test: close two always-green holes in the dimension tests

The cache-key test only asserted a hit, so a key degraded to a constant
would still pass it. Adding a namespace control group that must miss
proves the key still distinguishes inputs; verified by degrading
build_cache_key to a constant and watching the case go red.

The allow_nan=False branch had no test at all. A ChatRequest built with
a nan meta value (bypassing the entry validation, i.e. a future entry
point that forgets to validate) must drop the row and not raise;
verified red by removing allow_nan=False.

Also restore the read-only file permissions in a finally block, so a
failing assertion does not get masked by a PermissionError from tmp_path
cleanup; rename the warnings fixture to captured_warnings so it stops
shadowing the stdlib module; and drop a downstream business term from a
fixture value (zero-business-assumption rule).

tests/integration/test_postgres_telemetry.py

@@ -424,7 +424,7 @@ CREATE TABLE {schema}.llm_calls (
 _PRE_TENANT_INSERT = (
     "INSERT INTO {schema}.llm_calls (call_id, model, provider, source_name, messages, response, "
     "prompt_tokens, completion_tokens, usage_source, latency_ms) "
-    "VALUES ($1, 'm', 'p', 's1', '[]', 'contract text', 1, 2, 'measured', 10)"
+    "VALUES ($1, 'm', 'p', 's1', '[]', 'old body', 1, 2, 'measured', 10)"
 )
 
 
@@ -434,8 +434,12 @@ def _search_path_dsn(dsn: str, schema: str) -> str:
 
 
 @pytest.fixture
-async def warnings():
-    """捕获库发出的 WARNING;loguru 不经标准 logging,pytest 的 caplog 抓不到。"""
+async def captured_warnings():
+    """捕获库发出的 WARNING;loguru 不经标准 logging,pytest 的 caplog 抓不到。
+
+    名字避开裸 `warnings`: 那会遮蔽标准库模块名,本文件将来任何一次
+    `import warnings` 都会与它静默互相顶掉,而报错点离真因很远。
+    """
     from loguru import logger
 
     messages: list[str] = []
@@ -608,7 +612,7 @@ class TestCallerDimensionsAcceptance:
             await conn.close()
 
     async def test_backfill_failure_degrades_per_row_not_wholesale(
-        self, least_privilege_pre_tenant_dsn, warnings
+        self, least_privilege_pre_tenant_dsn, captured_warnings
     ):
         """补列失败的降级方向: 记 warning、不置 `_failed`、后续 INSERT 仍照发。
 
@@ -619,8 +623,8 @@ class TestCallerDimensionsAcceptance:
         try:
             await _record_minimal(recorder, call_id=_cid("lpp1"))  # 不得抛
             assert recorder._failed is False
-            assert any("补列失败" in m for m in warnings)
+            assert any("补列失败" in m for m in captured_warnings)
             # 缺列的表上 INSERT 必然失败;逐行 warning 正是"INSERT 照发了"的证据
-            assert any("写入失败" in m for m in warnings)
+            assert any("写入失败" in m for m in captured_warnings)
         finally:
             await recorder.aclose()

tests/unit/test_client.py

@@ -232,13 +232,23 @@ class TestCallerDimensions:
         assert recorder.rows == []
 
     async def test_meta_does_not_enter_cache_key(self):
-        """仅 meta 不同必须仍命中缓存(F1): 进 key 会让存量缓存全量冷启动且不报错。"""
-        client = _client(cache=InMemoryCache(), cache_namespace="proj", cache_ttl_s=3600)
+        """仅 meta 不同必须仍命中缓存(F1): 进 key 会让存量缓存全量冷启动且不报错。
+
+        带对照组: 只断言"命中"的话,缓存 key 退化成常量(忽略一切输入)时本用例
+        照样绿——那是恒真断言。故再改一个**确实进 key** 的维度(namespace)断言
+        miss,证明 key 仍在区分输入,"meta 不进 key"才是被测出来的结论。
+        """
+        cache = InMemoryCache()  # 两个 client 共用一份存储,否则对照组的 miss 是白来的
+        client = _client(cache=cache, cache_namespace="proj", cache_ttl_s=3600)
         async with client:
             first = await client.chat(self._MSG, meta={"batch": "b-1"})
             second = await client.chat(self._MSG, meta={"batch": "b-2"})
         assert first.cache_hit is False and second.cache_hit is True
 
