Add support for nested and direct image URL formats in message processing

app/MindWork AI Studio/Chat/ListContentBlockExtensions.cs

@@ -99,13 +99,20 @@ public static class ListContentBlockExtensions
     }
 
     /// <summary>
-    /// Processes a list of content blocks using standard role transformations to create message results asynchronously.
+    /// Processes a list of content blocks using direct image URL format to create message results asynchronously.
     /// </summary>
     /// <param name="blocks">The list of content blocks to process.</param>
     /// <param name="selectedProvider">The selected LLM provider.</param>
     /// <param name="selectedModel">The selected model.</param>
-    /// <returns>>An asynchronous task that resolves to a list of transformed message results.</returns>
+    /// <returns>An asynchronous task that resolves to a list of transformed message results.</returns>
-    public static async Task<IList<IMessageBase>> BuildMessagesUsingStandardsAsync(
+    /// <remarks>
+    /// Uses direct image URL format where the image data is placed directly in the image_url field:
+    /// <code>
+    /// { "type": "image_url", "image_url": "data:image/jpeg;base64,..." }
+    /// </code>
+    /// This format is used by OpenAI, Mistral, and Ollama.
+    /// </remarks>
+    public static async Task<IList<IMessageBase>> BuildMessagesUsingDirectImageUrlAsync(
         this List<ContentBlock> blocks,
         LLMProviders selectedProvider,
         Model selectedModel) => await blocks.BuildMessagesAsync(
@@ -113,20 +120,54 @@ public static class ListContentBlockExtensions
             selectedModel,
             StandardRoleTransformer,
             StandardTextSubContentFactory,
-            StandardImageSubContentFactory);
+            DirectImageSubContentFactory);
+
+    /// <summary>
+    /// Processes a list of content blocks using nested image URL format to create message results asynchronously.
+    /// </summary>
+    /// <param name="blocks">The list of content blocks to process.</param>
+    /// <param name="selectedProvider">The selected LLM provider.</param>
+    /// <param name="selectedModel">The selected model.</param>
+    /// <returns>An asynchronous task that resolves to a list of transformed message results.</returns>
+    /// <remarks>
+    /// Uses nested image URL format where the image data is wrapped in an object:
+    /// <code>
+    /// { "type": "image_url", "image_url": { "url": "data:image/jpeg;base64,..." } }
+    /// </code>
+    /// This format is used by LM Studio, VLLM, llama.cpp, and other OpenAI-compatible providers.
+    /// </remarks>
+    public static async Task<IList<IMessageBase>> BuildMessagesUsingNestedImageUrlAsync(
+        this List<ContentBlock> blocks,
+        LLMProviders selectedProvider,
+        Model selectedModel) => await blocks.BuildMessagesAsync(
+            selectedProvider,
+            selectedModel,
+            StandardRoleTransformer,
+            StandardTextSubContentFactory,
+            NestedImageSubContentFactory);
 
     private static ISubContent StandardTextSubContentFactory(string text) => new SubContentText
     {
         Text = text,
     };
 
-    private static async Task<ISubContent> StandardImageSubContentFactory(FileAttachmentImage attachment) => new SubContentImageUrl
+    private static async Task<ISubContent> DirectImageSubContentFactory(FileAttachmentImage attachment) => new SubContentImageUrl
     {
         ImageUrl = await attachment.TryAsBase64() is (true, var base64Content)
             ? $"data:{attachment.DetermineMimeType()};base64,{base64Content}"
             : string.Empty,
     };
 
+    private static async Task<ISubContent> NestedImageSubContentFactory(FileAttachmentImage attachment) => new SubContentImageUrlNested
+    {
+        ImageUrl = new SubContentImageUrlData
+        {
+            Url = await attachment.TryAsBase64() is (true, var base64Content)
+                ? $"data:{attachment.DetermineMimeType()};base64,{base64Content}"
+                : string.Empty,
+        },
+    };
+
     private static string StandardRoleTransformer(ChatRole role) => role switch
     {
         ChatRole.USER => "user",

