Added support for images (#609)

app/MindWork AI Studio/Provider/AlibabaCloud/ProviderAlibabaCloud.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.AlibabaCloud;
 
-public sealed class ProviderAlibabaCloud() : BaseProvider("https://dashscope-intl.aliyuncs.com/compatible-mode/v1/", LOGGER)
+public sealed class ProviderAlibabaCloud() : BaseProvider(LLMProviders.ALIBABA_CLOUD, "https://dashscope-intl.aliyuncs.com/compatible-mode/v1/", LOGGER)
 {
     private static readonly ILogger<ProviderAlibabaCloud> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderAlibabaCloud>();
 
@@ -40,24 +40,7 @@ public sealed class ProviderAlibabaCloud() : BaseProvider("https://dashscope-int
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the AlibabaCloud HTTP chat request:
         var alibabaCloudChatRequest = JsonSerializer.Serialize(new ChatCompletionAPIRequest

app/MindWork AI Studio/Provider/Anthropic/ISubContentImageSource.cs

@@ -0,0 +1,9 @@
+namespace AIStudio.Provider.Anthropic;
+
+public interface ISubContentImageSource
+{
+    /// <summary>
+    /// The type of the sub-content image.
+    /// </summary>
+    public SubContentImageType Type { get; }
+}

app/MindWork AI Studio/Provider/Anthropic/ProviderAnthropic.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.Anthropic;
 
-public sealed class ProviderAnthropic() : BaseProvider("https://api.anthropic.com/v1/", LOGGER)
+public sealed class ProviderAnthropic() : BaseProvider(LLMProviders.ANTHROPIC, "https://api.anthropic.com/v1/", LOGGER)
 {
     private static readonly ILogger<ProviderAnthropic> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderAnthropic>();
 
@@ -31,9 +31,11 @@ public sealed class ProviderAnthropic() : BaseProvider("https://api.anthropic.co
         var apiParameters = this.ParseAdditionalApiParameters("system");
 
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
+        var messages = await chatThread.Blocks.BuildMessagesAsync(
+            this.Provider, chatModel,
+            
+            // Anthropic-specific role mapping:
+            role => role switch
             {
                 ChatRole.USER => "user",
                 ChatRole.AI => "assistant",
@@ -41,13 +43,26 @@ public sealed class ProviderAnthropic() : BaseProvider("https://api.anthropic.co
 
                 _ => "user",
             },
-
-            Content = n.Content switch
+            
+            // Anthropic uses the standard text sub-content:
+            text => new SubContentText
             {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
+                Text = text,
+            },
+            
+            // Anthropic-specific image sub-content:
+            async attachment => new SubContentImage
+            {
+                Source = new SubContentBase64Image
+                {
+                    Data = await attachment.TryAsBase64(token: token) is (true, var base64Content)
+                        ? base64Content
+                        : string.Empty,
+                    
+                    MediaType = attachment.DetermineMimeType(),
+                }
             }
-        });
+        );
         
         // Prepare the Anthropic HTTP chat request:
         var chatRequest = JsonSerializer.Serialize(new ChatRequest

app/MindWork AI Studio/Provider/Anthropic/SubContentBase64Image.cs

@@ -0,0 +1,10 @@
+namespace AIStudio.Provider.Anthropic;
+
+public record SubContentBase64Image : ISubContentImageSource
+{
+    public SubContentImageType Type => SubContentImageType.BASE64;
+
+    public string MediaType { get; init; } = string.Empty;
+    
+    public string Data { get; init; } = string.Empty;
+}

app/MindWork AI Studio/Provider/Anthropic/SubContentImage.cs

@@ -0,0 +1,10 @@
+using AIStudio.Provider.OpenAI;
+
+namespace AIStudio.Provider.Anthropic;
+
+public record SubContentImage(SubContentType Type, ISubContentImageSource Source) : ISubContent
+{
+    public SubContentImage() : this(SubContentType.IMAGE, new SubContentImageUrl())
+    {
+    }
+}

