diff --git a/backend/agent/src/MoShiro.Agent/AgentApp.cs b/backend/agent/src/MoShiro.Agent/AgentApp.cs
index d0e61d4..3290cb5 100644
--- a/backend/agent/src/MoShiro.Agent/AgentApp.cs
+++ b/backend/agent/src/MoShiro.Agent/AgentApp.cs
@@ -33,7 +33,7 @@ public sealed class AgentApp : IDisposable
     private readonly Outbox _outbox = new(64 << 20);
     private readonly RestartUpdater? _update;
     private readonly BackendUplink _uplink;
-    private readonly UdpMux _udp;
+    private readonly QuicDatagramTransport _datagrams;
     private readonly TcpAcceptor _tcp;
     private readonly PeerListener _peers;
     private readonly PeerHub _hub;
@@ -62,7 +62,7 @@ public sealed class AgentApp : IDisposable
 
         _ipv6Supported = bind.AddressFamily == System.Net.Sockets.AddressFamily.InterNetworkV6;
         _admission = new AgentAdmission(_streams);
-        _udp = new UdpMux(_sessions, _admission, _clock, _counters.Data, log, bind, config.Listen.UdpPorts);
+        _datagrams = new QuicDatagramTransport(_sessions, _admission, _clock, _counters.Data, log, bind, config.Listen.EffectiveQuicPorts, identity.Certificate);
         // 预握手敲门：控制端口和数据端口共用一个关卡（限速和去重一起算）；名册就是期望状态里的 peers
         _trust = TrustAnchor.Load(config.Fleet.IdentityDir, log);
         _knock = new KnockGate(identity.PeerIdentity, RosterKeys, time);
@@ -74,7 +74,7 @@ public sealed class AgentApp : IDisposable
             Clock = _clock,
             Log = log,
             Session = () => null, // 每个 Probe 会话各用自己绑定的环境（BlockEnv.WithSession）
-            Udp = _udp,
+            Datagrams = _datagrams,
             TcpListen = _tcp,
             Admission = _admission,
             Counters = _counters.Data,
@@ -83,14 +83,14 @@ public sealed class AgentApp : IDisposable
         };
         var chunks = new ChunkAssembler(_streams, _clock, _counters, _outbox, identity.NodeId, time, log);
         var targets = new TargetRunners(chunks, identity.NodeId, _clock, time, log);
-        _tasks = new TaskManager(CreateGuard, _streams, env, targets, () => _udp.BoundPorts, () => _tcp.BoundPorts, _trust);
+        _tasks = new TaskManager(CreateGuard, _streams, env, targets, () => _datagrams.BoundPorts, () => _tcp.BoundPorts, _trust);
         _hub = new PeerHub(_sessions, _clock, chunks, _tasks, _uplink, time, log);
-        _tests = new TestRunner(_tasks, _sessions, _streams, env, _uplink, config.Limits.MaxConcurrentTests, transport => transport == "udp" ? _udp.BoundPorts : _tcp.BoundPorts, time, log);
+        _tests = new TestRunner(_tasks, _sessions, _streams, env, _uplink, config.Limits.MaxConcurrentTests, transport => transport == "quic_datagram" ? _datagrams.BoundPorts : _tcp.BoundPorts, time, log);
 
         _tasks.OnLineTasksChanged = (probe, set) => _ = _hub.PushToAsync(probe, set).AsTask();
         _tasks.OnPeersChanged = _hub.CloseNotIn;
         _hub.OnProbeLost = probe => _tests.ProbeLost(probe);
-        _admission.OnEndpointChanged = probe => _ = _uplink.EmitEventAsync(AgentEventKinds.EndpointChanged, probe.UdpEndpoint?.ToString()).AsTask();
+        _admission.OnEndpointChanged = probe => _ = _uplink.EmitEventAsync(AgentEventKinds.EndpointChanged, probe.DatagramRemoteEndPoint?.ToString()).AsTask();
 
         _peers = new PeerListener(
             new PeerListenerOptions
@@ -113,13 +113,13 @@ public sealed class AgentApp : IDisposable
 
     public void Dispose()
     {
-        _udp.Dispose();
+        _datagrams.Dispose();
         _ownedRestart?.Dispose();
     }
 
     internal StreamRegistry Streams => _streams;
 
-    public IReadOnlyList<int> UdpPorts => _udp.BoundPorts;
+    public IReadOnlyList<int> QuicPorts => _datagrams.BoundPorts;
 
     public IReadOnlyList<int> TcpPorts => _tcp.BoundPorts;
 
@@ -146,23 +146,23 @@ public sealed class AgentApp : IDisposable
         _log.Info("moshiro agent starting", MoShiro.Protocol.BuildInfo.Fields);
         using CancellationTokenSource linked = CancellationTokenSource.CreateLinkedTokenSource(ct);
         // 数据面和控制端口先开始监听，再连接 Backend：hello 里上报的是实际端口
-        _udp.Bind();
+        _datagrams.Bind();
         _tcp.Bind();
-        Task udp = _udp.RunAsync(linked.Token);
+        Task quic = _datagrams.RunAsync(linked.Token);
         Task tcp = _tcp.RunAsync(linked.Token);
         Task peers = _peers.RunAsync(linked.Token);
         await Task.WhenAny(_peers.Started.Task, peers);
         if (peers.IsFaulted)
         {
             await linked.CancelAsync();
-            await Task.WhenAll(udp, tcp, peers); // 抛出监听失败的原因（端口被占用等）
+            await Task.WhenAll(quic, tcp, peers); // 抛出监听失败的原因（端口被占用等）
         }
 
         _ready.TrySetResult();
-        _log.Info("agent listening", ("control", ControlPort), ("udp", string.Join(',', UdpPorts)), ("tcp", string.Join(',', TcpPorts)));
+        _log.Info("agent listening", ("control", ControlPort), ("quic", string.Join(',', QuicPorts)), ("tcp", string.Join(',', TcpPorts)));
         try
         {
-            await Task.WhenAll(udp, tcp, peers, _link.RunAsync(linked.Token), ReportHostAsync(linked.Token));
+            await Task.WhenAll(quic, tcp, peers, _link.RunAsync(linked.Token), ReportHostAsync(linked.Token));
         }
         finally
         {
@@ -203,7 +203,7 @@ public sealed class AgentApp : IDisposable
                 MaxTotalPps = _config.Limits.MaxTotalPps,
                 AllowedTargetCidrs = _config.Limits.AllowedTargetCidrs,
                 MaxConcurrentTests = _config.Limits.MaxConcurrentTests,
-                AllowedUdpPorts = _udp.BoundPorts,
+                AllowedQuicPorts = _datagrams.BoundPorts,
                 AllowedTcpPorts = _tcp.BoundPorts,
             },
             BlockCatalog.AgentKinds);
@@ -310,7 +310,8 @@ public sealed class AgentApp : IDisposable
             Platform = MoShiro.Measurement.PlatformDetector.Detect(),
             TlsPublicKey = Convert.ToBase64String(_identity.Certificate.PublicKey.ExportSubjectPublicKeyInfo()),
             ProbeTcpPort = ControlPort,
-            ProbeUdpPorts = [.. UdpPorts],
+            ProbeQuicPorts = [.. QuicPorts],
+            LegacyProbeUdpPorts = [.. QuicPorts],
             LocalLimits = new LocalLimits
             {
                 MaxTotalMbps = _config.Limits.MaxTotalMbps,
diff --git a/backend/agent/src/MoShiro.Agent/AgentConfig.cs b/backend/agent/src/MoShiro.Agent/AgentConfig.cs
index 8f20c8c..3f59b4b 100644
--- a/backend/agent/src/MoShiro.Agent/AgentConfig.cs
+++ b/backend/agent/src/MoShiro.Agent/AgentConfig.cs
@@ -51,8 +51,15 @@ public sealed class ListenSection
     [JsonPropertyName("control_port")]
     public int ControlPort { get; set; } = 7443;
 
+    [JsonPropertyName("quic_ports")]
+    public List<int> QuicPorts { get; set; } = [7443];
+
+    /// <summary>Legacy config key accepted while deployments migrate to QUIC Datagram.</summary>
     [JsonPropertyName("udp_ports")]
-    public List<int> UdpPorts { get; set; } = [7443];
+    public List<int>? LegacyUdpPorts { get; set; }
+
+    [JsonIgnore]
+    public IReadOnlyList<int> EffectiveQuicPorts => LegacyUdpPorts ?? QuicPorts;
 
     [JsonPropertyName("tcp_ports")]
     public List<int> TcpPorts { get; set; } = [7444];
diff --git a/backend/agent/src/MoShiro.Agent/DataPlane/Registries.cs b/backend/agent/src/MoShiro.Agent/DataPlane/Registries.cs
index b467648..239cc7b 100644
--- a/backend/agent/src/MoShiro.Agent/DataPlane/Registries.cs
+++ b/backend/agent/src/MoShiro.Agent/DataPlane/Registries.cs
@@ -44,7 +44,7 @@ public sealed class ProbeSession : DataSession
 {
     private readonly ConcurrentDictionary<uint, ReplayWindow> _windows = new();
     private readonly ConcurrentDictionary<ulong, byte> _nonces = new();
-    private SocketAddress? _udpSource;
+    private SocketAddress? _datagramSource;
 
     public ProbeSession(PeerSessionInfo info)
         : base(info.Credentials.SessionIdValue, info.Credentials.Key)
@@ -71,11 +71,11 @@ public sealed class ProbeSession : DataSession
     public RpcSession<PeerContext>? Rpc { get; set; }
 
     /// <summary>最近一次认证通过的 UDP 包的源地址（Agent 把单向数据发往这里）。</summary>
-    public override IPEndPoint? UdpEndpoint
+    public override IPEndPoint? DatagramRemoteEndPoint
     {
         get
         {
-            SocketAddress? source = Volatile.Read(ref _udpSource);
+            SocketAddress? source = Volatile.Read(ref _datagramSource);
             return source is null ? null : (IPEndPoint)new IPEndPoint(source.Family == AddressFamily.InterNetworkV6 ? IPAddress.IPv6Any : IPAddress.Any, 0).Create(source);
         }
     }
@@ -83,7 +83,7 @@ public sealed class ProbeSession : DataSession
     /// <summary>记录 UDP 源地址；NAT 映射变化后地址变了返回 true（上报 endpoint_changed）。第一次看到地址不算变化。</summary>
     public bool UpdateSource(SocketAddress source)
     {
-        SocketAddress? previous = Volatile.Read(ref _udpSource);
+        SocketAddress? previous = Volatile.Read(ref _datagramSource);
         if (previous is not null && previous.Equals(source))
         {
             return false;
@@ -96,7 +96,7 @@ public sealed class ProbeSession : DataSession
             copy[i] = source[i];
         }
 
-        Volatile.Write(ref _udpSource, copy);
+        Volatile.Write(ref _datagramSource, copy);
         return previous is not null;
     }
 
@@ -312,7 +312,7 @@ public sealed class AgentAdmission : IAdmission
     /// <summary>NAT 映射变化，源地址变了：上报 <c>endpoint_changed</c>。</summary>
     public Action<ProbeSession>? OnEndpointChanged { get; set; }
 
-    public Admission AdmitPacket(DataSession session, in UdpHeader header, SocketAddress source, long nowUs)
+    public Admission AdmitDatagram(DataSession session, in MeasurementDatagramHeader header, SocketAddress source, long nowUs)
     {
         if (session is not ProbeSession probe || !_streams.TryGet(header.StreamId, out StreamInfo? stream) || !ReferenceEquals(stream.Owner, probe) || !probe.AcceptSequence(header.StreamId, header.Seq))
         {
diff --git a/backend/agent/src/MoShiro.Agent/Tasks/TaskManager.cs b/backend/agent/src/MoShiro.Agent/Tasks/TaskManager.cs
index d63792c..8253825 100644
--- a/backend/agent/src/MoShiro.Agent/Tasks/TaskManager.cs
+++ b/backend/agent/src/MoShiro.Agent/Tasks/TaskManager.cs
@@ -24,7 +24,7 @@ public sealed class TaskManager
     private readonly StreamRegistry _streams;
     private readonly BlockEnv _env;
     private readonly TargetRunners _targets;
-    private readonly Func<IReadOnlyList<int>> _udpPorts;
+    private readonly Func<IReadOnlyList<int>> _quicPorts;
     private readonly Func<IReadOnlyList<int>> _tcpPorts;
     private readonly TrustAnchor _trust;
     private readonly Dictionary<ProbeSession, Dictionary<string, LineEntry>> _sessionLines = [];
@@ -33,14 +33,14 @@ public sealed class TaskManager
     private long _version;
     private BudgetGuard? _guard;
 
-    public TaskManager(Func<BudgetGuard> guardFactory, StreamRegistry streams, BlockEnv env, TargetRunners targets, Func<IReadOnlyList<int>> udpPorts, Func<IReadOnlyList<int>> tcpPorts, TrustAnchor? trust = null)
+    public TaskManager(Func<BudgetGuard> guardFactory, StreamRegistry streams, BlockEnv env, TargetRunners targets, Func<IReadOnlyList<int>> quicPorts, Func<IReadOnlyList<int>> tcpPorts, TrustAnchor? trust = null)
     {
         _trust = trust ?? TrustAnchor.None;
         _guardFactory = guardFactory;
         _streams = streams;
         _env = env;
         _targets = targets;
-        _udpPorts = udpPorts;
+        _quicPorts = quicPorts;
         _tcpPorts = tcpPorts;
     }
 
@@ -229,7 +229,8 @@ public sealed class TaskManager
         {
             Version = _version,
             Tasks = [.. entries.Values.Select(e => e.Task)],
-            UdpPorts = [.. _udpPorts()],
+            QuicPorts = [.. _quicPorts()],
+            LegacyUdpPorts = [.. _quicPorts()],
             TcpPorts = [.. _tcpPorts()],
         };
 
diff --git a/backend/agent/src/MoShiro.Agent/Tests/TestRunner.cs b/backend/agent/src/MoShiro.Agent/Tests/TestRunner.cs
index 745a8bc..4b7c01d 100644
--- a/backend/agent/src/MoShiro.Agent/Tests/TestRunner.cs
+++ b/backend/agent/src/MoShiro.Agent/Tests/TestRunner.cs
@@ -107,7 +107,7 @@ public sealed class TestRunner
 
         // 按需测试的数据端口由 Agent 决定：Backend 给的端口如果不是本机监听的端口（模板里是出厂默认值，每个 Agent 可以改，
         // 而 Backend 并不知道 TCP 数据端口），就用本机监听的第一个端口。块头里记录的是实际用的端口。
-        IReadOnlyList<int> ports = _ports(kind.Blocks.Transport == "udp" ? "udp" : "tcp");
+        IReadOnlyList<int> ports = _ports(kind.Blocks.Transport == "quic_datagram" ? "quic_datagram" : "tcp");
         bool listening = phase.Params.TryGetValue("port", out System.Text.Json.JsonElement requested) && requested.TryGetInt32(out int port) && ports.Contains(port);
         if (!listening)
         {
diff --git a/backend/openapi/v1.json b/backend/openapi/v1.json
index f16a252..a114f7f 100644
--- a/backend/openapi/v1.json
+++ b/backend/openapi/v1.json
@@ -5174,6 +5174,7 @@
           "public_host",
           "probe_tcp_port",
           "probe_udp_ports",
+          "probe_quic_ports",
           "labels",
           "public_visible",
           "kinds",
@@ -5242,6 +5243,17 @@
               "format": "int32"
             }
           },
+          "probe_quic_ports": {
+            "type": "array",
+            "items": {
+              "pattern": "^-?(?:0|[1-9]\\d*)$",
+              "type": [
+                "integer",
+                "string"
+              ],
+              "format": "int32"
+            }
+          },
           "labels": {
             "type": "array",
             "items": {
@@ -6974,6 +6986,16 @@
           "ipv6_available": {
             "type": "boolean",
             "default": false
+          },
+          "quic_health": {
+            "oneOf": [
+              {
+                "type": "null"
+              },
+              {
+                "$ref": "#/components/schemas/QuicLineHealthDto"
+              }
+            ]
           }
         }
       },
@@ -7601,6 +7623,16 @@
           "ip_version": {
             "type": "string",
             "default": "ipv4"
+          },
+          "quic_health": {
+            "oneOf": [
+              {
+                "type": "null"
+              },
+              {
+                "$ref": "#/components/schemas/QuicLineHealthDto"
+              }
+            ]
           }
         }
       },
@@ -8581,6 +8613,156 @@
           }
         }
       },
+      "QuicLineHealthDto": {
+        "required": [
+          "connected",
+          "handshake_attempts",
+          "handshake_successes",
+          "handshake_failures",
+          "handshake_timeouts",
+          "handshake_success_rate",
+          "handshake_failure_rate",
+          "handshake_timeout_rate",
+          "handshake_p95_ms",
+          "handshake_sample_count",
+          "transport_packet_loss_rate",
+          "transport_packets_sent",
+          "transport_congestion_events",
+          "transport_ecn_congestion_events",
+          "path_mtu",
+          "at"
+        ],
+        "type": "object",
+        "properties": {
+          "connected": {
+            "type": "boolean"
+          },
+          "handshake_attempts": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "integer",
+              "string"
+            ],
+            "format": "int64"
+          },
+          "handshake_successes": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "integer",
+              "string"
+            ],
+            "format": "int64"
+          },
+          "handshake_failures": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "integer",
+              "string"
+            ],
+            "format": "int64"
+          },
+          "handshake_timeouts": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "integer",
+              "string"
+            ],
+            "format": "int64"
+          },
+          "handshake_success_rate": {
+            "pattern": "^-?(?:0|[1-9]\\d*)(?:\\.\\d+)?(?:[eE][+-]?\\d+)?$",
+            "type": [
+              "null",
+              "number",
+              "string"
+            ],
+            "format": "double"
+          },
+          "handshake_failure_rate": {
+            "pattern": "^-?(?:0|[1-9]\\d*)(?:\\.\\d+)?(?:[eE][+-]?\\d+)?$",
+            "type": [
+              "null",
+              "number",
+              "string"
+            ],
+            "format": "double"
+          },
+          "handshake_timeout_rate": {
+            "pattern": "^-?(?:0|[1-9]\\d*)(?:\\.\\d+)?(?:[eE][+-]?\\d+)?$",
+            "type": [
+              "null",
+              "number",
+              "string"
+            ],
+            "format": "double"
+          },
+          "handshake_p95_ms": {
+            "pattern": "^-?(?:0|[1-9]\\d*)(?:\\.\\d+)?(?:[eE][+-]?\\d+)?$",
+            "type": [
+              "null",
+              "number",
+              "string"
+            ],
+            "format": "double"
+          },
+          "handshake_sample_count": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "integer",
+              "string"
+            ],
+            "format": "int64"
+          },
+          "transport_packet_loss_rate": {
+            "pattern": "^-?(?:0|[1-9]\\d*)(?:\\.\\d+)?(?:[eE][+-]?\\d+)?$",
+            "type": [
+              "null",
+              "number",
+              "string"
+            ],
+            "format": "double"
+          },
+          "transport_packets_sent": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "null",
+              "integer",
+              "string"
+            ],
+            "format": "uint64"
+          },
+          "transport_congestion_events": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "null",
+              "integer",
+              "string"
+            ],
+            "format": "uint32"
+          },
+          "transport_ecn_congestion_events": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "null",
+              "integer",
+              "string"
+            ],
+            "format": "uint32"
+          },
+          "path_mtu": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "null",
+              "integer",
+              "string"
+            ],
+            "format": "uint16"
+          },
+          "at": {
+            "format": "date-time"
+          }
+        }
+      },
       "RawChunkMetaDto": {
         "required": [
           "chunk_id",
diff --git a/backend/probe/src/MoShiro.Probe/Link/AgentConnection.cs b/backend/probe/src/MoShiro.Probe/Link/AgentConnection.cs
index 43ede3e..4ef4ad0 100644
--- a/backend/probe/src/MoShiro.Probe/Link/AgentConnection.cs
+++ b/backend/probe/src/MoShiro.Probe/Link/AgentConnection.cs
@@ -30,6 +30,14 @@ public sealed class AgentConnection
 
     private readonly ConnectionEnv _env;
     private volatile ConnectionSession? _session;
+    private int _previousQuicSourcePort;
+    private QuicDatagramTransport? _activeDatagrams;
+    private readonly object _handshakeGate = new();
+    private readonly Queue<double> _handshakeSamplesMs = new();
+    private long _handshakeAttempts;
+    private long _handshakeSuccesses;
+    private long _handshakeFailures;
+    private long _handshakeTimeouts;
 
     public AgentConnection(KnownAgent endpoint, ConnectionEnv env)
     {
@@ -45,6 +53,38 @@ public sealed class AgentConnection
 
     public long ClockOffsetUs => _session?.Clock.OffsetUs ?? 0;
 
+    public ProbeQuicLinkHealth QuicHealth()
+    {
+        lock (_handshakeGate)
+        {
+            double? p95 = null;
+            if (_handshakeSamplesMs.Count > 0)
+            {
+                double[] sorted = [.. _handshakeSamplesMs.Order()];
+                p95 = sorted[(int)Math.Ceiling(sorted.Length * 0.95) - 1];
+            }
+
+            QuicTransportSnapshot? transport = Volatile.Read(ref _activeDatagrams)?.GetTransportSnapshot();
+            return new ProbeQuicLinkHealth
+            {
+                AgentId = Endpoint.AgentId,
+                IpVersion = Endpoint.IpVersion,
+                Connected = IsConnected,
+                HandshakeAttempts = _handshakeAttempts,
+                HandshakeSuccesses = _handshakeSuccesses,
+                HandshakeFailures = _handshakeFailures,
+                HandshakeTimeouts = _handshakeTimeouts,
+                HandshakeP95Ms = p95,
+                HandshakeSampleCount = _handshakeSamplesMs.Count,
+                TransportPacketLossRate = transport?.PacketLossRate,
+                TransportPacketsSent = transport?.PacketsSent,
+                TransportCongestionEvents = transport?.CongestionEvents,
+                TransportEcnCongestionEvents = transport?.EcnCongestionEvents,
+                PathMtu = transport?.PathMtu,
+            };
+        }
+    }
+
     public async Task RunAsync(CancellationToken ct)
     {
         // 重连的间隔别拉太长：每次尝试本来就要等好几秒（握手上限 30 秒），线路一恢复要尽快接上；带抖动，不会和别的节点撞在一起
@@ -93,10 +133,22 @@ public sealed class AgentConnection
         byte[] agentKey = Convert.FromBase64String(Endpoint.PublicKey);
         (PeerSessionInfo info, TlsFrameTransport transport) = await PeerConnector.ConnectAsync(
             address.ToString(), Endpoint.TcpPort, agentKey, _env.Identity, _env.ProbeId, ProbeApp.Version, 8 << 20, _env.Time, ct);
-        var remote = (IPEndPoint)info.Remote!;
         var data = new DataSession(info.Credentials.SessionIdValue, info.Credentials.Key);
-        using var udp = new UdpMux(new SingleSession(data), null, _env.Clock, new DataPlaneCounters(), _env.Log, remote.AddressFamily == AddressFamily.InterNetworkV6 ? IPAddress.IPv6Any : IPAddress.Any, []);
-        udp.Bind();
+        var remote = (IPEndPoint)info.Remote!;
+        IReadOnlyList<int> quicPorts = Endpoint.EffectiveQuicPorts;
+        int quicPort = quicPorts.Count == 0 ? 7443 : quicPorts[0];
+        using var datagrams = new QuicDatagramTransport(
+            data,
+            _env.Clock,
+            new DataPlaneCounters(),
+            _env.Log,
+            new IPEndPoint(remote.Address, quicPort),
+            agentKey,
+            Volatile.Read(ref _previousQuicSourcePort));
+        Volatile.Write(ref _activeDatagrams, datagrams);
+        datagrams.Bind();
+        using CancellationTokenSource cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
+
         var outbox = new Outbox(8 << 20);
         var clock = new ClockEstimator();
         var shipper = new FragmentShipper(outbox, new NodeId(Endpoint.AgentId), new ProbeId(_env.ProbeId), clock, _env.Time);
@@ -105,7 +157,7 @@ public sealed class AgentConnection
             Clock = _env.Clock,
             Log = _env.Log,
             Session = () => data,
-            Udp = udp,
+            Datagrams = datagrams,
             PeerAddress = remote.Address,
             PeerSpkiSha256 = NodeIdentity.Fingerprint(agentKey),
             KnockKey = Knock.DeriveKey(_env.Identity, agentKey),
@@ -117,14 +169,52 @@ public sealed class AgentConnection
         var rpc = new RpcSession<ConnectionSession>(transport, s_router, session, _env.Time);
         rpc.OnBinary = (_, _) => ValueTask.CompletedTask;
 
