Handle track republish after full-reconnect

include/livekit/local_participant.h

@@ -293,6 +293,10 @@ class LIVEKIT_API LocalParticipant : public Participant {
   friend class Room;
 
 private:
+  /// Guards published_tracks_by_sid_ and coordinated publication/track updates.
+  /// Never held across blocking FFI requests. When both this and Room::lock_
+  /// are needed, acquire Room::lock_ first.
+  mutable std::mutex published_tracks_mutex_;
   /// Publication SID → local track (@ref unpublishTrack clears the track’s
   /// cached publication). @c mutable so @ref trackPublications() const can
   /// prune expired @c weak_ptr entries.

include/livekit/local_track_publication.h

@@ -23,14 +23,21 @@ namespace livekit {
 
 namespace proto {
 class OwnedTrackPublication;
-}
+class TrackPublicationInfo;
+} // namespace proto
 
 /// @brief A track published by a local participant.
 class LIVEKIT_API LocalTrackPublication : public TrackPublication {
 public:
   /// Note, this LocalTrackPublication is constructed internally only;
   /// safe to accept proto::OwnedTrackPublication.
   explicit LocalTrackPublication(const proto::OwnedTrackPublication& owned);
+
+private:
+  friend class Room;
+
+  /// Refresh publication metadata after a full reconnect republish.
+  void updateInfo(const proto::TrackPublicationInfo& info);
 };
 
 } // namespace livekit

src/ffi_client.cpp

@@ -103,6 +103,8 @@ std::optional<FfiClient::AsyncId> ExtractAsyncId(const proto::FfiEvent& event) {
       return event.get_stats().async_id();
     case E::kGetSessionStats:
       return event.get_session_stats().async_id();
+    case E::kSimulateScenario:
+      return event.simulate_scenario().async_id();
     case E::kPublishSipDtmf:
       return event.publish_sip_dtmf().async_id();
     case E::kChatMessage:
@@ -655,6 +657,42 @@ std::future<SessionStats> FfiClient::getSessionStatsAsync(uintptr_t room_handle)
   return fut;
 }
 
+std::future<void> FfiClient::simulateScenarioAsync(uintptr_t room_handle, int scenario) {
+  const AsyncId async_id = generateAsyncId();
+
+  auto fut = registerAsync<void>(
+      async_id,
+      [async_id](const proto::FfiEvent& event) {
+        return event.has_simulate_scenario() && event.simulate_scenario().async_id() == async_id;
+      },
+      [](const proto::FfiEvent& event, std::promise<void>& pr) {
+        const auto& cb = event.simulate_scenario();
+        if (cb.has_error() && !cb.error().empty()) {
+          pr.set_exception(std::make_exception_ptr(std::runtime_error(cb.error())));
+          return;
+        }
+        pr.set_value();
+      });
+
+  proto::FfiRequest req;
+  auto* msg = req.mutable_simulate_scenario();
+  msg->set_room_handle(room_handle);
+  msg->set_scenario(static_cast<proto::SimulateScenarioKind>(scenario));
+  msg->set_request_async_id(async_id);
+
+  try {
+    const proto::FfiResponse resp = sendRequest(req);
+    if (!resp.has_simulate_scenario()) {
+      logAndThrow("FfiResponse missing simulate_scenario");
+    }
+  } catch (...) {
+    cancelPendingByAsyncId(async_id);
+    throw;
+  }
+
+  return fut;
+}
+
 // Participant APIs Implementation
 std::future<proto::OwnedTrackPublication> FfiClient::publishTrackAsync(std::uint64_t local_participant_handle,
                                                                        std::uint64_t track_handle,

src/ffi_client.h

@@ -106,6 +106,8 @@ class LIVEKIT_INTERNAL_API FfiClient {
 
   std::future<SessionStats> getSessionStatsAsync(uintptr_t room_handle);
 
