.NET: Add ability to export/import sessions in harness console (#5920)

* Add ability to export/import sessions in harness console

* Address PR comments

dotnet/samples/02-agents/Harness/Harness_Shared_Console/Commands/SessionCommandHandler.cs

@@ -0,0 +1,98 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Text.Json;
+using Microsoft.Agents.AI;
+
+namespace Harness.Shared.Console.Commands;
+
+/// <summary>
+/// Handles <c>/session-export &lt;filename&gt;</c> and <c>/session-import &lt;filename&gt;</c>
+/// commands for serializing the current session to a file and restoring a session from a file.
+/// </summary>
+public sealed class SessionCommandHandler : CommandHandler
+{
+    private readonly AIAgent _agent;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SessionCommandHandler"/> class.
+    /// </summary>
+    /// <param name="agent">The agent used for session serialization and deserialization.</param>
+    public SessionCommandHandler(AIAgent agent)
+    {
+        this._agent = agent;
+    }
+
+    /// <inheritdoc/>
+    public override string? GetHelpText() => "/session-export <file> | /session-import <file>";
+
+    /// <inheritdoc/>
+    public override async ValueTask<bool> TryHandleAsync(string input, AgentSession session, IUXStateDriver ux)
+    {
+        string command = input.Split(' ', 2)[0];
+
+        if (command.Equals("/session-export", StringComparison.OrdinalIgnoreCase))
+        {
+            await this.HandleExportAsync(input, session, ux).ConfigureAwait(false);
+            return true;
+        }
+
+        if (command.Equals("/session-import", StringComparison.OrdinalIgnoreCase))
+        {
+            await this.HandleImportAsync(input, ux).ConfigureAwait(false);
+            return true;
+        }
+
+        return false;
+    }
+
+    private async Task HandleExportAsync(string input, AgentSession session, IUXStateDriver ux)
+    {
+        string[] parts = input.Split(' ', 2, StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
+        if (parts.Length < 2)
+        {
+            await ux.WriteInfoLineAsync("Usage: /session-export <filename>").ConfigureAwait(false);
+            return;
+        }
+
+        string filename = parts[1];
+        try
+        {
+            JsonElement serialized = await this._agent.SerializeSessionAsync(session).ConfigureAwait(false);
+            string json = JsonSerializer.Serialize(serialized);
+            await File.WriteAllTextAsync(filename, json).ConfigureAwait(false);
+            await ux.WriteInfoLineAsync($"Session exported to {filename}").ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            await ux.WriteInfoLineAsync($"Failed to export session to {filename}: {ex.Message}").ConfigureAwait(false);
+        }
+    }
+
+    private async Task HandleImportAsync(string input, IUXStateDriver ux)
+    {
+        string[] parts = input.Split(' ', 2, StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
+        if (parts.Length < 2)
+        {
+            await ux.WriteInfoLineAsync("Usage: /session-import <filename>").ConfigureAwait(false);
+            return;
+        }
+
+        string filename = parts[1];
+        try
+        {
+            string json = await File.ReadAllTextAsync(filename).ConfigureAwait(false);
+            JsonElement element = JsonSerializer.Deserialize<JsonElement>(json);
+            AgentSession newSession = await this._agent.DeserializeSessionAsync(element).ConfigureAwait(false);
+            await ux.ReplaceSessionAsync(newSession).ConfigureAwait(false);
+            await ux.WriteInfoLineAsync($"Session imported from {filename}").ConfigureAwait(false);
+        }
+        catch (FileNotFoundException)
+        {
+            await ux.WriteInfoLineAsync($"File not found: {filename}").ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            await ux.WriteInfoLineAsync($"Failed to import session from {filename}: {ex.Message}").ConfigureAwait(false);
+        }
+    }
+}

dotnet/samples/02-agents/Harness/Harness_Shared_Console/HarnessAgentRunner.cs

@@ -19,15 +19,15 @@ namespace Harness.Shared.Console;
 public sealed class HarnessAgentRunner : IDisposable
 {
     private readonly AIAgent _agent;
-    private readonly AgentSession _session;
     private readonly AgentModeProvider? _modeProvider;
     private readonly MessageInjectingChatClient? _messageInjector;
     private readonly IReadOnlyList<CommandHandler> _commandHandlers;
     private readonly IReadOnlyList<ConsoleObserver> _observers;
     private readonly IUXStateDriver _ux;
-
     private readonly SemaphoreSlim _inputGate = new(1, 1);
 
