Merge pull request #1799 from IanShaw027/rebuild/auth-identity-foundation

fix(auth,payment,profile): 修复认证身份和支付系统的后续问题

.github/workflows/backend-ci.yml

@@ -28,6 +28,26 @@ jobs:
         working-directory: backend
         run: make test-integration
 
+  frontend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 9
+      - name: Setup Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: '20'
+          cache: 'pnpm'
+          cache-dependency-path: frontend/pnpm-lock.yaml
+      - name: Install frontend dependencies
+        working-directory: frontend
+        run: pnpm install --frozen-lockfile
+      - name: Frontend typecheck and critical vitest
+        run: make test-frontend
+
   golangci-lint:
     runs-on: ubuntu-latest
     steps:

Makefile

-.PHONY: build build-backend build-frontend build-datamanagementd test test-backend test-frontend test-datamanagementd secret-scan
+.PHONY: build build-backend build-frontend build-datamanagementd test test-backend test-frontend test-frontend-critical test-datamanagementd secret-scan
+
+FRONTEND_CRITICAL_VITEST := \
+	src/views/auth/__tests__/LinuxDoCallbackView.spec.ts \
+	src/views/auth/__tests__/WechatCallbackView.spec.ts \
+	src/views/user/__tests__/PaymentView.spec.ts \
+	src/views/user/__tests__/PaymentResultView.spec.ts \
+	src/components/user/profile/__tests__/ProfileInfoCard.spec.ts \
+	src/views/admin/__tests__/SettingsView.spec.ts
 
 # 一键编译前后端
 build: build-backend build-frontend
@@ -24,6 +32,10 @@ test-backend:
 test-frontend:
 	@pnpm --dir frontend run lint:check
 	@pnpm --dir frontend run typecheck
+	@$(MAKE) test-frontend-critical
+
+test-frontend-critical:
+	@pnpm --dir frontend exec vitest run $(FRONTEND_CRITICAL_VITEST)
 
 test-datamanagementd:
 	@cd datamanagement && go test ./...

README.md

@@ -42,10 +42,18 @@ Sub2API is an AI API gateway platform designed to distribute and manage API quot
 - **Smart Scheduling** - Intelligent account selection with sticky sessions
 - **Concurrency Control** - Per-user and per-account concurrency limits
 - **Rate Limiting** - Configurable request and token rate limits
-- **Built-in Payment System** - Supports EasyPay, Alipay, WeChat Pay, and Stripe for user self-service top-up, no separate payment service needed ([Configuration Guide](docs/PAYMENT.md))
+- **Built-in Payment System** - Supports EasyPay, Alipay, WeChat Pay, and Stripe for user self-service top-up, no separate payment service needed ([Payment Setup](#payment))
 - **Admin Dashboard** - Web interface for monitoring and management
 - **External System Integration** - Embed external systems (e.g. ticketing) via iframe to extend the admin dashboard
 
+## Payment
+
+Sub2API includes the payment system in the main service. No standalone payment service or separate payment guide is required.
+
+- Supported providers: EasyPay, Alipay, WeChat Pay, Stripe
+- The frontend keeps user-facing methods unified; admins choose the backing source in `Admin -> Settings -> Payment`
+- Callback URLs are generated from the site domain when configuring providers
+
 ## ❤️ Sponsors
 
 > [Want to appear here?](mailto:support@pincc.ai)
@@ -109,7 +117,7 @@ Community projects that extend or integrate with Sub2API:
 
 | Project | Description | Features |
 |---------|-------------|----------|
-| ~~[Sub2ApiPay](https://github.com/touwaeriol/sub2apipay)~~ | ~~Self-service payment system~~ | **Now Built-in** — Payment is now integrated into Sub2API, no separate deployment needed. See [Payment Configuration Guide](docs/PAYMENT.md) |
+| ~~[Sub2ApiPay](https://github.com/touwaeriol/sub2apipay)~~ | ~~Self-service payment system~~ | **Now Built-in** — Payment is now integrated into Sub2API, no separate deployment needed. See [Payment Setup](#payment) |
 | [sub2api-mobile](https://github.com/ckken/sub2api-mobile) | Mobile admin console | Cross-platform app (iOS/Android/Web) for user management, account management, monitoring dashboard, and multi-backend switching; built with Expo + React Native |
 
 ## Tech Stack

README_CN.md

@@ -41,10 +41,18 @@ Sub2API 是一个 AI API 网关平台，用于分发和管理 AI 产品订阅的
 - **智能调度** - 智能账号选择，支持粘性会话
 - **并发控制** - 用户级和账号级并发限制
 - **速率限制** - 可配置的请求和 Token 速率限制
-- **内置支付系统** - 支持 EasyPay 易支付、支付宝官方、微信官方、Stripe，用户自助充值，无需独立部署支付服务（[配置指南](docs/PAYMENT_CN.md)）
+- **内置支付系统** - 支持 EasyPay 易支付、支付宝官方、微信官方、Stripe，用户自助充值，无需独立部署支付服务（[支付说明](#支付)）
 - **管理后台** - Web 界面进行监控和管理
 - **外部系统集成** - 支持通过 iframe 嵌入外部系统（如工单等），扩展管理后台功能
 
+## 支付
+
+Sub2API 已将支付系统集成到主服务中，无需独立支付服务，也不再依赖单独的支付配置文档。
+
+- 支持服务商：EasyPay 易支付、支付宝官方、微信官方、Stripe
+- 前台统一展示用户可见支付方式，管理员在 `管理后台 -> 设置 -> 支付` 里选择对应来源
+- 添加服务商时会基于站点域名生成回调地址
+
 ## ❤️ 赞助商
 
 > [想出现在这里？](mailto:support@pincc.ai)
@@ -108,7 +116,7 @@ Sub2API 是一个 AI API 网关平台，用于分发和管理 AI 产品订阅的
 
 | 项目 | 说明 | 功能 |
 |------|------|------|
-| ~~[Sub2ApiPay](https://github.com/touwaeriol/sub2apipay)~~ | ~~自助支付系统~~ | **已内置** — 支付功能已集成到 Sub2API 中，无需独立部署。详见 [支付配置指南](docs/PAYMENT_CN.md) |
+| ~~[Sub2ApiPay](https://github.com/touwaeriol/sub2apipay)~~ | ~~自助支付系统~~ | **已内置** — 支付功能已集成到 Sub2API 中，无需独立部署。详见 [支付说明](#支付) |
 | [sub2api-mobile](https://github.com/ckken/sub2api-mobile) | 移动端管理控制台 | 跨平台应用（iOS/Android/Web），支持用户管理、账号管理、监控看板、多后端切换；基于 Expo + React Native 构建 |
 
 ## 技术栈

README_JA.md

@@ -42,10 +42,18 @@ Sub2API は、AI 製品のサブスクリプションから API クォータを
 - **スマートスケジューリング** - スティッキーセッション付きのインテリジェントなアカウント選択
 - **同時実行制御** - ユーザーごと・アカウントごとの同時実行数制限
 - **レート制限** - 設定可能なリクエスト数およびトークンレート制限
-- **内蔵決済システム** - EasyPay、Alipay、WeChat Pay、Stripe に対応。ユーザーのセルフサービスチャージが可能で、別途決済サービスのデプロイは不要（[設定ガイド](docs/PAYMENT.md)）
+- **内蔵決済システム** - EasyPay、Alipay、WeChat Pay、Stripe に対応。ユーザーのセルフサービスチャージが可能で、別途決済サービスのデプロイは不要（[決済案内](#決済)）
 - **管理ダッシュボード** - 監視・管理のための Web インターフェース
 - **外部システム連携** - 外部システム（チケット管理など）を iframe 経由で管理ダッシュボードに埋め込み可能
 
+## 決済
+
+Sub2API の決済機能は本体に統合されています。独立した決済サービスや別個の決済ガイドは不要です。
+
+- 対応プロバイダー: EasyPay、Alipay、WeChat Pay、Stripe
+- フロントエンドではユーザー向け決済方法を統一表示し、管理者は `管理画面 -> 設定 -> 決済` で実際の接続先を選択します
+- プロバイダー設定時のコールバック URL はサイトドメインから自動生成されます
+
 ## ❤️ スポンサー
 
 > [こちらに掲載しませんか？](mailto:support@pincc.ai)
@@ -108,7 +116,7 @@ Sub2API を拡張・統合するコミュニティプロジェクト:
 
 | プロジェクト | 説明 | 機能 |
 |---------|-------------|----------|
-| ~~[Sub2ApiPay](https://github.com/touwaeriol/sub2apipay)~~ | ~~セルフサービス決済システム~~ | **内蔵済み** — 決済機能は Sub2API に統合されました。別途デプロイは不要です。[決済設定ガイド](docs/PAYMENT.md)をご参照ください |
+| ~~[Sub2ApiPay](https://github.com/touwaeriol/sub2apipay)~~ | ~~セルフサービス決済システム~~ | **内蔵済み** — 決済機能は Sub2API に統合されました。別途デプロイは不要です。[決済案内](#決済)をご参照ください |
 | [sub2api-mobile](https://github.com/ckken/sub2api-mobile) | モバイル管理コンソール | ユーザー管理、アカウント管理、監視ダッシュボード、マルチバックエンド切り替えが可能なクロスプラットフォームアプリ（iOS/Android/Web）。Expo + React Native で構築 |
 
 ## 技術スタック

backend/ent/migrate/auth_identity_fk_ondelete_test.go

+package migrate
+
+import (
+	"testing"
+
+	"entgo.io/ent/dialect/entsql"
+	entschema "entgo.io/ent/dialect/sql/schema"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAuthIdentityFoundationForeignKeyOnDeleteActions(t *testing.T) {
+	require.Equal(
+		t,
+		entschema.Cascade,
+		findForeignKeyBySymbol(t, AuthIdentitiesTable, "auth_identities_users_auth_identities").OnDelete,
+	)
+	require.Equal(
+		t,
+		entschema.Cascade,
+		findForeignKeyBySymbol(t, AuthIdentityChannelsTable, "auth_identity_channels_auth_identities_channels").OnDelete,
+	)
+	require.Equal(
+		t,
+		entschema.Cascade,
+		findForeignKeyBySymbol(t, IdentityAdoptionDecisionsTable, "identity_adoption_decisions_pending_auth_sessions_adoption_decision").OnDelete,
+	)
+
+	require.Equal(
+		t,
+		entschema.SetNull,
+		findForeignKeyBySymbol(t, PendingAuthSessionsTable, "pending_auth_sessions_users_pending_auth_sessions").OnDelete,
+	)
+	require.Equal(
+		t,
+		entschema.SetNull,
+		findForeignKeyBySymbol(t, IdentityAdoptionDecisionsTable, "identity_adoption_decisions_auth_identities_adoption_decisions").OnDelete,
+	)
+}
+
+func TestPaymentOrdersOutTradeNoPartialUniqueIndex(t *testing.T) {
+	idx := findIndexByName(t, PaymentOrdersTable, "paymentorder_out_trade_no")
+	require.True(t, idx.Unique)
+	require.Len(t, idx.Columns, 1)
+	require.Equal(t, "out_trade_no", idx.Columns[0].Name)
+	require.NotNil(t, idx.Annotation)
+	require.Equal(t, (&entsql.IndexAnnotation{Where: "out_trade_no <> ''"}).Where, idx.Annotation.Where)
+}
+
+func findForeignKeyBySymbol(t *testing.T, table *entschema.Table, symbol string) *entschema.ForeignKey {
+	t.Helper()
+
+	for _, fk := range table.ForeignKeys {
+		if fk.Symbol == symbol {
+			return fk
+		}
+	}
+
+	require.Failf(t, "missing foreign key", "table %s should include foreign key %s", table.Name, symbol)
+	return nil
+}
+
+func findIndexByName(t *testing.T, table *entschema.Table, name string) *entschema.Index {
+	t.Helper()
+
+	for _, idx := range table.Indexes {
+		if idx.Name == name {
+			return idx
+		}
+	}
+
+	require.Failf(t, "missing index", "table %s should include index %s", table.Name, name)
+	return nil
+}

