Fixed and improved the system prompt of chats started from assistants (#1172)

app/MindWork AI Studio/Chat/ChatStartRequest.cs

@@ -1,3 +1,3 @@
 namespace AIStudio.Chat;
 
-public sealed record ChatStartRequest(ChatThread ChatThread, bool ApplySelectedChatTemplateToComposer = false, bool PreserveDataSourceOptions = false);
+public sealed record ChatStartRequest(ChatThread ChatThread, bool PreserveDataSourceOptions = false);

app/MindWork AI Studio/Chat/ChatSystemPromptOrigin.cs

@@ -0,0 +1,25 @@
+using AIStudio.Assistants;
+
+namespace AIStudio.Chat;
+
+/// <summary>
+/// Which assistant chose the system prompt of a chat, and how.
+/// </summary>
+/// <remarks>
+/// Stored with a chat which continues the conversation of an assistant, so that the dialog showing the
+/// system prompt can name the assistant, and tell the prompt of the assistant apart from a prompt the
+/// assistant wrote for the chat. A chat without it got its prompt elsewhere: from AI Studio, from a
+/// chat template, or from a version of AI Studio before v26.11.1.
+/// </remarks>
+public sealed record ChatSystemPromptOrigin
+{
+    /// <summary>
+    /// Whether the chat got the prompt of the assistant or a prompt the assistant wrote for the chat.
+    /// </summary>
+    public ChatSystemPromptSource Source { get; set; } = ChatSystemPromptSource.ASSISTANT;
+
+    /// <summary>
+    /// The name of the assistant, as AI Studio showed it when the chat started.
+    /// </summary>
+    public string AssistantName { get; set; } = string.Empty;
+}

app/MindWork AI Studio/Chat/ChatThread.cs

@@ -241,6 +241,15 @@ public sealed record ChatThread
     /// </summary>
     public string SystemPrompt { get; set; } = string.Empty;
 
+    /// <summary>
+    /// Which assistant chose the system prompt of this chat, and how; null when the chat got its prompt elsewhere.
+    /// </summary>
+    /// <remarks>
+    /// Set when a chat continues the conversation of an assistant, see AssistantBase.ChatSystemPrompt, so that
+    /// the dialog showing the system prompt names the assistant rather than calling it the prompt of this chat.
+    /// </remarks>
+    public ChatSystemPromptOrigin? SystemPromptOrigin { get; set; }
+
     /// <summary>
     /// The content blocks of the chat thread.
     /// </summary>
@@ -414,7 +423,7 @@ public sealed record ChatThread
 
         parts.Add(usesChatTemplate
             ? new(SystemPromptPartKind.CHAT_TEMPLATE, systemPromptTextWithChatTemplate) { SourceName = chatTemplate.Name }
-            : new(SystemPromptPartKind.BASE_PROMPT, systemPromptTextWithChatTemplate));
+            : new(SystemPromptPartKind.BASE_PROMPT, systemPromptTextWithChatTemplate) { Origin = this.SystemPromptOrigin });
 
         //
         // Add augmented data, if available:

app/MindWork AI Studio/Chat/SystemPromptPart.cs

@@ -19,6 +19,12 @@ public sealed record SystemPromptPart(SystemPromptPartKind Kind, string Text)
     /// </summary>
     public string SourceName { get; init; } = string.Empty;
 
+    /// <summary>
+    /// Which assistant chose the base prompt, and how, when the chat continues the conversation of an
+    /// assistant; null for every other part.
+    /// </summary>
+    public ChatSystemPromptOrigin? Origin { get; init; }
+
     /// <summary>
     /// The tools whose usage policy the part states; empty for every other part.
     /// </summary>