refactor: 后端代码质量优化 - 复用公共库、使用标准库、类型安全错误判断

## 高优先级修复
- stats_service_impl: 使用 strings.SplitN 替代错误的索引分割
- provider_handler: 使用 errors.Is(err, gorm.ErrDuplicatedKey) 替代字符串匹配
- client: 重写 isNetworkError 使用 errors.As/Is 类型安全判断
- proxy_handler: 使用 encoding/json 标准库解析 JSON（extractModelName、isStreamRequest）

## 中优先级修复
- stats_handler: 添加 parseDateParam 辅助函数消除重复日期解析
- pkg/errors: 新增 ErrRequestCreate/Send/ResponseRead 错误类型和 WithCause 方法
- client: 使用结构化错误替代 fmt.Errorf
- ConversionEngine: logger 依赖注入，替换所有 zap.L() 调用

## 低优先级修复
- encoder: 删除 joinStrings，使用 strings.Join
- adapter: 删除 modelInfoRegex 正则，使用 isModelInfoPath 字符串函数

## 文档更新
- README.md: 添加公共库使用指南和编码规范章节
- specs: 同步 delta specs 到 main specs（error-handling、structured-logging、request-validation）

## 归档
- openspec/changes/archive/2026-04-20-refactor-backend-code-quality/

backend/README.md

@@ -329,3 +329,61 @@ make lint
 ### 环境要求
 
 - Go 1.26 或更高版本
+
+## 公共库使用指南
+
+### pkg/errors — 结构化错误
+
+使用预定义的错误类型，配合 `errors.Is` / `errors.As` 判断错误：
+
+```go
+import (
+    "errors"
+    pkgErrors "nex/backend/pkg/errors"
+)
+
+// 使用预定义错误
+return pkgErrors.ErrRequestSend.WithCause(err)
+
+// 判断错误类型
+var appErr *pkgErrors.AppError
+if errors.As(err, &appErr) {
+    // appErr.Code, appErr.HTTPStatus, appErr.Message
+}
+```
+
+可用函数：`NewAppError`、`Wrap`、`WithContext`、`WithMessage`、`AsAppError`
+
+预定义错误：`ErrModelNotFound`、`ErrProviderNotFound`、`ErrInvalidRequest`、`ErrRequestCreate`、`ErrRequestSend`、`ErrResponseRead` 等
+
+### pkg/logger — 日志系统
+
+使用依赖注入模式，构造函数接受 `*zap.Logger` 参数，nil 时回退到 `zap.L()`：
+
+```go
+func NewMyService(repo Repository, logger *zap.Logger) *MyService {
+    if logger == nil {
+        logger = zap.L()
+    }
+    return &MyService{repo: repo, logger: logger}
+}
+```
+
+禁止直接在业务代码中使用 `zap.L()` 全局 logger，应通过构造函数注入。
+
+### pkg/validator — 请求验证
+
+```go
+import "nex/backend/pkg/validator"
+
+v := validator.Get()
+err := v.Validate(myStruct)
+```
+
+## 编码规范
+
+- **JSON 解析**：使用 `encoding/json` 标准库（`json.Unmarshal` / `json.Marshal`），不手动扫描字节
+- **字符串拼接**：使用 `strings.Join`，不手写循环拼接
+- **错误判断**：使用 `errors.Is` / `errors.As`，不使用字符串匹配（`strings.Contains(err.Error(), ...)`）
+- **日志使用**：通过依赖注入 `*zap.Logger`，不直接调用 `zap.L()`
+- **字符串分割**：使用 `strings.SplitN(key, "/", 2)` 等精确分割，不使用索引切片

backend/cmd/server/main.go

@@ -81,7 +81,7 @@ func main() {
 	if err := registry.Register(anthropic.NewAdapter()); err != nil {
 		zapLogger.Fatal("注册 Anthropic 适配器失败", zap.String("error", err.Error()))
 	}
-	engine := conversion.NewConversionEngine(registry)
+	engine := conversion.NewConversionEngine(registry, zapLogger)
 
 	// 7. 初始化 provider client
 	providerClient := provider.NewClient()

backend/internal/conversion/anthropic/adapter.go

@@ -2,7 +2,6 @@ package anthropic
 
 import (
 	"encoding/json"
-	"regexp"
 	"strings"
 
 	"nex/backend/internal/conversion"
@@ -17,8 +16,6 @@ func NewAdapter() *Adapter {
 	return &Adapter{}
 }
 
-var modelInfoRegex = regexp.MustCompile(`^/v1/models/[^/]+$`)
-
 // ProtocolName 返回协议名称
 func (a *Adapter) ProtocolName() string { return "anthropic" }
 
@@ -35,13 +32,22 @@ func (a *Adapter) DetectInterfaceType(nativePath string) conversion.InterfaceTyp
 		return conversion.InterfaceTypeChat
 	case nativePath == "/v1/models":
 		return conversion.InterfaceTypeModels
-	case modelInfoRegex.MatchString(nativePath):
+	case isModelInfoPath(nativePath):
 		return conversion.InterfaceTypeModelInfo
 	default:
 		return conversion.InterfaceTypePassthrough
 	}
 }
 
+// isModelInfoPath 判断是否为模型详情路径（/v1/models/{id}）
+func isModelInfoPath(path string) bool {
+	if !strings.HasPrefix(path, "/v1/models/") {
+		return false
+	}
+	suffix := path[len("/v1/models/"):]
+	return suffix != "" && !strings.Contains(suffix, "/")
+}
+
 // BuildUrl 根据接口类型构建 URL
 func (a *Adapter) BuildUrl(nativePath string, interfaceType conversion.InterfaceType) string {
 	switch interfaceType {

backend/internal/conversion/engine.go

@@ -28,13 +28,18 @@ type HTTPResponseSpec struct {
 type ConversionEngine struct {
 	registry        AdapterRegistry
 	middlewareChain *MiddlewareChain
+	logger          *zap.Logger
 }
 
 // NewConversionEngine 创建转换引擎
-func NewConversionEngine(registry AdapterRegistry) *ConversionEngine {
+func NewConversionEngine(registry AdapterRegistry, logger *zap.Logger) *ConversionEngine {
+	if logger == nil {
+		logger = zap.L()
+	}
 	return &ConversionEngine{
 		registry:        registry,
 		middlewareChain: NewMiddlewareChain(),
+		logger:          logger,
 	}
 }
 
