diff --git a/src/GameCult.Mesh/CultMeshReliabilityDiagnostics.cs b/src/GameCult.Mesh/CultMeshReliabilityDiagnostics.cs
new file mode 100644
index 00000000..5391c77e
--- /dev/null
+++ b/src/GameCult.Mesh/CultMeshReliabilityDiagnostics.cs
@@ -0,0 +1,183 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace GameCult.Mesh
+{
+    /// <summary>
+    /// Clock used by CultMesh reliability owners.
+    /// </summary>
+    public interface ICultMeshClock
+    {
+        DateTimeOffset UtcNow { get; }
+
+        Task DelayAsync(TimeSpan delay, CancellationToken cancellationToken = default);
+    }
+
+    /// <summary>
+    /// Wall clock used outside deterministic tests.
+    /// </summary>
+    public sealed class CultMeshSystemClock : ICultMeshClock
+    {
+        public static CultMeshSystemClock Instance { get; } = new CultMeshSystemClock();
+
+        private CultMeshSystemClock()
+        {
+        }
+
+        public DateTimeOffset UtcNow => DateTimeOffset.UtcNow;
+
+        public Task DelayAsync(TimeSpan delay, CancellationToken cancellationToken = default)
+        {
+            return Task.Delay(delay, cancellationToken);
+        }
+    }
+
+    public enum CultMeshReliabilityOrgan
+    {
+        Discovery,
+        Session,
+        Authority,
+        ContentTransfer,
+        Stream
+    }
+
+    public enum CultMeshDiagnosticKind
+    {
+        DiscoveryObservation,
+        CandidateRejected,
+        ConnectionAttempt,
+        PathChanged,
+        RetryDecision,
+        AuthorityDecision,
+        VerifiedRange,
+        StreamGap
+    }
+
+    /// <summary>
+    /// One bounded operational observation emitted by a CultMesh reliability owner.
+    /// </summary>
+    public sealed class CultMeshDiagnosticEvent
+    {
+        public CultMeshDiagnosticEvent(
+            long sequence,
+            DateTimeOffset observedAtUtc,
+            CultMeshReliabilityOrgan organ,
+            CultMeshDiagnosticKind kind,
+            string operationId,
+            string subjectId,
+            string state,
+            string reasonCode = "",
+            string sourceId = "",
+            string endpoint = "",
+            string schemaVersion = "",
+            string libraryVersion = "")
+        {
+            if (sequence < 0) throw new ArgumentOutOfRangeException(nameof(sequence));
+            Sequence = sequence;
+            ObservedAtUtc = observedAtUtc;
+            Organ = organ;
+            Kind = kind;
+            OperationId = operationId ?? "";
+            SubjectId = subjectId ?? "";
+            State = state ?? "";
+            ReasonCode = reasonCode ?? "";
+            SourceId = sourceId ?? "";
+            Endpoint = endpoint ?? "";
+            SchemaVersion = schemaVersion ?? "";
+            LibraryVersion = string.IsNullOrWhiteSpace(libraryVersion)
+                ? CultMeshLibraryVersion.Current
+                : libraryVersion;
+        }
+
+        public long Sequence { get; }
+        public DateTimeOffset ObservedAtUtc { get; }
+        public CultMeshReliabilityOrgan Organ { get; }
+        public CultMeshDiagnosticKind Kind { get; }
+        public string OperationId { get; }
+        public string SubjectId { get; }
+        public string State { get; }
+        public string ReasonCode { get; }
+        public string SourceId { get; }
+        public string Endpoint { get; }
+        public string SchemaVersion { get; }
+        public string LibraryVersion { get; }
+    }
+
+    public interface ICultMeshDiagnosticSink
+    {
+        void Emit(CultMeshDiagnosticEvent diagnostic);
+    }
+
+    public sealed class CultMeshNullDiagnosticSink : ICultMeshDiagnosticSink
+    {
+        public static CultMeshNullDiagnosticSink Instance { get; } = new CultMeshNullDiagnosticSink();
+
+        private CultMeshNullDiagnosticSink()
+        {
+        }
+
+        public void Emit(CultMeshDiagnosticEvent diagnostic)
+        {
+        }
+    }
+
+    /// <summary>
+    /// Bounded diagnostic projection suitable for inspection and tests.
+    /// </summary>
+    public sealed class CultMeshDiagnosticBuffer : ICultMeshDiagnosticSink
+    {
+        private readonly object _gate = new object();
+        private readonly Queue<CultMeshDiagnosticEvent> _events;
+
+        public CultMeshDiagnosticBuffer(int capacity = 256)
+        {
+            if (capacity <= 0) throw new ArgumentOutOfRangeException(nameof(capacity));
+            Capacity = capacity;
+            _events = new Queue<CultMeshDiagnosticEvent>(capacity);
+        }
+
+        public int Capacity { get; }
+
+        public IReadOnlyList<CultMeshDiagnosticEvent> Snapshot()
+        {
+            lock (_gate)
+            {
+                return _events.ToArray();
+            }
+        }
+
+        public void Emit(CultMeshDiagnosticEvent diagnostic)
+        {
+            if (diagnostic == null) throw new ArgumentNullException(nameof(diagnostic));
+            lock (_gate)
+            {
+                while (_events.Count >= Capacity)
+                {
+                    _events.Dequeue();
+                }
+                _events.Enqueue(diagnostic);
+            }
+        }
+    }
+
+    public static class CultMeshLibraryVersion
+    {
+        public static string Current { get; } = Resolve();
+
+        private static string Resolve()
+        {
+            var assembly = typeof(CultMeshLibraryVersion).Assembly;
+            var informational = assembly
+                .GetCustomAttributes(typeof(AssemblyInformationalVersionAttribute), false)
+                .OfType<AssemblyInformationalVersionAttribute>()
+                .FirstOrDefault()?.InformationalVersion;
+            return string.IsNullOrWhiteSpace(informational)
+                ? assembly.GetName().Version?.ToString() ?? "unknown"
+                : informational;
+        }
+    }
+}
diff --git a/src/GameCult.Mesh/CultMeshVerseDiscovery.cs b/src/GameCult.Mesh/CultMeshVerseDiscovery.cs
index c6b9b4b6..0955a99b 100644
--- a/src/GameCult.Mesh/CultMeshVerseDiscovery.cs
+++ b/src/GameCult.Mesh/CultMeshVerseDiscovery.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using GameCult.Networking;
 
