refactor(net): own complete live session lifecycle

src/AcDream.App/Net/LiveSessionController.cs

@@ -1,114 +1,688 @@
-using System;
 using System.Net;
 using System.Net.Sockets;
 using AcDream.Core.Net;
+using AcDream.Core.Net.Messages;
+using AcDream.UI.Abstractions;
 
 namespace AcDream.App.Net;
 
-/// <summary>
+internal enum LiveSessionStartStatus
-/// Owns the network-side lifecycle of a live <see cref="WorldSession"/> —
-/// DNS resolution, endpoint construction, session instantiation, per-frame
-/// <c>Tick</c>, and disposal. The post-construction work (event wiring,
-/// <c>Connect</c>, character validation, <c>EnterWorld</c>, post-login UI
-/// state setup) stays in <c>GameWindow</c> for now because it touches
-/// renderer / chat / player-controller state that hasn't been extracted yet.
-/// </summary>
-/// <remarks>
-/// <para>
-/// Step 2 of the extraction sequence described in
-/// <c>docs/architecture/code-structure.md</c> §4. Future expansions can
-/// fold more of <c>TryStartLiveSession</c> into this controller as the
-/// surrounding state (event handlers, command bus, settings VM) gets
-/// extracted in later steps.
-/// </para>
-/// <para>
-/// <strong>Behavior preservation contract:</strong> this class produces
-/// byte-identical console output and event-wireup sequencing to the
-/// pre-refactor inline code path. The DNS-resolution lines, the
-/// "live: connecting to ..." line, and the wiring-vs-Connect ordering
-/// all match the previous flow.
-/// </para>
-/// </remarks>
-public sealed class LiveSessionController : IDisposable
 {
-    /// <summary>
+    Disabled,
-    /// Active session, or <see langword="null"/> when offline / before
+    MissingCredentials,
-    /// <see cref="CreateAndWire"/> succeeded / after <see cref="Dispose"/>.
+    NoCharacters,
-    /// </summary>
+    Connected,
-    public WorldSession? Session { get; private set; }
+    Deferred,
+    Failed,
+}
 
-    /// <summary>
+internal sealed record LiveSessionCharacterSelection(
-    /// Resolves the endpoint, instantiates the <see cref="WorldSession"/>,
+    int ActiveIndex,
-    /// hands it to <paramref name="wireEvents"/> for caller-side event
+    uint CharacterId,
-    /// subscriptions, and returns the live session. The caller is
+    string CharacterName,
-    /// responsible for the subsequent <c>Connect</c> /
+    string AccountName);
-    /// <c>EnterWorld</c> dance.
+
-    /// </summary>
+internal sealed record LiveSessionStartResult(
-    public WorldSession? CreateAndWire(RuntimeOptions options, Action<WorldSession> wireEvents)
+    LiveSessionStartStatus Status,
+    LiveSessionCharacterSelection? Selection = null,
+    Exception? Error = null);
+
+/// <summary>
+/// Narrow App composition boundary for one exact WorldSession generation.
+/// The host owns domain sinks and presentation state; the controller owns the
+/// connect/enter/stop transaction and never reaches into GameWindow state.
+/// </summary>
+internal interface ILiveSessionLifecycleHost
+{
+    LiveSessionBinding BindSession(WorldSession session);
+    void ResetSessionState();
+    void ReportConnecting(string host, int port, string user);
+    void ReportConnected();
+    void ApplySelectedCharacter(LiveSessionCharacterSelection selection);
+    void ApplyEnteredWorld(LiveSessionCharacterSelection selection);
+    void DetachSession(WorldSession session);
+}
+
+/// <summary>
+/// Owns routing and commands for one exact session. Teardown is ordered and
+/// retryable: outbound commands become inert before inbound subscriptions are
+/// detached.
+/// </summary>
+internal sealed class LiveSessionBinding : IDisposable
+{
+    private readonly Action _activateCommands;
+    private readonly Action _deactivateCommands;
+    private readonly Action _detachEvents;
+    private bool _commandsDeactivated;
+    private bool _eventsDetached;
+    private bool _commandsActivated;
+
+    public LiveSessionBinding(
+        WorldSession session,
+        ICommandBus commands,
+        Action activateCommands,
+        Action deactivateCommands,
+        Action detachEvents)
     {
-        if (options is null) throw new ArgumentNullException(nameof(options));
+        Session = session ?? throw new ArgumentNullException(nameof(session));
-        if (wireEvents is null) throw new ArgumentNullException(nameof(wireEvents));
+        Commands = commands ?? throw new ArgumentNullException(nameof(commands));
-
+        _activateCommands = activateCommands ?? throw new ArgumentNullException(nameof(activateCommands));
-        if (!options.LiveMode) return null;
+        _deactivateCommands = deactivateCommands ?? throw new ArgumentNullException(nameof(deactivateCommands));
-
+        _detachEvents = detachEvents ?? throw new ArgumentNullException(nameof(detachEvents));
-        if (string.IsNullOrEmpty(options.LiveUser) || string.IsNullOrEmpty(options.LivePass))
-        {
-            Console.WriteLine("live: ACDREAM_LIVE set but TEST_USER/TEST_PASS missing; skipping");
-            return null;
-        }
-
-        try
-        {
-            var endpoint = ResolveEndpoint(options.LiveHost, options.LivePort);
-            Console.WriteLine($"live: connecting to {endpoint} as {options.LiveUser}");
-            Session = new WorldSession(endpoint);
-            wireEvents(Session);
-            return Session;
-        }
-        catch (Exception ex)
-        {
-            Console.WriteLine($"live: session setup failed: {ex.Message}");
-            Session?.Dispose();
-            Session = null;
-            return null;
-        }
     }
 
-    /// <summary>
+    public WorldSession Session { get; }
-    /// Drains the inbound network queue. Proxies to
+    public ICommandBus Commands { get; }
-    /// <see cref="WorldSession.Tick"/>; no-op when <see cref="Session"/>
+
-    /// is <see langword="null"/>.
+    public void ActivateCommands()
-    /// </summary>
+    {
-    public void Tick() => Session?.Tick();
+        if (_commandsDeactivated || _eventsDetached)
+            throw new ObjectDisposedException(nameof(LiveSessionBinding));
+        if (_commandsActivated)
+            return;
+        _activateCommands();
+        if (_commandsDeactivated || _eventsDetached)
+            return;
+        _commandsActivated = true;
+    }
 
-    /// <summary>
-    /// Tears down the live session. Safe to call multiple times.
-    /// </summary>
     public void Dispose()
     {
-        Session?.Dispose();
+        if (!_commandsDeactivated)
-        Session = null;
+        {
+            _deactivateCommands();
+            _commandsDeactivated = true;
+        }
+        if (!_eventsDetached)
+        {
+            _detachEvents();
+            _eventsDetached = true;
+        }
     }
+}
 