backend/ent/migrate/schema.go

@@ -361,7 +361,7 @@ var (
 				Symbol:     "auth_identities_users_auth_identities",
 				Columns:    []*schema.Column{AuthIdentitiesColumns[9]},
 				RefColumns: []*schema.Column{UsersColumns[0]},
-				OnDelete:   schema.NoAction,
+				OnDelete:   schema.Cascade,
 			},
 		},
 		Indexes: []*schema.Index{
@@ -405,7 +405,7 @@ var (
 				Symbol:     "auth_identity_channels_auth_identities_channels",
 				Columns:    []*schema.Column{AuthIdentityChannelsColumns[9]},
 				RefColumns: []*schema.Column{AuthIdentitiesColumns[0]},
-				OnDelete:   schema.NoAction,
+				OnDelete:   schema.Cascade,
 			},
 		},
 		Indexes: []*schema.Index{
@@ -595,7 +595,7 @@ var (
 				Symbol:     "identity_adoption_decisions_pending_auth_sessions_adoption_decision",
 				Columns:    []*schema.Column{IdentityAdoptionDecisionsColumns[7]},
 				RefColumns: []*schema.Column{PendingAuthSessionsColumns[0]},
-				OnDelete:   schema.NoAction,
+				OnDelete:   schema.Cascade,
 			},
 		},
 		Indexes: []*schema.Index{
@@ -692,8 +692,11 @@ var (
 		Indexes: []*schema.Index{
 			{
 				Name:    "paymentorder_out_trade_no",
-				Unique:  false,
+				Unique:  true,
 				Columns: []*schema.Column{PaymentOrdersColumns[8]},
+				Annotation: &entsql.IndexAnnotation{
+					Where: "out_trade_no <> ''",
+				},
 			},
 			{
 				Name:    "paymentorder_user_id",

backend/ent/schema/auth_identity.go

@@ -79,7 +79,8 @@ func (AuthIdentity) Edges() []ent.Edge {
 			Field("user_id").
 			Required().
 			Unique(),
-		edge.To("channels", AuthIdentityChannel.Type),
+		edge.To("channels", AuthIdentityChannel.Type).
+			Annotations(entsql.OnDelete(entsql.Cascade)),
 		edge.To("adoption_decisions", IdentityAdoptionDecision.Type),
 	}
 }

backend/ent/schema/auth_identity_schema_test.go

@@ -3,7 +3,9 @@ package schema
 import (
 	"testing"
 
+	"entgo.io/ent"
 	"entgo.io/ent/entc/load"
+	"entgo.io/ent/schema/field"
 	"github.com/stretchr/testify/require"
 )
 
@@ -74,6 +76,17 @@ func TestAuthIdentityFoundationSchemas(t *testing.T) {
 
 	userSchema := requireSchema(t, schemas, "User")
 	requireSchemaFields(t, userSchema, "signup_source", "last_login_at", "last_active_at")
+	signupSource := requireSchemaField(t, userSchema, "signup_source")
+	require.Equal(t, field.TypeString, signupSource.Info.Type)
+	require.True(t, signupSource.Default)
+	require.Equal(t, "email", signupSource.DefaultValue)
+	require.Equal(t, 1, signupSource.Validators)
+
+	validator := requireStringFieldValidator(t, User{}.Fields(), "signup_source")
+	for _, value := range []string{"email", "linuxdo", "wechat", "oidc"} {
+		require.NoError(t, validator(value))
+	}
+	require.Error(t, validator("github"))
 }
 
 func requireSchema(t *testing.T, schemas map[string]*load.Schema, name string) *load.Schema {
@@ -98,6 +111,37 @@ func requireSchemaFields(t *testing.T, schema *load.Schema, names ...string) {
 	}
 }
 
+func requireSchemaField(t *testing.T, schema *load.Schema, name string) *load.Field {
+	t.Helper()
+
+	for _, schemaField := range schema.Fields {
+		if schemaField.Name == name {
+			return schemaField
+		}
+	}
+
+	require.Failf(t, "missing schema field", "schema %s should include field %s", schema.Name, name)
+	return nil
+}
+
+func requireStringFieldValidator(t *testing.T, fields []ent.Field, name string) func(string) error {
+	t.Helper()
+
+	for _, entField := range fields {
+		descriptor := entField.Descriptor()
+		if descriptor.Name != name {
+			continue
+		}
+		require.NotEmpty(t, descriptor.Validators, "field %s should include a validator", name)
+		validator, ok := descriptor.Validators[0].(func(string) error)
+		require.True(t, ok, "field %s validator should be func(string) error", name)
+		return validator
+	}
+
+	require.Failf(t, "missing field validator", "schema should include field %s", name)
+	return nil
+}
+
 func requireHasUniqueIndex(t *testing.T, schema *load.Schema, fields ...string) {
 	t.Helper()
 

backend/ent/schema/payment_order.go

@@ -185,7 +185,9 @@ func (PaymentOrder) Edges() []ent.Edge {
 
 func (PaymentOrder) Indexes() []ent.Index {
 	return []ent.Index{
-		index.Fields("out_trade_no"),
+		index.Fields("out_trade_no").
+			Unique().
+			Annotations(entsql.IndexWhere("out_trade_no <> ''")),
 		index.Fields("user_id"),
 		index.Fields("status"),
 		index.Fields("expires_at"),

backend/ent/schema/pending_auth_session.go

@@ -119,6 +119,7 @@ func (PendingAuthSession) Edges() []ent.Edge {
 			Field("target_user_id").
 			Unique(),
 		edge.To("adoption_decision", IdentityAdoptionDecision.Type).
+			Annotations(entsql.OnDelete(entsql.Cascade)).
 			Unique(),
 	}
 }

backend/ent/schema/user.go

 package schema
 
 import (
+	"fmt"
+
 	"github.com/Wei-Shaw/sub2api/ent/schema/mixins"
 	"github.com/Wei-Shaw/sub2api/internal/domain"
 
@@ -73,7 +75,14 @@ func (User) Fields() []ent.Field {
 			Optional().
 			Nillable(),
 		field.String("signup_source").
-			MaxLen(20).
+			Validate(func(value string) error {
+				switch value {
+				case "email", "linuxdo", "wechat", "oidc":
+					return nil
+				default:
+					return fmt.Errorf("must be one of email, linuxdo, wechat, oidc")
+				}
+			}).
 			Default("email"),
 		field.Time("last_login_at").
 			Optional().
@@ -115,7 +124,8 @@ func (User) Edges() []ent.Edge {
 		edge.To("attribute_values", UserAttributeValue.Type),
 		edge.To("promo_code_usages", PromoCodeUsage.Type),
 		edge.To("payment_orders", PaymentOrder.Type),
-		edge.To("auth_identities", AuthIdentity.Type),
+		edge.To("auth_identities", AuthIdentity.Type).
+			Annotations(entsql.OnDelete(entsql.Cascade)),
 		edge.To("pending_auth_sessions", PendingAuthSession.Type),
 	}
 }

backend/internal/config/config.go

@@ -70,6 +70,7 @@ type Config struct {
 	JWT                     JWTConfig                     `mapstructure:"jwt"`
 	Totp                    TotpConfig                    `mapstructure:"totp"`
 	LinuxDo                 LinuxDoConnectConfig          `mapstructure:"linuxdo_connect"`
+	WeChat                  WeChatConnectConfig           `mapstructure:"wechat_connect"`
 	OIDC                    OIDCConnectConfig             `mapstructure:"oidc_connect"`
 	Default                 DefaultConfig                 `mapstructure:"default"`
 	RateLimit               RateLimitConfig               `mapstructure:"rate_limit"`
@@ -190,6 +191,25 @@ type LinuxDoConnectConfig struct {
 	UserInfoUsernamePath string `mapstructure:"userinfo_username_path"`
 }
 
+type WeChatConnectConfig struct {
+	Enabled             bool   `mapstructure:"enabled"`
+	AppID               string `mapstructure:"app_id"`
+	AppSecret           string `mapstructure:"app_secret"`
+	OpenAppID           string `mapstructure:"open_app_id"`
+	OpenAppSecret       string `mapstructure:"open_app_secret"`
+	MPAppID             string `mapstructure:"mp_app_id"`
+	MPAppSecret         string `mapstructure:"mp_app_secret"`
+	MobileAppID         string `mapstructure:"mobile_app_id"`
+	MobileAppSecret     string `mapstructure:"mobile_app_secret"`
+	OpenEnabled         bool   `mapstructure:"open_enabled"`
+	MPEnabled           bool   `mapstructure:"mp_enabled"`
+	MobileEnabled       bool   `mapstructure:"mobile_enabled"`
+	Mode                string `mapstructure:"mode"`
+	Scopes              string `mapstructure:"scopes"`
+	RedirectURL         string `mapstructure:"redirect_url"`
+	FrontendRedirectURL string `mapstructure:"frontend_redirect_url"`
+}
+
 type OIDCConnectConfig struct {
 	Enabled                 bool   `mapstructure:"enabled"`
 	ProviderName            string `mapstructure:"provider_name"` // 显示名: "Keycloak" 等
@@ -207,6 +227,8 @@ type OIDCConnectConfig struct {
 	TokenAuthMethod         string `mapstructure:"token_auth_method"`     // client_secret_post / client_secret_basic / none
 	UsePKCE                 bool   `mapstructure:"use_pkce"`
 	ValidateIDToken         bool   `mapstructure:"validate_id_token"`
+	UsePKCEExplicit         bool   `mapstructure:"-" yaml:"-"`
+	ValidateIDTokenExplicit bool   `mapstructure:"-" yaml:"-"`
 	AllowedSigningAlgs      string `mapstructure:"allowed_signing_algs"`   // 默认 "RS256,ES256,PS256"
 	ClockSkewSeconds        int    `mapstructure:"clock_skew_seconds"`     // 默认 120
 	RequireEmailVerified    bool   `mapstructure:"require_email_verified"` // 默认 false
@@ -218,6 +240,225 @@ type OIDCConnectConfig struct {
 	UserInfoUsernamePath string `mapstructure:"userinfo_username_path"`
 }
 
