Add ReasoningContent field for deepseek-reasoner model

examples/deepseek-completion-example/deepseek-completion-example.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/tmc/langchaingo/llms"
+	"github.com/tmc/langchaingo/llms/openai"
+)
+
+func main() {
+	// Initialize the OpenAI client with Deepseek model
+	llm, err := openai.New(
+		openai.WithModel("deepseek-reasoner"),
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	ctx := context.Background()
+
+	// Create messages for the chat
+	content := []llms.MessageContent{
+		llms.TextParts(llms.ChatMessageTypeSystem, "You are a helpful assistant that explains complex topics step by step"),
+		llms.TextParts(llms.ChatMessageTypeHuman, "Explain how quantum entanglement works and why it's important for quantum computing"),
+	}
+
+	// Generate content with streaming to see both reasoning and final answer in real-time
+	completion, err := llm.GenerateContent(
+		ctx,
+		content,
+		llms.WithMaxTokens(2000),
+		llms.WithTemperature(0.7),
+		llms.WithStreamingFunc(func(ctx context.Context, chunk []byte) error {
+			fmt.Print(string(chunk))
+			return nil
+		}),
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Access the reasoning content and final answer separately
+	if len(completion.Choices) > 0 {
+		choice := completion.Choices[0]
+		fmt.Printf("\n\nReasoning Process:\n%s\n", choice.ReasoningContent)
+		fmt.Printf("\nFinal Answer:\n%s\n", choice.Content)
+	}
+}

llms/chat_messages.go

@@ -63,6 +63,9 @@ type AIChatMessage struct {
 
 	// ToolCalls represents the model choosing to call tools.
 	ToolCalls []ToolCall `json:"tool_calls,omitempty"`
+
+	// This field is only used with the deepseek-reasoner model and represents the reasoning contents of the assistant message before the final answer.
+	ReasoningContent string `json:"reasoning_content,omitempty"`
 }
 
 func (m AIChatMessage) GetType() ChatMessageType       { return ChatMessageTypeAI }

llms/generatecontent.go

@@ -143,6 +143,9 @@ type ContentChoice struct {
 
 	// ToolCalls is a list of tool calls the model asks to invoke.
 	ToolCalls []ToolCall
+
+	// This field is only used with the deepseek-reasoner model and represents the reasoning contents of the assistant message before the final answer.
+	ReasoningContent string
 }
 
 // TextParts is a helper function to create a MessageContent with a role and a

llms/openai/internal/openaiclient/chat.go

@@ -157,6 +157,9 @@ type ChatMessage struct { //nolint:musttag
 	// ToolCallID is the ID of the tool call this message is for.
 	// Only present in tool messages.
 	ToolCallID string `json:"tool_call_id,omitempty"`
+
+	// This field is only used with the deepseek-reasoner model and represents the reasoning contents of the assistant message before the final answer.
+	ReasoningContent string `json:"reasoning_content,omitempty"`
 }
 
