Keep the original casing of model name for custom endpoint to enable Foundry Local

shell/AIShell.Kernel/Shell.cs

@@ -694,7 +694,12 @@ internal async Task RunREPLAsync()
                     while (ex.InnerException is { })
                     {
                         sb ??= new(message, capacity: message.Length * 3);
-                        sb.Append($"\n   Inner -> {ex.InnerException.Message}");
+                        if (sb[^1] is not '\n')
+                        {
+                            sb.Append('\n');
+                        }
+
+                        sb.Append($"   Inner -> {ex.InnerException.Message}");
                         ex = ex.InnerException;
                     }
 
@@ -703,8 +708,9 @@ internal async Task RunREPLAsync()
                         message = sb.ToString();
                     }
 
+                    string separator = message.EndsWith('\n') ? "\n" : "\n\n";
                     Host.WriteErrorLine()
-                        .WriteErrorLine($"Agent failed to generate a response: {message}\n\n{stackTrace}")
+                        .WriteErrorLine($"Agent failed to generate a response: {message}{separator}{stackTrace}")
                         .WriteErrorLine();
                 }
             }

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

@@ -55,13 +55,16 @@ public GPT(
         Description = description;
         Endpoint = endpoint?.Trim().TrimEnd('/');
         Deployment = deployment;
-        ModelName = modelName.ToLowerInvariant();
         SystemPrompt = systemPrompt;
         Key = key;
         AuthType = authType;
 
         Dirty = false;
-        ModelInfo = ModelInfo.TryResolve(ModelName, out var model) ? model : null;
+        ModelInfo = ModelInfo.TryResolve(modelName, out var model) ? model : null;
+
+        // OpenAI models require the model name to be lower case. e.g., 'gpt-4.1' works but not 'GPT-4.1'.
+        // However, custom endpoint may be case-sensitive on the model name, such as Foundry Local.
+        ModelName = ModelInfo is { } ? modelName.ToLowerInvariant() : modelName;
 
         bool noEndpoint = string.IsNullOrEmpty(Endpoint);
         bool noDeployment = string.IsNullOrEmpty(Deployment);