+const (
+	defaultWeChatConnectMode             = "open"
+	defaultWeChatConnectScopes           = "snsapi_login"
+	defaultWeChatConnectFrontendRedirect = "/auth/wechat/callback"
+)
+
+func firstNonEmptyString(values ...string) string {
+	for _, value := range values {
+		if trimmed := strings.TrimSpace(value); trimmed != "" {
+			return trimmed
+		}
+	}
+	return ""
+}
+
+func normalizeWeChatConnectMode(raw string) string {
+	switch strings.ToLower(strings.TrimSpace(raw)) {
+	case "mp":
+		return "mp"
+	case "mobile":
+		return "mobile"
+	default:
+		return defaultWeChatConnectMode
+	}
+}
+
+func normalizeWeChatConnectStoredMode(openEnabled, mpEnabled, mobileEnabled bool, mode string) string {
+	mode = normalizeWeChatConnectMode(mode)
+	switch mode {
+	case "open":
+		if openEnabled {
+			return "open"
+		}
+	case "mp":
+		if mpEnabled {
+			return "mp"
+		}
+	case "mobile":
+		if mobileEnabled {
+			return "mobile"
+		}
+	}
+	switch {
+	case openEnabled:
+		return "open"
+	case mpEnabled:
+		return "mp"
+	case mobileEnabled:
+		return "mobile"
+	default:
+		return mode
+	}
+}
+
+func defaultWeChatConnectScopesForMode(mode string) string {
+	switch normalizeWeChatConnectMode(mode) {
+	case "mp":
+		return "snsapi_userinfo"
+	case "mobile":
+		return ""
+	default:
+		return defaultWeChatConnectScopes
+	}
+}
+
+func normalizeWeChatConnectScopes(raw, mode string) string {
+	switch normalizeWeChatConnectMode(mode) {
+	case "mp":
+		switch strings.TrimSpace(raw) {
+		case "snsapi_base":
+			return "snsapi_base"
+		case "snsapi_userinfo":
+			return "snsapi_userinfo"
+		default:
+			return defaultWeChatConnectScopesForMode(mode)
+		}
+	case "mobile":
+		return ""
+	default:
+		return defaultWeChatConnectScopes
+	}
+}
+
+func shouldApplyLegacyWeChatEnv(configKey, envKey string) bool {
+	if viper.InConfig(configKey) {
+		return false
+	}
+	_, hasNewEnv := os.LookupEnv(envKey)
+	return !hasNewEnv
+}
+
+func hasExplicitConfigOrEnv(configKey, envKey string) bool {
+	if viper.InConfig(configKey) {
+		return true
+	}
+	_, ok := os.LookupEnv(envKey)
+	return ok
+}
+
+func applyLegacyWeChatConnectEnvCompatibility(cfg *WeChatConnectConfig) {
+	if cfg == nil {
+		return
+	}
+
+	legacyOpenAppID := ""
+	if shouldApplyLegacyWeChatEnv("wechat_connect.open_app_id", "WECHAT_CONNECT_OPEN_APP_ID") &&
+		shouldApplyLegacyWeChatEnv("wechat_connect.app_id", "WECHAT_CONNECT_APP_ID") {
+		legacyOpenAppID = strings.TrimSpace(os.Getenv("WECHAT_OAUTH_OPEN_APP_ID"))
+		if legacyOpenAppID != "" {
+			cfg.OpenAppID = legacyOpenAppID
+		}
+	}
+
+	legacyOpenAppSecret := ""
+	if shouldApplyLegacyWeChatEnv("wechat_connect.open_app_secret", "WECHAT_CONNECT_OPEN_APP_SECRET") &&
+		shouldApplyLegacyWeChatEnv("wechat_connect.app_secret", "WECHAT_CONNECT_APP_SECRET") {
+		legacyOpenAppSecret = strings.TrimSpace(os.Getenv("WECHAT_OAUTH_OPEN_APP_SECRET"))
+		if legacyOpenAppSecret != "" {
+			cfg.OpenAppSecret = legacyOpenAppSecret
+		}
+	}
+
+	legacyMPAppID := ""
+	if shouldApplyLegacyWeChatEnv("wechat_connect.mp_app_id", "WECHAT_CONNECT_MP_APP_ID") &&
+		shouldApplyLegacyWeChatEnv("wechat_connect.app_id", "WECHAT_CONNECT_APP_ID") {
+		legacyMPAppID = strings.TrimSpace(os.Getenv("WECHAT_OAUTH_MP_APP_ID"))
+		if legacyMPAppID != "" {
+			cfg.MPAppID = legacyMPAppID
+		}
+	}
+
+	legacyMPAppSecret := ""
+	if shouldApplyLegacyWeChatEnv("wechat_connect.mp_app_secret", "WECHAT_CONNECT_MP_APP_SECRET") &&
+		shouldApplyLegacyWeChatEnv("wechat_connect.app_secret", "WECHAT_CONNECT_APP_SECRET") {
+		legacyMPAppSecret = strings.TrimSpace(os.Getenv("WECHAT_OAUTH_MP_APP_SECRET"))
+		if legacyMPAppSecret != "" {
+			cfg.MPAppSecret = legacyMPAppSecret
+		}
+	}
+
+	if shouldApplyLegacyWeChatEnv("wechat_connect.frontend_redirect_url", "WECHAT_CONNECT_FRONTEND_REDIRECT_URL") {
+		if legacyFrontend := strings.TrimSpace(os.Getenv("WECHAT_OAUTH_FRONTEND_REDIRECT_URL")); legacyFrontend != "" {
+			cfg.FrontendRedirectURL = legacyFrontend
+		}
+	}
+
+	hasLegacyOpen := legacyOpenAppID != "" && legacyOpenAppSecret != ""
+	hasLegacyMP := legacyMPAppID != "" && legacyMPAppSecret != ""
+
+	if shouldApplyLegacyWeChatEnv("wechat_connect.enabled", "WECHAT_CONNECT_ENABLED") && (hasLegacyOpen || hasLegacyMP) {
+		cfg.Enabled = true
+	}
+	if shouldApplyLegacyWeChatEnv("wechat_connect.open_enabled", "WECHAT_CONNECT_OPEN_ENABLED") && hasLegacyOpen {
+		cfg.OpenEnabled = true
+	}
+	if shouldApplyLegacyWeChatEnv("wechat_connect.mp_enabled", "WECHAT_CONNECT_MP_ENABLED") && hasLegacyMP {
+		cfg.MPEnabled = true
+	}
+	if shouldApplyLegacyWeChatEnv("wechat_connect.mode", "WECHAT_CONNECT_MODE") {
+		switch {
+		case hasLegacyMP && !hasLegacyOpen:
+			cfg.Mode = "mp"
+		case hasLegacyOpen:
+			cfg.Mode = "open"
+		}
+	}
+	if shouldApplyLegacyWeChatEnv("wechat_connect.scopes", "WECHAT_CONNECT_SCOPES") {
+		switch {
+		case hasLegacyMP && !hasLegacyOpen:
+			cfg.Scopes = defaultWeChatConnectScopesForMode("mp")
+		case hasLegacyOpen:
+			cfg.Scopes = defaultWeChatConnectScopesForMode("open")
+		}
+	}
+}
+
+func normalizeWeChatConnectConfig(cfg *WeChatConnectConfig) {
+	if cfg == nil {
+		return
+	}
+
+	cfg.AppID = strings.TrimSpace(cfg.AppID)
+	cfg.AppSecret = strings.TrimSpace(cfg.AppSecret)
+	cfg.OpenAppID = strings.TrimSpace(cfg.OpenAppID)
+	cfg.OpenAppSecret = strings.TrimSpace(cfg.OpenAppSecret)
+	cfg.MPAppID = strings.TrimSpace(cfg.MPAppID)
+	cfg.MPAppSecret = strings.TrimSpace(cfg.MPAppSecret)
+	cfg.MobileAppID = strings.TrimSpace(cfg.MobileAppID)
+	cfg.MobileAppSecret = strings.TrimSpace(cfg.MobileAppSecret)
+	cfg.Mode = normalizeWeChatConnectMode(cfg.Mode)
+	cfg.RedirectURL = strings.TrimSpace(cfg.RedirectURL)
+	cfg.FrontendRedirectURL = strings.TrimSpace(cfg.FrontendRedirectURL)
+
+	cfg.AppID = firstNonEmptyString(cfg.AppID, cfg.OpenAppID, cfg.MPAppID, cfg.MobileAppID)
+	cfg.AppSecret = firstNonEmptyString(cfg.AppSecret, cfg.OpenAppSecret, cfg.MPAppSecret, cfg.MobileAppSecret)
+	cfg.OpenAppID = firstNonEmptyString(cfg.OpenAppID, cfg.AppID)
+	cfg.OpenAppSecret = firstNonEmptyString(cfg.OpenAppSecret, cfg.AppSecret)
+	cfg.MPAppID = firstNonEmptyString(cfg.MPAppID, cfg.AppID)
+	cfg.MPAppSecret = firstNonEmptyString(cfg.MPAppSecret, cfg.AppSecret)
+	cfg.MobileAppID = firstNonEmptyString(cfg.MobileAppID, cfg.AppID)
+	cfg.MobileAppSecret = firstNonEmptyString(cfg.MobileAppSecret, cfg.AppSecret)
+
+	if !cfg.OpenEnabled && !cfg.MPEnabled && !cfg.MobileEnabled && cfg.Enabled {
+		switch cfg.Mode {
+		case "mp":
+			cfg.MPEnabled = true
+		case "mobile":
+			cfg.MobileEnabled = true
+		default:
+			cfg.OpenEnabled = true
+		}
+	}
+	cfg.Mode = normalizeWeChatConnectStoredMode(cfg.OpenEnabled, cfg.MPEnabled, cfg.MobileEnabled, cfg.Mode)
+	cfg.Scopes = normalizeWeChatConnectScopes(cfg.Scopes, cfg.Mode)
+	if cfg.FrontendRedirectURL == "" {
+		cfg.FrontendRedirectURL = defaultWeChatConnectFrontendRedirect
+	}
+}
+
 // TokenRefreshConfig OAuth token自动刷新配置
 type TokenRefreshConfig struct {
 	// 是否启用自动刷新
@@ -1012,6 +1253,8 @@ func load(allowMissingJWTSecret bool) (*Config, error) {
 	cfg.LinuxDo.UserInfoEmailPath = strings.TrimSpace(cfg.LinuxDo.UserInfoEmailPath)
 	cfg.LinuxDo.UserInfoIDPath = strings.TrimSpace(cfg.LinuxDo.UserInfoIDPath)
 	cfg.LinuxDo.UserInfoUsernamePath = strings.TrimSpace(cfg.LinuxDo.UserInfoUsernamePath)
+	applyLegacyWeChatConnectEnvCompatibility(&cfg.WeChat)
+	normalizeWeChatConnectConfig(&cfg.WeChat)
 	cfg.OIDC.ProviderName = strings.TrimSpace(cfg.OIDC.ProviderName)
 	cfg.OIDC.ClientID = strings.TrimSpace(cfg.OIDC.ClientID)
 	cfg.OIDC.ClientSecret = strings.TrimSpace(cfg.OIDC.ClientSecret)
@@ -1029,6 +1272,8 @@ func load(allowMissingJWTSecret bool) (*Config, error) {
 	cfg.OIDC.UserInfoEmailPath = strings.TrimSpace(cfg.OIDC.UserInfoEmailPath)
 	cfg.OIDC.UserInfoIDPath = strings.TrimSpace(cfg.OIDC.UserInfoIDPath)
 	cfg.OIDC.UserInfoUsernamePath = strings.TrimSpace(cfg.OIDC.UserInfoUsernamePath)
+	cfg.OIDC.UsePKCEExplicit = hasExplicitConfigOrEnv("oidc_connect.use_pkce", "OIDC_CONNECT_USE_PKCE")
+	cfg.OIDC.ValidateIDTokenExplicit = hasExplicitConfigOrEnv("oidc_connect.validate_id_token", "OIDC_CONNECT_VALIDATE_ID_TOKEN")
 	cfg.Dashboard.KeyPrefix = strings.TrimSpace(cfg.Dashboard.KeyPrefix)
 	cfg.CORS.AllowedOrigins = normalizeStringSlice(cfg.CORS.AllowedOrigins)
 	cfg.Security.ResponseHeaders.AdditionalAllowed = normalizeStringSlice(cfg.Security.ResponseHeaders.AdditionalAllowed)
@@ -1207,6 +1452,24 @@ func setDefaults() {
 	viper.SetDefault("linuxdo_connect.userinfo_id_path", "")
 	viper.SetDefault("linuxdo_connect.userinfo_username_path", "")
 