@@ -251,12 +256,12 @@ func (e *ConversionEngine) convertChatResponseBody(clientAdapter, providerAdapte
 func (e *ConversionEngine) convertModelsResponseBody(clientAdapter, providerAdapter ProtocolAdapter, body []byte) ([]byte, error) {
 	models, err := providerAdapter.DecodeModelsResponse(body)
 	if err != nil {
-		zap.L().Warn("解码 Models 响应失败，返回原始响应", zap.String("error", err.Error()))
+		e.logger.Warn("解码 Models 响应失败，返回原始响应", zap.String("error", err.Error()))
 		return body, nil
 	}
 	encoded, err := clientAdapter.EncodeModelsResponse(models)
 	if err != nil {
-		zap.L().Warn("编码 Models 响应失败，返回原始响应", zap.String("error", err.Error()))
+		e.logger.Warn("编码 Models 响应失败，返回原始响应", zap.String("error", err.Error()))
 		return body, nil
 	}
 	return encoded, nil
@@ -265,12 +270,12 @@ func (e *ConversionEngine) convertModelsResponseBody(clientAdapter, providerAdap
 func (e *ConversionEngine) convertModelInfoResponseBody(clientAdapter, providerAdapter ProtocolAdapter, body []byte) ([]byte, error) {
 	info, err := providerAdapter.DecodeModelInfoResponse(body)
 	if err != nil {
-		zap.L().Warn("解码 ModelInfo 响应失败，返回原始响应", zap.String("error", err.Error()))
+		e.logger.Warn("解码 ModelInfo 响应失败，返回原始响应", zap.String("error", err.Error()))
 		return body, nil
 	}
 	encoded, err := clientAdapter.EncodeModelInfoResponse(info)
 	if err != nil {
-		zap.L().Warn("编码 ModelInfo 响应失败，返回原始响应", zap.String("error", err.Error()))
+		e.logger.Warn("编码 ModelInfo 响应失败，返回原始响应", zap.String("error", err.Error()))
 		return body, nil
 	}
 	return encoded, nil
@@ -279,7 +284,7 @@ func (e *ConversionEngine) convertModelInfoResponseBody(clientAdapter, providerA
 func (e *ConversionEngine) convertEmbeddingBody(clientAdapter, providerAdapter ProtocolAdapter, provider *TargetProvider, body []byte) ([]byte, error) {
 	req, err := clientAdapter.DecodeEmbeddingRequest(body)
 	if err != nil {
-		zap.L().Warn("解码 Embedding 请求失败，返回原始请求", zap.String("error", err.Error()))
+		e.logger.Warn("解码 Embedding 请求失败，返回原始请求", zap.String("error", err.Error()))
 		return body, nil
 	}
 	return providerAdapter.EncodeEmbeddingRequest(req, provider)
@@ -288,7 +293,7 @@ func (e *ConversionEngine) convertEmbeddingBody(clientAdapter, providerAdapter P
 func (e *ConversionEngine) convertEmbeddingResponseBody(clientAdapter, providerAdapter ProtocolAdapter, body []byte) ([]byte, error) {
 	resp, err := providerAdapter.DecodeEmbeddingResponse(body)
 	if err != nil {
-		zap.L().Warn("解码 Embedding 响应失败，返回原始响应", zap.String("error", err.Error()))
+		e.logger.Warn("解码 Embedding 响应失败，返回原始响应", zap.String("error", err.Error()))
 		return body, nil
 	}
 	return clientAdapter.EncodeEmbeddingResponse(resp)
@@ -297,7 +302,7 @@ func (e *ConversionEngine) convertEmbeddingResponseBody(clientAdapter, providerA
 func (e *ConversionEngine) convertRerankBody(clientAdapter, providerAdapter ProtocolAdapter, provider *TargetProvider, body []byte) ([]byte, error) {
 	req, err := clientAdapter.DecodeRerankRequest(body)
 	if err != nil {
-		zap.L().Warn("解码 Rerank 请求失败，返回原始请求", zap.String("error", err.Error()))
+		e.logger.Warn("解码 Rerank 请求失败，返回原始请求", zap.String("error", err.Error()))
 		return body, nil
 	}
 	return providerAdapter.EncodeRerankRequest(req, provider)

backend/internal/conversion/engine_supplemental_test.go

@@ -39,7 +39,7 @@ func TestConversionError_FullBuilder(t *testing.T) {
 
 func TestEngine_Use(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	called := false
 	engine.Use(&testMiddleware{fn: func(req *canonical.CanonicalRequest, cp, pp string, ctx *ConversionContext) (*canonical.CanonicalRequest, error) {
 		called = true
@@ -66,7 +66,7 @@ func TestEngine_Use(t *testing.T) {
 
 func TestConvertHttpRequest_DecodeError(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	clientAdapter := newMockAdapter("client", false)
 	clientAdapter.decodeReqFn = func(raw []byte) (*canonical.CanonicalRequest, error) {
 		return nil, errors.New("decode failed")
@@ -82,7 +82,7 @@ func TestConvertHttpRequest_DecodeError(t *testing.T) {
 
 func TestConvertHttpRequest_EncodeError(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	_ = engine.RegisterAdapter(newMockAdapter("client", false))
 	providerAdapter := newMockAdapter("provider", false)
 	providerAdapter.encodeReqFn = func(req *canonical.CanonicalRequest, p *TargetProvider) ([]byte, error) {
@@ -98,7 +98,7 @@ func TestConvertHttpRequest_EncodeError(t *testing.T) {
 
 func TestConvertHttpResponse_CrossProtocol(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 
 	clientAdapter := newMockAdapter("client", false)
 	clientAdapter.encodeRespFn = func(resp *canonical.CanonicalResponse) ([]byte, error) {
@@ -121,7 +121,7 @@ func TestConvertHttpResponse_CrossProtocol(t *testing.T) {
 
 func TestConvertHttpResponse_DecodeError(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	providerAdapter := newMockAdapter("provider", false)
 	providerAdapter.decodeRespFn = func(raw []byte) (*canonical.CanonicalResponse, error) {
 		return nil, errors.New("decode error")
@@ -135,7 +135,7 @@ func TestConvertHttpResponse_DecodeError(t *testing.T) {
 
 func TestConvertHttpRequest_EmbeddingInterface(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 
 	clientAdapter := newMockAdapter("client", false)
 	clientAdapter.ifaceType = InterfaceTypeEmbeddings
@@ -158,7 +158,7 @@ func TestConvertHttpRequest_EmbeddingInterface(t *testing.T) {
 
 func TestConvertHttpRequest_RerankInterface(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 
 	clientAdapter := newMockAdapter("client", false)
 	clientAdapter.ifaceType = InterfaceTypeRerank
@@ -178,7 +178,7 @@ func TestConvertHttpRequest_RerankInterface(t *testing.T) {
 
 func TestConvertHttpResponse_EmbeddingInterface(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 
 	clientAdapter := newMockAdapter("client", false)
 	clientAdapter.supportsIface = map[InterfaceType]bool{InterfaceTypeEmbeddings: true}
@@ -196,7 +196,7 @@ func TestConvertHttpResponse_EmbeddingInterface(t *testing.T) {
 
 func TestConvertHttpResponse_RerankInterface(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 
 	clientAdapter := newMockAdapter("client", false)
 	clientAdapter.supportsIface = map[InterfaceType]bool{InterfaceTypeRerank: true}
@@ -214,7 +214,7 @@ func TestConvertHttpResponse_RerankInterface(t *testing.T) {
 
 func TestConvertHttpRequest_ModelsInterface_Passthrough(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	clientAdapter := newMockAdapter("client", false)
 	clientAdapter.ifaceType = InterfaceTypeModels
 	providerAdapter := newMockAdapter("provider", false)
@@ -232,7 +232,7 @@ func TestConvertHttpRequest_ModelsInterface_Passthrough(t *testing.T) {
 
 func TestConvertHttpResponse_ModelsInterface(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	clientAdapter := newMockAdapter("client", false)
 	clientAdapter.supportsIface = map[InterfaceType]bool{InterfaceTypeModels: true}
 	providerAdapter := newMockAdapter("provider", false)
@@ -249,7 +249,7 @@ func TestConvertHttpResponse_ModelsInterface(t *testing.T) {
 
 func TestConvertHttpResponse_ModelInfoInterface(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	clientAdapter := newMockAdapter("client", false)
 	clientAdapter.supportsIface = map[InterfaceType]bool{InterfaceTypeModelInfo: true}
 	providerAdapter := newMockAdapter("provider", false)

backend/internal/conversion/engine_test.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
 )
 
