diff --git a/src/llm/agents/orchestrator.py b/src/llm/agents/orchestrator.py
index 35fc16d..f54621b 100644
--- a/src/llm/agents/orchestrator.py
+++ b/src/llm/agents/orchestrator.py
@@ -34,11 +34,6 @@ logger = logging.getLogger(__name__)
 _AGENT_PROVIDER_CACHE: dict[str, tuple[float, LLMProvider]] = {}
 _AGENT_PROVIDER_CACHE_TTL = 60.0
 
-# 当前预测的模型覆盖(调用方显式指定)。用模块级变量而非新增形参,因为
-# run_specialists 会被既有测试 mock,加形参会破坏那些测试的调用签名。
-# 由 predict_match_multi 在进入时 set、退出时 reset。
-_ACTIVE_MODEL_OVERRIDE: str | None = None
-
 
 # ── 5 个专家 agent 定义 ──
 # A=近期状态 B=攻防数据 C=主客因素 D=联赛排名 E=历史交锋
@@ -160,16 +155,17 @@ async def run_specialists(
     *,
     version: str = "v1",
     before=None,
+    model_override: str | None = None,
 ) -> list[AgentReport]:
     """并行执行 5 个专家 agent。fail-open: 单个失败不影响其他。
 
     before: 数据截止时间(回测防泄漏)。None 表示不限制。
+    model_override: 调用方显式指定的模型,覆盖各 agent 的层级默认。
 
-    模型覆盖通过 _ACTIVE_MODEL_OVERRIDE 传递,而不是新增形参:既有测试
-    会 mock 本函数(见 tests/test_agent_weights_persist.py),加形参会破坏
-    它们的调用签名。predict_match_multi 在调用前后 set/reset 该变量。
+    注意:model_override 必须作为形参下传,不能用模块级变量中转。
+    backtest 会 asyncio.gather 并发 8 场预测(见 backtest.py 的 Semaphore(8)),
+    模块级变量会被并发调用互相覆盖,导致 A 场的预测用上 B 场的模型。
     """
-    model_override = _ACTIVE_MODEL_OVERRIDE
     tasks = [
         _run_one(spec, header, await _agent_provider(spec.name, tier="specialist", model_override=model_override), version=version, before=before)
         for spec in SPECIALIST_SPECS
@@ -266,14 +262,11 @@ async def predict_match_multi(
     prediction_cutoff_at = cutoff
 
     # 2. 并行专家(各自独立配置,使用统一 cutoff)
-    # 显式 model 覆盖通过模块级变量下传,避免改动 run_specialists 的签名
-    global _ACTIVE_MODEL_OVERRIDE
-    _prev_override = _ACTIVE_MODEL_OVERRIDE
-    _ACTIVE_MODEL_OVERRIDE = model
-    try:
-        reports = await run_specialists(header, version=version, before=cutoff)
-    finally:
-        _ACTIVE_MODEL_OVERRIDE = _prev_override
+    # model 作为形参下传,而非模块级变量:backtest 并发 8 场预测时,
+    # 模块级变量会被并发调用互相覆盖(模型串味)。
+    reports = await run_specialists(
+        header, version=version, before=cutoff, model_override=model
+    )
 
     # 2.5 统计有效专家报告数量
     ok_reports = [r for r in reports if r.status == "ok"]
diff --git a/tests/test_agent_weights_persist.py b/tests/test_agent_weights_persist.py
index 2fe3163..e2a11cc 100644
--- a/tests/test_agent_weights_persist.py
+++ b/tests/test_agent_weights_persist.py
@@ -84,7 +84,7 @@ class TestOrchestratorWritesAgentWeights:
 
         captured_values = {}
 
-        async def mock_specialists(h, *, version, before):
+        async def mock_specialists(h, *, version, before, model_override=None):
             return reports
 
         async def mock_provider(aid, **kw):
diff --git a/tests/test_multi_agent_cutoff.py b/tests/test_multi_agent_cutoff.py
index 920b511..e03100a 100644
--- a/tests/test_multi_agent_cutoff.py
+++ b/tests/test_multi_agent_cutoff.py
@@ -43,7 +43,7 @@ class TestMultiAgentCutoffPropagation:
 
         captured_before = []
 
