refactor: replace json.Marshal and json.Unmarshal with sjson and gjson

Optimized the handling of JSON serialization and deserialization by replacing redundant `json.Marshal` and `json.Unmarshal` calls with `sjson` and `gjson`. Introduced a `marshalJSONValue` utility for compact JSON encoding, improving performance and code simplicity. Removed unused `encoding/json` imports.

internal/translator/claude/openai/chat-completions/claude_openai_request.go

@@ -10,7 +10,6 @@ import (
 	"crypto/rand"
 	"crypto/sha256"
 	"encoding/hex"
-	"encoding/json"
 	"fmt"
 	"math/big"
 	"strings"
@@ -137,9 +136,6 @@ func ConvertOpenAIRequestToClaude(modelName string, inputRawJSON []byte, stream
 	out, _ = sjson.Set(out, "stream", stream)
 
 	// Process messages and transform them to Claude Code format
-	var anthropicMessages []interface{}
-	var toolCallIDs []string // Track tool call IDs for matching with tool results
-
 	if messages := root.Get("messages"); messages.Exists() && messages.IsArray() {
 		messages.ForEach(func(_, message gjson.Result) bool {
 			role := message.Get("role").String()
@@ -152,33 +148,23 @@ func ConvertOpenAIRequestToClaude(modelName string, inputRawJSON []byte, stream
 					role = "user"
 				}
 
-				msg := map[string]interface{}{
-					"role":    role,
-					"content": []interface{}{},
-				}
+				msg := `{"role":"","content":[]}`
+				msg, _ = sjson.Set(msg, "role", role)
 
 				// Handle content based on its type (string or array)
 				if contentResult.Exists() && contentResult.Type == gjson.String && contentResult.String() != "" {
-					// Simple text content conversion
-					msg["content"] = []interface{}{
-						map[string]interface{}{
-							"type": "text",
-							"text": contentResult.String(),
-						},
-					}
+					part := `{"type":"text","text":""}`
+					part, _ = sjson.Set(part, "text", contentResult.String())
+					msg, _ = sjson.SetRaw(msg, "content.-1", part)
 				} else if contentResult.Exists() && contentResult.IsArray() {
-					// Array of content parts processing
-					var contentParts []interface{}
 					contentResult.ForEach(func(_, part gjson.Result) bool {
 						partType := part.Get("type").String()
 
 						switch partType {
 						case "text":
-							// Text part conversion
-							contentParts = append(contentParts, map[string]interface{}{
-								"type": "text",
-								"text": part.Get("text").String(),
-							})
+							textPart := `{"type":"text","text":""}`
+							textPart, _ = sjson.Set(textPart, "text", part.Get("text").String())
+							msg, _ = sjson.SetRaw(msg, "content.-1", textPart)
 
 						case "image_url":
 							// Convert OpenAI image format to Claude Code format
@@ -191,132 +177,95 @@ func ConvertOpenAIRequestToClaude(modelName string, inputRawJSON []byte, stream
 									mediaType := strings.TrimPrefix(mediaTypePart, "data:")
 									data := parts[1]
 
-									contentParts = append(contentParts, map[string]interface{}{
-										"type": "image",
-										"source": map[string]interface{}{
-											"type":       "base64",
-											"media_type": mediaType,
-											"data":       data,
-										},
-									})
+									imagePart := `{"type":"image","source":{"type":"base64","media_type":"","data":""}}`
+									imagePart, _ = sjson.Set(imagePart, "source.media_type", mediaType)
+									imagePart, _ = sjson.Set(imagePart, "source.data", data)
+									msg, _ = sjson.SetRaw(msg, "content.-1", imagePart)
 								}
 							}
 						}
 						return true
 					})
-					if len(contentParts) > 0 {
-						msg["content"] = contentParts
-					}
-				} else {
-					// Initialize empty content array for tool calls
-					msg["content"] = []interface{}{}
 				}
 