 // mockProtocolAdapter 模拟协议适配器
@@ -170,14 +171,29 @@ func (e *noopStreamEncoder) Flush() [][]byte
 
 func TestNewConversionEngine(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	assert.NotNil(t, engine)
 	assert.Equal(t, registry, engine.GetRegistry())
 }
 
+func TestNewConversionEngine_LoggerInjection(t *testing.T) {
+	t.Run("nil_logger_uses_global", func(t *testing.T) {
+		registry := NewMemoryRegistry()
+		engine := NewConversionEngine(registry, nil)
+		assert.NotNil(t, engine.logger)
+	})
+
+	t.Run("custom_logger", func(t *testing.T) {
+		registry := NewMemoryRegistry()
+		customLogger := zap.NewNop()
+		engine := NewConversionEngine(registry, customLogger)
+		assert.Equal(t, customLogger, engine.logger)
+	})
+}
+
 func TestRegisterAdapter(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 
 	adapter := newMockAdapter("test-proto", true)
 	err := engine.RegisterAdapter(adapter)
@@ -189,7 +205,7 @@ func TestRegisterAdapter(t *testing.T) {
 
 func TestIsPassthrough_SameProtocol(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	adapter := newMockAdapter("openai", true)
 	_ = engine.RegisterAdapter(adapter)
 
@@ -198,7 +214,7 @@ func TestIsPassthrough_SameProtocol(t *testing.T) {
 
 func TestIsPassthrough_DifferentProtocol(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	_ = engine.RegisterAdapter(newMockAdapter("openai", true))
 	_ = engine.RegisterAdapter(newMockAdapter("anthropic", true))
 
@@ -207,7 +223,7 @@ func TestIsPassthrough_DifferentProtocol(t *testing.T) {
 
 func TestIsPassthrough_NoPassthrough(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	_ = engine.RegisterAdapter(newMockAdapter("custom", false))
 
 	assert.False(t, engine.IsPassthrough("custom", "custom"))
@@ -215,7 +231,7 @@ func TestIsPassthrough_NoPassthrough(t *testing.T) {
 
 func TestDetectInterfaceType(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	adapter := newMockAdapter("test", true)
 	adapter.ifaceType = InterfaceTypeChat
 	_ = engine.RegisterAdapter(adapter)
@@ -227,7 +243,7 @@ func TestDetectInterfaceType(t *testing.T) {
 
 func TestDetectInterfaceType_NonExistentProtocol(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 
 	_, err := engine.DetectInterfaceType("/v1/chat", "nonexistent")
 	assert.Error(t, err)
@@ -235,7 +251,7 @@ func TestDetectInterfaceType_NonExistentProtocol(t *testing.T) {
 
 func TestConvertHttpRequest_Passthrough(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	_ = engine.RegisterAdapter(newMockAdapter("openai", true))
 
 	provider := NewTargetProvider("https://api.openai.com", "sk-test", "gpt-4")
@@ -253,7 +269,7 @@ func TestConvertHttpRequest_Passthrough(t *testing.T) {
 
 func TestConvertHttpRequest_CrossProtocol(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 
 	clientAdapter := newMockAdapter("client-proto", false)
 	clientAdapter.decodeReqFn = func(raw []byte) (*canonical.CanonicalRequest, error) {
@@ -285,7 +301,7 @@ func TestConvertHttpRequest_CrossProtocol(t *testing.T) {
 
 func TestConvertHttpResponse_Passthrough(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	_ = engine.RegisterAdapter(newMockAdapter("openai", true))
 
 	spec := HTTPResponseSpec{
@@ -301,7 +317,7 @@ func TestConvertHttpResponse_Passthrough(t *testing.T) {
 
 func TestCreateStreamConverter_Passthrough(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	_ = engine.RegisterAdapter(newMockAdapter("openai", true))
 
 	converter, err := engine.CreateStreamConverter("openai", "openai")
@@ -312,7 +328,7 @@ func TestCreateStreamConverter_Passthrough(t *testing.T) {
 
 func TestCreateStreamConverter_Canonical(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	_ = engine.RegisterAdapter(newMockAdapter("client", false))
 	_ = engine.RegisterAdapter(newMockAdapter("provider", false))
 
@@ -324,7 +340,7 @@ func TestCreateStreamConverter_Canonical(t *testing.T) {
 
 func TestEncodeError(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 	_ = engine.RegisterAdapter(newMockAdapter("openai", true))
 
 	convErr := NewConversionError(ErrorCodeInvalidInput, "测试错误")
@@ -336,7 +352,7 @@ func TestEncodeError(t *testing.T) {
 
 func TestEncodeError_NonExistentProtocol(t *testing.T) {
 	registry := NewMemoryRegistry()
-	engine := NewConversionEngine(registry)
+	engine := NewConversionEngine(registry, nil)
 
 	convErr := NewConversionError(ErrorCodeInvalidInput, "测试错误")
 	body, statusCode, err := engine.EncodeError(convErr, "nonexistent")

backend/internal/conversion/openai/adapter.go

@@ -2,7 +2,7 @@ package openai
 
 import (
 	"encoding/json"
-	"regexp"
+	"strings"
 
 	"nex/backend/internal/conversion"
 	"nex/backend/internal/conversion/canonical"
@@ -16,8 +16,6 @@ func NewAdapter() *Adapter {
 	return &Adapter{}
 }
 
-var modelInfoRegex = regexp.MustCompile(`^/v1/models/[^/]+$`)
-
 // ProtocolName 返回协议名称
 func (a *Adapter) ProtocolName() string { return "openai" }
 
@@ -34,7 +32,7 @@ func (a *Adapter) DetectInterfaceType(nativePath string) conversion.InterfaceTyp
 		return conversion.InterfaceTypeChat
 	case nativePath == "/v1/models":
 		return conversion.InterfaceTypeModels
-	case modelInfoRegex.MatchString(nativePath):
+	case isModelInfoPath(nativePath):
 		return conversion.InterfaceTypeModelInfo
 	case nativePath == "/v1/embeddings":
 		return conversion.InterfaceTypeEmbeddings
@@ -45,6 +43,15 @@ func (a *Adapter) DetectInterfaceType(nativePath string) conversion.InterfaceTyp
 	}
 }
 