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

@@ -40,7 +40,7 @@ public sealed class ProviderAlibabaCloud() : BaseProvider(LLMProviders.ALIBABA_C
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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/BaseProvider.cs

@@ -49,6 +49,7 @@ public abstract class BaseProvider : IProvider, ISecretId
             new MessageBaseConverter(),
             new SubContentConverter(),
             new SubContentImageSourceConverter(),
+            new SubContentImageUrlConverter(),
         },
         AllowTrailingCommas = false
     };

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

@@ -40,7 +40,7 @@ public sealed class ProviderDeepSeek() : BaseProvider(LLMProviders.DEEP_SEEK, "h
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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

@@ -40,7 +40,7 @@ public class ProviderFireworks() : BaseProvider(LLMProviders.FIREWORKS, "https:/
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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/GWDG/ProviderGWDG.cs

@@ -40,7 +40,7 @@ public sealed class ProviderGWDG() : BaseProvider(LLMProviders.GWDG, "https://ch
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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

@@ -40,7 +40,7 @@ public class ProviderGoogle() : BaseProvider(LLMProviders.GOOGLE, "https://gener
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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

@@ -40,7 +40,7 @@ public class ProviderGroq() : BaseProvider(LLMProviders.GROQ, "https://api.groq.
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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

@@ -40,7 +40,7 @@ public sealed class ProviderHelmholtz() : BaseProvider(LLMProviders.HELMHOLTZ, "
         var apiParameters = this.ParseAdditionalApiParameters();
             
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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

@@ -45,7 +45,7 @@ public sealed class ProviderHuggingFace : BaseProvider
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var message = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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/Mistral/ProviderMistral.cs

@@ -38,7 +38,7 @@ public sealed class ProviderMistral() : BaseProvider(LLMProviders.MISTRAL, "http
         var apiParameters = this.ParseAdditionalApiParameters();
 
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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/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/ProviderOpenAI.cs

@@ -134,11 +134,14 @@ public sealed class ProviderOpenAI() : BaseProvider(LLMProviders.OPEN_AI, "https
                 },
                 
                 // Chat Completion API uses IMAGE_URL:
-                false => new SubContentImageUrl
+                false => new SubContentImageUrlNested
                 {
-                    ImageUrl = await attachment.TryAsBase64(token: token) is (true, var base64Content)
+                    ImageUrl = new SubContentImageUrlData
-                        ? $"data:{attachment.DetermineMimeType()};base64,{base64Content}"
+                    {
-                        : string.Empty,
+                        Url = await attachment.TryAsBase64(token: token) is (true, var base64Content)
+                            ? $"data:{attachment.DetermineMimeType()};base64,{base64Content}"
+                            : 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/OpenRouter/ProviderOpenRouter.cs

@@ -43,7 +43,7 @@ public sealed class ProviderOpenRouter() : BaseProvider(LLMProviders.OPEN_ROUTER
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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

@@ -49,7 +49,7 @@ public sealed class ProviderPerplexity() : BaseProvider(LLMProviders.PERPLEXITY,
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        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

@@ -35,8 +35,14 @@ public sealed class ProviderSelfHosted(Host host, string hostname) : BaseProvide
         // Parse the API parameters:
         var apiParameters = this.ParseAdditionalApiParameters();
 
-        // Build the list of messages:
+        // Build the list of messages. The image format depends on the host:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        // - 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
+        {
+            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/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/X/ProviderX.cs

@@ -40,7 +40,7 @@ public sealed class ProviderX() : BaseProvider(LLMProviders.X, "https://api.x.ai
         var apiParameters = this.ParseAdditionalApiParameters();
         
         // Build the list of messages:
-        var messages = await chatThread.Blocks.BuildMessagesUsingStandardsAsync(this.Provider, chatModel);
+        var messages = await chatThread.Blocks.BuildMessagesUsingNestedImageUrlAsync(this.Provider, chatModel);
         
         // Prepare the xAI HTTP chat request:
         var xChatRequest = JsonSerializer.Serialize(new ChatCompletionAPIRequest