 				// Handle tool calls (for assistant messages)
 				if toolCalls := message.Get("tool_calls"); toolCalls.Exists() && toolCalls.IsArray() && role == "assistant" {
-					var contentParts []interface{}
-
-					// Add existing text content if any
-					if existingContent, ok := msg["content"].([]interface{}); ok {
-						contentParts = existingContent
-					}
-
 					toolCalls.ForEach(func(_, toolCall gjson.Result) bool {
 						if toolCall.Get("type").String() == "function" {
 							toolCallID := toolCall.Get("id").String()
 							if toolCallID == "" {
 								toolCallID = genToolCallID()
 							}
-							toolCallIDs = append(toolCallIDs, toolCallID)
 
 							function := toolCall.Get("function")
-							toolUse := map[string]interface{}{
-								"type": "tool_use",
-								"id":   toolCallID,
-								"name": function.Get("name").String(),
-							}
+							toolUse := `{"type":"tool_use","id":"","name":"","input":{}}`
+							toolUse, _ = sjson.Set(toolUse, "id", toolCallID)
+							toolUse, _ = sjson.Set(toolUse, "name", function.Get("name").String())
 
 							// Parse arguments for the tool call
 							if args := function.Get("arguments"); args.Exists() {
 								argsStr := args.String()
-								if argsStr != "" {
-									var argsMap map[string]interface{}
-									if err := json.Unmarshal([]byte(argsStr), &argsMap); err == nil {
-										toolUse["input"] = argsMap
+								if argsStr != "" && gjson.Valid(argsStr) {
+									argsJSON := gjson.Parse(argsStr)
+									if argsJSON.IsObject() {
+										toolUse, _ = sjson.SetRaw(toolUse, "input", argsJSON.Raw)
 									} else {
-										toolUse["input"] = map[string]interface{}{}
+										toolUse, _ = sjson.SetRaw(toolUse, "input", "{}")
 									}
 								} else {
-									toolUse["input"] = map[string]interface{}{}
+									toolUse, _ = sjson.SetRaw(toolUse, "input", "{}")
 								}
 							} else {
-								toolUse["input"] = map[string]interface{}{}
+								toolUse, _ = sjson.SetRaw(toolUse, "input", "{}")
 							}
 
-							contentParts = append(contentParts, toolUse)
+							msg, _ = sjson.SetRaw(msg, "content.-1", toolUse)
 						}
 						return true
 					})
-					msg["content"] = contentParts
 				}
 
-				anthropicMessages = append(anthropicMessages, msg)
+				out, _ = sjson.SetRaw(out, "messages.-1", msg)
 
 			case "tool":
 				// Handle tool result messages conversion
 				toolCallID := message.Get("tool_call_id").String()
 				content := message.Get("content").String()
 
-				// Create tool result message in Claude Code format
-				msg := map[string]interface{}{
-					"role": "user",
-					"content": []interface{}{
-						map[string]interface{}{
-							"type":        "tool_result",
-							"tool_use_id": toolCallID,
-							"content":     content,
-						},
-					},
-				}
-
-				anthropicMessages = append(anthropicMessages, msg)
+				msg := `{"role":"user","content":[{"type":"tool_result","tool_use_id":"","content":""}]}`
+				msg, _ = sjson.Set(msg, "content.0.tool_use_id", toolCallID)
+				msg, _ = sjson.Set(msg, "content.0.content", content)
+				out, _ = sjson.SetRaw(out, "messages.-1", msg)
 			}
 			return true
 		})
 	}
 
-	// Set messages in the output template
-	if len(anthropicMessages) > 0 {
-		messagesJSON, _ := json.Marshal(anthropicMessages)
-		out, _ = sjson.SetRaw(out, "messages", string(messagesJSON))
-	}
-
 	// Tools mapping: OpenAI tools -> Claude Code tools
 	if tools := root.Get("tools"); tools.Exists() && tools.IsArray() && len(tools.Array()) > 0 {
-		var anthropicTools []interface{}
+		hasAnthropicTools := false
 		tools.ForEach(func(_, tool gjson.Result) bool {
 			if tool.Get("type").String() == "function" {
 				function := tool.Get("function")
-				anthropicTool := map[string]interface{}{
-					"name":        function.Get("name").String(),
-					"description": function.Get("description").String(),
-				}
+				anthropicTool := `{"name":"","description":""}`
+				anthropicTool, _ = sjson.Set(anthropicTool, "name", function.Get("name").String())
+				anthropicTool, _ = sjson.Set(anthropicTool, "description", function.Get("description").String())
 