+// isModelInfoPath 判断是否为模型详情路径（/v1/models/{id}）
+func isModelInfoPath(path string) bool {
+	if !strings.HasPrefix(path, "/v1/models/") {
+		return false
+	}
+	suffix := path[len("/v1/models/"):]
+	return suffix != "" && !strings.Contains(suffix, "/")
+}
+
 // BuildUrl 根据接口类型构建 URL
 func (a *Adapter) BuildUrl(nativePath string, interfaceType conversion.InterfaceType) string {
 	switch interfaceType {

backend/internal/conversion/openai/adapter_test.go

@@ -112,6 +112,28 @@ func TestAdapter_SupportsInterface(t *testing.T) {
 	}
 }
 
+func TestIsModelInfoPath(t *testing.T) {
+	tests := []struct {
+		name     string
+		path     string
+		expected bool
+	}{
+		{"model_info", "/v1/models/gpt-4", true},
+		{"model_info_with_dots", "/v1/models/gpt-4.1-preview", true},
+		{"models_list", "/v1/models", false},
+		{"nested_path", "/v1/models/gpt-4/versions", false},
+		{"empty_suffix", "/v1/models/", false},
+		{"unrelated", "/v1/chat/completions", false},
+		{"partial_prefix", "/v1/model", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, isModelInfoPath(tt.path))
+		})
+	}
+}
+
 func TestAdapter_EncodeError_InvalidInput(t *testing.T) {
 	a := NewAdapter()
 	convErr := conversion.NewConversionError(conversion.ErrorCodeInvalidInput, "参数无效")

backend/internal/conversion/openai/encoder.go

@@ -2,6 +2,7 @@ package openai
 
 import (
 	"encoding/json"
+	"strings"
 	"time"
 
 	"nex/backend/internal/conversion"
@@ -89,7 +90,7 @@ func encodeSystemAndMessages(req *canonical.CanonicalRequest) []map[string]any {
 		for _, b := range v {
 			parts = append(parts, b.Text)
 		}
-		text := joinStrings(parts, "\n\n")
+		text := strings.Join(parts, "\n\n")
 		if text != "" {
 			messages = append(messages, map[string]any{
 				"role":    "system",
@@ -132,7 +133,7 @@ func encodeMessage(msg canonical.CanonicalMessage) []map[string]any {
 
 		if len(toolUses) > 0 {
 			if len(textParts) > 0 {
-				m["content"] = joinStrings(textParts, "")
+				m["content"] = strings.Join(textParts, "")
 			} else {
 				m["content"] = nil
 			}
@@ -149,7 +150,7 @@ func encodeMessage(msg canonical.CanonicalMessage) []map[string]any {
 			}
 			m["tool_calls"] = tcs
 		} else if len(textParts) > 0 {
-			m["content"] = joinStrings(textParts, "")
+			m["content"] = strings.Join(textParts, "")
 		} else {
 			m["content"] = ""
 		}
@@ -286,7 +287,7 @@ func encodeResponse(resp *canonical.CanonicalResponse) ([]byte, error) {
 	message := map[string]any{"role": "assistant"}
 	if len(toolUses) > 0 {
 		if len(textParts) > 0 {
-			message["content"] = joinStrings(textParts, "")
+			message["content"] = strings.Join(textParts, "")
 		} else {
 			message["content"] = nil
 		}
@@ -303,13 +304,13 @@ func encodeResponse(resp *canonical.CanonicalResponse) ([]byte, error) {
 		}
 		message["tool_calls"] = tcs
 	} else if len(textParts) > 0 {
-		message["content"] = joinStrings(textParts, "")
+		message["content"] = strings.Join(textParts, "")
 	} else {
 		message["content"] = ""
 	}
 
 	if len(thinkingParts) > 0 {
-		message["reasoning_content"] = joinStrings(thinkingParts, "")
+		message["reasoning_content"] = strings.Join(thinkingParts, "")
 	}
 
 	var finishReason *string
@@ -488,18 +489,6 @@ func encodeRerankResponse(resp *canonical.CanonicalRerankResponse) ([]byte, erro
 	})
 }
 
-// joinStrings 拼接字符串切片
-func joinStrings(parts []string, sep string) string {
-	result := ""
-	for i, p := range parts {
-		if i > 0 {
-			result += sep
-		}
-		result += p
-	}
-	return result
-}
-
 // mergeConsecutiveRoles 合并连续同角色消息（拼接内容）
 func mergeConsecutiveRoles(messages []map[string]any) []map[string]any {
 	if len(messages) <= 1 {

backend/internal/handler/handler_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"gorm.io/gorm"
 
 	"nex/backend/internal/domain"
 	"nex/backend/internal/provider"
@@ -250,3 +251,25 @@ func formatMapErrors(errs map[string]string) string {
 	}
 	return "请求验证失败: " + strings.Join(parts, "; ")
 }
+
+// ============ 错误类型判断测试 ============
+
+func TestProviderHandler_CreateProvider_DuplicatedKey(t *testing.T) {
+	h := NewProviderHandler(&mockProviderService{
+		err: gorm.ErrDuplicatedKey,
+	})
+
+	body, _ := json.Marshal(map[string]string{
+		"id":       "p1",
+		"name":     "Test",
+		"api_key":  "sk-test",
+		"base_url": "https://test.com",
+	})
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest("POST", "/api/providers", bytes.NewReader(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	h.CreateProvider(c)
+	assert.Equal(t, 409, w.Code)
+}

backend/internal/handler/provider_handler.go

@@ -1,8 +1,8 @@
 package handler
 
 import (
+	"errors"
 	"net/http"
-	"strings"
 
 	"github.com/gin-gonic/gin"
 	"gorm.io/gorm"
@@ -55,7 +55,7 @@ func (h *ProviderHandler) CreateProvider(c *gin.Context) {
 
 	err := h.providerService.Create(provider)
 	if err != nil {
-		if strings.Contains(err.Error(), "UNIQUE constraint failed") {
+		if errors.Is(err, gorm.ErrDuplicatedKey) {
 			c.JSON(http.StatusConflict, gin.H{
 				"error": "供应商 ID 已存在",
 			})

backend/internal/handler/proxy_handler.go

@@ -2,6 +2,7 @@ package handler
 
 import (
 	"bufio"
+	"encoding/json"
 	"io"
 	"net/http"
 	"strings"
@@ -213,18 +214,14 @@ func (h *ProxyHandler) isStreamRequest(body []byte, clientProtocol, nativePath s
 	if ifaceType != conversion.InterfaceTypeChat {
 		return false
 	}
-	for i, b := range body {
-		if b == '"' && i+8 <= len(body) {
-			if string(body[i:i+8]) == `"stream"` {
-				for j := i + 8; j < len(body) && j < i+20; j++ {
-					if body[j] == 't' && j+3 < len(body) && string(body[j:j+4]) == "true" {
-						return true
-					}
-				}
-			}
-		}
+
+	var req struct {
+		Stream bool `json:"stream"`
 	}
-	return false
+	if err := json.Unmarshal(body, &req); err != nil {
+		return false
+	}
+	return req.Stream
 }
 