app/MindWork AI Studio/Provider/Anthropic/SubContentImageSourceConverter.cs

@@ -0,0 +1,32 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace AIStudio.Provider.Anthropic;
+
+/// <summary>
+/// Custom JSON converter for the ISubContentImageSource interface to handle polymorphic serialization.
+/// </summary>
+/// <remarks>
+/// This converter ensures that when serializing ISubContentImageSource objects, all properties
+/// of the concrete implementation (e.g., SubContentBase64Image, SubContentImageUrl) are serialized,
+/// not just the properties defined in the ISubContentImageSource interface.
+/// </remarks>
+public sealed class SubContentImageSourceConverter : JsonConverter<ISubContentImageSource>
+{
+    private static readonly ILogger<SubContentImageSourceConverter> LOGGER = Program.LOGGER_FACTORY.CreateLogger<SubContentImageSourceConverter>();
+
+    public override ISubContentImageSource? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        // Deserialization is not needed for request objects, as sub-content image sources are only serialized
+        // when sending requests to LLM providers.
+        LOGGER.LogError("Deserializing ISubContentImageSource is not supported. This converter is only used for serializing request messages.");
+        return null;
+    }
+
+    public override void Write(Utf8JsonWriter writer, ISubContentImageSource value, JsonSerializerOptions options)
+    {
+        // Serialize the actual concrete type (e.g., SubContentBase64Image, SubContentImageUrl) instead of just the ISubContentImageSource interface.
+        // This ensures all properties of the concrete type are included in the JSON output.
+        JsonSerializer.Serialize(writer, value, value.GetType(), options);
+    }
+}

app/MindWork AI Studio/Provider/Anthropic/SubContentImageType.cs

@@ -0,0 +1,7 @@
+namespace AIStudio.Provider.Anthropic;
+
+public enum SubContentImageType
+{
+    URL,
+    BASE64
+}

app/MindWork AI Studio/Provider/Anthropic/SubContentImageUrl.cs

@@ -0,0 +1,8 @@
+namespace AIStudio.Provider.Anthropic;
+
+public record SubContentImageUrl : ISubContentImageSource
+{
+    public SubContentImageType Type => SubContentImageType.URL;
+
+    public string Url { get; init; } = string.Empty;
+}

app/MindWork AI Studio/Provider/BaseProvider.cs

@@ -1,8 +1,10 @@
 using System.Net;
 using System.Runtime.CompilerServices;
 using System.Text.Json;
+using System.Text.Json.Serialization;
 
 using AIStudio.Chat;
+using AIStudio.Provider.Anthropic;
 using AIStudio.Provider.OpenAI;
 using AIStudio.Settings;
 using AIStudio.Tools.PluginSystem;
@@ -40,18 +42,28 @@ public abstract class BaseProvider : IProvider, ISecretId
     protected static readonly JsonSerializerOptions JSON_SERIALIZER_OPTIONS = new()
     {
         PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
-        Converters = { new AnnotationConverter(), new MessageBaseConverter() },
+        Converters =
+        {
+            new JsonStringEnumConverter(JsonNamingPolicy.SnakeCaseLower),
+            new AnnotationConverter(),
+            new MessageBaseConverter(),
+            new SubContentConverter(),
+            new SubContentImageSourceConverter(),
+            new SubContentImageUrlConverter(),
+        },
         AllowTrailingCommas = false
     };
 
     /// <summary>
     /// Constructor for the base provider.
     /// </summary>
+    /// <param name="provider">The provider enum value.</param>
     /// <param name="url">The base URL for the provider.</param>
     /// <param name="logger">The logger to use.</param>
-    protected BaseProvider(string url, ILogger logger)
+    protected BaseProvider(LLMProviders provider, string url, ILogger logger)
     {
         this.logger = logger;
+        this.Provider = provider;
 
         // Set the base URL:
         this.httpClient.BaseAddress = new(url);
@@ -59,6 +71,9 @@ public abstract class BaseProvider : IProvider, ISecretId
     
     #region Handling of IProvider, which all providers must implement
     
+    /// <inheritdoc />
+    public LLMProviders Provider { get; }
+    
     /// <inheritdoc />
     public abstract string Id { get; }
     

app/MindWork AI Studio/Provider/DeepSeek/ProviderDeepSeek.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.DeepSeek;
 
-public sealed class ProviderDeepSeek() : BaseProvider("https://api.deepseek.com/", LOGGER)
+public sealed class ProviderDeepSeek() : BaseProvider(LLMProviders.DEEP_SEEK, "https://api.deepseek.com/", LOGGER)
 {
     private static readonly ILogger<ProviderDeepSeek> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderDeepSeek>();
 