-        using CancellationTokenSource cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
         Task run = rpc.RunAsync(cts.Token);
-        Task receive = udp.RunAsync(cts.Token);
+        Task receive = datagrams.RunAsync(cts.Token);
         Task pump = PumpAsync(rpc, outbox, cts.Token);
         try
         {
             // 先同步时钟（块头里要带偏移）；Agent 随后推送线路任务集
             await SyncClockAsync(rpc, clock, rounds: 5, cts.Token);
+            lock (_handshakeGate)
+            {
+                _handshakeAttempts++;
+            }
+
+            try
+            {
+                await datagrams.ConnectAsync(cts.Token);
+                lock (_handshakeGate)
+                {
+                    _handshakeSuccesses++;
+                    if (datagrams.HandshakeDurationMs is { } elapsed)
+                    {
+                        _handshakeSamplesMs.Enqueue(elapsed);
+                        while (_handshakeSamplesMs.Count > 128)
+                        {
+                            _handshakeSamplesMs.Dequeue();
+                        }
+                    }
+                }
+            }
+            catch (Exception ex) when (!(ex is OperationCanceledException && cts.IsCancellationRequested))
+            {
+                lock (_handshakeGate)
+                {
+                    _handshakeFailures++;
+                    if (ex is TimeoutException)
+                    {
+                        _handshakeTimeouts++;
+                    }
+                }
+
+                throw;
+            }
+            if (datagrams.BoundPorts.Count > 0)
+            {
+                Volatile.Write(ref _previousQuicSourcePort, datagrams.BoundPorts[0]);
+            }
+
             backoff.Reset();
             _session = session;
             _env.Log.Info("agent session up", ("agent", Endpoint.AgentId), ("offset_us", clock.OffsetUs));
@@ -137,6 +227,7 @@ public sealed class AgentConnection
         finally
         {
             _session = null;
+            Volatile.Write(ref _activeDatagrams, null);
             await cts.CancelAsync();
             await session.StopAllAsync();
             await Quiet(run);
diff --git a/backend/probe/src/MoShiro.Probe/Link/AgentDirectory.cs b/backend/probe/src/MoShiro.Probe/Link/AgentDirectory.cs
index 69c68cc..c2cdad2 100644
--- a/backend/probe/src/MoShiro.Probe/Link/AgentDirectory.cs
+++ b/backend/probe/src/MoShiro.Probe/Link/AgentDirectory.cs
@@ -73,14 +73,15 @@ public sealed class AgentDirectory
         _trust.Update(result.TrustChain);
         foreach (AgentEndpoint agent in result.Agents)
         {
+            List<int> ports = agent.QuicPorts.Count > 0 ? agent.QuicPorts : agent.LegacyUdpPorts ?? [];
             if (!string.IsNullOrWhiteSpace(agent.Host))
             {
-                next.Add(new KnownAgent { AgentId = agent.AgentId.Value, Host = agent.Host, TcpPort = agent.TcpPort, PublicKey = agent.PublicKey });
+                next.Add(new KnownAgent { AgentId = agent.AgentId.Value, Host = agent.Host, TcpPort = agent.TcpPort, QuicPorts = [.. ports], PublicKey = agent.PublicKey });
             }
 
             if (!string.IsNullOrWhiteSpace(agent.Ipv6Host))
             {
-                next.Add(new KnownAgent { AgentId = agent.AgentId.Value, Host = agent.Ipv6Host, TcpPort = agent.TcpPort, PublicKey = agent.PublicKey, IpVersion = IpVersions.V6 });
+                next.Add(new KnownAgent { AgentId = agent.AgentId.Value, Host = agent.Ipv6Host, TcpPort = agent.TcpPort, QuicPorts = [.. ports], PublicKey = agent.PublicKey, IpVersion = IpVersions.V6 });
             }
         }
         lock (_gate)
@@ -111,5 +112,5 @@ public sealed class AgentDirectory
         a.Count == b.Count && a.Zip(b).All(p => Equal(p.First, p.Second));
 
     public static bool Equal(KnownAgent a, KnownAgent b) =>
-        a.AgentId == b.AgentId && a.IpVersion == b.IpVersion && a.Host == b.Host && a.TcpPort == b.TcpPort && a.PublicKey == b.PublicKey;
+        a.AgentId == b.AgentId && a.IpVersion == b.IpVersion && a.Host == b.Host && a.TcpPort == b.TcpPort && a.QuicPorts.SequenceEqual(b.QuicPorts) && a.PublicKey == b.PublicKey;
 }
diff --git a/backend/probe/src/MoShiro.Probe/ProbeApp.cs b/backend/probe/src/MoShiro.Probe/ProbeApp.cs
index fd8aee5..34a7549 100644
--- a/backend/probe/src/MoShiro.Probe/ProbeApp.cs
+++ b/backend/probe/src/MoShiro.Probe/ProbeApp.cs
@@ -45,7 +45,7 @@ public sealed class ProbeApp : IDisposable
             NodeId = identity.NodeId,
             NodeVersion = Version,
             Capabilities = [MoShiroCapabilities.Base],
-            HeartbeatExtra = () => JsonSerializer.SerializeToElement(new ProbeHeartbeatExtra { Update = update?.Status(), Ipv6 = Ipv6Diagnostics.Sample(null, Environment.GetEnvironmentVariable("MOSHIRO_NETWORK_SCOPE"), Environment.GetEnvironmentVariable("HOST_PROC")) }, MoShiroJsonContext.Default.ProbeHeartbeatExtra),
+            HeartbeatExtra = () => JsonSerializer.SerializeToElement(new ProbeHeartbeatExtra { Update = update?.Status(), Ipv6 = Ipv6Diagnostics.Sample(null, Environment.GetEnvironmentVariable("MOSHIRO_NETWORK_SCOPE"), Environment.GetEnvironmentVariable("HOST_PROC")), QuicLinks = SnapshotQuicLinks() }, MoShiroJsonContext.Default.ProbeHeartbeatExtra),
             HelloMeta = () => JsonSerializer.SerializeToElement(new ProbeHelloMeta { Owners = [.. trust.Controllers], Platform = PlatformDetector.Detect(), Ipv6 = Ipv6Diagnostics.Sample(null, Environment.GetEnvironmentVariable("MOSHIRO_NETWORK_SCOPE"), Environment.GetEnvironmentVariable("HOST_PROC")) }, MoShiroJsonContext.Default.ProbeHelloMeta),
         };
         var list = new StateHandler<ProbeAgentList>(
@@ -101,6 +101,14 @@ public sealed class ProbeApp : IDisposable
         }
     }
 
+    private List<ProbeQuicLinkHealth> SnapshotQuicLinks()
+    {
+        lock (_connections)
+        {
+            return [.. _connections.Values.Select(r => r.Connection.QuicHealth())];
+        }
+    }
+
     public async Task RunAsync(CancellationToken ct)
     {
         _log.Info("moshiro probe starting", MoShiro.Protocol.BuildInfo.Fields);
diff --git a/backend/probe/src/MoShiro.Probe/ProbeConfig.cs b/backend/probe/src/MoShiro.Probe/ProbeConfig.cs
index 233d8fc..f8cb9f2 100644
--- a/backend/probe/src/MoShiro.Probe/ProbeConfig.cs
+++ b/backend/probe/src/MoShiro.Probe/ProbeConfig.cs
@@ -57,6 +57,15 @@ public sealed class KnownAgent
     [JsonPropertyName("tcp_port")]
     public int TcpPort { get; set; }
 
+    [JsonPropertyName("quic_ports")]
+    public List<int> QuicPorts { get; set; } = [7443];
+
+    [JsonPropertyName("udp_ports")]
+    public List<int>? LegacyUdpPorts { get; set; }
+
+    [JsonIgnore]
+    public IReadOnlyList<int> EffectiveQuicPorts => LegacyUdpPorts ?? QuicPorts;
+
     /// <summary>Agent 的 TLS 证书公钥（SPKI，base64）：证书按它的 SHA-256 指纹固定，敲门密钥由它派生。</summary>
     [JsonPropertyName("public_key")]
     public string PublicKey { get; set; } = "";
diff --git a/backend/shared/MoShiro.Measurement/Blocks/BlockCatalog.cs b/backend/shared/MoShiro.Measurement/Blocks/BlockCatalog.cs
index 43465ab..385a547 100644
--- a/backend/shared/MoShiro.Measurement/Blocks/BlockCatalog.cs
+++ b/backend/shared/MoShiro.Measurement/Blocks/BlockCatalog.cs
@@ -26,7 +26,7 @@ public static class BlockCatalog
 {
     public static readonly IReadOnlyList<BlockPair> All =
     [
-        new("udp_echo", (e, s) => new UdpEchoDialer(e, s), (e, s) => new UdpEchoListener(e, s)),
+        new("udp_echo", (e, s) => new DatagramEchoDialer(e, s), (e, s) => new DatagramEchoListener(e, s)),
         new("tcp_echo", (e, s) => new TcpEchoDialer(e, s), (e, s) => new TcpEchoListener(e, s)),
         new("udp_train", (e, s) => new TrainDialer(e, s), (e, s) => new TrainListener(e, s), OnDemandOnly: true, Directions: ["rev"]),
         new("tcp_bulk", (e, s) => new TcpBulkDialer(e, s), (e, s) => new TcpBulkListener(e, s), OnDemandOnly: true, Directions: ["fwd", "rev"]),
diff --git a/backend/shared/MoShiro.Measurement/Blocks/Echo.cs b/backend/shared/MoShiro.Measurement/Blocks/Echo.cs
index ef639db..e29fe4f 100644
--- a/backend/shared/MoShiro.Measurement/Blocks/Echo.cs
+++ b/backend/shared/MoShiro.Measurement/Blocks/Echo.cs
@@ -11,7 +11,7 @@ namespace MoShiro.Measurement;
 internal sealed class EchoRows
 {
     /// <summary>UDP：没有在这段时间内回来的包就是丢了。</summary>
-    public const long UdpGraceUs = 2_000_000;
+    public const long DatagramGraceUs = 2_000_000;
 
     /// <summary>
     /// TCP 不会丢包，只会延迟（重传、队头阻塞）：一次几秒的中断之后，积压的回显会陆续回来，RTT 就是那几秒。
@@ -65,26 +65,27 @@ internal sealed class EchoRows
 /// <summary>
 /// UDP 回显，拨号方（Probe）：按声明的速率发包，t1 在发出时记录，回复到达时回填 t4。回复丢失的行 t4 缺失（Agent 一侧再补 t2/t3）。
 /// </summary>
-public sealed class UdpEchoDialer : BlockBase
+public sealed class DatagramEchoDialer : BlockBase
 {
     private readonly EchoRows _rows;
 
-    public UdpEchoDialer(BlockEnv env, BlockSpec spec)
+    public DatagramEchoDialer(BlockEnv env, BlockSpec spec)
         : base(env, spec)
     {
-        _rows = new EchoRows(spec.Kind, 16384, EchoRows.UdpGraceUs, settleOnReply: false);
+        _rows = new EchoRows(spec.Kind, 16384, EchoRows.DatagramGraceUs, settleOnReply: false);
     }
 
     public override long Produced => _rows.Count;
 
     public override async Task RunAsync(CancellationToken ct)
     {
-        UdpMux udp = Env.Udp!;
+        QuicDatagramTransport datagrams = Env.Datagrams!;
         DataSession session = Env.Session() ?? throw new BlockFaultException("no data session");
+        await datagrams.WaitUntilConnectedAsync(ct);
         IPEndPoint target = PeerEndpoint(Spec.Port);
         int size = (int)Spec.Int("size");
         byte[] packet = new byte[size];
-        udp.Register(Spec.StreamId, OnPacket);
+        datagrams.Register(Spec.StreamId, OnPacket);
         try
         {
             using var timer = new PeriodicTimer(TimeSpan.FromSeconds(1.0 / Spec.Int("rate_hz")), Env.Time);
@@ -92,8 +93,8 @@ public sealed class UdpEchoDialer : BlockBase
             {
                 long t1 = Env.Clock.NowUs();
                 uint seq = _rows.Add(size, t1);
-                UdpPacket.Write(packet, new UdpHeader(UdpPacketType.EchoRequest, session.SessionId, Spec.StreamId, seq, t1), session.Key);
-                udp.Send(target, packet);
+                MeasurementDatagram.Write(packet, new MeasurementDatagramHeader(MeasurementDatagramType.EchoRequest, session.SessionId, Spec.StreamId, seq, t1), session.Key);
+                datagrams.Send(session, target, packet);
             }
         }
         catch (OperationCanceledException)
@@ -102,7 +103,7 @@ public sealed class UdpEchoDialer : BlockBase
         }
         finally
         {
-            udp.Unregister(Spec.StreamId);
+            datagrams.Unregister(Spec.StreamId);
         }
     }
 
@@ -118,9 +119,9 @@ public sealed class UdpEchoDialer : BlockBase
         return 1;
     }
 
-    private void OnPacket(in UdpDelivery delivery)
+    private void OnPacket(in QuicDatagramDelivery delivery)
     {
-        if (delivery.Header.Type == UdpPacketType.EchoReply)
+        if (delivery.Header.Type == MeasurementDatagramType.EchoReply)
         {
             _rows.Reply(delivery.Header.Seq, delivery.ReceiveUs);
         }
@@ -128,11 +129,11 @@ public sealed class UdpEchoDialer : BlockBase
 }
 
 /// <summary>UDP 回显，监听方（Agent）：校验后立即回复一个等长的包，记录 t2（到达）和 t3（回复发出），按序号留给合并。</summary>
-public sealed class UdpEchoListener : BlockBase
+public sealed class DatagramEchoListener : BlockBase
 {
     private readonly RowStore _records;
 
-    public UdpEchoListener(BlockEnv env, BlockSpec spec)
+    public DatagramEchoListener(BlockEnv env, BlockSpec spec)
         : base(env, spec)
     {
         _records = new RowStore(spec.Kind.FindStream("msg")!, Side.Agent, 32768);
@@ -142,26 +143,26 @@ public sealed class UdpEchoListener : BlockBase
 
     public override async Task RunAsync(CancellationToken ct)
     {
-        Env.Udp!.Register(Spec.StreamId, OnPacket);
+        Env.Datagrams!.Register(Spec.StreamId, OnPacket);
         try
         {
             await WaitUntilCancelledAsync(ct);
         }
         finally
         {
-            Env.Udp.Unregister(Spec.StreamId);
+            Env.Datagrams.Unregister(Spec.StreamId);
         }
     }
 
-    private void OnPacket(in UdpDelivery delivery)
+    private void OnPacket(in QuicDatagramDelivery delivery)
     {
-        if (delivery.Header.Type != UdpPacketType.EchoRequest)
+        if (delivery.Header.Type != MeasurementDatagramType.EchoRequest)
         {
             return; // Data：探活包，只用来保持 NAT 映射和让准入策略学到源地址
         }
 
         long t2 = delivery.ReceiveUs;
-        delivery.ReplyAs(UdpPacketType.EchoReply);
+        delivery.ReplyAs(MeasurementDatagramType.EchoReply);
         Span<long> row = [t2, Env.Clock.NowUs()];
         _records.SetRow(delivery.Header.Seq, row);
     }
diff --git a/backend/shared/MoShiro.Measurement/Blocks/Train.cs b/backend/shared/MoShiro.Measurement/Blocks/Train.cs
index 7cfadac..f5dee5c 100644
--- a/backend/shared/MoShiro.Measurement/Blocks/Train.cs
+++ b/backend/shared/MoShiro.Measurement/Blocks/Train.cs
@@ -30,11 +30,11 @@ public sealed class TrainListener : BlockBase
     public override async Task RunAsync(CancellationToken ct)
     {
         // Probe 开始前发来的探活包（Data）要被接受，准入策略才能据此学到它当前的源地址（NAT 映射）；它们本身没有内容
-        Env.Udp!.Register(Spec.StreamId, static (in UdpDelivery _) => { });
+        Env.Datagrams!.Register(Spec.StreamId, static (in QuicDatagramDelivery _) => { });
         try
         {
             DataSession session = await WaitForPeerAsync(ct);
-            IPEndPoint target = session.UdpEndpoint!;
+            IPEndPoint target = session.DatagramRemoteEndPoint!;
             TimeSpan duration = TimeSpan.FromSeconds(Spec.Int("duration_s"));
             var done = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
             var thread = new Thread(() =>
@@ -58,7 +58,7 @@ public sealed class TrainListener : BlockBase
         }
         finally
         {
-            Env.Udp.Unregister(Spec.StreamId);
+            Env.Datagrams.Unregister(Spec.StreamId);
         }
     }
 
@@ -68,7 +68,7 @@ public sealed class TrainListener : BlockBase
         while (true)
         {
             DataSession? session = Env.Session();
-            if (session?.UdpEndpoint is not null)
+            if (session?.DatagramRemoteEndPoint is not null)
             {
                 return session;
             }
@@ -120,8 +120,8 @@ public sealed class TrainListener : BlockBase
             for (; seq < due; seq++)
             {
                 long sendUs = Env.Clock.NowUs();
-                UdpPacket.Write(packet, new UdpHeader(UdpPacketType.Data, session.SessionId, Spec.StreamId, seq, sendUs), session.Key);
-                Env.Udp!.Send(target, packet);
+                MeasurementDatagram.Write(packet, new MeasurementDatagramHeader(MeasurementDatagramType.Data, session.SessionId, Spec.StreamId, seq, sendUs), session.Key);
+                Env.Datagrams!.Send(session, target, packet);
                 Span<long> row = [size, sendUs];
                 _records.SetRow(seq, row);
                 Interlocked.Exchange(ref _sent, seq + 1L);
@@ -159,18 +159,19 @@ public sealed class TrainDialer : BlockBase
 
     public override async Task RunAsync(CancellationToken ct)
     {
-        UdpMux udp = Env.Udp!;
+        QuicDatagramTransport datagrams = Env.Datagrams!;
         DataSession session = Env.Session() ?? throw new BlockFaultException("no data session");
+        await datagrams.WaitUntilConnectedAsync(ct);
         _startUs = Env.Clock.NowUs();
-        udp.Register(Spec.StreamId, OnPacket);
+        datagrams.Register(Spec.StreamId, OnPacket);
         try
         {
-            byte[] hello = new byte[UdpPacket.MinBytes + 20];
+            byte[] hello = new byte[MeasurementDatagram.MinBytes + 20];
             IPEndPoint target = PeerEndpoint(Spec.Port);
             for (uint seq = 0; seq < 3; seq++)
             {
-                UdpPacket.Write(hello, new UdpHeader(UdpPacketType.Data, session.SessionId, Spec.StreamId, seq, Env.Clock.NowUs()), session.Key);
-                udp.Send(target, hello);
+                MeasurementDatagram.Write(hello, new MeasurementDatagramHeader(MeasurementDatagramType.Data, session.SessionId, Spec.StreamId, seq, Env.Clock.NowUs()), session.Key);
+                datagrams.Send(session, target, hello);
             }
 
             await WaitUntilCancelledAsync(ct);
@@ -178,7 +179,7 @@ public sealed class TrainDialer : BlockBase
         finally
         {
             _endUs = Env.Clock.NowUs();
-            udp.Unregister(Spec.StreamId);
+            datagrams.Unregister(Spec.StreamId);
         }
     }
 
@@ -228,10 +229,10 @@ public sealed class TrainDialer : BlockBase
     private static System.Text.Json.JsonElement Number(long value) =>
         System.Text.Json.JsonDocument.Parse(value.ToString(System.Globalization.CultureInfo.InvariantCulture)).RootElement.Clone();
 
-    private void OnPacket(in UdpDelivery delivery)
+    private void OnPacket(in QuicDatagramDelivery delivery)
     {
         long seq = delivery.Header.Seq;
-        if (delivery.Header.Type == UdpPacketType.Data && seq < _maxSeq && !_received.IsSet(seq, _tRecv))
+        if (delivery.Header.Type == MeasurementDatagramType.Data && seq < _maxSeq && !_received.IsSet(seq, _tRecv))
         {
             _received.Set(seq, _tRecv, delivery.ReceiveUs); // 只记第一次到达（重复的包不覆盖）
         }
diff --git a/backend/shared/MoShiro.Measurement/Core/Contracts.cs b/backend/shared/MoShiro.Measurement/Core/Contracts.cs
index d9fe153..301df12 100644
--- a/backend/shared/MoShiro.Measurement/Core/Contracts.cs
+++ b/backend/shared/MoShiro.Measurement/Core/Contracts.cs
@@ -11,6 +11,8 @@ namespace MoShiro.Measurement;
 /// </summary>
 public class DataSession
 {
+    private IDatagramConnection? _datagramConnection;
+
     public DataSession(long sessionId, byte[] key)
     {
         SessionId = sessionId;
@@ -21,13 +23,26 @@ public class DataSession
 
     public byte[] Key { get; }
 
+    public IDatagramConnection? DatagramConnection => Volatile.Read(ref _datagramConnection);
+
+    public void BindDatagramConnection(IDatagramConnection connection) => Volatile.Write(ref _datagramConnection, connection);
+
     /// <summary>对端最近一次通过认证的 UDP 源地址（监听方把单向数据发往这里；拨号方不需要）。</summary>
-    public virtual IPEndPoint? UdpEndpoint => null;
+    public virtual IPEndPoint? DatagramRemoteEndPoint => null;
 
     /// <summary>TCP 首帧的随机数只能用一次。拨号方不接受连接，所以默认放行。</summary>
     public virtual bool UseNonce(ReadOnlySpan<byte> nonce) => true;
 }
 
+/// <summary>Unreliable QUIC datagram sender bound to one authenticated measurement session.</summary>
+public interface IDatagramConnection
+{
+    bool Send(ReadOnlySpan<byte> datagram);
+}
+
+/// <summary>Transport-layer QUIC counters. These are separate from application Datagram delivery/loss.</summary>
+public sealed record QuicTransportSnapshot(double? PacketLossRate, ulong PacketsSent, uint CongestionEvents, uint EcnCongestionEvents, ushort PathMtu);
+
 public interface IDataSessions
 {
     DataSession? Find(long sessionId);
@@ -60,7 +75,7 @@ public enum Admission
 public interface IAdmission
 {
     /// <summary>UDP 包：<paramref name="source"/> 是认证通过的源地址（实现可以据此学习 NAT 重绑定）。</summary>
-    Admission AdmitPacket(DataSession session, in UdpHeader header, SocketAddress source, long nowUs);
+    Admission AdmitDatagram(DataSession session, in MeasurementDatagramHeader header, SocketAddress source, long nowUs);
 
     /// <summary>TCP 回显的一条消息（只限速）。</summary>
     bool AdmitMessage(DataSession session, uint streamId, long nowUs);
@@ -201,7 +216,7 @@ public sealed class BlockEnv
     /// <summary>当前的数据面会话（拨号方固定；监听方是 Agent 当前的 Probe 会话，可能没有）。</summary>
     public required Func<DataSession?> Session { get; init; }
 
-    public UdpMux? Udp { get; init; }
+    public QuicDatagramTransport? Datagrams { get; init; }
 
     /// <summary>监听方的准入策略（限速等）；拨号方为 null。</summary>
     public IAdmission? Admission { get; init; }
@@ -238,7 +253,7 @@ public sealed class BlockEnv
             Clock = Clock,
             Log = Log,
             Session = () => session,
-            Udp = Udp,
+            Datagrams = Datagrams,
             Admission = Admission,
             Counters = Counters,
             TcpListen = TcpListen,
diff --git a/backend/shared/MoShiro.Measurement/Execution/BudgetGuard.cs b/backend/shared/MoShiro.Measurement/Execution/BudgetGuard.cs
index add768e..934e6a9 100644
--- a/backend/shared/MoShiro.Measurement/Execution/BudgetGuard.cs
+++ b/backend/shared/MoShiro.Measurement/Execution/BudgetGuard.cs
@@ -17,7 +17,7 @@ public sealed class NodeLimits
     public int MaxConcurrentTests { get; init; } = 1;
 