 				// Convert parameters schema for the tool
 				if parameters := function.Get("parameters"); parameters.Exists() {
-					anthropicTool["input_schema"] = parameters.Value()
-				} else if parameters = function.Get("parametersJsonSchema"); parameters.Exists() {
-					anthropicTool["input_schema"] = parameters.Value()
+					anthropicTool, _ = sjson.SetRaw(anthropicTool, "input_schema", parameters.Raw)
+				} else if parameters := function.Get("parametersJsonSchema"); parameters.Exists() {
+					anthropicTool, _ = sjson.SetRaw(anthropicTool, "input_schema", parameters.Raw)
 				}
 
-				anthropicTools = append(anthropicTools, anthropicTool)
+				out, _ = sjson.SetRaw(out, "tools.-1", anthropicTool)
+				hasAnthropicTools = true
 			}
 			return true
 		})
 
-		if len(anthropicTools) > 0 {
-			toolsJSON, _ := json.Marshal(anthropicTools)
-			out, _ = sjson.SetRaw(out, "tools", string(toolsJSON))
+		if !hasAnthropicTools {
+			out, _ = sjson.Delete(out, "tools")
 		}
 	}
 
@@ -329,18 +278,17 @@ func ConvertOpenAIRequestToClaude(modelName string, inputRawJSON []byte, stream
 			case "none":
 				// Don't set tool_choice, Claude Code will not use tools
 			case "auto":
-				out, _ = sjson.Set(out, "tool_choice", map[string]interface{}{"type": "auto"})
+				out, _ = sjson.SetRaw(out, "tool_choice", `{"type":"auto"}`)
 			case "required":
-				out, _ = sjson.Set(out, "tool_choice", map[string]interface{}{"type": "any"})
+				out, _ = sjson.SetRaw(out, "tool_choice", `{"type":"any"}`)
 			}
 		case gjson.JSON:
 			// Specific tool choice mapping
 			if toolChoice.Get("type").String() == "function" {
 				functionName := toolChoice.Get("function.name").String()
-				out, _ = sjson.Set(out, "tool_choice", map[string]interface{}{
-					"type": "tool",
-					"name": functionName,
-				})
+				toolChoiceJSON := `{"type":"tool","name":""}`
+				toolChoiceJSON, _ = sjson.Set(toolChoiceJSON, "name", functionName)
+				out, _ = sjson.SetRaw(out, "tool_choice", toolChoiceJSON)
 			}
 		default:
 		}

internal/translator/claude/openai/chat-completions/claude_openai_response.go

@@ -8,7 +8,7 @@ package chat_completions
 import (
 	"bytes"
 	"context"
-	"encoding/json"
+	"fmt"
 	"strings"
 	"time"
 
@@ -178,18 +178,11 @@ func ConvertClaudeResponseToOpenAI(_ context.Context, modelName string, original
 				if arguments == "" {
 					arguments = "{}"
 				}
-
-				toolCall := map[string]interface{}{
-					"index": index,
-					"id":    accumulator.ID,
-					"type":  "function",
-					"function": map[string]interface{}{
-						"name":      accumulator.Name,
-						"arguments": arguments,
-					},
-				}
-
-				template, _ = sjson.Set(template, "choices.0.delta.tool_calls", []interface{}{toolCall})
+				template, _ = sjson.Set(template, "choices.0.delta.tool_calls.0.index", index)
+				template, _ = sjson.Set(template, "choices.0.delta.tool_calls.0.id", accumulator.ID)
+				template, _ = sjson.Set(template, "choices.0.delta.tool_calls.0.type", "function")
+				template, _ = sjson.Set(template, "choices.0.delta.tool_calls.0.function.name", accumulator.Name)
+				template, _ = sjson.Set(template, "choices.0.delta.tool_calls.0.function.arguments", arguments)
 
