diff --git a/quiche/quic/moqt/moqt_framer_test.cc b/quiche/quic/moqt/moqt_framer_test.cc
index 79f74fb..482e5c4 100644
--- a/quiche/quic/moqt/moqt_framer_test.cc
+++ b/quiche/quic/moqt/moqt_framer_test.cc
@@ -265,7 +265,8 @@
 };
 
 TEST_F(MoqtFramerSimpleTest, GroupMiddler) {
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(1, 1, true, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(1, 1, true, false, true);
   auto header = std::make_unique<StreamHeaderSubgroupMessage>(type);
   auto buffer1 = SerializeObject(
       framer_, std::get<MoqtObject>(header->structured_data()), "foo", type, 0);
@@ -324,13 +325,15 @@
       std::string(kDefaultExtensionBlob.data(), kDefaultExtensionBlob.size()),
       /*object_status=*/MoqtObjectStatus::kObjectDoesNotExist,
       /*subgroup_id=*/8,
+      /*first_object_in_subgroup=*/true,
       /*payload_length=*/3,
   };
   quiche::QuicheBuffer buffer;
   std::optional<PublishedObjectMetadata> previous;
   EXPECT_QUIC_BUG(
       buffer = framer_.SerializeObjectHeader(
-          object, MoqtDataStreamType::Subgroup(8, 0, false, false), previous),
+          object, MoqtDataStreamType::Subgroup(8, 0, false, false, true),
+          previous),
       "Object metadata is invalid");
   EXPECT_TRUE(buffer.empty());
 }
@@ -345,6 +348,7 @@
       std::string(kDefaultExtensionBlob),
       /*object_status=*/MoqtObjectStatus::kNormal,
       /*subgroup_id=*/std::nullopt,
+      /*first_object_in_subgroup=*/std::nullopt,
       /*payload_length=*/3,
   };
   quiche::QuicheBuffer buffer;
diff --git a/quiche/quic/moqt/moqt_messages.h b/quiche/quic/moqt/moqt_messages.h
index d8c0ac8..edfe38b 100644
--- a/quiche/quic/moqt/moqt_messages.h
+++ b/quiche/quic/moqt/moqt_messages.h
@@ -44,6 +44,7 @@
   static constexpr uint64_t kExtensions = 0x01;
   static constexpr uint64_t kEndOfGroup = 0x08;
   static constexpr uint64_t kDefaultPriority = 0x20;
+  static constexpr uint64_t kHasFirstObject = 0x40;
   // These two cannot simultaneously be true;
   static constexpr uint64_t kFirstObjectId = 0x02;
   static constexpr uint64_t kSubgroupId = 0x04;
@@ -59,7 +60,7 @@
       return std::nullopt;
     }
     if (value > (kSubgroup | kExtensions | kEndOfGroup | kDefaultPriority |
-                 kFirstObjectId | kSubgroupId)) {
+                 kFirstObjectId | kSubgroupId | kHasFirstObject)) {
       // Reserved bits.
       return std::nullopt;
     }
@@ -70,11 +71,9 @@
   }
   static MoqtDataStreamType Fetch() { return MoqtDataStreamType(kFetch); }
   static MoqtDataStreamType Padding() { return MoqtDataStreamType(kPadding); }
-  static MoqtDataStreamType Subgroup(uint64_t subgroup_id,
-                                     uint64_t first_object_id,
-                                     bool no_extension_headers,
-                                     bool default_priority,
-                                     bool end_of_group = false) {
+  static MoqtDataStreamType Subgroup(
+      uint64_t subgroup_id, uint64_t first_object_id, bool no_extension_headers,
+      bool default_priority, bool has_first_object, bool end_of_group = false) {
     uint64_t value = kSubgroup;
     if (!no_extension_headers) {
       value |= kExtensions;
@@ -85,6 +84,9 @@
     if (default_priority) {
       value |= kDefaultPriority;
     }
+    if (has_first_object) {
+      value |= kHasFirstObject;
+    }
     if (subgroup_id == 0) {
       return MoqtDataStreamType(value);
     }
@@ -117,6 +119,9 @@
   bool HasDefaultPriority() const {
     return IsSubgroup() && (value_ & kDefaultPriority);
   }
+  bool HasFirstObject() const {
+    return IsSubgroup() && (value_ & kHasFirstObject);
+  }
 
   uint64_t value() const { return value_; }
   MoqtDataStreamType& operator=(const MoqtDataStreamType& other) = default;
@@ -252,7 +257,8 @@
   MoqtPriority publisher_priority;
   std::string extension_headers;  // Raw, unparsed extension headers.
   MoqtObjectStatus object_status;
-  std::optional<uint64_t> subgroup_id;  // Only for subgroup objects.
+  std::optional<uint64_t> subgroup_id;           // Only for subgroup objects.
+  std::optional<bool> first_object_in_subgroup;  // Only for subgroup objects.
   uint64_t payload_length;
 };
 
