diff --git a/apps/resm/tasks.py b/apps/resm/tasks.py
index a3ec563..bbff0e3 100644
--- a/apps/resm/tasks.py
+++ b/apps/resm/tasks.py
@@ -13,6 +13,7 @@ from datetime import datetime, timedelta
 import random
 from .pdf_utils import _is_elsevier_preview_pdf
 from .d_oaurl import download_from_url_playwright
+from uuid import uuid4
 import asyncio
 import sys
 import os
@@ -492,6 +493,24 @@ def touch_alive(def_name: str):
     """标记该自触发链仍在运行。"""
     cache.set(def_name + ":alive", 1, timeout=ALIVE_TTL)
 
+def claim_chain(def_name: str, chain_id: str):
+    """自触发链去重: 同名任务同时只允许一条链存活。
+
+    cache 里记录当前唯一合法链的 chain_id。无 chain_id 的调用(beat 点火/手动 .delay/
+    历史遗留任务)视为新链接管, 旧链下一轮发现 chain_id 不匹配即自杀, 收敛到单链。
+    返回本任务应携带的 chain_id; 返回 None 表示本任务是重复链, 应立即退出。
+    """
+    key = def_name + ":chain"
+    current = cache.get(key)
+    if chain_id and current and chain_id != current:
+        return None  # 已有更新的链在跑, 本链退出
+    if not chain_id:
+        chain_id = uuid4().hex  # 新点火: 接管成为唯一链
+        cache.set(key, chain_id, timeout=None)
+    elif not current:
+        cache.set(key, chain_id, timeout=None)  # cache 丢失(如 redis 重启)后自愈
+    return chain_id
+
 def is_alive(def_name: str):
     return cache.get(def_name + ":alive") is not None
 
@@ -506,10 +525,13 @@ def ensure_fetch_running():
     return f"ensure_fetch_running started: {started}"
 
 @shared_task(base=CustomTask)
-def get_pdf_from_openalex(number_of_task: int =10):
+def get_pdf_from_openalex(number_of_task: int =10, chain_id: str = None):
     def_name = get_pdf_from_openalex.name
     if not show_task_run(def_name):
         return "stoped"
+    chain_id = claim_chain(def_name, chain_id)
+    if chain_id is None:
+        return "duplicate chain, exit"
     touch_alive(def_name)
 
     # 限流退避中: 不打 API, 慢节奏自重发只为维持 alive, 等 exceed 标记自然过期。
@@ -517,7 +539,7 @@ def get_pdf_from_openalex(number_of_task: int =10):
     if cache.get("openalex_api_exceed"):
         current_app.send_task(
             "apps.resm.tasks.get_pdf_from_openalex",
-            kwargs={"number_of_task": number_of_task},
+            kwargs={"number_of_task": number_of_task, "chain_id": chain_id},
             countdown=60,
         )
         return "openalex_api_exceed, backing off"
@@ -545,6 +567,7 @@ def get_pdf_from_openalex(number_of_task: int =10):
             "apps.resm.tasks.get_pdf_from_openalex",
             kwargs={
                 "number_of_task": number_of_task,
+                "chain_id": chain_id,
             },
             countdown=countdown,
         )
@@ -637,13 +660,16 @@ def _elsevier_fetch_pdf(req, paper):
 
 @shared_task(base=CustomTask)
 def get_abstract_from_elsevier(number_of_task:int = 20, exclude_failed:bool=True,
-                               pdf_number_of_task:int = 20):
+                               pdf_number_of_task:int = 20, chain_id: str = None):
     """Elsevier 单端点合并任务: 同一 DOI 先取 XML(摘要/全文标记), 若有全文则内联
     再取一次 PDF; 并补抓历史上已有全文标记但缺 PDF 的论文。原 get_pdf_from_elsevier 已并入。
     number_of_task: 阶段1(摘要+内联 PDF)每轮上限; pdf_number_of_task: 阶段2(存量补 PDF)每轮上限。"""
     def_name = get_abstract_from_elsevier.name
     if not show_task_run(def_name):
         return "stoped"
+    chain_id = claim_chain(def_name, chain_id)
+    if chain_id is None:
+        return "duplicate chain, exit"
     touch_alive(def_name)
 
     # 待抓摘要(并顺带取 PDF)
@@ -713,6 +739,7 @@ def get_abstract_from_elsevier(number_of_task:int = 20, exclude_failed:bool=True
                 "number_of_task": number_of_task,
                 "exclude_failed": exclude_failed,
                 "pdf_number_of_task": pdf_number_of_task,
+                "chain_id": chain_id,
             },
             countdown=countdown,
         )
@@ -870,10 +897,12 @@ def save_pdf_from_openalex(paper:Paper):
             message = res.json().get("message", "")
         except ValueError:
             message = res.text
-        if "Insufficient credits" in message:
+        # 文案历史上出现过 "Insufficient credits" 和 "Insufficient budget"(每日额度,
+        # UTC 午夜重置), 放宽到 "Insufficient" 统一匹配, 避免落进 2 分钟短退避分支空转
+        if "Insufficient" in message:
             # 额度耗尽: 退避 1 小时
             cache.set("openalex_api_exceed", True, timeout=3600)
-            return "openalex_pdf_error: Insufficient credits"
+            return f"openalex_pdf_error: {message[:100]}"
         # 普通限流(请求过频): 短退避 2 分钟, 避免立刻重试再撞 429
         cache.set("openalex_api_exceed", True, timeout=120)
         return f"openalex_pdf_error: 429 {message[:100]}"