     /// <summary>任务参数里的 <c>port</c> 只能取这些端口（本机配置的 listen 列表）。</summary>
-    public IReadOnlyList<int> AllowedUdpPorts { get; init; } = [7443];
+    public IReadOnlyList<int> AllowedQuicPorts { get; init; } = [7443];
 
     public IReadOnlyList<int> AllowedTcpPorts { get; init; } = [7444];
 }
@@ -143,7 +143,7 @@ public sealed class BudgetGuard
         }
 
         int port = (int)values.GetInt("port");
-        return kind.Blocks.Transport == "udp" ? _limits.AllowedUdpPorts.Contains(port) : _limits.AllowedTcpPorts.Contains(port);
+        return kind.Blocks.Transport == "quic_datagram" ? _limits.AllowedQuicPorts.Contains(port) : _limits.AllowedTcpPorts.Contains(port);
     }
 
     private static long EstimatePps(string kindId, ParamValues values) => kindId switch
diff --git a/backend/shared/MoShiro.Measurement/Net/MeasurementDatagramRouter.cs b/backend/shared/MoShiro.Measurement/Net/MeasurementDatagramRouter.cs
new file mode 100644
index 0000000..c38b55d
--- /dev/null
+++ b/backend/shared/MoShiro.Measurement/Net/MeasurementDatagramRouter.cs
@@ -0,0 +1,110 @@
+using System.Collections.Concurrent;
+using System.Net;
+using System.Net.Sockets;
+using MoShiro.Protocol;
+
+namespace MoShiro.Measurement;
+
+/// <summary>An authenticated, per-stream QUIC Datagram delivered to a measurement block.</summary>
+public readonly ref struct QuicDatagramDelivery
+{
+    private readonly Span<byte> _payload;
+    private readonly MsQuicConnection _connection;
+    private readonly DataPlaneCounters _counters;
+
+    internal QuicDatagramDelivery(MeasurementDatagramHeader header, Span<byte> payload, long receiveUs, DataSession session, MsQuicConnection connection, DataPlaneCounters counters)
+    {
+        Header = header;
+        _payload = payload;
+        ReceiveUs = receiveUs;
+        Session = session;
+        _connection = connection;
+        _counters = counters;
+    }
+
+    public MeasurementDatagramHeader Header { get; }
+    public ReadOnlySpan<byte> Payload => _payload;
+    public long ReceiveUs { get; }
+    public DataSession Session { get; }
+
+    public void ReplyAs(MeasurementDatagramType type)
+    {
+        _payload[3] = (byte)type;
+        MeasurementDatagram.Seal(_payload, Session.Key);
+        if (_connection.Send(_payload))
+        {
+            _counters.PacketOut();
+        }
+    }
+}
+
+public delegate void QuicDatagramHandler(in QuicDatagramDelivery delivery);
+
+/// <summary>Authenticates datagrams, applies Agent admission policy, and dispatches by stream.</summary>
+internal sealed class MeasurementDatagramRouter
+{
+    private readonly IDataSessions _sessions;
+    private readonly IAdmission? _admission;
+    private readonly MonoClock _clock;
+    private readonly ConcurrentDictionary<uint, QuicDatagramHandler> _handlers = new();
+
+    public MeasurementDatagramRouter(IDataSessions sessions, IAdmission? admission, MonoClock clock, DataPlaneCounters counters)
+    {
+        _sessions = sessions;
+        _admission = admission;
+        _clock = clock;
+        Counters = counters;
+    }
+
+    public DataPlaneCounters Counters { get; }
+
+    public void Register(uint streamId, QuicDatagramHandler handler) => _handlers[streamId] = handler;
+
+    public void Unregister(uint streamId) => _handlers.TryRemove(streamId, out _);
+
+    public void Dispatch(MsQuicConnection connection, ReadOnlySpan<byte> datagram)
+    {
+        Counters.PacketIn();
+        Span<byte> payload = stackalloc byte[MeasurementDatagram.MaxBytes];
+        if (datagram.Length > payload.Length)
+        {
+            Counters.DropInvalid();
+            return;
+        }
+
+        datagram.CopyTo(payload);
+        payload = payload[..datagram.Length];
+        if (!MeasurementDatagram.TryParseHeader(payload, out MeasurementDatagramHeader header)
+            || !_handlers.TryGetValue(header.StreamId, out QuicDatagramHandler? handler)
+            || _sessions.Find(header.SessionId) is not { } session
+            || !MeasurementDatagram.VerifyMac(payload, session.Key))
+        {
+            Counters.DropInvalid();
+            return;
+        }
+
+        IPEndPoint? remote = connection.RefreshRemoteEndPoint();
+        if (remote is null)
+        {
+            Counters.DropInvalid();
+            return;
+        }
+
+        long receiveUs = _clock.NowUs();
+        if (_admission is not null)
+        {
+            switch (_admission.AdmitDatagram(session, header, remote.Serialize(), receiveUs))
+            {
+                case Admission.Invalid:
+                    Counters.DropInvalid();
+                    return;
+                case Admission.RateLimited:
+                    Counters.DropRateLimited();
+                    return;
+            }
+        }
+
+        session.BindDatagramConnection(connection);
+        handler(new QuicDatagramDelivery(header, payload, receiveUs, session, connection, Counters));
+    }
+}
diff --git a/backend/shared/MoShiro.Measurement/Net/MsQuicApi.cs b/backend/shared/MoShiro.Measurement/Net/MsQuicApi.cs
new file mode 100644
index 0000000..e997628
--- /dev/null
+++ b/backend/shared/MoShiro.Measurement/Net/MsQuicApi.cs
@@ -0,0 +1,341 @@
+using System.Runtime.InteropServices;
+
+namespace MoShiro.Measurement;
+
+/// <summary>Small, versioned view of the MsQuic v2 C API table used by this transport.</summary>
+internal static unsafe class MsQuicApi
+{
+    private const int SetContextIndex = 0;
+    private const int SetCallbackHandlerIndex = 2;
+    private const int SetParamIndex = 3;
+    private const int GetParamIndex = 4;
+    private const int RegistrationOpenIndex = 5;
+    private const int RegistrationCloseIndex = 6;
+    private const int ConfigurationOpenIndex = 8;
+    private const int ConfigurationCloseIndex = 9;
+    private const int ConfigurationLoadCredentialIndex = 10;
+    private const int ListenerOpenIndex = 11;
+    private const int ListenerCloseIndex = 12;
+    private const int ListenerStartIndex = 13;
+    private const int ListenerStopIndex = 14;
+    private const int ConnectionOpenIndex = 15;
+    private const int ConnectionCloseIndex = 16;
+    private const int ConnectionShutdownIndex = 17;
+    private const int ConnectionStartIndex = 18;
+    private const int ConnectionSetConfigurationIndex = 19;
+    private const int DatagramSendIndex = 28;
+    private const uint ConnectionStatisticsV2Parameter = 0x05000016;
+
+    private static readonly SetContextDelegate s_setContext = MsQuicRuntime.Function<SetContextDelegate>(SetContextIndex);
+    private static readonly SetCallbackHandlerDelegate s_setCallbackHandler = MsQuicRuntime.Function<SetCallbackHandlerDelegate>(SetCallbackHandlerIndex);
+    private static readonly SetParamDelegate s_setParam = MsQuicRuntime.Function<SetParamDelegate>(SetParamIndex);
+    private static readonly GetParamDelegate s_getParam = MsQuicRuntime.Function<GetParamDelegate>(GetParamIndex);
+    private static readonly RegistrationOpenDelegate s_registrationOpen = MsQuicRuntime.Function<RegistrationOpenDelegate>(RegistrationOpenIndex);
+    private static readonly HandleCloseDelegate s_registrationClose = MsQuicRuntime.Function<HandleCloseDelegate>(RegistrationCloseIndex);
+    private static readonly ConfigurationOpenDelegate s_configurationOpen = MsQuicRuntime.Function<ConfigurationOpenDelegate>(ConfigurationOpenIndex);
+    private static readonly HandleCloseDelegate s_configurationClose = MsQuicRuntime.Function<HandleCloseDelegate>(ConfigurationCloseIndex);
+    private static readonly ConfigurationLoadCredentialDelegate s_loadCredential = MsQuicRuntime.Function<ConfigurationLoadCredentialDelegate>(ConfigurationLoadCredentialIndex);
+    private static readonly ListenerOpenDelegate s_listenerOpen = MsQuicRuntime.Function<ListenerOpenDelegate>(ListenerOpenIndex);
+    private static readonly HandleCloseDelegate s_listenerClose = MsQuicRuntime.Function<HandleCloseDelegate>(ListenerCloseIndex);
+    private static readonly ListenerStartDelegate s_listenerStart = MsQuicRuntime.Function<ListenerStartDelegate>(ListenerStartIndex);
+    private static readonly ListenerStopDelegate s_listenerStop = MsQuicRuntime.Function<ListenerStopDelegate>(ListenerStopIndex);
+    private static readonly ConnectionOpenDelegate s_connectionOpen = MsQuicRuntime.Function<ConnectionOpenDelegate>(ConnectionOpenIndex);
+    private static readonly HandleCloseDelegate s_connectionClose = MsQuicRuntime.Function<HandleCloseDelegate>(ConnectionCloseIndex);
+    private static readonly ConnectionShutdownDelegate s_connectionShutdown = MsQuicRuntime.Function<ConnectionShutdownDelegate>(ConnectionShutdownIndex);
+    private static readonly ConnectionStartDelegate s_connectionStart = MsQuicRuntime.Function<ConnectionStartDelegate>(ConnectionStartIndex);
+    private static readonly ConnectionSetConfigurationDelegate s_connectionSetConfiguration = MsQuicRuntime.Function<ConnectionSetConfigurationDelegate>(ConnectionSetConfigurationIndex);
+    private static readonly DatagramSendDelegate s_datagramSend = MsQuicRuntime.Function<DatagramSendDelegate>(DatagramSendIndex);
+
+    public static void SetContext(nint handle, nint context) => s_setContext(handle, context);
+
+    public static void SetCallbackHandler<T>(nint handle, T callback, nint context)
+        where T : Delegate => s_setCallbackHandler(handle, Marshal.GetFunctionPointerForDelegate(callback), context);
+
+    public static void SetParam(nint handle, uint parameter, byte value)
+    {
+        unsafe
+        {
+            uint status;
+            status = s_setParam(handle, parameter, sizeof(byte), &value);
+            Check(status, "SetParam");
+        }
+    }
+
+    public static byte[] GetAddress(nint handle, uint parameter)
+    {
+        byte[] address = new byte[128];
+        unsafe
+        {
+            fixed (byte* buffer = address)
+            {
+                uint length = (uint)address.Length;
+                uint status = s_getParam(handle, parameter, &length, buffer);
+                Check(status, "GetParam(address)");
+                Array.Resize(ref address, checked((int)length));
+            }
+        }
+
+        return address;
+    }
+
+    public static QuicStatisticsV2 GetStatisticsV2(nint connection)
+    {
+        QuicStatisticsV2 statistics = default;
+        unsafe
+        {
+            uint length = (uint)sizeof(QuicStatisticsV2);
+            uint status = s_getParam(connection, ConnectionStatisticsV2Parameter, &length, &statistics);
+            Check(status, "GetParam(connection statistics v2)");
+        }
+
+        return statistics;
+    }
+
+    public static nint RegistrationOpen(string appName)
+    {
+        nint utf8 = Marshal.StringToCoTaskMemUTF8(appName);
+        try
+        {
+            var config = new RegistrationConfig { AppName = utf8, ExecutionProfile = 0 };
+            uint status = s_registrationOpen(ref config, out nint registration);
+            Check(status, "RegistrationOpen");
+            return registration;
+        }
+        finally
+        {
+            Marshal.FreeCoTaskMem(utf8);
+        }
+    }
+
+    public static void RegistrationClose(nint handle) => s_registrationClose(handle);
+
+    public static nint ConfigurationOpen(nint registration, byte[] alpn)
+    {
+        unsafe
+        {
+            fixed (byte* alpnBytes = alpn)
+            {
+                var buffer = new QuicBuffer { Length = (uint)alpn.Length, Buffer = (nint)alpnBytes };
+                uint status = s_configurationOpen(registration, ref buffer, 1, 0, 0, 0, out nint configuration);
+                Check(status, "ConfigurationOpen");
+                return configuration;
+            }
+        }
+    }
+
+    public static void ConfigurationClose(nint handle) => s_configurationClose(handle);
+
+    public static void ConfigurationLoadCredential(nint configuration, ref CredentialConfig credential)
+    {
+        uint status = s_loadCredential(configuration, ref credential);
+        Check(status, "ConfigurationLoadCredential");
+    }
+
+    public static nint ListenerOpen<T>(nint registration, T callback, nint context)
+        where T : Delegate
+    {
+        uint status = s_listenerOpen(registration, Marshal.GetFunctionPointerForDelegate(callback), context, out nint listener);
+        Check(status, "ListenerOpen");
+        return listener;
+    }
+
+    public static void ListenerClose(nint handle) => s_listenerClose(handle);
+
+    public static void ListenerStart(nint listener, byte[] alpn, byte[] address)
+    {
+        unsafe
+        {
+            fixed (byte* alpnBytes = alpn)
+            fixed (byte* addressBytes = address)
+            {
+                var buffer = new QuicBuffer { Length = (uint)alpn.Length, Buffer = (nint)alpnBytes };
+                uint status = s_listenerStart(listener, ref buffer, 1, (nint)addressBytes);
+                Check(status, "ListenerStart");
+            }
+        }
+    }
+
+    public static void ListenerStop(nint handle) => s_listenerStop(handle);
+
+    public static nint ConnectionOpen<T>(nint registration, T callback, nint context)
+        where T : Delegate
+    {
+        uint status = s_connectionOpen(registration, Marshal.GetFunctionPointerForDelegate(callback), context, out nint connection);
+        Check(status, "ConnectionOpen");
+        return connection;
+    }
+
+    public static void ConnectionClose(nint handle) => s_connectionClose(handle);
+
+    public static void ConnectionShutdown(nint handle, ulong errorCode = 0) => s_connectionShutdown(handle, 0x00000001, errorCode);
+
+    public static void ConnectionStart(nint handle, nint configuration, ushort addressFamily, nint serverName, ushort port)
+    {
+        uint status = s_connectionStart(handle, configuration, addressFamily, serverName, port);
+        Check(status, "ConnectionStart");
+    }
+
+    public static void ConnectionBind(nint handle, byte[] address)
+    {
+        unsafe
+        {
+            fixed (byte* addressBytes = address)
+            {
+                uint status = s_setParam(handle, 0x05000001, (uint)address.Length, addressBytes);
+                Check(status, "SetParam(local address)");
+            }
+        }
+    }
+
+    public static void ConnectionSetConfiguration(nint handle, nint configuration)
+    {
+        uint status = s_connectionSetConfiguration(handle, configuration);
+        Check(status, "ConnectionSetConfiguration");
+    }
+
+    public static uint DatagramSend(nint connection, nint buffers, nint clientContext) => s_datagramSend(connection, buffers, 1, 0, clientContext);
+
+
+    public static void Check(uint status, string operation)
+    {
+        if (!Succeeded(status))
+        {
+            throw new InvalidOperationException($"MsQuic {operation} failed with status 0x{status:X8}.");
+        }
+    }
+
+    // QUIC_STATUS_PENDING (0xFFFFFFFE) is a successful asynchronous result. Other
+    // negative HRESULT/NTSTATUS values are failures on both Windows and POSIX.
+    public static bool Succeeded(uint status) => status == 0 || status == 0xFFFFFFFE;
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct QuicBuffer
+    {
+        public uint Length;
+        public nint Buffer;
+    }
+
+    // MsQuic QUIC_STATISTICS_V2 through v2.5. All fields are fixed-width on
+    // the supported 64-bit RIDs; keeping the field order aligned with msquic.h.
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct QuicStatisticsV2
+    {
+        public ulong CorrelationId;
+        public uint Flags;
+        public uint RttUs;
+        public uint MinRttUs;
+        public uint MaxRttUs;
+        public ulong TimingStart;
+        public ulong TimingInitialFlightEnd;
+        public ulong TimingHandshakeFlightEnd;
+        public uint HandshakeClientFlight1Bytes;
+        public uint HandshakeServerFlight1Bytes;
+        public uint HandshakeClientFlight2Bytes;
+        public ushort SendPathMtu;
+        public ulong SendTotalPackets;
+        public ulong SendRetransmittablePackets;
+        public ulong SendSuspectedLostPackets;
+        public ulong SendSpuriousLostPackets;
+        public ulong SendTotalBytes;
+        public ulong SendTotalStreamBytes;
+        public uint SendCongestionCount;
+        public uint SendPersistentCongestionCount;
+        public ulong RecvTotalPackets;
+        public ulong RecvReorderedPackets;
+        public ulong RecvDroppedPackets;
+        public ulong RecvDuplicatePackets;
+        public ulong RecvTotalBytes;
+        public ulong RecvTotalStreamBytes;
+        public ulong RecvDecryptionFailures;
+        public ulong RecvValidAckFrames;
+        public uint KeyUpdateCount;
+        public uint SendCongestionWindow;
+        public uint DestCidUpdateCount;
+        public uint SendEcnCongestionCount;
+        public byte HandshakeHopLimitTtl;
+        public uint RttVarianceUs;
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct RegistrationConfig
+    {
+        public nint AppName;
+        public int ExecutionProfile;
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct CredentialConfig
+    {
+        public uint Type;
+        public uint Flags;
+        public nint Certificate;
+        public nint Principal;
+        public nint Reserved;
+        public nint AsyncHandler;
+        public uint AllowedCipherSuites;
+        public nint CaCertificateFile;
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct Pkcs12Certificate
+    {
+        public nint Asn1Blob;
+        public uint Asn1BlobLength;
+        public nint PrivateKeyPassword;
+    }
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    internal delegate uint ListenerCallback(nint listener, nint context, nint @event);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    internal delegate uint ConnectionCallback(nint connection, nint context, nint @event);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate void SetContextDelegate(nint handle, nint context);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate void SetCallbackHandlerDelegate(nint handle, nint handler, nint context);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint SetParamDelegate(nint handle, uint parameter, uint bufferLength, void* buffer);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint GetParamDelegate(nint handle, uint parameter, uint* bufferLength, void* buffer);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint RegistrationOpenDelegate(ref RegistrationConfig config, out nint registration);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate void HandleCloseDelegate(nint handle);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint ConfigurationOpenDelegate(nint registration, ref QuicBuffer alpn, uint alpnCount, nint settings, uint settingsLength, nint context, out nint configuration);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint ConfigurationLoadCredentialDelegate(nint configuration, ref CredentialConfig credential);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint ListenerOpenDelegate(nint registration, nint callback, nint context, out nint listener);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint ListenerStartDelegate(nint listener, ref QuicBuffer alpn, uint alpnCount, nint address);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate void ListenerStopDelegate(nint listener);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint ConnectionOpenDelegate(nint registration, nint callback, nint context, out nint connection);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate void ConnectionShutdownDelegate(nint connection, uint flags, ulong errorCode);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint ConnectionStartDelegate(nint connection, nint configuration, ushort family, nint serverName, ushort serverPort);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint ConnectionSetConfigurationDelegate(nint connection, nint configuration);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate uint DatagramSendDelegate(nint connection, nint buffers, uint bufferCount, uint flags, nint clientContext);
+
+}
diff --git a/backend/shared/MoShiro.Measurement/Net/MsQuicConnection.cs b/backend/shared/MoShiro.Measurement/Net/MsQuicConnection.cs
new file mode 100644
index 0000000..c71a838
--- /dev/null
+++ b/backend/shared/MoShiro.Measurement/Net/MsQuicConnection.cs
@@ -0,0 +1,610 @@
+using System.Buffers;
+using System.Net;
+using System.Net.Sockets;
+using System.Runtime.InteropServices;
+using System.Diagnostics;
+using System.Security.Cryptography;
+using System.Security.Cryptography.X509Certificates;
+using Fleet.Core;
+
+namespace MoShiro.Measurement;
+
+internal delegate void MsQuicDatagramCallback(MsQuicConnection connection, ReadOnlySpan<byte> datagram);
+
+/// <summary>A single MsQuic connection with connection-bound datagram delivery.</summary>
+internal sealed class MsQuicConnection : IAsyncDisposable, IDatagramConnection
+{
+    private const uint DatagramReceiveEnabled = 0x0500000D;
+    private const uint ClientCredentialFlags = 0x00000001 | 0x00000004 | 0x00000010 | 0x00004000;
+    private const uint CertificateCredentialNone = 0;
+    private const uint CertificateCredentialContext = 3;
+    private const uint CertificateCredentialPkcs12 = 6;
+    private const uint ConnectionEventConnected = 0;
+    private const uint ConnectionEventShutdownByTransport = 1;
+    private const uint ConnectionEventShutdownByPeer = 2;
+    private const uint ConnectionEventShutdownComplete = 3;
+    private const uint ConnectionEventPeerAddressChanged = 5;
+    private const uint ConnectionEventDatagramStateChanged = 10;
+    private const uint ConnectionEventDatagramReceived = 11;
+    private const uint ConnectionEventDatagramSendStateChanged = 12;
+    private const uint ConnectionEventPeerCertificateReceived = 15;
+    private const int DatagramStateFinal = 3;
+    private const int QuicAddressBytes = 28;
+    private static readonly MsQuicApi.ConnectionCallback s_callback = OnEvent;
+
+    private readonly object _sendGate = new();
+    private readonly TaskCompletionSource _connected = new(TaskCreationOptions.RunContinuationsAsynchronously);
+    private readonly TaskCompletionSource _shutdown = new(TaskCreationOptions.RunContinuationsAsynchronously);
+    private readonly GCHandle _self;
+    private readonly byte[]? _expectedPeerSpki;
+    private readonly Action<MsQuicConnection>? _closed;
+    private readonly Action<IPEndPoint>? _peerAddressChanged;
+    private readonly INodeLog _log;
+    private readonly Dictionary<nint, SendState> _sends = [];
+    private nint _registration;
+    private nint _configuration;
+    private nint _handle;
+    private int _maxDatagramBytes;
+    private int _sendEnabled;
+    private int _disposeStarted;
+    private double? _handshakeDurationMs;
+
+    private MsQuicConnection(
+        nint handle,
+        nint registration,
+        nint configuration,
+        byte[]? expectedPeerSpki,
+        MsQuicDatagramCallback? datagramHandler,
+        INodeLog log,
+        Action<MsQuicConnection>? closed,
+        Action<IPEndPoint>? peerAddressChanged)
+    {
+        _handle = handle;
+        _registration = registration;
+        _configuration = configuration;
+        _expectedPeerSpki = expectedPeerSpki;
+        DatagramHandler = datagramHandler;
+        _log = log;
+        _closed = closed;
+        _peerAddressChanged = peerAddressChanged;
+        _self = GCHandle.Alloc(this);
+    }
+
+    public MsQuicDatagramCallback? DatagramHandler { get; set; }
+
+    public IPEndPoint? RemoteEndPoint { get; private set; }
+
+    public IPEndPoint? LocalEndPoint => Volatile.Read(ref _handle) is nint handle && handle != 0
+        ? ReadEndpoint(MsQuicApi.GetAddress(handle, 0x05000001))
+        : null;
+
+    public nint Handle => Volatile.Read(ref _handle);
+
+    public IPEndPoint? RefreshRemoteEndPoint()
+    {
+        if (RemoteEndPoint is not null || Handle == 0)
+        {
+            return RemoteEndPoint;
+        }
+
+        try
+        {
+            RemoteEndPoint = ReadEndpoint(MsQuicApi.GetAddress(Handle, 0x05000002));
+        }
+        catch (InvalidOperationException)
+        {
+            // Address isn't available until the handshake finishes.
+        }
+
+        return RemoteEndPoint;
+    }
+
+    public bool IsReady => _connected.Task.IsCompletedSuccessfully && Volatile.Read(ref _sendEnabled) != 0;
+
+    public int MaxDatagramBytes => Volatile.Read(ref _maxDatagramBytes);
+
+    public double? HandshakeDurationMs => _handshakeDurationMs;
+
+    public bool TryGetStatistics(out MsQuicApi.QuicStatisticsV2 statistics)
+    {
+        nint handle = Volatile.Read(ref _handle);
+        if (handle == 0)
+        {
+            statistics = default;
+            return false;
+        }
+
+        try
+        {
+            statistics = MsQuicApi.GetStatisticsV2(handle);
+            return true;
+        }
+        catch (InvalidOperationException)
+        {
+            statistics = default;
+            return false;
+        }
+    }
+
+    public static async Task<MsQuicConnection> ConnectAsync(
+        IPAddress address,
+        int port,
+        int localPort,
+        byte[] expectedPeerSpki,
+        MsQuicDatagramCallback datagramHandler,
+        INodeLog log,
+        CancellationToken ct)
+    {
+        nint registration = 0;
+        nint configuration = 0;
+        MsQuicConnection? connection = null;
+        long handshakeStarted = 0;
+        try
+        {
+            log.Info("opening MsQuic client registration");
+            registration = MsQuicApi.RegistrationOpen("moshiro-probe");
+            log.Info("opening MsQuic client configuration");
+            configuration = MsQuicApi.ConfigurationOpen(registration, QuicAlpn.Value);
+            log.Info("loading MsQuic client credentials");
+            LoadClientCredentials(configuration);
+            var endpoint = new IPEndPoint(address.AddressFamily == AddressFamily.InterNetworkV6 ? IPAddress.IPv6Any : IPAddress.Any, localPort);
+            SocketAddress serialized = endpoint.Serialize();
+            byte[] localAddress = new byte[QuicAddressBytes];
+            for (int i = 0; i < serialized.Size; i++)
+            {
+                localAddress[i] = serialized[i];
+            }
+            ushort nativeFamily = ReadAddressFamily(localAddress);
+            nint name = Marshal.StringToCoTaskMemUTF8(address.ToString());
+            try
+            {
+                nint handle = MsQuicApi.ConnectionOpen(registration, s_callback, 0);
+                log.Info("opened MsQuic client connection");
+                connection = new MsQuicConnection(handle, registration, configuration, expectedPeerSpki, datagramHandler, log, null, null);
+                registration = 0;
+                configuration = 0;
+                MsQuicApi.SetContext(handle, GCHandle.ToIntPtr(connection._self));
+                log.Info("enabling MsQuic datagram receive");
+                MsQuicApi.SetParam(handle, DatagramReceiveEnabled, 1);
+                log.Info("binding MsQuic local address", ("local_port", localPort));
+                MsQuicApi.ConnectionBind(handle, localAddress);
+                log.Info("starting MsQuic QUIC handshake", ("remote", address), ("port", port), ("local_port", localPort));
+                handshakeStarted = Stopwatch.GetTimestamp();
+                MsQuicApi.ConnectionStart(handle, connection._configuration, nativeFamily, name, checked((ushort)port));
+                log.Info("MsQuic connection start returned");
+            }
+            finally
+            {
+                Marshal.FreeCoTaskMem(name);
+            }
+
+            await connection._connected.Task.WaitAsync(TimeSpan.FromSeconds(10), ct);
+            connection._handshakeDurationMs = Stopwatch.GetElapsedTime(handshakeStarted).TotalMilliseconds;
+            return connection;
+        }
+        catch
+        {
+            if (connection is not null)
+            {
+                await connection.DisposeAsync();
+            }
+
+            if (configuration != 0)
+            {
+                MsQuicApi.ConfigurationClose(configuration);
+            }
+
+            if (registration != 0)
+            {
+                MsQuicApi.RegistrationClose(registration);
+            }
+
+            throw;
+        }
+    }
+
+    public static MsQuicConnection Accept(
+        nint handle,
+        nint configuration,
+        MsQuicDatagramCallback datagramHandler,
+        INodeLog log,
+        Action<MsQuicConnection> closed,
+        Action<IPEndPoint>? peerAddressChanged)
+    {
+        var connection = new MsQuicConnection(handle, 0, 0, null, datagramHandler, log, closed, peerAddressChanged);
+        MsQuicApi.SetContext(handle, GCHandle.ToIntPtr(connection._self));
+        MsQuicApi.SetCallbackHandler(handle, s_callback, GCHandle.ToIntPtr(connection._self));
+        MsQuicApi.ConnectionSetConfiguration(handle, configuration);
+        MsQuicApi.SetParam(handle, DatagramReceiveEnabled, 1);
+        return connection;
+    }
+
+    public bool Send(ReadOnlySpan<byte> datagram)
+    {
+        nint handle = Volatile.Read(ref _handle);
+        if (handle == 0 || !IsReady || datagram.Length > MaxDatagramBytes)
+        {
+            return false;
+        }
+
+        byte[] buffer = ArrayPool<byte>.Shared.Rent(datagram.Length);
+        datagram.CopyTo(buffer);
+        GCHandle pinned = GCHandle.Alloc(buffer, GCHandleType.Pinned);
+        nint nativeBuffer = Marshal.AllocHGlobal(Marshal.SizeOf<MsQuicApi.QuicBuffer>());
+        var state = new SendState(buffer, pinned, nativeBuffer);
+        GCHandle stateHandle = GCHandle.Alloc(state);
+        nint context = GCHandle.ToIntPtr(stateHandle);
+        lock (_sendGate)
+        {
+            if (_handle == 0)
+            {
+                stateHandle.Free();
+                state.Release();
+                return false;
+            }
+
+            _sends.Add(context, state);
+        }
+
+        var nativeBufferValue = new MsQuicApi.QuicBuffer
+        {
+            Length = (uint)datagram.Length,
+            Buffer = pinned.AddrOfPinnedObject(),
+        };
+        Marshal.StructureToPtr(nativeBufferValue, nativeBuffer, false);
+        uint status = MsQuicApi.DatagramSend(handle, nativeBuffer, context);
+        if (MsQuicApi.Succeeded(status))
+        {
+            return true;
+        }
+
+        ReleaseSend(context);
+        return false;
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        if (Interlocked.Exchange(ref _disposeStarted, 1) == 0 && Volatile.Read(ref _handle) is nint handle && handle != 0)
+        {
+            MsQuicApi.ConnectionShutdown(handle);
+        }
+
+        if (Volatile.Read(ref _handle) != 0)
+        {
+            await _shutdown.Task.ConfigureAwait(false);
+        }
+    }
+
+    public Task WaitForShutdownAsync() => _shutdown.Task;
+
+    private static void LoadClientCredentials(nint configuration)
+    {
+        var credential = new MsQuicApi.CredentialConfig { Type = CertificateCredentialNone, Flags = ClientCredentialFlags };
+        if (OperatingSystem.IsWindows())
+        {
+            credential.Flags &= ~0x00004000u;
+        }
+
+        MsQuicApi.ConfigurationLoadCredential(configuration, ref credential);
+    }
+
+    internal static void LoadServerCredentials(nint configuration, X509Certificate2 certificate)
+    {
+        var credential = new MsQuicApi.CredentialConfig();
+        GCHandle pfxPin = default;
+        nint pkcs12 = 0;
+        try
+        {
+            if (OperatingSystem.IsWindows())
+            {
+                credential.Type = CertificateCredentialContext;
+                credential.Certificate = certificate.Handle;
+            }
+            else
+            {
+                byte[] pfxBytes = certificate.Export(X509ContentType.Pkcs12);
+                pfxPin = GCHandle.Alloc(pfxBytes, GCHandleType.Pinned);
+                var pfxCertificate = new MsQuicApi.Pkcs12Certificate
+                {
+                    Asn1Blob = pfxPin.AddrOfPinnedObject(),
+                    Asn1BlobLength = (uint)pfxBytes.Length,
+                };
+                pkcs12 = Marshal.AllocHGlobal(Marshal.SizeOf<MsQuicApi.Pkcs12Certificate>());
+                Marshal.StructureToPtr(pfxCertificate, pkcs12, false);
+                credential.Type = CertificateCredentialPkcs12;
+                credential.Flags = 0x00004000;
+                credential.Certificate = pkcs12;
+            }
+
+            MsQuicApi.ConfigurationLoadCredential(configuration, ref credential);
+        }
+        finally
+        {
+            if (pkcs12 != 0)
+            {
+                Marshal.FreeHGlobal(pkcs12);
+            }
+
+            if (pfxPin.IsAllocated)
+            {
+                pfxPin.Free();
+            }
+        }
+    }
+
+    private static uint OnEvent(nint handle, nint context, nint eventPointer)
+    {
+        try
+        {
+            var connection = (MsQuicConnection)GCHandle.FromIntPtr(context).Target!;
+            uint eventType = unchecked((uint)Marshal.ReadInt32(eventPointer));
+            switch (eventType)
+            {
+                case ConnectionEventConnected:
+                    connection._log.Info("MsQuic QUIC handshake completed");
+                    connection.RefreshRemoteEndPoint();
+                    connection._connected.TrySetResult();
+                    break;
+                case ConnectionEventShutdownByTransport:
+                case ConnectionEventShutdownByPeer:
+                    connection._connected.TrySetException(new IOException("QUIC connection closed during handshake."));
+                    break;
+                case ConnectionEventShutdownComplete:
+                    connection.OnShutdownComplete(handle);
+                    break;
+                case ConnectionEventPeerAddressChanged:
+                {
+                    nint address = Marshal.ReadIntPtr(eventPointer, IntPtr.Size);
+                    IPEndPoint? endpoint = ReadEndpoint(address);
+                    if (endpoint is not null)
+                    {
+                        connection.RemoteEndPoint = endpoint;
+                        connection._peerAddressChanged?.Invoke(endpoint);
+                    }
+
+                    break;