diff --git a/quiche/quic/moqt/moqt_object.h b/quiche/quic/moqt/moqt_object.h
index 895a360..996a5e7 100644
--- a/quiche/quic/moqt/moqt_object.h
+++ b/quiche/quic/moqt/moqt_object.h
@@ -29,6 +29,11 @@
   std::string extensions;
   MoqtObjectStatus status = MoqtObjectStatus::kNormal;
   MoqtPriority publisher_priority = kDefaultPublisherPriority;
+  // `first_object_in_subgroup` is only available in objects communicated via
+  // a subscription.  It is not available for the fetched objects; however, the
+  // subscriber can guarantee that all subgroups have a start object by setting
+  // the FETCH range appropriately.
+  std::optional<bool> first_object_in_subgroup;
   // The length of the entire payload, which might include data that is not
   // present in an encompassing PublishedObject or CachedObject.
   uint64_t payload_length;
diff --git a/quiche/quic/moqt/moqt_outgoing_queue.cc b/quiche/quic/moqt/moqt_outgoing_queue.cc
index 71b3e39..9472a89 100644
--- a/quiche/quic/moqt/moqt_outgoing_queue.cc
+++ b/quiche/quic/moqt/moqt_outgoing_queue.cc
@@ -79,6 +79,7 @@
                                    "",
                                    status,
                                    default_publisher_priority(),
+                                   queue_.back().empty(),
                                    payload.length(),
                                    clock_->ApproximateNow()};
   queue_.back().push_back(
diff --git a/quiche/quic/moqt/moqt_outgoing_queue_test.cc b/quiche/quic/moqt/moqt_outgoing_queue_test.cc
index b091536..c1265f9 100644
--- a/quiche/quic/moqt/moqt_outgoing_queue_test.cc
+++ b/quiche/quic/moqt/moqt_outgoing_queue_test.cc
@@ -62,6 +62,7 @@
                                      AnyOf(MoqtObjectStatus::kNormal,
                                            MoqtObjectStatus::kEndOfGroup,
                                            MoqtObjectStatus::kEndOfTrack)))));
+    EXPECT_EQ(object->metadata.first_object_in_subgroup, sequence.object == 0);
     if (object->metadata.status == MoqtObjectStatus::kNormal) {
       PublishObject(object->metadata.location.group,
                     object->metadata.location.object,
diff --git a/quiche/quic/moqt/moqt_parser.cc b/quiche/quic/moqt/moqt_parser.cc
index 19e3377..13bfe26 100644
--- a/quiche/quic/moqt/moqt_parser.cc
+++ b/quiche/quic/moqt/moqt_parser.cc
@@ -1285,6 +1285,10 @@
       if (num_objects_read_ == 0 && type_.SubgroupIsFirstObjectId()) {
         metadata_.subgroup_id = metadata_.object_id;
       }
+      if (type_.IsSubgroup()) {
+        metadata_.first_object_in_subgroup =
+            type_.HasFirstObject() && num_objects_read_ == 0;
+      }
       if (type_.AreExtensionHeadersPresent()) {
         return kExtensionSize;
       }
diff --git a/quiche/quic/moqt/moqt_parser_test.cc b/quiche/quic/moqt/moqt_parser_test.cc
index e3c09f0..7b9d69c 100644
--- a/quiche/quic/moqt/moqt_parser_test.cc
+++ b/quiche/quic/moqt/moqt_parser_test.cc
@@ -463,7 +463,8 @@
   webtransport::test::InMemoryStream stream(/*stream_id=*/0);
   MoqtParserTestVisitor data_visitor;
   MoqtDataParser parser(&stream, &data_visitor);
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(1, 1, true, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(1, 1, true, false, true);
   auto message = std::make_unique<StreamHeaderSubgroupMessage>(type);
   EXPECT_TRUE(message->SetPayloadLength(14));
   message->set_wire_image_size(message->total_message_size() - 11);
@@ -499,7 +500,8 @@
   webtransport::test::InMemoryStream stream(/*stream_id=*/0);
   MoqtParserTestVisitor data_visitor;
   MoqtDataParser parser(&stream, &data_visitor);
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(2, 1, false, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(2, 1, false, false, true);
   auto message = std::make_unique<StreamHeaderSubgroupMessage>(type);
   EXPECT_TRUE(message->SetPayloadLength(payload_length));
 
@@ -533,7 +535,8 @@
   webtransport::test::InMemoryStream stream(/*stream_id=*/0);
   MoqtParserTestVisitor data_visitor;
   MoqtDataParser parser(&stream, &data_visitor);
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(2, 1, false, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(2, 1, false, false, true);
   auto message = std::make_unique<StreamHeaderSubgroupMessage>(type);
 
   // first part
@@ -557,7 +560,8 @@
   MoqtParserTestVisitor data_visitor;
   MoqtDataParser parser(&stream, &data_visitor);
   // first part
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(0, 1, false, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(0, 1, false, false, true);
   auto message1 = std::make_unique<StreamHeaderSubgroupMessage>(type);
   stream.Receive(message1->PacketSample(), false);
   parser.ReadAllData();
@@ -583,7 +587,8 @@
   MoqtParserTestVisitor data_visitor;
   MoqtDataParser parser(&stream, &data_visitor);
   // first part
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(0, 1, false, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(0, 1, false, false, true);
   auto message1 = std::make_unique<StreamHeaderSubgroupMessage>(type);
   message1->ExpandVarints();
   stream.Receive(message1->PacketSample(), false);
@@ -954,7 +959,8 @@
   webtransport::test::InMemoryStream stream(/*stream_id=*/0);
   MoqtParserTestVisitor data_visitor;
   MoqtDataParser parser(&stream, &data_visitor);
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(0, 1, true, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(0, 1, true, false, true);
   auto message = std::make_unique<StreamHeaderSubgroupMessage>(type);
   stream.Receive(
       message->PacketSample().substr(0, message->total_message_size() - 1),
@@ -972,7 +978,8 @@
   webtransport::test::InMemoryStream stream(/*stream_id=*/0);
   MoqtParserTestVisitor data_visitor;
   MoqtDataParser parser(&stream, &data_visitor);
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(0, 1, false, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(0, 1, false, false, true);
   auto message = std::make_unique<StreamHeaderSubgroupMessage>(type);
   // Read up to the extension body and then FIN.
   stream.Receive(message->PacketSample().substr(0, 7), true);
@@ -989,7 +996,8 @@
   webtransport::test::InMemoryStream stream(/*stream_id=*/0);
   MoqtParserTestVisitor data_visitor;
   MoqtDataParser parser(&stream, &data_visitor);
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(1, 1, false, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(1, 1, false, false, true);
   auto message = std::make_unique<StreamHeaderSubgroupMessage>(type);
   stream.Receive(
       message->PacketSample().substr(0, message->total_message_size() - 1),
@@ -1600,7 +1608,8 @@
 };
 
