助手按需查看：点名的一个都没认出来时（常见的是拿数据源说明里的中文词当表名），同一次查看按需求在那几个来源里挑，不让模型为拿真名再看一次，没认出来的照样写「没找到」；候选库一张表都没探查到时不再说「按需求没挑出来」，照实说尚未探查结构、不交空目录，查看算没完成；点名不在这一轮的数据源不补空目录（真实模型验收发现）

backend/app/look/service.py

@@ -4,7 +4,9 @@
   1. need 没写：回「look 要写 need」，不算次数；次数用完：回「按已查看的结构完成」，不再查看。
   2. targets 按类型分组（旧写法 tables:[{source, table}] 读进来换成 kind=table）。写了 name 的点名直取，不调挑选模型；
      只写了 kind（和 source）的、或者整个没写 targets 的，按 need 在那一类里挑（没写时挑这个入口的第一类）。
-  3. 挑选失败或挑出来是空的：交回那一类的目录（status=index），写明原因，请模型点名再看。
+  3. 挑选失败或挑出来是空的：交回那一类的目录（status=index），写明原因，请模型点名再看。点名的一个都没认出来时，
+     按 need 在那几个来源里挑（同只写类别），没认出来的照样写「没找到」；候选里一个能查看的都没有（库还没探查表
+     结构）时没有目录可交，status=failed，照实说原因。
   4. 这一批对象这一轮都已经看过：回「已在上面」，不重新排一遍。
   5. 各类给详情，合计受 LOOK_RESULT_CHARS 约束；记一条记录（id、by、need、status、objects、用时）。
 
@@ -36,6 +38,7 @@ INDEX_PROMPT = ("没能按需求挑出{what}：{reason}。下面是候选的{wha
 EMPTY_PROMPT = ("按这个需求没有挑出相关的{what}。这一步确实要用到{what}的话，从下面的目录里点名再 look；"
                 "不需要就接着写：\n{index}")
 FAILED_PROMPT = "这一次查看出错了：{reason}。按已有的信息接着写"
+UNAVAILABLE_PROMPT = "没有可查看的{what}：{reason}。按已有的信息接着写，不要猜{what}的名字和字段"
 #: 按需求挑出来是空的：写进 look 事件的 reason，界面上照原话显示
 EMPTY_REASON = "按这个需求没有挑出相关的{what}"
 UNKNOWN_KIND_PROMPT = "这一轮不能查看这一类对象：{kinds}（能查看的：{allowed}）"
@@ -184,21 +187,33 @@ class LookService:
         keys: set[str] = set()
         indexed: list[str] = []
         empty: list[str] = []
+        unavailable: list[str] = []
         budget = LOOK_RESULT_CHARS
         for kind_name in dict.fromkeys([*named, *picks]):
             kind = self.kinds[kind_name]
             found, missing = await kind.resolve(named.get(kind_name, [])) if kind_name in named else ([], [])
+            fallback = bool(missing) and not found and kind_name not in picks
+            if fallback:
+                # 点名的一个都没认出来（常见的是拿说明里的中文词当表名）：按 need 在那几个来源里挑，和只写类别时一样，
+                # 不让模型为了拿到真名再 look 一次。没认出来的照样写进「没找到」，不拿挑出来的冒充点名的
+                picks[kind_name] = list(dict.fromkeys(str(t["source"]) for t in missing if t.get("source"))) or None
             if kind_name in picks:
                 within = picks[kind_name] or sources
                 chosen, reason = await kind.pick(need, within)
                 if reason is not None or not chosen:
                     index = await kind.index(within)
-                    indexed.append(INDEX_PROMPT.format(what=kind.label, reason=reason, index=index) if reason
-                                   else EMPTY_PROMPT.format(what=kind.label, index=index))
-                    if reason is not None:
+                    if not index and reason is not None:
+                        # 候选里一个能查看的都没有（库还没探查表结构）：没有目录可交，照实说原因，算查看没完成
+                        unavailable.append(UNAVAILABLE_PROMPT.format(what=kind.label, reason=reason))
                         record["reason"] = reason
-                    else:
-                        empty.append(kind.label)
+                    elif index or not fallback:
+                        # 点名的来源本身不在这一轮里（目录是空的）：「没找到数据源」已经说清楚了，不再补一段空目录
+                        indexed.append(INDEX_PROMPT.format(what=kind.label, reason=reason, index=index) if reason
+                                       else EMPTY_PROMPT.format(what=kind.label, index=index))
+                        if reason is not None:
+                            record["reason"] = reason
+                        else:
+                            empty.append(kind.label)
                 found += [o for o in chosen if kind.key(o) not in {kind.key(f) for f in found}]
             if not found and not missing:
                 continue
@@ -210,8 +225,10 @@ class LookService:
         if unknown:
             parts.append(UNKNOWN_KIND_PROMPT.format(kinds="、".join(dict.fromkeys(unknown)),
                                                     allowed="、".join(self.kinds)))
-        parts += indexed
-        if indexed and not keys:
+        parts += indexed + unavailable
+        if unavailable and not indexed and not keys:
+            record["status"] = "failed"
+        elif indexed and not keys:
             # 一个对象都没给出详情、交回的是目录：挑选失败（有原因）或按需求没挑出来（返回空）
             record["status"] = "index"
             record.setdefault("reason", EMPTY_REASON.format(what="、".join(empty)))