@@ -161,6 +162,15 @@ namespace GameCult.Mesh
         /// Defaults to endpoint selection: rudp:// uses RUDP and cultnet:// uses LiteNetLib.
         /// </summary>
         public Func<ICultNetSchemaClient>? CreateClient { get; set; }
+
+        /// <summary>Gets or sets the clock that owns discovery deadlines.</summary>
+        public ICultMeshClock Clock { get; set; } = CultMeshSystemClock.Instance;
+
+        /// <summary>Gets or sets the bounded operational diagnostic sink.</summary>
+        public ICultMeshDiagnosticSink Diagnostics { get; set; } = CultMeshNullDiagnosticSink.Instance;
+
+        /// <summary>Gets or sets the identity of this bootstrap lookup source.</summary>
+        public string SourceId { get; set; } = "configured-bootstrap";
     }
 
     /// <summary>
@@ -169,6 +179,7 @@ namespace GameCult.Mesh
     public sealed class CultMeshVerseDiscoveryClient
     {
         private readonly CultMeshVerseDiscoveryClientOptions _options;
+        private long _diagnosticSequence;
 
         /// <summary>
         /// Creates a Verse discovery client.
@@ -202,17 +213,38 @@ namespace GameCult.Mesh
             client.OnCultNet<CultNetErrorMessage>(error =>
                 completion.TrySetException(new InvalidOperationException(error.Error)));
 