 // writeConversionError 写入转换错误
@@ -312,51 +309,13 @@ func (h *ProxyHandler) forwardPassthrough(c *gin.Context, inSpec conversion.HTTP
 
 // extractModelName 从 JSON body 中提取 model
 func extractModelName(body []byte) string {
-	inQuote := false
-	escaped := false
-	keyStart := -1
-	keyEnd := -1
-	lookingForKey := true
-	lookingForValue := false
-	valueStart := -1
-
-	for i := 0; i < len(body); i++ {
-		b := body[i]
-		if escaped {
-			escaped = false
-			continue
-		}
-		if b == '\\' {
-			escaped = true
-			continue
-		}
-		if b == '"' {
-			if !inQuote {
-				inQuote = true
-				if lookingForKey {
-					keyStart = i + 1
-				}
-				if lookingForValue {
-					valueStart = i + 1
-				}
-			} else {
-				inQuote = false
-				if lookingForKey && keyStart >= 0 {
-					keyEnd = i
-					if string(body[keyStart:keyEnd]) == "model" {
-						lookingForKey = false
-						lookingForValue = true
-					}
-				} else if lookingForValue && valueStart >= 0 {
-					return string(body[valueStart:i])
-				}
-			}
-		}
-		if !inQuote && lookingForValue && b == ':' {
-			// 等待值开始
-		}
+	var req struct {
+		Model string `json:"model"`
 	}
-	return ""
+	if err := json.Unmarshal(body, &req); err != nil {
+		return ""
+	}
+	return req.Model
 }
 
 // extractHeaders 从 Gin context 提取请求头

backend/internal/handler/proxy_handler_test.go

@@ -84,8 +84,9 @@ func (m *mockProxyStatsService) Aggregate(stats []domain.UsageStats, groupBy str
 func setupProxyEngine(t *testing.T) *conversion.ConversionEngine {
 	t.Helper()
 	registry := conversion.NewMemoryRegistry()
-	engine := conversion.NewConversionEngine(registry)
+	engine := conversion.NewConversionEngine(registry, nil)
 	require.NoError(t, registry.Register(openai.NewAdapter()))
+	require.NoError(t, registry.Register(anthropic.NewAdapter()))
 	return engine
 }
 
@@ -321,27 +322,6 @@ func TestProxyHandler_ForwardPassthrough_NoProviders(t *testing.T) {
 	assert.Equal(t, 404, w.Code)
 }
 
-func TestExtractModelName(t *testing.T) {
-	tests := []struct {
-		name string
-		body string
-		want string
-	}{
-		{"basic", `{"model":"gpt-4","messages":[]}`, "gpt-4"},
-		{"nested", `{"stream":true,"model":"claude-3","messages":[]}`, "claude-3"},
-		{"no_model", `{"messages":[]}`, ""},
-		{"empty", "", ""},
-		{"escaped", `{"model":"gpt\"4","messages":[]}`, `gpt\"4`},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			got := extractModelName([]byte(tt.body))
-			assert.Equal(t, tt.want, got)
-		})
-	}
-}
-
 func TestExtractHeaders(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := gin.CreateTestContext(w)
@@ -354,30 +334,6 @@ func TestExtractHeaders(t *testing.T) {
 	assert.Equal(t, "application/json", headers["Content-Type"])
 }
 
-func TestIsStreamRequest(t *testing.T) {
-	engine := setupProxyEngine(t)
-	h := newTestProxyHandler(engine, &mockProxyProviderClient{}, &mockProxyRoutingService{}, &mockProxyProviderService{})
-
-	tests := []struct {
-		name     string
-		body     string
-		path     string
-		expected bool
-	}{
-		{"stream true chat", `{"model":"gpt-4","stream":true}`, "/v1/chat/completions", true},
-		{"stream false chat", `{"model":"gpt-4","stream":false}`, "/v1/chat/completions", false},
-		{"no stream field", `{"model":"gpt-4"}`, "/v1/chat/completions", false},
-		{"stream true non-chat", `{"model":"gpt-4","stream":true}`, "/v1/models", false},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			result := h.isStreamRequest([]byte(tt.body), "openai", tt.path)
-			assert.Equal(t, tt.expected, result)
-		})
-	}
-}
-
 func TestProxyHandler_HandleProxy_ProviderProtocolDefault(t *testing.T) {
 	engine := setupProxyEngine(t)
 	routingSvc := &mockProxyRoutingService{
@@ -529,7 +485,7 @@ func TestProxyHandler_HandleStream_FlushOutput(t *testing.T) {
 
 func TestProxyHandler_HandleStream_CreateStreamConverterError(t *testing.T) {
 	registry := conversion.NewMemoryRegistry()
-	engine := conversion.NewConversionEngine(registry)
+	engine := conversion.NewConversionEngine(registry, nil)
 	err := registry.Register(openai.NewAdapter())
 	require.NoError(t, err)
 
@@ -552,7 +508,7 @@ func TestProxyHandler_HandleStream_CreateStreamConverterError(t *testing.T) {
 
 func TestProxyHandler_HandleStream_ConvertRequestError(t *testing.T) {
 	registry := conversion.NewMemoryRegistry()
-	engine := conversion.NewConversionEngine(registry)
+	engine := conversion.NewConversionEngine(registry, nil)
 	require.NoError(t, registry.Register(openai.NewAdapter()))
 
 	routingSvc := &mockProxyRoutingService{
@@ -574,7 +530,7 @@ func TestProxyHandler_HandleStream_ConvertRequestError(t *testing.T) {
 
 func TestProxyHandler_HandleNonStream_ConvertResponseError(t *testing.T) {
 	registry := conversion.NewMemoryRegistry()
-	engine := conversion.NewConversionEngine(registry)
+	engine := conversion.NewConversionEngine(registry, nil)
 	require.NoError(t, registry.Register(openai.NewAdapter()))
 	require.NoError(t, registry.Register(anthropic.NewAdapter()))
 
@@ -636,7 +592,7 @@ func TestProxyHandler_HandleNonStream_ResponseHeaders(t *testing.T) {
 
 func TestProxyHandler_ForwardPassthrough_CrossProtocol(t *testing.T) {
 	registry := conversion.NewMemoryRegistry()
-	engine := conversion.NewConversionEngine(registry)
+	engine := conversion.NewConversionEngine(registry, nil)
 	require.NoError(t, registry.Register(openai.NewAdapter()))
 
 	anthropicAdapter := anthropic.NewAdapter()
@@ -759,3 +715,119 @@ func TestProxyHandler_HandleProxy_RouteEmptyBody_NoModel(t *testing.T) {
 	h.HandleProxy(c)
 	assert.Equal(t, 200, w.Code)
 }
+
+// ============ extractModelName 测试 ============
+
+func TestExtractModelName(t *testing.T) {
+	tests := []struct {
+		name     string
+		body     []byte
+		expected string
+	}{
+		{
+			name:     "valid model",
+			body:     []byte(`{"model": "gpt-4", "messages": []}`),
+			expected: "gpt-4",
+		},
+		{
+			name:     "empty body",
+			body:     []byte(`{}`),
+			expected: "",
+		},
+		{
+			name:     "invalid json",
+			body:     []byte(`{invalid}`),
+			expected: "",
+		},
+		{
+			name:     "nested structure",
+			body:     []byte(`{"model": "claude-3", "messages": [{"role": "user", "content": "hello"}]}`),
+			expected: "claude-3",
+		},
+		{
+			name:     "model with special chars",
+			body:     []byte(`{"model": "gpt-4-0125-preview", "stream": true}`),
+			expected: "gpt-4-0125-preview",
+		},
+		{
+			name:     "empty body bytes",
+			body:     []byte{},
+			expected: "",
+		},
+		{
+			name:     "model is null",
+			body:     []byte(`{"model": null}`),
+			expected: "",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := extractModelName(tt.body)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+// ============ isStreamRequest 测试 ============
+
+func TestIsStreamRequest(t *testing.T) {
+	engine := setupProxyEngine(t)
+	h := &ProxyHandler{engine: engine}
+
+	tests := []struct {
+		name           string
+		body           []byte
+		clientProtocol string
+		nativePath     string
+		expected       bool
+	}{
+		{
+			name:           "stream true",
+			body:           []byte(`{"model": "gpt-4", "stream": true}`),
+			clientProtocol: "openai",
+			nativePath:     "/v1/chat/completions",
+			expected:       true,
+		},
+		{
+			name:           "stream false",
+			body:           []byte(`{"model": "gpt-4", "stream": false}`),
+			clientProtocol: "openai",
+			nativePath:     "/v1/chat/completions",
+			expected:       false,
+		},
+		{
+			name:           "no stream field",
+			body:           []byte(`{"model": "gpt-4"}`),
+			clientProtocol: "openai",
+			nativePath:     "/v1/chat/completions",
+			expected:       false,
+		},
+		{
+			name:           "invalid json",
+			body:           []byte(`{invalid}`),
+			clientProtocol: "openai",
+			nativePath:     "/v1/chat/completions",
+			expected:       false,
+		},
+		{
+			name:           "not chat endpoint",
+			body:           []byte(`{"model": "gpt-4", "stream": true}`),
+			clientProtocol: "openai",
+			nativePath:     "/v1/models",
+			expected:       false,
+		},
+		{
+			name:           "anthropic stream",
+			body:           []byte(`{"model": "claude-3", "stream": true}`),
+			clientProtocol: "anthropic",
+			nativePath:     "/v1/messages",
+			expected:       true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := h.isStreamRequest(tt.body, tt.clientProtocol, tt.nativePath)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}

backend/internal/handler/stats_handler.go

@@ -1,6 +1,7 @@
 package handler
 
 import (
+	"fmt"
 	"net/http"
 	"time"
 
@@ -23,31 +24,16 @@ func NewStatsHandler(statsService service.StatsService) *StatsHandler {
 func (h *StatsHandler) GetStats(c *gin.Context) {
 	providerID := c.Query("provider_id")
 	modelName := c.Query("model_name")
-	startDateStr := c.Query("start_date")
-	endDateStr := c.Query("end_date")
 
-	var startDate, endDate *time.Time
-
-	if startDateStr != "" {
-		t, err := time.Parse("2006-01-02", startDateStr)
-		if err != nil {
-			c.JSON(http.StatusBadRequest, gin.H{
-				"error": "无效的 start_date 格式，应为 YYYY-MM-DD",
-			})
-			return
-		}
-		startDate = &t
+	startDate, err := parseDateParam(c, "start_date")
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
 	}
-
-	if endDateStr != "" {
-		t, err := time.Parse("2006-01-02", endDateStr)
-		if err != nil {
-			c.JSON(http.StatusBadRequest, gin.H{
-				"error": "无效的 end_date 格式，应为 YYYY-MM-DD",
-			})
-			return
-		}
-		endDate = &t
+	endDate, err := parseDateParam(c, "end_date")
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
 	}
 
 	stats, err := h.statsService.Get(providerID, modelName, startDate, endDate)
@@ -65,32 +51,17 @@ func (h *StatsHandler) GetStats(c *gin.Context) {
 func (h *StatsHandler) AggregateStats(c *gin.Context) {
 	providerID := c.Query("provider_id")
 	modelName := c.Query("model_name")
-	startDateStr := c.Query("start_date")
-	endDateStr := c.Query("end_date")
 	groupBy := c.Query("group_by")
 
-	var startDate, endDate *time.Time
-
-	if startDateStr != "" {
-		t, err := time.Parse("2006-01-02", startDateStr)
-		if err != nil {
-			c.JSON(http.StatusBadRequest, gin.H{
-				"error": "无效的 start_date 格式，应为 YYYY-MM-DD",
-			})
-			return
-		}
-		startDate = &t
+	startDate, err := parseDateParam(c, "start_date")
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
 	}
-
-	if endDateStr != "" {
-		t, err := time.Parse("2006-01-02", endDateStr)
-		if err != nil {
-			c.JSON(http.StatusBadRequest, gin.H{
-				"error": "无效的 end_date 格式，应为 YYYY-MM-DD",
-			})
-			return
-		}
-		endDate = &t
+	endDate, err := parseDateParam(c, "end_date")
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
 	}
 
 	stats, err := h.statsService.Get(providerID, modelName, startDate, endDate)
@@ -104,3 +75,16 @@ func (h *StatsHandler) AggregateStats(c *gin.Context) {
 	result := h.statsService.Aggregate(stats, groupBy)
 	c.JSON(http.StatusOK, result)
 }
+
+// parseDateParam 解析日期查询参数
+func parseDateParam(c *gin.Context, paramName string) (*time.Time, error) {
+	dateStr := c.Query(paramName)
+	if dateStr == "" {
+		return nil, nil
+	}
+	t, err := time.Parse("2006-01-02", dateStr)
+	if err != nil {
+		return nil, fmt.Errorf("无效的 %s 格式，应为 YYYY-MM-DD", paramName)
+	}
+	return &t, nil
+}

backend/internal/handler/stats_handler_test.go

@@ -0,0 +1,61 @@
+package handler
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseDateParam(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	t.Run("valid_date", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodGet, "/?start_date=2024-01-15", nil)
+
+		result, err := parseDateParam(c, "start_date")
+		assert.NoError(t, err)
+		assert.NotNil(t, result)
+		expected := time.Date(2024, 1, 15, 0, 0, 0, 0, time.UTC)
+		assert.Equal(t, expected, *result)
+	})
+
+	t.Run("empty_param", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodGet, "/", nil)
+
+		result, err := parseDateParam(c, "start_date")
+		assert.NoError(t, err)
+		assert.Nil(t, result)
+	})
+
+	t.Run("invalid_format", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodGet, "/?start_date=2024/01/15", nil)
+
+		result, err := parseDateParam(c, "start_date")
+		assert.Error(t, err)
+		assert.Nil(t, result)
+		assert.Contains(t, err.Error(), "start_date")
+		assert.Contains(t, err.Error(), "YYYY-MM-DD")
+	})
+
+	t.Run("end_date", func(t *testing.T) {
+		w := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(w)
+		c.Request = httptest.NewRequest(http.MethodGet, "/?end_date=2024-12-31", nil)
+
+		result, err := parseDateParam(c, "end_date")
+		assert.NoError(t, err)
+		assert.NotNil(t, result)
+		expected := time.Date(2024, 12, 31, 0, 0, 0, 0, time.UTC)
+		assert.Equal(t, expected, *result)
+	})
+}

backend/internal/provider/client.go

@@ -3,15 +3,18 @@ package provider
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
-	"strings"
+	"syscall"
 	"time"
 