+                }
+                case ConnectionEventDatagramStateChanged:
+                    connection.OnDatagramStateChanged(eventPointer);
+                    break;
+                case ConnectionEventDatagramReceived:
+                    connection.OnDatagramReceived(eventPointer);
+                    break;
+                case ConnectionEventDatagramSendStateChanged:
+                    connection.OnDatagramSendStateChanged(eventPointer);
+                    break;
+                case ConnectionEventPeerCertificateReceived:
+                    return connection.ValidatePeerCertificate(eventPointer);
+            }
+
+            return 0;
+        }
+        catch (Exception ex)
+        {
+            try
+            {
+                if (context != 0 && GCHandle.FromIntPtr(context).Target is MsQuicConnection connection)
+                {
+                    connection._log.Error("MsQuic connection callback failed", ("err", ex.Message));
+                }
+            }
+            catch
+            {
+                // Keep exceptions inside the native callback boundary.
+            }
+
+            return OperatingSystem.IsWindows() ? 0x80004005u : 1u;
+        }
+    }
+
+    private void OnDatagramStateChanged(nint eventPointer)
+    {
+        byte sendEnabled = Marshal.ReadByte(eventPointer, IntPtr.Size);
+        int maxSendLength = (ushort)Marshal.ReadInt16(eventPointer, IntPtr.Size + 1);
+        Volatile.Write(ref _maxDatagramBytes, maxSendLength);
+        Volatile.Write(ref _sendEnabled, sendEnabled == 0 ? 0 : 1);
+    }
+
+    private void OnDatagramReceived(nint eventPointer)
+    {
+        nint bufferPointer = Marshal.ReadIntPtr(eventPointer, IntPtr.Size);
+        if (bufferPointer == 0)
+        {
+            return;
+        }
+
+        var buffer = Marshal.PtrToStructure<MsQuicApi.QuicBuffer>(bufferPointer);
+        if (buffer.Buffer != 0 && buffer.Length > 0 && buffer.Length <= 65535)
+        {
+            unsafe
+            {
+            DatagramHandler?.Invoke(this, new ReadOnlySpan<byte>((void*)buffer.Buffer, checked((int)buffer.Length)));
+            }
+        }
+    }
+
+    private void OnDatagramSendStateChanged(nint eventPointer)
+    {
+        nint context = Marshal.ReadIntPtr(eventPointer, IntPtr.Size);
+        int state = Marshal.ReadInt32(eventPointer, IntPtr.Size * 2);
+        if (state >= DatagramStateFinal)
+        {
+            ReleaseSend(context);
+        }
+    }
+
+    private uint ValidatePeerCertificate(nint eventPointer)
+    {
+        nint certificate = Marshal.ReadIntPtr(eventPointer, IntPtr.Size);
+        if (certificate == 0 || _expectedPeerSpki is null)
+        {
+            return 0;
+        }
+
+        byte[] der;
+        if (OperatingSystem.IsWindows())
+        {
+            nint encoded = Marshal.ReadIntPtr(certificate, IntPtr.Size);
+            int length = Marshal.ReadInt32(certificate, IntPtr.Size * 2);
+            if (encoded == 0 || length <= 0 || length > 64 * 1024)
+            {
+                return 0x80004005u;
+            }
+
+            der = new byte[length];
+            Marshal.Copy(encoded, der, 0, length);
+        }
+        else
+        {
+            var nativeBuffer = Marshal.PtrToStructure<MsQuicApi.QuicBuffer>(certificate);
+            if (nativeBuffer.Buffer == 0 || nativeBuffer.Length == 0 || nativeBuffer.Length > 64 * 1024)
+            {
+                return 1;
+            }
+
+            der = new byte[checked((int)nativeBuffer.Length)];
+            Marshal.Copy(nativeBuffer.Buffer, der, 0, der.Length);
+        }
+
+        using X509Certificate2 peerCertificate = X509CertificateLoader.LoadCertificate(der);
+        bool valid = ExportSubjectPublicKeyInfo(peerCertificate).AsSpan().SequenceEqual(_expectedPeerSpki);
+        return valid ? 0 : OperatingSystem.IsWindows() ? 0x80004005u : 1u;
+    }
+
+    private static byte[] ExportSubjectPublicKeyInfo(X509Certificate2 certificate)
+    {
+        using ECDsa? ecdsa = certificate.GetECDsaPublicKey();
+        if (ecdsa is not null)
+        {
+            return ecdsa.ExportSubjectPublicKeyInfo();
+        }
+
+        using RSA? rsa = certificate.GetRSAPublicKey();
+        if (rsa is not null)
+        {
+            return rsa.ExportSubjectPublicKeyInfo();
+        }
+
+        using DSA? dsa = certificate.GetDSAPublicKey();
+        if (dsa is not null)
+        {
+            return dsa.ExportSubjectPublicKeyInfo();
+        }
+
+        return [];
+    }
+
+    private void ReleaseSend(nint context)
+    {
+        SendState? state;
+        lock (_sendGate)
+        {
+            if (!_sends.Remove(context, out state))
+            {
+                return;
+            }
+        }
+
+        if (GCHandle.FromIntPtr(context).IsAllocated)
+        {
+            GCHandle.FromIntPtr(context).Free();
+        }
+
+        state.Release();
+    }
+
+    private void OnShutdownComplete(nint handle)
+    {
+        if (Interlocked.Exchange(ref _handle, 0) == 0)
+        {
+            return;
+        }
+
+        MsQuicApi.ConnectionClose(handle);
+        lock (_sendGate)
+        {
+            foreach ((nint context, SendState state) in _sends)
+            {
+                GCHandle.FromIntPtr(context).Free();
+                state.Release();
+            }
+
+            _sends.Clear();
+        }
+
+        if (_configuration != 0)
+        {
+            MsQuicApi.ConfigurationClose(_configuration);
+        }
+
+        if (_registration != 0)
+        {
+            MsQuicApi.RegistrationClose(_registration);
+        }
+
+        _self.Free();
+        _shutdown.TrySetResult();
+        _closed?.Invoke(this);
+    }
+
+    private static IPEndPoint? ReadEndpoint(nint address)
+    {
+        if (address == 0)
+        {
+            return null;
+        }
+
+        ushort family = unchecked((ushort)Marshal.ReadInt16(address));
+        if (family == 2)
+        {
+            byte[] bytes = new byte[4];
+            Marshal.Copy(address + 4, bytes, 0, bytes.Length);
+            int port = (Marshal.ReadByte(address, 2) << 8) | Marshal.ReadByte(address, 3);
+            return new IPEndPoint(new IPAddress(bytes), port);
+        }
+
+        ushort ipv6Family = OperatingSystem.IsWindows() ? (ushort)23 : OperatingSystem.IsMacOS() ? (ushort)30 : (ushort)10;
+        if (family == ipv6Family)
+        {
+            byte[] bytes = new byte[16];
+            Marshal.Copy(address + 8, bytes, 0, bytes.Length);
+            int port = (Marshal.ReadByte(address, 2) << 8) | Marshal.ReadByte(address, 3);
+            long scope = unchecked((uint)Marshal.ReadInt32(address, 24));
+            return new IPEndPoint(new IPAddress(bytes, scope), port);
+        }
+
+        return null;
+    }
+
+    private static IPEndPoint? ReadEndpoint(byte[] address)
+    {
+        unsafe
+        {
+            fixed (byte* addressBytes = address)
+            {
+                return ReadEndpoint((nint)addressBytes);
+            }
+        }
+    }
+
+    private static ushort ReadAddressFamily(byte[] address) => (ushort)(address[0] | (address[1] << 8));
+
+    private sealed class SendState(byte[] buffer, GCHandle pin, nint nativeBuffer)
+    {
+        public void Release()
+        {
+            if (pin.IsAllocated)
+            {
+                pin.Free();
+            }
+
+            if (nativeBuffer != 0)
+            {
+                Marshal.FreeHGlobal(nativeBuffer);
+            }
+
+            ArrayPool<byte>.Shared.Return(buffer);
+        }
+    }
+
+}
diff --git a/backend/shared/MoShiro.Measurement/Net/MsQuicListener.cs b/backend/shared/MoShiro.Measurement/Net/MsQuicListener.cs
new file mode 100644
index 0000000..c2d5467
--- /dev/null
+++ b/backend/shared/MoShiro.Measurement/Net/MsQuicListener.cs
@@ -0,0 +1,195 @@
+using System.Collections.Concurrent;
+using System.Net;
+using System.Net.Sockets;
+using System.Runtime.InteropServices;
+using System.Security.Cryptography.X509Certificates;
+using Fleet.Core;
+
+namespace MoShiro.Measurement;
+
+/// <summary>Agent-side MsQuic listener. Measurement frames arrive only as QUIC DATAGRAM frames.</summary>
+internal sealed class MsQuicListener : IAsyncDisposable
+{
+    private const int QuicAddressBytes = 28;
+    private const uint ListenerEventNewConnection = 0;
+    private const uint ListenerLocalAddress = 0x04000000;
+    private static readonly MsQuicApi.ListenerCallback s_callback = OnListenerEvent;
+
+    private readonly IPAddress _bindAddress;
+    private readonly IReadOnlyList<int> _ports;
+    private readonly MsQuicDatagramCallback _datagramHandler;
+    private readonly INodeLog _log;
+    private readonly Action<IPEndPoint>? _peerAddressChanged;
+    private readonly X509Certificate2 _certificate;
+    private readonly GCHandle _self;
+    private readonly ConcurrentDictionary<nint, MsQuicConnection> _connections = new();
+    private readonly List<nint> _listeners = [];
+    private nint _registration;
+    private nint _configuration;
+    private int _disposed;
+
+    public MsQuicListener(
+        IPAddress bindAddress,
+        IReadOnlyList<int> ports,
+        X509Certificate2 certificate,
+        MsQuicDatagramCallback datagramHandler,
+        INodeLog log,
+        Action<IPEndPoint>? peerAddressChanged)
+    {
+        _bindAddress = bindAddress;
+        _ports = ports.Count == 0 ? [7443] : ports;
+        _certificate = certificate;
+        _datagramHandler = datagramHandler;
+        _log = log;
+        _peerAddressChanged = peerAddressChanged;
+        _self = GCHandle.Alloc(this);
+    }
+
+    public IReadOnlyList<int> BoundPorts { get; private set; } = [];
+
+    public void Start()
+    {
+        if (_registration != 0)
+        {
+            throw new InvalidOperationException("MsQuic listener is already started.");
+        }
+
+        _registration = MsQuicApi.RegistrationOpen("moshiro-agent");
+        try
+        {
+            _configuration = MsQuicApi.ConfigurationOpen(_registration, QuicAlpn.Value);
+            MsQuicConnection.LoadServerCredentials(_configuration, _certificate);
+            var bound = new List<int>(_ports.Count);
+            foreach (int port in _ports)
+            {
+                nint listener = MsQuicApi.ListenerOpen(_registration, s_callback, GCHandle.ToIntPtr(_self));
+                _listeners.Add(listener);
+                byte[] address = Serialize(new IPEndPoint(_bindAddress, port));
+                MsQuicApi.ListenerStart(listener, QuicAlpn.Value, address);
+                bound.Add(ReadPort(MsQuicApi.GetAddress(listener, ListenerLocalAddress)));
+            }
+
+            BoundPorts = bound;
+        }
+        catch
+        {
+            foreach (nint listener in _listeners)
+            {
+                MsQuicApi.ListenerStop(listener);
+                MsQuicApi.ListenerClose(listener);
+            }
+
+            _listeners.Clear();
+            DisposeHandles();
+            throw;
+        }
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        if (Interlocked.Exchange(ref _disposed, 1) != 0)
+        {
+            return;
+        }
+
+        foreach (nint listener in _listeners)
+        {
+            MsQuicApi.ListenerStop(listener);
+        }
+
+        foreach (nint listener in _listeners)
+        {
+            MsQuicApi.ListenerClose(listener);
+        }
+
+        _listeners.Clear();
+        MsQuicConnection[] connections = [.. _connections.Values];
+        await Task.WhenAll(connections.Select(c => c.DisposeAsync().AsTask())).ConfigureAwait(false);
+        DisposeHandles();
+        _self.Free();
+    }
+
+    private static uint OnListenerEvent(nint listener, nint context, nint @event)
+    {
+        try
+        {
+            var owner = (MsQuicListener)GCHandle.FromIntPtr(context).Target!;
+            uint eventType = unchecked((uint)Marshal.ReadInt32(@event));
+            if (eventType != ListenerEventNewConnection || Volatile.Read(ref owner._disposed) != 0)
+            {
+                return 1;
+            }
+
+            nint connectionHandle = Marshal.ReadIntPtr(@event, IntPtr.Size * 2);
+            owner._log.Info("accepted MsQuic QUIC connection");
+            MsQuicConnection? connection = null;
+            connection = MsQuicConnection.Accept(
+                connectionHandle,
+                owner._configuration,
+                owner._datagramHandler,
+                owner._log,
+                closed => owner._connections.TryRemove(connectionHandle, out _),
+                owner._peerAddressChanged);
+            if (!owner._connections.TryAdd(connectionHandle, connection))
+            {
+                _ = connection.DisposeAsync().AsTask();
+                return 1;
+            }
+
+            return 0;
+        }
+        catch (Exception ex)
+        {
+            try
+            {
+                if (context != 0 && GCHandle.FromIntPtr(context).Target is MsQuicListener owner)
+                {
+                    owner._log.Error("MsQuic listener callback failed", ("err", ex.Message));
+                }
+            }
+            catch
+            {
+                // Keep exceptions inside the native callback boundary.
+            }
+
+            return 1;
+        }
+    }
+
+    private void DisposeHandles()
+    {
+        if (_configuration != 0)
+        {
+            MsQuicApi.ConfigurationClose(_configuration);
+            _configuration = 0;
+        }
+
+        if (_registration != 0)
+        {
+            MsQuicApi.RegistrationClose(_registration);
+            _registration = 0;
+        }
+    }
+
+    private static byte[] Serialize(IPEndPoint endpoint)
+    {
+        SocketAddress source = endpoint.Serialize();
+        byte[] address = new byte[QuicAddressBytes];
+        for (int i = 0; i < source.Size; i++)
+        {
+            address[i] = source[i];
+        }
+
+        return address;
+    }
+
+    private static int ReadPort(byte[] address)
+    {
+        if (address.Length < 4)
+        {
+            throw new InvalidOperationException("MsQuic returned a truncated bound address.");
+        }
+
+        return (address[2] << 8) | address[3];
+    }
+}
diff --git a/backend/shared/MoShiro.Measurement/Net/MsQuicRuntime.cs b/backend/shared/MoShiro.Measurement/Net/MsQuicRuntime.cs
new file mode 100644
index 0000000..ff101c1
--- /dev/null
+++ b/backend/shared/MoShiro.Measurement/Net/MsQuicRuntime.cs
@@ -0,0 +1,118 @@
+using System.Runtime.InteropServices;
+
+namespace MoShiro.Measurement;
+
+/// <summary>Loads the MsQuic v2 ABI used by the QUIC datagram transport.</summary>
+internal static class MsQuicRuntime
+{
+    private const uint ApiVersion = 2;
+    private static readonly object s_gate = new();
+    private static nint s_library;
+    private static nint s_api;
+    private static OpenVersionDelegate? s_open;
+    private static CloseDelegate? s_close;
+    private static readonly List<nint> s_supportLibraries = [];
+
+    public static nint Api
+    {
+        get
+        {
+            lock (s_gate)
+            {
+                if (s_api != 0)
+                {
+                    return s_api;
+                }
+
+                string[] candidates = OperatingSystem.IsWindows()
+                    ? ["msquic.dll"]
+                    : OperatingSystem.IsMacOS()
+                        ? ["libmsquic.dylib"]
+                        : ["libmsquic.so.2", "libmsquic.so"];
+                LoadBundledSupportLibraries();
+                string appDirectory = AppContext.BaseDirectory;
+                foreach (string candidate in candidates)
+                {
+                    if (NativeLibrary.TryLoad(Path.Combine(appDirectory, candidate), out s_library)
+                        || NativeLibrary.TryLoad(candidate, out s_library))
+                    {
+                        break;
+                    }
+                }
+
+                if (s_library == 0)
+                {
+                    throw new DllNotFoundException($"MsQuic runtime was not found. Expected one of: {string.Join(", ", candidates)}.");
+                }
+
+                s_open = Marshal.GetDelegateForFunctionPointer<OpenVersionDelegate>(NativeLibrary.GetExport(s_library, "MsQuicOpenVersion"));
+                s_close = Marshal.GetDelegateForFunctionPointer<CloseDelegate>(NativeLibrary.GetExport(s_library, "MsQuicClose"));
+                int status = s_open(ApiVersion, out s_api);
+                if (status != 0 || s_api == 0)
+                {
+                    NativeLibrary.Free(s_library);
+                    s_library = 0;
+                    s_api = 0;
+                    throw new InvalidOperationException($"MsQuic API v{ApiVersion} could not be opened (status {status}).");
+                }
+
+                return s_api;
+            }
+        }
+    }
+
+    public static void Close()
+    {
+        lock (s_gate)
+        {
+            if (s_api != 0)
+            {
+                s_close!(s_api);
+                s_api = 0;
+            }
+
+            if (s_library != 0)
+            {
+                NativeLibrary.Free(s_library);
+                s_library = 0;
+            }
+
+            for (int i = s_supportLibraries.Count - 1; i >= 0; i--)
+            {
+                NativeLibrary.Free(s_supportLibraries[i]);
+            }
+
+            s_supportLibraries.Clear();
+        }
+    }
+
+    private static void LoadBundledSupportLibraries()
+    {
+        if (OperatingSystem.IsLinux())
+        {
+            TryLoadSupport("libnuma.so.1");
+        }
+        else if (OperatingSystem.IsMacOS())
+        {
+            TryLoadSupport("libcrypto.3.dylib");
+            TryLoadSupport("libssl.3.dylib");
+        }
+    }
+
+    private static void TryLoadSupport(string library)
+    {
+        if (NativeLibrary.TryLoad(Path.Combine(AppContext.BaseDirectory, library), out nint handle))
+        {
+            s_supportLibraries.Add(handle);
+        }
+    }
+
+    public static T Function<T>(int index)
+        where T : Delegate => Marshal.GetDelegateForFunctionPointer<T>(Marshal.ReadIntPtr(Api, checked(index * IntPtr.Size)));
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate int OpenVersionDelegate(uint version, out nint api);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate void CloseDelegate(nint api);
+}
diff --git a/backend/shared/MoShiro.Measurement/Net/QuicAlpn.cs b/backend/shared/MoShiro.Measurement/Net/QuicAlpn.cs
new file mode 100644
index 0000000..0786aad
--- /dev/null
+++ b/backend/shared/MoShiro.Measurement/Net/QuicAlpn.cs
@@ -0,0 +1,7 @@
+namespace MoShiro.Measurement;
+
+/// <summary>The application protocol negotiated by the Agent and Probe QUIC endpoints.</summary>
+internal static class QuicAlpn
+{
+    internal static readonly byte[] Value = "h3"u8.ToArray();
+}
diff --git a/backend/shared/MoShiro.Measurement/Net/QuicDatagramTransport.cs b/backend/shared/MoShiro.Measurement/Net/QuicDatagramTransport.cs
new file mode 100644
index 0000000..a36876c
--- /dev/null
+++ b/backend/shared/MoShiro.Measurement/Net/QuicDatagramTransport.cs
@@ -0,0 +1,205 @@
+using System.Net;
+using System.Net.Sockets;
+using System.Security.Cryptography.X509Certificates;
+using Fleet.Core;
+
+namespace MoShiro.Measurement;
+
+/// <summary>
+/// Measurement data transport. Agent instances listen on configured QUIC UDP ports; Probe instances
+/// open one QUIC connection from a newly selected ephemeral source port. Measurement frames are sent
+/// only with MsQuic DATAGRAM calls; the existing TLS peer connection continues to carry session control.
+/// </summary>
+public sealed class QuicDatagramTransport : IDisposable
+{
+    private readonly MeasurementDatagramRouter _router;
+    private readonly INodeLog _log;
+    private readonly MsQuicDatagramCallback _onDatagram;
+    private readonly IPAddress _bind;
+    private readonly IReadOnlyList<int> _ports;
+    private readonly X509Certificate2? _serverCertificate;
+    private readonly DataSession? _clientSession;
+    private readonly IPEndPoint? _remote;
+    private readonly byte[]? _peerSpki;
+    private readonly int _previousSourcePort;
+    private readonly TaskCompletionSource _clientReady = new(TaskCreationOptions.RunContinuationsAsynchronously);
+    private MsQuicListener? _listener;
+    private MsQuicConnection? _client;
+    private int _disposed;
+
+    /// <summary>Constructs an Agent-side QUIC listener.</summary>
+    public QuicDatagramTransport(IDataSessions sessions, IAdmission? admission, MonoClock clock, DataPlaneCounters counters, INodeLog log, IPAddress bind, IReadOnlyList<int> ports, X509Certificate2 serverCertificate)
+    {
+        _router = new MeasurementDatagramRouter(sessions, admission, clock, counters);
+        _log = log;
+        _onDatagram = _router.Dispatch;
+        _bind = bind;
+        _ports = ports;
+        _serverCertificate = serverCertificate;
+    }
+
+    /// <summary>Constructs a Probe-side QUIC dialer for one Agent session.</summary>
+    public QuicDatagramTransport(DataSession session, MonoClock clock, DataPlaneCounters counters, INodeLog log, IPEndPoint remote, byte[] peerSpki, int previousSourcePort)
+    {
+        _router = new MeasurementDatagramRouter(new SingleSession(session), null, clock, counters);
+        _log = log;
+        _onDatagram = _router.Dispatch;
+        _bind = remote.AddressFamily == AddressFamily.InterNetworkV6 ? IPAddress.IPv6Any : IPAddress.Any;
+        _ports = [];
+        _clientSession = session;
+        _remote = remote;
+        _peerSpki = peerSpki;
+        _previousSourcePort = previousSourcePort;
+    }
+
+    public IReadOnlyList<int> BoundPorts { get; private set; } = [];
+
+    public DataPlaneCounters Counters => _router.Counters;
+
+    public bool IsConnected => _client?.IsReady == true;
+
+    public double? HandshakeDurationMs => _client?.HandshakeDurationMs;
+
+    public QuicTransportSnapshot? GetTransportSnapshot()
+    {
+        if (_client is null || !_client.TryGetStatistics(out MsQuicApi.QuicStatisticsV2 stats))
+        {
+            return null;
+        }
+
+        ulong lost = stats.SendSuspectedLostPackets >= stats.SendSpuriousLostPackets
+            ? stats.SendSuspectedLostPackets - stats.SendSpuriousLostPackets
+            : 0;
+        double? packetLossRate = stats.SendTotalPackets > 0 ? lost * 100.0 / stats.SendTotalPackets : null;
+        return new QuicTransportSnapshot(packetLossRate, stats.SendTotalPackets, stats.SendCongestionCount, stats.SendEcnCongestionCount, stats.SendPathMtu);
+    }
+
+    public void Bind()
+    {
+        if (_remote is not null)
+        {
+            return;
+        }
+
+        if (_listener is not null)
+        {
+            throw new InvalidOperationException("QUIC listener is already bound.");
+        }
+
+        _listener = new MsQuicListener(_bind, _ports, _serverCertificate!, _onDatagram, _log, null);
+        _listener.Start();
+        BoundPorts = _listener.BoundPorts;
+    }
+
+    public async Task ConnectAsync(CancellationToken ct)
+    {
+        if (_remote is null || _clientSession is null || _peerSpki is null)
+        {
+            throw new InvalidOperationException("Only Probe-side QUIC transports can connect.");
+        }
+
+        try
+        {
+            int sourcePort = SelectSourcePort(_remote.AddressFamily, _previousSourcePort);
+            _client = await MsQuicConnection.ConnectAsync(
+                _remote.Address,
+                _remote.Port,
+                sourcePort,
+                _peerSpki,
+                _onDatagram,
+                _log,
+                ct);
+            _clientSession.BindDatagramConnection(_client);
+            BoundPorts = _client.LocalEndPoint is { } local ? [local.Port] : [sourcePort];
+            _clientReady.TrySetResult();
+        }
+        catch (Exception ex)
+        {
+            _log.Error("QUIC client connection failed", ("err", ex.Message));
+            _clientReady.TrySetException(ex);
+            throw;
+        }
+    }
+
+    public Task WaitUntilConnectedAsync(CancellationToken ct) => _remote is null ? Task.CompletedTask : _clientReady.Task.WaitAsync(ct);
+
+    public void Register(uint streamId, QuicDatagramHandler handler) => _router.Register(streamId, handler);
+
+    public void Unregister(uint streamId) => _router.Unregister(streamId);
+
+    /// <summary>Sends one measurement datagram on the connection for the supplied session.</summary>
+    public void Send(DataSession session, EndPoint target, ReadOnlySpan<byte> packet)
+    {
+        _ = target; // A QUIC connection owns its path; the Agent learns it from authenticated datagrams.
+        if (session.DatagramConnection?.Send(packet) == true)
+        {
+            _router.Counters.PacketOut();
+        }
+    }
+
+    public async Task RunAsync(CancellationToken ct)
+    {
+        if (_remote is not null)
+        {
+            await _clientReady.Task.WaitAsync(ct);
+            await _client!.WaitForShutdownAsync().WaitAsync(ct);
+            return;
+        }
+
+        try
+        {
+            await Task.Delay(Timeout.InfiniteTimeSpan, ct);
+        }
+        catch (OperationCanceledException) when (ct.IsCancellationRequested)
+        {
+            // Listener lifetime is controlled by AgentApp.
+        }
+    }
+
+    public void Dispose()
+    {
+        if (Interlocked.Exchange(ref _disposed, 1) != 0)
+        {
+            return;
+        }
+
+        _ = DisposeNativeResourcesAsync();
+    }
+
+    private async Task DisposeNativeResourcesAsync()
+    {
+        try
+        {
+            if (_client is not null)
+            {
+                await _client.DisposeAsync().ConfigureAwait(false);
+            }
+
+            if (_listener is not null)
+            {
+                await _listener.DisposeAsync().ConfigureAwait(false);
+            }
+        }
+        catch (Exception ex) when (ex is IOException or InvalidOperationException or ObjectDisposedException)
+        {
+            _log.Error("QUIC datagram transport shutdown failed", ("err", ex.Message));
+        }
+    }
+
+    private static int SelectSourcePort(AddressFamily family, int previousPort)
+    {
+        IPAddress local = family == AddressFamily.InterNetworkV6 ? IPAddress.IPv6Any : IPAddress.Any;
+        for (int attempt = 0; attempt < 8; attempt++)
+        {
+            using var socket = new Socket(family, SocketType.Dgram, ProtocolType.Udp);
+            socket.Bind(new IPEndPoint(local, 0));
+            int port = ((IPEndPoint)socket.LocalEndPoint!).Port;
+            if (port != previousPort)
+            {
+                return port;
+            }
+        }
+
+        throw new SocketException((int)SocketError.AddressAlreadyInUse);
+    }
+}
diff --git a/backend/shared/MoShiro.Measurement/Net/UdpMux.cs b/backend/shared/MoShiro.Measurement/Net/UdpMux.cs
deleted file mode 100644
index 9d036af..0000000
--- a/backend/shared/MoShiro.Measurement/Net/UdpMux.cs
+++ /dev/null
@@ -1,216 +0,0 @@
-using System.Collections.Concurrent;
-using System.Net;
-using System.Net.Sockets;
-using Fleet.Core;
-using MoShiro.Protocol;
-
-namespace MoShiro.Measurement;
-
-/// <summary>一个通过校验的 UDP 包，交给按 <c>stream_id</c> 登记的处理函数。处理函数在接收循环里同步执行，不能阻塞。</summary>
-public readonly ref struct UdpDelivery
-{
-    private readonly Span<byte> _packet;
-    private readonly Socket _socket;
-    private readonly SocketAddress _source;
-    private readonly DataPlaneCounters _counters;
-
-    internal UdpDelivery(UdpHeader header, Span<byte> packet, long receiveUs, DataSession session, Socket socket, SocketAddress source, DataPlaneCounters counters)
-    {
-        Header = header;
-        _packet = packet;
-        ReceiveUs = receiveUs;
-        Session = session;
-        _socket = socket;
-        _source = source;
-        _counters = counters;
-    }
-
-    public UdpHeader Header { get; }
-
-    public ReadOnlySpan<byte> Packet => _packet;
-
-    /// <summary>包到达的时刻（本节点的单调时钟，微秒）：从接收返回的那一刻取，不含校验的耗时。</summary>
-    public long ReceiveUs { get; }
-
-    public DataSession Session { get; }
-
-    /// <summary>
-    /// 原地回复：同样的长度，只把 type 改成 <paramref name="type"/> 并重新计算 MAC，发回请求的实际源地址。
-    /// 回复与请求等长，所以监听方不能被当成放大器。发送失败（源地址已经不可达）不抛出。
-    /// </summary>
-    public void ReplyAs(UdpPacketType type)
-    {
-        _packet[3] = (byte)type;
-        UdpPacket.Seal(_packet, Session.Key);
-        try
-        {
-            _socket.SendTo(_packet, SocketFlags.None, _source);
-            _counters.PacketOut();
-        }
-        catch (SocketException)
-        {
-            // 回复丢失由对端的缺失体现
-        }
-    }
-}
-
-public delegate void UdpHandler(in UdpDelivery delivery);
-
-/// <summary>
-/// UDP 数据面：一个或多个套接字，按 <c>stream_id</c> 把包分发给积木。校验顺序：长度、magic、version、type →
-/// 流和会话都存在 → MAC → （监听方）<see cref="IAdmission"/>（重放窗口、限速）。任何一步失败都静默丢弃并计数，不回复。
-/// 接收循环只做校验和分发，不分配对象。两端共用这一份代码：Agent 监听多个端口并带准入策略，Probe 每个 Agent 一个临时端口。
-/// </summary>
-public sealed class UdpMux : IDisposable
-{
-    private const int WindowsUdpConnReset = -1744830452; // SIO_UDP_CONNRESET
-
-    private readonly IDataSessions _sessions;
-    private readonly IAdmission? _admission;
-    private readonly MonoClock _clock;
-    private readonly DataPlaneCounters _counters;
-    private readonly INodeLog _log;
-    private readonly IPAddress _bind;
-    private readonly IReadOnlyList<int> _ports;
-    private readonly List<Socket> _sockets = [];
-    private readonly ConcurrentDictionary<uint, UdpHandler> _handlers = new();
-
-    /// <param name="ports">要监听的端口（0 表示由系统分配）；空表示一个临时端口。</param>
-    public UdpMux(IDataSessions sessions, IAdmission? admission, MonoClock clock, DataPlaneCounters counters, INodeLog log, IPAddress bind, IReadOnlyList<int> ports)
-    {
-        _sessions = sessions;
-        _admission = admission;
-        _clock = clock;
-        _counters = counters;
-        _log = log;
-        _bind = bind;
-        _ports = ports.Count == 0 ? [0] : ports;
-    }
-
-    public IReadOnlyList<int> BoundPorts { get; private set; } = [];
-
-    public DataPlaneCounters Counters => _counters;
-
-    /// <summary>绑定套接字（端口被占用等错误在这里抛出）。</summary>
-    public void Bind()
-    {
-        var bound = new List<int>();
-        foreach (int port in _ports)
-        {
-            var socket = new Socket(_bind.AddressFamily, SocketType.Dgram, ProtocolType.Udp) { ReceiveBufferSize = 4 << 20, SendBufferSize = 4 << 20 };
-            if (_bind.AddressFamily == AddressFamily.InterNetworkV6)
-            {
-                socket.DualMode = true;
-            }
-
-            if (OperatingSystem.IsWindows())
-            {
-                // Windows 上对一个已关闭的端口发送之后，下一次接收会抛 ConnectionReset：关掉这个行为
-                socket.IOControl(WindowsUdpConnReset, [0], null);
-            }
-
-            socket.Bind(new IPEndPoint(_bind, port));
-            bound.Add(((IPEndPoint)socket.LocalEndPoint!).Port);
-            _sockets.Add(socket);
-        }
-
-        BoundPorts = bound;
-    }
-
-    public void Register(uint streamId, UdpHandler handler) => _handlers[streamId] = handler;
-
-    public void Unregister(uint streamId) => _handlers.TryRemove(streamId, out _);
-
-    /// <summary>从第一个套接字发出一个已经封好的包。发送失败（没有路由、缓冲区满）不抛出：丢包本身就是测量结果。</summary>
-    public void Send(EndPoint to, ReadOnlySpan<byte> packet)
-    {
-        try
-        {
-            _sockets[0].SendTo(packet, SocketFlags.None, to);
-            _counters.PacketOut();
-        }
-        catch (SocketException)
-        {
-            // 记为丢失
-        }
-    }
-
-    public async Task RunAsync(CancellationToken ct)
-    {
-        try
-        {
-            await Task.WhenAll(_sockets.Select(s => ReceiveLoopAsync(s, ct)));
-        }
-        catch (ObjectDisposedException)
-        {
-            // 套接字已释放：停止
-        }
-    }
-
-    public void Dispose()
-    {
-        foreach (Socket socket in _sockets)
-        {
-            socket.Dispose();
-        }
-    }
-
-    private async Task ReceiveLoopAsync(Socket socket, CancellationToken ct)
-    {
-        byte[] buffer = new byte[UdpPacket.MaxBytes + 64];
-        var source = new SocketAddress(socket.AddressFamily);
-        while (!ct.IsCancellationRequested)
-        {
-            int length;
-            try
-            {
-                length = await socket.ReceiveFromAsync(buffer.AsMemory(), SocketFlags.None, source, ct);
-            }
-            catch (OperationCanceledException)
-            {
-                return;
-            }
-            catch (ObjectDisposedException)
-            {
-                return;
-            }
-            catch (SocketException ex)
-            {
-                // 个别错误（例如对端的 ICMP 不可达）不能让接收循环退出
-                _log.Warn("udp receive failed", ("err", ex.SocketErrorCode));
-                continue;
-            }
-
-            Dispatch(socket, buffer, length, source, _clock.NowUs());
-        }
-    }
-
-    private void Dispatch(Socket socket, byte[] buffer, int length, SocketAddress source, long receiveUs)
-    {
-        _counters.PacketIn();
-        Span<byte> packet = buffer.AsSpan(0, length);
-        if (!UdpPacket.TryParseHeader(packet, out UdpHeader header)
-            || !_handlers.TryGetValue(header.StreamId, out UdpHandler? handler)
-            || _sessions.Find(header.SessionId) is not { } session
-            || !UdpPacket.VerifyMac(packet, session.Key))
-        {
-            _counters.DropInvalid();
-            return;
-        }
-
-        if (_admission is not null)
-        {
-            switch (_admission.AdmitPacket(session, header, source, receiveUs))
-            {
-                case Admission.Invalid:
-                    _counters.DropInvalid();
-                    return;
-                case Admission.RateLimited:
-                    _counters.DropRateLimited();
-                    return;
-            }
-        }
-
-        handler(new UdpDelivery(header, packet, receiveUs, session, socket, source, _counters));
-    }
-}
diff --git a/backend/shared/MoShiro.Protocol/Catalog/Kinds/Kinds.cs b/backend/shared/MoShiro.Protocol/Catalog/Kinds/Kinds.cs
index f89639a..4cb7f6e 100644
--- a/backend/shared/MoShiro.Protocol/Catalog/Kinds/Kinds.cs
+++ b/backend/shared/MoShiro.Protocol/Catalog/Kinds/Kinds.cs
@@ -27,10 +27,10 @@ public static class Kinds
 
