添加会话级固定预设

Co-Authored-By: Claude <noreply@anthropic.com>

server/handlers.go

@@ -26,6 +26,11 @@ type activeProfileRequest struct {
 	Name string `json:"name"`
 }
 
+type createConversationRequest struct {
+	Preset       string `json:"preset"`
+	PresetPrompt string `json:"preset_prompt"`
+}
+
 func (s *Server) indexHandler(c *gin.Context) {
 	profile := s.aiState.ActiveProfile()
 	c.HTML(http.StatusOK, "chat.html", gin.H{
@@ -89,7 +94,15 @@ func (s *Server) listConversationsHandler(c *gin.Context) {
 }
 
 func (s *Server) createConversationHandler(c *gin.Context) {
-	conv, err := s.store.Create()
+	var req createConversationRequest
+	if c.Request.Body != nil {
+		_ = c.ShouldBindJSON(&req)
+	}
+	preset := req.PresetPrompt
+	if strings.TrimSpace(preset) == "" {
+		preset = req.Preset
+	}
+	conv, err := s.store.CreateWithPreset(preset)
 	if err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": "创建对话失败: " + err.Error()})
 		return
@@ -118,6 +131,41 @@ func (s *Server) deleteConversationHandler(c *gin.Context) {
 	c.Status(http.StatusNoContent)
 }
 
+func conversationPresetPrompt(store *conversation.Store, id string) string {
+	id = strings.TrimSpace(id)
+	if id == "" || store == nil {
+		return ""
+	}
+	conv, err := store.Get(id)
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(conv.PresetPrompt)
+}
+
+func conversationContextMessages(messages []message.ChatMessage, preset string) []message.ChatMessage {
+	preset = strings.TrimSpace(preset)
+	if preset == "" {
+		return append([]message.ChatMessage(nil), messages...)
+	}
+	cleaned := filterRequestPresetMessages(messages)
+	contextMessages := make([]message.ChatMessage, 0, len(cleaned)+1)
+	contextMessages = append(contextMessages, message.ChatMessage{Role: "system", Content: preset, Hidden: true})
+	contextMessages = append(contextMessages, cleaned...)
+	return contextMessages
+}
+
+func filterRequestPresetMessages(messages []message.ChatMessage) []message.ChatMessage {
+	filtered := make([]message.ChatMessage, 0, len(messages))
+	for _, msg := range messages {
+		if msg.Hidden && strings.EqualFold(msg.Role, "system") {
+			continue
+		}
+		filtered = append(filtered, msg)
+	}
+	return filtered
+}
+
 // chatHandler 流式 SSE 对话接口
 func (s *Server) chatHandler(c *gin.Context) {
 	var req message.ChatRequest
@@ -163,8 +211,8 @@ func (s *Server) chatHandler(c *gin.Context) {
 	usage := stream.NewTracker()
 	ctx = stream.ContextWithTracker(ctx, usage)
 
-	contextMessages := req.Messages
-	chatWindow := contextwindow.ApplyChatWindow(req.Messages, profile.Config.ContextWindowTokens)
+	contextMessages := conversationContextMessages(req.Messages, conversationPresetPrompt(s.store, req.ConversationID))
+	chatWindow := contextwindow.ApplyChatWindow(contextMessages, profile.Config.ContextWindowTokens)
 	if chatWindow.Removed > 0 || chatWindow.Overflow {
 		emitTrace("context_window", "chat", "success", "已清理对话历史上下文", map[string]any{"max_tokens": chatWindow.MaxTokens, "before_tokens": chatWindow.BeforeTokens, "after_tokens": chatWindow.AfterTokens, "removed_messages": chatWindow.Removed, "overflow": chatWindow.Overflow, "base_overflow": chatWindow.BaseOverflow})
 	}