-            client.Connect(host, port);
-            var backgroundFailure = (client as ICultNetSchemaClientHealth)?.BackgroundFailure;
-            await WaitForConnectionAsync(client, endpoint, backgroundFailure).ConfigureAwait(false);
-            client.SendCultNet(new CultMeshVerseCatalogRequestMessage
+            Emit(CultMeshDiagnosticKind.ConnectionAttempt, messageId, endpoint, "connecting");
+            try
             {
-                MessageId = messageId,
-                TransportVersion = request?.TransportVersion,
-                VerseIds = request?.VerseIds
-            });
+                client.Connect(host, port);
+                var backgroundFailure = (client as ICultNetSchemaClientHealth)?.BackgroundFailure;
+                await WaitForConnectionAsync(client, endpoint, backgroundFailure).ConfigureAwait(false);
+                client.SendCultNet(new CultMeshVerseCatalogRequestMessage
+                {
+                    MessageId = messageId,
+                    TransportVersion = request?.TransportVersion,
+                    VerseIds = request?.VerseIds
+                });
 
-            return await WaitForResponseAsync(completion.Task, endpoint, backgroundFailure).ConfigureAwait(false);
+                var response = await WaitForResponseAsync(completion.Task, endpoint, backgroundFailure).ConfigureAwait(false);
+                Emit(
+                    CultMeshDiagnosticKind.DiscoveryObservation,
+                    messageId,
+                    endpoint,
+                    "fresh",
+                    schemaVersion: response.SchemaVersion);
+                return response;
+            }
+            catch (Exception error) when (!(error is OperationCanceledException))
+            {
+                Emit(
+                    CultMeshDiagnosticKind.CandidateRejected,
+                    messageId,
+                    endpoint,
+                    "unavailable",
+                    ReasonCode(error));
+                throw;
+            }
         }
 
         /// <summary>
@@ -251,7 +283,7 @@ namespace GameCult.Mesh
             string endpoint,
             Task<Exception>? backgroundFailure)
         {
-            var deadline = DateTimeOffset.UtcNow + _options.ConnectTimeout;
+            var deadline = _options.Clock.UtcNow + _options.ConnectTimeout;
             while (!client.Connected)
             {
                 if (backgroundFailure?.IsCompleted == true)
@@ -261,12 +293,12 @@ namespace GameCult.Mesh
                         $"Verse discovery client failed while connecting to {endpoint}.",
                         error);
                 }
-                if (DateTimeOffset.UtcNow >= deadline)
+                if (_options.Clock.UtcNow >= deadline)
                 {
                     throw new TimeoutException($"Timed out connecting to Verse discovery endpoint {endpoint}.");
                 }
 
-                await Task.Delay(TimeSpan.FromMilliseconds(25)).ConfigureAwait(false);
+                await _options.Clock.DelayAsync(TimeSpan.FromMilliseconds(25)).ConfigureAwait(false);
             }
         }
 
@@ -275,7 +307,7 @@ namespace GameCult.Mesh
             string endpoint,
             Task<Exception>? backgroundFailure)
         {
-            var timeoutTask = Task.Delay(_options.ResponseTimeout);
+            var timeoutTask = _options.Clock.DelayAsync(_options.ResponseTimeout);
             var completed = backgroundFailure == null
                 ? await Task.WhenAny(responseTask, timeoutTask).ConfigureAwait(false)
                 : await Task.WhenAny(responseTask, timeoutTask, backgroundFailure).ConfigureAwait(false);
@@ -293,5 +325,34 @@ namespace GameCult.Mesh
 
             return await responseTask.ConfigureAwait(false);
         }
+
+        private void Emit(
+            CultMeshDiagnosticKind kind,
+            string operationId,
+            string endpoint,
+            string state,
+            string reasonCode = "",
+            string schemaVersion = "")
+        {
+            _options.Diagnostics.Emit(new CultMeshDiagnosticEvent(
+                Interlocked.Increment(ref _diagnosticSequence),
+                _options.Clock.UtcNow,
+                CultMeshReliabilityOrgan.Discovery,
+                kind,
+                operationId,
+                endpoint,
+                state,
+                reasonCode,
+                _options.SourceId,
+                endpoint,
+                schemaVersion));
+        }
+
+        private static string ReasonCode(Exception error)
+        {
+            if (error is TimeoutException) return "timeout";
+            if (error is InvalidOperationException) return "transport_failure";
+            return "lookup_failure";
+        }
     }
 }
diff --git a/src/GameCult.Mesh/docs/reliability-migration-plan.md b/src/GameCult.Mesh/docs/reliability-migration-plan.md
index 3e4e14ec..1ec8067d 100644
--- a/src/GameCult.Mesh/docs/reliability-migration-plan.md
+++ b/src/GameCult.Mesh/docs/reliability-migration-plan.md
@@ -202,6 +202,36 @@ failure.
   counters.
 - Diagnostics have bounded cost and can be disabled or sampled on hot paths.
 