+        other_ns = _client(cache=cache, cache_namespace="other", cache_ttl_s=3600)
+        async with other_ns:
+            assert (await other_ns.chat(self._MSG, meta={"batch": "b-1"})).cache_hit is False
+
 
 class TestModelFingerprint:
     """配置级采样参数须进缓存身份,否则改 temperature 后仍读旧缓存(决策 C)。"""

tests/unit/test_telemetry.py

@@ -318,7 +318,7 @@ CREATE TABLE llm_calls (
 _PRE_TENANT_INSERT = (
     "INSERT INTO llm_calls (call_id, model, provider, source_name, messages, response, "
     "prompt_tokens, completion_tokens, usage_source, latency_ms) "
-    "VALUES ('old-row', 'm', 'p', 's1', '[]', 'contract text', 1, 2, 'measured', 10)"
+    "VALUES ('old-row', 'm', 'p', 's1', '[]', 'old body', 1, 2, 'measured', 10)"
 )
 
 
@@ -399,12 +399,16 @@ class TestSQLiteCallerDimensionsAcceptance:
         conn.close()
         db.chmod(0o444)
 
+        # finally 还原权限位: 任一断言先失败时,不还原会让 tmp_path 清理连带报错,
+        # 把"某条断言失败"的真因盖成一个无关的 PermissionError
+        try:
             recorder = SQLiteRecorder(db)  # 不得抛
             assert recorder._conn is not None  # 补列失败 ≠ recorder 失能
             await _record_minimal(recorder, call_id="doomed")  # 只读库写不进,但不得抛
             recorder.close()
+        finally:
+            db.chmod(0o644)
 
-        db.chmod(0o644)  # 还原,让 tmp_path 清理不受阻
         stale = sqlite3.connect(db)
         assert [r[1] for r in stale.execute("PRAGMA table_info(llm_calls)")] == (
             _EXPECTED_COLUMNS[:-2]
@@ -875,6 +879,25 @@ class TestEmitterCallerDimensions:
         )
         assert "研发" in rec.rows[0]["meta"]
 
+    async def test_non_finite_meta_value_drops_the_row_instead_of_poisoning_it(self):
+        """入口失守时 `allow_nan=False` 的真实结果: 整行降级丢弃,且不抛给调用方。
+
+        直接构造带 `nan` 的 `ChatRequest`(绕过 `validate_caller_dimensions` 这道
+        主防线,模拟将来某个新入口忘记校验)。没有 `allow_nan=False` 时,
+        `json.dumps` 会写出裸 `NaN` 字面量——PG 的 JSONB 会拒收,但 **SQLite 的
+        `meta` 是 TEXT 列不做校验**,那串非法 JSON 会被静默存进去,污染此后一切
+        按 JSON 解析 meta 的分析。宁可丢一行遥测,也不要一行毒数据。
+
+        同时断言不抛: 遥测的降级方向是"静默降级"(铁律),把调用方的一次正常
+        业务调用因为一个维度值炸掉,方向反了。
+        """
+        rec = _MemoryRecorder()
+        req = ChatRequest(messages=[{"role": "user", "content": "hi"}], meta={"k": float("nan")})
+        await TelemetryEmitter(rec).emit_terminal_failure(
+            request=req, call_id="c", latency_ms=1, error="dead"
+        )
+        assert rec.rows == []
+
 
 class TestCostWithCachedTier:
     """issue #3: 命中部分按缓存单价计费,避免 cost 系统性高估。"""