+	// WeChat Connect OAuth 登录
+	viper.SetDefault("wechat_connect.enabled", false)
+	viper.SetDefault("wechat_connect.app_id", "")
+	viper.SetDefault("wechat_connect.app_secret", "")
+	viper.SetDefault("wechat_connect.open_app_id", "")
+	viper.SetDefault("wechat_connect.open_app_secret", "")
+	viper.SetDefault("wechat_connect.mp_app_id", "")
+	viper.SetDefault("wechat_connect.mp_app_secret", "")
+	viper.SetDefault("wechat_connect.mobile_app_id", "")
+	viper.SetDefault("wechat_connect.mobile_app_secret", "")
+	viper.SetDefault("wechat_connect.open_enabled", false)
+	viper.SetDefault("wechat_connect.mp_enabled", false)
+	viper.SetDefault("wechat_connect.mobile_enabled", false)
+	viper.SetDefault("wechat_connect.mode", defaultWeChatConnectMode)
+	viper.SetDefault("wechat_connect.scopes", defaultWeChatConnectScopes)
+	viper.SetDefault("wechat_connect.redirect_url", "")
+	viper.SetDefault("wechat_connect.frontend_redirect_url", defaultWeChatConnectFrontendRedirect)
+
 	// Generic OIDC OAuth 登录
 	viper.SetDefault("oidc_connect.enabled", false)
 	viper.SetDefault("oidc_connect.provider_name", "OIDC")
@@ -1222,7 +1485,7 @@ func setDefaults() {
 	viper.SetDefault("oidc_connect.redirect_url", "")
 	viper.SetDefault("oidc_connect.frontend_redirect_url", "/auth/oidc/callback")
 	viper.SetDefault("oidc_connect.token_auth_method", "client_secret_post")
-	viper.SetDefault("oidc_connect.use_pkce", false)
+	viper.SetDefault("oidc_connect.use_pkce", true)
 	viper.SetDefault("oidc_connect.validate_id_token", true)
 	viper.SetDefault("oidc_connect.allowed_signing_algs", "RS256,ES256,PS256")
 	viper.SetDefault("oidc_connect.clock_skew_seconds", 120)
@@ -1613,9 +1876,6 @@ func (c *Config) Validate() error {
 		return fmt.Errorf("security.csp.policy is required when CSP is enabled")
 	}
 	if c.LinuxDo.Enabled {
-		if !c.LinuxDo.UsePKCE {
-			return fmt.Errorf("linuxdo_connect.use_pkce must be true when linuxdo_connect.enabled=true")
-		}
 		if strings.TrimSpace(c.LinuxDo.ClientID) == "" {
 			return fmt.Errorf("linuxdo_connect.client_id is required when linuxdo_connect.enabled=true")
 		}
@@ -1667,13 +1927,46 @@ func (c *Config) Validate() error {
 		warnIfInsecureURL("linuxdo_connect.redirect_url", c.LinuxDo.RedirectURL)
 		warnIfInsecureURL("linuxdo_connect.frontend_redirect_url", c.LinuxDo.FrontendRedirectURL)
 	}
-	if c.OIDC.Enabled {
-		if !c.OIDC.UsePKCE {
-			return fmt.Errorf("oidc_connect.use_pkce must be true when oidc_connect.enabled=true")
+	if c.WeChat.Enabled {
+		weChat := c.WeChat
+		normalizeWeChatConnectConfig(&weChat)
+
+		if weChat.OpenEnabled {
+			if strings.TrimSpace(weChat.OpenAppID) == "" {
+				return fmt.Errorf("wechat_connect.open_app_id is required when wechat_connect.open_enabled=true")
+			}
+			if strings.TrimSpace(weChat.OpenAppSecret) == "" {
+				return fmt.Errorf("wechat_connect.open_app_secret is required when wechat_connect.open_enabled=true")
 			}
-		if !c.OIDC.ValidateIDToken {
-			return fmt.Errorf("oidc_connect.validate_id_token must be true when oidc_connect.enabled=true")
 		}
+		if weChat.MPEnabled {
+			if strings.TrimSpace(weChat.MPAppID) == "" {
+				return fmt.Errorf("wechat_connect.mp_app_id is required when wechat_connect.mp_enabled=true")
+			}
+			if strings.TrimSpace(weChat.MPAppSecret) == "" {
+				return fmt.Errorf("wechat_connect.mp_app_secret is required when wechat_connect.mp_enabled=true")
+			}
+		}
+		if weChat.MobileEnabled {
+			if strings.TrimSpace(weChat.MobileAppID) == "" {
+				return fmt.Errorf("wechat_connect.mobile_app_id is required when wechat_connect.mobile_enabled=true")
+			}
+			if strings.TrimSpace(weChat.MobileAppSecret) == "" {
+				return fmt.Errorf("wechat_connect.mobile_app_secret is required when wechat_connect.mobile_enabled=true")
+			}
+		}
+		if v := strings.TrimSpace(weChat.RedirectURL); v != "" {
+			if err := ValidateAbsoluteHTTPURL(v); err != nil {
+				return fmt.Errorf("wechat_connect.redirect_url invalid: %w", err)
+			}
+			warnIfInsecureURL("wechat_connect.redirect_url", v)
+		}
+		if err := ValidateFrontendRedirectURL(weChat.FrontendRedirectURL); err != nil {
+			return fmt.Errorf("wechat_connect.frontend_redirect_url invalid: %w", err)
+		}
+		warnIfInsecureURL("wechat_connect.frontend_redirect_url", weChat.FrontendRedirectURL)
+	}
+	if c.OIDC.Enabled {
 		if strings.TrimSpace(c.OIDC.ClientID) == "" {
 			return fmt.Errorf("oidc_connect.client_id is required when oidc_connect.enabled=true")
 		}

backend/internal/config/config_test.go

@@ -225,6 +225,52 @@ func TestLoadSchedulingConfigFromEnv(t *testing.T) {
 	}
 }
 
+func TestLoadWeChatConnectConfigFromLegacyEnv(t *testing.T) {
+	resetViperWithJWTSecret(t)
+	t.Setenv("WECHAT_OAUTH_OPEN_APP_ID", "wx-open-app")
+	t.Setenv("WECHAT_OAUTH_OPEN_APP_SECRET", "wx-open-secret")
+	t.Setenv("WECHAT_OAUTH_MP_APP_ID", "wx-mp-app")
+	t.Setenv("WECHAT_OAUTH_MP_APP_SECRET", "wx-mp-secret")
+	t.Setenv("WECHAT_OAUTH_FRONTEND_REDIRECT_URL", "/auth/wechat/legacy-callback")
+
+	cfg, err := Load()
+	require.NoError(t, err)
+	require.True(t, cfg.WeChat.Enabled)
+	require.True(t, cfg.WeChat.OpenEnabled)
+	require.True(t, cfg.WeChat.MPEnabled)
+	require.False(t, cfg.WeChat.MobileEnabled)
+	require.Equal(t, "open", cfg.WeChat.Mode)
+	require.Equal(t, "wx-open-app", cfg.WeChat.OpenAppID)
+	require.Equal(t, "wx-open-secret", cfg.WeChat.OpenAppSecret)
+	require.Equal(t, "wx-mp-app", cfg.WeChat.MPAppID)
+	require.Equal(t, "wx-mp-secret", cfg.WeChat.MPAppSecret)
+	require.Equal(t, "/auth/wechat/legacy-callback", cfg.WeChat.FrontendRedirectURL)
+}
+
+func TestLoadDefaultOIDCSecurityDefaults(t *testing.T) {
+	resetViperWithJWTSecret(t)
+
+	cfg, err := Load()
+	require.NoError(t, err)
+	require.True(t, cfg.OIDC.UsePKCE)
+	require.True(t, cfg.OIDC.ValidateIDToken)
+	require.False(t, cfg.OIDC.UsePKCEExplicit)
+	require.False(t, cfg.OIDC.ValidateIDTokenExplicit)
+}
+
+func TestLoadExplicitOIDCSecurityDefaultsFromEnvMarksFlagsExplicit(t *testing.T) {
+	resetViperWithJWTSecret(t)
+	t.Setenv("OIDC_CONNECT_USE_PKCE", "false")
+	t.Setenv("OIDC_CONNECT_VALIDATE_ID_TOKEN", "false")
+
+	cfg, err := Load()
+	require.NoError(t, err)
+	require.False(t, cfg.OIDC.UsePKCE)
+	require.False(t, cfg.OIDC.ValidateIDToken)
+	require.True(t, cfg.OIDC.UsePKCEExplicit)
+	require.True(t, cfg.OIDC.ValidateIDTokenExplicit)
+}
+
 func TestLoadForcedCodexInstructionsTemplate(t *testing.T) {
 	resetViperWithJWTSecret(t)
 
@@ -346,7 +392,7 @@ func TestValidateLinuxDoFrontendRedirectURL(t *testing.T) {
 	}
 }
 
-func TestValidateLinuxDoPKCERequiredForPublicClient(t *testing.T) {
+func TestValidateLinuxDoAllowsDisablingPKCEForCompatibility(t *testing.T) {
 	resetViperWithJWTSecret(t)
 
 	cfg, err := Load()
@@ -363,11 +409,8 @@ func TestValidateLinuxDoPKCERequiredForPublicClient(t *testing.T) {
 	cfg.LinuxDo.UsePKCE = false
 
 	err = cfg.Validate()
-	if err == nil {
-		t.Fatalf("Validate() expected error when token_auth_method=none and use_pkce=false, got nil")
-	}
-	if !strings.Contains(err.Error(), "linuxdo_connect.use_pkce") {
-		t.Fatalf("Validate() expected use_pkce error, got: %v", err)
+	if err != nil {
+		t.Fatalf("Validate() expected LinuxDo config without PKCE to pass for compatibility, got: %v", err)
 	}
 }
 
@@ -427,6 +470,35 @@ func TestValidateOIDCAllowsIssuerOnlyEndpointsWithDiscoveryFallback(t *testing.T
 	}
 }
 