 	"go.uber.org/zap"
 
 	"nex/backend/internal/conversion"
+	pkgErrors "nex/backend/pkg/errors"
 )
 
 // StreamConfig 流式处理配置
@@ -72,7 +75,7 @@ func (c *Client) Send(ctx context.Context, spec conversion.HTTPRequestSpec) (*co
 
 	httpReq, err := http.NewRequestWithContext(ctx, spec.Method, spec.URL, bodyReader)
 	if err != nil {
-		return nil, fmt.Errorf("创建请求失败: %w", err)
+		return nil, pkgErrors.ErrRequestCreate.WithCause(err)
 	}
 
 	for k, v := range spec.Headers {
@@ -86,13 +89,13 @@ func (c *Client) Send(ctx context.Context, spec conversion.HTTPRequestSpec) (*co
 
 	resp, err := c.httpClient.Do(httpReq)
 	if err != nil {
-		return nil, fmt.Errorf("发送请求失败: %w", err)
+		return nil, pkgErrors.ErrRequestSend.WithCause(err)
 	}
 	defer resp.Body.Close()
 
 	respBody, err := io.ReadAll(resp.Body)
 	if err != nil {
-		return nil, fmt.Errorf("读取响应失败: %w", err)
+		return nil, pkgErrors.ErrResponseRead.WithCause(err)
 	}
 
 	respHeaders := make(map[string]string)
@@ -120,7 +123,7 @@ func (c *Client) SendStream(ctx context.Context, spec conversion.HTTPRequestSpec
 	httpReq, err := http.NewRequestWithContext(streamCtx, spec.Method, spec.URL, bodyReader)
 	if err != nil {
 		cancel()
-		return nil, fmt.Errorf("创建请求失败: %w", err)
+		return nil, pkgErrors.ErrRequestCreate.WithCause(err)
 	}
 
 	for k, v := range spec.Headers {
@@ -130,7 +133,7 @@ func (c *Client) SendStream(ctx context.Context, spec conversion.HTTPRequestSpec
 	resp, err := c.httpClient.Do(httpReq)
 	if err != nil {
 		cancel()
-		return nil, fmt.Errorf("发送请求失败: %w", err)
+		return nil, pkgErrors.ErrRequestSend.WithCause(err)
 	}
 
 	if resp.StatusCode != http.StatusOK {
@@ -226,10 +229,46 @@ func isNetworkError(err error) bool {
 	if err == nil {
 		return false
 	}
-	errStr := err.Error()
-	return strings.Contains(errStr, "connection reset") ||
-		strings.Contains(errStr, "broken pipe") ||
-		strings.Contains(errStr, "network") ||
-		strings.Contains(errStr, "timeout") ||
-		strings.Contains(errStr, "EOF")
+
+	// 检查标准库定义的网络错误类型
+	var netErr net.Error
+	if errors.As(err, &netErr) {
+		return true
+	}
+
+	// 检查操作错误
+	var opErr *net.OpError
+	if errors.As(err, &opErr) {
+		// 检查具体的系统错误
+		if opErr.Err != nil {
+			// 连接重置
+			if errors.Is(opErr.Err, syscall.ECONNRESET) {
+				return true
+			}
+			// 断管
+			if errors.Is(opErr.Err, syscall.EPIPE) {
+				return true
+			}
+			// 超时
+			if errors.Is(opErr.Err, syscall.ETIMEDOUT) {
+				return true
+			}
+		}
+		return true
+	}
+
+	// 检查上下文错误
+	if errors.Is(err, context.DeadlineExceeded) {
+		return true
+	}
+	if errors.Is(err, context.Canceled) {
+		return true
+	}
+
+	// 检查 EOF
+	if errors.Is(err, io.EOF) {
+		return true
+	}
+
+	return false
 }

backend/internal/provider/client_test.go

@@ -2,9 +2,12 @@ package provider
 
 import (
 	"context"
-	"fmt"
+	"errors"
+	"io"
+	"net"
 	"net/http"
 	"net/http/httptest"
+	"syscall"
 	"testing"
 	"time"
 
@@ -309,22 +312,49 @@ func TestClient_SendStream_SplitSSEEvents(t *testing.T) {
 }
 
 func TestIsNetworkError(t *testing.T) {
-	tests := []struct {
-		input string
-		want  bool
-	}{
-		{"connection reset by peer", true},
-		{"broken pipe", true},
-		{"network is unreachable", true},
-		{"timeout waiting for response", true},
-		{"unexpected EOF", true},
-		{"normal error", false},
-		{"", false},
-	}
-	for _, tt := range tests {
-		err := fmt.Errorf("%s", tt.input)
-		assert.Equal(t, tt.want, isNetworkError(err), "isNetworkError(%q)", tt.input)
-	}
+	// 测试 net.Error 类型
+	t.Run("net_error", func(t *testing.T) {
+		var netErr net.Error
+		err := context.DeadlineExceeded
+		assert.True(t, errors.As(err, &netErr))
+		assert.True(t, isNetworkError(err))
+	})
+
+	// 测试 io.EOF
+	t.Run("io_eof", func(t *testing.T) {
+		assert.True(t, isNetworkError(io.EOF))
+	})
+
+	// 测试 context 错误
+	t.Run("context_errors", func(t *testing.T) {
+		assert.True(t, isNetworkError(context.DeadlineExceeded))
+		assert.True(t, isNetworkError(context.Canceled))
+	})
+
+	// 测试 syscall 错误（包装在 net.OpError 中）
+	t.Run("syscall_errors", func(t *testing.T) {
+		// ECONNRESET
+		opErr := &net.OpError{
+			Op:  "read",
+			Net: "tcp",
+			Err: syscall.ECONNRESET,
+		}
+		assert.True(t, isNetworkError(opErr))
+
+		// EPIPE
+		opErr = &net.OpError{
+			Op:  "write",
+			Net: "tcp",
+			Err: syscall.EPIPE,
+		}
+		assert.True(t, isNetworkError(opErr))
+	})
+
+	// 测试普通错误
+	t.Run("normal_error", func(t *testing.T) {
+		assert.False(t, isNetworkError(errors.New("normal error")))
+		assert.False(t, isNetworkError(nil))
+	})
 }
 
 func TestClient_SendStream_MidStreamNetworkError(t *testing.T) {

backend/internal/service/service_supplemental_test.go

@@ -104,26 +104,6 @@ func TestModelService_Delete_NotFound(t *testing.T) {
 	assert.Error(t, err)
 }
 
