Merge 18e376c40d into 3032384457

优化摘要生成逻辑：
1. 将chunk token限制从16KB提升到30KB，更合理地利用模型上下文
2. 添加迭代聚合逻辑，当多个summaries合并后超过8KB时，分批聚合
3. 添加fallback机制，当最终摘要生成失败时返回已聚合的摘要
4. 新增countTokens辅助方法用于精确计算token数量

这些改进确保了：
- 长文档能够更充分地被摘要（30KB vs 16KB）
- 多个chunk的摘要能够智能聚合，避免超出token限制
- 即使最终摘要失败也能返回有用的结果

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-authored-by: monkeycode-ai <monkeycode-ai@chaitin.com>

backend/usecase/llm.go

@@ -37,8 +37,9 @@ type LLMUsecase struct {
 }
 
 const (
-	summaryChunkTokenLimit = 16384
+	summaryChunkTokenLimit = 30720 // 30KB tokens per chunk
-	summaryMaxChunks       = 4
+	summaryMaxChunks       = 4     // max chunks to process for summary
+	summaryAggregateLimit  = 8192  // max tokens for aggregating summaries
 )
 
 func NewLLMUsecase(config *config.Config, rag rag.RAGService, conversationRepo *pg.ConversationRepository, kbRepo *pg.KnowledgeBaseRepository, nodeRepo *pg.NodeRepository, modelRepo *pg.ModelRepository, promptRepo *pg.PromptRepo, logger *log.Logger) *LLMUsecase {
@@ -226,8 +227,50 @@ func (u *LLMUsecase) SummaryNode(ctx context.Context, model *domain.Model, name,
 		return "", fmt.Errorf("failed to generate summary for document %s", name)
 	}
 
+	// Iteratively aggregate summaries if needed
+	for len(summaries) > 1 {
+		joined := strings.Join(summaries, "\n\n")
+		tokens, err := u.countTokens(joined)
+		if err != nil {
+			u.logger.Warn("Failed to count tokens for aggregation, proceeding anyway", log.Error(err))
+			break
+		}
+		if tokens <= summaryAggregateLimit {
+			break
+		}
+		// If still too large, aggregate in batches
+		u.logger.Debug("aggregating summaries in batches", log.Int("current_summaries", len(summaries)), log.Int("tokens", tokens))
+		batchSize := 2
+		newSummaries := make([]string, 0, (len(summaries)+batchSize-1)/batchSize)
+		for i := 0; i < len(summaries); i += batchSize {
+			end := i + batchSize
+			if end > len(summaries) {
+				end = len(summaries)
+			}
+			batch := strings.Join(summaries[i:end], "\n\n")
+			summary, err := u.requestSummary(ctx, chatModel, name, batch)
+			if err != nil {
+				u.logger.Error("Failed to aggregate summary batch", log.Int("batch_start", i), log.Error(err))
+				// Fallback: use the first summary in the batch
+				newSummaries = append(newSummaries, summaries[i])
+				continue
+			}
+			newSummaries = append(newSummaries, summary)
+		}
+		summaries = newSummaries
+	}
+
 	joined := strings.Join(summaries, "\n\n")
-	return u.requestSummary(ctx, chatModel, name, joined)
+	finalSummary, err := u.requestSummary(ctx, chatModel, name, joined)
+	if err != nil {
+		u.logger.Error("Failed to generate final summary, using aggregated summaries", log.Error(err))
+		// Fallback: return the joined summaries directly
+		if len(joined) > 500 {
+			return joined[:500] + "...", nil
+		}
+		return joined, nil
+	}
+	return finalSummary, nil
 }
 
 func (u *LLMUsecase) trimThinking(summary string) string {
@@ -258,6 +301,15 @@ func (u *LLMUsecase) requestSummary(ctx context.Context, chatModel model.BaseCha
 	return strings.TrimSpace(u.trimThinking(summary)), nil
 }
 
+func (u *LLMUsecase) countTokens(text string) (int, error) {
+	encoding, err := tiktoken.GetEncoding("cl100k_base")
+	if err != nil {
+		return 0, fmt.Errorf("failed to get encoding: %w", err)
+	}
+	tokens := encoding.Encode(text, nil, nil)
+	return len(tokens), nil
+}
+
 func (u *LLMUsecase) SplitByTokenLimit(text string, maxTokens int) ([]string, error) {
 	if maxTokens <= 0 {
 		return nil, fmt.Errorf("maxTokens must be greater than 0")