Add /v1/completions endpoint with OpenAI compatibility

- Implemented `/v1/completions` endpoint mirroring OpenAI's completions API specification.
- Added conversion functions to translate between completions and chat completions formats.
- Introduced streaming and non-streaming response handling for completions requests.
- Updated `server.go` to register the new endpoint and include it in the API's metadata.

internal/api/handlers/openai/openai_handlers.go

@@ -8,6 +8,7 @@ package openai
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"time"
@@ -19,6 +20,7 @@ import (
 	"github.com/luispater/CLIProxyAPI/internal/registry"
 	log "github.com/sirupsen/logrus"
 	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
 )
 
 // OpenAIAPIHandler contains the handlers for OpenAI API endpoints.
@@ -92,6 +94,276 @@ func (h *OpenAIAPIHandler) ChatCompletions(c *gin.Context) {
 
 }
 
+// Completions handles the /v1/completions endpoint.
+// It determines whether the request is for a streaming or non-streaming response
+// and calls the appropriate handler based on the model provider.
+// This endpoint follows the OpenAI completions API specification.
+//
+// Parameters:
+//   - c: The Gin context containing the HTTP request and response
+func (h *OpenAIAPIHandler) Completions(c *gin.Context) {
+	rawJSON, err := c.GetRawData()
+	// If data retrieval fails, return a 400 Bad Request error.
+	if err != nil {
+		c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
+			Error: handlers.ErrorDetail{
+				Message: fmt.Sprintf("Invalid request: %v", err),
+				Type:    "invalid_request_error",
+			},
+		})
+		return
+	}
+
+	// Check if the client requested a streaming response.
+	streamResult := gjson.GetBytes(rawJSON, "stream")
+	if streamResult.Type == gjson.True {
+		h.handleCompletionsStreamingResponse(c, rawJSON)
+	} else {
+		h.handleCompletionsNonStreamingResponse(c, rawJSON)
+	}
+
+}
+
+// convertCompletionsRequestToChatCompletions converts OpenAI completions API request to chat completions format.
+// This allows the completions endpoint to use the existing chat completions infrastructure.
+//
+// Parameters:
+//   - rawJSON: The raw JSON bytes of the completions request
+//
+// Returns:
+//   - []byte: The converted chat completions request
+func convertCompletionsRequestToChatCompletions(rawJSON []byte) []byte {
+	root := gjson.ParseBytes(rawJSON)
+
+	// Extract prompt from completions request
+	prompt := root.Get("prompt").String()
+	if prompt == "" {
+		prompt = "Complete this:"
+	}
+
+	// Create chat completions structure
+	out := `{"model":"","messages":[{"role":"user","content":""}]}`
+
+	// Set model
+	if model := root.Get("model"); model.Exists() {
+		out, _ = sjson.Set(out, "model", model.String())
+	}
+
+	// Set the prompt as user message content
+	out, _ = sjson.Set(out, "messages.0.content", prompt)
+
+	// Copy other parameters from completions to chat completions
+	if maxTokens := root.Get("max_tokens"); maxTokens.Exists() {
+		out, _ = sjson.Set(out, "max_tokens", maxTokens.Int())
+	}
+
+	if temperature := root.Get("temperature"); temperature.Exists() {
+		out, _ = sjson.Set(out, "temperature", temperature.Float())
+	}
+
+	if topP := root.Get("top_p"); topP.Exists() {
+		out, _ = sjson.Set(out, "top_p", topP.Float())
+	}
+
+	if frequencyPenalty := root.Get("frequency_penalty"); frequencyPenalty.Exists() {
+		out, _ = sjson.Set(out, "frequency_penalty", frequencyPenalty.Float())
+	}
+
+	if presencePenalty := root.Get("presence_penalty"); presencePenalty.Exists() {
+		out, _ = sjson.Set(out, "presence_penalty", presencePenalty.Float())
+	}
+
+	if stop := root.Get("stop"); stop.Exists() {
+		out, _ = sjson.SetRaw(out, "stop", stop.Raw)
+	}
+
+	if stream := root.Get("stream"); stream.Exists() {
+		out, _ = sjson.Set(out, "stream", stream.Bool())
+	}
+
+	if logprobs := root.Get("logprobs"); logprobs.Exists() {
+		out, _ = sjson.Set(out, "logprobs", logprobs.Bool())
+	}
+
+	if topLogprobs := root.Get("top_logprobs"); topLogprobs.Exists() {