@@ -40,24 +40,7 @@ public sealed class ProviderDeepSeek() : BaseProvider("https://api.deepseek.com/
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingDirectImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the DeepSeek HTTP chat request:
         var deepSeekChatRequest = JsonSerializer.Serialize(new ChatCompletionAPIRequest

app/MindWork AI Studio/Provider/Fireworks/ProviderFireworks.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.Fireworks;
 
-public class ProviderFireworks() : BaseProvider("https://api.fireworks.ai/inference/v1/", LOGGER)
+public class ProviderFireworks() : BaseProvider(LLMProviders.FIREWORKS, "https://api.fireworks.ai/inference/v1/", LOGGER)
 {
     private static readonly ILogger<ProviderFireworks> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderFireworks>();
 
@@ -40,24 +40,7 @@ public class ProviderFireworks() : BaseProvider("https://api.fireworks.ai/infere
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the Fireworks HTTP chat request:
         var fireworksChatRequest = JsonSerializer.Serialize(new ChatRequest

app/MindWork AI Studio/Provider/Fireworks/TextMessage.cs

@@ -1,13 +0,0 @@
-namespace AIStudio.Provider.Fireworks;
-
-/// <summary>
-/// Chat message model.
-/// </summary>
-/// <param name="Content">The text content of the message.</param>
-/// <param name="Role">The role of the message.</param>
-public record TextMessage(string Content, string Role) : IMessage<string>
-{
-    public TextMessage() : this(string.Empty, string.Empty)
-    {
-    }
-}

app/MindWork AI Studio/Provider/GWDG/ProviderGWDG.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.GWDG;
 
-public sealed class ProviderGWDG() : BaseProvider("https://chat-ai.academiccloud.de/v1/", LOGGER)
+public sealed class ProviderGWDG() : BaseProvider(LLMProviders.GWDG, "https://chat-ai.academiccloud.de/v1/", LOGGER)
 {
     private static readonly ILogger<ProviderGWDG> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderGWDG>();
 
@@ -40,24 +40,7 @@ public sealed class ProviderGWDG() : BaseProvider("https://chat-ai.academiccloud
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the GWDG HTTP chat request:
         var gwdgChatRequest = JsonSerializer.Serialize(new ChatCompletionAPIRequest

app/MindWork AI Studio/Provider/Google/ProviderGoogle.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.Google;
 
-public class ProviderGoogle() : BaseProvider("https://generativelanguage.googleapis.com/v1beta/", LOGGER)
+public class ProviderGoogle() : BaseProvider(LLMProviders.GOOGLE, "https://generativelanguage.googleapis.com/v1beta/", LOGGER)
 {
     private static readonly ILogger<ProviderGoogle> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderGoogle>();
 
@@ -40,24 +40,7 @@ public class ProviderGoogle() : BaseProvider("https://generativelanguage.googlea
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the Google HTTP chat request:
         var geminiChatRequest = JsonSerializer.Serialize(new ChatRequest

app/MindWork AI Studio/Provider/Groq/ProviderGroq.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.Groq;
 
-public class ProviderGroq() : BaseProvider("https://api.groq.com/openai/v1/", LOGGER)
+public class ProviderGroq() : BaseProvider(LLMProviders.GROQ, "https://api.groq.com/openai/v1/", LOGGER)
 {
     private static readonly ILogger<ProviderGroq> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderGroq>();
 
@@ -40,24 +40,7 @@ public class ProviderGroq() : BaseProvider("https://api.groq.com/openai/v1/", LO
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the OpenAI HTTP chat request:
         var groqChatRequest = JsonSerializer.Serialize(new ChatRequest

app/MindWork AI Studio/Provider/Helmholtz/ProviderHelmholtz.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.Helmholtz;
 
-public sealed class ProviderHelmholtz() : BaseProvider("https://api.helmholtz-blablador.fz-juelich.de/v1/", LOGGER)
+public sealed class ProviderHelmholtz() : BaseProvider(LLMProviders.HELMHOLTZ, "https://api.helmholtz-blablador.fz-juelich.de/v1/", LOGGER)
 {
     private static readonly ILogger<ProviderHelmholtz> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderHelmholtz>();
 
