fix(openai): preserve usage path precedence

backend/internal/service/openai_gateway_response_handling.go

@@ -981,15 +981,15 @@ func extractOpenAIUsageFromJSONBytes(body []byte) (OpenAIUsage, bool) {
 	}
 	// 部分 OpenAI 兼容上游（例如 Cline API）会将标准响应包在 data 字段中：
 	// {"data":{"choices": [...], "usage": {...}}, "success":true}。
-	// 按优先级尝试原生 OpenAI Responses、兼容层 data 包装和 Responses 包装，
+	// 按优先级先保留原有路径，再尝试兼容层 data 包装，
 	// 避免同步请求能正常返回但用量被静默记录为 0。
 	candidates := []struct {
 		usagePath      string
 		imageUsagePath string
 	}{
 		{usagePath: "usage", imageUsagePath: "tool_usage.image_gen"},
-		{usagePath: "data.usage", imageUsagePath: "data.tool_usage.image_gen"},
 		{usagePath: "response.usage", imageUsagePath: "response.tool_usage.image_gen"},
+		{usagePath: "data.usage", imageUsagePath: "data.tool_usage.image_gen"},
 		{usagePath: "data.response.usage", imageUsagePath: "data.response.tool_usage.image_gen"},
 	}
 	for _, candidate := range candidates {

backend/internal/service/openai_gateway_service_test.go

@@ -483,6 +483,27 @@ func TestExtractOpenAIUsage_ReadsClineDataEnvelope(t *testing.T) {
 	require.Equal(t, 4, usage.CacheReadInputTokens)
 }
 
+func TestExtractOpenAIUsage_ReadsWrappedResponsesDataEnvelope(t *testing.T) {
+	body := []byte(`{"data":{"response":{"usage":{"input_tokens":11,"output_tokens":5,"total_tokens":16,"input_tokens_details":{"cached_tokens":2}}}}}`)
+
+	usage, ok := extractOpenAIUsageFromJSONBytes(body)
+
+	require.True(t, ok)
+	require.Equal(t, 11, usage.InputTokens)
+	require.Equal(t, 5, usage.OutputTokens)
+	require.Equal(t, 2, usage.CacheReadInputTokens)
+}
+
+func TestExtractOpenAIUsage_PreservesResponseUsagePriority(t *testing.T) {
+	body := []byte(`{"data":{"usage":{"prompt_tokens":100,"completion_tokens":50}},"response":{"usage":{"input_tokens":11,"output_tokens":5}}}`)
+
+	usage, ok := extractOpenAIUsageFromJSONBytes(body)
+
+	require.True(t, ok)
+	require.Equal(t, 11, usage.InputTokens)
+	require.Equal(t, 5, usage.OutputTokens)
+}
+
 func TestOpenAIGatewayService_BindHTTPResponseAccount(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	rec := httptest.NewRecorder()