-    /// <summary>
+internal interface ILiveSessionOperations
-    /// Resolve a host string (literal IP or DNS name) to an
+{
-    /// <see cref="IPEndPoint"/>. Pre-refactor logic preserved exactly:
+    IPEndPoint ResolveEndpoint(string host, int port);
-    /// try <see cref="IPAddress.TryParse"/> first, fall back to
+    WorldSession CreateSession(IPEndPoint endpoint);
-    /// <see cref="Dns.GetHostAddresses"/>, prefer IPv4 (ACE + retail use
+    void Connect(WorldSession session, string user, string password);
-    /// IPv4 UDP exclusively), throw on empty resolution.
+    CharacterList.Parsed? GetCharacters(WorldSession session);
-    /// </summary>
+    void EnterWorld(WorldSession session, int activeCharacterIndex);
-    private static IPEndPoint ResolveEndpoint(string host, int port)
+    void Tick(WorldSession session);
+    void DisposeSession(WorldSession session);
+}
+
+internal sealed class ProductionLiveSessionOperations : ILiveSessionOperations
+{
+    public static ProductionLiveSessionOperations Instance { get; } = new();
+
+    private ProductionLiveSessionOperations() { }
+
+    public IPEndPoint ResolveEndpoint(string host, int port)
     {
         IPAddress ip;
         if (!IPAddress.TryParse(host, out ip!))
         {
-            var addrs = Dns.GetHostAddresses(host);
+            IPAddress[] addresses = Dns.GetHostAddresses(host);
-            ip = Array.Find(addrs, a => a.AddressFamily == AddressFamily.InterNetwork)
+            ip = Array.Find(
-                ?? (addrs.Length > 0
+                    addresses,
-                    ? addrs[0]
+                    static address => address.AddressFamily == AddressFamily.InterNetwork)
-                    : throw new Exception($"DNS resolved no addresses for '{host}'"));
+                ?? (addresses.Length != 0
+                    ? addresses[0]
+                    : throw new InvalidOperationException(
+                        $"DNS resolved no addresses for '{host}'"));
             Console.WriteLine($"live: resolved {host} → {ip}");
         }
         return new IPEndPoint(ip, port);
     }
+
+    public WorldSession CreateSession(IPEndPoint endpoint) => new(endpoint);
+
+    public void Connect(WorldSession session, string user, string password) =>
+        session.Connect(user, password);
+
+    public CharacterList.Parsed? GetCharacters(WorldSession session) => session.Characters;
+
+    public void EnterWorld(WorldSession session, int activeCharacterIndex) =>
+        session.EnterWorld(activeCharacterIndex);
+
+    public void Tick(WorldSession session) => session.Tick();
+
+    public void DisposeSession(WorldSession session) => session.Dispose();
+}
+
+/// <summary>
+/// Sole owner of the App lifetime for a live WorldSession: endpoint resolution,
+/// complete pre-Connect routing, character validation/entry, active command
+/// publication, exact-generation Tick, graceful replacement, and convergent
+/// teardown. Retail wire behavior remains inside WorldSession.
+/// </summary>
+public sealed class LiveSessionController : IDisposable
+{
+    private sealed class SessionScope(
+        WorldSession session,
+        ILiveSessionLifecycleHost host)
+    {
+        private int _teardownStage;
+
+        public WorldSession Session { get; } = session;
+        public ILiveSessionLifecycleHost Host { get; } = host;
+        public LiveSessionBinding? Binding { get; set; }
+        public bool HostAttached { get; set; }
+
+        public void DrainTeardown(ILiveSessionOperations operations)
+        {
+            if (_teardownStage == 0)
+            {
+                Binding?.Dispose();
+                _teardownStage = 1;
+            }
+            if (_teardownStage == 1)
+            {
+                operations.DisposeSession(Session);
+                _teardownStage = 2;
+            }
+            if (_teardownStage == 2)
+            {
+                if (HostAttached)
+                    Host.DetachSession(Session);
+                _teardownStage = 3;
+            }
+            if (_teardownStage == 3)
+            {
+                Host.ResetSessionState();
+                _teardownStage = 4;
+            }
+        }
+
+        public bool IsTeardownComplete => _teardownStage == 4;
+    }
+
+    private enum PendingKind
+    {
+        Stop,
+        Reconnect,
+        Dispose,
+    }
+
+    private sealed record PendingOperation(
+        PendingKind Kind,
+        RuntimeOptions? Options = null,
+        ILiveSessionLifecycleHost? Host = null);
+
+    private readonly object _gate = new();
+    private readonly ILiveSessionOperations _operations;
+    private SessionScope? _scope;
+    private SessionScope? _retiredScope;
+    private ILiveSessionLifecycleHost? _pendingInitialResetHost;
+    private PendingOperation? _pendingOperation;
+    private WorldSession? _legacySession;
+    private int _operationDepth;
+    private bool _inWorld;
+    private bool _disposeRequested;
+    private bool _disposed;
+    private ulong _generation;
+    private LiveSessionCharacterSelection? _activeSelection;
+
+    public LiveSessionController()
+        : this(ProductionLiveSessionOperations.Instance)
+    {
+    }
+
+    internal LiveSessionController(ILiveSessionOperations operations)
+    {
+        _operations = operations ?? throw new ArgumentNullException(nameof(operations));
+    }
+
+    public WorldSession? CurrentSession
+    {
+        get { lock (_gate) return _scope?.Session ?? _legacySession; }
+    }
+
+    /// <summary>Temporary Slice-3 compatibility alias; removed at GameWindow cutover.</summary>
+    public WorldSession? Session => CurrentSession;
+
+    public ICommandBus Commands
+    {
+        get
+        {
+            lock (_gate)
+                return _inWorld && _scope?.Binding is { } binding
+                    ? binding.Commands
+                    : NullCommandBus.Instance;
+        }
+    }
+
+    public bool IsInWorld
+    {
+        get { lock (_gate) return _inWorld; }
+    }
+
+    public ulong SessionGeneration
+    {
+        get { lock (_gate) return _generation; }
+    }
+
+    internal LiveSessionStartResult Start(
+        RuntimeOptions options,
+        ILiveSessionLifecycleHost host)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+        ArgumentNullException.ThrowIfNull(host);
+        lock (_gate)
+        {
+            ThrowIfDisposing();
+            if (_operationDepth != 0)
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+            if (_inWorld)
+                return ConnectedResult();
+            return RunTopLevel(() => StartCore(options, host, resetHost: true));
+        }
+    }
+
+    internal LiveSessionStartResult Reconnect(
+        RuntimeOptions options,
+        ILiveSessionLifecycleHost host)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+        ArgumentNullException.ThrowIfNull(host);
+        lock (_gate)
+        {
+            ThrowIfDisposing();
+            if (_operationDepth != 0)
+            {
+                Schedule(new PendingOperation(PendingKind.Reconnect, options, host));
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+            }
+            return RunTopLevel(() => ReconnectCore(options, host));
+        }
+    }
+
+    internal void Stop()
+    {
+        lock (_gate)
+        {
+            if (_disposed)
+                return;
+            if (_operationDepth != 0)
+            {
+                Schedule(new PendingOperation(PendingKind.Stop));
+                return;
+            }
+            RunTopLevel(StopCore);
+        }
+    }
+
+    public void Tick()
+    {
+        lock (_gate)
+        {
+            if (_disposed)
+                return;
+            if (_legacySession is not null && _scope is null)
+            {
+                _legacySession.Tick();
+                return;
+            }
+            if (!_inWorld || _scope is null || _operationDepth != 0)
+                return;
+
+            RunTopLevel(() =>
+            {
+                SessionScope scope = _scope;
+                ulong generation = _generation;
+                try
+                {
+                    _operations.Tick(scope.Session);
+                    if (!IsCurrent(scope, generation))
+                        return;
+                }
+                catch (Exception tickError)
+                {
+                    Exception error = StopAfterFailure(tickError);
+                    throw error;
+                }
+            });
+        }
+    }
+
+    public void Dispose()
+    {
+        lock (_gate)
+        {
+            if (_disposed)
+                return;
+            _disposeRequested = true;
+            if (_operationDepth != 0)
+            {
+                Schedule(new PendingOperation(PendingKind.Dispose));
+                return;
+            }
+
+            RunTopLevel(DisposeCore);
+        }
+    }
+
+    private LiveSessionStartResult ReconnectCore(
+        RuntimeOptions options,
+        ILiveSessionLifecycleHost host)
+    {
+        ILiveSessionLifecycleHost? oldHost =
+            _scope?.Host ?? _retiredScope?.Host ?? _pendingInitialResetHost;
+        ulong generationBeforeStop = _generation;
+        try
+        {
+            StopCore();
+        }
+        catch (Exception error)
+        {
+            return new LiveSessionStartResult(LiveSessionStartStatus.Failed, Error: error);
+        }
+        if (_generation != unchecked(generationBeforeStop + 1))
+            return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+        return StartCore(options, host, resetHost: !ReferenceEquals(oldHost, host));
+    }
+
+    private LiveSessionStartResult StartCore(
+        RuntimeOptions options,
+        ILiveSessionLifecycleHost host,
+        bool resetHost)
+    {
+        ulong generation = ++_generation;
+        try
+        {
+            DrainRetiredScope();
+            if (_generation != generation)
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+            if (resetHost)
+                ResetHostBeforeStart(host, generation);