backend/app/look/tables.py

@@ -236,6 +236,12 @@ class TableKind:
 
     async def pick(self, need: str, sources: list[str] | None) -> tuple[list[TableRef], str | None]:
         candidates, _ = self._candidates(sources)
+        if not any(self.plans[i].tables for i in candidates):
+            # 候选库一张表都没探查到：不是「按需求没挑出来」，照实说为什么是空的（和概览行同一句）
+            bare = [self.plans[i] for i in candidates] if sources else self.plans
+            if bare:
+                return [], "；".join(f"数据源「{p.name}」{introspect.why_empty(p.source.schema_cache or {})}"
+                                    for p in bare)
         pool = [TableRef(i, key, "picked") for i in candidates for key in self.plans[i].tables]
         if len(pool) <= PICK_LIMIT:
             return pool, None

backend/tests/test_copilot_table_pick.py

@@ -458,3 +458,49 @@ async def test_the_old_tables_field_still_looks(scenic_source):
     result = await looks.look({"op": "look", "need": "门店",
                                "tables": [{"source": scenic_source.name, "table": "stores"}]}, LookBudget())
     assert result.record["objects"][0]["named"] == ["stores"] and "store_code  TEXT" in result.text
+
+
+async def test_names_that_match_nothing_fall_back_to_picking_by_need(monkeypatch, small_source):
+    """模型拿说明里的中文词点名（「订单」「客户」）一个都没认出来：同一次查看里按需求挑，不让它为了拿到真名再看一次。
+    小库不调挑选模型、全部给出；没认出来的照样写进「没找到」，不拿挑出来的冒充点名的。"""
+    fake = FakePicker(error=AssertionError("小库不该调挑选模型"))
+    _use_picker(monkeypatch, fake)
+    looks = await _service([small_source])
+    result = await looks.look({"op": "look", "need": "每位客户的订单金额", "targets": [
+        {"kind": "table", "source": small_source.name, "name": "订单"},
+        {"kind": "table", "source": small_source.name, "name": "客户"}]}, LookBudget())
+    record = result.record
+    assert record["status"] == "ok" and not fake.calls
+    (block,) = record["objects"]
+    assert block["named"] == [] and sorted(block["picked"]) == ["customers", "orders"]
+    assert block["missing"] == ["订单", "客户"]
+    assert "customer_id" in result.text and f"没找到：{small_source.name} 的 订单" in result.text
+
+
+async def test_names_in_an_unknown_source_do_not_hand_back_an_empty_index(small_source):
+    looks = await _service([small_source])
+    result = await looks.look({"op": "look", "need": "退款", "targets": [
+        {"kind": "table", "source": "没有这个库", "name": "refunds"}]}, LookBudget())
+    assert "没找到数据源「没有这个库」" in result.text
+    assert "目录" not in result.text and result.record["status"] == "ok"
+
+
+async def test_a_source_never_introspected_says_so_instead_of_an_empty_pick():
+    """库接上了但还没探查表结构：不是「按需求没挑出来」，照实说为什么是空的，查看算没完成（不交空目录）。"""
+    async with SessionLocal() as session:
+        row = DataSource(name=f"look_bare_{uuid.uuid4().hex[:8]}", kind="sqlite", database="/nonexistent.db",
+                         description="门店、订单、客户")
+        session.add(row)
+        await session.commit()
+        await session.refresh(row)
+        session.expunge(row)
+    try:
+        looks = await _service([row])
+        for line in ({"op": "look", "need": "各地区销售额"},
+                     {"op": "look", "need": "各地区销售额", "targets": [{"kind": "table", "name": "订单"}]}):
+            result = await looks.look(line, LookBudget())
+            assert result.record["status"] == "failed", line
+            assert result.record["reason"] == f"数据源「{row.name}」尚未探查结构"
+            assert "尚未探查结构" in result.text and "目录" not in result.text
+    finally:
+        await drop_source(row.id)