fix: simplify identical source/target loop in payload builder

examples/experimental/litellm/src/switchyard_litellm/client.py

@@ -236,10 +236,10 @@ def _payload(request: Mapping[str, object], model: str) -> dict[str, Any]:
     tool_choice = _tool_choice(request)
     if tool_choice is not None:
         payload["tool_choice"] = tool_choice
-    for source, target in (("temperature", "temperature"), ("top_p", "top_p")):
-        value = sampling.get(source)
+    for key in ("temperature", "top_p"):
+        value = sampling.get(key)
         if value is not None:
-            payload[target] = value
+            payload[key] = value
     max_tokens = output.get("max_output_tokens")
     if max_tokens is not None:
         payload["max_completion_tokens"] = max_tokens

examples/experimental/litellm/tests/test_payload_sampling.py

@@ -0,0 +1,11 @@
+from switchyard_litellm.client import _payload
+
+
+def test_sampling_temperature_and_top_p_forwarded() -> None:
+    request = {
+        "messages": [{"role": "user", "content": [{"type": "text", "text": "hi"}]}],
+        "sampling": {"temperature": 0.5, "top_p": 0.9},
+    }
+    payload = _payload(request, "strong")
+    assert payload["temperature"] == 0.5
+    assert payload["top_p"] == 0.9