diff --git a/assets/tools_schema_cn.json b/assets/tools_schema_cn.json
index 98fbc211b..657865cfd 100644
--- a/assets/tools_schema_cn.json
+++ b/assets/tools_schema_cn.json
@@ -67,7 +67,7 @@
   }},
   {"type": "function", "function": {
     "name": "start_long_term_update",
-    "description": "准备开始提炼记忆。发现值得长期记忆的信息（环境事实/用户偏好/避坑经验）时调用此工具。已记忆更新或在自主流程内时无需调用。超15轮完成的任务必须调用以沉淀经验",
+    "description": "准备开始提炼记忆。发现值得长期记忆的信息（环境事实/用户偏好/避坑经验）时调用此工具。已记忆更新或在自主流程内时无需调用。达到15轮（含）完成的任务必须调用以沉淀经验",
     "parameters": {"type": "object", "properties": {}}}
   }
 ]
\ No newline at end of file
diff --git a/frontends/tests/test_long_term_settlement_gate.py b/frontends/tests/test_long_term_settlement_gate.py
new file mode 100644
index 000000000..dfcd3c00a
--- /dev/null
+++ b/frontends/tests/test_long_term_settlement_gate.py
@@ -0,0 +1,117 @@
+"""Tests for the completion-time long-term settlement gate (#789).
+
+ga.py imports with stdlib only (agent_loop falls back when plugins.hooks is
+absent), so these tests exercise the real GenericAgentHandler.
+Run: pytest frontends/tests/test_long_term_settlement_gate.py -v
+"""
+import sys
+from pathlib import Path
+from types import SimpleNamespace
+
+ROOT = Path(__file__).resolve().parent.parent.parent
+
+# test_bridge_sessions installs an attribute-less `agent_loop` stub into
+# sys.modules; evict it so the real module can load (ga imports agent_loop).
+_stub = sys.modules.get("agent_loop")
+if _stub is not None and not hasattr(_stub, "BaseHandler"):
+    del sys.modules["agent_loop"]
+sys.path.insert(0, str(ROOT))
+
+from ga import GenericAgentHandler
+
+
+def _handler(turn, history=None):
+    parent = SimpleNamespace(task_dir=None, verbose=False, extrakeyinfo=None, intervene=None)
+    h = GenericAgentHandler(parent, last_history=history or [])
+    h.current_turn = turn
+    return h
+
+
+def _run(gen):
+    """Exhaust a do_* generator -> (yielded strings, returned StepOutcome)."""
+    yields, outcome = [], None
+    try:
+        while True:
+            yields.append(next(gen))
+    except StopIteration as e:
+        outcome = e.value
+    return yields, outcome
+
+
+def _response(content="任务已完成"):
+    return SimpleNamespace(content=content, thinking="", tool_calls=None)
+
+
+_SETTLE_MARK = "记忆提纯"
+
+
+class TestGateThreshold:
+    def test_turn_14_completes_normally(self):
+        h = _handler(14)
+        _, outcome = _run(h.do_no_tool({}, _response()))
+        assert outcome.next_prompt is None
+        assert not h._lt_started
+
+    def test_turn_15_enters_settlement_once(self):
+        h = _handler(15)
+        yields, outcome = _run(h.do_no_tool({}, _response()))
+        assert h._lt_started
+        assert _SETTLE_MARK in outcome.next_prompt
+        assert any("distilling" in y for y in yields)
+
+    def test_turn_40_enters_settlement(self):
+        h = _handler(40)
+        _, outcome = _run(h.do_no_tool({}, _response()))
+        assert _SETTLE_MARK in outcome.next_prompt
+
+    def test_settlement_completion_exits_without_recursion(self):
+        h = _handler(20)
+        _, first = _run(h.do_no_tool({}, _response()))
+        assert first.next_prompt is not None          # settlement phase started
+        _, second = _run(h.do_no_tool({}, _response()))
+        assert second.next_prompt is None             # settlement done -> normal exit
+
+    def test_explicit_call_blocks_gate(self):
+        h = _handler(20)
+        _, settled = _run(h.do_start_long_term_update({}, _response()))
+        assert settled.next_prompt is not None
+        _, outcome = _run(h.do_no_tool({}, _response()))
+        assert outcome.next_prompt is None            # gate already satisfied
+
+    def test_refused_early_call_does_not_block_gate(self):
+        h = _handler(5)
+        _, refused = _run(h.do_start_long_term_update({}, _response()))
+        assert "only used after completing" in refused.data
+        assert not h._lt_started
+        h.current_turn = 20
+        _, outcome = _run(h.do_no_tool({}, _response()))
+        assert _SETTLE_MARK in outcome.next_prompt     # gate still fires later
+
+
+class TestExemptions:
+    def test_no_user_tools_exempt(self, monkeypatch):
+        monkeypatch.setattr(sys, "argv", ["ga", "--no-user-tools"])
+        h = _handler(30)
+        _, outcome = _run(h.do_no_tool({}, _response()))
+        assert outcome.next_prompt is None
+        assert not h._lt_started
+
+    def test_autonomous_flow_exempt(self):
+        h = _handler(30, history=["[USER]: [AUTO]🤖 用户已经离开超过30分钟，执行自动任务。"])
+        _, outcome = _run(h.do_no_tool({}, _response()))
+        assert outcome.next_prompt is None
+        assert not h._lt_started
+
+    def test_normal_user_message_not_exempt(self):
+        h = _handler(30, history=["[USER]: 帮我规划旅行"])
+        _, outcome = _run(h.do_no_tool({}, _response()))
+        assert _SETTLE_MARK in outcome.next_prompt
+
+    def test_autonomous_detection_uses_latest_user_message(self):
+        h = _handler(30, history=[
+            "[USER]: [AUTO] auto task",
+            "[Agent] did stuff",
+            "[USER]: 普通问题",
+        ])
+        _, outcome = _run(h.do_no_tool({}, _response()))
+        assert _SETTLE_MARK in outcome.next_prompt
diff --git a/ga.py b/ga.py
index b2a21df24..a0e786329 100644
--- a/ga.py
+++ b/ga.py
@@ -287,6 +287,7 @@ def __init__(self, parent, last_history=None, cwd='./temp'):
         self.code_stop_signal = []
         self._done_hooks = []
         self.print = safe_print
+        self._lt_started = False
 
