diff --git a/services/room-service/internal/storage/mysql/outbox.go b/services/room-service/internal/storage/mysql/outbox.go
index acb371b5..b37f094f 100644
--- a/services/room-service/internal/storage/mysql/outbox.go
+++ b/services/room-service/internal/storage/mysql/outbox.go
@@ -161,14 +161,17 @@ func (r *Repository) claimPendingOutboxFromTable(ctx context.Context, table stri
 	nowMS := time.Now().UTC().UnixMilli()
 	appCode := appcode.FromContext(ctx)
 	records := make([]outbox.Record, 0, limit)
+	// pending 新事件的 next_retry_at_ms 固定为 0，真正决定可见性的是未被抢占的 lock_until_ms；
+	// 因此 pending 分支必须走 claim 索引按 created_at_ms 直接取最早记录，避免在机器人 outbox 堆积时用
+	// next_retry_at_ms range 扫描数百万历史行再 filesort。retryable 才按 next_retry_at_ms 到期时间排序。
 	claimBranches := []struct {
 		query string
 		args  []any
 	}{
 		{
 			query: `SELECT app_code, event_id, event_type, room_id, status, worker_id, lock_until_ms, envelope, created_at_ms, retry_count, next_retry_at_ms, COALESCE(last_error, '')
-			 FROM ` + table + ` FORCE INDEX (` + pendingIndex + `)
-			 WHERE app_code = ? AND status = ? AND next_retry_at_ms <= ? AND lock_until_ms IS NULL
+			 FROM ` + table + ` FORCE INDEX (` + claimIndex + `)
+			 WHERE app_code = ? AND status = ? AND lock_until_ms IS NULL AND next_retry_at_ms <= ?
 			 ORDER BY created_at_ms ASC, event_id ASC
 			 LIMIT ? FOR UPDATE SKIP LOCKED`,
 			args: []any{appCode, outbox.StatusPending, nowMS},
@@ -177,7 +180,7 @@ func (r *Repository) claimPendingOutboxFromTable(ctx context.Context, table stri
 			query: `SELECT app_code, event_id, event_type, room_id, status, worker_id, lock_until_ms, envelope, created_at_ms, retry_count, next_retry_at_ms, COALESCE(last_error, '')
 			 FROM ` + table + ` FORCE INDEX (` + pendingIndex + `)
 			 WHERE app_code = ? AND status = ? AND next_retry_at_ms <= ? AND lock_until_ms IS NULL
-			 ORDER BY created_at_ms ASC, event_id ASC
+			 ORDER BY next_retry_at_ms ASC, created_at_ms ASC, event_id ASC
 			 LIMIT ? FOR UPDATE SKIP LOCKED`,
 			args: []any{appCode, outbox.StatusRetryable, nowMS},
 		},