diff --git a/backend/ai-core/internal/background/thinker.go b/backend/ai-core/internal/background/thinker.go
index 50d0e26..c8ed50f 100644
--- a/backend/ai-core/internal/background/thinker.go
+++ b/backend/ai-core/internal/background/thinker.go
@@ -511,7 +511,7 @@ func NewThinker(
 		lightThinkEnabled:   cfg.LightThinkEnabled,
 		lightThinkInterval:  cfg.LightThinkInterval,
 		silenceTimeout:      cfg.SilenceTimeout,
-		proactiveMsgMinGap:  getEnvDuration("PROACTIVE_MSG_MIN_GAP_SEC", 1800),
+		proactiveMsgMinGap:  getEnvDuration("PROACTIVE_MSG_MIN_GAP_SEC", 300),
 		postChatDelay:       cfg.PostChatDelay,
 		minThinkGap:         cfg.MinThinkGap,
 		offlineThinkGap:     cfg.OfflineThinkGap,
@@ -1956,7 +1956,7 @@ func (t *Thinker) storeThought(content string, toolCallsJSON string, toolCallCou
 			}
 		} else if canPush {
 			gapSinceLast := time.Since(t.lastProactiveTime())
-			if gapSinceLast < 30*time.Minute {
+			if gapSinceLast < t.proactiveMsgMinGap {
 				log.Printf("[后台思考] 主动消息距上次仅 %v，跳过推送", gapSinceLast.Round(time.Second))
 				canPush = false
 			} else {
@@ -1965,6 +1965,11 @@ func (t *Thinker) storeThought(content string, toolCallsJSON string, toolCallCou
 			}
 		}
 	}
+	// 被拦截的主动消息：清除标记，防止 LLM 下次以为发过了
+	if !canPush && proactiveMsg != "" {
+		content = strings.ReplaceAll(content, "【主动消息】", "【未发送】")
+		content = strings.ReplaceAll(content, "【话题发起】", "【未发送】")
+	}
 	// Copy target for use after unlock (avoid race).
 	var targetCopy *ProactiveTarget
 	if proactiveTarget != nil {