     public static readonly KindSpec UdpEcho = new(
         "udp_echo",
-        "UDP echo",
-        "Fixed-rate UDP echo with four timestamps per packet.",
+        "QUIC Datagram echo",
+        "Fixed-rate QUIC Datagram echo with four timestamps per packet.",
         Scope.Line,
-        new BlockSet("udp", "fixed", "fixed", "echo", []),
+        new BlockSet("quic_datagram", "fixed", "fixed", "echo", []),
         [
             P.Int("rate_hz", 10, 1, 200, "Hz"),
             P.Int("size", 64, 44, 1400, "B"),
@@ -41,10 +41,10 @@ public static class Kinds
 
     public static readonly KindSpec UdpTrain = new(
         "udp_train",
-        "UDP train",
-        "Fixed-rate or laddered one-way UDP stream (Agent to Probe) for loss and jitter under load.",
+        "QUIC Datagram train",
+        "Fixed-rate or laddered one-way QUIC Datagram stream (Agent to Probe) for loss and delay variation under load.",
         Scope.Line,
-        new BlockSet("udp", "ladder", "fixed", "sink", []),
+        new BlockSet("quic_datagram", "ladder", "fixed", "sink", []),
         [
             P.Number("mbps", 10, 0.1, 1000, "Mbit/s"),
             P.Int("size", 1250, 200, 1400, "B"),
diff --git a/backend/shared/MoShiro.Protocol/Rpc/MoShiroRpc.cs b/backend/shared/MoShiro.Protocol/Rpc/MoShiroRpc.cs
index c063c88..742a7de 100644
--- a/backend/shared/MoShiro.Protocol/Rpc/MoShiroRpc.cs
+++ b/backend/shared/MoShiro.Protocol/Rpc/MoShiroRpc.cs
@@ -146,8 +146,11 @@ public sealed class AgentEndpoint
     [JsonPropertyName("tcp_port")]
     public int TcpPort { get; set; }
 
+    [JsonPropertyName("quic_ports")]
+    public List<int> QuicPorts { get; set; } = [];
+
     [JsonPropertyName("udp_ports")]
-    public List<int> UdpPorts { get; set; } = [];
+    public List<int> LegacyUdpPorts { get; set; } = [];
 
     /// <summary>Agent 面向 Probe 的 TLS 证书公钥（SPKI，base64）：证书按它的 SHA-256 指纹固定，敲门密钥由它和 Probe 的身份密钥派生。</summary>
     [JsonPropertyName("public_key")]
@@ -175,8 +178,11 @@ public sealed class AgentEnrollMeta
     [JsonPropertyName("probe_tcp_port")]
     public int ProbeTcpPort { get; set; } = 7443;
 
+    [JsonPropertyName("probe_quic_ports")]
+    public List<int> ProbeQuicPorts { get; set; } = [];
+
     [JsonPropertyName("probe_udp_ports")]
-    public List<int> ProbeUdpPorts { get; set; } = [7443];
+    public List<int>? LegacyProbeUdpPorts { get; set; }
 
     [JsonPropertyName("public_host")]
     public string? PublicHost { get; set; }
@@ -296,6 +302,9 @@ public sealed class UpdateStatus
 /// <summary>Probe 的 <c>fleet.heartbeat</c> 附加字段：更新器的状态。</summary>
 public sealed class ProbeHeartbeatExtra
 {
+    [JsonPropertyName("quic_links")]
+    public List<ProbeQuicLinkHealth>? QuicLinks { get; set; }
+
     [JsonPropertyName("ipv6")]
     public Ipv6Diagnostic? Ipv6 { get; set; }
 
@@ -303,6 +312,53 @@ public sealed class ProbeHeartbeatExtra
     public UpdateStatus? Update { get; set; }
 }
 
+/// <summary>Probe's rolling QUIC connection health snapshot for one Agent/IP path.</summary>
+public sealed class ProbeQuicLinkHealth
+{
+    [JsonPropertyName("agent_id")]
+    public string AgentId { get; set; } = "";
+
+    [JsonPropertyName("ip_version")]
+    public string IpVersion { get; set; } = IpVersions.V4;
+
+    [JsonPropertyName("connected")]
+    public bool Connected { get; set; }
+
+    [JsonPropertyName("handshake_attempts")]
+    public long HandshakeAttempts { get; set; }
+
+    [JsonPropertyName("handshake_successes")]
+    public long HandshakeSuccesses { get; set; }
+
+    [JsonPropertyName("handshake_failures")]
+    public long HandshakeFailures { get; set; }
+
+    [JsonPropertyName("handshake_timeouts")]
+    public long HandshakeTimeouts { get; set; }
+
+    [JsonPropertyName("handshake_p95_ms")]
+    public double? HandshakeP95Ms { get; set; }
+
+    [JsonPropertyName("handshake_sample_count")]
+    public long HandshakeSampleCount { get; set; }
+
+    /// <summary>QUIC packet-loss estimate from MsQuic's non-spurious loss counters; not Datagram application loss or retransmission.</summary>
+    [JsonPropertyName("transport_packet_loss_rate")]
+    public double? TransportPacketLossRate { get; set; }
+
+    [JsonPropertyName("transport_packets_sent")]
+    public ulong? TransportPacketsSent { get; set; }
+
+    [JsonPropertyName("transport_congestion_events")]
+    public uint? TransportCongestionEvents { get; set; }
+
+    [JsonPropertyName("transport_ecn_congestion_events")]
+    public uint? TransportEcnCongestionEvents { get; set; }
+
+    [JsonPropertyName("path_mtu")]
+    public ushort? PathMtu { get; set; }
+}
+
 /// <summary>Probe 的 <c>fleet.hello</c> 附加字段：系统、架构和构建信息（只用于展示和更新）。</summary>
 public sealed class ProbeHelloMeta
 {
@@ -345,8 +401,11 @@ public sealed class AgentHelloMeta
     [JsonPropertyName("probe_tcp_port")]
     public int? ProbeTcpPort { get; set; }
 