+		out, _ = sjson.Set(out, "top_logprobs", topLogprobs.Int())
+	}
+
+	if echo := root.Get("echo"); echo.Exists() {
+		out, _ = sjson.Set(out, "echo", echo.Bool())
+	}
+
+	return []byte(out)
+}
+
+// convertChatCompletionsResponseToCompletions converts chat completions API response back to completions format.
+// This ensures the completions endpoint returns data in the expected format.
+//
+// Parameters:
+//   - rawJSON: The raw JSON bytes of the chat completions response
+//
+// Returns:
+//   - []byte: The converted completions response
+func convertChatCompletionsResponseToCompletions(rawJSON []byte) []byte {
+	root := gjson.ParseBytes(rawJSON)
+
+	// Base completions response structure
+	out := `{"id":"","object":"text_completion","created":0,"model":"","choices":[]}`
+
+	// Copy basic fields
+	if id := root.Get("id"); id.Exists() {
+		out, _ = sjson.Set(out, "id", id.String())
+	}
+
+	if created := root.Get("created"); created.Exists() {
+		out, _ = sjson.Set(out, "created", created.Int())
+	}
+
+	if model := root.Get("model"); model.Exists() {
+		out, _ = sjson.Set(out, "model", model.String())
+	}
+
+	if usage := root.Get("usage"); usage.Exists() {
+		out, _ = sjson.SetRaw(out, "usage", usage.Raw)
+	}
+
+	// Convert choices from chat completions to completions format
+	var choices []interface{}
+	if chatChoices := root.Get("choices"); chatChoices.Exists() && chatChoices.IsArray() {
+		chatChoices.ForEach(func(_, choice gjson.Result) bool {
+			completionsChoice := map[string]interface{}{
+				"index": choice.Get("index").Int(),
+			}
+
+			// Extract text content from message.content
+			if message := choice.Get("message"); message.Exists() {
+				if content := message.Get("content"); content.Exists() {
+					completionsChoice["text"] = content.String()
+				}
+			} else if delta := choice.Get("delta"); delta.Exists() {
+				// For streaming responses, use delta.content
+				if content := delta.Get("content"); content.Exists() {
+					completionsChoice["text"] = content.String()
+				}
+			}
+
+			// Copy finish_reason
+			if finishReason := choice.Get("finish_reason"); finishReason.Exists() {
+				completionsChoice["finish_reason"] = finishReason.String()
+			}
+
+			// Copy logprobs if present
+			if logprobs := choice.Get("logprobs"); logprobs.Exists() {
+				completionsChoice["logprobs"] = logprobs.Value()
+			}
+
+			choices = append(choices, completionsChoice)
+			return true
+		})
+	}
+
+	if len(choices) > 0 {
+		choicesJSON, _ := json.Marshal(choices)
+		out, _ = sjson.SetRaw(out, "choices", string(choicesJSON))
+	}
+
+	return []byte(out)
+}
+
+// convertChatCompletionsStreamChunkToCompletions converts a streaming chat completions chunk to completions format.
+// This handles the real-time conversion of streaming response chunks and filters out empty text responses.
+//
+// Parameters:
+//   - chunkData: The raw JSON bytes of a single chat completions stream chunk
+//
+// Returns:
+//   - []byte: The converted completions stream chunk, or nil if should be filtered out
+func convertChatCompletionsStreamChunkToCompletions(chunkData []byte) []byte {
+	root := gjson.ParseBytes(chunkData)
+
+	// Check if this chunk has any meaningful content
+	hasContent := false
+	if chatChoices := root.Get("choices"); chatChoices.Exists() && chatChoices.IsArray() {
+		chatChoices.ForEach(func(_, choice gjson.Result) bool {
+			// Check if delta has content or finish_reason
+			if delta := choice.Get("delta"); delta.Exists() {
+				if content := delta.Get("content"); content.Exists() && content.String() != "" {
+					hasContent = true
+					return false // Break out of forEach
+				}
+			}
+			// Also check for finish_reason to ensure we don't skip final chunks
+			if finishReason := choice.Get("finish_reason"); finishReason.Exists() && finishReason.String() != "" && finishReason.String() != "null" {
+				hasContent = true
+				return false // Break out of forEach
+			}
+			return true
+		})
+	}
+
+	// If no meaningful content, return nil to indicate this chunk should be skipped
+	if !hasContent {