+### Phase 0 Body Map
+
+**Owner:** reliability organs own their clocks and emit typed observations;
+`CultMeshDiagnosticBuffer` owns only a bounded inspection projection.
+
+**Inputs:** injected `ICultMeshClock`, organ state transitions, endpoint and
+source identity, reason code, and served schema/library version.
+
+**Outputs:** ordered `CultMeshDiagnosticEvent` observations. The deterministic
+test network emits scheduled packet deliveries under loss, duplication,
+reordering, latency, partition, endpoint rotation, corruption, and restart.
+
+**Derived state:** diagnostic sequence and the bounded recent-event window.
+Neither confers reachability, authority, or retry policy.
+
+**Forbidden writers:** diagnostic sinks and fault harnesses cannot choose a
+route, mutate discovery candidates, authorize a peer, or repair a session.
+
+**Shared paths:** the existing Verse discovery client now uses the injected
+clock for connection and response deadlines and emits the same typed timeline
+for success, timeout, and transport failure.
+
+**Cut line:** wall-clock reads and unobservable timeout delays have been removed
+from Verse discovery. Caller-owned catalog mutation and endpoint sequencing
+remain compatibility authority until Phase 1 replaces and demotes them.
+
+**Verification layer:** tests observe the emitted discovery timeline and served
+version, while the deterministic network harness proves exact replay of every
+required hostile-network action.
+
 ## Phase Closure Contract
 
