fix: make the sampling invariant test actually enforce the constraint

The test passed overlay and sampling as separate objects while production
aliases them, so an in-place mutation slipped through it. Also syncs the
telemetry schema page and adds the missing postgres round-trip assertion.

tests/integration/test_postgres_telemetry.py

@@ -11,6 +11,7 @@ DSN 走 .env `PGW_TELEMETRY_PG_DSN`,缺则 skip。该实例上有 app/chs_prod
 from __future__ import annotations
 
 import asyncio
+import json
 import os
 from uuid import uuid4
 
@@ -180,9 +181,12 @@ class TestObservabilityColumns:
             await _record_minimal(recorder, call_id=_cid("hit"), cached_prompt_tokens=64)
             await _record_minimal(recorder, call_id=_cid("zero"), cached_prompt_tokens=0)
             await _record_minimal(recorder, call_id=_cid("model"), model_reported="MiniMax-01")
+            await _record_minimal(
+                recorder, call_id=_cid("samp"), sampling='{"seed": 42, "temperature": 0}'
+            )
             rows = await _fetch(
                 dsn,
-                "SELECT call_id, cached_prompt_tokens, model_reported FROM llm_calls "
+                "SELECT call_id, cached_prompt_tokens, model_reported, sampling FROM llm_calls "
                 "WHERE call_id LIKE $1",
                 f"{_RUN_PREFIX}-%",
             )
@@ -191,6 +195,9 @@ class TestObservabilityColumns:
             assert by_id[_cid("zero")]["cached_prompt_tokens"] == 0  # 真实零命中 ≠ NULL
             assert by_id[_cid("model")]["cached_prompt_tokens"] is None
             assert by_id[_cid("model")]["model_reported"] == "MiniMax-01"
+            # issue #4: PG 侧也须验非空 sampling 能读回原值(不只是列存在)
+            assert json.loads(by_id[_cid("samp")]["sampling"]) == {"seed": 42, "temperature": 0}
+            assert by_id[_cid("hit")]["sampling"] is None
         finally:
             await recorder.aclose()
 

tests/unit/test_ports.py

@@ -116,6 +116,7 @@ class _DummyRecorder:
         cost,
         cached_prompt_tokens,
         model_reported,
+        sampling,
     ) -> None: ...
 
 

tests/unit/test_structured.py

@@ -193,7 +193,14 @@ class TestSamplingSnapshotInvariant:
         terminal = ScriptedTerminal(["not json at all", '{"answer": 1, "reason": "r"}'])
         mw = _mw(strategy=NativeSchemaStrategy(), max_retries=1)
         await mw(
-            ChatRequest(messages=_MSGS, structured=Verdict, sampling=caller_sampling),
+            # overlay 与 sampling 传**同一个对象**,复现 client.py 的别名关系
+            # ——否则中间件就地改写 overlay 时不会波及 sampling,这条执法就是空的
+            ChatRequest(
+                messages=_MSGS,
+                structured=Verdict,
+                overlay=caller_sampling,
+                sampling=caller_sampling,
+            ),
             terminal,
         )
         assert len(terminal.requests) == 2  # 确实重问过
@@ -205,11 +212,20 @@ class TestSamplingSnapshotInvariant:
             assert "response_format" not in seen.sampling
 
     async def test_middleware_does_not_mutate_caller_mapping(self):
-        """决策 E 的第二条约束: 中间件只能 replace 派生,不得就地改这两个 dict。"""
+        """决策 E 的第二条约束: 中间件只能 replace 派生,不得就地改这两个 dict。
+
+        同样传同一对象: 生产中 overlay 与 sampling 是别名,任何对 overlay 的
+        就地改写都会同步毒化缓存 key 与遥测列。
+        """
         caller_sampling = {"seed": 7}
         terminal = ScriptedTerminal(['{"answer": 1, "reason": "r"}'])
         await _mw(strategy=NativeSchemaStrategy())(
-            ChatRequest(messages=_MSGS, structured=Verdict, sampling=caller_sampling),
+            ChatRequest(
+                messages=_MSGS,
+                structured=Verdict,
+                overlay=caller_sampling,
+                sampling=caller_sampling,
+            ),
             terminal,
         )
         assert caller_sampling == {"seed": 7}  # 调用方的对象未被污染