+  std::future<void> simulateScenarioAsync(uintptr_t room_handle, int scenario);
+
   // Participant APIs
   std::future<proto::OwnedTrackPublication> publishTrackAsync(std::uint64_t local_participant_handle,
                                                               std::uint64_t track_handle,

src/local_participant.cpp

@@ -18,6 +18,7 @@
 
 #include <chrono>
 #include <memory>
+#include <mutex>
 #include <stdexcept>
 
 #include "data_track.pb.h"
@@ -200,9 +201,11 @@ void LocalParticipant::publishTrack(const std::shared_ptr<Track>& track, const T
   auto publication = std::make_shared<LocalTrackPublication>(owned_pub);
 
   const std::string sid = publication->sid();
-  published_tracks_by_sid_[sid] = std::weak_ptr<Track>(track);
-
-  track->setPublication(publication);
+  {
+    const std::scoped_lock<std::mutex> guard(published_tracks_mutex_);
+    published_tracks_by_sid_[sid] = std::weak_ptr<Track>(track);
+    track->setPublication(publication);
+  }
 }
 
 std::shared_ptr<LocalVideoTrack> LocalParticipant::publishVideoTrack(const std::string& name,
@@ -248,16 +251,20 @@ void LocalParticipant::unpublishTrack(const std::string& track_sid) {
 
   fut.get();
 
-  if (auto it = published_tracks_by_sid_.find(track_sid); it != published_tracks_by_sid_.end()) {
-    if (auto t = it->second.lock()) {
-      t->setPublication(nullptr);
+  {
+    const std::scoped_lock<std::mutex> guard(published_tracks_mutex_);
+    if (auto it = published_tracks_by_sid_.find(track_sid); it != published_tracks_by_sid_.end()) {
+      if (auto t = it->second.lock()) {
+        t->setPublication(nullptr);
+      }
+      published_tracks_by_sid_.erase(it);
     }
-    published_tracks_by_sid_.erase(it);
   }
 }
 
 LocalParticipant::PublicationMap LocalParticipant::trackPublications() const {
   PublicationMap out;
+  const std::scoped_lock<std::mutex> guard(published_tracks_mutex_);
   for (auto it = published_tracks_by_sid_.begin(); it != published_tracks_by_sid_.end();) {
     auto t = it->second.lock();
     if (!t) {
@@ -494,6 +501,7 @@ void LocalParticipant::handleRpcMethodInvocation(uint64_t invocation_id, const s
 }
 
 std::shared_ptr<TrackPublication> LocalParticipant::findTrackPublication(const std::string& sid) const {
+  const std::scoped_lock<std::mutex> guard(published_tracks_mutex_);
   auto it = published_tracks_by_sid_.find(sid);
   if (it == published_tracks_by_sid_.end()) {
     return nullptr;

src/local_track_publication.cpp

@@ -16,6 +16,7 @@
 
 #include "livekit/local_track_publication.h"
 
+#include "track.pb.h"
 #include "track_proto_converter.h"
 
 namespace livekit {
@@ -27,4 +28,18 @@ LocalTrackPublication::LocalTrackPublication(const proto::OwnedTrackPublication&
                        static_cast<EncryptionType>(owned.info().encryption_type()),
                        convertAudioFeatures(owned.info().audio_features())) {}
 
+void LocalTrackPublication::updateInfo(const proto::TrackPublicationInfo& info) {
+  sid_ = info.sid();
+  name_ = info.name();
+  kind_ = fromProto(info.kind());
+  source_ = fromProto(info.source());
+  simulcasted_ = info.simulcasted();
+  width_ = info.width();
+  height_ = info.height();
+  mime_type_ = info.mime_type();
+  muted_ = info.muted();
+  encryption_type_ = static_cast<EncryptionType>(info.encryption_type());
+  audio_features_ = convertAudioFeatures(info.audio_features());
+}
+
 } // namespace livekit