 Every implementation phase must close with all of the following:
diff --git a/tests/GameCult.Mesh.Tests/CultMeshDeterministicNetwork.cs b/tests/GameCult.Mesh.Tests/CultMeshDeterministicNetwork.cs
new file mode 100644
index 00000000..5573204a
--- /dev/null
+++ b/tests/GameCult.Mesh.Tests/CultMeshDeterministicNetwork.cs
@@ -0,0 +1,131 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+#nullable enable
+
+namespace GameCult.Mesh.Tests;
+
+internal enum CultMeshFaultKind
+{
+    Drop,
+    Duplicate,
+    Delay,
+    Reorder,
+    Partition,
+    Corrupt,
+    RotateEndpoint,
+    Restart
+}
+
+internal sealed record CultMeshFault(
+    long SendOrdinal,
+    CultMeshFaultKind Kind,
+    TimeSpan Delay = default,
+    string Endpoint = "");
+
+internal sealed record CultMeshTestPacket(
+    long SendOrdinal,
+    string Endpoint,
+    byte[] Payload,
+    DateTimeOffset DeliverAtUtc,
+    long DeliveryOrdinal);
+
+/// <summary>
+/// Transport-neutral hostile-network harness. Delivery is driven only by the
+/// injected clock and schedule, so a failure timeline is exactly replayable.
+/// </summary>
+internal sealed class CultMeshDeterministicNetwork
+{
+    private readonly Func<DateTimeOffset> _utcNow;
+    private readonly Dictionary<long, CultMeshFault[]> _faults;
+    private readonly List<CultMeshTestPacket> _pending = new();
+    private long _sendOrdinal;
+    private long _deliveryOrdinal;
+    private bool _partitioned;
+    private string _endpoint;
+
+    public CultMeshDeterministicNetwork(
+        Func<DateTimeOffset> utcNow,
+        string endpoint,
+        IEnumerable<CultMeshFault>? faults = null)
+    {
+        _utcNow = utcNow ?? throw new ArgumentNullException(nameof(utcNow));
+        _endpoint = endpoint ?? throw new ArgumentNullException(nameof(endpoint));
+        _faults = (faults ?? Array.Empty<CultMeshFault>())
+            .GroupBy(fault => fault.SendOrdinal)
+            .ToDictionary(group => group.Key, group => group.ToArray());
+    }
+
+    public int RestartCount { get; private set; }
+
+    public string Endpoint => _endpoint;
+
+    public void Send(byte[] payload)
+    {
+        if (payload == null) throw new ArgumentNullException(nameof(payload));
+        var ordinal = ++_sendOrdinal;
+        var copies = 1;
+        var delay = TimeSpan.Zero;
+        var reorder = false;
+        var dropped = false;
+        var bytes = payload.ToArray();
+
+        foreach (var fault in _faults.GetValueOrDefault(ordinal, Array.Empty<CultMeshFault>()))
+        {
+            switch (fault.Kind)
+            {
+                case CultMeshFaultKind.Drop:
+                    dropped = true;
+                    break;
+                case CultMeshFaultKind.Duplicate:
+                    copies++;
+                    break;
+                case CultMeshFaultKind.Delay:
+                    delay += fault.Delay;
+                    break;
+                case CultMeshFaultKind.Reorder:
+                    reorder = true;
+                    break;
+                case CultMeshFaultKind.Partition:
+                    _partitioned = !_partitioned;
+                    break;
+                case CultMeshFaultKind.Corrupt:
+                    if (bytes.Length > 0) bytes[0] ^= 0xff;
+                    break;
+                case CultMeshFaultKind.RotateEndpoint:
+                    _endpoint = fault.Endpoint;
+                    break;
+                case CultMeshFaultKind.Restart:
+                    _pending.Clear();
+                    _partitioned = false;
+                    RestartCount++;
+                    break;
+            }
+        }
+
+        if (dropped || _partitioned) return;
+        for (var copy = 0; copy < copies; copy++)
+        {
+            var deliveryOrdinal = ++_deliveryOrdinal;
+            _pending.Add(new CultMeshTestPacket(
+                ordinal,
+                _endpoint,
+                bytes.ToArray(),
+                _utcNow() + delay,
+                reorder ? -deliveryOrdinal : deliveryOrdinal));
+        }
+    }
+
+    public IReadOnlyList<CultMeshTestPacket> ReceiveAvailable()
+    {
+        var now = _utcNow();
+        var available = _pending
+            .Where(packet => packet.DeliverAtUtc <= now)
+            .OrderBy(packet => packet.DeliverAtUtc)
+            .ThenBy(packet => packet.DeliveryOrdinal)
+            .ToArray();
+        foreach (var packet in available) _pending.Remove(packet);
+        return available;
+    }
+}
diff --git a/tests/GameCult.Mesh.Tests/CultMeshReliabilityDiagnosticsTests.cs b/tests/GameCult.Mesh.Tests/CultMeshReliabilityDiagnosticsTests.cs
new file mode 100644
index 00000000..d40ee4e0
--- /dev/null
+++ b/tests/GameCult.Mesh.Tests/CultMeshReliabilityDiagnosticsTests.cs
@@ -0,0 +1,118 @@