 				// Clean up the accumulator for this index
 				delete((*param).(*ConvertAnthropicResponseToOpenAIParams).ToolCallsAccumulator, index)
@@ -210,12 +203,11 @@ func ConvertClaudeResponseToOpenAI(_ context.Context, modelName string, original
 
 		// Handle usage information for token counts
 		if usage := root.Get("usage"); usage.Exists() {
-			usageObj := map[string]interface{}{
-				"prompt_tokens":     usage.Get("input_tokens").Int(),
-				"completion_tokens": usage.Get("output_tokens").Int(),
-				"total_tokens":      usage.Get("input_tokens").Int() + usage.Get("output_tokens").Int(),
-			}
-			template, _ = sjson.Set(template, "usage", usageObj)
+			inputTokens := usage.Get("input_tokens").Int()
+			outputTokens := usage.Get("output_tokens").Int()
+			template, _ = sjson.Set(template, "usage.prompt_tokens", inputTokens)
+			template, _ = sjson.Set(template, "usage.completion_tokens", outputTokens)
+			template, _ = sjson.Set(template, "usage.total_tokens", inputTokens+outputTokens)
 		}
 		return []string{template}
 
@@ -230,14 +222,10 @@ func ConvertClaudeResponseToOpenAI(_ context.Context, modelName string, original
 	case "error":
 		// Error event - format and return error response
 		if errorData := root.Get("error"); errorData.Exists() {
-			errorResponse := map[string]interface{}{
-				"error": map[string]interface{}{
-					"message": errorData.Get("message").String(),
-					"type":    errorData.Get("type").String(),
-				},
-			}
-			errorJSON, _ := json.Marshal(errorResponse)
-			return []string{string(errorJSON)}
+			errorJSON := `{"error":{"message":"","type":""}}`
+			errorJSON, _ = sjson.Set(errorJSON, "error.message", errorData.Get("message").String())
+			errorJSON, _ = sjson.Set(errorJSON, "error.type", errorData.Get("type").String())
+			return []string{errorJSON}
 		}
 		return []string{}
 
@@ -298,10 +286,7 @@ func ConvertClaudeResponseToOpenAINonStream(_ context.Context, _ string, origina
 	var stopReason string
 	var contentParts []string
 	var reasoningParts []string
-	// Use map to track tool calls by index for proper merging
-	toolCallsMap := make(map[int]map[string]interface{})
-	// Track tool call arguments accumulation
-	toolCallArgsMap := make(map[int]strings.Builder)
+	toolCallsAccumulator := make(map[int]*ToolCallAccumulator)
 
 	for _, chunk := range chunks {
 		root := gjson.ParseBytes(chunk)
@@ -327,18 +312,12 @@ func ConvertClaudeResponseToOpenAINonStream(_ context.Context, _ string, origina
 					// Start of thinking/reasoning content - skip for now as it's handled in delta
 					continue
 				} else if blockType == "tool_use" {
-					// Initialize tool call tracking for this index
+					// Initialize tool call accumulator for this index
 					index := int(root.Get("index").Int())
-					toolCallsMap[index] = map[string]interface{}{
-						"id":   contentBlock.Get("id").String(),
-						"type": "function",
-						"function": map[string]interface{}{
-							"name":      contentBlock.Get("name").String(),
-							"arguments": "",
-						},
+					toolCallsAccumulator[index] = &ToolCallAccumulator{
+						ID:   contentBlock.Get("id").String(),
+						Name: contentBlock.Get("name").String(),
 					}
-					// Initialize arguments builder for this tool call
-					toolCallArgsMap[index] = strings.Builder{}
 				}
 			}
 