@@ -40,24 +40,7 @@ public sealed class ProviderHelmholtz() : BaseProvider("https://api.helmholtz-bl
         var apiParameters = this.ParseAdditionalApiParameters();
             
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the Helmholtz HTTP chat request:
         var helmholtzChatRequest = JsonSerializer.Serialize(new ChatCompletionAPIRequest

app/MindWork AI Studio/Provider/HuggingFace/ProviderHuggingFace.cs

@@ -13,9 +13,9 @@ public sealed class ProviderHuggingFace : BaseProvider
 {
     private static readonly ILogger<ProviderHuggingFace> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderHuggingFace>();
 
-    public ProviderHuggingFace(HFInferenceProvider hfProvider, Model model) : base($"https://router.huggingface.co/{hfProvider.Endpoints(model)}", LOGGER)
+    public ProviderHuggingFace(HFInferenceProvider hfProvider, Model model) : base(LLMProviders.HUGGINGFACE, $"https://router.huggingface.co/{hfProvider.Endpoints(model)}", LOGGER)
     {
-        LOGGER.LogInformation($"We use the inferende provider '{hfProvider}'. Thus we use the base URL 'https://router.huggingface.co/{hfProvider.Endpoints(model)}'.");
+        LOGGER.LogInformation($"We use the inference provider '{hfProvider}'. Thus we use the base URL 'https://router.huggingface.co/{hfProvider.Endpoints(model)}'.");
     }
 
     #region Implementation of IProvider
@@ -45,24 +45,7 @@ public sealed class ProviderHuggingFace : BaseProvider
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var message = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var message = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the HuggingFace HTTP chat request:
         var huggingfaceChatRequest = JsonSerializer.Serialize(new ChatCompletionAPIRequest

app/MindWork AI Studio/Provider/IProvider.cs

@@ -8,6 +8,11 @@ namespace AIStudio.Provider;
 /// </summary>
 public interface IProvider
 {
+    /// <summary>
+    /// The provider type.
+    /// </summary>
+    public LLMProviders Provider { get; }
+    
     /// <summary>
     /// The provider's ID.
     /// </summary>

app/MindWork AI Studio/Provider/Mistral/ProviderMistral.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.Mistral;
 
-public sealed class ProviderMistral() : BaseProvider("https://api.mistral.ai/v1/", LOGGER)
+public sealed class ProviderMistral() : BaseProvider(LLMProviders.MISTRAL, "https://api.mistral.ai/v1/", LOGGER)
 {
     private static readonly ILogger<ProviderMistral> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderMistral>();
 
@@ -38,24 +38,7 @@ public sealed class ProviderMistral() : BaseProvider("https://api.mistral.ai/v1/
         var apiParameters = this.ParseAdditionalApiParameters();
 
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingDirectImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the Mistral HTTP chat request:
         var mistralChatRequest = JsonSerializer.Serialize(new ChatRequest

app/MindWork AI Studio/Provider/Mistral/TextMessage.cs

@@ -1,13 +0,0 @@
-namespace AIStudio.Provider.Mistral;
-
-/// <summary>
-/// Text chat message model.
-/// </summary>
-/// <param name="Content">The text content of the message.</param>
-/// <param name="Role">The role of the message.</param>
-public record TextMessage(string Content, string Role) : IMessage<string>
-{
-    public TextMessage() : this(string.Empty, string.Empty)
-    {
-    }
-}

app/MindWork AI Studio/Provider/NoProvider.cs

@@ -9,6 +9,8 @@ public class NoProvider : IProvider
 {
     #region Implementation of IProvider
 
+    public LLMProviders Provider => LLMProviders.NONE;
+    
     public string Id => "none";
 
     public string InstanceName { get; set; } = "None";

app/MindWork AI Studio/Provider/OpenAI/ISubContent.cs

@@ -0,0 +1,12 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Contract for sub-content in multimodal messages.
+/// </summary>
+public interface ISubContent
+{
+    /// <summary>
+    /// The type of the sub-content.
+    /// </summary>
+    public SubContentType Type { get; init; }
+}

