feat：语音对话优化

backend/internal/ai/stt/mimo.go

@@ -158,7 +158,8 @@ func (m *MiMoService) Recognize(ctx context.Context, audio []byte, opts Options)
 	}
 
 	if len(mResp.Choices) == 0 {
-		return "", fmt.Errorf("stt: mimo returned empty choices")
+		// MiMo 返回空结果，视为无法识别（非错误），返回空文本
+		return "", nil
 	}
 
 	text := strings.TrimSpace(mResp.Choices[0].Message.Content)

backend/internal/ai/stt/mimo_test.go

@@ -103,9 +103,12 @@ func TestMiMoService_Recognize_EmptyChoices(t *testing.T) {
 	defer srv.Close()
 
 	wav := makeValidWAV([]byte{0x00, 0x00})
-	_, err := s.Recognize(context.Background(), wav, Options{})
-	if err == nil {
-		t.Fatal("expected error for empty choices")
+	text, err := s.Recognize(context.Background(), wav, Options{})
+	if err != nil {
+		t.Fatalf("unexpected error for empty choices: %v", err)
+	}
+	if text != "" {
+		t.Errorf("expected empty string for empty choices, got %q", text)
 	}
 }
 

backend/internal/orchestrator/pipeline.go

@@ -133,24 +133,48 @@ func (p *Pipeline) ProcessQuery(
 		}
 	} else {
 		// 语音模式：执行 STT 语音识别
-		log.Infow("开始语音识别", "request_id", req.RequestID)
+		log.Infow("开始语音识别", "request_id", req.RequestID, "audio_bytes", len(audio))
 		sttResult, err := p.sttService.Recognize(ctx, audio, stt.Options{
 			Encoding:   "pcm_s16le",
 			SampleRate: 16000,
 			Language:   sess.Config.Language,
 		})
 		if err != nil {
-			log.Errorw("语音识别失败", "error", err)
+			log.Errorw("语音识别失败", "error", err, "audio_bytes", len(audio))
 			sender.SendError(models.WsError{
 				Type:      "error",
 				RequestID: req.RequestID,
 				Code:      "STT_ERROR",
-				Message:   "语音识别失败",
+				Message:   "语音识别失败: " + err.Error(),
 			})
 			return err
 		}
 		userText = sttResult
 
+		// STT 返回空文本：未识别到语音，发送结果后直接返回（不调 LLM）
+		if strings.TrimSpace(userText) == "" {
+			log.Infow("语音识别结果为空", "request_id", req.RequestID)
+			userText = "（未识别到语音）"
+			if err := sender.SendSTTResult(models.WsSTTResult{
+				Type:      "stt_result",
+				RequestID: req.RequestID,
+				Text:      userText,
+				IsFinal:   true,
+			}); err != nil {
+				log.Errorw("发送 STT 结果失败", "error", err)
+			}
+			// 发送空的 llm_done 以结束本轮处理
+			latency := time.Since(startTime).Milliseconds()
+			_ = sender.SendLLMDone(models.WsLLMDone{
+				Type:      "llm_done",
+				RequestID: req.RequestID,
+				FullText:  "",
+				Model:     p.model,
+				LatencyMs: latency,
+			})
+			return nil
+		}
+
 		// 发送 STT 结果
 		if err := sender.SendSTTResult(models.WsSTTResult{
 			Type:      "stt_result",