feat: 优化情景切换功能

backend/internal/ws/handler.go

@@ -10,6 +10,7 @@ import (
 	"github.com/gin-gonic/gin"
 	"github.com/gorilla/websocket"
 
+	"github.com/hhs/camtalk/internal/ai/llm"
 	"github.com/hhs/camtalk/internal/auth"
 	"github.com/hhs/camtalk/internal/config"
 	"github.com/hhs/camtalk/internal/errors"
@@ -277,7 +278,47 @@ func serveWS(c *gin.Context, sessionMgr session.Manager, orch orchestrator.Orche
 				errors.SendWSError(client, errors.CodeInternalError, "", err)
 				continue
 			}
-			logger.Log.Infow("config updated", "session", sessionID)
+
+			scenarioID := ""
+			if msg.Payload.Scenario != nil {
+				scenarioID = *msg.Payload.Scenario
+			}
+			logger.Log.Infow("config updated", "session", sessionID, "scenario", scenarioID)
+
+			// 如果切换了情景（非自由对话），返回首句引导
+			if scenarioID != "" && scenarioID != "free_chat" {
+				sess, err := client.sessionMgr.Get(context.Background(), sessionID)
+				if err == nil && sess != nil {
+					greeting := llm.GetScenarioGreeting(scenarioID, sess.Config.Language)
+					if greeting != "" {
+						// 发送首句作为 AI 消息
+						_ = client.SendJSON(models.WsLLMChunk{
+							Type:      "llm_chunk",
+							RequestID: "scenario_greeting",
+							Delta:     greeting,
+							Role:      "assistant",
+						})
+
+						doneMsg := models.WsLLMDone{
+							Type:      "llm_done",
+							RequestID: "scenario_greeting",
+							FullText:  greeting,
+							Model:     "",
+							LatencyMs: 0,
+						}
+						doneMsg.TokensUsed.Prompt = 0
+						doneMsg.TokensUsed.Completion = 0
+						doneMsg.TokensUsed.Total = 0
+						_ = client.SendJSON(doneMsg)
+
+						// 追加首句到历史记录
+						_ = client.sessionMgr.AppendMessage(context.Background(), sessionID, models.Message{
+							Role:    "assistant",
+							Content: greeting,
+						})
+					}
+				}
+			}
 
 		case "interrupt":
 			logger.Log.Infow("interrupt received", "session", sessionID)