diff --git a/internal/plugins/webui/handler.go b/internal/plugins/webui/handler.go
index b81270e..f2e5f0e 100644
--- a/internal/plugins/webui/handler.go
+++ b/internal/plugins/webui/handler.go
@@ -1693,7 +1693,10 @@ func (h *Handler) handleChatEvents(w http.ResponseWriter, r *http.Request) {
 	// writeCh 不 close：Subscribe 回调闭包持有它，handler 退出后回调仍可能被
 	// 总线异步触发，close 后再发送会 panic（send on closed channel，生产日志中
 	// 单日数千次）。writer goroutine 通过 done 退出；发送侧 select on done 防泄漏。
-	writeCh := make(chan string, 64)
+	// 缓冲加大到 512 且 writer 做批量合并：reasoning/content 增量是高频小包，
+	// 每条单独 flush 会因 socket 写慢而填满小缓冲导致 delta 被丢弃（表现为
+	// 前端只能等最终的 agent_output 整段，体感延迟）。
+	writeCh := make(chan string, 512)
 	writerDone := make(chan struct{})
 	go func() {
 		defer func() {
@@ -1702,12 +1705,32 @@ func (h *Handler) handleChatEvents(w http.ResponseWriter, r *http.Request) {
 			}
 			close(writerDone)
 		}()
+		// 批量合并窗口：16ms 内收集的增量一次性 flush，降 flush 次数、
+		// 避免高频小包拖慢 socket 写导致 writeCh 积压丢 delta。
+		pending := make([]string, 0, 64)
+		flushPending := func() {
+			if len(pending) == 0 {
+				return
+			}
+			for _, line := range pending {
+				fmt.Fprintf(w, "%s\n", line)
+			}
+			flusher.Flush()
+			pending = pending[:0]
+		}
+		flushTicker := time.NewTicker(16 * time.Millisecond)
+		defer flushTicker.Stop()
 		for {
 			select {
 			case line := <-writeCh:
-				fmt.Fprintf(w, "%s\n", line)
-				flusher.Flush()
+				pending = append(pending, line)
+				if len(pending) >= 64 {
+					flushPending()
+				}
+			case <-flushTicker.C:
+				flushPending()
 			case <-done:
+				flushPending()
 				return
 			}
 		}