test: verify sampling parameters through the full governance stack

tests/integration/test_governance_stack.py

@@ -4,6 +4,7 @@
 """
 
 import asyncio
+import dataclasses
 import json
 import sqlite3
 
@@ -204,3 +205,74 @@ class TestTransientErrorExport:
 
         assert isinstance(ei.value, polygateway.AllSourcesExhausted)
         assert isinstance(ei.value.__cause__, TransientError)
+
+
+class TestSamplingThroughStack:
+    """issue #4: 采样参数经完整洋葱到达请求体,且缓存/遥测口径一致。"""
+
+    async def test_reaches_wire_and_lands_in_telemetry(self, tmp_path):
+        seen = []
+
+        def handler(request):
+            seen.append(json.loads(request.content))
+            return _sse()
+
+        db = tmp_path / "t.db"
+        recorder = SQLiteRecorder(db)
+        client = _full_client(handler, telemetry=recorder)
+        await client.chat([{"role": "user", "content": "hi"}], overlay={"seed": 42})
+        recorder.close()
+
+        assert seen[0]["seed"] == 42  # 穿过全栈到达线上
+        rows = sqlite3.connect(db).execute("SELECT sampling FROM llm_calls").fetchall()
+        assert json.loads(rows[0][0]) == {"seed": 42}
+
+    async def test_config_level_merges_and_records(self, tmp_path):
+        """源级 extra_body 只有 emit_attempt 记得到(唯一有生效源的入口)。"""
+        seen = []
+
+        def handler(request):
+            seen.append(json.loads(request.content))
+            return _sse()
+
+        src = dataclasses.replace(_source(), extra_body={"temperature": 0})
+        db = tmp_path / "t.db"
+        recorder = SQLiteRecorder(db)
+        client = GatewayClient(
+            scope="llm",
+            sources=[src],
+            selector=RoundRobinSelector(),
+            limiter=InMemoryLimiter(
+                scope="llm", sources={src.name: src}, global_limits=GlobalLimits(0, 0, 0)
+            ),
+            breaker=InMemoryGate(config=_BREAKER),
+            transport=OpenAICompatTransport(
+                client_factory=lambda s: httpx.AsyncClient(transport=httpx.MockTransport(handler))
+            ),
+            retry=RetryPolicy(2, 2.0, 30.0),
+            backpressure=BackpressurePolicy(300.0, 0.01),
+            telemetry=recorder,
+            structured_strategy=JsonRepairStrategy(),
+            sleep=_noop_sleep,
+        )
+        await client.chat([{"role": "user", "content": "hi"}], overlay={"seed": 1})
+        recorder.close()
+
+        assert seen[0]["temperature"] == 0 and seen[0]["seed"] == 1
+        rows = sqlite3.connect(db).execute("SELECT sampling FROM llm_calls").fetchall()
+        assert json.loads(rows[0][0]) == {"seed": 1, "temperature": 0}
+
+    async def test_differing_seed_bypasses_cache_end_to_end(self):
+        """issue 场景全栈回归: 逐 rollout 变 seed 必须真的回源。"""
+        calls = []
+
+        def handler(request):
+            calls.append(json.loads(request.content)["seed"])
+            return _sse()
+
+        client = _full_client(handler, cache=InMemoryCache())
+        await client.chat([{"role": "user", "content": "hi"}], overlay={"seed": 1})
+        await client.chat([{"role": "user", "content": "hi"}], overlay={"seed": 2})
+        second_same = await client.chat([{"role": "user", "content": "hi"}], overlay={"seed": 1})
+        assert calls == [1, 2]  # 两个不同 seed 各自回源
+        assert second_same.cache_hit is True  # 同 seed 才命中