feat: carry the reasoning verdict through to LLMResponse

Both assembly paths fill it, streaming and non-streaming alike. Filling
only one is exactly the divergence this issue exposed: M3 returns
reasoning prose over SSE and nothing at all over the plain endpoint, so
a verdict computed on one path says nothing about the other.

The field defaults to UNKNOWN on both TransportResult and LLMResponse.
A transport that does not judge should not get to declare absence on
the provider's behalf, and a default that stays silent is the only one
that cannot lie.

tests/unit/test_openai_compat.py

@@ -22,7 +22,7 @@ from polygateway.transports.openai_compat import (
     _iter_sse_deltas,
     _sse_data_payload,
 )
-from polygateway.types import ChatRequest, LLMResponse, SourceConfig
+from polygateway.types import ChatRequest, LLMResponse, SourceConfig, ThinkingObservation
 
 
 def _source(**overrides):
@@ -471,6 +471,81 @@ class TestReasoningTokens:
         assert result.reasoning_tokens is None
 
 
+class TestThinkingObservationVerdict:
+    """issue #16/#17: 两条组装路径都必须裁定"推理到底发生没发生"。
+
+    流式与非流式各测一遍是刻意的——只填一条路径正是本 issue 的根因形态:
+    库在其中一条路径上悄悄给出了不同的可观测性,下游无从分辨。
+    """
+
+    def _reasoning_usage(self, reasoning):
+        return {**_USAGE, "completion_tokens_details": {"reasoning_tokens": reasoning}}
+
+    async def test_stream_reasoning_content_is_observed(self):
+        def handler(request):
+            return _sse_stream(
+                _chunk(reasoning="想一下"), _chunk(content="ok"), _chunk(usage=_USAGE)
+            )
+
+        result = await _complete(_transport_for(handler), _source())
+        assert result.thinking_observation is ThinkingObservation.OBSERVED
+
+    async def test_stream_without_any_signal_is_unknown(self):
+        """无正文、无 details: 库不知道,就如实说不知道。"""
+
+        def handler(request):
+            return _sse_stream(_chunk(content="ok"), _chunk(usage=_USAGE))
+
+        result = await _complete(_transport_for(handler), _source())
+        assert result.thinking_observation is ThinkingObservation.UNKNOWN
+
+    async def test_stream_zero_reasoning_tokens_is_absent(self):
+        """上游明确上报 0 才算 ABSENT——这是唯一的"确实没推理"证据。"""
+
+        def handler(request):
+            return _sse_stream(_chunk(content="ok"), _chunk(usage=self._reasoning_usage(0)))
+
+        result = await _complete(_transport_for(handler), _source())
+        assert result.thinking_observation is ThinkingObservation.ABSENT
+
+    async def test_non_stream_reasoning_content_is_observed(self):
+        def handler(request):
+            return httpx.Response(
+                200,
+                json={
+                    "choices": [{"message": {"content": "42", "reasoning_content": "想一下"}}],
+                    "usage": _USAGE,
+                },
+            )
+
+        result = await _complete(_transport_for(handler), _source(), stream=False)
+        assert result.thinking_observation is ThinkingObservation.OBSERVED
+
+    async def test_non_stream_without_any_signal_is_unknown(self):
+        """M3 非流式实测形态: 推理已计费却既不回传正文也不回传 details。"""
+
+        def handler(request):
+            return httpx.Response(
+                200, json={"choices": [{"message": {"content": "42"}}], "usage": _USAGE}
+            )
+
+        result = await _complete(_transport_for(handler), _source(), stream=False)
+        assert result.thinking_observation is ThinkingObservation.UNKNOWN
+
+    async def test_non_stream_zero_reasoning_tokens_is_absent(self):
+        def handler(request):
+            return httpx.Response(
+                200,
+                json={
+                    "choices": [{"message": {"content": "42"}}],
+                    "usage": self._reasoning_usage(0),
+                },
+            )
+
+        result = await _complete(_transport_for(handler), _source(), stream=False)
+        assert result.thinking_observation is ThinkingObservation.ABSENT
+
+
 class TestNonStreamFastPath:
     async def test_non_stream_parses_message(self):
         def handler(request):

tests/unit/test_retry.py

@@ -27,6 +27,7 @@ from polygateway.types import (
     GlobalLimits,
     RetryPolicy,
     SourceConfig,
+    ThinkingObservation,
     TransportResult,
 )
 from tests.contracts.conftest import FakeClock
@@ -225,6 +226,29 @@ class TestObservabilityPassthrough:
         assert resp.cached_prompt_tokens is None and resp.model_reported is None
         assert resp.reasoning_tokens is None
 
+    async def test_thinking_observation_reaches_the_response(self):
+        """issue #16/#17: 裁定归 transport,中间件只透传,不得在途中改判。"""
+        result = TransportResult(
+            content="ok",
+            thinking="想一下",
+            prompt_tokens=10,
+            completion_tokens=5,
+            usage_source="measured",
+            ttft_ms=12.0,
+            max_inter_token_ms=3.0,
+            raw={},
+            thinking_observation=ThinkingObservation.OBSERVED,
+        )
+        mw, *_ = _harness([_src("a")], [result])
+        resp = await mw(_REQ)
+        assert resp.thinking_observation is ThinkingObservation.OBSERVED
+
+    async def test_unjudged_transport_result_stays_unknown(self):
+        """不裁定的 transport(如 OCR)透传出来仍是 UNKNOWN,不被默认成 ABSENT。"""
+        mw, *_ = _harness([_src("a")], [_ok()])
+        resp = await mw(_REQ)
+        assert resp.thinking_observation is ThinkingObservation.UNKNOWN
+
 
 class TestRetryAndFailover:
     async def test_transient_switches_source_then_succeeds(self):

tests/unit/test_types.py

@@ -88,6 +88,30 @@ class TestLLMResponse:
         assert filled.model_reported == "MiniMax-Text-01-250321"
         assert filled.reasoning_tokens == 0  # 上报了且确实没推理,不得与 None 混同
 
+    def test_thinking_observation_defaults_to_unknown(self):
+        """issue #16/#17: 默认必须是 UNKNOWN——"没信号"不得被伪装成"没推理"。
+
+        默认值取 ABSENT 会让每个不填该字段的构造点(测试 fake、其他 transport)
+        都在替上游做一个它没做过的声明,那正是本 issue 要消灭的静默错觉。
+        """
+        resp = LLMResponse("c", "t", "m", "p", 1, 2, 3, None, None, False, "cid")
+        assert resp.thinking_observation is ThinkingObservation.UNKNOWN
+        filled = LLMResponse(
+            "c",
+            "t",
+            "m",
+            "p",
+            1,
+            2,
+            3,
+            None,
+            None,
+            False,
+            "cid",
+            thinking_observation=ThinkingObservation.OBSERVED,
+        )
+        assert filled.thinking_observation is ThinkingObservation.OBSERVED
+
     def test_frozen(self):
         resp = LLMResponse("c", "t", "m", "p", 1, 2, 3, None, None, False, "cid")
         with pytest.raises(dataclasses.FrozenInstanceError):
@@ -264,6 +288,8 @@ class TestAuxTypes:
         # issue #3: 新字段带默认值,不填也能构造(OCR 等其他 transport 零改动)
         assert s.cached_prompt_tokens is None and s.model_reported is None
         assert s.reasoning_tokens is None
+        # issue #16/#17: 不裁定的 transport 只能说"不知道",不能替上游说"没推理"
+        assert s.thinking_observation is ThinkingObservation.UNKNOWN
 
 
 class TestOcrTypes: