Fixed several provider dialog issues (#629)

app/MindWork AI Studio/Provider/BaseProvider.cs

@@ -554,10 +554,22 @@ public abstract class BaseProvider : IProvider, ISecretId
         
             await using var fileStream = File.OpenRead(audioFilePath);
             using var fileContent = new StreamContent(fileStream);
+            
+            // Set the content type based on the file extension:
             fileContent.Headers.ContentType = new MediaTypeHeaderValue(mimeType);
-
+            
+            // Add the file content to the form data:
             form.Add(fileContent, "file", Path.GetFileName(audioFilePath));
-            form.Add(new StringContent(transcriptionModel.Id), "model");
+
+            //
+            // Add the model name to the form data. Ensure that a model name is always provided.
+            // Otherwise, the StringContent constructor will throw an exception.
+            //
+            var modelName = transcriptionModel.Id;
+            if (string.IsNullOrWhiteSpace(modelName))
+                modelName = "placeholder";
+            
+            form.Add(new StringContent(modelName), "model");
 
             using var request = new HttpRequestMessage(HttpMethod.Post, host.TranscriptionURL());
             request.Content = form;

app/MindWork AI Studio/Provider/LLMProvidersExtensions.cs

@@ -327,6 +327,32 @@ public static class LLMProvidersExtensions
         _ => false,
     };
 
+    /// <summary>
+    /// Determines if the model selection should be completely hidden for LLM providers.
+    /// This is the case when the host does not support model selection (e.g., llama.cpp).
+    /// </summary>
+    /// <param name="provider">The provider.</param>
+    /// <param name="host">The host for self-hosted providers.</param>
+    /// <returns>True if model selection should be hidden; otherwise, false.</returns>
+    public static bool IsLLMModelSelectionHidden(this LLMProviders provider, Host host) => provider switch
+    {
+        LLMProviders.SELF_HOSTED => host is Host.LLAMA_CPP,
+        _ => false,
+    };
+
+    /// <summary>
+    /// Determines if the model selection should be completely hidden for transcription providers.
+    /// This is the case when the host does not support model selection (e.g., whisper.cpp).
+    /// </summary>
+    /// <param name="provider">The provider.</param>
+    /// <param name="host">The host for self-hosted providers.</param>
+    /// <returns>True if model selection should be hidden; otherwise, false.</returns>
+    public static bool IsTranscriptionModelSelectionHidden(this LLMProviders provider, Host host) => provider switch
+    {
+        LLMProviders.SELF_HOSTED => host is Host.WHISPER_CPP,
+        _ => false,
+    };
+
     public static bool IsHostNeeded(this LLMProviders provider) => provider switch
     {
         LLMProviders.SELF_HOSTED => true,
@@ -391,13 +417,13 @@ public static class LLMProvidersExtensions
             {
                 case Host.NONE:
                 case Host.LLAMA_CPP:
+                case Host.WHISPER_CPP:
                 default:
                     return false;
 
                 case Host.OLLAMA:
                 case Host.LM_STUDIO:
                 case Host.VLLM:
-                case Host.WHISPER_CPP:
                     return true;
             }
         }

app/MindWork AI Studio/Provider/Model.cs

@@ -9,6 +9,22 @@ namespace AIStudio.Provider;
 /// <param name="DisplayName">The model's display name.</param>
 public readonly record struct Model(string Id, string? DisplayName)
 {
+    /// <summary>
+    /// Special model ID used when the model is selected by the system/host
+    /// and cannot be changed by the user (e.g., llama.cpp, whisper.cpp).
+    /// </summary>
+    private const string SYSTEM_MODEL_ID = "::system::";
+
+    /// <summary>
+    /// Creates a system-configured model placeholder.
+    /// </summary>
+    public static readonly Model SYSTEM_MODEL = new(SYSTEM_MODEL_ID, null);
+
+    /// <summary>
+    /// Checks if this model is the system-configured placeholder.
+    /// </summary>
+    public bool IsSystemModel => this == SYSTEM_MODEL;
+
     private static string TB(string fallbackEN) => I18N.I.T(fallbackEN, typeof(Model).Namespace, nameof(Model));
     
     #region Overrides of ValueType

app/MindWork AI Studio/Provider/SelfHosted/ProviderSelfHosted.cs

@@ -149,31 +149,30 @@ public sealed class ProviderSelfHosted(Host host, string hostname) : BaseProvide
     }
     
     /// <inheritdoc />
-    public override Task<IEnumerable<Provider.Model>> GetTranscriptionModels(string? apiKeyProvisional = null, CancellationToken token = default)
+    public override async Task<IEnumerable<Provider.Model>> GetTranscriptionModels(string? apiKeyProvisional = null, CancellationToken token = default)
     {
         try
         {
             switch (host)
             {
                 case Host.WHISPER_CPP:
-                    return Task.FromResult<IEnumerable<Provider.Model>>(
-                        new List<Provider.Model>
-                        {
-                            new("loaded-model", TB("Model as configured by whisper.cpp")),
-                        });
+                    return new List<Provider.Model>
+                    {
+                        new("loaded-model", TB("Model as configured by whisper.cpp")),
+                    };
                 
                 case Host.OLLAMA:
                 case Host.VLLM:
-                    return this.LoadModels(SecretStoreType.TRANSCRIPTION_PROVIDER, [], [], token, apiKeyProvisional);
+                    return await this.LoadModels(SecretStoreType.TRANSCRIPTION_PROVIDER, [], [], token, apiKeyProvisional);
                 
                 default:
-                    return Task.FromResult(Enumerable.Empty<Provider.Model>());
+                    return [];
             }
         }
         catch (Exception e)
         {
-            LOGGER.LogError(e, "Failed to load transcription models from self-hosted provider.");
-            return Task.FromResult(Enumerable.Empty<Provider.Model>());
+            LOGGER.LogError($"Failed to load transcription models from self-hosted provider: {e.Message}");
+            return [];
         }
     }