     def _get_tool_maxlen(self, l, args, growth_rate=1.0):
         multiplier = 1 + (self.parent.get_ctx_multiplier() - 1) * growth_rate
@@ -474,6 +475,21 @@ def _retry_or_exit(self, prompt):
         if self._empty_ct >= 3: return StepOutcome({}, should_exit=True)
         return StepOutcome({}, next_prompt=prompt)
 
+    _LONG_TASK_TURNS = 15   # schema：15+ turns / 达到15轮（含），turn >= 15 才门控
+
+    def _in_autonomous_flow(self):
+        for line in reversed(self.history_info):
+            if line.startswith('[USER]: '):
+                return line[8:].lstrip().startswith('[AUTO]')
+        return False
+
+    def _needs_long_term_settlement(self):
+        '''完成时一次性结算门控（#789）：schema 措辞只是建议，15+ 轮任务可能不带结算就退出。
+        已结算 / --no-user-tools / 自主流程 / 未到阈值 → 放行正常退出。'''
+        if self._lt_started or self.current_turn < self._LONG_TASK_TURNS: return False
+        if '--no-user-tools' in sys.argv: return False
+        return not self._in_autonomous_flow()
+
     def do_no_tool(self, args, response):
         '''这是一个特殊工具，由引擎自主调用，不要包含在TOOLS_SCHEMA里。
         当模型在一轮中未显式调用任何工具时，由引擎自动触发。
@@ -522,6 +538,8 @@ def do_no_tool(self, args, response):
                 self._exit_plan_mode(); yield "[Info] Plan完成：plan.md中0个[ ]残留，退出plan模式。\n"
         
         #yield "[Info] Final response to user.\n"
+        if self._needs_long_term_settlement():
+            return (yield from self.do_start_long_term_update(args, response))
         return StepOutcome(response, next_prompt=None)
     
     def do_start_long_term_update(self, args, response):
@@ -534,7 +552,10 @@ def do_start_long_term_update(self, args, response):
         path = './memory/memory_management_sop.md'
         if os.path.exists(path): result = 'This is L0:\n' + file_read(path, show_linenos=False)
         else: result = "Memory Management SOP not found. Do not update memory."
-        if self.current_turn < 10: result, prompt = 'start_long_term_update is only used after completing a long turn task!', '\n'
+        if self.current_turn < 10:
+            result, prompt = 'start_long_term_update is only used after completing a long turn task!', '\n'
+        else:
+            self._lt_started = True   # 结算已启动：完成门控放行；settlement 自身完成也不会递归再触发
         return StepOutcome(result, next_prompt=prompt)
 
     def _fold_earlier(self, lines):