diff --git a/backend/app/engine/masking.py b/backend/app/engine/masking.py
index 58f3bac0..eee69f4a 100644
--- a/backend/app/engine/masking.py
+++ b/backend/app/engine/masking.py
@@ -2020,8 +2020,9 @@ def mask_query_result(payload: dict[str, Any], masked: Iterable[str], kind: str
     - 列名不换（模型自己写的，换了它引用的列名就对不上）；结果里一列都没取自遮罩列、也没有可按值换的原样交回：数值的
       汇总、只数个数的查询不受影响
 
-    交回的 secrets 只有这份结果里的遮罩值（known 调用方自己有）。分析本身出了意外，整份结果的列都遮：这一步挡在模型
-    前面，分析的缺陷不能把原值放过去（宁可多遮）。"""
+    交回的 secrets 只有这份结果里的遮罩值（known 调用方自己有）。分析本身出了意外（认列、认标签、逐格换值哪一步都算），
+    整份结果的每一格都遮、全部的列记成查询时遮掉的（_masked_whole）：这一步挡在模型前面，分析的缺陷不能把原值放过去
+    （宁可多遮）。"""
     base = {str(c).strip().lower() for c in masked if str(c).strip()}
     columns = [str(c) for c in payload.get("columns") or []]
     given = known is not None and bool(known.strong)
@@ -2046,11 +2047,25 @@ def mask_query_result(payload: dict[str, Any], masked: Iterable[str], kind: str
         view, _ = _masked_view(payload, hidden, pool, embedded=True, rename=False)
     except Exception:  # noqa: BLE001 - 认不准就整份遮掉，原值不交给模型
         logger.warning("核查查询的遮罩分析出错，整份结果按遮罩处理", exc_info=True)
-        hidden, own = {c.lower() for c in columns}, _Secrets()
-        view, _ = _masked_view(payload, hidden, own, rename=False)
+        return QueryMask(_masked_whole(payload), columns, _Secrets())
     return QueryMask(view, [c for c in columns if c.lower() in hidden], own)
 
 
+def _masked_whole(payload: dict[str, Any]) -> dict[str, Any]:
+    """整份结果的每一格都换成「已遮罩」、类型都记成文本：遮罩分析出了意外时的兜底。不经 _masked_view——出意外的可能
+    就是它，兜底跟着出意外，原值就挡不住了。列名、SQL 是模型自己写的，照原样。"""
+    word = _masked_word()
+    rows: list[Any] = []
+    for row in payload.get("rows") or []:
+        if isinstance(row, list):
+            rows.append([word] * len(row))
+        elif isinstance(row, dict):
+            rows.append(dict.fromkeys(row, word))
+        else:
+            rows.append(word)
+    return {**payload, "rows": rows, "column_types": {str(c): "text" for c in payload.get("columns") or []}}
+
+
 #: 查询报错里引号括起来的一段（Postgres、DuckDB、MySQL 把转换失败的值写在引号里：invalid input syntax for type
 #: bigint: "139-0000-0001"）。引号前后紧挨着字母数字的不算（can't、isn't 里的撇号）
 _QUOTED_ERROR = re.compile(r"(?<![0-9A-Za-z_])(\"[^\"\n]*\"|'[^'\n]*')(?![0-9A-Za-z_])")
diff --git a/backend/tests/test_masking_tool_boundary.py b/backend/tests/test_masking_tool_boundary.py
new file mode 100644
index 00000000..b5db6244
--- /dev/null
+++ b/backend/tests/test_masking_tool_boundary.py
@@ -0,0 +1,92 @@
+"""工具边界先遮（engine/masking.py 的 mask_query_result）的收口：认不准就整份遮，多遮也不改写没设遮罩的数值证据。
+
+- 遮罩分析本身出了意外（认遮罩列、标签列、逐格换值的哪一步都算）：整份结果的每一格都是「已遮罩」，交给模型的、落库的
+  都一样，masked_at_query 记全部的列。兜底不再经出意外的那一步（以前兜底又调了一遍逐格换值的那一步，它出意外时兜底跟着
+  出意外，结果没交出去，也没有测试证明「整份遮」这句保证）
+- 按值遮只换文字格：没设遮罩的数值列（访问次数正好等于某一笔被遮的金额）原样，存下的证据和数据库里的一样，双盲复算照常
+  取得到；文字格里整格就是遮罩值、夹着遮罩值的照换，换过的格子记进快照（masked_cells），格子引用指到它们照实说是遮罩。
+  占位的短词（未知、暂无……）不当遮罩值，没设遮罩的列、备注里的同一个词照原样
+
+模型一律是 MockChatModel 剧本，数据源是现造的 SQLite 文件，手机号、姓名、金额、访问次数都是虚构的。
+"""
+from __future__ import annotations
+
+import json
+
+import pytest
+from httpx import ASGITransport, AsyncClient
+
+from app.core import artifact_store
+from app.data.engine import engines
+from app.engine import masking
+from app.main import app
+from tests.test_verify_agent import Script, q