 TEST_F(MoqtDataParserStateMachineTest, ReadAll) {
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(0, 1, false, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(0, 1, false, false, true);
   stream_.Receive(StreamHeaderSubgroupMessage(type).PacketSample());
   stream_.Receive(StreamMiddlerSubgroupMessage(type).PacketSample());
   parser_.ReadAllData();
@@ -1614,7 +1623,8 @@
 }
 
 TEST_F(MoqtDataParserStateMachineTest, ReadObjects) {
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(0, 1, true, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(0, 1, true, false, true);
   stream_.Receive(StreamHeaderSubgroupMessage(type).PacketSample());
   stream_.Receive(StreamMiddlerSubgroupMessage(type).PacketSample(),
                   /*fin=*/true);
@@ -1629,7 +1639,8 @@
 }
 
 TEST_F(MoqtDataParserStateMachineTest, ReadTypeThenObjects) {
-  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(1, 1, false, false);
+  MoqtDataStreamType type =
+      MoqtDataStreamType::Subgroup(1, 1, false, false, true);
   stream_.Receive(StreamHeaderSubgroupMessage(type).PacketSample());
   stream_.Receive(StreamMiddlerSubgroupMessage(type).PacketSample(),
                   /*fin=*/true);
@@ -1742,7 +1753,8 @@
 
 TEST_F(MoqtDataParserStateMachineTest, IntegerOverflowObjectId) {
   MoqtDataStreamType type = MoqtDataStreamType::Subgroup(
-      0, 1, /*no_extension_headers=*/true, /*default_priority=*/false);
+      0, 1, /*no_extension_headers=*/true, /*default_priority=*/false,
+      /*has_first_object=*/true);
   stream_.Receive(StreamHeaderSubgroupMessage(type).PacketSample());
   char buffer[32];
   quic::QuicDataWriter writer(sizeof(buffer), buffer);
@@ -1757,4 +1769,53 @@
             "Integer overflow when parsing object ID");
 }
 
