
+        return entry.start_time;
+      }
+    }
+  }
+  return std::nullopt;
+}
+
+std::optional<Timeline::Entry> Timeline::findAlertAtTime(double target_time) const {
+  for (const auto &entry : *get()) {
+    if (entry.start_time > target_time) break;
+    if (entry.end_time >= target_time && entry.type >= TimelineType::AlertInfo) {
+      return entry;
+    }
+  }
+  return std::nullopt;
+}
+
+void Timeline::buildTimeline(const Route &route, uint64_t route_start_ts, bool local_cache,
+                             std::function<void(std::shared_ptr<LogReader>)> callback) {
+  std::optional<size_t> current_engaged_idx, current_alert_idx;
+
+  for (const auto &segment : route.segments()) {
+    if (should_exit_) break;
+
+    auto log = std::make_shared<LogReader>();
+    if (!log->load(segment.second.qlog, &should_exit_, local_cache, 0, 3) || log->events.empty()) {
+      continue;  // Skip if log loading fails or no events
+    }
+
+    for (const Event &e : log->events) {
+      double seconds = (e.mono_time - route_start_ts) / 1e9;
+      if (e.which == cereal::Event::Which::SELFDRIVE_STATE) {
+        capnp::FlatArrayMessageReader reader(e.data);
+        auto cs = reader.getRoot<cereal::Event>().getSelfdriveState();
+        updateEngagementStatus(cs, current_engaged_idx, seconds);
+        updateAlertStatus(cs, current_alert_idx, seconds);
+      } else if (e.which == cereal::Event::Which::USER_FLAG) {
+        staging_entries_.emplace_back(Entry{seconds, seconds, TimelineType::UserFlag});
+      }
+    }
+
+    callback(log);  // Notify the callback once the log is processed
+
+    // Sort and finalize the timeline entries
+    std::sort(staging_entries_.begin(), staging_entries_.end(), [](auto &a, auto &b) { return a.start_time < b.start_time; });
+    timeline_entries_ = std::make_shared<std::vector<Entry>>(staging_entries_);
+  }
+}
+
+void Timeline::updateEngagementStatus(const cereal::SelfdriveState::Reader &cs, std::optional<size_t> &idx, double seconds) {
+  if (idx) staging_entries_[*idx].end_time = seconds;
+  if (cs.getEnabled()) {
+    if (!idx) {
+      idx = staging_entries_.size();
+      staging_entries_.emplace_back(Entry{seconds, seconds, TimelineType::Engaged});
+    }
+  } else {
+    idx.reset();
+  }
+}
+
+void Timeline::updateAlertStatus(const cereal::SelfdriveState::Reader &cs, std::optional<size_t> &idx, double seconds) {
+  static auto alert_types = std::array{TimelineType::AlertInfo, TimelineType::AlertWarning, TimelineType::AlertCritical};
+
+  Entry *entry = idx ? &staging_entries_[*idx] : nullptr;
+  if (entry) entry->end_time = seconds;
+  if (cs.getAlertSize() != cereal::SelfdriveState::AlertSize::NONE) {
+    auto type = alert_types[(int)cs.getAlertStatus()];
+    std::string text1 = cs.getAlertText1().cStr();
+    std::string text2 = cs.getAlertText2().cStr();
+    if (!entry || entry->type != type || entry->text1 != text1 || entry->text2 != text2) {
+      idx = staging_entries_.size();
+      staging_entries_.emplace_back(Entry{seconds, seconds, type, text1, text2});  // Start a new entry
+    }
+  } else {
+    idx.reset();
+  }
+}
diff --git a/tools/replay/timeline.h b/tools/replay/timeline.h
new file mode 100644
index 0000000000..b2535fd8b0
--- /dev/null
+++ b/tools/replay/timeline.h
@@ -0,0 +1,46 @@
+#pragma once
+
+#include <atomic>
+#include <optional>
+#include <thread>
+#include <vector>
+
+#include "tools/replay/route.h"
+
+enum class TimelineType { None, Engaged, AlertInfo, AlertWarning, AlertCritical, UserFlag };