+func TestValidateOIDCAllowsExplicitCompatibilityOverridesForPKCEAndIDTokenValidation(t *testing.T) {
+	resetViperWithJWTSecret(t)
+
+	cfg, err := Load()
+	if err != nil {
+		t.Fatalf("Load() error: %v", err)
+	}
+
+	cfg.OIDC.Enabled = true
+	cfg.OIDC.ClientID = "oidc-client"
+	cfg.OIDC.ClientSecret = "oidc-secret"
+	cfg.OIDC.IssuerURL = "https://issuer.example.com"
+	cfg.OIDC.AuthorizeURL = "https://issuer.example.com/auth"
+	cfg.OIDC.TokenURL = "https://issuer.example.com/token"
+	cfg.OIDC.UserInfoURL = "https://issuer.example.com/userinfo"
+	cfg.OIDC.RedirectURL = "https://example.com/api/v1/auth/oauth/oidc/callback"
+	cfg.OIDC.FrontendRedirectURL = "/auth/oidc/callback"
+	cfg.OIDC.Scopes = "openid email profile"
+	cfg.OIDC.UsePKCE = false
+	cfg.OIDC.ValidateIDToken = false
+	cfg.OIDC.JWKSURL = ""
+	cfg.OIDC.AllowedSigningAlgs = ""
+
+	err = cfg.Validate()
+	if err != nil {
+		t.Fatalf("Validate() expected OIDC config without PKCE/id_token validation to pass for compatibility, got: %v", err)
+	}
+}
+
 func TestLoadDefaultDashboardCacheConfig(t *testing.T) {
 	resetViperWithJWTSecret(t)
 

backend/internal/handler/admin/setting_handler.go

@@ -304,8 +304,8 @@ type UpdateSettingsRequest struct {
 	OIDCConnectRedirectURL          string `json:"oidc_connect_redirect_url"`
 	OIDCConnectFrontendRedirectURL  string `json:"oidc_connect_frontend_redirect_url"`
 	OIDCConnectTokenAuthMethod      string `json:"oidc_connect_token_auth_method"`
-	OIDCConnectUsePKCE              bool   `json:"oidc_connect_use_pkce"`
-	OIDCConnectValidateIDToken      bool   `json:"oidc_connect_validate_id_token"`
+	OIDCConnectUsePKCE              *bool  `json:"oidc_connect_use_pkce"`
+	OIDCConnectValidateIDToken      *bool  `json:"oidc_connect_validate_id_token"`
 	OIDCConnectAllowedSigningAlgs   string `json:"oidc_connect_allowed_signing_algs"`
 	OIDCConnectClockSkewSeconds     int    `json:"oidc_connect_clock_skew_seconds"`
 	OIDCConnectRequireEmailVerified bool   `json:"oidc_connect_require_email_verified"`
@@ -565,6 +565,15 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		req.WeChatConnectScopes = strings.TrimSpace(req.WeChatConnectScopes)
 		req.WeChatConnectRedirectURL = strings.TrimSpace(req.WeChatConnectRedirectURL)
 		req.WeChatConnectFrontendRedirectURL = strings.TrimSpace(req.WeChatConnectFrontendRedirectURL)
+		req.WeChatConnectAppID = strings.TrimSpace(firstNonEmpty(req.WeChatConnectAppID, previousSettings.WeChatConnectAppID))
+		req.WeChatConnectRedirectURL = strings.TrimSpace(firstNonEmpty(req.WeChatConnectRedirectURL, previousSettings.WeChatConnectRedirectURL))
+		req.WeChatConnectFrontendRedirectURL = strings.TrimSpace(firstNonEmpty(req.WeChatConnectFrontendRedirectURL, previousSettings.WeChatConnectFrontendRedirectURL))
+		if req.WeChatConnectMode == "" {
+			req.WeChatConnectMode = strings.ToLower(strings.TrimSpace(previousSettings.WeChatConnectMode))
+		}
+		if req.WeChatConnectScopes == "" {
+			req.WeChatConnectScopes = strings.TrimSpace(previousSettings.WeChatConnectScopes)
+		}
 
 		if req.WeChatConnectMPEnabled && req.WeChatConnectMobileEnabled {
 			response.BadRequest(c, "WeChat Official Account and Mobile App cannot be enabled at the same time")
@@ -598,9 +607,9 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 			}
 		}
 
-		req.WeChatConnectOpenAppID = strings.TrimSpace(firstNonEmpty(req.WeChatConnectOpenAppID, req.WeChatConnectAppID))
-		req.WeChatConnectMPAppID = strings.TrimSpace(firstNonEmpty(req.WeChatConnectMPAppID, req.WeChatConnectAppID))
-		req.WeChatConnectMobileAppID = strings.TrimSpace(firstNonEmpty(req.WeChatConnectMobileAppID, req.WeChatConnectAppID))
+		req.WeChatConnectOpenAppID = strings.TrimSpace(firstNonEmpty(req.WeChatConnectOpenAppID, req.WeChatConnectAppID, previousSettings.WeChatConnectOpenAppID, previousSettings.WeChatConnectAppID))
+		req.WeChatConnectMPAppID = strings.TrimSpace(firstNonEmpty(req.WeChatConnectMPAppID, req.WeChatConnectAppID, previousSettings.WeChatConnectMPAppID, previousSettings.WeChatConnectAppID))
+		req.WeChatConnectMobileAppID = strings.TrimSpace(firstNonEmpty(req.WeChatConnectMobileAppID, req.WeChatConnectAppID, previousSettings.WeChatConnectMobileAppID, previousSettings.WeChatConnectAppID))
 
 		if req.WeChatConnectOpenAppSecret == "" {
 			req.WeChatConnectOpenAppSecret = strings.TrimSpace(firstNonEmpty(previousSettings.WeChatConnectOpenAppSecret, previousSettings.WeChatConnectAppSecret, req.WeChatConnectAppSecret))
@@ -653,8 +662,9 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 				req.WeChatConnectScopes = service.DefaultWeChatConnectScopesForMode(req.WeChatConnectMode)
 			}
 		}
+		if req.WeChatConnectOpenEnabled || req.WeChatConnectMPEnabled {
 			if req.WeChatConnectRedirectURL == "" {
-			response.BadRequest(c, "WeChat Redirect URL is required when enabled")
+				response.BadRequest(c, "WeChat Redirect URL is required when web oauth is enabled")
 				return
 			}
 			if err := config.ValidateAbsoluteHTTPURL(req.WeChatConnectRedirectURL); err != nil {
@@ -669,8 +679,14 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 				return
 			}
 		}
+	}
 
 	// Generic OIDC 参数验证
+	oidcUsePKCE, oidcValidateIDToken, err := h.settingService.OIDCSecurityWriteDefaults(c.Request.Context())
+	if err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
 	if req.OIDCConnectEnabled {
 		req.OIDCConnectProviderName = strings.TrimSpace(req.OIDCConnectProviderName)
 		req.OIDCConnectClientID = strings.TrimSpace(req.OIDCConnectClientID)
@@ -689,10 +705,35 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		req.OIDCConnectUserInfoEmailPath = strings.TrimSpace(req.OIDCConnectUserInfoEmailPath)
 		req.OIDCConnectUserInfoIDPath = strings.TrimSpace(req.OIDCConnectUserInfoIDPath)
 		req.OIDCConnectUserInfoUsernamePath = strings.TrimSpace(req.OIDCConnectUserInfoUsernamePath)
-
-		if req.OIDCConnectProviderName == "" {
-			req.OIDCConnectProviderName = "OIDC"
+		req.OIDCConnectProviderName = strings.TrimSpace(firstNonEmpty(req.OIDCConnectProviderName, previousSettings.OIDCConnectProviderName, "OIDC"))
+		req.OIDCConnectClientID = strings.TrimSpace(firstNonEmpty(req.OIDCConnectClientID, previousSettings.OIDCConnectClientID))
+		req.OIDCConnectIssuerURL = strings.TrimSpace(firstNonEmpty(req.OIDCConnectIssuerURL, previousSettings.OIDCConnectIssuerURL))
+		req.OIDCConnectDiscoveryURL = strings.TrimSpace(firstNonEmpty(req.OIDCConnectDiscoveryURL, previousSettings.OIDCConnectDiscoveryURL))
+		req.OIDCConnectAuthorizeURL = strings.TrimSpace(firstNonEmpty(req.OIDCConnectAuthorizeURL, previousSettings.OIDCConnectAuthorizeURL))
+		req.OIDCConnectTokenURL = strings.TrimSpace(firstNonEmpty(req.OIDCConnectTokenURL, previousSettings.OIDCConnectTokenURL))
+		req.OIDCConnectUserInfoURL = strings.TrimSpace(firstNonEmpty(req.OIDCConnectUserInfoURL, previousSettings.OIDCConnectUserInfoURL))
+		req.OIDCConnectJWKSURL = strings.TrimSpace(firstNonEmpty(req.OIDCConnectJWKSURL, previousSettings.OIDCConnectJWKSURL))
+		req.OIDCConnectScopes = strings.TrimSpace(firstNonEmpty(req.OIDCConnectScopes, previousSettings.OIDCConnectScopes, "openid email profile"))
+		req.OIDCConnectRedirectURL = strings.TrimSpace(firstNonEmpty(req.OIDCConnectRedirectURL, previousSettings.OIDCConnectRedirectURL))
+		req.OIDCConnectFrontendRedirectURL = strings.TrimSpace(firstNonEmpty(req.OIDCConnectFrontendRedirectURL, previousSettings.OIDCConnectFrontendRedirectURL, "/auth/oidc/callback"))
+		req.OIDCConnectTokenAuthMethod = strings.ToLower(strings.TrimSpace(firstNonEmpty(req.OIDCConnectTokenAuthMethod, previousSettings.OIDCConnectTokenAuthMethod, "client_secret_post")))
+		req.OIDCConnectAllowedSigningAlgs = strings.TrimSpace(firstNonEmpty(req.OIDCConnectAllowedSigningAlgs, previousSettings.OIDCConnectAllowedSigningAlgs, "RS256,ES256,PS256"))
+		req.OIDCConnectUserInfoEmailPath = strings.TrimSpace(firstNonEmpty(req.OIDCConnectUserInfoEmailPath, previousSettings.OIDCConnectUserInfoEmailPath))
+		req.OIDCConnectUserInfoIDPath = strings.TrimSpace(firstNonEmpty(req.OIDCConnectUserInfoIDPath, previousSettings.OIDCConnectUserInfoIDPath))
+		req.OIDCConnectUserInfoUsernamePath = strings.TrimSpace(firstNonEmpty(req.OIDCConnectUserInfoUsernamePath, previousSettings.OIDCConnectUserInfoUsernamePath))
+		if req.OIDCConnectUsePKCE != nil {
+			oidcUsePKCE = *req.OIDCConnectUsePKCE
+		}
+		if req.OIDCConnectValidateIDToken != nil {
+			oidcValidateIDToken = *req.OIDCConnectValidateIDToken
+		}
+		if req.OIDCConnectClockSkewSeconds == 0 {
+			req.OIDCConnectClockSkewSeconds = previousSettings.OIDCConnectClockSkewSeconds
+			if req.OIDCConnectClockSkewSeconds == 0 {
+				req.OIDCConnectClockSkewSeconds = 120
 			}
+		}
+
 		if req.OIDCConnectClientID == "" {
 			response.BadRequest(c, "OIDC Client ID is required when enabled")
 			return
@@ -749,14 +790,6 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 			response.BadRequest(c, "OIDC scopes must contain openid")
 			return
 		}
-		if !req.OIDCConnectUsePKCE {
-			response.BadRequest(c, "OIDC PKCE must be enabled")
-			return
-		}
-		if !req.OIDCConnectValidateIDToken {
-			response.BadRequest(c, "OIDC ID Token validation must be enabled")
-			return
-		}
 		switch req.OIDCConnectTokenAuthMethod {
 		case "", "client_secret_post", "client_secret_basic", "none":
 		default:
@@ -767,7 +800,7 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 			response.BadRequest(c, "OIDC clock skew seconds must be between 0 and 600")
 			return
 		}
-		if req.OIDCConnectAllowedSigningAlgs == "" {
+		if oidcValidateIDToken && req.OIDCConnectAllowedSigningAlgs == "" {
 			response.BadRequest(c, "OIDC Allowed Signing Algs is required when validate_id_token=true")
 			return
 		}
@@ -1048,8 +1081,8 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		OIDCConnectRedirectURL:           req.OIDCConnectRedirectURL,
 		OIDCConnectFrontendRedirectURL:   req.OIDCConnectFrontendRedirectURL,
 		OIDCConnectTokenAuthMethod:       req.OIDCConnectTokenAuthMethod,
-		OIDCConnectUsePKCE:               req.OIDCConnectUsePKCE,
-		OIDCConnectValidateIDToken:       req.OIDCConnectValidateIDToken,
+		OIDCConnectUsePKCE:               oidcUsePKCE,
+		OIDCConnectValidateIDToken:       oidcValidateIDToken,
 		OIDCConnectAllowedSigningAlgs:    req.OIDCConnectAllowedSigningAlgs,
 		OIDCConnectClockSkewSeconds:      req.OIDCConnectClockSkewSeconds,
 		OIDCConnectRequireEmailVerified:  req.OIDCConnectRequireEmailVerified,

backend/internal/handler/admin/setting_handler_auth_source_defaults_test.go

@@ -247,6 +247,163 @@ func TestSettingHandler_UpdateSettings_PersistsPaymentVisibleMethodsAndAdvancedS
 	require.Equal(t, true, data["openai_advanced_scheduler_enabled"])
 }
 