 func (m ChatMessage) MarshalJSON() ([]byte, error) {
@@ -181,6 +184,9 @@ func (m ChatMessage) MarshalJSON() ([]byte, error) {
 			// ToolCallID is the ID of the tool call this message is for.
 			// Only present in tool messages.
 			ToolCallID string `json:"tool_call_id,omitempty"`
+
+			// This field is only used with the deepseek-reasoner model and represents the reasoning contents of the assistant message before the final answer.
+			ReasoningContent string `json:"reasoning_content,omitempty"`
 		}(m)
 		return json.Marshal(msg)
 	}
@@ -196,6 +202,9 @@ func (m ChatMessage) MarshalJSON() ([]byte, error) {
 		// ToolCallID is the ID of the tool call this message is for.
 		// Only present in tool messages.
 		ToolCallID string `json:"tool_call_id,omitempty"`
+
+		// This field is only used with the deepseek-reasoner model and represents the reasoning contents of the assistant message before the final answer.
+		ReasoningContent string `json:"reasoning_content,omitempty"`
 	}(m)
 	return json.Marshal(msg)
 }
@@ -221,6 +230,9 @@ func (m *ChatMessage) UnmarshalJSON(data []byte) error {
 		// ToolCallID is the ID of the tool call this message is for.
 		// Only present in tool messages.
 		ToolCallID string `json:"tool_call_id,omitempty"`
+
+		// This field is only used with the deepseek-reasoner model and represents the reasoning contents of the assistant message before the final answer.
+		ReasoningContent string `json:"reasoning_content,omitempty"`
 	}{}
 	err := json.Unmarshal(data, &msg)
 	if err != nil {
@@ -322,6 +334,8 @@ type StreamedChatResponsePayload struct {
 			FunctionCall *FunctionCall `json:"function_call,omitempty"`
 			// ToolCalls is a list of tools that were called in the message.
 			ToolCalls []*ToolCall `json:"tool_calls,omitempty"`
+			// This field is only used with the deepseek-reasoner model and represents the reasoning contents of the assistant message before the final answer.
+			ReasoningContent string `json:"reasoning_content,omitempty"`
 		} `json:"delta,omitempty"`
 		FinishReason FinishReason `json:"finish_reason,omitempty"`
 	} `json:"choices,omitempty"`
@@ -481,6 +495,7 @@ func combineStreamingChatResponse(
 		chunk := []byte(choice.Delta.Content)
 		response.Choices[0].Message.Content += choice.Delta.Content
 		response.Choices[0].FinishReason = choice.FinishReason
+		response.Choices[0].Message.ReasoningContent = choice.Delta.ReasoningContent
 
 		if choice.Delta.FunctionCall != nil {
 			chunk = updateFunctionCall(response.Choices[0].Message, choice.Delta.FunctionCall)

llms/openai/internal/openaiclient/chat_test.go

@@ -33,6 +33,29 @@ func TestParseStreamingChatResponse_FinishReason(t *testing.T) {
 	assert.Equal(t, FinishReason("stop"), resp.Choices[0].FinishReason)
 }
 
+func TestParseStreamingChatResponse_ReasoningContent(t *testing.T) {
+	t.Parallel()
+	mockBody := `data: {"choices":[{"index":0,"delta":{"role":"assistant","content":"final answer","reasoning_content":"step-by-step reasoning"},"finish_reason":"stop"}]}`
+	r := &http.Response{
+		StatusCode: http.StatusOK,
+		Body:       io.NopCloser(bytes.NewBufferString(mockBody)),
+	}
+
+	req := &ChatRequest{
+		StreamingFunc: func(_ context.Context, _ []byte) error {
+			return nil
+		},
+	}
+
+	resp, err := parseStreamingChatResponse(context.Background(), r, req)
+
+	require.NoError(t, err)
+	assert.NotNil(t, resp)
+	assert.Equal(t, "final answer", resp.Choices[0].Message.Content)
+	assert.Equal(t, "step-by-step reasoning", resp.Choices[0].Message.ReasoningContent)
+	assert.Equal(t, FinishReason("stop"), resp.Choices[0].FinishReason)
+}
+
 func TestChatMessage_MarshalUnmarshal(t *testing.T) {
 	t.Parallel()
 	msg := ChatMessage{
@@ -52,3 +75,20 @@ func TestChatMessage_MarshalUnmarshal(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, msg, msg2)
 }
+
+func TestChatMessage_MarshalUnmarshal_WithReasoning(t *testing.T) {
+	t.Parallel()
+	msg := ChatMessage{
+		Role:             "assistant",
+		Content:          "final answer",
+		ReasoningContent: "step-by-step reasoning",
+	}
+	text, err := json.Marshal(msg)
+	require.NoError(t, err)
+	require.Equal(t, `{"role":"assistant","content":"final answer","reasoning_content":"step-by-step reasoning"}`, string(text))
+
+	var msg2 ChatMessage
+	err = json.Unmarshal(text, &msg2)
+	require.NoError(t, err)
+	require.Equal(t, msg, msg2)
+}