diff --git a/quic/core/quic_dispatcher_test.cc b/quic/core/quic_dispatcher_test.cc
index 517b892..188707b 100644
--- a/quic/core/quic_dispatcher_test.cc
+++ b/quic/core/quic_dispatcher_test.cc
@@ -877,6 +877,7 @@
   static_assert(QUIC_ARRAYSIZE(kSupportedTransportVersions) == 5u,
                 "Supported versions out of sync");
   SetQuicReloadableFlag(quic_disable_version_39, false);
+  SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, true);
   SetQuicReloadableFlag(quic_enable_version_99, true);
   QuicSocketAddress client_address(QuicIpAddress::Loopback4(), 1);
@@ -961,6 +962,39 @@
                 SerializeCHLO(), CONNECTION_ID_PRESENT,
                 PACKET_4BYTE_PACKET_NUMBER, 1);
 
+  // Turn off version 46.
+  SetQuicReloadableFlag(quic_enable_version_46, false);
+  connection_id = TestConnectionId(++conn_id);
+  EXPECT_CALL(*dispatcher_, CreateQuicSession(connection_id, client_address,
+                                              QuicStringPiece("hq"), _))
+      .Times(0);
+  ProcessPacket(client_address, connection_id, true,
+                ParsedQuicVersion(PROTOCOL_QUIC_CRYPTO, QUIC_VERSION_46),
+                SerializeCHLO(), CONNECTION_ID_PRESENT,
+                PACKET_4BYTE_PACKET_NUMBER, 1);
+
+  // Turn on version 46.
+  SetQuicReloadableFlag(quic_enable_version_46, true);
+  connection_id = TestConnectionId(++conn_id);
+  EXPECT_CALL(*dispatcher_, CreateQuicSession(connection_id, client_address,
+                                              QuicStringPiece("hq"), _))
+      .WillOnce(testing::Return(CreateSession(
+          dispatcher_.get(), config_, connection_id, client_address,
+          &mock_helper_, &mock_alarm_factory_, &crypto_config_,
+          QuicDispatcherPeer::GetCache(dispatcher_.get()), &session1_)));
+  EXPECT_CALL(*reinterpret_cast<MockQuicConnection*>(session1_->connection()),
+              ProcessUdpPacket(_, _, _))
+      .WillOnce(WithArg<2>(
+          Invoke([this, connection_id](const QuicEncryptedPacket& packet) {
+            ValidatePacket(connection_id, packet);
+          })));
+  EXPECT_CALL(*dispatcher_,
+              ShouldCreateOrBufferPacketForConnection(connection_id, _));
+  ProcessPacket(client_address, connection_id, true,
+                ParsedQuicVersion(PROTOCOL_QUIC_CRYPTO, QUIC_VERSION_46),
+                SerializeCHLO(), CONNECTION_ID_PRESENT,
+                PACKET_4BYTE_PACKET_NUMBER, 1);
+
   // Turn off version 39.
   SetQuicReloadableFlag(quic_disable_version_39, true);
   connection_id = TestConnectionId(++conn_id);
diff --git a/quic/core/quic_version_manager.cc b/quic/core/quic_version_manager.cc
index 045e38c..cde3664 100644
--- a/quic/core/quic_version_manager.cc
+++ b/quic/core/quic_version_manager.cc
@@ -16,6 +16,7 @@
     ParsedQuicVersionVector supported_versions)
     : enable_version_99_(GetQuicReloadableFlag(quic_enable_version_99)),
       enable_version_47_(GetQuicReloadableFlag(quic_enable_version_47)),
+      enable_version_46_(GetQuicReloadableFlag(quic_enable_version_46)),
       disable_version_39_(GetQuicReloadableFlag(quic_disable_version_39)),
       enable_tls_(GetQuicFlag(FLAGS_quic_supports_tls_handshake)),
       allowed_supported_versions_(std::move(supported_versions)) {
@@ -38,10 +39,12 @@
 void QuicVersionManager::MaybeRefilterSupportedVersions() {
   if (enable_version_99_ != GetQuicReloadableFlag(quic_enable_version_99) ||
       enable_version_47_ != GetQuicReloadableFlag(quic_enable_version_47) ||
+      enable_version_46_ != GetQuicReloadableFlag(quic_enable_version_46) ||
       disable_version_39_ != GetQuicReloadableFlag(quic_disable_version_39) ||
       enable_tls_ != GetQuicFlag(FLAGS_quic_supports_tls_handshake)) {
     enable_version_99_ = GetQuicReloadableFlag(quic_enable_version_99);
     enable_version_47_ = GetQuicReloadableFlag(quic_enable_version_47);
+    enable_version_46_ = GetQuicReloadableFlag(quic_enable_version_46);
     disable_version_39_ = GetQuicReloadableFlag(quic_disable_version_39);
     enable_tls_ = GetQuicFlag(FLAGS_quic_supports_tls_handshake);
     RefilterSupportedVersions();
diff --git a/quic/core/quic_version_manager.h b/quic/core/quic_version_manager.h
index 71a285a..a865be6 100644
--- a/quic/core/quic_version_manager.h
+++ b/quic/core/quic_version_manager.h
@@ -42,6 +42,8 @@
   bool enable_version_99_;
   // quic_enable_version_47 flag
   bool enable_version_47_;
+  // quic_enable_version_46 flag
+  bool enable_version_46_;
   // quic_disable_version_39 flag
   bool disable_version_39_;
   // quic_supports_tls_handshake flag
diff --git a/quic/core/quic_version_manager_test.cc b/quic/core/quic_version_manager_test.cc
index 4e4b3f4..de5af3b 100644
--- a/quic/core/quic_version_manager_test.cc
+++ b/quic/core/quic_version_manager_test.cc
@@ -20,16 +20,21 @@
                 "Supported versions out of sync");
   SetQuicReloadableFlag(quic_enable_version_99, false);
   SetQuicReloadableFlag(quic_enable_version_47, false);
+  SetQuicReloadableFlag(quic_enable_version_46, false);
   SetQuicReloadableFlag(quic_disable_version_39, true);
   QuicVersionManager manager(AllSupportedVersions());
 