app/MindWork AI Studio/Provider/OpenAI/ISubContentImageUrl.cs

@@ -0,0 +1,19 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Contract for nested image URL sub-content.
+/// </summary>
+/// <remarks>
+/// Some providers use a nested object format for image URLs:
+/// <code>
+/// { "type": "image_url", "image_url": { "url": "data:image/jpeg;base64,..." } }
+/// </code>
+/// This interface represents the inner object with the "url" property.
+/// </remarks>
+public interface ISubContentImageUrl 
+{
+    /// <summary>
+    /// The URL or base64-encoded data URI of the image.
+    /// </summary>
+    public string Url { get; init; }
+}

app/MindWork AI Studio/Provider/OpenAI/MultimodalMessage.cs

@@ -0,0 +1,13 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// A multimodal chat message model that can contain various types of content.
+/// </summary>
+/// <param name="Content">The list of sub-contents in the message.</param>
+/// <param name="Role">The role of the message.</param>
+public record MultimodalMessage(List<ISubContent> Content, string Role) : IMessage<List<ISubContent>>
+{
+    public MultimodalMessage() : this([], string.Empty)
+    {
+    }
+}

app/MindWork AI Studio/Provider/OpenAI/ProviderOpenAI.cs

@@ -11,7 +11,7 @@ namespace AIStudio.Provider.OpenAI;
 /// <summary>
 /// The OpenAI provider.
 /// </summary>
-public sealed class ProviderOpenAI() : BaseProvider("https://api.openai.com/v1/", LOGGER)
+public sealed class ProviderOpenAI() : BaseProvider(LLMProviders.OPEN_AI, "https://api.openai.com/v1/", LOGGER)
 {
     private static readonly ILogger<ProviderOpenAI> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderOpenAI>();
     
@@ -59,7 +59,7 @@ public sealed class ProviderOpenAI() : BaseProvider("https://api.openai.com/v1/"
         };
 
         // Read the model capabilities:
-        var modelCapabilities = ProviderExtensions.GetModelCapabilitiesOpenAI(chatModel);
+        var modelCapabilities = this.Provider.GetModelCapabilities(chatModel);
         
         // Check if we are using the Responses API or the Chat Completion API:
         var usingResponsesAPI = modelCapabilities.Contains(Capability.RESPONSES_API);
@@ -90,9 +90,11 @@ public sealed class ProviderOpenAI() : BaseProvider("https://api.openai.com/v1/"
         var apiParameters = this.ParseAdditionalApiParameters("input", "store", "tools");
 
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
+        var messages = await chatThread.Blocks.BuildMessagesAsync(
+            this.Provider, chatModel,
+
+            // OpenAI-specific role mapping:
+            role => role switch
             {
                 ChatRole.USER => "user",
                 ChatRole.AI => "assistant",
@@ -102,12 +104,46 @@ public sealed class ProviderOpenAI() : BaseProvider("https://api.openai.com/v1/"
                 _ => "user",
             },
 
-            Content = n.Content switch
+            // OpenAI's text sub-content depends on the model, whether we are using
+            // the Responses API or the Chat Completion API:
+            text => usingResponsesAPI switch
             {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+                // Responses API uses INPUT_TEXT:
+                true => new SubContentInputText
+                {
+                    Text = text,
+                },
+
+                // Chat Completion API uses TEXT:
+                false => new SubContentText
+                {
+                    Text = text,
+                },
+            },
+
+            // OpenAI's image sub-content depends on the model as well,
+            // whether we are using the Responses API or the Chat Completion API:
+            async attachment => usingResponsesAPI switch
+            {
+                // Responses API uses INPUT_IMAGE:
+                true => new SubContentInputImage
+                {
+                    ImageUrl = await attachment.TryAsBase64(token: token) is (true, var base64Content)
+                        ? $"data:{attachment.DetermineMimeType()};base64,{base64Content}"
+                        : string.Empty,
+                },
+                
+                // Chat Completion API uses IMAGE_URL:
+                false => new SubContentImageUrlNested
+                {
+                    ImageUrl = new SubContentImageUrlData
+                    {
+                        Url = await attachment.TryAsBase64(token: token) is (true, var base64Content)
+                            ? $"data:{attachment.DetermineMimeType()};base64,{base64Content}"
+                            : string.Empty,
+                    },
+                }
+            });
         
         //
         // Create the request: either for the Responses API or the Chat Completion API
@@ -149,7 +185,7 @@ public sealed class ProviderOpenAI() : BaseProvider("https://api.openai.com/v1/"
                 
             }, JSON_SERIALIZER_OPTIONS),
         };
-
+        
         async Task<HttpRequestMessage> RequestBuilder()
         {
             // Build the HTTP post request:

app/MindWork AI Studio/Provider/OpenAI/SubContentImageUrl.cs

@@ -0,0 +1,11 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Image sub-content for multimodal messages.
+/// </summary>
+public record SubContentImageUrl(SubContentType Type, string ImageUrl) : ISubContent
+{
+    public SubContentImageUrl() : this(SubContentType.IMAGE_URL, string.Empty)
+    {
+    }
+}

app/MindWork AI Studio/Provider/OpenAI/SubContentImageUrlData.cs

@@ -0,0 +1,17 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Represents the inner object of a nested image URL sub-content.
+/// </summary>
+/// <remarks>
+/// This record is used when the provider expects the format:
+/// <code>
+/// { "type": "image_url", "image_url": { "url": "data:image/jpeg;base64,..." } }
+/// </code>
+/// This class represents the inner <c>{ "url": "..." }</c> part.
+/// </remarks>
+public record SubContentImageUrlData : ISubContentImageUrl
+{
+    /// <inheritdoc />
+    public string Url { get; init; } = string.Empty;
+}

app/MindWork AI Studio/Provider/OpenAI/SubContentImageUrlNested.cs

@@ -0,0 +1,18 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Image sub-content for multimodal messages using nested URL format.
+/// </summary>
+/// <remarks>
+/// This record is used when the provider expects the format:
+/// <code>
+/// { "type": "image_url", "image_url": { "url": "data:image/jpeg;base64,..." } }
+/// </code>
+/// Used by LM Studio, VLLM, and other OpenAI-compatible providers.
+/// </remarks>
+public record SubContentImageUrlNested(SubContentType Type, ISubContentImageUrl ImageUrl) : ISubContent
+{
+    public SubContentImageUrlNested() : this(SubContentType.IMAGE_URL, new SubContentImageUrlData())
+    {
+    }
+}

app/MindWork AI Studio/Provider/OpenAI/SubContentInputImage.cs

@@ -0,0 +1,14 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Image input sub-content for multimodal messages.
+/// </summary>
+/// <remarks>
+/// Right now, this is used only by OpenAI in its responses API.
+/// </remarks>
+public record SubContentInputImage(SubContentType Type, string ImageUrl) : ISubContent
+{
+    public SubContentInputImage() : this(SubContentType.INPUT_IMAGE, string.Empty)
+    {
+    }
+}

app/MindWork AI Studio/Provider/OpenAI/SubContentInputText.cs

@@ -0,0 +1,14 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Text input sub-content for multimodal messages.
+/// </summary>
+/// <remarks>
+/// Right now, this is used only by OpenAI in its responses API.
+/// </remarks>
+public record SubContentInputText(SubContentType Type, string Text) : ISubContent
+{
+    public SubContentInputText() : this(SubContentType.INPUT_TEXT, string.Empty)
+    {
+    }
+}

app/MindWork AI Studio/Provider/OpenAI/SubContentText.cs

@@ -0,0 +1,11 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Text sub-content for multimodal messages.
+/// </summary>
+public record SubContentText(SubContentType Type, string Text) : ISubContent
+{
+    public SubContentText() : this(SubContentType.TEXT, string.Empty)
+    {
+    }
+}

app/MindWork AI Studio/Provider/OpenAI/TextMessage.cs

@@ -1,7 +1,7 @@
 namespace AIStudio.Provider.OpenAI;
 
 /// <summary>
-/// Chat message model.
+/// Standard text-based chat message model.
 /// </summary>
 /// <param name="Content">The text content of the message.</param>
 /// <param name="Role">The role of the message.</param>

app/MindWork AI Studio/Provider/OpenRouter/ProviderOpenRouter.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.OpenRouter;
 
-public sealed class ProviderOpenRouter() : BaseProvider("https://openrouter.ai/api/v1/", LOGGER)
+public sealed class ProviderOpenRouter() : BaseProvider(LLMProviders.OPEN_ROUTER, "https://openrouter.ai/api/v1/", LOGGER)
 {
     private const string PROJECT_WEBSITE = "https://github.com/MindWorkAI/AI-Studio";
     private const string PROJECT_NAME = "MindWork AI Studio";
@@ -43,24 +43,7 @@ public sealed class ProviderOpenRouter() : BaseProvider("https://openrouter.ai/a
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
 