@@ -361,9 +340,8 @@ func ConvertClaudeResponseToOpenAINonStream(_ context.Context, _ string, origina
 					// Accumulate tool call arguments
 					if partialJSON := delta.Get("partial_json"); partialJSON.Exists() {
 						index := int(root.Get("index").Int())
-						if builder, exists := toolCallArgsMap[index]; exists {
-							builder.WriteString(partialJSON.String())
-							toolCallArgsMap[index] = builder
+						if accumulator, exists := toolCallsAccumulator[index]; exists {
+							accumulator.Arguments.WriteString(partialJSON.String())
 						}
 					}
 				}
@@ -372,14 +350,9 @@ func ConvertClaudeResponseToOpenAINonStream(_ context.Context, _ string, origina
 		case "content_block_stop":
 			// Finalize tool call arguments for this index when content block ends
 			index := int(root.Get("index").Int())
-			if toolCall, exists := toolCallsMap[index]; exists {
-				if builder, argsExists := toolCallArgsMap[index]; argsExists {
-					// Set the accumulated arguments for the tool call
-					arguments := builder.String()
-					if arguments == "" {
-						arguments = "{}"
-					}
-					toolCall["function"].(map[string]interface{})["arguments"] = arguments
+			if accumulator, exists := toolCallsAccumulator[index]; exists {
+				if accumulator.Arguments.Len() == 0 {
+					accumulator.Arguments.WriteString("{}")
 				}
 			}
 
@@ -417,24 +390,35 @@ func ConvertClaudeResponseToOpenAINonStream(_ context.Context, _ string, origina
 	}
 
 	// Set tool calls if any were accumulated during processing
-	if len(toolCallsMap) > 0 {
-		// Convert tool calls map to array, preserving order by index
-		var toolCallsArray []interface{}
-		// Find the maximum index to determine the range
+	if len(toolCallsAccumulator) > 0 {
+		toolCallsCount := 0
 		maxIndex := -1
-		for index := range toolCallsMap {
+		for index := range toolCallsAccumulator {
 			if index > maxIndex {
 				maxIndex = index
 			}
 		}
-		// Iterate through all possible indices up to maxIndex
+
 		for i := 0; i <= maxIndex; i++ {
-			if toolCall, exists := toolCallsMap[i]; exists {
-				toolCallsArray = append(toolCallsArray, toolCall)
+			accumulator, exists := toolCallsAccumulator[i]
+			if !exists {
+				continue
 			}
+
+			arguments := accumulator.Arguments.String()
+
+			idPath := fmt.Sprintf("choices.0.message.tool_calls.%d.id", toolCallsCount)
+			typePath := fmt.Sprintf("choices.0.message.tool_calls.%d.type", toolCallsCount)
+			namePath := fmt.Sprintf("choices.0.message.tool_calls.%d.function.name", toolCallsCount)
+			argumentsPath := fmt.Sprintf("choices.0.message.tool_calls.%d.function.arguments", toolCallsCount)
+
+			out, _ = sjson.Set(out, idPath, accumulator.ID)
+			out, _ = sjson.Set(out, typePath, "function")
+			out, _ = sjson.Set(out, namePath, accumulator.Name)
+			out, _ = sjson.Set(out, argumentsPath, arguments)
+			toolCallsCount++
 		}
-		if len(toolCallsArray) > 0 {
-			out, _ = sjson.Set(out, "choices.0.message.tool_calls", toolCallsArray)
+		if toolCallsCount > 0 {
 			out, _ = sjson.Set(out, "choices.0.finish_reason", "tool_calls")
 		} else {
 			out, _ = sjson.Set(out, "choices.0.finish_reason", mapAnthropicStopReasonToOpenAI(stopReason))

internal/translator/claude/openai/responses/claude_openai-responses_request.go

@@ -254,7 +254,10 @@ func ConvertOpenAIResponsesRequestToClaude(modelName string, inputRawJSON []byte
 				toolUse, _ = sjson.Set(toolUse, "id", callID)
 				toolUse, _ = sjson.Set(toolUse, "name", name)
 				if argsStr != "" && gjson.Valid(argsStr) {
-					toolUse, _ = sjson.SetRaw(toolUse, "input", argsStr)
+					argsJSON := gjson.Parse(argsStr)
+					if argsJSON.IsObject() {
+						toolUse, _ = sjson.SetRaw(toolUse, "input", argsJSON.Raw)
+					}
 				}
 