   EXPECT_EQ(FilterSupportedTransportVersions(AllSupportedTransportVersions()),
             manager.GetSupportedTransportVersions());
 
-  EXPECT_EQ(QuicTransportVersionVector({QUIC_VERSION_46, QUIC_VERSION_43}),
+  EXPECT_EQ(QuicTransportVersionVector({QUIC_VERSION_43}),
             manager.GetSupportedTransportVersions());
 
   SetQuicReloadableFlag(quic_disable_version_39, false);
+  EXPECT_EQ(QuicTransportVersionVector({QUIC_VERSION_43, QUIC_VERSION_39}),
+            manager.GetSupportedTransportVersions());
+
+  SetQuicReloadableFlag(quic_enable_version_46, true);
   EXPECT_EQ(QuicTransportVersionVector(
                 {QUIC_VERSION_46, QUIC_VERSION_43, QUIC_VERSION_39}),
             manager.GetSupportedTransportVersions());
diff --git a/quic/core/quic_versions.cc b/quic/core/quic_versions.cc
index 960a046..d540def 100644
--- a/quic/core/quic_versions.cc
+++ b/quic/core/quic_versions.cc
@@ -228,11 +228,17 @@
     }
     if (version.transport_version == QUIC_VERSION_99) {
       if (GetQuicReloadableFlag(quic_enable_version_99) &&
-          GetQuicReloadableFlag(quic_enable_version_47)) {
+          GetQuicReloadableFlag(quic_enable_version_47) &&
+          GetQuicReloadableFlag(quic_enable_version_46)) {
         filtered_versions.push_back(version);
       }
     } else if (version.transport_version == QUIC_VERSION_47) {
-      if (GetQuicReloadableFlag(quic_enable_version_47)) {
+      if (GetQuicReloadableFlag(quic_enable_version_47) &&
+          GetQuicReloadableFlag(quic_enable_version_46)) {
+        filtered_versions.push_back(version);
+      }
+    } else if (version.transport_version == QUIC_VERSION_46) {
+      if (GetQuicReloadableFlag(quic_enable_version_46)) {
         filtered_versions.push_back(version);
       }
     } else if (version.transport_version == QUIC_VERSION_39) {
@@ -439,6 +445,9 @@
   if (parsed_version.transport_version >= QUIC_VERSION_47) {
     SetQuicReloadableFlag(quic_enable_version_47, true);
   }
+  if (parsed_version.transport_version >= QUIC_VERSION_46) {
+    SetQuicReloadableFlag(quic_enable_version_46, true);
+  }
 }
 