+func TestSettingHandler_UpdateSettings_PreservesLegacyBlankPaymentVisibleMethodSource(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	repo := &settingHandlerRepoStub{
+		values: map[string]string{
+			service.SettingKeyPromoCodeEnabled:               "true",
+			service.SettingPaymentVisibleMethodAlipayEnabled: "true",
+			service.SettingPaymentVisibleMethodAlipaySource:  "",
+			service.SettingPaymentVisibleMethodWxpayEnabled:  "false",
+			service.SettingPaymentVisibleMethodWxpaySource:   "",
+		},
+	}
+	svc := service.NewSettingService(repo, &config.Config{Default: config.DefaultConfig{UserConcurrency: 5}})
+	handler := NewSettingHandler(svc, nil, nil, nil, nil, nil)
+
+	body := map[string]any{
+		"promo_code_enabled": false,
+	}
+	rawBody, err := json.Marshal(body)
+	require.NoError(t, err)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPut, "/api/v1/admin/settings", bytes.NewReader(rawBody))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	handler.UpdateSettings(c)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Equal(t, "", repo.values[service.SettingPaymentVisibleMethodAlipaySource])
+	require.Equal(t, "true", repo.values[service.SettingPaymentVisibleMethodAlipayEnabled])
+}
+
+func TestSettingHandler_UpdateSettings_PersistsExplicitFalseOIDCCompatibilityFlags(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	repo := &settingHandlerRepoStub{
+		values: map[string]string{
+			service.SettingKeyPromoCodeEnabled:               "true",
+			service.SettingKeyOIDCConnectEnabled:             "true",
+			service.SettingKeyOIDCConnectProviderName:        "OIDC",
+			service.SettingKeyOIDCConnectClientID:            "oidc-client",
+			service.SettingKeyOIDCConnectClientSecret:        "oidc-secret",
+			service.SettingKeyOIDCConnectIssuerURL:           "https://issuer.example.com",
+			service.SettingKeyOIDCConnectAuthorizeURL:        "https://issuer.example.com/auth",
+			service.SettingKeyOIDCConnectTokenURL:            "https://issuer.example.com/token",
+			service.SettingKeyOIDCConnectUserInfoURL:         "https://issuer.example.com/userinfo",
+			service.SettingKeyOIDCConnectJWKSURL:             "https://issuer.example.com/jwks",
+			service.SettingKeyOIDCConnectScopes:              "openid email profile",
+			service.SettingKeyOIDCConnectRedirectURL:         "https://example.com/api/v1/auth/oauth/oidc/callback",
+			service.SettingKeyOIDCConnectFrontendRedirectURL: "/auth/oidc/callback",
+			service.SettingKeyOIDCConnectTokenAuthMethod:     "client_secret_post",
+			service.SettingKeyOIDCConnectUsePKCE:             "true",
+			service.SettingKeyOIDCConnectValidateIDToken:     "true",
+			service.SettingKeyOIDCConnectAllowedSigningAlgs:  "RS256",
+			service.SettingKeyOIDCConnectClockSkewSeconds:    "120",
+		},
+	}
+	svc := service.NewSettingService(repo, &config.Config{Default: config.DefaultConfig{UserConcurrency: 5}})
+	handler := NewSettingHandler(svc, nil, nil, nil, nil, nil)
+
+	body := map[string]any{
+		"promo_code_enabled":                true,
+		"oidc_connect_enabled":              true,
+		"oidc_connect_use_pkce":             false,
+		"oidc_connect_validate_id_token":    false,
+		"oidc_connect_allowed_signing_algs": "",
+	}
+	rawBody, err := json.Marshal(body)
+	require.NoError(t, err)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPut, "/api/v1/admin/settings", bytes.NewReader(rawBody))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	handler.UpdateSettings(c)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Equal(t, "false", repo.values[service.SettingKeyOIDCConnectUsePKCE])
+	require.Equal(t, "false", repo.values[service.SettingKeyOIDCConnectValidateIDToken])
+
+	var resp response.Response
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &resp))
+	data, ok := resp.Data.(map[string]any)
+	require.True(t, ok)
+	require.Equal(t, false, data["oidc_connect_use_pkce"])
+	require.Equal(t, false, data["oidc_connect_validate_id_token"])
+}
+
+func TestSettingHandler_UpdateSettings_DoesNotSolidifyImplicitOIDCSecurityDefaultsOnLegacyUpgrade(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	repo := &settingHandlerRepoStub{
+		values: map[string]string{
+			service.SettingKeyPromoCodeEnabled:                "true",
+			service.SettingKeyOIDCConnectEnabled:              "true",
+			service.SettingKeyOIDCConnectProviderName:         "OIDC",
+			service.SettingKeyOIDCConnectClientID:             "oidc-client",
+			service.SettingKeyOIDCConnectClientSecret:         "oidc-secret",
+			service.SettingKeyOIDCConnectIssuerURL:            "https://issuer.example.com",
+			service.SettingKeyOIDCConnectAuthorizeURL:         "https://issuer.example.com/auth",
+			service.SettingKeyOIDCConnectTokenURL:             "https://issuer.example.com/token",
+			service.SettingKeyOIDCConnectUserInfoURL:          "https://issuer.example.com/userinfo",
+			service.SettingKeyOIDCConnectJWKSURL:              "https://issuer.example.com/jwks",
+			service.SettingKeyOIDCConnectScopes:               "openid email profile",
+			service.SettingKeyOIDCConnectRedirectURL:          "https://example.com/api/v1/auth/oauth/oidc/callback",
+			service.SettingKeyOIDCConnectFrontendRedirectURL:  "/auth/oidc/callback",
+			service.SettingKeyOIDCConnectTokenAuthMethod:      "client_secret_post",
+			service.SettingKeyOIDCConnectAllowedSigningAlgs:   "RS256",
+			service.SettingKeyOIDCConnectClockSkewSeconds:     "120",
+			service.SettingKeyOIDCConnectRequireEmailVerified: "false",
+			service.SettingKeyOIDCConnectUserInfoEmailPath:    "",
+			service.SettingKeyOIDCConnectUserInfoIDPath:       "",
+			service.SettingKeyOIDCConnectUserInfoUsernamePath: "",
+		},
+	}
+	svc := service.NewSettingService(repo, &config.Config{
+		Default: config.DefaultConfig{UserConcurrency: 5},
+		OIDC: config.OIDCConnectConfig{
+			Enabled:             true,
+			ProviderName:        "OIDC",
+			ClientID:            "oidc-client",
+			ClientSecret:        "oidc-secret",
+			IssuerURL:           "https://issuer.example.com",
+			AuthorizeURL:        "https://issuer.example.com/auth",
+			TokenURL:            "https://issuer.example.com/token",
+			UserInfoURL:         "https://issuer.example.com/userinfo",
+			JWKSURL:             "https://issuer.example.com/jwks",
+			Scopes:              "openid email profile",
+			RedirectURL:         "https://example.com/api/v1/auth/oauth/oidc/callback",
+			FrontendRedirectURL: "/auth/oidc/callback",
+			TokenAuthMethod:     "client_secret_post",
+			UsePKCE:             true,
+			ValidateIDToken:     true,
+			AllowedSigningAlgs:  "RS256",
+			ClockSkewSeconds:    120,
+		},
+	})
+	handler := NewSettingHandler(svc, nil, nil, nil, nil, nil)
+
+	body := map[string]any{
+		"promo_code_enabled":   true,
+		"oidc_connect_enabled": true,
+	}
+	rawBody, err := json.Marshal(body)
+	require.NoError(t, err)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPut, "/api/v1/admin/settings", bytes.NewReader(rawBody))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	handler.UpdateSettings(c)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Equal(t, "false", repo.values[service.SettingKeyOIDCConnectUsePKCE])
+	require.Equal(t, "false", repo.values[service.SettingKeyOIDCConnectValidateIDToken])
+}
+
 func TestSettingHandler_UpdateSettings_RejectsInvalidPaymentVisibleMethodSource(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	repo := &settingHandlerRepoStub{

backend/internal/handler/auth_current_user_test.go

@@ -37,6 +37,7 @@ func TestAuthHandlerGetCurrentUserReturnsProfileCompatibilityFields(t *testing.T
 					VerifiedAt:      &verifiedAt,
 					Metadata: map[string]any{
 						"username":   "linuxdo-handle",
+						"avatar_url": "https://cdn.example.com/linuxdo.png",
 					},
 				},
 			},

backend/internal/handler/auth_handler.go

@@ -78,9 +78,24 @@ type AuthResponse struct {
 	User         *dto.User `json:"user"`
 }
 
+func ensureLoginUserActive(user *service.User) error {
+	if user == nil {
+		return infraerrors.Unauthorized("INVALID_USER", "user not found")
+	}
+	if !user.IsActive() {
+		return service.ErrUserNotActive
+	}
+	return nil
+}
+
 // respondWithTokenPair 生成 Token 对并返回认证响应
 // 如果 Token 对生成失败，回退到只返回 Access Token（向后兼容）
 func (h *AuthHandler) respondWithTokenPair(c *gin.Context, user *service.User) {
+	if err := ensureLoginUserActive(user); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+
 	tokenPair, err := h.authService.GenerateTokenPair(c.Request.Context(), user, "")
 	if err != nil {
 		slog.Error("failed to generate token pair", "error", err, "user_id", user.ID)
@@ -293,6 +308,10 @@ func (h *AuthHandler) Login2FA(c *gin.Context) {
 		response.ErrorFrom(c, err)
 		return
 	}
+	if err := ensureLoginUserActive(user); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
 
 	if err := h.ensureBackendModeAllowsUser(c.Request.Context(), user); err != nil {
 		response.ErrorFrom(c, err)
@@ -678,6 +697,8 @@ func (h *AuthHandler) Logout(c *gin.Context) {
 			// 不影响登出流程
 		}
 	}
+	h.consumePendingOAuthSessionOnLogout(c)
+	clearOAuthLogoutCookies(c)
 
 	response.Success(c, LogoutResponse{
 		Message: "Logged out successfully",
@@ -698,7 +719,7 @@ func (h *AuthHandler) RevokeAllSessions(c *gin.Context) {
 		return
 	}
 
-	if err := h.authService.RevokeAllUserSessions(c.Request.Context(), subject.UserID); err != nil {
+	if err := h.authService.RevokeAllUserTokens(c.Request.Context(), subject.UserID); err != nil {
 		slog.Error("failed to revoke all sessions", "user_id", subject.UserID, "error", err)
 		response.InternalError(c, "Failed to revoke sessions")
 		return

backend/internal/handler/auth_linuxdo_oauth.go

@@ -123,13 +123,16 @@ func (h *AuthHandler) LinuxDoOAuthStart(c *gin.Context) {
 		clearCookie(c, linuxDoOAuthBindUserCookieName, secureCookie)
 	}
 