+    [JsonPropertyName("probe_quic_ports")]
+    public List<int>? ProbeQuicPorts { get; set; }
+
     [JsonPropertyName("probe_udp_ports")]
-    public List<int>? ProbeUdpPorts { get; set; }
+    public List<int>? LegacyProbeUdpPorts { get; set; }
 
     [JsonPropertyName("local_limits")]
     public LocalLimits? LocalLimits { get; set; }
@@ -482,8 +541,11 @@ public sealed class LineTaskSet
     public List<LineTask> Tasks { get; set; } = [];
 
     /// <summary>Agent 的数据面端口（Probe 把包发到这里）。</summary>
+    [JsonPropertyName("quic_ports")]
+    public List<int> QuicPorts { get; set; } = [];
+
     [JsonPropertyName("udp_ports")]
-    public List<int> UdpPorts { get; set; } = [];
+    public List<int> LegacyUdpPorts { get; set; } = [];
 
     [JsonPropertyName("tcp_ports")]
     public List<int> TcpPorts { get; set; } = [];
diff --git a/backend/shared/MoShiro.Protocol/Wire/UdpPacket.cs b/backend/shared/MoShiro.Protocol/Wire/MeasurementDatagram.cs
similarity index 84%
rename from backend/shared/MoShiro.Protocol/Wire/UdpPacket.cs
rename to backend/shared/MoShiro.Protocol/Wire/MeasurementDatagram.cs
index 737b57c..e0c829b 100644
--- a/backend/shared/MoShiro.Protocol/Wire/UdpPacket.cs
+++ b/backend/shared/MoShiro.Protocol/Wire/MeasurementDatagram.cs
@@ -3,7 +3,7 @@ using System.Security.Cryptography;
 
 namespace MoShiro.Protocol;
 
-public enum UdpPacketType : byte
+public enum MeasurementDatagramType : byte
 {
     EchoRequest = 1,
     EchoReply = 2,
@@ -12,7 +12,7 @@ public enum UdpPacketType : byte
     Data = 3,
 }
 
-public readonly record struct UdpHeader(UdpPacketType Type, long SessionId, uint StreamId, uint Seq, long SendTsUs);
+public readonly record struct MeasurementDatagramHeader(MeasurementDatagramType Type, long SessionId, uint StreamId, uint Seq, long SendTsUs);
 
 /// <summary>
 /// 数据面的 UDP 包（Fleet 之外的线格式）：
@@ -20,7 +20,7 @@ public readonly record struct UdpHeader(UdpPacketType Type, long SessionId, uint
 /// mac = HMAC-SHA256(session_key, 前面全部字节) 截断到 16 字节。所有整数小端。
 /// 接收方对不合法的包静默丢弃并计数，不回复（防放大）。
 /// </summary>
-public static class UdpPacket
+public static class MeasurementDatagram
 {
     public const ushort Magic = 0x4D4E; // "MN"
     public const byte Version = 1;
@@ -30,19 +30,19 @@ public static class UdpPacket
     public const int MaxBytes = 1472;
 
     /// <summary>检查长度、magic、version、type 并解析头部（不校验 MAC）。</summary>
-    public static bool TryParseHeader(ReadOnlySpan<byte> packet, out UdpHeader header)
+    public static bool TryParseHeader(ReadOnlySpan<byte> packet, out MeasurementDatagramHeader header)
     {
         header = default;
         if (packet.Length is < MinBytes or > MaxBytes
             || BinaryPrimitives.ReadUInt16LittleEndian(packet) != Magic
             || packet[2] != Version
-            || packet[3] is < (byte)UdpPacketType.EchoRequest or > (byte)UdpPacketType.Data)
+            || packet[3] is < (byte)MeasurementDatagramType.EchoRequest or > (byte)MeasurementDatagramType.Data)
         {
             return false;
         }
 
-        header = new UdpHeader(
-            (UdpPacketType)packet[3],
+        header = new MeasurementDatagramHeader(
+            (MeasurementDatagramType)packet[3],
             BinaryPrimitives.ReadInt64LittleEndian(packet[4..]),
             BinaryPrimitives.ReadUInt32LittleEndian(packet[12..]),
             BinaryPrimitives.ReadUInt32LittleEndian(packet[16..]),
@@ -51,7 +51,7 @@ public static class UdpPacket
     }
 
     /// <summary>写入整个包（长度就是 <paramref name="destination"/> 的长度），填充为零，末尾是 MAC。</summary>
-    public static void Write(Span<byte> destination, in UdpHeader header, ReadOnlySpan<byte> key)
+    public static void Write(Span<byte> destination, in MeasurementDatagramHeader header, ReadOnlySpan<byte> key)
     {
         if (destination.Length is < MinBytes or > MaxBytes)
         {
diff --git a/backend/shared/MoShiro.Protocol/Wire/TcpWire.cs b/backend/shared/MoShiro.Protocol/Wire/TcpWire.cs
index b03a5b3..2b18ca7 100644
--- a/backend/shared/MoShiro.Protocol/Wire/TcpWire.cs
+++ b/backend/shared/MoShiro.Protocol/Wire/TcpWire.cs
@@ -19,8 +19,8 @@ public static class TcpWire
 
     public static void WriteAuth(Span<byte> destination, long sessionId, uint streamId, ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> key)
     {
-        BinaryPrimitives.WriteUInt16LittleEndian(destination, UdpPacket.Magic);
-        destination[2] = UdpPacket.Version;
+        BinaryPrimitives.WriteUInt16LittleEndian(destination, MeasurementDatagram.Magic);
+        destination[2] = MeasurementDatagram.Version;
         BinaryPrimitives.WriteInt64LittleEndian(destination[3..], sessionId);
         BinaryPrimitives.WriteUInt32LittleEndian(destination[11..], streamId);
         nonce[..NonceBytes].CopyTo(destination[15..]);
@@ -35,7 +35,7 @@ public static class TcpWire
         sessionId = 0;
         streamId = 0;
         nonce = default;
-        if (frame.Length != AuthBytes || BinaryPrimitives.ReadUInt16LittleEndian(frame) != UdpPacket.Magic || frame[2] != UdpPacket.Version)
+        if (frame.Length != AuthBytes || BinaryPrimitives.ReadUInt16LittleEndian(frame) != MeasurementDatagram.Magic || frame[2] != MeasurementDatagram.Version)
         {
             return false;
         }
diff --git a/backend/shared/tests/MoShiro.Measurement.Tests/MeasurementTests.cs b/backend/shared/tests/MoShiro.Measurement.Tests/MeasurementTests.cs
index 1912f09..d0f301b 100644
--- a/backend/shared/tests/MoShiro.Measurement.Tests/MeasurementTests.cs
+++ b/backend/shared/tests/MoShiro.Measurement.Tests/MeasurementTests.cs
@@ -16,7 +16,7 @@ public sealed class MeasurementTests
         Params = parameters.ToDictionary(p => p.Key, p => Json(p.Raw)),
     };
 
-    private static BudgetGuard Guard(NodeLimits? limits = null) => new(limits ?? new NodeLimits { AllowedUdpPorts = [7443], AllowedTcpPorts = [7444] }, BlockCatalog.AgentKinds);
+    private static BudgetGuard Guard(NodeLimits? limits = null) => new(limits ?? new NodeLimits { AllowedQuicPorts = [7443], AllowedTcpPorts = [7444] }, BlockCatalog.AgentKinds);
 
     [Fact]
     public void BudgetGuard_AcceptsDefaults_RejectsUnknownKindsBadParamsAndForeignPorts()
@@ -34,7 +34,7 @@ public sealed class MeasurementTests
     [Fact]
     public void BudgetGuard_AccumulatesTheBudget_AndRejectsWhatDoesNotFit()
     {
-        BudgetGuard guard = Guard(new NodeLimits { MaxTotalMbps = 15, AllowedUdpPorts = [7443] });
+        BudgetGuard guard = Guard(new NodeLimits { MaxTotalMbps = 15, AllowedQuicPorts = [7443] });
         double mbps = 0;
         long pps = 0;
         Assert.True(guard.CheckPhase("udp_train", new Dictionary<string, JsonElement> { ["mbps"] = Json("10") }).Accepted);
@@ -298,7 +298,7 @@ public sealed class MeasurementTests
     [Fact]
     public void EchoRows_Udp_GivesUpOnAMissingReplyAfterTwoSeconds()
     {
-        var rows = new EchoRows(Kinds.UdpEcho, 64, EchoRows.UdpGraceUs, settleOnReply: false);
+        var rows = new EchoRows(Kinds.UdpEcho, 64, EchoRows.DatagramGraceUs, settleOnReply: false);
         rows.Add(64, 0);
         rows.Add(64, 1_000_000);
         RawStream cut = rows.Take(2_500_000, all: false)!;
diff --git a/backend/src/MoShiro.Backend.Analysis/Metrics/LinkMetrics.cs b/backend/src/MoShiro.Backend.Analysis/Metrics/LinkMetrics.cs
index 090686e..31e094b 100644
--- a/backend/src/MoShiro.Backend.Analysis/Metrics/LinkMetrics.cs
+++ b/backend/src/MoShiro.Backend.Analysis/Metrics/LinkMetrics.cs
@@ -26,10 +26,18 @@ public static class LinkMetrics
         "jitter.down", s_udpMsg, Ops.OwdVar(Dir.Down), "Jitter (down)", "One-way delay variation, offset and drift removed.", Unit.Ms, [Stat.P95], good: 3, poor: 20);
 
     public static readonly MetricDef LossRun = Metric.RunLength(
-        "loss.run", s_udpMsg, Ops.LossRuns, "Loss runs", "Lengths of consecutive lost packets.",
+        "loss.run", s_udpMsg, Ops.LossRuns(Dir.Down), "Loss runs (legacy downstream alias)", "Legacy downstream-only consecutive loss metric.",
         new MetricExport("loss.run_max", Stat.Max, Unit.Packets, 2, 10),
         new MetricExport("loss.run_mean", Stat.Mean, Unit.Packets));
 
+    public static readonly MetricDef LossRunUp = Metric.Max(
+        "loss.run.up", s_udpMsg, Ops.LossRunMax(Dir.Up), "Upstream longest loss run", "Longest consecutive Probe-to-Agent Datagram loss run in each chunk; zero means no loss.",
+        Unit.Packets, "loss.run.up_max", good: 0, poor: 10);
+
+    public static readonly MetricDef LossRunDown = Metric.Max(
+        "loss.run.down", s_udpMsg, Ops.LossRunMax(Dir.Down), "Downstream longest loss run", "Longest consecutive Agent-to-Probe Datagram loss run in each chunk, conditioned on the request reaching the Agent; zero means no loss.",
+        Unit.Packets, "loss.run.down_max", good: 0, poor: 10);
+
     public static readonly MetricDef Reorder = Metric.Counter(
         "reorder", s_udpMsg, Ops.Reorder, "Reordered", "Replies that arrived after a higher sequence number.", new MetricExport("reorder", Stat.Count, Unit.Count));
 
diff --git a/backend/src/MoShiro.Backend.Analysis/Metrics/MetricRegistry.cs b/backend/src/MoShiro.Backend.Analysis/Metrics/MetricRegistry.cs
index e332a84..79dbd57 100644
--- a/backend/src/MoShiro.Backend.Analysis/Metrics/MetricRegistry.cs
+++ b/backend/src/MoShiro.Backend.Analysis/Metrics/MetricRegistry.cs
@@ -11,7 +11,7 @@ public static class MetricRegistry
     public static readonly IReadOnlyList<MetricDef> All =
     [
         LinkMetrics.Rtt, LinkMetrics.LossUp, LinkMetrics.LossDown, LinkMetrics.LossTotal,
-        LinkMetrics.JitterUp, LinkMetrics.JitterDown, LinkMetrics.LossRun, LinkMetrics.Reorder, LinkMetrics.Dup, LinkMetrics.SamplesUdp,
+        LinkMetrics.JitterUp, LinkMetrics.JitterDown, LinkMetrics.LossRun, LinkMetrics.LossRunUp, LinkMetrics.LossRunDown, LinkMetrics.Reorder, LinkMetrics.Dup, LinkMetrics.SamplesUdp,
         TcpMetrics.Rtt, TcpMetrics.Slow, TcpMetrics.Stall, TcpMetrics.StallMax, TcpMetrics.Retrans, TcpMetrics.Srtt, TcpMetrics.BulkRate, TcpMetrics.BulkPeak, TcpMetrics.SamplesTcp,
         SessionMetrics.ConnectSuccess, SessionMetrics.ConnectTcp, SessionMetrics.ConnectTls,
         SessionMetrics.FailTimeout, SessionMetrics.FailReset, SessionMetrics.FailTls,
@@ -22,7 +22,8 @@ public static class MetricRegistry
     /// <summary>指标分组：前端按分组展示，新增指标只需要把它加进分组。</summary>
     public static readonly IReadOnlyList<PresetDef> Presets =
     [
-        new("udp", "UDP", ["loss.up", "loss.down", "loss.total", "rtt.p50", "rtt.p95", "rtt.p99", "jitter.up.p95", "jitter.down.p95", "loss.run_max", "reorder", "dup"]),
+        new("quic", "QUIC Datagram", ["loss.up", "loss.down", "loss.total", "rtt.p50", "rtt.p95", "rtt.p99", "jitter.up.p95", "jitter.down.p95", "loss.run.up_max", "loss.run.down_max", "reorder", "dup"]),
+        new("udp", "QUIC Datagram (legacy alias)", ["loss.up", "loss.down", "loss.total", "rtt.p50", "rtt.p95", "rtt.p99", "jitter.up.p95", "jitter.down.p95", "loss.run_max", "reorder", "dup"]),
         new("tcp", "TCP", ["tcp.rtt.p50", "tcp.rtt.p95", "tcp.rtt.p99", "tcp.rtt.p999", "tcp.rtt.max", "tcp.rtt.tail", "tcp.slow", "tcp.stall.per_min", "tcp.stall_max", "tcp.retrans", "tcp.srtt.p95"]),
         new("connect", "Connect", ["connect.success", "connect.tcp_ms.p95", "connect.tls_ms.p95", "connect.fail.timeout", "connect.fail.rst", "connect.fail.tls"]),
         new("session", "Session", ["hold.resets.per_h", "hold.lifetime_max"]),
diff --git a/backend/src/MoShiro.Backend.Analysis/Metrics/SessionMetrics.cs b/backend/src/MoShiro.Backend.Analysis/Metrics/SessionMetrics.cs
index 6f5acbb..66abca1 100644
--- a/backend/src/MoShiro.Backend.Analysis/Metrics/SessionMetrics.cs
+++ b/backend/src/MoShiro.Backend.Analysis/Metrics/SessionMetrics.cs
@@ -1,6 +1,6 @@
 namespace MoShiro.Backend.Analysis;
 
-/// <summary>连接建立、长连接、UDP 压测（udp_train）的指标。</summary>
+/// <summary>TCP 建连、长连接、QUIC Datagram 压测（legacy kind udp_train）的指标。</summary>
 public static class SessionMetrics
 {
     private static readonly string[] s_conn = ["connect.conn"];
@@ -33,13 +33,13 @@ public static class SessionMetrics
         "hold.lifetime", s_hold, Ops.HoldLifetime, "Longest connection lifetime", "Longest observed lifetime of the held connection (ms).", Unit.Ms, "hold.lifetime_max", Better.Higher);
 
     public static readonly MetricDef TrainLoss = Metric.Ratio(
-        "train.loss", s_train, Ops.TrainLoss, "Train loss", "Loss of a fixed-rate UDP stream.", good: 1, poor: 10);
+        "train.loss", s_train, Ops.TrainLoss, "Datagram train loss", "Loss of a fixed-rate QUIC Datagram stream.", good: 1, poor: 10);
 
     public static readonly MetricDef TrainJitter = Metric.Histogram(
-        "train.jitter", s_train, Ops.TrainJitter, "Train jitter", "One-way delay variation of a fixed-rate UDP stream.", Unit.Ms, [Stat.P95], good: 3, poor: 20);
+        "train.jitter", s_train, Ops.TrainJitter, "Datagram train delay variation", "One-way delay variation of a fixed-rate QUIC Datagram stream.", Unit.Ms, [Stat.P95], good: 3, poor: 20);
 
     public static readonly MetricDef TrainRate = Metric.Histogram(
-        "train.rate", s_train, Ops.TrainRate, "Train rate", "Delivered rate of a fixed-rate UDP stream per second.", Unit.Mbps, [Stat.P50, Stat.Mean], Better.Higher);
+        "train.rate", s_train, Ops.TrainRate, "Datagram train rate", "Delivered rate of a fixed-rate QUIC Datagram stream per second.", Unit.Mbps, [Stat.P50, Stat.Mean], Better.Higher);
 
     public static readonly MetricDef SamplesConnect = Metric.Counter(
         "n.connect", s_conn, Ops.RowCount, "connect samples", "Number of connection attempts.", new MetricExport("n.connect", Stat.Count, Unit.Count), Better.None);
diff --git a/backend/src/MoShiro.Backend.Analysis/Models/Models.cs b/backend/src/MoShiro.Backend.Analysis/Models/Models.cs
index aeb9825..383d470 100644
--- a/backend/src/MoShiro.Backend.Analysis/Models/Models.cs
+++ b/backend/src/MoShiro.Backend.Analysis/Models/Models.cs
@@ -12,9 +12,9 @@ public sealed class BaseModel : ServiceModelBase
 
     public override string Title => "Line quality";
 
-    public override int Version => 1;
+    public override int Version => 2;
 
-    public override IReadOnlyList<string> Needs { get; } = ["rtt.p95", "loss.total", "jitter.down.p95", "jitter.up.p95", "loss.run_max"];
+    public override IReadOnlyList<string> Needs { get; } = ["rtt.p95", "loss.total", "jitter.down.p95", "jitter.up.p95", "loss.run.up_max", "loss.run.down_max"];
 
     public override ModelScore Score(MetricView view) =>
         Combine(
@@ -24,7 +24,8 @@ public sealed class BaseModel : ServiceModelBase
                 Dim(view, "loss.total", "Packet loss", 4, s_loss),
                 Dim(view, "jitter.down.p95", "Jitter (down)", 1.5, s_jitter),
                 Dim(view, "jitter.up.p95", "Jitter (up)", 1.5, s_jitter),
-                Dim(view, "loss.run_max", "Longest loss run", 1, s_run),
+                Dim(view, "loss.run.up_max", "Longest upstream loss run", 0.5, s_run),
+                Dim(view, "loss.run.down_max", "Longest downstream loss run", 0.5, s_run),
             ],
             estimated: false);
 }
diff --git a/backend/src/MoShiro.Backend.Analysis/Ops/EchoOps.cs b/backend/src/MoShiro.Backend.Analysis/Ops/EchoOps.cs
index f160ef9..e52be7c 100644
--- a/backend/src/MoShiro.Backend.Analysis/Ops/EchoOps.cs
+++ b/backend/src/MoShiro.Backend.Analysis/Ops/EchoOps.cs
@@ -273,7 +273,14 @@ internal static class JitterEmitter
 /// <summary>连续丢失段的长度（按发送顺序）。</summary>
 internal sealed class LossRunsOp : MetricOp
 {
-    public override string Signature => "loss_runs/1";
+    private readonly Dir _direction;
+
+    public LossRunsOp(Dir direction)
+    {
+        _direction = direction;
+    }
+
+    public override string Signature => $"loss_runs/{_direction}/2";
 
     public override void Evaluate(ChunkView view, RawStream stream, IObservationSink sink)
     {
@@ -292,7 +299,13 @@ internal sealed class LossRunsOp : MetricOp
                 continue;
             }
 
-            if (c.IsReplyLost(i))
+            bool lost = _direction switch
+            {
+                Dir.Up => c.IsUpLost(i),
+                Dir.Down => !c.IsUpLost(i) && c.IsReplyLost(i),
+                _ => c.IsReplyLost(i),
+            };
+            if (lost)
             {
                 if (run == 0)
                 {
@@ -315,6 +328,59 @@ internal sealed class LossRunsOp : MetricOp
     }
 }
 
+/// <summary>每个块一个最长连续丢包值；无丢包的有效块明确输出 0。</summary>
+internal sealed class LossRunMaxOp(Dir direction) : MetricOp
+{
+    public override string Signature => $"loss_run_max/{direction}/1";
+
+    public override void Evaluate(ChunkView view, RawStream stream, IObservationSink sink)
+    {
+        var c = new EchoColumns(stream);
+        if (!c.HasBasics || (direction != Dir.Total && c.T2 is null))
+        {
+            return;
+        }
+
+        int run = 0;
+        int maximum = 0;
+        bool hasSample = false;
+        long sampleAt = 0;
+        for (int i = 0; i < c.Count; i++)
+        {
+            if (!c.T1!.IsValid(i))
+            {
+                continue;
+            }
+
+            bool lost = direction switch
+            {
+                Dir.Up => c.IsUpLost(i),
+                Dir.Down => !c.IsUpLost(i) && c.IsReplyLost(i),
+                _ => c.IsReplyLost(i),
+            };
+            if (direction == Dir.Down && c.IsUpLost(i))
+            {
+                // A request lost before reaching the Agent is not a downstream sample.
+                run = 0;
+                continue;
+            }
+
+            if (!hasSample)
+            {
+                sampleAt = c.SentUtcMs(view, i);
+                hasSample = true;
+            }
+            run = lost ? run + 1 : 0;
+            maximum = Math.Max(maximum, run);
+        }
+
+        if (hasSample)
+        {
+            sink.Emit(sampleAt, maximum);
+        }
+    }
+}
+
 /// <summary>乱序：按到达顺序，序号比之前见过的最大序号还小。重复的序号不算乱序。</summary>
 internal sealed class ReorderOp : MetricOp
 {
diff --git a/backend/src/MoShiro.Backend.Analysis/Ops/Ops.cs b/backend/src/MoShiro.Backend.Analysis/Ops/Ops.cs
index ab9ecd1..0755942 100644
--- a/backend/src/MoShiro.Backend.Analysis/Ops/Ops.cs
+++ b/backend/src/MoShiro.Backend.Analysis/Ops/Ops.cs
@@ -11,7 +11,9 @@ public static class Ops
 
     public static MetricOp OwdVar(Dir dir) => new OwdVarOp(dir);
 