+		return nil
+	}
+
+	// Base completions stream response structure
+	out := `{"id":"","object":"text_completion","created":0,"model":"","choices":[]}`
+
+	// Copy basic fields
+	if id := root.Get("id"); id.Exists() {
+		out, _ = sjson.Set(out, "id", id.String())
+	}
+
+	if created := root.Get("created"); created.Exists() {
+		out, _ = sjson.Set(out, "created", created.Int())
+	}
+
+	if model := root.Get("model"); model.Exists() {
+		out, _ = sjson.Set(out, "model", model.String())
+	}
+
+	// Convert choices from chat completions delta to completions format
+	var choices []interface{}
+	if chatChoices := root.Get("choices"); chatChoices.Exists() && chatChoices.IsArray() {
+		chatChoices.ForEach(func(_, choice gjson.Result) bool {
+			completionsChoice := map[string]interface{}{
+				"index": choice.Get("index").Int(),
+			}
+
+			// Extract text content from delta.content
+			if delta := choice.Get("delta"); delta.Exists() {
+				if content := delta.Get("content"); content.Exists() && content.String() != "" {
+					completionsChoice["text"] = content.String()
+				} else {
+					completionsChoice["text"] = ""
+				}
+			} else {
+				completionsChoice["text"] = ""
+			}
+
+			// Copy finish_reason
+			if finishReason := choice.Get("finish_reason"); finishReason.Exists() && finishReason.String() != "null" {
+				completionsChoice["finish_reason"] = finishReason.String()
+			}
+
+			// Copy logprobs if present
+			if logprobs := choice.Get("logprobs"); logprobs.Exists() {
+				completionsChoice["logprobs"] = logprobs.Value()
+			}
+
+			choices = append(choices, completionsChoice)
+			return true
+		})
+	}
+
+	if len(choices) > 0 {
+		choicesJSON, _ := json.Marshal(choices)
+		out, _ = sjson.SetRaw(out, "choices", string(choicesJSON))
+	}
+
+	return []byte(out)
+}
+
 // handleNonStreamingResponse handles non-streaming chat completion responses
 // for Gemini models. It selects a client from the pool, sends the request, and
 // aggregates the response before sending it back to the client in OpenAI format.
@@ -251,3 +523,177 @@ outLoop:
 		}
 	}
 }
+
+// handleCompletionsNonStreamingResponse handles non-streaming completions responses.
+// It converts completions request to chat completions format, sends to backend,
+// then converts the response back to completions format before sending to client.
+//
+// Parameters:
+//   - c: The Gin context containing the HTTP request and response
+//   - rawJSON: The raw JSON bytes of the OpenAI-compatible completions request
+func (h *OpenAIAPIHandler) handleCompletionsNonStreamingResponse(c *gin.Context, rawJSON []byte) {
+	c.Header("Content-Type", "application/json")
+
+	// Convert completions request to chat completions format
+	chatCompletionsJSON := convertCompletionsRequestToChatCompletions(rawJSON)
+
+	modelName := gjson.GetBytes(chatCompletionsJSON, "model").String()
+	cliCtx, cliCancel := h.GetContextWithCancel(h, c, context.Background())
+
+	var cliClient interfaces.Client
+	defer func() {
+		if cliClient != nil {
+			cliClient.GetRequestMutex().Unlock()
+		}
+	}()
+
+	retryCount := 0
+	for retryCount <= h.Cfg.RequestRetry {
+		var errorResponse *interfaces.ErrorMessage
+		cliClient, errorResponse = h.GetClient(modelName)
+		if errorResponse != nil {
+			c.Status(errorResponse.StatusCode)
+			_, _ = fmt.Fprint(c.Writer, errorResponse.Error.Error())
+			cliCancel()
+			return
+		}
+
+		// Send the converted chat completions request
+		resp, err := cliClient.SendRawMessage(cliCtx, modelName, chatCompletionsJSON, "")
+		if err != nil {
+			switch err.StatusCode {
+			case 429:
+				if h.Cfg.QuotaExceeded.SwitchProject {
+					log.Debugf("quota exceeded, switch client")
+					continue // Restart the client selection process
+				}
+			case 403, 408, 500, 502, 503, 504:
+				log.Debugf("http status code %d, switch client", err.StatusCode)
+				retryCount++
+				continue
+			default:
+				// Forward other errors directly to the client
+				c.Status(err.StatusCode)
+				_, _ = c.Writer.Write([]byte(err.Error.Error()))
+				cliCancel(err.Error)