 #undef RETURN_STRING_LITERAL  // undef for jumbo builds
diff --git a/quic/core/quic_versions_test.cc b/quic/core/quic_versions_test.cc
index 0dbc72b..0b719d5 100644
--- a/quic/core/quic_versions_test.cc
+++ b/quic/core/quic_versions_test.cc
@@ -268,6 +268,7 @@
 TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsAllVersions) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
   SetQuicReloadableFlag(quic_disable_version_39, false);
+  SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, true);
   SetQuicReloadableFlag(quic_enable_version_99, true);
   ParsedQuicVersionVector parsed_versions;
@@ -290,6 +291,7 @@
 TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo99) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
   SetQuicReloadableFlag(quic_disable_version_39, false);
+  SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, true);
   SetQuicReloadableFlag(quic_enable_version_99, false);
   ParsedQuicVersionVector parsed_versions;
@@ -311,6 +313,7 @@
 TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo47) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
   SetQuicReloadableFlag(quic_disable_version_39, false);
+  SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, false);
   SetQuicReloadableFlag(quic_enable_version_99, false);
   ParsedQuicVersionVector parsed_versions;
@@ -329,17 +332,39 @@
   ASSERT_EQ(expected_parsed_versions, FilterSupportedVersions(parsed_versions));
 }
 
-TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo39) {
+TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo46) {
   QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
-  SetQuicReloadableFlag(quic_disable_version_39, true);
+  SetQuicReloadableFlag(quic_disable_version_39, false);
+  SetQuicReloadableFlag(quic_enable_version_46, false);
   SetQuicReloadableFlag(quic_enable_version_47, false);
   SetQuicReloadableFlag(quic_enable_version_99, false);
   ParsedQuicVersionVector parsed_versions;
   for (QuicTransportVersion version : all_versions) {
     parsed_versions.push_back(ParsedQuicVersion(PROTOCOL_QUIC_CRYPTO, version));
   }
-  QuicTransportVersionVector expected_versions = {QUIC_VERSION_46,
-                                                  QUIC_VERSION_43};
+  QuicTransportVersionVector expected_versions = {QUIC_VERSION_43,
+                                                  QUIC_VERSION_39};
+  ParsedQuicVersionVector expected_parsed_versions;
+  for (QuicTransportVersion version : expected_versions) {
+    expected_parsed_versions.push_back(
+        ParsedQuicVersion(PROTOCOL_QUIC_CRYPTO, version));
+  }
+
+  ASSERT_EQ(expected_versions, FilterSupportedTransportVersions(all_versions));
+  ASSERT_EQ(expected_parsed_versions, FilterSupportedVersions(parsed_versions));
+}
+
+TEST_F(QuicVersionsTest, FilterSupportedTransportVersionsNo39) {
+  QuicTransportVersionVector all_versions = AllSupportedTransportVersions();
+  SetQuicReloadableFlag(quic_disable_version_39, true);
+  SetQuicReloadableFlag(quic_enable_version_46, false);
+  SetQuicReloadableFlag(quic_enable_version_47, false);
+  SetQuicReloadableFlag(quic_enable_version_99, false);
+  ParsedQuicVersionVector parsed_versions;
+  for (QuicTransportVersion version : all_versions) {
+    parsed_versions.push_back(ParsedQuicVersion(PROTOCOL_QUIC_CRYPTO, version));
+  }
+  QuicTransportVersionVector expected_versions = {QUIC_VERSION_43};
   ParsedQuicVersionVector expected_parsed_versions;
   for (QuicTransportVersion version : expected_versions) {
     expected_parsed_versions.push_back(
@@ -446,6 +471,7 @@
       ParsedQuicVersion(PROTOCOL_TLS1_3, QUIC_VERSION_99);
   SetQuicFlag(FLAGS_quic_supports_tls_handshake, false);
   SetQuicReloadableFlag(quic_disable_version_39, false);
+  SetQuicReloadableFlag(quic_enable_version_46, true);
   SetQuicReloadableFlag(quic_enable_version_47, false);
   SetQuicReloadableFlag(quic_enable_version_99, false);
 