src/room.cpp

@@ -20,7 +20,10 @@
 #include "ffi_client.h"
 #include "livekit/audio_stream.h"
 #include "livekit/e2ee.h"
+#include "livekit/local_audio_track.h"
 #include "livekit/local_participant.h"
+#include "livekit/local_track_publication.h"
+#include "livekit/local_video_track.h"
 #include "livekit/remote_audio_track.h"
 #include "livekit/remote_data_track.h"
 #include "livekit/remote_participant.h"
@@ -47,6 +50,19 @@ using proto::FfiResponse;
 
 namespace {
 
+std::shared_ptr<LocalTrackPublication> localTrackPublication(const std::shared_ptr<Track>& track) {
+  if (!track) {
+    return nullptr;
+  }
+  if (auto video = std::dynamic_pointer_cast<LocalVideoTrack>(track)) {
+    return video->publication();
+  }
+  if (auto audio = std::dynamic_pointer_cast<LocalAudioTrack>(track)) {
+    return audio->publication();
+  }
+  return nullptr;
+}
+
 std::shared_ptr<livekit::RemoteParticipant> createRemoteParticipant(const proto::OwnedParticipant& owned) {
   const auto& pinfo = owned.info();
   std::unordered_map<std::string, std::string> attrs;
@@ -593,6 +609,39 @@ void Room::onEvent(const FfiEvent& event) {
           }
           break;
         }
+        case proto::RoomEvent::kLocalTrackRepublished: {
+          const std::scoped_lock<std::mutex> guard(lock_);
+          if (!local_participant_) {
+            LK_LOG_ERROR("kLocalTrackRepublished: local_participant_ is nullptr");
+            break;
+          }
+          const auto& local_track_repub = re.local_track_republished();
+          const std::string& previous_sid = local_track_repub.previous_sid();
+
+          const std::scoped_lock<std::mutex> tracks_guard(local_participant_->published_tracks_mutex_);
+          auto& published_tracks = local_participant_->published_tracks_by_sid_;
+          auto it = published_tracks.find(previous_sid);
+          if (it == published_tracks.end()) {
+            LK_LOG_WARN("local_track_republished for unknown previous sid: {}", previous_sid);
+            break;
+          }
+          auto track = it->second.lock();
+          if (!track) {
+            published_tracks.erase(it);
+            LK_LOG_WARN("local_track_republished for expired previous sid: {}", previous_sid);
+            break;
+          }
+          auto publication = localTrackPublication(track);
+          if (!publication) {
+            LK_LOG_WARN("local_track_republished missing publication for sid: {}", previous_sid);
+            break;
+          }
+          publication->updateInfo(local_track_repub.info());
+          published_tracks.erase(it);
+          published_tracks[publication->sid()] = track;
+          track->setPublication(publication);
+          break;
+        }
         case proto::RoomEvent::kLocalTrackSubscribed: {
           LocalTrackSubscribedEvent ev;
           {

src/tests/common/room_test_access.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2026 LiveKit
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <livekit/livekit.h>
+
+#include <memory>
+#include <mutex>
+#include <stdexcept>
+
+#include "ffi_client.h"
+#include "room.pb.h"
+
+namespace livekit {
+
+struct RoomTestAccess {
+  static int listenerId(const Room& room) {
+    const std::scoped_lock<std::mutex> guard(room.lock_);
+    return room.listener_id_;
+  }
+
+  static void simulateScenario(Room& room, proto::SimulateScenarioKind scenario) {
+    std::shared_ptr<FfiHandle> handle;
+    {
+      const std::scoped_lock<std::mutex> guard(room.lock_);
+      handle = room.room_handle_;
+    }
+    if (!handle) {
+      throw std::runtime_error("cannot simulate scenario for a disconnected room");
+    }
+    FfiClient::instance().simulateScenarioAsync(handle->get(), static_cast<int>(scenario)).get();
+  }
+};
+
+} // namespace livekit