+			}
+			break
+		} else {
+			// Convert chat completions response back to completions format
+			completionsResp := convertChatCompletionsResponseToCompletions(resp)
+			_, _ = c.Writer.Write(completionsResp)
+			cliCancel(completionsResp)
+			break
+		}
+	}
+}
+
+// handleCompletionsStreamingResponse handles streaming completions responses.
+// It converts completions request to chat completions format, streams from backend,
+// then converts each response chunk back to completions format before sending to client.
+//
+// Parameters:
+//   - c: The Gin context containing the HTTP request and response
+//   - rawJSON: The raw JSON bytes of the OpenAI-compatible completions request
+func (h *OpenAIAPIHandler) handleCompletionsStreamingResponse(c *gin.Context, rawJSON []byte) {
+	c.Header("Content-Type", "text/event-stream")
+	c.Header("Cache-Control", "no-cache")
+	c.Header("Connection", "keep-alive")
+	c.Header("Access-Control-Allow-Origin", "*")
+
+	// Get the http.Flusher interface to manually flush the response.
+	flusher, ok := c.Writer.(http.Flusher)
+	if !ok {
+		c.JSON(http.StatusInternalServerError, handlers.ErrorResponse{
+			Error: handlers.ErrorDetail{
+				Message: "Streaming not supported",
+				Type:    "server_error",
+			},
+		})
+		return
+	}
+
+	// Convert completions request to chat completions format
+	chatCompletionsJSON := convertCompletionsRequestToChatCompletions(rawJSON)
+
+	modelName := gjson.GetBytes(chatCompletionsJSON, "model").String()
+	cliCtx, cliCancel := h.GetContextWithCancel(h, c, context.Background())
+
+	var cliClient interfaces.Client
+	defer func() {
+		// Ensure the client's mutex is unlocked on function exit.
+		if cliClient != nil {
+			cliClient.GetRequestMutex().Unlock()
+		}
+	}()
+
+	retryCount := 0
+outLoop:
+	for retryCount <= h.Cfg.RequestRetry {
+		var errorResponse *interfaces.ErrorMessage
+		cliClient, errorResponse = h.GetClient(modelName)
+		if errorResponse != nil {
+			c.Status(errorResponse.StatusCode)
+			_, _ = fmt.Fprint(c.Writer, errorResponse.Error.Error())
+			flusher.Flush()
+			cliCancel()
+			return
+		}
+
+		// Send the converted chat completions request and receive response chunks
+		respChan, errChan := cliClient.SendRawMessageStream(cliCtx, modelName, chatCompletionsJSON, "")
+
+		for {
+			select {
+			// Handle client disconnection.
+			case <-c.Request.Context().Done():
+				if c.Request.Context().Err().Error() == "context canceled" {
+					log.Debugf("client disconnected: %v", c.Request.Context().Err())
+					cliCancel() // Cancel the backend request.
+					return
+				}
+			// Process incoming response chunks.
+			case chunk, okStream := <-respChan:
+				if !okStream {
+					// Stream is closed, send the final [DONE] message.
+					_, _ = fmt.Fprintf(c.Writer, "data: [DONE]\n\n")
+					flusher.Flush()
+					cliCancel()
+					return
+				}
+
+				// Convert chat completions chunk to completions chunk format
+				completionsChunk := convertChatCompletionsStreamChunkToCompletions(chunk)
+				// Skip this chunk if it has no meaningful content (empty text)
+				if completionsChunk != nil {
+					_, _ = fmt.Fprintf(c.Writer, "data: %s\n\n", string(completionsChunk))
+					flusher.Flush()
+				}
+			// Handle errors from the backend.
+			case err, okError := <-errChan:
+				if okError {
+					switch err.StatusCode {
+					case 429:
+						if h.Cfg.QuotaExceeded.SwitchProject {
+							log.Debugf("quota exceeded, switch client")
+							continue outLoop // Restart the client selection process
+						}
+					case 403, 408, 500, 502, 503, 504:
+						log.Debugf("http status code %d, switch client", err.StatusCode)
+						retryCount++
+						continue outLoop
+					default:
+						// Forward other errors directly to the client
+						c.Status(err.StatusCode)
+						_, _ = fmt.Fprint(c.Writer, err.Error.Error())
+						flusher.Flush()
+						cliCancel(err.Error)
+					}
+					return
+				}
+			// Send a keep-alive signal to the client.
+			case <-time.After(500 * time.Millisecond):
+			}
+		}
+	}
+}