+            if (_generation != generation)
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+        }
+        catch (Exception error)
+        {
+            return new LiveSessionStartResult(LiveSessionStartStatus.Failed, Error: error);
+        }
+
+        if (!options.LiveMode)
+            return new LiveSessionStartResult(LiveSessionStartStatus.Disabled);
+        if (string.IsNullOrEmpty(options.LiveUser) || string.IsNullOrEmpty(options.LivePass))
+            return new LiveSessionStartResult(LiveSessionStartStatus.MissingCredentials);
+
+        SessionScope? scope = null;
+        try
+        {
+            IPEndPoint endpoint = _operations.ResolveEndpoint(options.LiveHost, options.LivePort);
+            if (_generation != generation)
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+            Console.WriteLine($"live: connecting to {endpoint} as {options.LiveUser}");
+            WorldSession session = _operations.CreateSession(endpoint);
+            scope = new SessionScope(session, host);
+            _scope = scope;
+            _inWorld = false;
+            if (!IsCurrent(scope, generation))
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+
+            LiveSessionBinding binding = host.BindSession(session);
+            scope.Binding = binding;
+            scope.HostAttached = true;
+            if (!ReferenceEquals(binding.Session, session))
+            {
+                throw new InvalidOperationException(
+                    "The live-session host returned a binding for a different session.");
+            }
+            if (!IsCurrent(scope, generation))
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+
+            host.ReportConnecting(options.LiveHost, options.LivePort, options.LiveUser);
+            if (!IsCurrent(scope, generation))
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+
+            _operations.Connect(session, options.LiveUser, options.LivePass);
+            if (!IsCurrent(scope, generation))
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+            host.ReportConnected();
+            if (!IsCurrent(scope, generation))
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+
+            CharacterList.Parsed? characters = _operations.GetCharacters(session);
+            if (characters is null
+                || !CharacterList.TrySelectFirstAvailable(characters, out CharacterList.Selection selected))
+            {
+                Console.WriteLine("live: no available characters on account; disconnecting");
+                StopCore();
+                return new LiveSessionStartResult(LiveSessionStartStatus.NoCharacters);
+            }
+
+            var selection = new LiveSessionCharacterSelection(
+                selected.ActiveIndex,
+                selected.Character.Id,
+                selected.Character.Name,
+                characters.AccountName);
+            host.ApplySelectedCharacter(selection);
+            if (!IsCurrent(scope, generation))
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+
+            Console.WriteLine(
+                $"live: entering world as 0x{selection.CharacterId:X8} {selection.CharacterName}");
+            _operations.EnterWorld(session, selection.ActiveIndex);
+            if (!IsCurrent(scope, generation))
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+
+            binding.ActivateCommands();
+            if (!IsCurrent(scope, generation))
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+            _inWorld = true;
+            _activeSelection = selection;
+            host.ApplyEnteredWorld(selection);
+            if (!IsCurrent(scope, generation))
+                return new LiveSessionStartResult(LiveSessionStartStatus.Deferred);
+
+            Console.WriteLine("live: in world — CreateObject stream active");
+            return new LiveSessionStartResult(
+                LiveSessionStartStatus.Connected,
+                selection);
+        }
+        catch (Exception startError)
+        {
+            return new LiveSessionStartResult(
+                LiveSessionStartStatus.Failed,
+                Error: StopAfterFailure(startError));
+        }
+    }
+
+    private Exception StopAfterFailure(Exception operationError)
+    {
+        try
+        {
+            StopCore();
+            return operationError;
+        }
+        catch (Exception cleanupError)
+        {
+            return new AggregateException(
+                "Live-session operation and cleanup both failed.",
+                operationError,
+                cleanupError);
+        }
+    }
+
+    private void StopCore()
+    {
+        ++_generation;
+        _inWorld = false;
+        _activeSelection = null;
+        if (_scope is { } scope)
+        {
+            _scope = null;
+            if (_retiredScope is not null && !ReferenceEquals(_retiredScope, scope))
+                throw new InvalidOperationException(
+                    "A second live-session scope cannot retire before the first converges.");
+            _retiredScope = scope;
+        }
+        DrainRetiredScope();
+        DrainPendingInitialReset();
+    }
+
+    private void DrainRetiredScope()
+    {
+        if (_retiredScope is not { } retired)
+            return;
+        retired.DrainTeardown(_operations);
+        if (retired.IsTeardownComplete)
+            _retiredScope = null;
+    }
+
+    private void ResetHostBeforeStart(
+        ILiveSessionLifecycleHost host,
+        ulong generation)
+    {
+        bool requestedHostAlreadyReset = false;
+        if (_pendingInitialResetHost is { } pending)
+        {
+            pending.ResetSessionState();
+            _pendingInitialResetHost = null;
+            requestedHostAlreadyReset = ReferenceEquals(pending, host);
+        }
+        if (requestedHostAlreadyReset || _generation != generation)
+            return;
+
+        try
+        {
+            host.ResetSessionState();
+        }
+        catch
+        {
+            _pendingInitialResetHost = host;
+            throw;
+        }
+    }
+
+    private void DrainPendingInitialReset()
+    {
+        if (_pendingInitialResetHost is not { } host)
+            return;
+        host.ResetSessionState();
+        _pendingInitialResetHost = null;
+    }
+
+    private void Schedule(PendingOperation operation)
+    {
+        if (_pendingOperation?.Kind == PendingKind.Dispose)
+            return;
+        _pendingOperation = operation;
+        ++_generation;
+        _inWorld = false;
+        _scope?.Binding?.Dispose();
+    }
+
+    private T RunTopLevel<T>(Func<T> operation)
+    {
+        _operationDepth++;
+        try
+        {
+            return operation();
+        }
+        finally
+        {
+            _operationDepth--;
+            if (_operationDepth == 0)
+                DrainPendingOperations();
+        }
+    }
+
+    private void RunTopLevel(Action operation) =>
+        RunTopLevel(() =>
+        {
+            operation();
+            return true;
+        });
+
+    private void DrainPendingOperations()
+    {
+        while (_pendingOperation is { } pending)
+        {
+            _pendingOperation = null;
+            _operationDepth++;
+            try
+            {
+                switch (pending.Kind)
+                {
+                    case PendingKind.Stop:
+                        StopCore();
+                        break;
+                    case PendingKind.Reconnect:
+                        _ = ReconnectCore(pending.Options!, pending.Host!);
+                        break;
+                    case PendingKind.Dispose:
+                        DisposeCore();
+                        break;
+                }
+            }
+            finally
+            {
+                _operationDepth--;
+            }
+        }
+    }
+
+    private void DisposeCore()
+    {
+        StopCore();
+        if (_legacySession is { } legacy)
+        {
+            _operations.DisposeSession(legacy);
+            _legacySession = null;
+        }
+        _disposed = true;
+    }
+
+    private bool IsCurrent(SessionScope scope, ulong generation) =>
+        ReferenceEquals(_scope, scope) && _generation == generation;
+
+    private LiveSessionStartResult ConnectedResult()
+        => new(LiveSessionStartStatus.Connected, _activeSelection);
+
+    private void ThrowIfDisposing()
+    {
+        if (_disposeRequested || _disposed)
+            throw new ObjectDisposedException(nameof(LiveSessionController));
+    }
+
+    // Temporary compatibility surface for Slice 3 Commit E. The complete
+    // controller above is exercised independently before GameWindow cuts over.
+    public WorldSession? CreateAndWire(RuntimeOptions options, Action<WorldSession> wireEvents)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+        ArgumentNullException.ThrowIfNull(wireEvents);
+        lock (_gate)
+        {
+            ThrowIfDisposing();
+            if (!options.LiveMode)
+                return null;
+            if (string.IsNullOrEmpty(options.LiveUser) || string.IsNullOrEmpty(options.LivePass))
+            {
+                Console.WriteLine(
+                    "live: ACDREAM_LIVE set but TEST_USER/TEST_PASS missing; skipping");
+                return null;
+            }
+
+            try
+            {
+                IPEndPoint endpoint = _operations.ResolveEndpoint(options.LiveHost, options.LivePort);
+                Console.WriteLine($"live: connecting to {endpoint} as {options.LiveUser}");
+                _legacySession = _operations.CreateSession(endpoint);
+                wireEvents(_legacySession);
+                return _legacySession;
+            }
+            catch (Exception error)
+            {
+                Console.WriteLine($"live: session setup failed: {error.Message}");
+                if (_legacySession is not null)
+                    _operations.DisposeSession(_legacySession);
+                _legacySession = null;
+                return null;
+            }
+        }
+    }
 }