+TEST_F(MoqtDataParserStateMachineTest, SubgroupHasFirstObjectTrue) {
+  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(
+      0, 1, /*no_extension_headers=*/true, /*default_priority=*/false,
+      /*has_first_object=*/true);
+  stream_.Receive(StreamHeaderSubgroupMessage(type).PacketSample());
+  stream_.Receive(StreamMiddlerSubgroupMessage(type).PacketSample(),
+                  /*fin=*/true);
+  parser_.ReadAtMostOneObject();
+  ASSERT_EQ(visitor_.messages_received(), 1);
+  ASSERT_TRUE(visitor_.last_message().has_value());
+  EXPECT_EQ(visitor_.last_message()->first_object_in_subgroup, true);
+  parser_.ReadAtMostOneObject();
+  ASSERT_EQ(visitor_.messages_received(), 2);
+  ASSERT_TRUE(visitor_.last_message().has_value());
+  EXPECT_EQ(visitor_.last_message()->first_object_in_subgroup, false);
+  EXPECT_EQ(visitor_.parsing_error(), std::nullopt);
+  EXPECT_TRUE(visitor_.fin_received());
+}
+
+TEST_F(MoqtDataParserStateMachineTest, SubgroupHasFirstObjectFalse) {
+  MoqtDataStreamType type = MoqtDataStreamType::Subgroup(
+      0, 1, /*no_extension_headers=*/true, /*default_priority=*/false,
+      /*has_first_object=*/false);
+  stream_.Receive(StreamHeaderSubgroupMessage(type).PacketSample());
+  stream_.Receive(StreamMiddlerSubgroupMessage(type).PacketSample(),
+                  /*fin=*/true);
+  parser_.ReadAtMostOneObject();
+  ASSERT_EQ(visitor_.messages_received(), 1);
+  ASSERT_TRUE(visitor_.last_message().has_value());
+  EXPECT_EQ(visitor_.last_message()->first_object_in_subgroup, false);
+  parser_.ReadAtMostOneObject();
+  ASSERT_EQ(visitor_.messages_received(), 2);
+  ASSERT_TRUE(visitor_.last_message().has_value());
+  EXPECT_EQ(visitor_.last_message()->first_object_in_subgroup, false);
+  EXPECT_EQ(visitor_.parsing_error(), std::nullopt);
+  EXPECT_TRUE(visitor_.fin_received());
+}
+
+TEST_F(MoqtDataParserStateMachineTest, FetchFirstObjectMissing) {
+  StreamHeaderFetchMessage header;
+  stream_.Receive(header.PacketSample());
+  parser_.ReadStreamType();
+  ASSERT_EQ(visitor_.messages_received(), 0);
+  parser_.ReadAtMostOneObject();
+  ASSERT_EQ(visitor_.messages_received(), 1);
+  ASSERT_TRUE(visitor_.last_message().has_value());
+  EXPECT_FALSE(visitor_.last_message()->first_object_in_subgroup.has_value());
+}
+
 }  // namespace moqt::test
diff --git a/quiche/quic/moqt/moqt_relay_track_publisher_test.cc b/quiche/quic/moqt/moqt_relay_track_publisher_test.cc
index 32ba149..e12227d 100644
--- a/quiche/quic/moqt/moqt_relay_track_publisher_test.cc
+++ b/quiche/quic/moqt/moqt_relay_track_publisher_test.cc
@@ -83,7 +83,7 @@
     publisher_.OnObjectFragment(
         kTrackName,
         PublishedObjectMetadata{location, subgroup, "", status, 128,
-                                payload.length()},
+                                location.object == 0, payload.length()},
         payload, /*offset=*/0);
     std::optional<PublishedObject> object =
         publisher_.GetCachedObject(location.group, subgroup, location.object);
@@ -173,7 +173,7 @@
     publisher_.OnObjectFragment(
         kTrackName,
         PublishedObjectMetadata{Location(group, 0), 0, "",
-                                MoqtObjectStatus::kEndOfGroup, 128, 0},
+                                MoqtObjectStatus::kEndOfGroup, 128, true, 0},
         "", /*offset=*/0);
   }
 }
@@ -189,7 +189,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 0, "", MoqtObjectStatus::kNormal, 128,
-                              6},
+                              location.object == 0, 6},
       "object", /*offset=*/0);
   EXPECT_TRUE(track_deleted_);
 }
@@ -205,7 +205,8 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{first_location, 0, "",
-                              MoqtObjectStatus::kEndOfTrack, 128, 0},
+                              MoqtObjectStatus::kEndOfTrack, 128,
+                              first_location.object == 0, 0},
       "", /*offset=*/0);
   EXPECT_TRUE(track_deleted_);
 }
@@ -221,7 +222,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 1, "", MoqtObjectStatus::kEndOfGroup,
-                              128, 6},
+                              128, location.object == 0, 6},
       "object", /*offset=*/0);
   EXPECT_TRUE(track_deleted_);
 }
@@ -237,7 +238,8 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{first_location, 1, "",
-                              MoqtObjectStatus::kEndOfGroup, 128, 0},
+                              MoqtObjectStatus::kEndOfGroup, 128,
+                              first_location.object == 0, 0},
       "", /*offset=*/0);
   EXPECT_TRUE(track_deleted_);
 }
@@ -253,7 +255,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 0, "", MoqtObjectStatus::kNormal, 200,
-                              6},
+                              location.object == 0, 6},
       "object", /*offset=*/0);
   EXPECT_TRUE(track_deleted_);
 }
@@ -271,7 +273,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 0, "", MoqtObjectStatus::kNormal, 128,
-                              6},
+                              location.object == 0, 6},
       "object", /*offset=*/0);
   EXPECT_TRUE(track_deleted_);
 }
@@ -287,7 +289,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{first_location, 0, "", MoqtObjectStatus::kNormal,
-                              128, 6},
+                              128, first_location.object == 0, 6},
       "object", /*offset=*/0);
   // Object is simply ignored; track is not malformed.
   EXPECT_FALSE(track_deleted_);
@@ -369,7 +371,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 0, "foo", MoqtObjectStatus::kNormal,
-                              128, 6},
+                              128, location.object == 0, 6},
       "object", /*offset=*/0);
   // Exact duplicate is ignored. It doesn't matter that the arrival time
   // changed.
@@ -379,7 +381,8 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 0, "foo", MoqtObjectStatus::kNormal,
-                              128, 6, quic::QuicTime::Infinite()},
+                              128, location.object == 0, 6,
+                              quic::QuicTime::Infinite()},
       "object", /*offset=*/0);
 }
 
@@ -392,7 +395,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 0, "foo", MoqtObjectStatus::kNormal,
-                              128, 6},
+                              128, location.object == 0, 6},
       "object", /*offset=*/0);
   // Priority change; malformed track.
   EXPECT_CALL(listener_, OnNewObjectAvailable).Times(0);
@@ -400,7 +403,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 0, "foo", MoqtObjectStatus::kNormal, 64,
-                              6},
+                              location.object == 0, 6},
       "object", /*offset=*/0);
   EXPECT_TRUE(track_deleted_);
 }
@@ -414,7 +417,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 0, "foo", MoqtObjectStatus::kNormal,
-                              128, 7},
+                              128, location.object == 0, 7},
       "payload", /*offset=*/0);
   // Payload change; malformed track.
   EXPECT_CALL(listener_, OnNewObjectAvailable).Times(0);
@@ -422,7 +425,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, 0, "foo", MoqtObjectStatus::kNormal,
-                              128, 6},
+                              128, location.object == 0, 6},
       "foobar", /*offset=*/0);
   EXPECT_TRUE(track_deleted_);
 }
@@ -469,7 +472,7 @@
   publisher_.OnObjectFragment(
       kTrackName,
       PublishedObjectMetadata{location, std::nullopt, "",
-                              MoqtObjectStatus::kNormal, 128, 6},
+                              MoqtObjectStatus::kNormal, 128, std::nullopt, 6},
       "object", /*offset=*/0);
   std::optional<PublishedObject> object =
       publisher_.GetCachedObject(location.group, std::nullopt, 0);
@@ -481,8 +484,10 @@
   Location location = kLargestLocation.Next();
   uint64_t subgroup = 0;
   // Total size is 15 bytes.
-  PublishedObjectMetadata metadata = {
-      location, subgroup, "", MoqtObjectStatus::kNormal, 128, 15};
+  PublishedObjectMetadata metadata = {location, subgroup,
+                                      "",       MoqtObjectStatus::kNormal,
+                                      128,      location.object == 0,
+                                      15};
 
