Omit unset optional request parameters

engine_test.go

@@ -360,14 +360,14 @@ func TestEngineExecutionSettingPrecedence(t *testing.T) {
 		wantPresence promptkit.ExecutionTargetPresence
 	}{
 		{
-			name:    "framework defaults fill zero-valued profile settings",
+			name:    "unspecified provider controls retain framework timeout",
 			profile: defaultsProfile,
 			want: promptkit.ExecutionTarget{
 				Endpoint:        defaultsProfile.endpoint,
 				Model:           defaultsProfile.model,
 				Temperature:     0,
 				MaxTokens:       0,
-				TopP:            1,
+				TopP:            0,
 				TimeoutSeconds:  600,
 				ServiceTier:     defaultsProfile.serviceTier,
 				ReasoningEffort: defaultsProfile.reasoningEffort,