src/AcDream.Core.Net/AcDream.Core.Net.csproj

@@ -12,5 +12,6 @@
   </ItemGroup>
   <ItemGroup>
     <InternalsVisibleTo Include="AcDream.Core.Net.Tests" />
+    <InternalsVisibleTo Include="AcDream.App.Tests" />
   </ItemGroup>
 </Project>

src/AcDream.Core.Net/WorldSession.cs

@@ -10,6 +10,29 @@ using AcDream.Core.Net.Packets;
 
 namespace AcDream.Core.Net;
 
+internal interface IWorldSessionTransport : IDisposable
+{
+    void Send(ReadOnlySpan<byte> datagram);
+    void Send(IPEndPoint remote, ReadOnlySpan<byte> datagram);
+    byte[]? Receive(TimeSpan timeout, out IPEndPoint? from);
+}
+
+internal sealed class NetClientWorldSessionTransport(IPEndPoint remote)
+    : IWorldSessionTransport
+{
+    private readonly NetClient _client = new(remote);
+
+    public void Send(ReadOnlySpan<byte> datagram) => _client.Send(datagram);
+
+    public void Send(IPEndPoint endpoint, ReadOnlySpan<byte> datagram) =>
+        _client.Send(endpoint, datagram);
+
+    public byte[]? Receive(TimeSpan timeout, out IPEndPoint? from) =>
+        _client.Receive(timeout, out from);
+
+    public void Dispose() => _client.Dispose();
+}
+
 /// <summary>
 /// High-level AC client session: owns a <see cref="NetClient"/>, drives
 /// the full handshake + character-enter-world flow, and converts the
@@ -600,7 +623,7 @@ public sealed class WorldSession : IDisposable
 
     public CharacterList.Parsed? Characters { get; private set; }
 
-    private readonly NetClient _net;
+    private readonly IWorldSessionTransport _net;
     private long _lastInboundPacketTicks = Stopwatch.GetTimestamp();
     private long _lastPingRequestTicks;
     private long _lastPingRoundTripBits = BitConverter.DoubleToInt64Bits(double.NaN);
@@ -676,10 +699,34 @@ public sealed class WorldSession : IDisposable
     private uint _gameActionSequence;
 
     public WorldSession(IPEndPoint serverLogin)
+        : this(
+            serverLogin,
+            static endpoint => new NetClientWorldSessionTransport(endpoint))
     {
+    }
+
+    internal WorldSession(
+        IPEndPoint serverLogin,
+        IWorldSessionTransport transport)
+        : this(serverLogin, _ => transport)
+    {
+    }
+
+    internal WorldSession(
+        IPEndPoint serverLogin,
+        Func<IPEndPoint, IWorldSessionTransport> transportFactory)
+    {
+        ArgumentNullException.ThrowIfNull(serverLogin);
+        ArgumentNullException.ThrowIfNull(transportFactory);
+        if (serverLogin.Port == ushort.MaxValue)
+            throw new ArgumentOutOfRangeException(
+                nameof(serverLogin),
+                "The login endpoint must leave room for the adjacent connect port.");
+
         _loginEndpoint = serverLogin;
         _connectEndpoint = new IPEndPoint(serverLogin.Address, serverLogin.Port + 1);
-        _net = new NetClient(serverLogin);
+        _net = transportFactory(serverLogin)
+            ?? throw new InvalidOperationException("The session transport factory returned null.");
 
         // Phase I.6: SetTurbineChatChannels (0x0295) is a GameEvent
         // sub-opcode of 0xF7B0, not a top-level opcode. Route it through

tests/AcDream.App.Tests/Net/LiveSessionControllerTests.cs

@@ -0,0 +1,864 @@
+using System.Net;
+using AcDream.App.Net;
+using AcDream.Core.Net;
+using AcDream.Core.Net.Messages;
+using AcDream.UI.Abstractions;
+
+namespace AcDream.App.Tests.Net;
+
+public sealed class LiveSessionControllerTests
+{
+    private sealed class TestTransport : IWorldSessionTransport
+    {
+        public void Send(ReadOnlySpan<byte> datagram) { }
+
+        public void Send(IPEndPoint remote, ReadOnlySpan<byte> datagram) { }
+
+        public byte[]? Receive(TimeSpan timeout, out IPEndPoint? from)
+        {
+            from = null;
+            return null;
+        }
+
+        public void Dispose() { }
+    }
+
+    private sealed class TestCommandBus : ICommandBus
+    {
+        public bool Active { get; set; }
+        public int PublishCount { get; private set; }
+
+        public void Publish<T>(T command) where T : notnull
+        {
+            if (Active)
+                PublishCount++;
+        }
+    }
+
+    private sealed class TestOperations(List<string> calls) : ILiveSessionOperations
+    {
+        public CharacterList.Parsed? Characters { get; set; } = AvailableCharacters();
+        public Action? OnResolve { get; set; }
+        public Action? OnCreate { get; set; }
+        public Action? OnConnect { get; set; }
+        public Action? OnCharacters { get; set; }
+        public Action? OnEnterWorld { get; set; }
+        public Action? OnTick { get; set; }
+        public Action? OnDispose { get; set; }
+        public bool ThrowOnConnect { get; set; }
+        public bool ThrowOnCreate { get; set; }
+        public bool ThrowOnCharacters { get; set; }
+        public bool ThrowOnEnterWorld { get; set; }
+        public bool ThrowOnTick { get; set; }
+        public bool FailDisposeOnce { get; set; }
+        public List<WorldSession> Sessions { get; } = [];
+        public Dictionary<WorldSession, int> DisposeCounts { get; } = [];
+        public int EnterWorldCount { get; private set; }
+        public int TickCount { get; private set; }
+
+        public IPEndPoint ResolveEndpoint(string host, int port)
+        {
+            calls.Add("resolve");
+            OnResolve?.Invoke();
+            return new IPEndPoint(IPAddress.Loopback, port);
+        }
+
+        public WorldSession CreateSession(IPEndPoint endpoint)
+        {
+            calls.Add("create");
+            OnCreate?.Invoke();
+            if (ThrowOnCreate)
+                throw new InvalidOperationException("create failure");
+            var session = new WorldSession(endpoint, new TestTransport());
+            Sessions.Add(session);
+            return session;
+        }
+
+        public void Connect(WorldSession session, string user, string password)
+        {
+            calls.Add("connect");
+            OnConnect?.Invoke();
+            if (ThrowOnConnect)
+                throw new InvalidOperationException("connect failure");
+        }
+
+        public CharacterList.Parsed? GetCharacters(WorldSession session)
+        {
+            OnCharacters?.Invoke();
+            if (ThrowOnCharacters)
+                throw new InvalidOperationException("characters failure");
+            return Characters;
+        }
+
+        public void EnterWorld(WorldSession session, int activeCharacterIndex)
+        {
+            calls.Add($"enter:{activeCharacterIndex}");
+            EnterWorldCount++;
+            OnEnterWorld?.Invoke();
+            if (ThrowOnEnterWorld)
+                throw new InvalidOperationException("enter failure");
+        }
+
+        public void Tick(WorldSession session)
+        {
+            calls.Add("tick");
+            TickCount++;
+            OnTick?.Invoke();
+            if (ThrowOnTick)
+                throw new InvalidOperationException("tick failure");
+        }
+
+        public void DisposeSession(WorldSession session)
+        {
+            calls.Add("dispose-session");
+            OnDispose?.Invoke();
+            if (FailDisposeOnce)
+            {
+                FailDisposeOnce = false;
+                throw new InvalidOperationException("dispose failure");
+            }
+            DisposeCounts[session] = DisposeCounts.GetValueOrDefault(session) + 1;
+        }
+    }
+
+    private sealed class TestHost(List<string> calls) : ILiveSessionLifecycleHost
+    {
+        public Action? OnBind { get; set; }
+        public Action? OnReset { get; set; }
+        public Action? OnConnecting { get; set; }
+        public Action? OnConnected { get; set; }
+        public Action? OnSelected { get; set; }
+        public Action? OnActivate { get; set; }
+        public Action? OnEntered { get; set; }
+        public Action? OnDetach { get; set; }
+        public bool FailResetOnce { get; set; }
+        public bool FailDetachOnce { get; set; }
+        public bool FailDeactivateOnce { get; set; }
+        public bool FailEventDetachOnce { get; set; }
+        public bool ThrowOnBind { get; set; }
+        public bool ThrowOnConnecting { get; set; }
+        public bool ThrowOnConnected { get; set; }
+        public bool ThrowOnSelected { get; set; }
+        public bool ThrowOnActivate { get; set; }
+        public bool ThrowOnEntered { get; set; }
+        public WorldSession? BindingSessionOverride { get; set; }
+        public int ResetCount { get; private set; }
+        public int DetachCount { get; private set; }
+        public int DeactivateCount { get; private set; }
+        public int EventDetachCount { get; private set; }
+        public int ActivateCount { get; private set; }
+        public List<TestCommandBus> CommandBuses { get; } = [];
+        public List<LiveSessionCharacterSelection> Selections { get; } = [];
+
+        public LiveSessionBinding BindSession(WorldSession session)
+        {
+            calls.Add("bind");
+            OnBind?.Invoke();
+            if (ThrowOnBind)
+                throw new InvalidOperationException("bind failure");
+            var commands = new TestCommandBus();
+            CommandBuses.Add(commands);
+            return new LiveSessionBinding(
+                BindingSessionOverride ?? session,
+                commands,
+                activateCommands: () =>
+                {
+                    calls.Add("activate");
+                    ActivateCount++;
+                    commands.Active = true;
+                    OnActivate?.Invoke();
+                    if (ThrowOnActivate)
+                        throw new InvalidOperationException("activate failure");
+                },
+                deactivateCommands: () =>
+                {
+                    calls.Add("deactivate");
+                    DeactivateCount++;
+                    commands.Active = false;
+                    if (FailDeactivateOnce)
+                    {
+                        FailDeactivateOnce = false;
+                        throw new InvalidOperationException("deactivate failure");
+                    }
+                },
+                detachEvents: () =>
+                {
+                    calls.Add("detach-events");
+                    EventDetachCount++;
+                    if (FailEventDetachOnce)
+                    {
+                        FailEventDetachOnce = false;
+                        throw new InvalidOperationException("event detach failure");
+                    }
+                });
+        }
+
+        public void ResetSessionState()
+        {
+            calls.Add("reset");
+            ResetCount++;
+            OnReset?.Invoke();
+            if (FailResetOnce)
+            {
+                FailResetOnce = false;
+                throw new InvalidOperationException("reset failure");
+            }
+        }
+
+        public void ReportConnecting(string host, int port, string user)
+        {
+            calls.Add("report-connecting");
+            OnConnecting?.Invoke();
+            if (ThrowOnConnecting)
+                throw new InvalidOperationException("connecting failure");
+        }
+
+        public void ReportConnected()
+        {
+            calls.Add("report-connected");
+            OnConnected?.Invoke();
+            if (ThrowOnConnected)
+                throw new InvalidOperationException("connected failure");
+        }
+
+        public void ApplySelectedCharacter(LiveSessionCharacterSelection selection)
+        {
+            calls.Add("selected");
+            Selections.Add(selection);
+            OnSelected?.Invoke();
+            if (ThrowOnSelected)
+                throw new InvalidOperationException("selected failure");
+        }
+
+        public void ApplyEnteredWorld(LiveSessionCharacterSelection selection)
+        {
+            calls.Add("entered");
+            OnEntered?.Invoke();
+            if (ThrowOnEntered)
+                throw new InvalidOperationException("entered failure");
+        }
+
+        public void DetachSession(WorldSession session)
+        {
+            calls.Add("detach-session");
+            DetachCount++;
+            OnDetach?.Invoke();
+            if (FailDetachOnce)
+            {
+                FailDetachOnce = false;
+                throw new InvalidOperationException("detach failure");
+            }
+        }
+    }
+
+    public enum ReentrantStopPoint
+    {
+        Reset,
+        Resolve,
+        Create,
+        Bind,
+        Connecting,
+        Connect,
+        Connected,
+        Selected,
+        EnterWorld,
+        Activate,
+        Entered,
+    }
+
+    [Fact]
+    public void Start_BindsBeforeConnectAndPublishesCanonicalSelectionAfterEnterWorld()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+
+        LiveSessionStartResult result = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Connected, result.Status);
+        Assert.Equal(
+            [
+                "reset", "resolve", "create", "bind", "report-connecting",
+                "connect", "report-connected", "selected", "enter:1",
+                "activate", "entered",