-    public static MetricOp LossRuns { get; } = new LossRunsOp();
+    public static MetricOp LossRuns(Dir direction) => new LossRunsOp(direction);
+
+    public static MetricOp LossRunMax(Dir direction) => new LossRunMaxOp(direction);
 
     public static MetricOp Reorder { get; } = new ReorderOp();
 
diff --git a/backend/src/MoShiro.Backend.Api/Common/Mappers.cs b/backend/src/MoShiro.Backend.Api/Common/Mappers.cs
index 95d8b6e..c01ee40 100644
--- a/backend/src/MoShiro.Backend.Api/Common/Mappers.cs
+++ b/backend/src/MoShiro.Backend.Api/Common/Mappers.cs
@@ -31,7 +31,23 @@ public static class Mappers
     public static OverviewLineDto ToDto(OverviewLine line) =>
         new(
             line.Line.Key.Id, line.Line.Agent.Agent.Id.Value, line.Line.Probe.Id, line.Line.Probe.Name, line.Line.Agent.Agent.Name, line.Line.Agent.Agent.Labels,
-            line.Line.Agent.Online, line.Line.Connected, line.Line.Agent.EndpointChanges, ToDto(line.Summary), Summary(line.LastTest), line.Line.IpVersion);
+            line.Line.Agent.Online, line.Line.Connected, line.Line.Agent.EndpointChanges, ToDto(line.Summary), Summary(line.LastTest), line.Line.IpVersion, ToDto(line.Line.QuicHealth));
+
+    public static QuicLineHealthDto? ToDto(ProbeQuicLinkSnapshot? snapshot)
+    {
+        if (snapshot is null)
+        {
+            return null;
+        }
+
+        ProbeQuicLinkHealth health = snapshot.Health;
+        double? Rate(long count) => health.HandshakeAttempts > 0 ? count * 100.0 / health.HandshakeAttempts : null;
+        return new QuicLineHealthDto(
+            health.Connected, health.HandshakeAttempts, health.HandshakeSuccesses, health.HandshakeFailures, health.HandshakeTimeouts,
+            Rate(health.HandshakeSuccesses), Rate(health.HandshakeFailures), Rate(health.HandshakeTimeouts), health.HandshakeP95Ms, health.HandshakeSampleCount,
+            health.TransportPacketLossRate, health.TransportPacketsSent, health.TransportCongestionEvents,
+            health.TransportEcnCongestionEvents, health.PathMtu, Time(snapshot.AtMs));
+    }
 
     public static HostDto ToDto(HostSnapshot h) =>
         new(h.CpuPercent, h.MemUsed, h.MemTotal, h.DiskUsed, h.DiskTotal, h.NetRxTotal, h.NetTxTotal, h.NetRxBps, h.NetTxBps, h.NetLinkMbps, h.UptimeSeconds, Time(h.AtUtcMs));
@@ -102,7 +118,7 @@ public static class Mappers
             ? new HeartbeatDto(h.Sessions, h.PpsIn, h.PpsOut, h.DroppedInvalid, h.DroppedRateLimited, h.QueueBytes, Time(view.HeartbeatAtMs ?? 0))
             : null;
         return new AgentDto(
-            a.Id.Value, a.Name, StatusName(a.Status), view.Online, view.ProbeConnected, [.. view.Probes.Select(ToDto)], view.Host is null ? null : ToDto(view.Host), a.PublicHost, a.ProbeTcpPort, a.ProbeUdpPorts, a.Labels, a.PublicVisible,
+            a.Id.Value, a.Name, StatusName(a.Status), view.Online, view.ProbeConnected, [.. view.Probes.Select(ToDto)], view.Host is null ? null : ToDto(view.Host), a.PublicHost, a.ProbeTcpPort, a.ProbeUdpPorts, a.ProbeUdpPorts, a.Labels, a.PublicVisible,
             a.Kinds, a.AgentVersion, limits, a.TaskVersion, a.AppliedTaskVersion, rejected, heartbeat, view.EndpointChanges, Time(a.CreatedAtMs), Time(a.LastSeenAtMs), a.Ipv6Host, a.Ipv6Supported, Ipv6Of(view), !a.PublicHostManual, !a.Ipv6HostManual, a.AddedBy);
     }
 
diff --git a/backend/src/MoShiro.Backend.Api/Contracts/AdminDtos.cs b/backend/src/MoShiro.Backend.Api/Contracts/AdminDtos.cs
index 1818308..a9e00b8 100644
--- a/backend/src/MoShiro.Backend.Api/Contracts/AdminDtos.cs
+++ b/backend/src/MoShiro.Backend.Api/Contracts/AdminDtos.cs
@@ -42,6 +42,7 @@ public sealed record AgentDto(
     string PublicHost,
     int ProbeTcpPort,
     IReadOnlyList<int> ProbeUdpPorts,
+    IReadOnlyList<int> ProbeQuicPorts,
     IReadOnlyList<string> Labels,
     bool PublicVisible,
     IReadOnlyList<string> Kinds,
diff --git a/backend/src/MoShiro.Backend.Api/Contracts/ApiJsonContext.cs b/backend/src/MoShiro.Backend.Api/Contracts/ApiJsonContext.cs
index 54ae57c..d466561 100644
--- a/backend/src/MoShiro.Backend.Api/Contracts/ApiJsonContext.cs
+++ b/backend/src/MoShiro.Backend.Api/Contracts/ApiJsonContext.cs
@@ -22,6 +22,7 @@ namespace MoShiro.Backend.Api;
 [JsonSerializable(typeof(DistributionDto))]
 [JsonSerializable(typeof(HeatmapDto))]
 [JsonSerializable(typeof(LineDto))]
+[JsonSerializable(typeof(QuicLineHealthDto))]
 [JsonSerializable(typeof(TestDto))]
 [JsonSerializable(typeof(PageDto<TestDto>))]
 [JsonSerializable(typeof(PageDto<KindDto>))]
diff --git a/backend/src/MoShiro.Backend.Api/Contracts/PublicDtos.cs b/backend/src/MoShiro.Backend.Api/Contracts/PublicDtos.cs
index 318c514..cde6f11 100644
--- a/backend/src/MoShiro.Backend.Api/Contracts/PublicDtos.cs
+++ b/backend/src/MoShiro.Backend.Api/Contracts/PublicDtos.cs
@@ -28,7 +28,27 @@ public sealed record OverviewLineDto(
     int EndpointChanges,
     SummaryDto Summary,
     TestSummaryDto? LastTest,
-    string IpVersion = "ipv4");
+    string IpVersion = "ipv4",
+    QuicLineHealthDto? QuicHealth = null);
+
+/// <summary>Latest QUIC session health reported by the Probe; cumulative counters reset when the Probe restarts.</summary>
+public sealed record QuicLineHealthDto(
+    bool Connected,
+    long HandshakeAttempts,
+    long HandshakeSuccesses,
+    long HandshakeFailures,
+    long HandshakeTimeouts,
+    double? HandshakeSuccessRate,
+    double? HandshakeFailureRate,
+    double? HandshakeTimeoutRate,
+    double? HandshakeP95Ms,
+    long HandshakeSampleCount,
+    double? TransportPacketLossRate,
+    ulong? TransportPacketsSent,
+    uint? TransportCongestionEvents,
+    uint? TransportEcnCongestionEvents,
+    ushort? PathMtu,
+    DateTimeOffset At);
 
 public sealed record OverviewDto(string Range, DateTimeOffset From, DateTimeOffset To, string Step, string Source, bool Degraded, IReadOnlyList<OverviewLineDto> Lines);
 
@@ -90,7 +110,8 @@ public sealed record LineDto(
     IReadOnlyList<string> Kinds,
     TestSummaryDto? LastTest,
     string IpVersion = "ipv4",
-    bool Ipv6Available = false);
+    bool Ipv6Available = false,
+    QuicLineHealthDto? QuicHealth = null);
 
 public sealed record DimensionDto(string Id, string Label, double Weight, double? Value, double? Score);
 
diff --git a/backend/src/MoShiro.Backend.Api/Public/QueryEndpoints.cs b/backend/src/MoShiro.Backend.Api/Public/QueryEndpoints.cs
index e459f98..4de3589 100644
--- a/backend/src/MoShiro.Backend.Api/Public/QueryEndpoints.cs
+++ b/backend/src/MoShiro.Backend.Api/Public/QueryEndpoints.cs
@@ -13,8 +13,8 @@ namespace MoShiro.Backend.Api;
 public static class QueryEndpoints
 {
     private const string Tag = "public";
-    private const string DefaultOverviewPreset = "udp,tcp,scores";
-    private const string DefaultSeriesPreset = "udp,tcp";
+    private const string DefaultOverviewPreset = "quic,tcp,scores";
+    private const string DefaultSeriesPreset = "quic,tcp";
 
     public static void Map(RouteGroupBuilder group)
     {
@@ -102,7 +102,7 @@ public static class QueryEndpoints
         return TypedResults.Json(
             new LineDto(
                 line.Key.Id, view.Agent.Id.Value, line.Probe.Id, line.Probe.Name, view.Agent.Name, view.Agent.Labels, view.Online, line.Connected,
-                Mappers.Time(await query.EarliestAsync(line.Key, ct)), view.Agent.Kinds, Mappers.Summary(last), line.IpVersion, view.Agent.Ipv6Host.Length > 0),
+                Mappers.Time(await query.EarliestAsync(line.Key, ct)), view.Agent.Kinds, Mappers.Summary(last), line.IpVersion, view.Agent.Ipv6Host.Length > 0, Mappers.ToDto(line.QuicHealth)),
             ApiJsonContext.Default.LineDto);
     }
 
diff --git a/backend/src/MoShiro.Backend.Application/Agents/AgentService.cs b/backend/src/MoShiro.Backend.Application/Agents/AgentService.cs
index 462fa5b..9a616be 100644
--- a/backend/src/MoShiro.Backend.Application/Agents/AgentService.cs
+++ b/backend/src/MoShiro.Backend.Application/Agents/AgentService.cs
@@ -173,7 +173,8 @@ public sealed partial class AgentService
                 Host = agent.PublicHost,
                 Ipv6Host = agent.Ipv6Supported && agent.Ipv6Host.Length > 0 ? agent.Ipv6Host : null,
                 TcpPort = agent.ProbeTcpPort,
-                UdpPorts = [.. agent.ProbeUdpPorts],
+                QuicPorts = [.. agent.ProbeUdpPorts],
+                LegacyUdpPorts = [.. agent.ProbeUdpPorts],
                 PublicKey = Convert.ToBase64String(agent.TlsPublicKey!),
             });
         }
diff --git a/backend/src/MoShiro.Backend.Application/Agents/MoShiroFleetHooks.cs b/backend/src/MoShiro.Backend.Application/Agents/MoShiroFleetHooks.cs
index 769a26e..d1ed0ee 100644
--- a/backend/src/MoShiro.Backend.Application/Agents/MoShiroFleetHooks.cs
+++ b/backend/src/MoShiro.Backend.Application/Agents/MoShiroFleetHooks.cs
@@ -43,7 +43,7 @@ public sealed class MoShiroEnrollmentHook : IEnrollmentHook
         // 注册请求带了 public_host 就用它；否则来源地址是公网地址时用来源地址（私网或隧道出口不用，等 hello 里的本机地址）
         string host = !string.IsNullOrWhiteSpace(meta.PublicHost) ? meta.PublicHost
             : System.Net.IPAddress.TryParse(context.RemoteIp, out System.Net.IPAddress? remote) && PublicAddress.IsPublicIpv4(remote) ? remote.ToString() : "";
-        await _agents.ApplyEnrollmentAsync(node.Id, new AgentEnrollment(host, meta.ProbeTcpPort, meta.ProbeUdpPorts, meta.Kinds), ct);
+        await _agents.ApplyEnrollmentAsync(node.Id, new AgentEnrollment(host, meta.ProbeTcpPort, meta.ProbeQuicPorts.Count > 0 ? meta.ProbeQuicPorts : meta.LegacyProbeUdpPorts ?? [7443], meta.Kinds), ct);
         if (await _agents.GetAsync(node.Id, ct) is { } enrolled)
         {
             (_, string? observedV6) = AgentAddressPolicy.Choose(enrolled, [], context.RemoteIp);
@@ -70,10 +70,12 @@ public sealed class MoShiroNodeEventSink : INodeEventSink
     private readonly ScheduleService _schedule;
     private readonly IProbeStore _probes;
     private readonly NodeOwnerService _owners;
+    private readonly ProbeQuicRuntime _quicRuntime;
 
-    public MoShiroNodeEventSink(IAgentStore agents, AgentRuntime runtime, IEventStore events, LiveHub live, AgentService service, NodeInfoService nodes, ReleaseService releases, ScheduleService schedule, IProbeStore probes, NodeOwnerService owners)
+    public MoShiroNodeEventSink(IAgentStore agents, AgentRuntime runtime, IEventStore events, LiveHub live, AgentService service, NodeInfoService nodes, ReleaseService releases, ScheduleService schedule, IProbeStore probes, NodeOwnerService owners, ProbeQuicRuntime quicRuntime)
     {
         _owners = owners;
+        _quicRuntime = quicRuntime;
         _releases = releases;
         _schedule = schedule;
         _probes = probes;
@@ -168,12 +170,17 @@ public sealed class MoShiroNodeEventSink : INodeEventSink
             case NodeEventKind.Offline:
                 _live.Publish(new NodeSignal("probe", id.Value, false, nodeEvent.AtMs));
                 _releases.RecordStatus(id, null);
+                _quicRuntime.MarkProbeOffline(id.Value, nodeEvent.AtMs);
                 break;
             case NodeEventKind.Heartbeat when nodeEvent.Extra is { } extra:
                 try
                 {
                     ProbeHeartbeatExtra? heartbeat = extra.Deserialize(MoShiroJsonContext.Default.ProbeHeartbeatExtra);
                     _releases.RecordStatus(id, heartbeat?.Update);
+                    if (heartbeat?.QuicLinks is { } quicLinks)
+                    {
+                        _quicRuntime.Replace(id.Value, nodeEvent.AtMs, quicLinks);
+                    }
                     if (heartbeat?.Ipv6 is { } ipv6)
                     {
                         await _probes.SetIpv6DiagnosticsAsync(id.Value, JsonSerializer.Serialize(ipv6, MoShiroJsonContext.Default.Ipv6Diagnostic), ct);
@@ -236,7 +243,8 @@ public sealed class MoShiroNodeEventSink : INodeEventSink
         AgentRecord? before = await _agents.GetAsync(id, ct);
         string? limitsJson = meta.LocalLimits is null ? null : JsonSerializer.Serialize(meta.LocalLimits, LocalLimitsJson.Default.LocalLimits);
         string? ipv6Json = meta.Ipv6 is null ? null : JsonSerializer.Serialize(meta.Ipv6, MoShiroJsonContext.Default.Ipv6Diagnostic);
-        await _agents.ApplyHelloAsync(id, new AgentHello(kinds, hello.NodeVersion, limitsJson, spki is { Length: 32 } ? spki : null, meta.ProbeTcpPort, meta.ProbeUdpPorts, meta.Ipv6Supported, ipv6Json, meta.Addresses, tlsKey), ct);
+        IReadOnlyList<int>? quicPorts = meta.ProbeQuicPorts is { Count: > 0 } ? meta.ProbeQuicPorts : meta.LegacyProbeUdpPorts;
+        await _agents.ApplyHelloAsync(id, new AgentHello(kinds, hello.NodeVersion, limitsJson, spki is { Length: 32 } ? spki : null, meta.ProbeTcpPort, quicPorts, meta.Ipv6Supported, ipv6Json, meta.Addresses, tlsKey), ct);
 
         // 自动识别对外地址：Agent 上报的公网地址；手填的不动
         if (meta.Addresses is not null && await _agents.GetAsync(id, ct) is { } reported)
diff --git a/backend/src/MoShiro.Backend.Application/Agents/ProbeQuicRuntime.cs b/backend/src/MoShiro.Backend.Application/Agents/ProbeQuicRuntime.cs
new file mode 100644
index 0000000..4958972
--- /dev/null
+++ b/backend/src/MoShiro.Backend.Application/Agents/ProbeQuicRuntime.cs
@@ -0,0 +1,56 @@
+using System.Collections.Concurrent;
+using MoShiro.Protocol;
+
+namespace MoShiro.Backend.Application;
+
+public sealed record ProbeQuicLinkSnapshot(ProbeQuicLinkHealth Health, long AtMs);
+
+/// <summary>Latest per-line QUIC health reported by connected Probes. Volatile runtime state, not historical metrics.</summary>
+public sealed class ProbeQuicRuntime
+{
+    private readonly ConcurrentDictionary<(string Probe, string Agent, string IpVersion), ProbeQuicLinkSnapshot> _links = new();
+
+    public ProbeQuicLinkSnapshot? Get(string probeId, string agentId, string ipVersion) =>
+        _links.TryGetValue((probeId, agentId, ipVersion), out ProbeQuicLinkSnapshot? snapshot) ? snapshot : null;
+
+    public void Replace(string probeId, long atMs, IReadOnlyList<ProbeQuicLinkHealth> links)
+    {
+        var current = new HashSet<(string Probe, string Agent, string IpVersion)>();
+        foreach (ProbeQuicLinkHealth link in links)
+        {
+            var key = (probeId, link.AgentId, link.IpVersion);
+            current.Add(key);
+            _links[key] = new ProbeQuicLinkSnapshot(link, atMs);
+        }
+
+        foreach ((string Probe, string Agent, string IpVersion) key in _links.Keys.Where(k => k.Probe == probeId && !current.Contains(k)))
+        {
+            _links.TryRemove(key, out _);
+        }
+    }
+
+    public void MarkProbeOffline(string probeId, long atMs)
+    {
+        foreach (KeyValuePair<(string Probe, string Agent, string IpVersion), ProbeQuicLinkSnapshot> pair in _links.ToArray().Where(p => p.Key.Probe == probeId))
+        {
+            ProbeQuicLinkHealth old = pair.Value.Health;
+            _links[pair.Key] = new ProbeQuicLinkSnapshot(new ProbeQuicLinkHealth
+            {
+                AgentId = old.AgentId,
+                IpVersion = old.IpVersion,
+                Connected = false,
+                HandshakeAttempts = old.HandshakeAttempts,
+                HandshakeSuccesses = old.HandshakeSuccesses,
+                HandshakeFailures = old.HandshakeFailures,
+                HandshakeTimeouts = old.HandshakeTimeouts,
+                HandshakeP95Ms = old.HandshakeP95Ms,
+                HandshakeSampleCount = old.HandshakeSampleCount,
+                TransportPacketLossRate = old.TransportPacketLossRate,
+                TransportPacketsSent = old.TransportPacketsSent,
+                TransportCongestionEvents = old.TransportCongestionEvents,
+                TransportEcnCongestionEvents = old.TransportEcnCongestionEvents,
+                PathMtu = old.PathMtu,
+            }, atMs);
+        }
+    }
+}
diff --git a/backend/src/MoShiro.Backend.Application/ApplicationServiceCollectionExtensions.cs b/backend/src/MoShiro.Backend.Application/ApplicationServiceCollectionExtensions.cs
index 0684571..9cb9651 100644
--- a/backend/src/MoShiro.Backend.Application/ApplicationServiceCollectionExtensions.cs
+++ b/backend/src/MoShiro.Backend.Application/ApplicationServiceCollectionExtensions.cs
@@ -16,6 +16,7 @@ public static class ApplicationServiceCollectionExtensions
         services.AddHostedService<StartupTasks>();
 
         services.AddSingleton<AgentRuntime>();
+        services.AddSingleton<ProbeQuicRuntime>();
         services.AddSingleton<LiveHub>();
         services.AddSingleton<HotLayer>();
         services.AddSingleton<BackendCounters>();
diff --git a/backend/src/MoShiro.Backend.Application/Query/Lines.cs b/backend/src/MoShiro.Backend.Application/Query/Lines.cs
index 63d20a1..c5b1d9b 100644
--- a/backend/src/MoShiro.Backend.Application/Query/Lines.cs
+++ b/backend/src/MoShiro.Backend.Application/Query/Lines.cs
@@ -25,7 +25,7 @@ public readonly record struct LineKey(NodeId Agent, ProbeId Probe, string IpVers
 }
 
 /// <summary>一条线路的展示视图：Agent 的状态、Probe 记录，以及这一对现在是否连着。</summary>
-public sealed record LineView(AgentView Agent, ProbeRecord Probe, string IpVersion = IpVersions.V4)
+public sealed record LineView(AgentView Agent, ProbeRecord Probe, string IpVersion = IpVersions.V4, ProbeQuicLinkSnapshot? QuicHealth = null)
 {
     public LineKey Key => new(Agent.Agent.Id, new ProbeId(Probe.Id), IpVersion);
 
@@ -40,12 +40,14 @@ public sealed class LineService
     private readonly AgentService _agents;
     private readonly IProbeStore _probes;
     private readonly LinkService _links;
+    private readonly ProbeQuicRuntime _quicRuntime;
 
-    public LineService(AgentService agents, IProbeStore probes, LinkService links)
+    public LineService(AgentService agents, IProbeStore probes, LinkService links, ProbeQuicRuntime quicRuntime)
     {
         _links = links;
         _agents = agents;
         _probes = probes;
+        _quicRuntime = quicRuntime;
     }
 
     /// <summary>所有线路：每个 Agent 和每个<b>未吊销</b>的 Probe 配成一对，只留下线路开着的（见 <see cref="LinkService"/>）；关掉的线路历史数据还在，按 id 仍然查得到。</summary>
@@ -59,10 +61,10 @@ public sealed class LineService
         {
             foreach (ProbeRecord probe in probes.Where(p => links.IsLinked(p.Id, agent.Agent.Id.Value)))
             {
-                result.Add(new LineView(agent, probe));
+                result.Add(new LineView(agent, probe, IpVersions.V4, _quicRuntime.Get(probe.Id, agent.Agent.Id.Value, IpVersions.V4)));
                 if (agent.Agent.Ipv6Host.Length > 0)
                 {
-                    result.Add(new LineView(agent, probe, IpVersions.V6));
+                    result.Add(new LineView(agent, probe, IpVersions.V6, _quicRuntime.Get(probe.Id, agent.Agent.Id.Value, IpVersions.V6)));
                 }
             }
         }
@@ -117,6 +119,6 @@ public sealed class LineService
             probe = active[0];
         }
 
-        return Result<LineView>.Ok(new LineView(agent, probe, ipVersion));
+        return Result<LineView>.Ok(new LineView(agent, probe, ipVersion, _quicRuntime.Get(probe.Id, agent.Agent.Id.Value, ipVersion)));
     }
 }
diff --git a/backend/src/MoShiro.Backend.Application/Tests/TestService.cs b/backend/src/MoShiro.Backend.Application/Tests/TestService.cs
index ad5efa5..bcc78f2 100644
--- a/backend/src/MoShiro.Backend.Application/Tests/TestService.cs
+++ b/backend/src/MoShiro.Backend.Application/Tests/TestService.cs
@@ -240,7 +240,7 @@ public sealed class TestService
             }
 
             // 没有指定端口的 UDP 阶段使用 Agent 上报的数据端口（目录里的默认值只是出厂默认，每个 Agent 可以改）
-            if (!merged.ContainsKey("port") && kind.Blocks.Transport == "udp" && kind.Params.Any(s => s.Name == "port") && agent.ProbeUdpPorts.Count > 0)
+            if (!merged.ContainsKey("port") && kind.Blocks.Transport == "quic_datagram" && kind.Params.Any(s => s.Name == "port") && agent.ProbeUdpPorts.Count > 0)
             {
                 merged["port"] = JsonSerializer.SerializeToElement(agent.ProbeUdpPorts[0], PlanPortJson.Default.Int32);
             }
diff --git a/backend/tests/MoShiro.Backend.Analysis.Tests/ModelAndTestEvaluatorTests.cs b/backend/tests/MoShiro.Backend.Analysis.Tests/ModelAndTestEvaluatorTests.cs
index 487311f..4f90ba2 100644
--- a/backend/tests/MoShiro.Backend.Analysis.Tests/ModelAndTestEvaluatorTests.cs
+++ b/backend/tests/MoShiro.Backend.Analysis.Tests/ModelAndTestEvaluatorTests.cs
@@ -40,8 +40,8 @@ public sealed class ModelAndTestEvaluatorTests
     [Fact]
     public void BaseModel_PerfectLine_ScoresHigh_AndBadLine_ScoresLow()
     {
-        double good = new BaseModel().Score(View(("rtt.p95", 25), ("loss.total", 0), ("jitter.down.p95", 1), ("jitter.up.p95", 1), ("loss.run_max", 1))).Score!.Value;
-        double bad = new BaseModel().Score(View(("rtt.p95", 400), ("loss.total", 12), ("jitter.down.p95", 90), ("jitter.up.p95", 90), ("loss.run_max", 40))).Score!.Value;
+        double good = new BaseModel().Score(View(("rtt.p95", 25), ("loss.total", 0), ("jitter.down.p95", 1), ("jitter.up.p95", 1), ("loss.run.up_max", 1), ("loss.run.down_max", 1))).Score!.Value;
+        double bad = new BaseModel().Score(View(("rtt.p95", 400), ("loss.total", 12), ("jitter.down.p95", 90), ("jitter.up.p95", 90), ("loss.run.up_max", 40), ("loss.run.down_max", 40))).Score!.Value;
         Assert.True(good > 95);
         Assert.True(bad < 10);
     }
@@ -83,7 +83,7 @@ public sealed class ModelAndTestEvaluatorTests
         var ranges = new Dictionary<string, double[]>
         {
             ["rtt.p95"] = [10, 30, 80, 150, 300, 600], ["loss.total"] = [0, 0.5, 1, 3, 10, 30],
-            ["jitter.down.p95"] = [0, 2, 8, 20, 80, 200], ["jitter.up.p95"] = [0, 2, 8, 20, 80, 200], ["loss.run_max"] = [1, 3, 10, 30, 60],
+            ["jitter.down.p95"] = [0, 2, 8, 20, 80, 200], ["jitter.up.p95"] = [0, 2, 8, 20, 80, 200], ["loss.run.up_max"] = [1, 3, 10, 30, 60], ["loss.run.down_max"] = [1, 3, 10, 30, 60],
             ["tcp.rtt.p95"] = [10, 40, 100, 200, 400, 800], ["tcp.stall.per_min"] = [0, 1, 5, 20, 60, 200], ["tcp.stall_max"] = [50, 150, 500, 2000, 5000],
             ["tcp.retrans"] = [0, 0.1, 1, 3, 10, 30], ["connect.tls_ms.p95"] = [50, 150, 400, 1000, 3000], ["hold.resets.per_h"] = [0, 1, 4, 12, 30],
             ["connect.success"] = [100, 99, 95, 80, 50], ["tcp.bulk.peak.max"] = [800, 400, 100, 10, 1], ["hy2.sustainable_mbps"] = [100, 50, 25, 10, 0],
diff --git a/backend/tests/MoShiro.Backend.Analysis.Tests/OpTests.cs b/backend/tests/MoShiro.Backend.Analysis.Tests/OpTests.cs
index 850e2d1..82d0002 100644
--- a/backend/tests/MoShiro.Backend.Analysis.Tests/OpTests.cs
+++ b/backend/tests/MoShiro.Backend.Analysis.Tests/OpTests.cs
@@ -90,6 +90,28 @@ public sealed class OpTests
         Assert.Equal(2, ((RunLengthAcc)EvaluateOneBucket(chunk, "loss.run").Items["loss.run"]).Max);
     }
 