   // Fragment 1 arrives.
   EXPECT_CALL(listener_,
@@ -524,7 +529,8 @@
   SubscribeAndOk();
   Location location = kLargestLocation.Next();
   PublishedObjectMetadata metadata = {
-      location, std::nullopt, "", MoqtObjectStatus::kNormal, 128, 10};
+      location, std::nullopt, "", MoqtObjectStatus::kNormal,
+      128,      std::nullopt, 10};
   // Fragment length mismatch.
   EXPECT_QUICHE_BUG(
       publisher_.OnObjectFragment(kTrackName, metadata, "short", 0),
@@ -540,8 +546,10 @@
   Location location = kLargestLocation.Next();
   uint64_t subgroup = 0;
   // Total size is 15 bytes.
-  PublishedObjectMetadata metadata = {
-      location, subgroup, "", MoqtObjectStatus::kNormal, 128, 15};
+  PublishedObjectMetadata metadata = {location, subgroup,
+                                      "",       MoqtObjectStatus::kNormal,
+                                      128,      location.object == 0,
+                                      15};
 
   // Fragment 1 arrives (first 10 bytes).
   EXPECT_CALL(listener_,
diff --git a/quiche/quic/moqt/moqt_session_test.cc b/quiche/quic/moqt/moqt_session_test.cc
index 6ddd7f8..15eb900 100644
--- a/quiche/quic/moqt/moqt_session_test.cc
+++ b/quiche/quic/moqt/moqt_session_test.cc
@@ -70,7 +70,7 @@
 constexpr uint64_t kDefaultLocalRequestId = 0;
 constexpr uint64_t kDefaultPeerRequestId = 1;
 const MoqtDataStreamType kDefaultSubgroupStreamType =
-    MoqtDataStreamType::Subgroup(2, 4, false, false);
+    MoqtDataStreamType::Subgroup(2, 4, false, false, true);
 constexpr MoqtPriority kDefaultPublisherPriority = 0x80;
 const TrackExtensions kNoExtensions;
 