src/tests/integration/test_local_track_publish_sid.cpp

@@ -16,15 +16,21 @@
 
 #include <gtest/gtest.h>
 
+#include <chrono>
 #include <memory>
 #include <string>
+#include <thread>
 
 #include "../common/audio_utils.h"
+#include "../common/room_test_access.h"
 #include "../common/test_common.h"
+#include "room.pb.h"
 
 namespace livekit::test {
 namespace {
 
+using namespace std::chrono_literals;
+
 void expectTrackSidAssigned(const Track& track, const LocalTrackPublication& publication) {
   const std::string& track_sid = track.sid();
   const std::string& publication_sid = publication.sid();
@@ -33,6 +39,17 @@ void expectTrackSidAssigned(const Track& track, const LocalTrackPublication& pub
   EXPECT_EQ(track_sid, publication_sid);
 }
 
+bool waitForSidChange(const Track& track, const std::string& previous_sid, std::chrono::milliseconds timeout) {
+  const auto deadline = std::chrono::steady_clock::now() + timeout;
+  while (std::chrono::steady_clock::now() < deadline) {
+    if (track.sid() != previous_sid && track.sid() != "TR_unknown") {
+      return true;
+    }
+    std::this_thread::sleep_for(50ms);
+  }
+  return track.sid() != previous_sid && track.sid() != "TR_unknown";
+}
+
 } // namespace
 
 class LocalTrackPublishSidTest : public LiveKitTestBase {};
@@ -73,4 +90,34 @@ TEST_F(LocalTrackPublishSidTest, PublishAudioTrackAssignsSid) {
   lockLocalParticipant(room)->unpublishTrack(track->publication()->sid());
 }
 
+TEST_F(LocalTrackPublishSidTest, FullReconnectUpdatesPublishedSid) {
+  failIfNotConfigured();
+
+  Room room;
+  const RoomOptions room_options;
+  ASSERT_TRUE(room.connect(config_.url, config_.token_a, room_options));
+
+  auto source = std::make_shared<EncodedVideoSource>(VideoCodec::H264, 16, 16);
+  std::shared_ptr<LocalVideoTrack> track;
+  ASSERT_NO_THROW(
+      track = lockLocalParticipant(room)->publishVideoTrack("republish-sid-check", source, TrackSource::SOURCE_CAMERA));
+  ASSERT_NE(track, nullptr);
+  ASSERT_NE(track->publication(), nullptr);
+  expectTrackSidAssigned(*track, *track->publication());
+
+  const std::string previous_sid = track->sid();
+  ASSERT_NO_THROW(RoomTestAccess::simulateScenario(room, proto::SIMULATE_FULL_RECONNECT));
+  ASSERT_TRUE(waitForSidChange(*track, previous_sid, 30s)) << "Timed out waiting for republished track SID";
+
+  ASSERT_NE(track->publication(), nullptr);
+  expectTrackSidAssigned(*track, *track->publication());
+  EXPECT_NE(track->sid(), previous_sid);
+
+  const auto pubs = lockLocalParticipant(room)->trackPublications();
+  EXPECT_EQ(pubs.count(previous_sid), 0u);
+  EXPECT_EQ(pubs.count(track->sid()), 1u);
+
+  lockLocalParticipant(room)->unpublishTrack(track->sid());
+}
+
 } // namespace livekit::test

src/tests/integration/test_room.cpp

@@ -29,21 +29,11 @@
 #include <thread>
 #include <vector>
 
+#include "../common/room_test_access.h"
 #include "../common/test_common.h"
 
 using namespace std::chrono_literals;
 
-namespace livekit {
-
-struct RoomTestAccess {
-  static int listenerId(const Room& room) {
-    const std::scoped_lock<std::mutex> guard(room.lock_);
-    return room.listener_id_;
-  }
-};
-
-} // namespace livekit
-
 namespace livekit::test {
 
 // Server-dependent tests - require LIVEKIT_URL and LIVEKIT_TOKEN_A env vars