diff --git a/yunkes/src/views/ChatTimeline.vue b/yunkes/src/views/ChatTimeline.vue
index 20bd1b6..33ee895 100644
--- a/yunkes/src/views/ChatTimeline.vue
+++ b/yunkes/src/views/ChatTimeline.vue
@@ -85,13 +85,15 @@ function scrollToBottom(): void {
 
 /** Shared query params for both DM and group timelines. */
 function queryFor(pageNum: number) {
+  // 日期窗为 both-or-neither：仅当 start/end 同时存在才透传，避免单边过滤
+  // (getMessages→clean() 会逐键剔除 undefined，单边 start 会变成下界过滤)。
+  const hasWindow = windowStart.value != null && windowEnd.value != null
   return {
     channel: channelTyped.value,
     owner_account_id: props.ownerId,
     talker_id: isGroup.value ? undefined : props.talkerId,
     room_id: isGroup.value ? props.roomId : undefined,
-    start: windowStart.value,
-    end: windowEnd.value,
+    ...(hasWindow ? { start: windowStart.value, end: windowEnd.value } : {}),
     page: pageNum,
     page_size: PAGE_SIZE,
   }