Multiple fixes and UI improvements based on feedback

shell/AIShell.Abstraction/ILLMAgent.cs

@@ -138,7 +138,7 @@ public interface ILLMAgent : IDisposable
 
     /// <summary>
     /// Refresh the current chat or force starting a new chat session.
-    /// This method allows an agent to reset chat states, interact with user for authentication, print welcome message, and more.
+    /// This method allows an agent to reset chat states, refresh token or settings, interact with user for authentication, print welcome message, and more.
     /// </summary>
     /// <param name="shell">The interface for interacting with the shell.</param>
     /// <param name="force">Whether or not to force creating a new chat session.</param>

shell/AIShell.Kernel/LLMAgent.cs

@@ -13,7 +13,7 @@ internal LLMAgent(ILLMAgent agent, AgentAssemblyLoadContext loadContext)
     {
         Impl = agent;
         LoadContext = loadContext;
-        Prompt = agent.Name;
+        Prompt = $"@{agent.Name}";
     }
 
     internal void Display(Host host, string description = null)

shell/AIShell.Kernel/Shell.cs

@@ -285,7 +285,7 @@ private void LoadAvailableAgents()
             chosenAgent ??= _agents.Count is 1
                 ? _agents[0]
                 : Host.PromptForSelectionAsync(
-                    title: "[orange1]Please select an [Blue]agent[/] to use[/]:",
+                    title: "[orange1]Please select an [Blue]agent[/] to use[/]:\n[grey](You can switch to another agent later by typing [Blue]@<agent name>[/])[/]",
                     choices: _agents,
                     converter: static a => a.Impl.Name)
                 .GetAwaiter().GetResult();
@@ -538,6 +538,18 @@ private async Task<string> ReadUserInput(string prompt, CancellationToken cancel
         return input;
     }
 
+    /// <summary>
+    /// Give an agent the opportunity to refresh its chat session, in the unforced way.
+    /// </summary>
+    private async Task RefreshChatAsNeeded(LLMAgent agent)
+    {
+        if (_shouldRefresh)
+        {
+            _shouldRefresh = false;
+            await agent?.Impl.RefreshChatAsync(this, force: false);
+        }
+    }
+
     /// <summary>
     /// Run a chat REPL.
     /// </summary>
@@ -552,11 +564,7 @@ internal async Task RunREPLAsync()
 
             try
             {
-                if (_shouldRefresh)
-                {
-                    _shouldRefresh = false;
-                    await agent?.Impl.RefreshChatAsync(this, force: false);
-                }
+                await RefreshChatAsNeeded(agent);
 
                 if (Regenerate)
                 {
@@ -595,6 +603,12 @@ internal async Task RunREPLAsync()
                     {
                         continue;
                     }
+                    else
+                    {
+                        // We may be switching to an agent that hasn't setup its chat session yet.
+                        // So, give it a chance to do so before calling its 'Chat' method.
+                        await RefreshChatAsNeeded(agent);
+                    }
                 }
 
                 string copiedText = await GetClipboardContent(input);

shell/agents/AIShell.Interpreter.Agent/Agent.cs

@@ -74,12 +74,15 @@ public void Initialize(AgentConfig config)
     /// <inheritdoc/>
     public Task RefreshChatAsync(IShell shell, bool force)
     {
-        // Reload the setting file if needed.
-        ReloadSettings();
-        // Reset the history so the subsequent chat can start fresh.
-        _chatService.RefreshChat();
-        // Shut down the execution service to start fresh.
-        _executionService.Terminate();
+        if (force)
+        {
+            // Reload the setting file if needed.
+            ReloadSettings();
+            // Reset the history so the subsequent chat can start fresh.
+            _chatService.RefreshChat();
+            // Shut down the execution service to start fresh.
+            _executionService.Terminate();
+        }
 
         return Task.CompletedTask;
     }

shell/agents/AIShell.OpenAI.Agent/Agent.cs

@@ -79,10 +79,13 @@ public void OnUserAction(UserActionPayload actionPayload) {}
     /// <inheritdoc/>
     public Task RefreshChatAsync(IShell shell, bool force)
     {
-        // Reload the setting file if needed.
-        ReloadSettings();
-        // Reset the history so the subsequent chat can start fresh.
-        _chatService.ChatHistory.Clear();
+        if (force)
+        {
+            // Reload the setting file if needed.
+            ReloadSettings();
+            // Reset the history so the subsequent chat can start fresh.
+            _chatService.ChatHistory.Clear();
+        }
 
         return Task.CompletedTask;
     }

shell/agents/Microsoft.Azure.Agent/AzureAgent.cs

@@ -77,7 +77,7 @@ public AzureAgent()
 
     public void Dispose()
     {
-        ArgPlaceholder?.DataRetriever?.Dispose();
+        ResetArgumentPlaceholder();
         _chatSession.Dispose();
         _httpClient.Dispose();
 
@@ -120,6 +120,7 @@ public async Task RefreshChatAsync(IShell shell, bool force)
     {
         IHost host = shell.Host;
         CancellationToken cancellationToken = shell.CancellationToken;
+        ResetArgumentPlaceholder();
 
         try
         {
@@ -179,8 +180,7 @@ public async Task<bool> ChatAsync(string input, IShell shell)
 
             if (_copilotResponse.ChunkReader is null)
             {
-                ArgPlaceholder?.DataRetriever?.Dispose();
-                ArgPlaceholder = null;
+                ResetArgumentPlaceholder();
 
                 // Process CLI handler response specially to support parameter injection.
                 ResponseData data = null;
@@ -360,6 +360,12 @@ private ResponseData ParseCLIHandlerResponse(IShell shell)
         return data;
     }
 
+    internal void ResetArgumentPlaceholder()
+    {
+        ArgPlaceholder?.DataRetriever?.Dispose();
+        ArgPlaceholder = null;
+    }
+
     internal void SaveUserValue(string phName, string value)
     {
         ArgumentException.ThrowIfNullOrEmpty(phName);
@@ -465,7 +471,9 @@ internal string GenerateAnswer(ResponseData data)
                     _buffer.Append($"- `{phItem.Name}`: {phItem.Desc}\n");
                 }
 
-                _buffer.Append("\nRun `/replace` to get assistance in placeholder replacement.\n");
+                // Use green (0,195,0) on grey (48,48,48) for rendering the command '/replace'.
+                // TODO: the color formatting should be exposed by the shell as utility method.
+                _buffer.Append("\nRun \x1b[38;2;0;195;0;48;2;48;48;48m /replace \x1b[0m to get assistance in placeholder replacement.\n");
             }
         }
 

shell/agents/Microsoft.Azure.Agent/ChatSession.cs

@@ -70,15 +70,15 @@ internal async Task<string> RefreshAsync(IStatusContext context, bool force, Can
             if (force)
             {
                 // End the existing conversation.
-                context.Status("End current chat ...");
+                context.Status("Ending current chat ...");
                 EndConversation();
                 Reset();
             }
             else
             {
                 try
                 {
-                    context.Status("Refresh DirectLine token ...");
+                    context.Status("Refreshing token ...");
                     await RenewTokenAsync(cancellationToken);
                     return null;
                 }

shell/agents/Microsoft.Azure.Agent/Command.cs

@@ -238,8 +238,7 @@ private async Task<string> RegenerateAsync()
 
         if (data.PlaceholderSet is null)
         {
-            _agent.ArgPlaceholder.DataRetriever.Dispose();
-            _agent.ArgPlaceholder = null;
+            _agent.ResetArgumentPlaceholder();
         }
 
         return _agent.GenerateAnswer(data);