-        async def mock_run_specialists(header, *, version, before=None):
+        async def mock_run_specialists(header, *, version, before=None, model_override=None):
             captured_before.append(before)
             return []
 
@@ -86,7 +86,7 @@ class TestMultiAgentCutoffPropagation:
 
         captured_before = []
 
-        async def mock_run_specialists(header, *, version, before=None):
+        async def mock_run_specialists(header, *, version, before=None, model_override=None):
             captured_before.append(before)
             return []
 
@@ -118,7 +118,7 @@ class TestMultiAgentCutoffPropagation:
 
         captured_before = []
 
-        async def mock_run_specialists(header, *, version, before=None):
+        async def mock_run_specialists(header, *, version, before=None, model_override=None):
             captured_before.append(before)
             return []
 
diff --git a/tests/test_multi_agent_degraded.py b/tests/test_multi_agent_degraded.py
index 9528be8..94a0a25 100644
--- a/tests/test_multi_agent_degraded.py
+++ b/tests/test_multi_agent_degraded.py
@@ -66,7 +66,7 @@ class TestAllExpertsFailed:
         header = _make_header()
 
         # Mock run_specialists 返回全 error
-        async def mock_run_specialists(header, *, version, before):
+        async def mock_run_specialists(header, *, version, before, model_override=None):
             return _all_error_reports()
 
         # Mock _agent_provider
@@ -131,7 +131,7 @@ class TestAllExpertsFailed:
         """5 个专家全 no_data → status=degraded,不调终裁。"""
         header = _make_header()
 
-        async def mock_run_specialists(header, *, version, before):
+        async def mock_run_specialists(header, *, version, before, model_override=None):
             return _all_no_data_reports()
 
         async def mock_agent_provider(agent_id, *, tier):
@@ -188,7 +188,7 @@ class TestPartialExpertsOk:
         """1 个 ok + 4 个 error → status=success(走终裁)。"""
         header = _make_header()
 
-        async def mock_run_specialists(header, *, version, before):
+        async def mock_run_specialists(header, *, version, before, model_override=None):
             return _mixed_reports()
 
         async def mock_agent_provider(agent_id, *, tier):
@@ -255,7 +255,7 @@ class TestNoAggregatorCallOnDegraded:
         header = _make_header()
         aggregator_called = []
 
-        async def mock_run_specialists(header, *, version, before):
+        async def mock_run_specialists(header, *, version, before, model_override=None):
             return _all_error_reports()
 
         async def mock_agent_provider(agent_id, *, tier):
diff --git a/tests/test_review_required_fixes.py b/tests/test_review_required_fixes.py
index 4eaa07f..e070e45 100644
--- a/tests/test_review_required_fixes.py
+++ b/tests/test_review_required_fixes.py
@@ -13,6 +13,7 @@ from __future__ import annotations
 import inspect
 import logging
 import pathlib
+import re
 
 import pytest
 
@@ -348,9 +349,13 @@ def test_r4_override_does_not_pollute_cache():
     assert "_AGENT_PROVIDER_CACHE[cache_key]" in src
 
 
-async def test_r4_dispatch_sets_override_for_specialists(monkeypatch):
-    """行为测试: predict_match_multi 应把 model 放进 _ACTIVE_MODEL_OVERRIDE,
-    并在 run_specialists 执行期间对 specialist 生效(退出后复位)。
+async def test_r4_dispatch_passes_override_to_specialists(monkeypatch):
+    """行为测试: predict_match_multi 必须把 model 作为**形参**传给 run_specialists。
+
+    早期实现用模块级变量 _ACTIVE_MODEL_OVERRIDE 中转,但 backtest 会
+    asyncio.gather 并发 8 场预测(backtest.py Semaphore(8)),全局变量会被
+    并发调用互相覆盖 → A 场预测用上 B 场的模型。故此处断言「形参传递」,
+    并显式断言该模块级变量已不存在。
 