diff --git a/quic/quartc/quartc_endpoint_test.cc b/quic/quartc/quartc_endpoint_test.cc
index 6b56b1a..5f8c25d 100644
--- a/quic/quartc/quartc_endpoint_test.cc
+++ b/quic/quartc/quartc_endpoint_test.cc
@@ -80,6 +80,11 @@
 // attempts to connect using a newer version.
 TEST_F(QuartcEndpointTest,
        QUIC_TEST_DISABLED_IN_CHROME(ServerNegotiatesForOldVersion)) {
+  // Note: for this test, we need support for two versions.  Which two shouldn't
+  // matter, but they must be enabled so that the version manager doesn't filter
+  // them out.
+  SetQuicReloadableFlag(quic_enable_version_46, true);
+
   // Reset the client endpoint to prefer version 46 but also be capable of
   // speaking version 43.
   ParsedQuicVersionVector client_versions;
@@ -121,6 +126,11 @@
 // QUIC versions.
 TEST_F(QuartcEndpointTest,
        QUIC_TEST_DISABLED_IN_CHROME(ServerAcceptsOldVersion)) {
+  // Note: for this test, we need support for two versions.  Which two shouldn't
+  // matter, but they must be enabled so that the version manager doesn't filter
+  // them out.
+  SetQuicReloadableFlag(quic_enable_version_46, true);
+
   // Reset the client endpoint to only speak version 43.
   ParsedQuicVersionVector client_versions;
   client_versions.push_back({PROTOCOL_QUIC_CRYPTO, QUIC_VERSION_43});
@@ -162,6 +172,11 @@
 // completely disjoint sets of versions.
 TEST_F(QuartcEndpointTest,
        QUIC_TEST_DISABLED_IN_CHROME(VersionNegotiationWithDisjointVersions)) {
+  // Note: for this test, we need support for two versions.  Which two shouldn't
+  // matter, but they must be enabled so that the version manager doesn't filter
+  // them out.
+  SetQuicReloadableFlag(quic_enable_version_46, true);
+
   // Reset the client endpoint to only speak version 43.
   ParsedQuicVersionVector client_versions;
   client_versions.push_back({PROTOCOL_QUIC_CRYPTO, QUIC_VERSION_43});
@@ -204,6 +219,11 @@
   // version negotiation fails.
   SetQuicReloadableFlag(quic_no_client_conn_ver_negotiation, true);
 
+  // Note: for this test, we need support for two versions.  Which two shouldn't
+  // matter, but they must be enabled so that the version manager doesn't filter
+  // them out.
+  SetQuicReloadableFlag(quic_enable_version_46, true);
+
   // Reset the client endpoint to prefer version 46 but also be capable of
   // speaking version 43.
   ParsedQuicVersionVector client_versions;
diff --git a/quic/quartc/quartc_factory.cc b/quic/quartc/quartc_factory.cc
index 4e86fed..b75244c 100644
--- a/quic/quartc/quartc_factory.cc
+++ b/quic/quartc/quartc_factory.cc
@@ -62,6 +62,9 @@
   // Fix b/110259444.
   SetQuicReloadableFlag(quic_fix_spurious_ack_alarm, true);
 
+  // Enable version 46 to enable SendMessage API and 'quic bit' per draft 17.
+  SetQuicReloadableFlag(quic_enable_version_46, true);
+
   // Enable version 47 to enable variable-length connection ids.
   SetQuicReloadableFlag(quic_enable_version_47, true);
 
@@ -96,6 +99,12 @@
   // settings doesn't seem preferable.
   ConfigureGlobalQuicSettings();
 
+  // In exoblaze this may return false. DCHECK to avoid problems caused by
+  // incorrect flags configuration.
+  DCHECK(GetQuicReloadableFlag(quic_enable_version_46))
+      << "Your build does not support quic reloadable flags and shouldn't "
+         "place Quartc calls";
+
   QuicTagVector copt;
   copt.push_back(kNSTP);