+    private AgentSession _session;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="HarnessAgentRunner"/> class.
     /// </summary>
@@ -62,6 +62,25 @@ public sealed class HarnessAgentRunner : IDisposable
     /// </summary>
     public string HelpText { get; }
 
+    /// <summary>
+    /// Replaces the current session with the specified session. Used by the UX driver
+    /// when importing a serialized session. Acquires the input gate to ensure no
+    /// concurrent agent turn is reading the session.
+    /// </summary>
+    /// <param name="newSession">The new session to use.</param>
+    internal async Task ReplaceSessionAsync(AgentSession newSession)
+    {
+        await this._inputGate.WaitAsync().ConfigureAwait(false);
+        try
+        {
+            this._session = newSession;
+        }
+        finally
+        {
+            this._inputGate.Release();
+        }
+    }
+
     /// <inheritdoc/>
     public void Dispose() => this._inputGate.Dispose();
 

dotnet/samples/02-agents/Harness/Harness_Shared_Console/HarnessAppComponent.cs

@@ -63,6 +63,7 @@ public class HarnessAppComponent : ConsoleReactiveComponent<ConsoleReactiveProps
             getState: () => this.State!,
             setState: s => this.SetState(s),
             requestShutdown: () => this._shutdownTcs.TrySetResult(true),
+            replaceSession: s => this.Runner!.ReplaceSessionAsync(s),
             modeColors: modeColors);
 
         this.Runner = runnerFactory(this._uxDriver);

dotnet/samples/02-agents/Harness/Harness_Shared_Console/HarnessConsoleOptions.cs

@@ -128,6 +128,7 @@ public class HarnessConsoleOptions
             new ExitCommandHandler(),
             new TodoCommandHandler(todoProvider),
             new ModeCommandHandler(modeProvider, modeColors ?? DefaultModeColors),
+            new SessionCommandHandler(agent),
         ];
     }
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/HarnessConsoleUXStateDriver.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using Harness.ConsoleReactiveComponents;
+using Microsoft.Agents.AI;
 using Microsoft.Extensions.AI;
 
 namespace Harness.Shared.Console;
@@ -16,6 +17,7 @@ internal sealed class HarnessConsoleUXStateDriver : IUXStateDriver
     private readonly Func<HarnessAppComponentState> _getState;
     private readonly Action<HarnessAppComponentState> _setState;
     private readonly Action _requestShutdown;
+    private readonly Func<AgentSession, Task> _replaceSession;
     private readonly IReadOnlyDictionary<string, ConsoleColor>? _modeColors;
     private readonly List<string> _outputItems = [];
     private readonly object _stateLock = new();
@@ -32,16 +34,19 @@ internal sealed class HarnessConsoleUXStateDriver : IUXStateDriver
     /// <param name="getState">Returns the component's current state.</param>
     /// <param name="setState">Replaces the component's state and triggers a re-render.</param>
     /// <param name="requestShutdown">Callback invoked when a command handler requests application shutdown.</param>
+    /// <param name="replaceSession">Callback invoked to replace the current agent session (e.g., on import).</param>
     /// <param name="modeColors">Optional mapping of mode names to console colors.</param>
     public HarnessConsoleUXStateDriver(
         Func<HarnessAppComponentState> getState,
         Action<HarnessAppComponentState> setState,
         Action requestShutdown,
+        Func<AgentSession, Task> replaceSession,
         IReadOnlyDictionary<string, ConsoleColor>? modeColors = null)
     {
         this._getState = getState;
         this._setState = setState;
         this._requestShutdown = requestShutdown;
+        this._replaceSession = replaceSession;
         this._modeColors = modeColors;
         this._currentMode = getState().ModeText;
     }
@@ -405,4 +410,7 @@ internal sealed class HarnessConsoleUXStateDriver : IUXStateDriver
 
     /// <inheritdoc/>
     public void RequestShutdown() => this._requestShutdown();
+
+    /// <inheritdoc/>
+    public Task ReplaceSessionAsync(AgentSession newSession) => this._replaceSession(newSession);
 }

dotnet/samples/02-agents/Harness/Harness_Shared_Console/IUXStateDriver.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using Microsoft.Agents.AI;
 using Microsoft.Extensions.AI;
 
 namespace Harness.Shared.Console;
@@ -117,4 +118,11 @@ public interface IUXStateDriver
     /// on the owning component.
     /// </summary>
     void RequestShutdown();
+
+    /// <summary>
+    /// Replaces the current agent session with the specified session (e.g., after importing
+    /// a serialized session from a file).
+    /// </summary>
+    /// <param name="newSession">The new session to use.</param>
+    Task ReplaceSessionAsync(AgentSession newSession);
 }