+	codeChallenge := ""
+	if cfg.UsePKCE {
 		verifier, err := oauth.GenerateCodeVerifier()
 		if err != nil {
 			response.ErrorFrom(c, infraerrors.InternalServer("OAUTH_PKCE_GEN_FAILED", "failed to generate pkce verifier").WithCause(err))
 			return
 		}
-	codeChallenge := oauth.GenerateCodeChallenge(verifier)
+		codeChallenge = oauth.GenerateCodeChallenge(verifier)
 		setCookie(c, linuxDoOAuthVerifierCookie, encodeCookieValue(verifier), linuxDoOAuthCookieMaxAgeSec, secureCookie)
+	}
 
 	redirectURI := strings.TrimSpace(cfg.RedirectURL)
 	if redirectURI == "" {
@@ -200,11 +203,14 @@ func (h *AuthHandler) LinuxDoOAuthCallback(c *gin.Context) {
 	intent, _ := readCookieDecoded(c, linuxDoOAuthIntentCookieName)
 	intent = normalizeOAuthIntent(intent)
 
-	codeVerifier, _ := readCookieDecoded(c, linuxDoOAuthVerifierCookie)
+	codeVerifier := ""
+	if cfg.UsePKCE {
+		codeVerifier, _ = readCookieDecoded(c, linuxDoOAuthVerifierCookie)
 		if codeVerifier == "" {
 			redirectOAuthError(c, frontendCallback, "missing_verifier", "missing pkce verifier", "")
 			return
 		}
+	}
 
 	redirectURI := strings.TrimSpace(cfg.RedirectURL)
 	if redirectURI == "" {
@@ -292,24 +298,15 @@ func (h *AuthHandler) LinuxDoOAuthCallback(c *gin.Context) {
 		return
 	}
 	if existingIdentityUser != nil {
-		tokenPair, user, err := h.authService.LoginOrRegisterOAuthWithTokenPair(c.Request.Context(), existingIdentityUser.Email, username, "")
-		if err != nil {
-			redirectOAuthError(c, frontendCallback, "login_failed", infraerrors.Reason(err), infraerrors.Message(err))
-			return
-		}
 		if err := h.createOAuthPendingSession(c, oauthPendingSessionPayload{
 			Intent:                 oauthIntentLogin,
 			Identity:               identityKey,
-			TargetUserID:           &user.ID,
+			TargetUserID:           &existingIdentityUser.ID,
 			ResolvedEmail:          existingIdentityUser.Email,
 			RedirectTo:             redirectTo,
 			BrowserSessionKey:      browserSessionKey,
 			UpstreamIdentityClaims: upstreamClaims,
 			CompletionResponse: map[string]any{
-				"access_token":  tokenPair.AccessToken,
-				"refresh_token": tokenPair.RefreshToken,
-				"expires_in":    tokenPair.ExpiresIn,
-				"token_type":    "Bearer",
 				"redirect": redirectTo,
 			},
 		}); err != nil {
@@ -358,15 +355,20 @@ func (h *AuthHandler) findLinuxDoCompatEmailUser(ctx context.Context, email stri
 	}
 
 	userEntity, err := client.User.Query().
-		Where(dbuser.EmailEqualFold(email)).
-		Only(ctx)
+		Where(userNormalizedEmailPredicate(email)).
+		Order(dbent.Asc(dbuser.FieldID)).
+		All(ctx)
 	if err != nil {
-		if dbent.IsNotFound(err) {
-			return nil, nil
-		}
 		return nil, infraerrors.InternalServer("COMPAT_EMAIL_LOOKUP_FAILED", "failed to look up compat email user").WithCause(err)
 	}
-	return userEntity, nil
+	switch len(userEntity) {
+	case 0:
+		return nil, nil
+	case 1:
+		return userEntity[0], nil
+	default:
+		return nil, infraerrors.Conflict("USER_EMAIL_CONFLICT", "normalized email matched multiple users")
+	}
 }
 
 func (h *AuthHandler) createLinuxDoOAuthChoicePendingSession(
@@ -414,9 +416,15 @@ func (h *AuthHandler) createLinuxDoOAuthChoicePendingSession(
 		completionResponse["choice_reason"] = "force_email_on_signup"
 	}
 
+	var targetUserID *int64
+	if compatEmailUser != nil && compatEmailUser.ID > 0 {
+		targetUserID = &compatEmailUser.ID
+	}
+
 	return h.createOAuthPendingSession(c, oauthPendingSessionPayload{
 		Intent:                 oauthIntentLogin,
 		Identity:               identity,
+		TargetUserID:           targetUserID,
 		ResolvedEmail:          resolvedChoiceEmail,
 		RedirectTo:             redirectTo,
 		BrowserSessionKey:      browserSessionKey,
@@ -472,6 +480,15 @@ func (h *AuthHandler) CompleteLinuxDoOAuthRegistration(c *gin.Context) {
 		response.ErrorFrom(c, err)
 		return
 	}
+	if updatedSession, handled, err := h.legacyCompleteRegistrationSessionStatus(c, session); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	} else if handled {
+		c.JSON(http.StatusOK, buildPendingOAuthSessionStatusPayload(updatedSession))
+		return
+	} else {
+		session = updatedSession
+	}
 	if err := h.ensureBackendModeAllowsNewUserLogin(c.Request.Context()); err != nil {
 		response.ErrorFrom(c, err)
 		return
@@ -484,12 +501,16 @@ func (h *AuthHandler) CompleteLinuxDoOAuthRegistration(c *gin.Context) {
 		return
 	}
 
-	tokenPair, user, err := h.authService.LoginOrRegisterOAuthWithTokenPair(c.Request.Context(), email, username, req.InvitationCode)
-	if err != nil {
-		response.ErrorFrom(c, err)
+	client := h.entClient()
+	if client == nil {
+		response.ErrorFrom(c, infraerrors.ServiceUnavailable("PENDING_AUTH_NOT_READY", "pending auth service is not ready"))
 		return
 	}
-	decision, err := h.upsertPendingOAuthAdoptionDecision(c, session.ID, oauthAdoptionDecisionRequest{
+	if err := ensurePendingOAuthRegistrationIdentityAvailable(c.Request.Context(), client, session); err != nil {
+		respondPendingOAuthBindingApplyError(c, err)
+		return
+	}
+	decision, err := h.ensurePendingOAuthAdoptionDecision(c, session.ID, oauthAdoptionDecisionRequest{
 		AdoptDisplayName: req.AdoptDisplayName,
 		AdoptAvatar:      req.AdoptAvatar,
 	})
@@ -497,17 +518,16 @@ func (h *AuthHandler) CompleteLinuxDoOAuthRegistration(c *gin.Context) {
 		response.ErrorFrom(c, err)
 		return
 	}
-	if err := applyPendingOAuthAdoption(c.Request.Context(), h.entClient(), h.authService, h.userService, session, decision, &user.ID); err != nil {
-		response.ErrorFrom(c, infraerrors.InternalServer("PENDING_AUTH_ADOPTION_APPLY_FAILED", "failed to apply oauth profile adoption").WithCause(err))
+	tokenPair, user, err := h.authService.LoginOrRegisterOAuthWithTokenPair(c.Request.Context(), email, username, req.InvitationCode)
+	if err != nil {
+		response.ErrorFrom(c, err)
 		return
 	}
-	h.authService.RecordSuccessfulLogin(c.Request.Context(), user.ID)
-	if _, err := pendingSvc.ConsumeBrowserSession(c.Request.Context(), sessionToken, browserSessionKey); err != nil {
-		clearOAuthPendingSessionCookie(c, secureCookie)
-		clearOAuthPendingBrowserCookie(c, secureCookie)
-		response.ErrorFrom(c, err)
+	if err := applyPendingOAuthAdoptionAndConsumeSession(c.Request.Context(), client, h.authService, h.userService, session, decision, user.ID); err != nil {
+		respondPendingOAuthBindingApplyError(c, err)
 		return
 	}
+	h.authService.RecordSuccessfulLogin(c.Request.Context(), user.ID)
 	clearOAuthPendingSessionCookie(c, secureCookie)
 	clearOAuthPendingBrowserCookie(c, secureCookie)
 
@@ -546,7 +566,9 @@ func linuxDoExchangeCode(
 	form.Set("client_id", cfg.ClientID)
 	form.Set("code", code)
 	form.Set("redirect_uri", redirectURI)
+	if strings.TrimSpace(codeVerifier) != "" {
 		form.Set("code_verifier", codeVerifier)
+	}
 
 	r := client.R().
 		SetContext(ctx).
@@ -699,8 +721,10 @@ func buildLinuxDoAuthorizeURL(cfg config.LinuxDoConnectConfig, state string, cod
 		q.Set("scope", cfg.Scopes)
 	}
 	q.Set("state", state)
+	if strings.TrimSpace(codeChallenge) != "" {
 		q.Set("code_challenge", codeChallenge)
 		q.Set("code_challenge_method", "S256")
+	}
 
 	u.RawQuery = q.Encode()
 	return u.String(), nil
@@ -937,7 +961,19 @@ func clearOAuthBindAccessTokenCookie(c *gin.Context, secure bool) {
 		Value:    "",
 		Path:     oauthBindAccessTokenCookiePath,
 		MaxAge:   -1,
-		HttpOnly: false,
+		HttpOnly: true,
+		Secure:   secure,
+		SameSite: http.SameSiteLaxMode,
+	})
+}
+
+func setOAuthBindAccessTokenCookie(c *gin.Context, token string, secure bool) {
+	http.SetCookie(c.Writer, &http.Cookie{
+		Name:     oauthBindAccessTokenCookieName,
+		Value:    url.QueryEscape(strings.TrimSpace(token)),
+		Path:     oauthBindAccessTokenCookiePath,
+		MaxAge:   linuxDoOAuthCookieMaxAgeSec,
+		HttpOnly: true,
 		Secure:   secure,
 		SameSite: http.SameSiteLaxMode,
 	})
@@ -1021,6 +1057,26 @@ func (h *AuthHandler) buildOAuthBindUserCookieFromContext(c *gin.Context) (strin
 	return buildOAuthBindUserCookieValue(*userID, h.oauthBindCookieSecret())
 }
 
+func (h *AuthHandler) PrepareOAuthBindAccessTokenCookie(c *gin.Context) {
+	const bearerPrefix = "Bearer "
+
+	authHeader := strings.TrimSpace(c.GetHeader("Authorization"))
+	if !strings.HasPrefix(strings.ToLower(authHeader), strings.ToLower(bearerPrefix)) {
+		response.ErrorFrom(c, infraerrors.Unauthorized("UNAUTHORIZED", "authentication required"))
+		return
+	}
+
+	token := strings.TrimSpace(authHeader[len(bearerPrefix):])
+	if token == "" {
+		response.ErrorFrom(c, infraerrors.Unauthorized("UNAUTHORIZED", "authentication required"))
+		return
+	}
+
+	setOAuthBindAccessTokenCookie(c, token, isRequestHTTPS(c))
+	c.Status(http.StatusNoContent)
+	c.Writer.WriteHeaderNow()
+}
+
 func (h *AuthHandler) resolveOAuthBindTargetUserID(c *gin.Context) (*int64, error) {
 	if subject, ok := servermiddleware.GetAuthSubjectFromContext(c); ok && subject.UserID > 0 {
 		return &subject.UserID, nil

backend/internal/handler/auth_linuxdo_oauth_test.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"strings"
 	"testing"
 	"time"
@@ -170,6 +171,80 @@ func TestLinuxDoOAuthBindStartRedirectsAndSetsBindCookies(t *testing.T) {
 	require.Equal(t, int64(42), userID)
 }
 