+from tests.test_verify_agent_masking import (  # noqa: F401 - clean_spend 是自动用上的夹具
+    MASKED,
+    SALES,
+    VALUE_SCHEMA,
+    _cells,
+    _clean,
+    _source,
+    ask,
+    clean_spend,
+    masked_shop,
+)
+
+
+# --------------------------------------------------------------------------
+# 分析出意外：整份遮
+# --------------------------------------------------------------------------
+
+
+def _broken(*args, **kwargs):
+    raise RuntimeError("遮罩分析里的意外")
+
+
+PAYLOAD = {"sql": "SELECT id, buyer_phone, note FROM sales", "columns": ["id", "buyer_phone", "note"],
+           "rows": [[1, "13900000001", "客户来电"], [2, "13900000002", "例行回访"]],
+           "column_types": {"id": "number", "buyer_phone": "text", "note": "text"}}
+
+
+@pytest.mark.parametrize("step", ["_derived_hidden", "_snapshot_labels", "_masked_view"])
+def test_a_failing_analysis_masks_every_cell(monkeypatch, step):
+    """认遮罩列、认标签列、逐格换值，哪一步出了意外都整份遮：每一格都是「已遮罩」、类型记成文本，整列遮掉的是全部的列。"""
+    monkeypatch.setattr(masking, step, _broken)
+    done = masking.mask_query_result(json.loads(json.dumps(PAYLOAD)), ["buyer_phone"], "sqlite")
+    assert done.payload["rows"] == [[MASKED] * 3, [MASKED] * 3]
+    assert done.payload["column_types"] == {"id": "text", "buyer_phone": "text", "note": "text"}
+    assert done.columns == ["id", "buyer_phone", "note"]
+    assert done.payload["sql"] == PAYLOAD["sql"], "SQL 是模型自己写的，照原样"
+    assert not done.secrets.strong, "认不准，不收值"
+
+
+def test_a_failing_analysis_masks_rows_of_any_shape(monkeypatch):
+    """行是字典的结果同样整份遮。"""
+    monkeypatch.setattr(masking, "_masked_view", _broken)
+    payload = {"sql": "SELECT id, buyer_phone FROM sales", "columns": ["id", "buyer_phone"],
+               "rows": [{"id": 1, "buyer_phone": "13900000001"}]}
+    done = masking.mask_query_result(payload, ["buyer_phone"], "sqlite")
+    assert done.payload["rows"] == [{"id": MASKED, "buyer_phone": MASKED}]
+
+
+@pytest.mark.parametrize("step", ["_derived_hidden", "_masked_view"])
+async def test_the_model_and_the_snapshot_see_only_masks_when_the_analysis_fails(monkeypatch, masked_shop, step):
+    """端到端：分析出了意外，交给模型的工具结果、落库的快照、通用接口给的都只有「已遮罩」，masked_at_query 是全部的列；
+    格子引用照实说是遮罩列，不采信。"""
+    monkeypatch.setattr(masking, step, _broken)
+    name = masked_shop
+    sql = "SELECT id, region, buyer_phone AS 手机号, amount FROM sales ORDER BY id"
+    script = Script(monkeypatch, [q(name, sql, "c1")], {"value": {"alias": "Q1", "row": 0, "column": "amount"},
+                                                        "rationale": "x"})
+    out, _ = await ask(name)
+    seen = json.loads(script.tool_results()["c1"].split("\n", 1)[1])
+    assert seen["rows"] == [[MASKED] * 4] * 4, seen
+    snapshot = artifact_store.load(out.queries[0]["artifact"])
+    assert snapshot["rows"] == [[MASKED] * 4] * 4
+    assert snapshot["masked_at_query"] == ["id", "region", "手机号", "amount"]
+    assert _clean(json.dumps(snapshot, ensure_ascii=False))
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as client:
+        got = await client.get(f"/api/artifacts/{out.queries[0]['artifact']}")
+    assert got.status_code == 200 and _clean(got.text) and "1200" not in got.text
+    assert out.result["value"] is None
+    assert out.cells[0]["reason"] == "Q1 的「amount」取自设置了遮罩的列，查询时已遮罩，不采信"