         // Prepare the OpenRouter HTTP chat request:
         var openRouterChatRequest = JsonSerializer.Serialize(new ChatCompletionAPIRequest

app/MindWork AI Studio/Provider/Perplexity/ProviderPerplexity.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.Perplexity;
 
-public sealed class ProviderPerplexity() : BaseProvider("https://api.perplexity.ai/", LOGGER)
+public sealed class ProviderPerplexity() : BaseProvider(LLMProviders.PERPLEXITY, "https://api.perplexity.ai/", LOGGER)
 {
     private static readonly ILogger<ProviderPerplexity> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderPerplexity>();
 
@@ -49,24 +49,7 @@ public sealed class ProviderPerplexity() : BaseProvider("https://api.perplexity.
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage()
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the Perplexity HTTP chat request:
         var perplexityChatRequest = JsonSerializer.Serialize(new ChatCompletionAPIRequest

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

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.SelfHosted;
 
-public sealed class ProviderSelfHosted(Host host, string hostname) : BaseProvider($"{hostname}{host.BaseURL()}", LOGGER)
+public sealed class ProviderSelfHosted(Host host, string hostname) : BaseProvider(LLMProviders.SELF_HOSTED, $"{hostname}{host.BaseURL()}", LOGGER)
 {
     private static readonly ILogger<ProviderSelfHosted> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderSelfHosted>();
 
@@ -34,26 +34,15 @@ public sealed class ProviderSelfHosted(Host host, string hostname) : BaseProvide
         
         // Parse the API parameters:
         var apiParameters = this.ParseAdditionalApiParameters();
-        
-        // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
+
+        // Build the list of messages. The image format depends on the host:
+        // - Ollama uses the direct image URL format: { "type": "image_url", "image_url": "data:..." }
+        // - LM Studio, vLLM, and llama.cpp use the nested image URL format: { "type": "image_url", "image_url": { "url": "data:..." } }
+        var messages = host switch
         {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text =>  await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+            Host.OLLAMA => await chatThread.Blocks.BuildMessagesUsingDirectImageUrlAsync(this.Provider, chatModel),
+            _ => await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel),
+        };
         
         // Prepare the OpenAI HTTP chat request:
         var providerChatRequest = JsonSerializer.Serialize(new ChatRequest

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

@@ -1,13 +0,0 @@
-namespace AIStudio.Provider.SelfHosted;
-
-/// <summary>
-/// Chat message model.
-/// </summary>
-/// <param name="Content">The text content of the message.</param>
-/// <param name="Role">The role of the message.</param>
-public record TextMessage(string Content, string Role) : IMessage<string>
-{
-    public TextMessage() : this(string.Empty, string.Empty)
-    {
-    }
-}

app/MindWork AI Studio/Provider/SubContentConverter.cs

@@ -0,0 +1,34 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+using AIStudio.Provider.OpenAI;
+
+namespace AIStudio.Provider;
+
+/// <summary>
+/// Custom JSON converter for the ISubContent interface to handle polymorphic serialization.
+/// </summary>
+/// <remarks>
+/// This converter ensures that when serializing ISubContent objects, all properties
+/// of the concrete implementation (e.g., SubContentText, SubContentImageUrl) are serialized,
+/// not just the properties defined in the ISubContent interface.
+/// </remarks>
+public sealed class SubContentConverter : JsonConverter<ISubContent>
+{
+    private static readonly ILogger<SubContentConverter> LOGGER = Program.LOGGER_FACTORY.CreateLogger<SubContentConverter>();
+
+    public override ISubContent? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        // Deserialization is not needed for request objects, as sub-content is only serialized
+        // when sending requests to LLM providers.
+        LOGGER.LogError("Deserializing ISubContent is not supported. This converter is only used for serializing request messages.");
+        return null;
+    }
+
+    public override void Write(Utf8JsonWriter writer, ISubContent value, JsonSerializerOptions options)
+    {
+        // Serialize the actual concrete type (e.g., SubContentText, SubContentImageUrl) instead of just the ISubContent interface.
+        // This ensures all properties of the concrete type are included in the JSON output.
+        JsonSerializer.Serialize(writer, value, value.GetType(), options);
+    }
+}

