feat: add DeepSeek extreme reasoning tier

tests/test_provider.py

@@ -21,10 +21,15 @@ def disable_retry_sleep(monkeypatch: pytest.MonkeyPatch) -> None:
 async def _complete_with_handler(
     settings: Settings,
     handler: Callable[[httpx.Request], httpx.Response | Awaitable[httpx.Response]],
+    **kwargs,
 ) -> dict:
     async with httpx.AsyncClient(transport=httpx.MockTransport(handler)) as client:
         provider = ModelProvider(settings, client)
-        return await provider.complete(model="test-model", messages=[{"role": "user", "content": "hello"}])
+        return await provider.complete(
+            model="test-model",
+            messages=[{"role": "user", "content": "hello"}],
+            **kwargs,
+        )
 
 
 async def test_complete_retries_transient_gateway_response(settings: Settings) -> None:
@@ -158,3 +163,41 @@ async def test_complete_aggregates_streamed_tool_call(settings: Settings) -> Non
         }
     ]
     assert result["usage"]["total_tokens"] == 7
+
+
+async def test_deepseek_route_enables_thinking_and_uses_separate_credentials(settings: Settings) -> None:
+    body = (
+        'data: {"choices":[{"index":0,"delta":{"role":"assistant",'
+        '"reasoning_content":"private state","tool_calls":[{"index":0,"id":"call-1",'
+        '"type":"function","function":{"name":"ping","arguments":"{}"}}]},'
+        '"finish_reason":"tool_calls"}]}\n\n'
+        "data: [DONE]\n\n"
+    )
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        assert str(request.url) == "https://api.deepseek.example.test/v1/chat/completions"
+        assert request.headers["Authorization"] == "Bearer deepseek-secret"
+        payload = json.loads(request.content)
+        assert payload["model"] == "test-model"
+        assert payload["thinking"] == {"type": "enabled"}
+        assert payload["reasoning_effort"] == "max"
+        assert payload["max_tokens"] == 16_384
+        return httpx.Response(
+            200,
+            request=request,
+            headers={"Content-Type": "text/event-stream"},
+            content=body,
+        )
+
+    result = await _complete_with_handler(
+        settings,
+        handler,
+        provider="deepseek",
+        thinking_enabled=True,
+        reasoning_effort="max",
+        max_output_tokens=16_384,
+    )
+
+    message = result["choices"][0]["message"]
+    assert message["reasoning_content"] == "private state"
+    assert message["tool_calls"][0]["function"]["name"] == "ping"