+            ],
+            calls);
+        Assert.Equal(
+            new LiveSessionCharacterSelection(1, 0x50000002u, "Ready", "Canonical"),
+            result.Selection);
+        Assert.True(controller.IsInWorld);
+        Assert.Same(operations.Sessions[0], controller.CurrentSession);
+        Assert.Same(host.CommandBuses[0], controller.Commands);
+        Assert.True(host.CommandBuses[0].Active);
+    }
+
+    [Fact]
+    public void Start_DisabledAndMissingCredentialsResetButNeverConstructSession()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+
+        Assert.Equal(
+            LiveSessionStartStatus.Disabled,
+            controller.Start(LiveOptions(live: false), host).Status);
+        Assert.Equal(
+            LiveSessionStartStatus.MissingCredentials,
+            controller.Start(LiveOptions(user: null), host).Status);
+
+        Assert.Equal(2, host.ResetCount);
+        Assert.Empty(operations.Sessions);
+        Assert.Equal(NullCommandBus.Instance, controller.Commands);
+    }
+
+    [Fact]
+    public void Start_NoAvailableCharacterTearsDownExactScope()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls)
+        {
+            Characters = new CharacterList.Parsed(
+                0u,
+                [new CharacterList.Character(0x50000001u, "Grey", 5u)],
+                [],
+                11,
+                "Canonical",
+                true,
+                true),
+        };
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+
+        LiveSessionStartResult result = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.NoCharacters, result.Status);
+        Assert.False(controller.IsInWorld);
+        Assert.Null(controller.CurrentSession);
+        Assert.Equal(1, host.DeactivateCount);
+        Assert.Equal(1, host.EventDetachCount);
+        Assert.Equal(1, host.DetachCount);
+        Assert.Equal(2, host.ResetCount);
+        Assert.Equal(1, operations.DisposeCounts[operations.Sessions[0]]);
+    }
+
+    [Fact]
+    public void Start_ConnectFailureConvergesOffline()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls) { ThrowOnConnect = true };
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+
+        LiveSessionStartResult result = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Failed, result.Status);
+        Assert.Contains("connect failure", result.Error!.ToString());
+        Assert.False(controller.IsInWorld);
+        Assert.Null(controller.CurrentSession);
+        Assert.Equal(1, operations.DisposeCounts[operations.Sessions[0]]);
+        Assert.Equal(1, host.DetachCount);
+    }
+
+    [Theory]
+    [InlineData("create")]
+    [InlineData("bind")]
+    [InlineData("enter")]
+    public void Start_OtherConstructionAndEntryFailuresConvergeOffline(string phase)
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls)
+        {
+            ThrowOnCreate = phase == "create",
+            ThrowOnEnterWorld = phase == "enter",
+        };
+        var host = new TestHost(calls) { ThrowOnBind = phase == "bind" };
+        var controller = new LiveSessionController(operations);
+
+        LiveSessionStartResult result = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Failed, result.Status);
+        Assert.Contains($"{phase} failure", result.Error!.ToString());
+        Assert.False(controller.IsInWorld);
+        Assert.Null(controller.CurrentSession);
+        if (phase == "create")
+        {
+            Assert.Empty(operations.Sessions);
+            Assert.Equal(1, host.ResetCount);
+        }
+        else
+        {
+            Assert.Single(operations.Sessions);
+            Assert.Equal(1, operations.DisposeCounts[operations.Sessions[0]]);
+            Assert.Equal(2, host.ResetCount);
+        }
+        Assert.Equal(phase == "enter" ? 1 : 0, host.DetachCount);
+    }
+
+    [Fact]
+    public void Start_HealthyDuplicateIsIdempotent()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        LiveSessionStartResult first = controller.Start(LiveOptions(), host);
+
+        LiveSessionStartResult duplicate = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Connected, duplicate.Status);
+        Assert.Equal(first.Selection, duplicate.Selection);
+        Assert.Single(operations.Sessions);
+        Assert.Equal(1, host.ResetCount);
+        Assert.Equal(1, host.ActivateCount);
+    }
+
+    [Fact]
+    public void Reconnect_QuiescesAThenDisposesDetachesResetsBeforeConstructingB()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        controller.Start(LiveOptions(), host);
+        WorldSession sessionA = operations.Sessions[0];
+        TestCommandBus commandsA = host.CommandBuses[0];
+        calls.Clear();
+
+        LiveSessionStartResult result = controller.Reconnect(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Connected, result.Status);
+        Assert.Equal(
+            [
+                "deactivate", "detach-events", "dispose-session", "detach-session",
+                "reset", "resolve", "create", "bind", "report-connecting",
+                "connect", "report-connected", "selected", "enter:1",
+                "activate", "entered",
+            ],
+            calls);
+        commandsA.Publish(new object());
+        Assert.Equal(0, commandsA.PublishCount);
+        Assert.Equal(1, operations.DisposeCounts[sessionA]);
+        Assert.Equal(2, operations.Sessions.Count);
+        Assert.Same(operations.Sessions[1], controller.CurrentSession);
+    }
+
+    [Theory]
+    [InlineData("detach", "stop")]
+    [InlineData("detach", "dispose")]
+    [InlineData("detach", "reconnect")]
+    [InlineData("reset", "stop")]
+    [InlineData("reset", "dispose")]
+    [InlineData("reset", "reconnect")]
+    public void Reconnect_ReentrantTeardownRequestNeverPublishesSupersededB(
+        string callbackPhase,
+        string request)
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        controller.Start(LiveOptions(), host);
+        bool requested = false;
+        Action callback = () =>
+        {
+            if (requested)
+                return;
+            requested = true;
+            switch (request)
+            {
+                case "stop": controller.Stop(); break;
+                case "dispose": controller.Dispose(); break;
+                case "reconnect":
+                    Assert.Equal(
+                        LiveSessionStartStatus.Deferred,
+                        controller.Reconnect(LiveOptions(), host).Status);
+                    break;
+            }
+        };
+        if (callbackPhase == "detach")
+            host.OnDetach = callback;
+        else
+            host.OnReset = callback;
+
+        LiveSessionStartResult outer = controller.Reconnect(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Deferred, outer.Status);
+        Assert.Equal(request == "reconnect" ? 2 : 1, operations.Sessions.Count);
+        Assert.Equal(request == "reconnect", controller.IsInWorld);
+        if (request == "dispose")
+            Assert.Throws<ObjectDisposedException>(() => controller.Start(LiveOptions(), host));
+        controller.Dispose();
+    }
+
+    [Fact]
+    public void MismatchedBindingWithInterruptedDetachRetainsCleanupOwnershipForRetry()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        using var mismatchedSession = new WorldSession(
+            new IPEndPoint(IPAddress.Loopback, 9001),
+            new TestTransport());
+        var host = new TestHost(calls)
+        {
+            BindingSessionOverride = mismatchedSession,
+            FailEventDetachOnce = true,
+        };
+        var controller = new LiveSessionController(operations);
+
+        LiveSessionStartResult result = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Failed, result.Status);
+        Assert.Contains("different session", result.Error!.ToString());
+        Assert.Equal(0, operations.DisposeCounts.GetValueOrDefault(operations.Sessions[0]));
+        Assert.Equal(1, host.DeactivateCount);
+        Assert.Equal(1, host.EventDetachCount);
+
+        controller.Stop();
+
+        Assert.Equal(1, operations.DisposeCounts[operations.Sessions[0]]);
+        Assert.Equal(1, host.DeactivateCount);
+        Assert.Equal(2, host.EventDetachCount);
+        Assert.Equal(1, host.DetachCount);
+        controller.Dispose();
+    }
+
+    [Theory]
+    [InlineData(ReentrantStopPoint.Reset)]
+    [InlineData(ReentrantStopPoint.Resolve)]
+    [InlineData(ReentrantStopPoint.Create)]
+    [InlineData(ReentrantStopPoint.Bind)]
+    [InlineData(ReentrantStopPoint.Connecting)]
+    [InlineData(ReentrantStopPoint.Connect)]
+    [InlineData(ReentrantStopPoint.Connected)]
+    [InlineData(ReentrantStopPoint.Selected)]
+    [InlineData(ReentrantStopPoint.EnterWorld)]
+    [InlineData(ReentrantStopPoint.Activate)]
+    [InlineData(ReentrantStopPoint.Entered)]
+    public void ReentrantStop_InvalidatesOuterGenerationAndCannotResurrect(
+        ReentrantStopPoint point)
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        Action stop = controller.Stop;
+        switch (point)
+        {
+            case ReentrantStopPoint.Reset: host.OnReset = stop; break;
+            case ReentrantStopPoint.Resolve: operations.OnResolve = stop; break;
+            case ReentrantStopPoint.Create: operations.OnCreate = stop; break;
+            case ReentrantStopPoint.Bind: host.OnBind = stop; break;
+            case ReentrantStopPoint.Connecting: host.OnConnecting = stop; break;
+            case ReentrantStopPoint.Connect: operations.OnConnect = stop; break;
+            case ReentrantStopPoint.Connected: host.OnConnected = stop; break;
+            case ReentrantStopPoint.Selected: host.OnSelected = stop; break;
+            case ReentrantStopPoint.EnterWorld: operations.OnEnterWorld = stop; break;
+            case ReentrantStopPoint.Activate: host.OnActivate = stop; break;
+            case ReentrantStopPoint.Entered: host.OnEntered = stop; break;
+        }
+
+        LiveSessionStartResult result = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Deferred, result.Status);
+        Assert.False(controller.IsInWorld);
+        Assert.Null(controller.CurrentSession);
+        Assert.Same(NullCommandBus.Instance, controller.Commands);
+        if (operations.Sessions.Count == 0)
+        {
+            Assert.Contains(
+                point,
+                new[] { ReentrantStopPoint.Reset, ReentrantStopPoint.Resolve });
+        }
+        else
+        {
+            Assert.Equal(1, operations.DisposeCounts[operations.Sessions[0]]);
+        }
+        Assert.Equal(
+            point is ReentrantStopPoint.Reset
+                or ReentrantStopPoint.Resolve
+                or ReentrantStopPoint.Create
+                ? 0
+                : 1,
+            host.DetachCount);
+    }
+
+    [Fact]
+    public void ReentrantDuplicateStartIsDeferredWithoutDisturbingOuterAttempt()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        LiveSessionStartResult? nested = null;
+        host.OnSelected = () => nested = controller.Start(LiveOptions(), host);
+
+        LiveSessionStartResult outer = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Deferred, nested!.Status);
+        Assert.Equal(LiveSessionStartStatus.Connected, outer.Status);
+        Assert.True(controller.IsInWorld);
+        Assert.Single(operations.Sessions);
+    }
+
+    [Fact]
+    public void ReentrantStartFromFailingEnteredCallbackCannotObserveUncommittedSession()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        LiveSessionStartResult? nested = null;
+        host.OnEntered = () =>
+        {
+            nested = controller.Start(LiveOptions(), host);
+            throw new InvalidOperationException("entered failure");
+        };
+
+        LiveSessionStartResult outer = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Deferred, nested!.Status);
+        Assert.Equal(LiveSessionStartStatus.Failed, outer.Status);
+        Assert.False(controller.IsInWorld);
+        Assert.Null(controller.CurrentSession);
+        controller.Dispose();
+    }
+
+    [Theory]
+    [InlineData("reconnect")]
+    [InlineData("dispose")]
+    public void ReentrantLifecycleRequestDuringActivationDoesNotLeakActiveCommands(
+        string request)
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        bool requested = false;
+        host.OnActivate = () =>
+        {
+            if (requested)
+                return;
+            requested = true;
+            if (request == "reconnect")
+                controller.Reconnect(LiveOptions(), host);
+            else
+                controller.Dispose();
+        };
+
+        LiveSessionStartResult outer = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Deferred, outer.Status);
+        Assert.False(host.CommandBuses[0].Active);
+        Assert.Equal(request == "reconnect" ? 2 : 1, operations.Sessions.Count);
+        Assert.Equal(request == "reconnect", controller.IsInWorld);
+        controller.Dispose();
+    }
+
+    [Theory]
+    [InlineData("connecting")]
+    [InlineData("connected")]
+    [InlineData("characters")]
+    [InlineData("selected")]
+    [InlineData("activate")]
+    [InlineData("entered")]
+    public void Start_CallbackFailureConvergesOffline(string phase)
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        switch (phase)
+        {
+            case "connecting": host.ThrowOnConnecting = true; break;
+            case "connected": host.ThrowOnConnected = true; break;
+            case "characters": operations.ThrowOnCharacters = true; break;
+            case "selected": host.ThrowOnSelected = true; break;
+            case "activate": host.ThrowOnActivate = true; break;
+            case "entered": host.ThrowOnEntered = true; break;
+        }
+        var controller = new LiveSessionController(operations);
+
+        LiveSessionStartResult result = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Failed, result.Status);
+        Assert.Contains($"{phase} failure", result.Error!.ToString());
+        Assert.False(controller.IsInWorld);
+        Assert.Null(controller.CurrentSession);
+        Assert.Equal(1, operations.DisposeCounts[operations.Sessions[0]]);
+        Assert.Same(NullCommandBus.Instance, controller.Commands);
+        controller.Dispose();
+    }
+
+    [Theory]
+    [InlineData("deactivate")]
+    [InlineData("events")]
+    [InlineData("session")]
+    [InlineData("detach")]
+    [InlineData("reset")]
+    public void Stop_RetriesExactFailedTeardownStageWithoutRepeatingCompletedWork(
+        string phase)
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        controller.Start(LiveOptions(), host);
+        WorldSession session = operations.Sessions[0];
+        switch (phase)
+        {
+            case "deactivate": host.FailDeactivateOnce = true; break;
+            case "events": host.FailEventDetachOnce = true; break;
+            case "session": operations.FailDisposeOnce = true; break;
+            case "detach": host.FailDetachOnce = true; break;
+            case "reset": host.FailResetOnce = true; break;
+        }
+
+        Assert.Throws<InvalidOperationException>(controller.Stop);
+        controller.Stop();
+
+        Assert.False(controller.IsInWorld);
+        Assert.Null(controller.CurrentSession);
+        Assert.Equal(1, operations.DisposeCounts[session]);
+        Assert.Equal(phase == "detach" ? 2 : 1, host.DetachCount);
+        Assert.Equal(phase == "reset" ? 3 : 2, host.ResetCount);
+        controller.Dispose();
+    }
+
+    [Fact]
+    public void ReconnectRequestedDuringTickRunsAfterTickAndReplacesExactGeneration()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        controller.Start(LiveOptions(), host);
+        WorldSession sessionA = operations.Sessions[0];
+        bool requested = false;
+        operations.OnTick = () =>
+        {
+            if (requested)
+                return;
+            requested = true;
+            LiveSessionStartResult nested = controller.Reconnect(LiveOptions(), host);
+            Assert.Equal(LiveSessionStartStatus.Deferred, nested.Status);
+        };
+
+        controller.Tick();
+
+        Assert.True(controller.IsInWorld);
+        Assert.Equal(2, operations.Sessions.Count);
+        Assert.Equal(1, operations.DisposeCounts[sessionA]);
+        Assert.Same(operations.Sessions[1], controller.CurrentSession);
+    }
+
+    [Fact]
+    public void ResetFailureBlocksConstructionUntilRetryConverges()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls) { FailResetOnce = true };
+        var controller = new LiveSessionController(operations);
+
+        LiveSessionStartResult first = controller.Start(LiveOptions(), host);
+        LiveSessionStartResult second = controller.Start(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Failed, first.Status);
+        Assert.Equal(LiveSessionStartStatus.Connected, second.Status);
+        Assert.Equal(2, host.ResetCount);
+        Assert.Single(operations.Sessions);
+    }
+
+    [Fact]
+    public void FailedDetachRetainsRetiredScopeAndBlocksBFactoryUntilRetry()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls) { FailDetachOnce = true };
+        var controller = new LiveSessionController(operations);
+        controller.Start(LiveOptions(), host);
+        WorldSession sessionA = operations.Sessions[0];
+
+        LiveSessionStartResult first = controller.Reconnect(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Failed, first.Status);
+        Assert.Single(operations.Sessions);
+        Assert.Equal(1, operations.DisposeCounts[sessionA]);
+        Assert.False(controller.IsInWorld);
+
+        LiveSessionStartResult retry = controller.Reconnect(LiveOptions(), host);
+
+        Assert.Equal(LiveSessionStartStatus.Connected, retry.Status);
+        Assert.Equal(2, operations.Sessions.Count);
+        Assert.Equal(1, operations.DisposeCounts[sessionA]);
+        Assert.Equal(2, host.DetachCount);
+    }
+
+    [Fact]
+    public void TickFailureCleansScopeBeforeRethrowing()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls) { ThrowOnTick = true };
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        controller.Start(LiveOptions(), host);
+        WorldSession session = operations.Sessions[0];
+
+        Assert.Throws<InvalidOperationException>(controller.Tick);
+
+        Assert.False(controller.IsInWorld);
+        Assert.Null(controller.CurrentSession);
+        Assert.Equal(1, operations.DisposeCounts[session]);
+    }
+
+    [Fact]
+    public void DisposeIsIdempotentAndMakesOldCommandsInert()
+    {
+        var calls = new List<string>();
+        var operations = new TestOperations(calls);
+        var host = new TestHost(calls);
+        var controller = new LiveSessionController(operations);
+        controller.Start(LiveOptions(), host);
+        WorldSession session = operations.Sessions[0];
+        TestCommandBus commands = host.CommandBuses[0];
+
+        controller.Dispose();
+        controller.Dispose();
+        commands.Publish(new object());
+
+        Assert.Equal(1, operations.DisposeCounts[session]);
+        Assert.Equal(0, commands.PublishCount);
+        Assert.False(controller.IsInWorld);
+        Assert.Same(NullCommandBus.Instance, controller.Commands);
+        Assert.Throws<ObjectDisposedException>(() => controller.Start(LiveOptions(), host));
+    }
+
+    private static RuntimeOptions LiveOptions(
+        bool live = true,
+        string? user = "user")
+    {
+        var environment = new Dictionary<string, string?>
+        {
+            ["ACDREAM_LIVE"] = live ? "1" : "0",
+            ["ACDREAM_TEST_HOST"] = "127.0.0.1",
+            ["ACDREAM_TEST_PORT"] = "9000",
+            ["ACDREAM_TEST_USER"] = user,
+            ["ACDREAM_TEST_PASS"] = "password",
+        };
+        return RuntimeOptions.Parse(
+            "dat",
+            name => environment.GetValueOrDefault(name));
+    }
+
+    private static CharacterList.Parsed AvailableCharacters() => new(
+        0u,
+        [
+            new CharacterList.Character(0x50000001u, "Grey", 10u),
+            new CharacterList.Character(0x50000002u, "Ready", 0u),
+        ],
+        [new CharacterList.Character(0x50000003u, "Deleted", 0u)],
+        11,
+        "Canonical",
+        true,
+        true);
+}