internal/api/server.go

@@ -104,6 +104,7 @@ func (s *Server) setupRoutes() {
 	{
 		v1.GET("/models", s.unifiedModelsHandler(openaiHandlers, claudeCodeHandlers))
 		v1.POST("/chat/completions", openaiHandlers.ChatCompletions)
+		v1.POST("/completions", openaiHandlers.Completions)
 		v1.POST("/messages", claudeCodeHandlers.ClaudeMessages)
 	}
 
@@ -123,6 +124,7 @@ func (s *Server) setupRoutes() {
 			"version": "1.0.0",
 			"endpoints": []string{
 				"POST /v1/chat/completions",
+				"POST /v1/completions",
 				"GET /v1/models",
 			},
 		})
@@ -140,10 +142,10 @@ func (s *Server) unifiedModelsHandler(openaiHandler *openai.OpenAIAPIHandler, cl
 
 		// Route to Claude handler if User-Agent starts with "claude-cli"
 		if strings.HasPrefix(userAgent, "claude-cli") {
-			log.Debugf("Routing /v1/models to Claude handler for User-Agent: %s", userAgent)
+			// log.Debugf("Routing /v1/models to Claude handler for User-Agent: %s", userAgent)
 			claudeHandler.ClaudeModels(c)
 		} else {
-			log.Debugf("Routing /v1/models to OpenAI handler for User-Agent: %s", userAgent)
+			// log.Debugf("Routing /v1/models to OpenAI handler for User-Agent: %s", userAgent)
 			openaiHandler.OpenAIModels(c)
 		}
 	}

internal/client/qwen_client.go

@@ -329,6 +329,11 @@ func (c *QwenClient) APIRequest(ctx context.Context, modelName, endpoint string,
 		}
 	}
 
+	toolsResult := gjson.GetBytes(jsonBody, "tools")
+	if toolsResult.IsArray() && len(toolsResult.Array()) == 0 {
+		jsonBody, _ = sjson.DeleteBytes(jsonBody, "tools")
+	}
+
 	streamResult := gjson.GetBytes(jsonBody, "stream")
 	if streamResult.Exists() && streamResult.Type == gjson.True {
 		jsonBody, _ = sjson.SetBytes(jsonBody, "stream_options.include_usage", true)

internal/registry/model_registry.go

@@ -185,7 +185,7 @@ func (r *ModelRegistry) ClearModelQuotaExceeded(clientID, modelID string) {
 
 	if registration, exists := r.models[modelID]; exists {
 		delete(registration.QuotaExceededClients, clientID)
-		log.Debugf("Cleared quota exceeded status for model %s and client %s", modelID, clientID)
+		// log.Debugf("Cleared quota exceeded status for model %s and client %s", modelID, clientID)
 	}
 }
 

internal/translator/claude/openai/claude_openai_request.go

@@ -244,7 +244,7 @@ func ConvertOpenAIRequestToClaude(modelName string, rawJSON []byte, stream bool)
 	}
 
 	// Tools mapping: OpenAI tools -> Claude Code tools
-	if tools := root.Get("tools"); tools.Exists() && tools.IsArray() {
+	if tools := root.Get("tools"); tools.Exists() && tools.IsArray() && len(tools.Array()) > 0 {
 		var anthropicTools []interface{}
 		tools.ForEach(func(_, tool gjson.Result) bool {
 			if tool.Get("type").String() == "function" {

internal/translator/codex/openai/codex_openai_request.go

@@ -231,7 +231,7 @@ func ConvertOpenAIRequestToCodex(modelName string, rawJSON []byte, stream bool)
 
 	// Map tools (flatten function fields)
 	tools := gjson.GetBytes(rawJSON, "tools")
-	if tools.IsArray() {
+	if tools.IsArray() && len(tools.Array()) > 0 {
 		out, _ = sjson.SetRaw(out, "tools", `[]`)
 		arr := tools.Array()
 		for i := 0; i < len(arr); i++ {

internal/translator/gemini-cli/openai/cli_openai_request.go

@@ -215,7 +215,7 @@ func ConvertOpenAIRequestToGeminiCLI(modelName string, rawJSON []byte, _ bool) [
 
 	// tools -> request.tools[0].functionDeclarations
 	tools := gjson.GetBytes(rawJSON, "tools")
-	if tools.IsArray() {
+	if tools.IsArray() && len(tools.Array()) > 0 {
 		out, _ = sjson.SetRawBytes(out, "request.tools", []byte(`[{"functionDeclarations":[]}]`))
 		fdPath := "request.tools.0.functionDeclarations"
 		for _, t := range tools.Array() {

internal/translator/gemini/openai/gemini_openai_request.go

@@ -215,7 +215,7 @@ func ConvertOpenAIRequestToGemini(modelName string, rawJSON []byte, _ bool) []by
 
 	// tools -> tools[0].functionDeclarations
 	tools := gjson.GetBytes(rawJSON, "tools")
-	if tools.IsArray() {
+	if tools.IsArray() && len(tools.Array()) > 0 {
 		out, _ = sjson.SetRawBytes(out, "tools", []byte(`[{"functionDeclarations":[]}]`))
 		fdPath := "tools.0.functionDeclarations"
 		for _, t := range tools.Array() {