 				asst := `{"role":"assistant","content":[]}`
@@ -309,16 +312,18 @@ func ConvertOpenAIResponsesRequestToClaude(modelName string, inputRawJSON []byte
 		case gjson.String:
 			switch toolChoice.String() {
 			case "auto":
-				out, _ = sjson.Set(out, "tool_choice", map[string]interface{}{"type": "auto"})
+				out, _ = sjson.SetRaw(out, "tool_choice", `{"type":"auto"}`)
 			case "none":
 				// Leave unset; implies no tools
 			case "required":
-				out, _ = sjson.Set(out, "tool_choice", map[string]interface{}{"type": "any"})
+				out, _ = sjson.SetRaw(out, "tool_choice", `{"type":"any"}`)
 			}
 		case gjson.JSON:
 			if toolChoice.Get("type").String() == "function" {
 				fn := toolChoice.Get("function.name").String()
-				out, _ = sjson.Set(out, "tool_choice", map[string]interface{}{"type": "tool", "name": fn})
+				toolChoiceJSON := `{"name":"","type":"tool"}`
+				toolChoiceJSON, _ = sjson.Set(toolChoiceJSON, "name", fn)
+				out, _ = sjson.SetRaw(out, "tool_choice", toolChoiceJSON)
 			}
 		default:
 

internal/translator/claude/openai/responses/claude_openai-responses_response.go

@@ -344,31 +344,20 @@ func ConvertClaudeResponseToOpenAIResponses(ctx context.Context, modelName strin
 		}
 
 		// Build response.output from aggregated state
-		var outputs []interface{}
+		outputsWrapper := `{"arr":[]}`
 		// reasoning item (if any)
 		if st.ReasoningBuf.Len() > 0 || st.ReasoningPartAdded {
-			r := map[string]interface{}{
-				"id":      st.ReasoningItemID,
-				"type":    "reasoning",
-				"summary": []interface{}{map[string]interface{}{"type": "summary_text", "text": st.ReasoningBuf.String()}},
-			}
-			outputs = append(outputs, r)
+			item := `{"id":"","type":"reasoning","summary":[{"type":"summary_text","text":""}]}`
+			item, _ = sjson.Set(item, "id", st.ReasoningItemID)
+			item, _ = sjson.Set(item, "summary.0.text", st.ReasoningBuf.String())
+			outputsWrapper, _ = sjson.SetRaw(outputsWrapper, "arr.-1", item)
 		}
 		// assistant message item (if any text)
 		if st.TextBuf.Len() > 0 || st.InTextBlock || st.CurrentMsgID != "" {
-			m := map[string]interface{}{
-				"id":     st.CurrentMsgID,
-				"type":   "message",
-				"status": "completed",
-				"content": []interface{}{map[string]interface{}{
-					"type":        "output_text",
-					"annotations": []interface{}{},
-					"logprobs":    []interface{}{},
-					"text":        st.TextBuf.String(),
-				}},
-				"role": "assistant",
-			}
-			outputs = append(outputs, m)
+			item := `{"id":"","type":"message","status":"completed","content":[{"type":"output_text","annotations":[],"logprobs":[],"text":""}],"role":"assistant"}`
+			item, _ = sjson.Set(item, "id", st.CurrentMsgID)
+			item, _ = sjson.Set(item, "content.0.text", st.TextBuf.String())
+			outputsWrapper, _ = sjson.SetRaw(outputsWrapper, "arr.-1", item)
 		}
 		// function_call items (in ascending index order for determinism)
 		if len(st.FuncArgsBuf) > 0 {
@@ -395,19 +384,16 @@ func ConvertClaudeResponseToOpenAIResponses(ctx context.Context, modelName strin
 				if callID == "" && st.CurrentFCID != "" {
 					callID = st.CurrentFCID
 				}
-				item := map[string]interface{}{
-					"id":        fmt.Sprintf("fc_%s", callID),
-					"type":      "function_call",
-					"status":    "completed",
-					"arguments": args,
-					"call_id":   callID,
-					"name":      name,
-				}
-				outputs = append(outputs, item)
+				item := `{"id":"","type":"function_call","status":"completed","arguments":"","call_id":"","name":""}`
+				item, _ = sjson.Set(item, "id", fmt.Sprintf("fc_%s", callID))
+				item, _ = sjson.Set(item, "arguments", args)
+				item, _ = sjson.Set(item, "call_id", callID)
+				item, _ = sjson.Set(item, "name", name)
+				outputsWrapper, _ = sjson.SetRaw(outputsWrapper, "arr.-1", item)
 			}
 		}
-		if len(outputs) > 0 {
-			completed, _ = sjson.Set(completed, "response.output", outputs)
+		if gjson.Get(outputsWrapper, "arr.#").Int() > 0 {
+			completed, _ = sjson.SetRaw(completed, "response.output", gjson.Get(outputsWrapper, "arr").Raw)
 		}
 