tests/AcDream.Core.Net.Tests/WorldSessionConstructionTests.cs

@@ -0,0 +1,41 @@
+using System.Net;
+
+namespace AcDream.Core.Net.Tests;
+
+public sealed class WorldSessionConstructionTests
+{
+    [Fact]
+    public void InvalidEndpointIsRejectedBeforeTransportAllocation()
+    {
+        int allocationCount = 0;
+        IWorldSessionTransport Allocate(IPEndPoint _)
+        {
+            allocationCount++;
+            return new TestTransport();
+        }
+
+        Assert.Throws<ArgumentNullException>(
+            () => new WorldSession(null!, Allocate));
+        Assert.Throws<ArgumentOutOfRangeException>(
+            () => new WorldSession(
+                new IPEndPoint(IPAddress.Loopback, ushort.MaxValue),
+                Allocate));
+
+        Assert.Equal(0, allocationCount);
+    }
+
+    private sealed class TestTransport : IWorldSessionTransport
+    {
+        public void Send(ReadOnlySpan<byte> datagram) { }
+
+        public void Send(IPEndPoint remote, ReadOnlySpan<byte> datagram) { }
+
+        public byte[]? Receive(TimeSpan timeout, out IPEndPoint? from)
+        {
+            from = null;
+            return null;
+        }
+
+        public void Dispose() { }
+    }
+}