fix(relay): preserve presence/frequency penalty in Responses conversion (#6654)

relaykit/dto/openai_request.go

@@ -867,6 +867,11 @@ type OpenAIResponsesRequest struct {
 	Metadata           json.RawMessage `json:"metadata,omitempty"`
 	Moderation         json.RawMessage `json:"moderation,omitempty"`
 	ParallelToolCalls  json.RawMessage `json:"parallel_tool_calls,omitempty"`
+	// FrequencyPenalty/PresencePenalty are not part of the official OpenAI
+	// Responses API; they are forwarded verbatim for OpenAI-compatible upstreams
+	// (e.g. vLLM) that accept them.
+	FrequencyPenalty   json.RawMessage `json:"frequency_penalty,omitempty"`
+	PresencePenalty    json.RawMessage `json:"presence_penalty,omitempty"`
 	PreviousResponseID string          `json:"previous_response_id,omitempty"`
 	Reasoning          *Reasoning      `json:"reasoning,omitempty"`
 	// ServiceTier specifies upstream service level and may affect billing.

relaykit/dto/openai_request_zero_value_test.go

@@ -123,7 +123,9 @@ func TestOpenAIResponsesRequestPreserveExplicitZeroValues(t *testing.T) {
 		"max_output_tokens":0,
 		"max_tool_calls":0,
 		"stream":false,
-		"top_p":0
+		"top_p":0,
+		"frequency_penalty":0,
+		"presence_penalty":0
 	}`)
 
 	var req OpenAIResponsesRequest
@@ -137,6 +139,8 @@ func TestOpenAIResponsesRequestPreserveExplicitZeroValues(t *testing.T) {
 	require.True(t, gjson.GetBytes(encoded, "max_tool_calls").Exists())
 	require.True(t, gjson.GetBytes(encoded, "stream").Exists())
 	require.True(t, gjson.GetBytes(encoded, "top_p").Exists())
+	require.True(t, gjson.GetBytes(encoded, "frequency_penalty").Exists())
+	require.True(t, gjson.GetBytes(encoded, "presence_penalty").Exists())
 }
 
 func TestOpenAIResponsesRequestPreserveQwenThinkingBudget(t *testing.T) {

relaykit/relayconvert/internal/oai_chat/to_oai_responses_req.go

@@ -372,6 +372,14 @@ func ChatCompletionsRequestToResponsesRequest(req *dto.GeneralOpenAIRequest) (*d
 		topP = kitutil.GetPointer(lo.FromPtr(req.TopP))
 	}
 
+	var frequencyPenaltyRaw, presencePenaltyRaw json.RawMessage
+	if req.FrequencyPenalty != nil {
+		frequencyPenaltyRaw, _ = kitutil.Marshal(req.FrequencyPenalty)
+	}
+	if req.PresencePenalty != nil {
+		presencePenaltyRaw, _ = kitutil.Marshal(req.PresencePenalty)
+	}
+
 	out := &dto.OpenAIResponsesRequest{
 		Model:             req.Model,
 		Input:             inputRaw,
@@ -382,6 +390,8 @@ func ChatCompletionsRequestToResponsesRequest(req *dto.GeneralOpenAIRequest) (*d
 		ToolChoice:        toolChoiceRaw,
 		Tools:             toolsRaw,
 		TopP:              topP,
+		FrequencyPenalty:  frequencyPenaltyRaw,
+		PresencePenalty:   presencePenaltyRaw,
 		User:              req.User,
 		ParallelToolCalls: parallelToolCallsRaw,
 		Store:             req.Store,

relaykit/relayconvert/internal/oai_chat/to_oai_responses_req_test.go

@@ -84,6 +84,51 @@ func TestChatCompletionsRequestToResponsesRequestRejectsMultipleChoices(t *testi
 	assert.Contains(t, err.Error(), "n>1")
 }
 