+    [Fact]
+    public void LossRuns_AreSeparatedByDirection_AndDownstreamExcludesRequestsLostUpstream()
+    {
+        bool[] upLost = [false, true, true, false, false, false, true, true];
+        bool[] downLost = [false, false, true, true, false, true, false, true];
+        RawChunk chunk = ChunkFactory.Echo(s_agent, "udp_echo", T0, upLost.Length, 100,
+            i => new EchoPacket(upLost[i], downLost[i], 20_000, 20_000));
+
+        MetricSet set = EvaluateOneBucket(chunk, "loss.run.up", "loss.run.down");
+        Assert.Equal(2, ((MaxAcc)set.Items["loss.run.up"]).Result);
+        Assert.Equal(1, ((MaxAcc)set.Items["loss.run.down"]).Result);
+    }
+
+    [Fact]
+    public void LossRuns_NoLoss_ExportsZeroForBothDirections()
+    {
+        RawChunk chunk = ChunkFactory.UdpEchoClean(s_agent, T0, count: 8);
+        MetricSet set = EvaluateOneBucket(chunk, "loss.run.up", "loss.run.down");
+        Assert.Equal(0, ((MaxAcc)set.Items["loss.run.up"]).Result);
+        Assert.Equal(0, ((MaxAcc)set.Items["loss.run.down"]).Result);
+    }
+
     [Fact]
     public void Reorder_CountsLateArrivals_AndIgnoresDuplicates()
     {
diff --git a/backend/tests/MoShiro.Backend.Tests/AgentEndToEndTests.cs b/backend/tests/MoShiro.Backend.Tests/AgentEndToEndTests.cs
index f4ad4ff..b55c441 100644
--- a/backend/tests/MoShiro.Backend.Tests/AgentEndToEndTests.cs
+++ b/backend/tests/MoShiro.Backend.Tests/AgentEndToEndTests.cs
@@ -21,7 +21,7 @@ public sealed class AgentEndToEndTests
         AgentHarness agent = await AgentHarness.StartAsync(_backend);
         await agent.OverrideLineTasksAsync(rateHz: 30);
         ProbeSimulator probe = await agent.ConnectProbeAsync();
-        LineTaskSet set = await probe.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "udp_echo" && t.Port == agent.App.UdpPorts[0]));
+        LineTaskSet set = await probe.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "udp_echo" && t.Port == agent.App.QuicPorts[0]));
         return (agent, probe, set.Tasks.Single(t => t.Kind == "udp_echo"));
     }
 
@@ -159,8 +159,8 @@ public sealed class AgentEndToEndTests
 
             // The probe process restarts: a new session with its own streams; sequence numbers start from 0 again
             await using ProbeSimulator second = first.Restarted();
-            await second.ConnectAsync("127.0.0.1", agent.App.ControlPort, agent.TlsPublicKey, agent.App.UdpPorts[0], agent.NodeId);
-            LineTaskSet set = await second.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "udp_echo" && t.Port == agent.App.UdpPorts[0]));
+            await second.ConnectAsync("127.0.0.1", agent.App.ControlPort, agent.TlsPublicKey, agent.App.QuicPorts[0], agent.NodeId);
+            LineTaskSet set = await second.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "udp_echo" && t.Port == agent.App.QuicPorts[0]));
             LineTask udp2 = set.Tasks.Single(t => t.Kind == "udp_echo");
             Assert.NotEqual(udp.StreamId, udp2.StreamId);
 
@@ -221,11 +221,11 @@ public sealed class AgentEndToEndTests
         await using AgentHarness agent = await AgentHarness.StartAsync(_backend);
         await agent.CreateProbeAsync();
         await using var stranger = new ProbeSimulator("prb_stranger", Fleet.Identity.NodeIdentity.Generate());
-        await Assert.ThrowsAnyAsync<Exception>(() => stranger.ConnectAsync("127.0.0.1", agent.App.ControlPort, agent.TlsPublicKey, agent.App.UdpPorts[0], agent.NodeId));
+        await Assert.ThrowsAnyAsync<Exception>(() => stranger.ConnectAsync("127.0.0.1", agent.App.ControlPort, agent.TlsPublicKey, agent.App.QuicPorts[0], agent.NodeId));
 
         // 证书公钥不对（中间人）也不会连上
         await using ProbeSimulator probe = await agent.CreateProbeAsync();
-        await Assert.ThrowsAnyAsync<Exception>(() => probe.ConnectAsync("127.0.0.1", agent.App.ControlPort, Fleet.Identity.NodeIdentity.Generate().PublicKeySpki, agent.App.UdpPorts[0], agent.NodeId));
+        await Assert.ThrowsAnyAsync<Exception>(() => probe.ConnectAsync("127.0.0.1", agent.App.ControlPort, Fleet.Identity.NodeIdentity.Generate().PublicKeySpki, agent.App.QuicPorts[0], agent.NodeId));
     }
 
     [Fact]
@@ -335,7 +335,7 @@ public sealed class AgentEndToEndTests
         await using AgentHarness agent = await AgentHarness.StartAsync(_backend, config => config.Limits.MaxTotalMbps = 20);
         await agent.OverrideLineTasksAsync();
 
-        var phase = new TestPhase { Kind = "udp_train", DurationSeconds = 1, Params = { ["port"] = System.Text.Json.JsonSerializer.SerializeToElement(agent.App.UdpPorts[0]) } };
+        var phase = new TestPhase { Kind = "udp_train", DurationSeconds = 1, Params = { ["port"] = System.Text.Json.JsonSerializer.SerializeToElement(agent.App.QuicPorts[0]) } };
         var run = new TestRunParams { TestId = new TestId("tst_x"), ProbeId = new ProbeId("prb_nobody"), Plan = "x", Phases = [phase] };
         Assert.Equal("probe_offline", agent.App.Tests.Start(run).Error.Code.Value);
 
diff --git a/backend/tests/MoShiro.Backend.Tests/AgentHarness.cs b/backend/tests/MoShiro.Backend.Tests/AgentHarness.cs
index 2a4854b..0fd5fbf 100644
--- a/backend/tests/MoShiro.Backend.Tests/AgentHarness.cs
+++ b/backend/tests/MoShiro.Backend.Tests/AgentHarness.cs
@@ -58,7 +58,7 @@ public sealed class AgentHarness : IAsyncDisposable
         var config = new AgentConfig
         {
             Fleet = { Server = backend.BaseAddress.ToString(), IdentityDir = directory },
-            Listen = { Bind = "127.0.0.1", ControlPort = 0, UdpPorts = [0], TcpPorts = [0] },
+            Listen = { Bind = "127.0.0.1", ControlPort = 0, QuicPorts = [0], TcpPorts = [0] },
         };
         configure?.Invoke(config);
         LoadedNodeIdentity identity = LoadedNodeIdentity.Load(directory);
@@ -87,7 +87,7 @@ public sealed class AgentHarness : IAsyncDisposable
     public async Task<ProbeSimulator> ConnectProbeAsync()
     {
         ProbeSimulator probe = await CreateProbeAsync();
-        await probe.ConnectAsync("127.0.0.1", App.ControlPort, TlsPublicKey, App.UdpPorts[0], NodeId);
+        await probe.ConnectAsync("127.0.0.1", App.ControlPort, TlsPublicKey, App.QuicPorts[0], NodeId);
         return probe;
     }
 
@@ -104,7 +104,7 @@ public sealed class AgentHarness : IAsyncDisposable
             }
 
             string kind = task["kind"]!.GetValue<string>();
-            var parameters = new JsonObject { ["port"] = kind == "udp_echo" ? App.UdpPorts[0] : App.TcpPorts[0] };
+            var parameters = new JsonObject { ["port"] = kind == "udp_echo" ? App.QuicPorts[0] : App.TcpPorts[0] };
             // 默认的 connect 模板在这些用例里不需要（也占预算）：对这个 Agent 关掉它
             bool enabled = kind != "connect";
             if (rateHz is { } hz && kind != "connect")
diff --git a/backend/tests/MoShiro.TestSupport/AgentSimulator.cs b/backend/tests/MoShiro.TestSupport/AgentSimulator.cs
index 603fc25..77fac3b 100644
--- a/backend/tests/MoShiro.TestSupport/AgentSimulator.cs
+++ b/backend/tests/MoShiro.TestSupport/AgentSimulator.cs
@@ -97,6 +97,7 @@ public sealed class AgentSimulator : IAsyncDisposable
             ["meta"] = new JsonObject
             {
                 ["probe_tcp_port"] = 7443,
+                ["probe_quic_ports"] = new JsonArray(7443),
                 ["probe_udp_ports"] = new JsonArray(7443),
                 ["public_host"] = publicHost,
                 ["kinds"] = new JsonArray((kinds ?? ["udp_echo", "tcp_echo", "udp_train", "connect", "hold", "tcp_bulk", "icmp_echo"]).Select(k => (JsonNode?)JsonValue.Create(k)).ToArray()),
@@ -154,7 +155,8 @@ public sealed class AgentSimulator : IAsyncDisposable
                 TlsPublicKey = Convert.ToBase64String(_tlsKey.PublicKeySpki),
                 Addresses = Addresses is null ? null : [.. Addresses],
                 ProbeTcpPort = 7443,
-                ProbeUdpPorts = [7443],
+                ProbeQuicPorts = [7443],
+                LegacyProbeUdpPorts = [7443],
                 LocalLimits = new LocalLimits { MaxTotalMbps = 200, MaxTotalPps = 20_000, MaxConcurrentTests = 1 },
             },
             MoShiroJsonContext.Default.AgentHelloMeta);
diff --git a/backend/tests/MoShiro.TestSupport/MoShiro.TestSupport.csproj b/backend/tests/MoShiro.TestSupport/MoShiro.TestSupport.csproj
index 56e8167..75a458f 100644
--- a/backend/tests/MoShiro.TestSupport/MoShiro.TestSupport.csproj
+++ b/backend/tests/MoShiro.TestSupport/MoShiro.TestSupport.csproj
@@ -4,6 +4,7 @@
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\shared\MoShiro.Protocol\MoShiro.Protocol.csproj" />
+    <ProjectReference Include="..\..\shared\MoShiro.Measurement\MoShiro.Measurement.csproj" />
     <ProjectReference Include="..\..\fleet\src\Fleet.Identity\Fleet.Identity.csproj" />
     <ProjectReference Include="..\..\fleet\src\Fleet.Link\Fleet.Link.csproj" />
   </ItemGroup>
diff --git a/backend/tests/MoShiro.TestSupport/ProbeSimulator.cs b/backend/tests/MoShiro.TestSupport/ProbeSimulator.cs
index c02797a..5d02f70 100644
--- a/backend/tests/MoShiro.TestSupport/ProbeSimulator.cs
+++ b/backend/tests/MoShiro.TestSupport/ProbeSimulator.cs
@@ -8,13 +8,14 @@ using Fleet.Core;
 using Fleet.Identity;
 using Fleet.Link;
 using Fleet.Rpc;
+using MoShiro.Measurement;
 using MoShiro.Protocol;
 
 namespace MoShiro.TestSupport;
 
 /// <summary>
 /// 假 Probe：通过真实的点对点握手（TLS 固定证书 + 签名 + ECDH）连接真实的 Agent，接收 <c>line_task_set</c>，
-/// 在自己的 UDP 套接字上发回显包、接收单向数据流、估计时钟偏移，并把 Probe 一侧的列块经发件箱通道 17 交给 Agent。
+/// 通过 QUIC Datagram 发回显包、接收单向数据流、估计时钟偏移，并把 Probe 一侧的列块经发件箱通道 17 交给 Agent。
 /// 它实现 Probe 的协议职责，是将来真实 Probe 的参照。
 /// </summary>
 public sealed class ProbeSimulator : IAsyncDisposable
@@ -30,8 +31,9 @@ public sealed class ProbeSimulator : IAsyncDisposable
     private readonly CancellationTokenSource _stop = new();
     private NodeId _agentId;
     private RpcSession<ProbeSimulator>? _rpc;
-    private UdpClient? _udp;
-    private IPEndPoint? _agentUdp;
+    private QuicDatagramTransport? _quic;
+    private DataSession? _dataSession;
+    private IPEndPoint? _agentQuic;
     private PeerSessionInfo? _info;
     private Task? _receiver;
     private Task? _run;
@@ -72,13 +74,22 @@ public sealed class ProbeSimulator : IAsyncDisposable
         (PeerSessionInfo info, TlsFrameTransport transport) = await PeerConnector.ConnectAsync(host, controlPort, agentPublicKey, _identity, ProbeId, "0.0.0-sim", 8 << 20, time ?? TimeProvider.System, ct);
         _info = info;
         _agentKey = agentPublicKey;
-        _udp = new UdpClient(new IPEndPoint(IPAddress.Loopback, 0));
-        _agentUdp = new IPEndPoint(IPAddress.Parse(host), udpPort);
+        _dataSession = new DataSession(info.Credentials.SessionIdValue, info.Credentials.Key);
+        _agentQuic = new IPEndPoint(IPAddress.Parse(host), udpPort);
+        _quic = new QuicDatagramTransport(
+            _dataSession,
+            new MonoClock(time ?? TimeProvider.System),
+            new DataPlaneCounters(),
+            new TestNodeLog(),
+            _agentQuic,
+            agentPublicKey,
+            0);
         _rpc = new RpcSession<ProbeSimulator>(transport, _router, this, time ?? TimeProvider.System);
         _rpc.OnBinary = (_, _) => ValueTask.CompletedTask;
         _run = _rpc.RunAsync(_stop.Token);
-        _receiver = Task.Run(ReceiveLoopAsync, _stop.Token);
+        _receiver = _quic.RunAsync(_stop.Token);
         await SyncClockAsync();
+        await _quic.ConnectAsync(ct);
     }
 
     public async Task<LineTaskSet> WaitForTasksAsync(Func<LineTaskSet, bool> predicate, TimeSpan? timeout = null)
@@ -123,19 +134,21 @@ public sealed class ProbeSimulator : IAsyncDisposable
         int size = (int)task.Params["size"].GetInt64();
         var collector = new EchoCollector();
         _echoes[task.StreamId] = collector;
+        _quic!.Register(task.StreamId, OnDatagram);
         long startUtc = TimeProvider.System.GetUtcNow().ToUnixTimeMilliseconds();
         byte[] packet = new byte[size];
         for (uint seq = 0; seq < count; seq++)
         {
             long t1 = NowUs();
             collector.Sent[seq] = t1;
-            UdpPacket.Write(packet, new UdpHeader(UdpPacketType.EchoRequest, _info!.Credentials.SessionIdValue, task.StreamId, seq, t1), _info.Credentials.Key);
-            await _udp!.SendAsync(packet, packet.Length, _agentUdp!);
+            MeasurementDatagram.Write(packet, new MeasurementDatagramHeader(MeasurementDatagramType.EchoRequest, _info!.Credentials.SessionIdValue, task.StreamId, seq, t1), _info.Credentials.Key);
+            _quic.Send(_dataSession!, _agentQuic!, packet);
             await Task.Delay(interval, ct);
         }
 
         await Task.Delay(300, ct); // 等最后的回复
         _echoes.TryRemove(task.StreamId, out _);
+        _quic.Unregister(task.StreamId);
 
         var msg = new StreamBuilder(new StreamSpec("msg", [Col.Seq("seq"), Col.U16("size"), Col.TsProbe("t1"), Col.TsProbe("t4", nullable: true)]));
         foreach ((uint seq, long t1) in collector.Sent.OrderBy(p => p.Key))
@@ -191,22 +204,28 @@ public sealed class ProbeSimulator : IAsyncDisposable
     }
 
     /// <summary>发送任意字节到 Agent 的 UDP 端口（用来测试 Agent 对垃圾包的处理）。</summary>
-    public Task SendRawUdpAsync(byte[] datagram) => _udp!.SendAsync(datagram, datagram.Length, _agentUdp!);
+    public Task SendRawUdpAsync(byte[] datagram)
+    {
+        _quic!.Send(_dataSession!, _agentQuic!, datagram);
+        return Task.CompletedTask;
+    }
 
     /// <summary>用伪造的密钥发一个回显包。</summary>
     public Task SendForgedEchoAsync(LineTask task, uint seq, byte[]? key = null)
     {
         byte[] packet = new byte[64];
-        UdpPacket.Write(packet, new UdpHeader(UdpPacketType.EchoRequest, _info!.Credentials.SessionIdValue, task.StreamId, seq, NowUs()), key ?? new byte[32]);
-        return _udp!.SendAsync(packet, packet.Length, _agentUdp!);
+        MeasurementDatagram.Write(packet, new MeasurementDatagramHeader(MeasurementDatagramType.EchoRequest, _info!.Credentials.SessionIdValue, task.StreamId, seq, NowUs()), key ?? new byte[32]);
+        _quic!.Send(_dataSession!, _agentQuic!, packet);
+        return Task.CompletedTask;
     }
 
     /// <summary>重放：用同一个序号、同样的密钥再发一次。</summary>
     public Task SendEchoAsync(LineTask task, uint seq)
     {
         byte[] packet = new byte[64];
-        UdpPacket.Write(packet, new UdpHeader(UdpPacketType.EchoRequest, _info!.Credentials.SessionIdValue, task.StreamId, seq, NowUs()), _info.Credentials.Key);
-        return _udp!.SendAsync(packet, packet.Length, _agentUdp!);
+        MeasurementDatagram.Write(packet, new MeasurementDatagramHeader(MeasurementDatagramType.EchoRequest, _info!.Credentials.SessionIdValue, task.StreamId, seq, NowUs()), _info.Credentials.Key);
+        _quic!.Send(_dataSession!, _agentQuic!, packet);
+        return Task.CompletedTask;
     }
 
     public int EchoRepliesSeen(uint streamId) => _echoes.TryGetValue(streamId, out EchoCollector? c) ? c.Received.Count : 0;
@@ -227,7 +246,7 @@ public sealed class ProbeSimulator : IAsyncDisposable
     public async ValueTask DisposeAsync()
     {
         await _stop.CancelAsync();
-        _udp?.Dispose();
+        _quic?.Dispose();
         if (_rpc is not null)
         {
             await _rpc.DisposeAsync();
@@ -277,41 +296,18 @@ public sealed class ProbeSimulator : IAsyncDisposable
         return header;
     }
 
-    private async Task ReceiveLoopAsync()
+    private void OnDatagram(in QuicDatagramDelivery delivery)
     {
-        while (!_stop.IsCancellationRequested)
+        long now = delivery.ReceiveUs;
+        MeasurementDatagramHeader header = delivery.Header;
+        if (header.Type == MeasurementDatagramType.EchoReply && _echoes.TryGetValue(header.StreamId, out EchoCollector? echo))
         {
-            UdpReceiveResult result;
-            try
-            {
-                result = await _udp!.ReceiveAsync(_stop.Token);
-            }
-            catch (Exception ex) when (ex is OperationCanceledException or ObjectDisposedException or SocketException)
-            {
-                if (_stop.IsCancellationRequested || ex is ObjectDisposedException)
-                {
-                    return;
-                }
-
-                continue;
-            }
-
-            long now = NowUs();
-            byte[] data = result.Buffer;
-            if (!UdpPacket.TryParseHeader(data, out UdpHeader header) || !UdpPacket.VerifyMac(data, _info!.Credentials.Key))
-            {
-                continue;
-            }
-
-            if (header.Type == UdpPacketType.EchoReply && _echoes.TryGetValue(header.StreamId, out EchoCollector? echo))
-            {
-                echo.Received.TryAdd(header.Seq, now);
-            }
-            else if (header.Type == UdpPacketType.Data && _trains.TryGetValue(header.StreamId, out TrainCollector? train))
-            {
-                train.Received.TryAdd(header.Seq, now);
-                train.Size = data.Length;
-            }
+            echo.Received.TryAdd(header.Seq, now);
+        }
+        else if (header.Type == MeasurementDatagramType.Data && _trains.TryGetValue(header.StreamId, out TrainCollector? train))
+        {
+            train.Received.TryAdd(header.Seq, now);
+            train.Size = delivery.Payload.Length;
         }
     }
 
@@ -366,33 +362,39 @@ public sealed class ProbeSimulator : IAsyncDisposable
 
     private readonly ConcurrentDictionary<uint, TestPhaseStartParams> _activePhases = new();
 
-    private async Task<bool> StartPhaseAsync(TestPhaseStartParams start, CancellationToken ct)
+    private Task<bool> StartPhaseAsync(TestPhaseStartParams start, CancellationToken ct)
     {
         Phases.Enqueue(start);
         if (RefusePhases)
         {
-            return false;
+            return Task.FromResult(false);
         }
 
         _activePhases[start.StreamId] = start;
         if (start.Kind == "udp_train")
         {
             _trains[start.StreamId] = new TrainCollector { StartUtcMs = TimeProvider.System.GetUtcNow().ToUnixTimeMilliseconds() };
+            _quic!.Register(start.StreamId, OnDatagram);
             // 先发几个探活包，让 Agent 学到（最新的）源地址，再回复 accepted
             byte[] hello = new byte[64];
             for (uint seq = 0; seq < 3; seq++)
             {
-                UdpPacket.Write(hello, new UdpHeader(UdpPacketType.Data, _info!.Credentials.SessionIdValue, start.StreamId, seq, NowUs()), _info.Credentials.Key);
-                await _udp!.SendAsync(hello.AsMemory(), _agentUdp!, ct);
+                MeasurementDatagram.Write(hello, new MeasurementDatagramHeader(MeasurementDatagramType.Data, _info!.Credentials.SessionIdValue, start.StreamId, seq, NowUs()), _info.Credentials.Key);
+                _quic.Send(_dataSession!, _agentQuic!, hello);
             }
         }
 
-        return true;
+        _ = ct;
+        return Task.FromResult(true);
     }
 
     private async Task<int> EndPhaseAsync(TestPhaseEndParams end, CancellationToken ct)
     {
         _activePhases.TryRemove(end.StreamId, out TestPhaseStartParams? start);
+        if (start is not null)
+        {
+            _quic!.Unregister(start.StreamId);
+        }
         if (start is null || DropFragments)
         {
             _trains.TryRemove(end.StreamId, out _);
@@ -456,4 +458,9 @@ public sealed class ProbeSimulator : IAsyncDisposable
 
         public long StartUtcMs { get; init; }
     }
+
+    private sealed class TestNodeLog : INodeLog
+    {
+        public void Write(NodeLogLevel level, string message, params (string Key, object? Value)[] fields) { }
+    }
 }
diff --git a/web/shared/api/schema.ts b/web/shared/api/schema.ts
index aa1d0cd..6a23445 100644
--- a/web/shared/api/schema.ts
+++ b/web/shared/api/schema.ts
@@ -1300,6 +1300,7 @@ export interface components {
             /** Format: int32 */
             probe_tcp_port: number | string;
             probe_udp_ports: (number | string)[];
+            probe_quic_ports: (number | string)[];
             labels: string[];
             public_visible: boolean;
             kinds: string[];
@@ -1694,6 +1695,7 @@ export interface components {
             ip_version: string;
             /** @default false */
             ipv6_available: boolean;
+            quic_health?: null | components["schemas"]["QuicLineHealthDto"];
         };
         LinkDto: {
             probe_id: string;
@@ -1828,6 +1830,7 @@ export interface components {
             last_test: null | components["schemas"]["TestSummaryDto"];
             /** @default ipv4 */
             ip_version: string;
+            quic_health?: null | components["schemas"]["QuicLineHealthDto"];
         };
         PageDtoOfAgentDto: {
             items: components["schemas"]["AgentDto"][];
@@ -2037,6 +2040,39 @@ export interface components {
             sha256: string;
             command: string;
         };
+        QuicLineHealthDto: {
+            connected: boolean;
+            /** Format: int64 */
+            handshake_attempts: number | string;
+            /** Format: int64 */
+            handshake_successes: number | string;
+            /** Format: int64 */
+            handshake_failures: number | string;
+            /** Format: int64 */
+            handshake_timeouts: number | string;
+            /** Format: double */
+            handshake_success_rate: null | number | string;
+            /** Format: double */
+            handshake_failure_rate: null | number | string;
+            /** Format: double */
+            handshake_timeout_rate: null | number | string;
+            /** Format: double */
+            handshake_p95_ms: null | number | string;
+            /** Format: int64 */
+            handshake_sample_count: number | string;
+            /** Format: double */
+            transport_packet_loss_rate: null | number | string;
+            /** Format: uint64 */
+            transport_packets_sent: null | number | string;
+            /** Format: uint32 */
+            transport_congestion_events: null | number | string;
+            /** Format: uint32 */
+            transport_ecn_congestion_events: null | number | string;
+            /** Format: uint16 */
+            path_mtu: null | number | string;
+            /** Format: date-time */
+            at: unknown;
+        };
         RawChunkMetaDto: {
             chunk_id: string;
             agent_id: string;