+using System;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace GameCult.Mesh.Tests;
+
+public sealed class CultMeshReliabilityDiagnosticsTests
+{
+    [Test]
+    public void DiagnosticBuffer_IsBoundedAndCarriesServedVersion()
+    {
+        var clock = new TestClock(new DateTimeOffset(2026, 7, 12, 18, 0, 0, TimeSpan.Zero));
+        var diagnostics = new CultMeshDiagnosticBuffer(capacity: 2);
+
+        for (var sequence = 1; sequence <= 3; sequence++)
+        {
+            diagnostics.Emit(new CultMeshDiagnosticEvent(
+                sequence,
+                clock.UtcNow,
+                CultMeshReliabilityOrgan.Discovery,
+                CultMeshDiagnosticKind.DiscoveryObservation,
+                "lookup:aetheria",
+                "aetheria",
+                sequence == 3 ? "degraded" : "fresh",
+                schemaVersion: "gamecult.mesh.discovery_diagnostic.v1"));
+            clock.Advance(TimeSpan.FromSeconds(1));
+        }
+
+        var snapshot = diagnostics.Snapshot();
+        snapshot.Select(item => item.Sequence).Should().Equal(2, 3);
+        snapshot[^1].State.Should().Be("degraded");
+        snapshot[^1].LibraryVersion.Should().Be(CultMeshLibraryVersion.Current);
+        snapshot[^1].LibraryVersion.Should().NotBeNullOrWhiteSpace();
+        snapshot[^1].SchemaVersion.Should().Be("gamecult.mesh.discovery_diagnostic.v1");
+    }
+
+    [Test]
+    public void DeterministicNetwork_ReplaysLossDuplicationReorderingLatencyAndCorruption()
+    {
+        var clock = new TestClock(new DateTimeOffset(2026, 7, 12, 18, 0, 0, TimeSpan.Zero));
+        var network = new CultMeshDeterministicNetwork(
+            () => clock.UtcNow,
+            "rudp://first:3076",
+            new[]
+            {
+                new CultMeshFault(1, CultMeshFaultKind.Drop),
+                new CultMeshFault(2, CultMeshFaultKind.Duplicate),
+                new CultMeshFault(2, CultMeshFaultKind.Delay, TimeSpan.FromSeconds(2)),
+                new CultMeshFault(3, CultMeshFaultKind.Reorder),
+                new CultMeshFault(3, CultMeshFaultKind.Corrupt)
+            });
+
+        network.Send(Encoding.UTF8.GetBytes("lost"));
+        network.Send(Encoding.UTF8.GetBytes("twice"));
+        network.Send(new byte[] { 0x01, 0x02 });
+
+        var immediate = network.ReceiveAvailable();
+        immediate.Should().ContainSingle();
+        immediate[0].SendOrdinal.Should().Be(3);
+        immediate[0].Payload.Should().Equal(0xfe, 0x02);
+
+        clock.Advance(TimeSpan.FromSeconds(2));
+        var delayed = network.ReceiveAvailable();
+        delayed.Should().HaveCount(2);
+        delayed.Select(packet => Encoding.UTF8.GetString(packet.Payload)).Should().OnlyContain(value => value == "twice");
+    }
+
+    [Test]
+    public void DeterministicNetwork_ReplaysPartitionEndpointRotationAndRestart()
+    {
+        var clock = new TestClock(new DateTimeOffset(2026, 7, 12, 18, 0, 0, TimeSpan.Zero));
+        var network = new CultMeshDeterministicNetwork(
+            () => clock.UtcNow,
+            "rudp://first:3076",
+            new[]
+            {
+                new CultMeshFault(1, CultMeshFaultKind.Partition),
+                new CultMeshFault(2, CultMeshFaultKind.Partition),
+                new CultMeshFault(2, CultMeshFaultKind.RotateEndpoint, Endpoint: "rudp://second:3076"),
+                new CultMeshFault(3, CultMeshFaultKind.Restart)
+            });
+
+        network.Send(new byte[] { 1 });
+        network.Send(new byte[] { 2 });
+        network.ReceiveAvailable().Should().ContainSingle().Which.Endpoint.Should().Be("rudp://second:3076");
+
+        network.Send(new byte[] { 3 });
+        network.RestartCount.Should().Be(1);
+        network.Endpoint.Should().Be("rudp://second:3076");
+        network.ReceiveAvailable().Should().ContainSingle().Which.Payload.Should().Equal(3);
+    }
+
+    private sealed class TestClock : ICultMeshClock
+    {
+        public TestClock(DateTimeOffset utcNow)
+        {
+            UtcNow = utcNow;
+        }
+
+        public DateTimeOffset UtcNow { get; private set; }
+
+        public Task DelayAsync(TimeSpan delay, CancellationToken cancellationToken = default)
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+            Advance(delay);
+            return Task.CompletedTask;
+        }
+
+        public void Advance(TimeSpan duration)
+        {
+            UtcNow += duration;
+        }
+    }
+}
diff --git a/tests/GameCult.Networking.Tests/NetworkingTests.cs b/tests/GameCult.Networking.Tests/NetworkingTests.cs
index 42707754..a08dc846 100644
--- a/tests/GameCult.Networking.Tests/NetworkingTests.cs
+++ b/tests/GameCult.Networking.Tests/NetworkingTests.cs
@@ -2789,6 +2789,38 @@ namespace GameCult.Networking.Tests
             Assert.That(response.Verses.Single().VerseId, Is.EqualTo("local"));
         }
 