 		reasoningTokens := int64(0)
@@ -628,27 +614,18 @@ func ConvertClaudeResponseToOpenAIResponsesNonStream(_ context.Context, _ string
 	}
 
 	// Build output array
-	var outputs []interface{}
+	outputsWrapper := `{"arr":[]}`
 	if reasoningBuf.Len() > 0 {
-		outputs = append(outputs, map[string]interface{}{
-			"id":      reasoningItemID,
-			"type":    "reasoning",
-			"summary": []interface{}{map[string]interface{}{"type": "summary_text", "text": reasoningBuf.String()}},
-		})
+		item := `{"id":"","type":"reasoning","summary":[{"type":"summary_text","text":""}]}`
+		item, _ = sjson.Set(item, "id", reasoningItemID)
+		item, _ = sjson.Set(item, "summary.0.text", reasoningBuf.String())
+		outputsWrapper, _ = sjson.SetRaw(outputsWrapper, "arr.-1", item)
 	}
 	if currentMsgID != "" || textBuf.Len() > 0 {
-		outputs = append(outputs, map[string]interface{}{
-			"id":     currentMsgID,
-			"type":   "message",
-			"status": "completed",
-			"content": []interface{}{map[string]interface{}{
-				"type":        "output_text",
-				"annotations": []interface{}{},
-				"logprobs":    []interface{}{},
-				"text":        textBuf.String(),
-			}},
-			"role": "assistant",
-		})
+		item := `{"id":"","type":"message","status":"completed","content":[{"type":"output_text","annotations":[],"logprobs":[],"text":""}],"role":"assistant"}`
+		item, _ = sjson.Set(item, "id", currentMsgID)
+		item, _ = sjson.Set(item, "content.0.text", textBuf.String())
+		outputsWrapper, _ = sjson.SetRaw(outputsWrapper, "arr.-1", item)
 	}
 	if len(toolCalls) > 0 {
 		// Preserve index order
@@ -669,18 +646,16 @@ func ConvertClaudeResponseToOpenAIResponsesNonStream(_ context.Context, _ string
 			if args == "" {
 				args = "{}"
 			}
-			outputs = append(outputs, map[string]interface{}{
-				"id":        fmt.Sprintf("fc_%s", st.id),
-				"type":      "function_call",
-				"status":    "completed",
-				"arguments": args,
-				"call_id":   st.id,
-				"name":      st.name,
-			})
+			item := `{"id":"","type":"function_call","status":"completed","arguments":"","call_id":"","name":""}`
+			item, _ = sjson.Set(item, "id", fmt.Sprintf("fc_%s", st.id))
+			item, _ = sjson.Set(item, "arguments", args)
+			item, _ = sjson.Set(item, "call_id", st.id)
+			item, _ = sjson.Set(item, "name", st.name)
+			outputsWrapper, _ = sjson.SetRaw(outputsWrapper, "arr.-1", item)
 		}
 	}
-	if len(outputs) > 0 {
-		out, _ = sjson.Set(out, "output", outputs)
+	if gjson.Get(outputsWrapper, "arr.#").Int() > 0 {
+		out, _ = sjson.SetRaw(out, "output", gjson.Get(outputsWrapper, "arr").Raw)
 	}
 
 	// Usage