+enum class FindFlag { nextEngagement, nextDisEngagement, nextUserFlag, nextInfo, nextWarning, nextCritical };
+
+class Timeline {
+public:
+  struct Entry {
+    double start_time;
+    double end_time;
+    TimelineType type;
+    std::string text1;
+    std::string text2;
+  };
+
+  Timeline() : timeline_entries_(std::make_shared<std::vector<Entry>>()) {}
+  ~Timeline();
+
+  void initialize(const Route &route, uint64_t route_start_ts, bool local_cache,
+                  std::function<void(std::shared_ptr<LogReader>)> callback);
+  std::optional<uint64_t> find(double cur_ts, FindFlag flag) const;
+  std::optional<Entry> findAlertAtTime(double target_time) const;
+  const std::shared_ptr<std::vector<Entry>> get() const { return timeline_entries_; }
+
+private:
+ void buildTimeline(const Route &route, uint64_t route_start_ts, bool local_cache,
+                    std::function<void(std::shared_ptr<LogReader>)> callback);
+ void updateEngagementStatus(const cereal::SelfdriveState::Reader &cs, std::optional<size_t> &idx, double seconds);
+ void updateAlertStatus(const cereal::SelfdriveState::Reader &cs, std::optional<size_t> &idx, double seconds);
+
+ std::thread thread_;
+ std::atomic<bool> should_exit_ = false;
+
+ // Temporarily holds entries before they are sorted and finalized
+ std::vector<Entry> staging_entries_;
+
+ // Final sorted timeline entries
+ std::shared_ptr<std::vector<Entry>> timeline_entries_;
+};
diff --git a/tools/replay/util.cc b/tools/replay/util.cc
index 91f6af4f84..fac1e11c47 100644
--- a/tools/replay/util.cc
+++ b/tools/replay/util.cc
@@ -14,7 +14,6 @@
 #include <map>
 #include <mutex>
 #include <numeric>
-#include <sstream>
 #include <utility>
 #include <zstd.h>
 
@@ -404,15 +403,6 @@ std::vector<std::string> split(std::string_view source, char delimiter) {
   return fields;
 }
 
-std::string join(const std::vector<std::string> &elements, char separator) {
-  std::ostringstream oss;
-  for (size_t i = 0; i < elements.size(); ++i) {
-    if (i != 0) oss << separator;
-    oss << elements[i];
-  }
-  return oss.str();
-}
-
 std::string extractFileName(const std::string &file) {
   size_t queryPos = file.find_first_of("?");
   std::string path = (queryPos != std::string::npos) ? file.substr(0, queryPos) : file;
diff --git a/tools/replay/util.h b/tools/replay/util.h
index 317b964181..46df2bc191 100644
--- a/tools/replay/util.h
+++ b/tools/replay/util.h
@@ -3,6 +3,7 @@
 #include <atomic>
 #include <deque>
 #include <functional>
+#include <sstream>
 #include <string>
 #include <string_view>
 #include <vector>
@@ -59,6 +60,15 @@ typedef std::function<void(uint64_t cur, uint64_t total, bool success)> Download
 void installDownloadProgressHandler(DownloadProgressHandler);
 bool httpDownload(const std::string &url, const std::string &file, size_t chunk_size = 0, std::atomic<bool> *abort = nullptr);
 std::string formattedDataSize(size_t size);
-std::vector<std::string> split(std::string_view source, char delimiter);
-std::string join(const std::vector<std::string> &elements, char separator);
 std::string extractFileName(const std::string& file);
+std::vector<std::string> split(std::string_view source, char delimiter);
+
+template <typename Iterable>
+std::string join(const Iterable& elements, const std::string& separator) {
+  std::ostringstream oss;
+  for (auto it = elements.begin(); it != elements.end(); ++it) {
+    if (it != elements.begin()) oss << separator;
+    oss << *it;
+  }
+  return oss.str();
+}