diff --git a/app/service/risk_judgement_service.py b/app/service/risk_judgement_service.py
index 0dd8ee2..89cd7a8 100644
--- a/app/service/risk_judgement_service.py
+++ b/app/service/risk_judgement_service.py
@@ -49,6 +49,7 @@ def assess_alert_detail(detail: dict[str, Any]) -> dict[str, Any]:
 
 
 def _assess_list_rule(rule: str, item: dict[str, Any]) -> dict[str, Any]:
+    item = _flatten_merged_evidence(item)
     if rule == "RW-018":
         # 原先这里**完全不看 item**，无条件返回"可考虑放行"，而且理由文本是硬编码的
         # "现有摘要显示交易来自有效定投工单"。于是列表里那些渠道并不匹配、或证据里
@@ -101,7 +102,32 @@ def _assess_list_rule(rule: str, item: dict[str, Any]) -> dict[str, Any]:
     )
 
 
+def _flatten_merged_evidence(detail: dict[str, Any]) -> dict[str, Any]:
+    """把"合并预警"的嵌套证据摊回顶层，再交给各条规则的研判函数。
+
+    同一笔交易命中多条规则时，扫描器会把它们合并成一条
+    （`risk_scan_service._merge_same_transaction_alerts`）。合并后的 `evidence_snapshot`
+    只保留 `product_id` 和 `merged_alerts`，各条**原有的证据键被塞进
+    `merged_alerts[].evidence`**；而各研判函数读的是**顶层键**（`snapshot.get("ratio")`
+    之类），于是合并过的预警一律读不到证据、降级成"缺证据无法复核" ——
+    合并本来是为了少几条噪音，结果把这些预警的研判全废掉了（docs/25 P2）。
+
+    在入口统一摊平：顶层已有的键优先（它来自 priority_score 最高的那条主预警），
+    再按顺序补入各子条目的证据键。所有规则共用这一步，不必各自去认嵌套结构。
+    """
+    snapshot = _mapping(detail.get("evidence_snapshot"))
+    merged = snapshot.get("merged_alerts")
+    if not isinstance(merged, list):
+        return detail
+    flat = dict(snapshot)
+    for entry in merged:
+        for key, value in _mapping(_mapping(entry).get("evidence")).items():
+            flat.setdefault(key, value)
+    return {**detail, "evidence_snapshot": flat}
+
+
 def _assess_detail_rule(rule: str, detail: dict[str, Any]) -> dict[str, Any]:
+    detail = _flatten_merged_evidence(detail)
     if rule == "RW-003":
         return _assess_rw003(detail)
     if rule == "RW-007":
diff --git a/tests/unit/service/test_risk_judgement_merged_evidence.py b/tests/unit/service/test_risk_judgement_merged_evidence.py
new file mode 100644
index 0000000..c2eb138
--- /dev/null
+++ b/tests/unit/service/test_risk_judgement_merged_evidence.py
@@ -0,0 +1,90 @@
+"""合并预警的证据必须能被研判读到（docs/25 P2）。
+
+**问题**：同一笔交易命中多条规则时，扫描器会把它们合并成一条
+（`risk_scan_service._merge_same_transaction_alerts`），合并后的 `evidence_snapshot`
+只留 `product_id` 和 `merged_alerts`，各条**原有的证据键被塞进
+`merged_alerts[].evidence`**。而研判函数读的是**顶层键**（`snapshot.get("ratio")` 之类），
+于是合并过的预警一律读不到证据、降级成"缺证据无法复核" —— 合并本来是为了少几条噪音，
+结果把这些预警的研判全废了。
+
+修法是在研判入口统一摊平（`_flatten_merged_evidence`），列表级与详情级共用。
+"""
+
+from typing import Any
+
+from app.service.risk_judgement_service import (
+    _assess_detail_rule,
+    _flatten_merged_evidence,
+)
+
+
+def _merged(**nested_evidence: Any) -> dict[str, Any]:
+    return {
+        "transaction": {"amount": "600000"},
+        "evidence_snapshot": {
+            "product_id": 7001,
+            "merged_alerts": [
+                {"alert_type": "大额赎回", "evidence": nested_evidence},
+            ],
+        },
+    }
+
+
+def test_non_merged_detail_is_returned_unchanged() -> None:
+    detail = {"evidence_snapshot": {"ratio": "0.9"}}
+
+    assert _flatten_merged_evidence(detail) == detail
+
+
+def test_nested_evidence_is_lifted_to_top_level() -> None:
+    flat = _flatten_merged_evidence(_merged(ratio="0.9", average_amount="100"))["evidence_snapshot"]
+
+    assert flat["ratio"] == "0.9"
+    assert flat["average_amount"] == "100"
+    assert flat["product_id"] == 7001  # 原有键不丢
+    assert "merged_alerts" in flat  # 嵌套结构保留，可追溯性不受影响
+
+
+def test_top_level_value_wins_over_nested() -> None:
+    """冲突时保留顶层 —— 它来自 priority_score 最高的那条主预警。"""
+    detail = {
+        "evidence_snapshot": {
+            "ratio": "9",
+            "merged_alerts": [{"alert_type": "A", "evidence": {"ratio": "1"}}],
+        }
+    }
+
+    assert _flatten_merged_evidence(detail)["evidence_snapshot"]["ratio"] == "9"
+
+
+def test_multiple_merged_entries_are_all_lifted() -> None:
+    detail = {
+        "evidence_snapshot": {
+            "product_id": 1,
+            "merged_alerts": [
+                {"alert_type": "A", "evidence": {"ratio": "0.9"}},
+                {"alert_type": "B", "evidence": {"average_amount": "100"}},
+            ],
+        }
+    }
+    flat = _flatten_merged_evidence(detail)["evidence_snapshot"]
+
+    assert flat["ratio"] == "0.9"
+    assert flat["average_amount"] == "100"
+
+
+def test_rw003_no_longer_degrades_on_merged_evidence() -> None:
+    """报告描述的原始症状：合并后 RW-003 读不到 ratio、一律降级。
+
+    对比"没有 ratio"与"ratio 藏在 merged_alerts 里"两种输入 —— 摊平之后后者应当
+    真的把 ratio 读进来，于是两条路径的研判结果不再相同。
+    """
+    without_ratio = {
+        "transaction": {"amount": "600000"},
+        "evidence_snapshot": {"product_id": 7001},
+    }
+
+    degraded = _assess_detail_rule("RW-003", without_ratio)
+    recovered = _assess_detail_rule("RW-003", _merged(ratio="0.9"))
+
+    assert str(degraded) != str(recovered), "摊平后应当读到嵌套的 ratio，研判结果应不同"