-func TestStatsService_Aggregate_ByModel(t *testing.T) {
-	statsRepo := repository.NewStatsRepository(nil)
-	svc := NewStatsService(statsRepo)
-
-	stats := []domain.UsageStats{
-		{ProviderID: "p1", ModelName: "gpt-4", RequestCount: 10},
-		{ProviderID: "p1", ModelName: "gpt-4", RequestCount: 5},
-		{ProviderID: "p2", ModelName: "gpt-4", RequestCount: 8},
-	}
-
-	result := svc.Aggregate(stats, "model")
-	assert.True(t, len(result) >= 1)
-
-	totalCount := 0
-	for _, r := range result {
-		totalCount += r["request_count"].(int)
-	}
-	assert.Equal(t, 23, totalCount)
-}
-
 func TestStatsService_Aggregate_Default(t *testing.T) {
 	statsRepo := repository.NewStatsRepository(nil)
 	svc := NewStatsService(statsRepo)

backend/internal/service/service_test.go

@@ -243,3 +243,28 @@ func TestStatsService_Aggregate_ByDate(t *testing.T) {
 	assert.Len(t, result, 1)
 	assert.Equal(t, 15, result[0]["request_count"])
 }
+
+func TestStatsService_Aggregate_ByModel(t *testing.T) {
+	statsRepo := repository.NewStatsRepository(nil)
+	svc := NewStatsService(statsRepo)
+
+	stats := []domain.UsageStats{
+		{ProviderID: "openai", ModelName: "gpt-4", RequestCount: 10},
+		{ProviderID: "openai", ModelName: "gpt-3.5", RequestCount: 5},
+		{ProviderID: "anthropic", ModelName: "claude-3", RequestCount: 8},
+		{ProviderID: "openai", ModelName: "gpt-4", RequestCount: 3},
+	}
+
+	result := svc.Aggregate(stats, "model")
+	assert.Len(t, result, 3)
+
+	// 验证每个 provider/model 组合的计数
+	counts := make(map[string]int)
+	for _, r := range result {
+		key := r["provider_id"].(string) + "/" + r["model_name"].(string)
+		counts[key] = r["request_count"].(int)
+	}
+	assert.Equal(t, 13, counts["openai/gpt-4"])
+	assert.Equal(t, 5, counts["openai/gpt-3.5"])
+	assert.Equal(t, 8, counts["anthropic/claude-3"])
+}

backend/internal/service/stats_service_impl.go

@@ -1,6 +1,7 @@
 package service
 
 import (
+	"strings"
 	"time"
 
 	"nex/backend/internal/domain"
@@ -59,9 +60,10 @@ func (s *statsService) aggregateByModel(stats []domain.UsageStats) []map[string]
 	}
 	result := make([]map[string]interface{}, 0, len(aggregated))
 	for key, count := range aggregated {
+		parts := strings.SplitN(key, "/", 2)
 		result = append(result, map[string]interface{}{
-			"provider_id":   key[:len(key)/2],
-			"model_name":    key[len(key)/2+1:],
+			"provider_id":   parts[0],
+			"model_name":    parts[1],
 			"request_count": count,
 		})
 	}

backend/pkg/errors/errors.go

@@ -27,6 +27,17 @@ func (e *AppError) Unwrap() error {
 	return e.Cause
 }
 
+// WithCause returns a copy of the error with the given cause
+func (e *AppError) WithCause(cause error) *AppError {
+	return &AppError{
+		Code:       e.Code,
+		Message:    e.Message,
+		HTTPStatus: e.HTTPStatus,
+		Cause:      cause,
+		Context:    e.Context,
+	}
+}
+
 // NewAppError creates a new AppError
 func NewAppError(code, message string, httpStatus int) *AppError {
 	return &AppError{
@@ -46,6 +57,9 @@ var (
 	ErrInternal         = NewAppError("internal_error", "内部错误", http.StatusInternalServerError)
 	ErrDatabaseNotInit  = NewAppError("database_not_initialized", "数据库未初始化", http.StatusInternalServerError)
 	ErrConflict         = NewAppError("conflict", "资源已存在", http.StatusConflict)
+	ErrRequestCreate    = NewAppError("request_create_error", "创建请求失败", http.StatusInternalServerError)
+	ErrRequestSend      = NewAppError("request_send_error", "发送请求失败", http.StatusBadGateway)
+	ErrResponseRead     = NewAppError("response_read_error", "读取响应失败", http.StatusBadGateway)
 )
 
 // AsAppError 尝试将 error 转换为 *AppError

backend/pkg/errors/errors_test.go

@@ -90,6 +90,9 @@ func TestPredefinedErrors(t *testing.T) {
 		{"ErrInternal", ErrInternal, "internal_error", http.StatusInternalServerError},
 		{"ErrDatabaseNotInit", ErrDatabaseNotInit, "database_not_initialized", http.StatusInternalServerError},
 		{"ErrConflict", ErrConflict, "conflict", http.StatusConflict},
+		{"ErrRequestCreate", ErrRequestCreate, "request_create_error", http.StatusInternalServerError},
+		{"ErrRequestSend", ErrRequestSend, "request_send_error", http.StatusBadGateway},
+		{"ErrResponseRead", ErrResponseRead, "response_read_error", http.StatusBadGateway},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -123,3 +126,16 @@ func TestAsAppError(t *testing.T) {
 		assert.False(t, ok)
 	})
 }
+
+func TestWithCause(t *testing.T) {
+	cause := errors.New("连接超时")
+	err := ErrRequestSend.WithCause(cause)
+	assert.Equal(t, "request_send_error", err.Code)
+	assert.Equal(t, http.StatusBadGateway, err.HTTPStatus)
+	assert.Equal(t, cause, err.Cause)
+	assert.True(t, errors.Is(err, cause))
+
+	var appErr *AppError
+	assert.True(t, errors.As(err, &appErr))
+	assert.Equal(t, "request_send_error", appErr.Code)
+}

backend/tests/integration/conversion_test.go

@@ -69,7 +69,7 @@ func setupConversionTest(t *testing.T) (*gin.Engine, *gorm.DB, *httptest.Server)
 	registry := conversion.NewMemoryRegistry()
 	require.NoError(t, registry.Register(openaiConv.NewAdapter()))
 	require.NoError(t, registry.Register(anthropic.NewAdapter()))
-	engine := conversion.NewConversionEngine(registry)
+	engine := conversion.NewConversionEngine(registry, nil)
 
 	providerClient := provider.NewClient()
 	proxyHandler := handler.NewProxyHandler(engine, providerClient, routingService, providerService, statsService)

backend/tests/integration/e2e_conversion_test.go

@@ -66,7 +66,7 @@ func setupE2ETest(t *testing.T) (*gin.Engine, *httptest.Server) {
 	registry := conversion.NewMemoryRegistry()
 	require.NoError(t, registry.Register(openaiConv.NewAdapter()))
 	require.NoError(t, registry.Register(anthropic.NewAdapter()))
-	engine := conversion.NewConversionEngine(registry)
+	engine := conversion.NewConversionEngine(registry, nil)
 
 	providerClient := provider.NewClient()
 	proxyHandler := handler.NewProxyHandler(engine, providerClient, routingService, providerService, statsService)