+func TestChatCompletionsRequestToResponsesRequestPreservesPenalties(t *testing.T) {
+	tests := []struct {
+		name          string
+		frequency     *float64
+		frequencyWant json.RawMessage
+		presence      *float64
+		presenceWant  json.RawMessage
+	}{
+		{
+			name:          "positive values",
+			frequency:     lo.ToPtr(0.5),
+			frequencyWant: json.RawMessage(`0.5`),
+			presence:      lo.ToPtr(1.5),
+			presenceWant:  json.RawMessage(`1.5`),
+		},
+		{
+			name:          "explicit zero values",
+			frequency:     lo.ToPtr(0.0),
+			frequencyWant: json.RawMessage(`0`),
+			presence:      lo.ToPtr(0.0),
+			presenceWant:  json.RawMessage(`0`),
+		},
+		{
+			name:      "unset stays nil",
+			frequency: nil,
+			presence:  nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := ChatCompletionsRequestToResponsesRequest(&dto.GeneralOpenAIRequest{
+				Model:            "gpt-test",
+				Messages:         []dto.Message{{Role: "user", Content: "hello"}},
+				FrequencyPenalty: tt.frequency,
+				PresencePenalty:  tt.presence,
+			})
+			require.NoError(t, err)
+
+			assert.Equal(t, tt.frequencyWant, got.FrequencyPenalty)
+			assert.Equal(t, tt.presenceWant, got.PresencePenalty)
+		})
+	}
+}
+
 func assistantMessageWithTool(content string, id string, name string, args string) dto.Message {
 	msg := dto.Message{Role: "assistant", Content: content}
 	msg.SetToolCalls([]dto.ToolCallRequest{

relaykit/relayconvert/internal/oai_responses/to_oai_chat_req.go

@@ -76,6 +76,15 @@ func ResponsesRequestToChatCompletionsRequest(req *dto.OpenAIResponsesRequest) (
 		ThinkingBudget:       req.ThinkingBudget,
 	}
 
+	out.FrequencyPenalty, err = responsesRawFloat(req.FrequencyPenalty)
+	if err != nil {
+		return nil, fmt.Errorf("invalid frequency_penalty: %w", err)
+	}
+	out.PresencePenalty, err = responsesRawFloat(req.PresencePenalty)
+	if err != nil {
+		return nil, fmt.Errorf("invalid presence_penalty: %w", err)
+	}
+
 	if req.Reasoning != nil {
 		out.ReasoningEffort = req.Reasoning.Effort
 	}
@@ -527,6 +536,17 @@ func responseToolOutputToChatContent(value any) any {
 	}
 }
 
+func responsesRawFloat(raw json.RawMessage) (*float64, error) {
+	if !rawJSONPresent(raw) {
+		return nil, nil
+	}
+	var value float64
+	if err := kitutil.Unmarshal(raw, &value); err != nil {
+		return nil, err
+	}
+	return &value, nil
+}
+
 func responsesJSONString(raw json.RawMessage) (string, error) {
 	if kitutil.GetJsonType(raw) != "string" {
 		return string(raw), nil

relaykit/relayconvert/internal/oai_responses/to_oai_chat_req_test.go

@@ -295,6 +295,61 @@ func TestResponsesRequestToChatCompletionsRequestRejectsStatefulFields(t *testin
 	}
 }
 
+func TestResponsesRequestToChatCompletionsRequestPreservesPenalties(t *testing.T) {
+	tests := []struct {
+		name          string
+		frequencyRaw  json.RawMessage
+		frequencyWant *float64
+		presenceRaw   json.RawMessage
+		presenceWant  *float64
+	}{
+		{
+			name:          "positive values",
+			frequencyRaw:  json.RawMessage(`0.5`),
+			frequencyWant: lo.ToPtr(0.5),
+			presenceRaw:   json.RawMessage(`1.5`),
+			presenceWant:  lo.ToPtr(1.5),
+		},
+		{
+			name:          "explicit zero values",
+			frequencyRaw:  json.RawMessage(`0.0`),
+			frequencyWant: lo.ToPtr(0.0),
+			presenceRaw:   json.RawMessage(`0.0`),
+			presenceWant:  lo.ToPtr(0.0),
+		},
+		{
+			name:         "unset stays nil",
+			frequencyRaw: nil,
+			presenceRaw:  nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := ResponsesRequestToChatCompletionsRequest(&dto.OpenAIResponsesRequest{
+				Model:            "gpt-test",
+				Input:            mustRawMessage(t, "hello"),
+				FrequencyPenalty: tt.frequencyRaw,
+				PresencePenalty:  tt.presenceRaw,
+			})
+			require.NoError(t, err)
+
+			assert.Equal(t, tt.frequencyWant, got.FrequencyPenalty)
+			assert.Equal(t, tt.presenceWant, got.PresencePenalty)
+		})
+	}
+}
+
+func TestResponsesRequestToChatCompletionsRequestRejectsMalformedPenalty(t *testing.T) {
+	_, err := ResponsesRequestToChatCompletionsRequest(&dto.OpenAIResponsesRequest{
+		Model:            "gpt-test",
+		Input:            mustRawMessage(t, "hello"),
+		FrequencyPenalty: json.RawMessage(`"not-a-number"`),
+	})
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "frequency_penalty")
+}
+
 func mustRawMessage(t *testing.T, value any) []byte {
 	t.Helper()
 	raw, err := kitutil.Marshal(value)