app/MindWork AI Studio/Provider/SubContentImageUrlConverter.cs

@@ -0,0 +1,34 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+using AIStudio.Provider.OpenAI;
+
+namespace AIStudio.Provider;
+
+/// <summary>
+/// Custom JSON converter for the ISubContentImageUrl interface to handle polymorphic serialization.
+/// </summary>
+/// <remarks>
+/// This converter ensures that when serializing ISubContentImageUrl objects, all properties
+/// of the concrete implementation (e.g., SubContentImageUrlData) are serialized,
+/// not just the properties defined in the ISubContentImageUrl interface.
+/// </remarks>
+public sealed class SubContentImageUrlConverter : JsonConverter<ISubContentImageUrl>
+{
+    private static readonly ILogger<SubContentImageUrlConverter> LOGGER = Program.LOGGER_FACTORY.CreateLogger<SubContentImageUrlConverter>();
+
+    public override ISubContentImageUrl? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        // Deserialization is not needed for request objects, as sub-content image URLs are only serialized
+        // when sending requests to LLM providers.
+        LOGGER.LogError("Deserializing ISubContentImageUrl is not supported. This converter is only used for serializing request messages.");
+        return null;
+    }
+
+    public override void Write(Utf8JsonWriter writer, ISubContentImageUrl value, JsonSerializerOptions options)
+    {
+        // Serialize the actual concrete type (e.g., SubContentImageUrlData) instead of just the ISubContentImageUrl interface.
+        // This ensures all properties of the concrete type are included in the JSON output.
+        JsonSerializer.Serialize(writer, value, value.GetType(), options);
+    }
+}

app/MindWork AI Studio/Provider/SubContentType.cs

@@ -0,0 +1,39 @@
+namespace AIStudio.Provider;
+
+/// <summary>
+/// Sub content types for OpenAI-compatible API interactions when using multimodal messages.
+/// </summary>
+public enum SubContentType
+{
+    /// <summary>
+    /// Default type for user prompts in multimodal messages. This type is supported across all providers.
+    /// </summary>
+    TEXT,
+    
+    /// <summary>
+    /// Right now only supported by OpenAI and it's responses API. Even other providers that support multimodal messages
+    /// and the responses API do not support this type. They use TEXT instead.
+    /// </summary>
+    INPUT_TEXT,
+    
+    /// <summary>
+    /// Right now only supported by OpenAI and it's responses API. Even other providers that support multimodal messages
+    /// and the responses API do not support this type. They use IMAGE_URL instead.
+    /// </summary>
+    INPUT_IMAGE,
+    
+    /// <summary>
+    /// Default type for images in multimodal messages. This type is supported across all providers.
+    /// </summary>
+    IMAGE_URL,
+    
+    /// <summary>
+    /// The image type is used exclusively by Anthropic's messages API.
+    /// </summary>
+    IMAGE,
+    
+    /// <summary>
+    /// Right now only supported by OpenAI (responses & chat completion API), Google (chat completions API), and Mistral (chat completions API).
+    /// </summary>
+    INPUT_AUDIO,
+}

app/MindWork AI Studio/Provider/X/ProviderX.cs

@@ -9,7 +9,7 @@ using AIStudio.Settings;
 
 namespace AIStudio.Provider.X;
 
-public sealed class ProviderX() : BaseProvider("https://api.x.ai/v1/", LOGGER)
+public sealed class ProviderX() : BaseProvider(LLMProviders.X, "https://api.x.ai/v1/", LOGGER)
 {
     private static readonly ILogger<ProviderX> LOGGER = Program.LOGGER_FACTORY.CreateLogger<ProviderX>();
     
@@ -40,24 +40,7 @@ public sealed class ProviderX() : BaseProvider("https://api.x.ai/v1/", LOGGER)
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessages(async n => new TextMessage
-        {
-            Role = n.Role switch
-            {
-                ChatRole.USER => "user",
-                ChatRole.AI => "assistant",
-                ChatRole.AGENT => "assistant",
-                ChatRole.SYSTEM => "system",
-
-                _ => "user",
-            },
-
-            Content = n.Content switch
-            {
-                ContentText text => await text.PrepareTextContentForAI(),
-                _ => string.Empty,
-            }
-        });
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the xAI HTTP chat request:
         var xChatRequest = JsonSerializer.Serialize(new ChatCompletionAPIRequest