@@ -208,8 +208,9 @@
     }
     quiche::QuicheBuffer buffer = framer.SerializeObjectHeader(
         object,
-        MoqtDataStreamType::Subgroup(*object.subgroup_id, object.object_id,
-                                     false, false),
+        MoqtDataStreamType::Subgroup(
+            *object.subgroup_id, object.object_id, false, false,
+            object.first_object_in_subgroup.value_or(true)),
         previous_object);
     size_t data_read = 0;
     if (visitor == nullptr) {  // It's the first object in the stream
@@ -1222,6 +1223,7 @@
       /*extension_headers=*/"",
       /*object_status=*/MoqtObjectStatus::kNormal,
       /*subgroup_id=*/std::nullopt,
+      /*first_object_in_subgroup=*/std::nullopt,
       /*payload_length=*/8,
   };
   char datagram[] = {0x00, 0x02, 0x00, 0x00, 0x00, 0x64, 0x65,
@@ -1326,7 +1328,7 @@
       .WillOnce(Return(PublishedObject{
           PublishedObjectMetadata{
               Location(0, 0), 0, "", MoqtObjectStatus::kNormal,
-              kLocalDefaultPriority, 8, MoqtSessionPeer::Now(&session_)},
+              kLocalDefaultPriority, true, 8, MoqtSessionPeer::Now(&session_)},
           PayloadFromString("deadbeef")}))
       .WillOnce(Return(std::nullopt));
   EXPECT_CALL(mock_stream_, Writev)
@@ -1341,9 +1343,10 @@
   // Send a datagram with the default priority.
   EXPECT_CALL(*track, GetCachedObject(_, _, _, _))
       .WillOnce(Return(PublishedObject{
-          PublishedObjectMetadata{
-              Location(0, 1), std::nullopt, "", MoqtObjectStatus::kNormal,
-              kLocalDefaultPriority, 8, MoqtSessionPeer::Now(&session_)},
+          PublishedObjectMetadata{Location(0, 1), std::nullopt, "",
+                                  MoqtObjectStatus::kNormal,
+                                  kLocalDefaultPriority, std::nullopt, 8,
+                                  MoqtSessionPeer::Now(&session_)},
           PayloadFromString("deadbeef")}));
   EXPECT_CALL(mock_session_, SendOrQueueDatagram)
       .WillOnce([](absl::string_view datagram) {
@@ -1357,9 +1360,10 @@
   // Non-default priority
   EXPECT_CALL(*track, GetCachedObject(_, _, _, _))
       .WillOnce(Return(PublishedObject{
-          PublishedObjectMetadata{
-              Location(0, 2), std::nullopt, "", MoqtObjectStatus::kNormal,
-              kLocalDefaultPriority + 1, 8, MoqtSessionPeer::Now(&session_)},
+          PublishedObjectMetadata{Location(0, 2), std::nullopt, "",
+                                  MoqtObjectStatus::kNormal,
+                                  kLocalDefaultPriority + 1, std::nullopt, 8,
+                                  MoqtSessionPeer::Now(&session_)},
           PayloadFromString("deadbeef")}));
   EXPECT_CALL(mock_session_, SendOrQueueDatagram)
       .WillOnce([](absl::string_view datagram) {
@@ -1610,7 +1614,7 @@
   // Trigger stream opening (calls SetObjectAvailableCallback with lambda1).
   // Setting the stream visitor will cause a second call to the callback.
   PublishedObjectMetadata metadata = {
-      Location(0, 0), 0, "", MoqtObjectStatus::kNormal, 128, 10};
+      Location(0, 0), 0, "", MoqtObjectStatus::kNormal, 128, true, 10};
   EXPECT_CALL(*fetch_task, GetNextObject)
       .WillOnce([&](PublishedObject& output) {
         output.metadata = metadata;
@@ -1894,6 +1898,7 @@
       /*extension_headers=*/"",
       /*status=*/MoqtObjectStatus::kNormal,
       /*subgroup=*/0,
+      /*first_object_in_subgroup=*/true,
       /*payload_length=*/3,
   };
   MoqtFramer framer(true, quic::Perspective::IS_SERVER);
@@ -2124,6 +2129,7 @@
       /*extension_headers=*/"",
       /*status=*/MoqtObjectStatus::kNormal,
       /*subgroup=*/0,
+      /*first_object_in_subgroup=*/true,
       /*payload_length=*/3,
   };
   MoqtFramer framer(true, quic::Perspective::IS_SERVER);
@@ -2197,6 +2203,7 @@
       /*extension_headers=*/"",
       /*status=*/MoqtObjectStatus::kNormal,
       /*subgroup=*/0,
+      /*first_object_in_subgroup=*/true,
       /*payload_length=*/3,
   };
   MoqtFramer framer(true, quic::Perspective::IS_SERVER);
@@ -2544,6 +2551,7 @@
       /*extension_headers=*/"",
       /*object_status=*/MoqtObjectStatus::kEndOfGroup,
       /*subgroup_id=*/0,
+      /*first_object_in_subgroup=*/true,
       /*payload_length=*/0,
   };
   EXPECT_CALL(mock_stream_, GetStreamId())
@@ -2588,6 +2596,7 @@
       /*extension_headers=*/"",
       /*object_status=*/MoqtObjectStatus::kEndOfGroup,
       /*subgroup_id=*/0,
+      /*first_object_in_subgroup=*/true,
       /*payload_length=*/0,
   };
   EXPECT_CALL(mock_stream_, GetStreamId())
@@ -2755,7 +2764,7 @@
   EXPECT_CALL(*track, GetCachedObject(0, Optional(1), 0, 0))
       .WillOnce(Return(PublishedObject{
           PublishedObjectMetadata{Location(0, 0), 1, "",
-                                  MoqtObjectStatus::kNormal, 0x80, 0,
+                                  MoqtObjectStatus::kNormal, 0x80, true, 0,
                                   MoqtSessionPeer::Now(&session_)},
           PayloadFromString(""), false}));
   EXPECT_CALL(*track, GetCachedObject(0, Optional(1), 1, 0))
diff --git a/quiche/quic/moqt/moqt_subscription_test.cc b/quiche/quic/moqt/moqt_subscription_test.cc
index 227b8cb..37e1da9 100644
--- a/quiche/quic/moqt/moqt_subscription_test.cc
+++ b/quiche/quic/moqt/moqt_subscription_test.cc
@@ -109,6 +109,9 @@
   object.metadata.status = MoqtObjectStatus::kNormal;
   object.metadata.publisher_priority = publisher_priority;
   object.metadata.extensions = "extensions";
+  object.metadata.first_object_in_subgroup =
+      subgroup.has_value() ? std::optional<bool>(location.object == 0)
+                           : std::nullopt;
   object.metadata.payload_length = 8;
   object.payload.push_back(quiche::QuicheMemSlice::Copy("deadbeef"));
   return object;
@@ -344,7 +347,7 @@
 TEST_F(SubscriptionPublisherTest, UpdatePriorityWithActiveStreams) {
   CreateStream(
       Location(1, 0), 0, 127,
-      {0x11, static_cast<uint8_t>(kTrackAlias), 0x01, 0x7f, 0x00, 0x0a});
+      {0x51, static_cast<uint8_t>(kTrackAlias), 0x01, 0x7f, 0x00, 0x0a});
   MessageParameters new_params;
   new_params.subscriber_priority = 20;
   EXPECT_CALL(mock_uni_stream_, SetPriority);
diff --git a/quiche/quic/moqt/moqt_track_test.cc b/quiche/quic/moqt/moqt_track_test.cc
index 010157d..9e15a7f 100644
--- a/quiche/quic/moqt/moqt_track_test.cc
+++ b/quiche/quic/moqt/moqt_track_test.cc
@@ -306,7 +306,8 @@
   PublishedObject object;
   EXPECT_EQ(fetch_task_->GetNextObject(object),
             MoqtFetchTask::GetNextObjectResult::kPending);
-  MoqtObject new_object = {1, 3, 0, 128, "", MoqtObjectStatus::kNormal, 0, 6};
+  MoqtObject new_object = {1, 3,    0, 128, "", MoqtObjectStatus::kNormal,
+                           0, true, 6};
   bool got_object = false;
   fetch_task_->SetObjectAvailableCallback([&]() {
     got_object = true;
@@ -341,7 +342,8 @@
 
 TEST_F(UpstreamFetchTest, ObjectRetrievalEmptyPayload) {
   fetch_.OnFetchResult(Location(3, 50), absl::OkStatus(), nullptr);
-  MoqtObject moqt_obj = {1, 3, 0, 128, "", MoqtObjectStatus::kEndOfGroup, 0, 0};
+  MoqtObject moqt_obj = {1, 3,    0, 128, "", MoqtObjectStatus::kEndOfGroup,
+                         0, true, 0};
   fetch_.task()->NewObject(moqt_obj);
   fetch_.task()->NotifyNewObject();
   fetch_.OnStreamOpened([]() {});
@@ -370,7 +372,7 @@
   fetch_.OnFetchResult(largest, absl::OkStatus(), nullptr);
   fetch_.OnStreamOpened([]() {});
 
-  MoqtObject obj1 = {1, 3, 49, 128, "", MoqtObjectStatus::kNormal, 0, 1};
+  MoqtObject obj1 = {1, 3, 49, 128, "", MoqtObjectStatus::kNormal, 0, false, 1};
   fetch_.task()->NewObject(obj1);
   fetch_.task()->AppendPayloadToObject("a");
   fetch_.task()->NotifyNewObject();
@@ -382,7 +384,7 @@
   EXPECT_EQ(fetch_task_->GetNextObject(out),
             MoqtFetchTask::GetNextObjectResult::kPending);
 
