openai: add v1/responses support (#13351)

Only supporting the stateless part of the API.

Doc updates to come once this is shipped.

Closes: #9659

middleware/openai.go

@@ -433,3 +433,111 @@ func ChatMiddleware() gin.HandlerFunc {
 		c.Next()
 	}
 }
+
+type ResponsesWriter struct {
+	BaseWriter
+	converter  *openai.ResponsesStreamConverter
+	model      string
+	stream     bool
+	responseID string
+	itemID     string
+}
+
+func (w *ResponsesWriter) writeEvent(eventType string, data any) error {
+	d, err := json.Marshal(data)
+	if err != nil {
+		return err
+	}
+	_, err = w.ResponseWriter.Write([]byte(fmt.Sprintf("event: %s\ndata: %s\n\n", eventType, d)))
+	if err != nil {
+		return err
+	}
+	if f, ok := w.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+	return nil
+}
+
+func (w *ResponsesWriter) writeResponse(data []byte) (int, error) {
+	var chatResponse api.ChatResponse
+	if err := json.Unmarshal(data, &chatResponse); err != nil {
+		return 0, err
+	}
+
+	if w.stream {
+		w.ResponseWriter.Header().Set("Content-Type", "text/event-stream")
+
+		events := w.converter.Process(chatResponse)
+		for _, event := range events {
+			if err := w.writeEvent(event.Event, event.Data); err != nil {
+				return 0, err
+			}
+		}
+		return len(data), nil
+	}
+
+	// Non-streaming response
+	w.ResponseWriter.Header().Set("Content-Type", "application/json")
+	response := openai.ToResponse(w.model, w.responseID, w.itemID, chatResponse)
+	return len(data), json.NewEncoder(w.ResponseWriter).Encode(response)
+}
+
+func (w *ResponsesWriter) Write(data []byte) (int, error) {
+	code := w.ResponseWriter.Status()
+	if code != http.StatusOK {
+		return w.writeError(data)
+	}
+	return w.writeResponse(data)
+}
+
+func ResponsesMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		var req openai.ResponsesRequest
+		if err := c.ShouldBindJSON(&req); err != nil {
+			c.AbortWithStatusJSON(http.StatusBadRequest, openai.NewError(http.StatusBadRequest, err.Error()))
+			return
+		}
+
+		chatReq, err := openai.FromResponsesRequest(req)
+		if err != nil {
+			c.AbortWithStatusJSON(http.StatusBadRequest, openai.NewError(http.StatusBadRequest, err.Error()))
+			return
+		}
+
+		// Check if client requested streaming (defaults to false)
+		streamRequested := req.Stream != nil && *req.Stream
+
+		// Pass streaming preference to the underlying chat request
+		chatReq.Stream = &streamRequested
+
+		var b bytes.Buffer
+		if err := json.NewEncoder(&b).Encode(chatReq); err != nil {
+			c.AbortWithStatusJSON(http.StatusInternalServerError, openai.NewError(http.StatusInternalServerError, err.Error()))
+			return
+		}
+
+		c.Request.Body = io.NopCloser(&b)
+
+		responseID := fmt.Sprintf("resp_%d", rand.Intn(999999))
+		itemID := fmt.Sprintf("msg_%d", rand.Intn(999999))
+
+		w := &ResponsesWriter{
+			BaseWriter: BaseWriter{ResponseWriter: c.Writer},
+			converter:  openai.NewResponsesStreamConverter(responseID, itemID, req.Model),
+			model:      req.Model,
+			stream:     streamRequested,
+			responseID: responseID,
+			itemID:     itemID,
+		}
+
+		// Set headers based on streaming mode
+		if streamRequested {
+			c.Writer.Header().Set("Content-Type", "text/event-stream")
+			c.Writer.Header().Set("Cache-Control", "no-cache")
+			c.Writer.Header().Set("Connection", "keep-alive")
+		}
+
+		c.Writer = w
+		c.Next()
+	}
+}

openai/openai.go

@@ -487,29 +487,9 @@ func FromChatRequest(r ChatCompletionRequest) (*api.ChatRequest, error) {
 						}
 					}
 
-					types := []string{"jpeg", "jpg", "png", "webp"}
+					img, err := decodeImageURL(url)
-					valid := false
-					// support blank mime type to match api/chat taking just unadorned base64
-					if strings.HasPrefix(url, "data:;base64,") {
-						url = strings.TrimPrefix(url, "data:;base64,")
-						valid = true
-					}
-					for _, t := range types {
-						prefix := "data:image/" + t + ";base64,"
-						if strings.HasPrefix(url, prefix) {
-							url = strings.TrimPrefix(url, prefix)
-							valid = true
-							break
-						}
-					}
-
-					if !valid {
-						return nil, errors.New("invalid image input")
-					}
-
-					img, err := base64.StdEncoding.DecodeString(url)
 					if err != nil {
-						return nil, errors.New("invalid message format")
+						return nil, err
 					}
 
 					messages = append(messages, api.Message{Role: msg.Role, Images: []api.ImageData{img}})
@@ -648,6 +628,35 @@ func nameFromToolCallID(messages []Message, toolCallID string) string {
 	return ""
 }
 
+// decodeImageURL decodes a base64 data URI into raw image bytes.
+func decodeImageURL(url string) (api.ImageData, error) {
+	types := []string{"jpeg", "jpg", "png", "webp"}
+
+	// Support blank mime type to match /api/chat's behavior of taking just unadorned base64
+	if strings.HasPrefix(url, "data:;base64,") {
+		url = strings.TrimPrefix(url, "data:;base64,")
+	} else {
+		valid := false
+		for _, t := range types {
+			prefix := "data:image/" + t + ";base64,"
+			if strings.HasPrefix(url, prefix) {
+				url = strings.TrimPrefix(url, prefix)
+				valid = true
+				break
+			}
+		}
+		if !valid {
+			return nil, errors.New("invalid image input")
+		}
+	}
+
+	img, err := base64.StdEncoding.DecodeString(url)
+	if err != nil {
+		return nil, errors.New("invalid image input")
+	}
+	return img, nil
+}
+
 // FromCompletionToolCall converts OpenAI ToolCall format to api.ToolCall
 func FromCompletionToolCall(toolCalls []ToolCall) ([]api.ToolCall, error) {
 	apiToolCalls := make([]api.ToolCall, len(toolCalls))

server/routes.go

@@ -1532,6 +1532,7 @@ func (s *Server) GenerateRoutes(rc *ollama.Registry) (http.Handler, error) {
 	r.POST("/v1/embeddings", middleware.EmbeddingsMiddleware(), s.EmbedHandler)
 	r.GET("/v1/models", middleware.ListMiddleware(), s.ListHandler)
 	r.GET("/v1/models/:model", middleware.RetrieveMiddleware(), s.ShowHandler)
+	r.POST("/v1/responses", middleware.ResponsesMiddleware(), s.ChatHandler)
 
 	if rc != nil {
 		// wrap old with new
@@ -2393,3 +2394,4 @@ func filterThinkTags(msgs []api.Message, m *Model) []api.Message {
 	}
 	return msgs
 }
+