+        [Test]
+        public async Task CultMeshVerseDiscoveryClient_ReportsDeterministicConnectionFailureTimeline()
+        {
+            var clock = new ManualCultMeshClock(new DateTimeOffset(2026, 7, 12, 18, 0, 0, TimeSpan.Zero));
+            var diagnostics = new CultMeshDiagnosticBuffer();
+            var client = new CultMeshVerseDiscoveryClient(new CultMeshVerseDiscoveryClientOptions
+            {
+                CreateClient = () => new NeverConnectedSchemaClient(),
+                Clock = clock,
+                Diagnostics = diagnostics,
+                SourceId = "test-bootstrap",
+                ConnectTimeout = TimeSpan.FromMilliseconds(50)
+            });
+
+            var error = Assert.ThrowsAsync<TimeoutException>(() =>
+                client.FetchAsync("rudp://unavailable.example.test:4075"));
+            Assert.That(error!.Message, Does.Contain("unavailable.example.test"));
+
+            var timeline = diagnostics.Snapshot();
+            Assert.That(timeline.Select(item => item.Kind), Is.EqualTo(new[]
+            {
+                CultMeshDiagnosticKind.ConnectionAttempt,
+                CultMeshDiagnosticKind.CandidateRejected
+            }));
+            Assert.That(timeline[0].ObservedAtUtc, Is.EqualTo(new DateTimeOffset(2026, 7, 12, 18, 0, 0, TimeSpan.Zero)));
+            Assert.That(timeline[1].ObservedAtUtc, Is.EqualTo(new DateTimeOffset(2026, 7, 12, 18, 0, 0, 50, TimeSpan.Zero)));
+            Assert.That(timeline[1].State, Is.EqualTo("unavailable"));
+            Assert.That(timeline[1].ReasonCode, Is.EqualTo("timeout"));
+            Assert.That(timeline[1].SourceId, Is.EqualTo("test-bootstrap"));
+            Assert.That(timeline[1].LibraryVersion, Is.Not.Empty);
+        }
+
         [Test]
         public async Task CultMeshPeerExchangeClient_Uses_SchemaClientPort()
         {
@@ -4912,6 +4944,45 @@ namespace GameCult.Networking.Tests
             }
         }
 
+        private sealed class NeverConnectedSchemaClient : ICultNetSchemaClient
+        {
+            public bool Connected => false;
+
+            public void Connect(string host, int port)
+            {
+            }
+
+            public void SendCultNet<T>(T message) where T : ICultNetSchemaMessage
+            {
+                throw new InvalidOperationException("A disconnected client cannot send.");
+            }
+
+            public void OnCultNet<T>(Action<T> callback) where T : ICultNetSchemaMessage
+            {
+            }
+
+            public void Dispose()
+            {
+            }
+        }
+
+        private sealed class ManualCultMeshClock : ICultMeshClock
+        {
+            public ManualCultMeshClock(DateTimeOffset utcNow)
+            {
+                UtcNow = utcNow;
+            }
+
+            public DateTimeOffset UtcNow { get; private set; }
+
+            public Task DelayAsync(TimeSpan delay, CancellationToken cancellationToken = default)
+            {
+                cancellationToken.ThrowIfCancellationRequested();
+                UtcNow += delay;
+                return Task.CompletedTask;
+            }
+        }
+
         [MessagePack.MessagePackObject]
         public sealed class PlayerDataPayload
         {