-  MoqtObject obj2 = {1, 3, 50, 128, "", MoqtObjectStatus::kNormal, 0, 1};
+  MoqtObject obj2 = {1, 3, 50, 128, "", MoqtObjectStatus::kNormal, 0, false, 1};
   fetch_.task()->NewObject(obj2);
   fetch_.task()->AppendPayloadToObject("b");
   fetch_.task()->NotifyNewObject();
diff --git a/quiche/quic/moqt/moqt_uni_stream.cc b/quiche/quic/moqt/moqt_uni_stream.cc
index 0f0456e..26ab6c2 100644
--- a/quiche/quic/moqt/moqt_uni_stream.cc
+++ b/quiche/quic/moqt/moqt_uni_stream.cc
@@ -29,6 +29,7 @@
 #include "quiche/quic/moqt/moqt_trace_recorder.h"
 #include "quiche/quic/moqt/moqt_track.h"
 #include "quiche/quic/moqt/moqt_types.h"
+#include "quiche/common/platform/api/quiche_bug_tracker.h"
 #include "quiche/common/quiche_buffer_allocator.h"
 #include "quiche/common/quiche_mem_slice.h"
 #include "quiche/common/quiche_weak_ptr.h"
@@ -149,6 +150,10 @@
           << "Received non-empty object with no payload";
       return;
     }
+    QUICHE_BUG_IF(OutgoingSubgroupStream_SendObjects_no_first_object,
+                  !object->metadata.first_object_in_subgroup.has_value())
+        << "first_object_in_subgroup has to be set on all objects set via "
+           "subscription";
     QUICHE_DCHECK_EQ(object->metadata.location.group, index_.group);
     QUICHE_DCHECK(object->metadata.subgroup == index_.subgroup);
     if (!visitor->InWindow(object->metadata.location)) {
@@ -175,7 +180,8 @@
       type_ = MoqtDataStreamType::Subgroup(
           index_.subgroup, next_object_, false,
           object->metadata.publisher_priority ==
-              publisher_->extensions().default_publisher_priority());
+              publisher_->extensions().default_publisher_priority(),
+          object->metadata.first_object_in_subgroup.value_or(true));
     }
     uint64_t start_offset = already_delivered_;
     already_delivered_ +=
@@ -446,6 +452,7 @@
       metadata.extensions = message.extension_headers;
       metadata.status = message.object_status;
       metadata.publisher_priority = message.publisher_priority;
+      metadata.first_object_in_subgroup = message.first_object_in_subgroup;
       metadata.payload_length = message.payload_length;
       metadata.arrival_time = clock_->Now();
       visitor_->OnObjectFragment(track->full_track_name(), metadata, payload,
diff --git a/quiche/quic/moqt/moqt_uni_stream_test.cc b/quiche/quic/moqt/moqt_uni_stream_test.cc
index 9b446ea..d69c198 100644
--- a/quiche/quic/moqt/moqt_uni_stream_test.cc
+++ b/quiche/quic/moqt/moqt_uni_stream_test.cc
@@ -51,6 +51,7 @@
   object.metadata.location = Location(0, 0);
   object.metadata.subgroup = 0;
   object.metadata.status = MoqtObjectStatus::kNormal;
+  object.metadata.first_object_in_subgroup = true;
   object.metadata.arrival_time = quic::QuicTime::Zero();
   object.metadata.payload_length = 7;
   object.payload.push_back(quiche::QuicheMemSlice::Copy("payload"));
@@ -463,8 +464,9 @@
     0x80,  // publisher_priority
     "",    // extension_headers
     MoqtObjectStatus::kNormal,
-    0,  // subgroup_id
-    0,  // payload_length
+    0,     // subgroup_id
+    true,  // first_object_in_subgroup
+    0,     // payload_length
 };
 
 class MockSessionToUniStreamInterface : public SessionToUniStreamInterface {
@@ -539,7 +541,7 @@
 }
 
 TEST_F(IncomingDataStreamTest, DestructorAfterObject) {
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   ProcessAlias(2);
   EXPECT_CALL(visitor_, OnObjectFragment);
   stream_->OnObjectMessage(kDefaultObject, "", true);
@@ -548,7 +550,7 @@
 }
 
 TEST_F(IncomingDataStreamTest, DestructorAfterFin) {
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   ProcessAlias(2);
   EXPECT_CALL(visitor_, OnObjectFragment);
   stream_->OnObjectMessage(kDefaultObject, "", true);
@@ -570,7 +572,7 @@
 }
 
 TEST_F(IncomingDataStreamTest, OnObjectMessage) {
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   ProcessAlias(2);
   MoqtObject object = kDefaultObject;
   object.payload_length = 8;
@@ -592,7 +594,7 @@
 }
 
 TEST_F(IncomingDataStreamTest, OnObjectMessageBufferPartialObject) {
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   ProcessAlias(2);
   MoqtObject object = kDefaultObject;
   object.payload_length = 6;
@@ -611,7 +613,7 @@
 
 TEST_F(IncomingDataStreamTest, OnObjectMessageDontBufferPartialObject) {
   EXPECT_CALL(session_, deliver_partial_objects()).WillRepeatedly(Return(true));
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   ProcessAlias(2);
   MoqtObject object = kDefaultObject;
   object.payload_length = 6;
@@ -673,7 +675,8 @@
   MoqtObject sent_object = MoqtObject(
       /*request_id=*/0, /*group_id=*/0,
       /*object_id=*/0, /*publisher_priority=*/0x80, /*extension_headers=*/"",
-      MoqtObjectStatus::kNormal, /*subgroup_id=*/0, /*payload_length=*/12);
+      MoqtObjectStatus::kNormal, /*subgroup_id=*/0,
+      /*first_object_in_subgroup=*/true, /*payload_length=*/12);
   stream_->OnObjectMessage(sent_object, "foo", false);
   task->NotifyNewObject();
   EXPECT_EQ(objects_available_callbacks, 1);
@@ -703,7 +706,7 @@
 }
 
