diff --git a/backend/app/api/action_plans.py b/backend/app/api/action_plans.py
index 694995f6..dcbd9b83 100644
--- a/backend/app/api/action_plans.py
+++ b/backend/app/api/action_plans.py
@@ -124,7 +124,10 @@ def list_plans(
         item["kpi_dimension"] = kpi.dimension if kpi else None
         # 附带KR信息（行动挂KR 2026-08-27）
         if p.kr_id is not None:
-            kr = db.query(KR).filter(KR.id == p.kr_id).first()
+            # 账套隔离（2026-09-18 batch3 读侧同族残余）：kr_id 可能指向对端账套 KR（存量脏行，
+            # 写入侧 create_plan/update_plan 已校验归属但旧行仍存在）→ 富化查询必须带账套，
+            # 否则列表跨账套回显对端 KR 标题
+            kr = db.query(KR).filter(KR.id == p.kr_id, KR.entity_id == entity_id).first()
             item["kr_title"] = kr.title if kr else None
             item["kr_metric_kpi_id"] = kr.metric_kpi_id if kr else None
         else:
diff --git a/backend/tests/test_cross_entity_isolation_batch3_20260918.py b/backend/tests/test_cross_entity_isolation_batch3_20260918.py
index f2390f52..0ebf7120 100644
--- a/backend/tests/test_cross_entity_isolation_batch3_20260918.py
+++ b/backend/tests/test_cross_entity_isolation_batch3_20260918.py
@@ -127,7 +127,7 @@ def _mk_allocation(db: Session, activity: AbcActivity, eid: int, product_code: s
 
 
 def _mk_plan(db: Session, kpi_id: int, eid: int, title: str, **kw) -> ActionPlan:
-    plan = ActionPlan(entity_id=eid, kpi_id=kpi_id, title=title,
+    plan = ActionPlan(entity_id=eid, kpi_id=kpi_id, kr_id=kw.get("kr_id"), title=title,
                       assignee=kw.get("assignee", "张三"), priority="medium",
                       status=kw.get("status", "pending"), progress=0)
     db.add(plan)
@@ -394,6 +394,59 @@ def test_plan_stats_reverse_direction(client: TestClient, db: Session):
     assert s2["pending"] == 1
 
 
+# ──────────────────────────────────────────────
+# D6. GET /action-plans 的 KR 富化按会话账套（batch3 读侧同族残余）
+# ──────────────────────────────────────────────
+# 缺陷：list_plans 富化 kr_title 的查询 db.query(KR).filter(KR.id == p.kr_id) 无账套校验
+#      → 存量脏行（action_plans.kr_id 指向对端账套 KR）会让列表跨账套回显对端 KR 标题。
+#      写入侧已在 batch3 修（update_plan/create_plan 校验 kr_id 归属），本用例覆盖读侧。
+
+def _list_plans(client: TestClient, token: str) -> dict:
+    r = client.get(PLANS, headers=auth_header(token))
+    assert r.status_code == 200, r.text
+    return {row["id"]: row for row in r.json()["data"]}
+
+
+def test_list_plans_kr_enrichment_isolated_by_entity(client: TestClient, db: Session):
+    """双向：本账套计划挂对端 KR（存量脏行）→ 列表不回显对端 KR 标题；挂本账套 KR → 正常回显"""
+    k1, k2 = _seed_two_entities(db)
+    kr1 = _mk_objective_kr(db, 1, "e1 KR")
+    kr2 = _mk_objective_kr(db, 2, "e2 KR")
+
+    # e1 账套：一条挂本账套 KR（正对照）+ 一条脏行挂 e2 的 KR
+    good1 = _mk_plan(db, k1.id, 1, "zz e1 挂本账套 KR", kr_id=kr1.id)
+    dirty1 = _mk_plan(db, k1.id, 1, "zz e1 脏行挂对端 KR", kr_id=kr2.id)
+    # e2 账套：反向同理
+    good2 = _mk_plan(db, k2.id, 2, "zz e2 挂本账套 KR", kr_id=kr2.id)
+    dirty2 = _mk_plan(db, k2.id, 2, "zz e2 脏行挂对端 KR", kr_id=kr1.id)
+
+    rows1 = _list_plans(client, _login(client, 1))
+    assert good1.id in rows1 and dirty1.id in rows1, f"e1 会话看不到本账套计划: {sorted(rows1)}"
+    assert rows1[good1.id]["kr_title"] == "e1 KR", (
+        f"e1 本账套 KR 标题未回显: {rows1[good1.id].get('kr_title')!r}"
+    )
+    assert rows1[dirty1.id]["kr_title"] is None, (
+        f"e1 会话跨账套回显了 e2 的 KR 标题 {rows1[dirty1.id]['kr_title']!r}"
+        "（缺陷：list_plans 富化 kr 查询缺 KR.entity_id 校验）"
+    )
+    assert rows1[dirty1.id]["kr_metric_kpi_id"] is None, (
+        f"e1 会话跨账套回显了 e2 KR 的 metric_kpi_id = {rows1[dirty1.id]['kr_metric_kpi_id']!r}"
+    )
+
+    rows2 = _list_plans(client, _login(client, 2))
+    assert good2.id in rows2 and dirty2.id in rows2, f"e2 会话看不到本账套计划: {sorted(rows2)}"
+    assert rows2[good2.id]["kr_title"] == "e2 KR", (
+        f"e2 本账套 KR 标题未回显: {rows2[good2.id].get('kr_title')!r}"
+    )
+    assert rows2[dirty2.id]["kr_title"] is None, (
+        f"e2 会话跨账套回显了 e1 的 KR 标题 {rows2[dirty2.id]['kr_title']!r}"
+    )
+    assert rows2[dirty2.id]["kr_metric_kpi_id"] is None
+
+    # 计划本体归属未被本改动影响：e1 列表不含 e2 的两条计划
+    assert good2.id not in rows1 and dirty2.id not in rows1, "e1 列表混入了 e2 账套计划"
+
+
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 # 鉴权底线（改前改后都应通过）
 # ──────────────────────────────────────────────