     参照 tests/test_multi_agent_degraded.py 的 stub 方式,避免触碰真实 DB。
     """
@@ -366,8 +371,8 @@ async def test_r4_dispatch_sets_override_for_specialists(monkeypatch):
         h.match_dt = None
         return h
 
-    async def _fake_specialists(header, *, version, before):
-        seen["override_during_run"] = orch_mod._ACTIVE_MODEL_OVERRIDE
+    async def _fake_specialists(header, *, version, before, model_override=None):
+        seen["override_during_run"] = model_override
         return []
 
     async def _fake_upsert(session, **kw):
@@ -403,14 +408,63 @@ async def test_r4_dispatch_sets_override_for_specialists(monkeypatch):
     monkeypatch.setattr(orch_mod, "run_specialists", _fake_specialists, raising=True)
     monkeypatch.setattr(orch_mod, "_upsert_prediction", _fake_upsert, raising=True)
     monkeypatch.setattr(orch_mod, "get_uow", _FakeUow, raising=True)
-    monkeypatch.setattr(orch_mod, "_ACTIVE_MODEL_OVERRIDE", None, raising=False)
 
     assert get_uow is not None  # 确保 import 生效,session 未被真实打开
 
     await orch_mod.predict_match_multi(999, model="OVERRIDE-X")
 
-    assert seen["override_during_run"] == "OVERRIDE-X"
-    assert orch_mod._ACTIVE_MODEL_OVERRIDE is None, "退出后必须复位"
+    assert seen["override_during_run"] == "OVERRIDE-X", (
+        "model 未作为形参传给 run_specialists"
+    )
+    # 回归守卫: 模块级中转变量必须不存在(并发下会产生模型串味)
+    assert not hasattr(orch_mod, "_ACTIVE_MODEL_OVERRIDE"), (
+        "不应再用模块级 _ACTIVE_MODEL_OVERRIDE 中转 model: backtest 并发 8 场预测时"
+        "会互相覆盖,导致模型串味"
+    )
+
+
+def test_r4_run_specialists_accepts_model_override_parameter():
+    """run_specialists 必须显式接收 model_override 形参(而非读全局)。"""
+    import inspect
+
+    sig = inspect.signature(orch_mod.run_specialists)
+    assert "model_override" in sig.parameters, (
+        "run_specialists 缺少 model_override 形参 —— 并发场景下模型会串味"
+    )
+    assert sig.parameters["model_override"].default is None
+
+
+def test_r4_no_module_level_model_override_global():
+    """并发安全守卫: orchestrator 不得用模块级变量中转 model 覆盖。
+
+    backtest 会 asyncio.gather 并发 8 场预测(backtest.py 的 Semaphore(8)),
+    模块级变量会被并发调用互相覆盖 → A 场的预测用上 B 场的模型(模型串味)。
+    正确做法是把 model 作为形参一路下传。
+
+    说明: 这里用源码级断言而非并发行为测试 —— 真实 run_specialists 会调用
+    数据库(_agent_provider -> load_match_header),在无 DB 的测试环境下
+    无法稳定执行,写出来的并发测试会是 flaky 的假证据(已实测确认)。
+    形参方案与全局方案的判别点清晰且可直接观测,故用源码守卫。
+    """
+    src = _orchestrator_source()
+
+    # 1) 不得存在模块级覆盖变量
+    assert "_ACTIVE_MODEL_OVERRIDE" not in src, (
+        "orchestrator 又引入了模块级 model 覆盖变量 —— 并发预测会模型串味"
+    )
+    # 2) 不得有 `global` 声明去写模型覆盖
+    assert not re.search(r"^\s*global\s+.*MODEL", src, re.M), (
+        "orchestrator 使用 global 声明中转模型覆盖 —— 并发下不安全"
+    )
+    # 3) model_override 必须作为实参出现在 run_specialists 调用里
+    call = re.search(
+        r"await run_specialists\((.*?)\)", src, re.S
+    )
+    assert call, "未找到 run_specialists 调用点"
+    assert "model_override=" in call.group(1), (
+        "run_specialists 调用点未显式传 model_override —— "
+        "model 可能又走回隐式中转,并发下会串味"
+    )
 
 
 # ============================================================