fix(translator): improve tool response handling for non-string content

- Added `setToolCallOutputContent` to process various content types, including arrays and fallback cases.
- Implemented robust handling for specific tool output types like text, image URLs, and files, ensuring proper serialization.
- Improved fallback logic to handle unexpected or missing data.

Fixed: #2313
Closes: #2349

internal/translator/codex/openai/chat-completions/codex_openai_request.go

@@ -121,13 +121,13 @@ func ConvertOpenAIRequestToCodex(modelName string, inputRawJSON []byte, stream b
 			case "tool":
 				// Handle tool response messages as top-level function_call_output objects
 				toolCallID := m.Get("tool_call_id").String()
-				content := m.Get("content").String()
+				content := m.Get("content")
 
 				// Create function_call_output object
 				funcOutput := []byte(`{}`)
 				funcOutput, _ = sjson.SetBytes(funcOutput, "type", "function_call_output")
 				funcOutput, _ = sjson.SetBytes(funcOutput, "call_id", toolCallID)
-				funcOutput, _ = sjson.SetBytes(funcOutput, "output", content)
+				funcOutput = setToolCallOutputContent(funcOutput, content)
 				out, _ = sjson.SetRawBytes(out, "input.-1", funcOutput)
 
 			default:
@@ -359,6 +359,91 @@ func ConvertOpenAIRequestToCodex(modelName string, inputRawJSON []byte, stream b
 	return out
 }
 
+func setToolCallOutputContent(funcOutput []byte, content gjson.Result) []byte {
+	switch {
+	case content.Type == gjson.String:
+		funcOutput, _ = sjson.SetBytes(funcOutput, "output", content.String())
+	case content.IsArray():
+		output := []byte(`[]`)
+		for _, item := range content.Array() {
+			output = appendToolOutputContentPart(output, item)
+		}
+		funcOutput, _ = sjson.SetRawBytes(funcOutput, "output", output)
+	default:
+		fallbackOutput := content.Raw
+		if fallbackOutput == "" {
+			fallbackOutput = content.String()
+		}
+		funcOutput, _ = sjson.SetBytes(funcOutput, "output", fallbackOutput)
+	}
+	return funcOutput
+}
+
+func appendToolOutputContentPart(output []byte, item gjson.Result) []byte {
+	switch item.Get("type").String() {
+	case "text":
+		part := []byte(`{}`)
+		part, _ = sjson.SetBytes(part, "type", "input_text")
+		part, _ = sjson.SetBytes(part, "text", item.Get("text").String())
+		output, _ = sjson.SetRawBytes(output, "-1", part)
+	case "image_url":
+		imageURL := item.Get("image_url.url").String()
+		fileID := item.Get("image_url.file_id").String()
+		if imageURL == "" && fileID == "" {
+			return appendToolOutputFallbackPart(output, item)
+		}
+		part := []byte(`{}`)
+		part, _ = sjson.SetBytes(part, "type", "input_image")
+		if imageURL != "" {
+			part, _ = sjson.SetBytes(part, "image_url", imageURL)
+		}
+		if fileID != "" {
+			part, _ = sjson.SetBytes(part, "file_id", fileID)
+		}
+		if detail := item.Get("image_url.detail").String(); detail != "" {
+			part, _ = sjson.SetBytes(part, "detail", detail)
+		}
+		output, _ = sjson.SetRawBytes(output, "-1", part)
+	case "file":
+		fileID := item.Get("file.file_id").String()
+		fileData := item.Get("file.file_data").String()
+		fileURL := item.Get("file.file_url").String()
+		if fileID == "" && fileData == "" && fileURL == "" {
+			return appendToolOutputFallbackPart(output, item)
+		}
+		part := []byte(`{}`)
+		part, _ = sjson.SetBytes(part, "type", "input_file")
+		if fileID != "" {
+			part, _ = sjson.SetBytes(part, "file_id", fileID)
+		}
+		if fileData != "" {
+			part, _ = sjson.SetBytes(part, "file_data", fileData)
+		}
+		if fileURL != "" {
+			part, _ = sjson.SetBytes(part, "file_url", fileURL)
+		}
+		if filename := item.Get("file.filename").String(); filename != "" {
+			part, _ = sjson.SetBytes(part, "filename", filename)
+		}
+		output, _ = sjson.SetRawBytes(output, "-1", part)
+	default:
+		output = appendToolOutputFallbackPart(output, item)
+	}
+	return output
+}
+
+func appendToolOutputFallbackPart(output []byte, item gjson.Result) []byte {
+	text := item.Raw
+	if text == "" {
+		text = item.String()
+	}
+	part := []byte(`{}`)
+	part, _ = sjson.SetBytes(part, "type", "input_text")
+	part, _ = sjson.SetBytes(part, "text", text)
+	output, _ = sjson.SetRawBytes(output, "-1", part)
+	return output
+}
+
 // shortenNameIfNeeded applies the simple shortening rule for a single name.
 // If the name length exceeds 64, it will try to preserve the "mcp__" prefix and last segment.
 // Otherwise it truncates to 64 characters.