 TEST_F(IncomingDataStreamTest, OnObjectMessageInvalidTrack) {
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   uint8_t alias = 2;
   mock_stream_.Receive(
       absl::string_view(reinterpret_cast<const char*>(&alias), 1), false);
@@ -714,7 +717,7 @@
 }
 
 TEST_F(IncomingDataStreamTest, OnObjectMessageNotInWindow) {
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   ProcessAlias(2);
   MessageParameters parameters;
   parameters.set_forward(false);
@@ -724,7 +727,7 @@
 }
 
 TEST_F(IncomingDataStreamTest, OnObjectMessageMissingSubgroupId) {
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   ProcessAlias(2);
   MoqtObject object = kDefaultObject;
   object.subgroup_id = std::nullopt;
@@ -733,7 +736,7 @@
 }
 
 TEST_F(IncomingDataStreamTest, ObjectAfterTrackEnd) {
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   ProcessAlias(2);
   MoqtObject object = kDefaultObject;
   object.object_status = MoqtObjectStatus::kEndOfTrack;
@@ -748,7 +751,7 @@
 }
 
 TEST_F(IncomingDataStreamTest, ObjectAfterGroupEnd) {
-  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80));
+  ProcessStreamType(MoqtDataStreamType::Subgroup(0, 0, false, 0x80, true));
   ProcessAlias(2);
   MoqtObject object = kDefaultObject;
   object.object_status = MoqtObjectStatus::kEndOfGroup;
diff --git a/quiche/quic/moqt/test_tools/moqt_mock_visitor.h b/quiche/quic/moqt/test_tools/moqt_mock_visitor.h
index d106fb2..5915dfc 100644
--- a/quiche/quic/moqt/test_tools/moqt_mock_visitor.h
+++ b/quiche/quic/moqt/test_tools/moqt_mock_visitor.h
@@ -155,6 +155,7 @@
     metadata.extensions = "";
     metadata.status = MoqtObjectStatus::kNormal;
     metadata.publisher_priority = 128;
+    metadata.first_object_in_subgroup = location.object == 0;
     metadata.payload_length = payload.length();
     metadata.arrival_time = arrival_time;
     auto it = objects_.find(location);
diff --git a/quiche/quic/moqt/test_tools/moqt_test_message.h b/quiche/quic/moqt/test_tools/moqt_test_message.h
index a19cc8a..4a01ac2 100644
--- a/quiche/quic/moqt/test_tools/moqt_test_message.h
+++ b/quiche/quic/moqt/test_tools/moqt_test_message.h
@@ -71,15 +71,18 @@
 
 inline std::vector<MoqtDataStreamType> AllMoqtDataStreamTypes() {
   std::vector<MoqtDataStreamType> types;
+  types.reserve(256);
   types.push_back(MoqtDataStreamType::Fetch());
   uint64_t first_object_id = 1;
   for (uint64_t subgroup_id : {0, 1, 2}) {
     for (bool no_extension_headers : {true, false}) {
       for (bool default_priority : {true, false}) {
-        for (bool end_of_group : {false, true}) {
-          types.push_back(MoqtDataStreamType::Subgroup(
-              subgroup_id, first_object_id, no_extension_headers,
-              default_priority, end_of_group));
+        for (bool has_first_object : {true, false}) {
+          for (bool end_of_group : {false, true}) {
+            types.push_back(MoqtDataStreamType::Subgroup(
+                subgroup_id, first_object_id, no_extension_headers,
+                default_priority, has_first_object, end_of_group));
+          }
         }
       }
     }
@@ -275,15 +278,16 @@
   }
 
  protected:
-  MoqtObject object_ = {
-      /*track_alias=*/4,
-      /*group_id*/ 5,
-      /*object_id=*/6,
-      /*publisher_priority=*/7,
-      std::string(kDefaultExtensionBlob),
-      /*object_status=*/MoqtObjectStatus::kNormal,
-      /*subgroup_id=*/8,
-      /*payload_length=*/3,
+  MoqtObject object_{
+      .track_alias = 4,
+      .group_id = 5,
+      .object_id = 6,
+      .publisher_priority = 7,
+      .extension_headers = std::string(kDefaultExtensionBlob),
+      .object_status = MoqtObjectStatus::kNormal,
+      .subgroup_id = 8,
+      .first_object_in_subgroup = false,
+      .payload_length = 3,
   };
 };
 
@@ -891,7 +895,10 @@
 
  private:
   uint8_t raw_packet_[4] = {
-      0x0a, 0x00, 0x01, 0x03,  // request_id = 3
+      0x0a,
+      0x00,
+      0x01,
+      0x03,  // request_id = 3
   };
 
   MoqtUnsubscribe unsubscribe_ = {
@@ -1638,7 +1645,9 @@
 
  private:
   uint8_t raw_packet_[4] = {
-      0x17, 0x00, 0x01,
+      0x17,
+      0x00,
+      0x01,
       0x01,  // request_id = 1
   };
 
@@ -1669,7 +1678,9 @@
 
  private:
   uint8_t raw_packet_[4] = {
-      0x1a, 0x00, 0x01,
+      0x1a,
+      0x00,
+      0x01,
       0x0b,  // max_request_id = 11
   };