+func TestLinuxDoOAuthStartOmitsPKCEWhenDisabled(t *testing.T) {
+	handler := newLinuxDoOAuthTestHandler(t, false, config.LinuxDoConnectConfig{
+		Enabled:             true,
+		ClientID:            "linuxdo-client",
+		ClientSecret:        "linuxdo-secret",
+		AuthorizeURL:        "https://connect.linux.do/oauth/authorize",
+		TokenURL:            "https://connect.linux.do/oauth/token",
+		UserInfoURL:         "https://connect.linux.do/api/user",
+		Scopes:              "read",
+		RedirectURL:         "https://api.example.com/api/v1/auth/oauth/linuxdo/callback",
+		FrontendRedirectURL: "/auth/linuxdo/callback",
+		TokenAuthMethod:     "client_secret_post",
+		UsePKCE:             false,
+	})
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodGet, "/api/v1/auth/oauth/linuxdo/start?redirect=/dashboard", nil)
+
+	handler.LinuxDoOAuthStart(c)
+
+	require.Equal(t, http.StatusFound, recorder.Code)
+	require.NotContains(t, recorder.Header().Get("Location"), "code_challenge=")
+	require.Nil(t, findCookie(recorder.Result().Cookies(), linuxDoOAuthVerifierCookie))
+}
+
+func TestLinuxDoOAuthCallbackAllowsMissingVerifierWhenPKCEDisabled(t *testing.T) {
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/token":
+			require.NoError(t, r.ParseForm())
+			require.Empty(t, r.PostForm.Get("code_verifier"))
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"access_token":"linuxdo-access","token_type":"Bearer","expires_in":3600}`))
+		case "/userinfo":
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"id":"compat-subject","username":"linuxdo_user","name":"LinuxDo Display"}`))
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	defer upstream.Close()
+
+	handler, client := newLinuxDoOAuthHandlerAndClient(t, false, config.LinuxDoConnectConfig{
+		Enabled:             true,
+		ClientID:            "linuxdo-client",
+		ClientSecret:        "linuxdo-secret",
+		AuthorizeURL:        upstream.URL + "/authorize",
+		TokenURL:            upstream.URL + "/token",
+		UserInfoURL:         upstream.URL + "/userinfo",
+		Scopes:              "read",
+		RedirectURL:         "https://api.example.com/api/v1/auth/oauth/linuxdo/callback",
+		FrontendRedirectURL: "/auth/linuxdo/callback",
+		TokenAuthMethod:     "client_secret_post",
+		UsePKCE:             false,
+	})
+	t.Cleanup(func() { _ = client.Close() })
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/auth/oauth/linuxdo/callback?code=linuxdo-code&state=state-123", nil)
+	req.AddCookie(encodedCookie(linuxDoOAuthStateCookieName, "state-123"))
+	req.AddCookie(encodedCookie(linuxDoOAuthRedirectCookie, "/dashboard"))
+	req.AddCookie(encodedCookie(linuxDoOAuthIntentCookieName, oauthIntentLogin))
+	req.AddCookie(encodedCookie(oauthPendingBrowserCookieName, "browser-123"))
+	c.Request = req
+
+	handler.LinuxDoOAuthCallback(c)
+
+	require.Equal(t, http.StatusFound, recorder.Code)
+	require.Equal(t, "/auth/linuxdo/callback", recorder.Header().Get("Location"))
+	require.NotNil(t, findCookie(recorder.Result().Cookies(), oauthPendingSessionCookieName))
+}
+
 func TestLinuxDoOAuthBindStartAcceptsAccessTokenCookie(t *testing.T) {
 	handler, client := newLinuxDoOAuthHandlerAndClient(t, false, config.LinuxDoConnectConfig{
 		Enabled:             true,
@@ -226,6 +301,27 @@ func TestLinuxDoOAuthBindStartAcceptsAccessTokenCookie(t *testing.T) {
 	require.Equal(t, -1, accessTokenCookie.MaxAge)
 }
 
+func TestPrepareOAuthBindAccessTokenCookieSetsHttpOnlyCookie(t *testing.T) {
+	handler, client := newLinuxDoOAuthHandlerAndClient(t, false, config.LinuxDoConnectConfig{})
+	t.Cleanup(func() { _ = client.Close() })
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/oauth/bind-token", nil)
+	req.Header.Set("Authorization", "Bearer access-token-value")
+	c.Request = req
+
+	handler.PrepareOAuthBindAccessTokenCookie(c)
+
+	require.Equal(t, http.StatusNoContent, recorder.Code)
+	accessTokenCookie := findCookie(recorder.Result().Cookies(), oauthBindAccessTokenCookieName)
+	require.NotNil(t, accessTokenCookie)
+	require.Equal(t, oauthBindAccessTokenCookiePath, accessTokenCookie.Path)
+	require.Equal(t, linuxDoOAuthCookieMaxAgeSec, accessTokenCookie.MaxAge)
+	require.True(t, accessTokenCookie.HttpOnly)
+	require.Equal(t, url.QueryEscape("access-token-value"), accessTokenCookie.Value)
+}
+
 func TestLinuxDoOAuthCallbackCreatesLoginPendingSessionForExistingIdentityUser(t *testing.T) {
 	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		switch r.URL.Path {
@@ -305,10 +401,81 @@ func TestLinuxDoOAuthCallbackCreatesLoginPendingSessionForExistingIdentityUser(t
 	completion, ok := session.LocalFlowState[oauthCompletionResponseKey].(map[string]any)
 	require.True(t, ok)
 	require.Equal(t, "/dashboard", completion["redirect"])
-	require.NotEmpty(t, completion["access_token"])
+	_, hasAccessToken := completion["access_token"]
+	require.False(t, hasAccessToken)
+	_, hasRefreshToken := completion["refresh_token"]
+	require.False(t, hasRefreshToken)
 	require.Nil(t, completion["error"])
 }
 
+func TestLinuxDoOAuthCallbackRejectsDisabledExistingIdentityUser(t *testing.T) {
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/token":
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"access_token":"linuxdo-access","token_type":"Bearer","expires_in":3600}`))
+		case "/userinfo":
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"id":"654","username":"linuxdo_disabled","name":"LinuxDo Disabled"}`))
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	defer upstream.Close()
+
+	handler, client := newLinuxDoOAuthHandlerAndClient(t, false, config.LinuxDoConnectConfig{
+		Enabled:             true,
+		ClientID:            "linuxdo-client",
+		ClientSecret:        "linuxdo-secret",
+		AuthorizeURL:        upstream.URL + "/authorize",
+		TokenURL:            upstream.URL + "/token",
+		UserInfoURL:         upstream.URL + "/userinfo",
+		Scopes:              "read",
+		RedirectURL:         "https://api.example.com/api/v1/auth/oauth/linuxdo/callback",
+		FrontendRedirectURL: "/auth/linuxdo/callback",
+		TokenAuthMethod:     "client_secret_post",
+		UsePKCE:             true,
+	})
+	t.Cleanup(func() { _ = client.Close() })
+
+	ctx := context.Background()
+	existingUser, err := client.User.Create().
+		SetEmail(linuxDoSyntheticEmail("654")).
+		SetUsername("disabled-user").
+		SetPasswordHash("hash").
+		SetRole(service.RoleUser).
+		SetStatus(service.StatusDisabled).
+		Save(ctx)
+	require.NoError(t, err)
+	_, err = client.AuthIdentity.Create().
+		SetUserID(existingUser.ID).
+		SetProviderType("linuxdo").
+		SetProviderKey("linuxdo").
+		SetProviderSubject("654").
+		Save(ctx)
+	require.NoError(t, err)
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/auth/oauth/linuxdo/callback?code=code-disabled&state=state-disabled", nil)
+	req.AddCookie(encodedCookie(linuxDoOAuthStateCookieName, "state-disabled"))
+	req.AddCookie(encodedCookie(linuxDoOAuthRedirectCookie, "/dashboard"))
+	req.AddCookie(encodedCookie(linuxDoOAuthVerifierCookie, "verifier-disabled"))
+	req.AddCookie(encodedCookie(linuxDoOAuthIntentCookieName, oauthIntentLogin))
+	req.AddCookie(encodedCookie(oauthPendingBrowserCookieName, "browser-disabled"))
+	c.Request = req
+
+	handler.LinuxDoOAuthCallback(c)
+
+	require.Equal(t, http.StatusFound, recorder.Code)
+	require.Nil(t, findCookie(recorder.Result().Cookies(), oauthPendingSessionCookieName))
+	assertOAuthRedirectError(t, recorder.Header().Get("Location"), "session_error", "USER_NOT_ACTIVE")
+
+	count, err := client.PendingAuthSession.Query().Count(ctx)
+	require.NoError(t, err)
+	require.Zero(t, count)
+}
+
 func TestLinuxDoOAuthCallbackCreatesBindPendingSessionForCompatEmailUser(t *testing.T) {
 	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		switch r.URL.Path {
@@ -341,7 +508,7 @@ func TestLinuxDoOAuthCallbackCreatesBindPendingSessionForCompatEmailUser(t *test
 
 	ctx := context.Background()
 	existingUser, err := client.User.Create().
-		SetEmail("legacy@example.com").
+		SetEmail(" Legacy@Example.com ").
 		SetUsername("legacy-user").
 		SetPasswordHash("hash").
 		SetRole(service.RoleUser).
@@ -372,16 +539,17 @@ func TestLinuxDoOAuthCallbackCreatesBindPendingSessionForCompatEmailUser(t *test
 		Only(ctx)
 	require.NoError(t, err)
 	require.Equal(t, oauthIntentLogin, session.Intent)
-	require.Nil(t, session.TargetUserID)
-	require.Equal(t, existingUser.Email, session.ResolvedEmail)
+	require.NotNil(t, session.TargetUserID)
+	require.Equal(t, existingUser.ID, *session.TargetUserID)
+	require.Equal(t, strings.TrimSpace(existingUser.Email), session.ResolvedEmail)
 	require.Equal(t, "legacy@example.com", session.UpstreamIdentityClaims["compat_email"])
 
 	completion, ok := session.LocalFlowState[oauthCompletionResponseKey].(map[string]any)
 	require.True(t, ok)
 	require.Equal(t, "/dashboard", completion["redirect"])
 	require.Equal(t, oauthPendingChoiceStep, completion["step"])
-	require.Equal(t, existingUser.Email, completion["email"])
-	require.Equal(t, existingUser.Email, completion["existing_account_email"])
+	require.Equal(t, strings.TrimSpace(existingUser.Email), completion["email"])
+	require.Equal(t, strings.TrimSpace(existingUser.Email), completion["existing_account_email"])
 	require.Equal(t, true, completion["existing_account_bindable"])
 	require.Equal(t, "compat_email_match", completion["choice_reason"])
 	_, hasAccessToken := completion["access_token"]
@@ -658,6 +826,186 @@ func TestCompleteLinuxDoOAuthRegistrationRejectsAdoptExistingUserSession(t *test
 	require.Nil(t, storedSession.ConsumedAt)
 }
 
+func TestCompleteLinuxDoOAuthRegistrationReturnsPendingSessionWhenChoiceStillRequired(t *testing.T) {
+	handler, client := newOAuthPendingFlowTestHandler(t, false)
+	ctx := context.Background()
+
+	session, err := client.PendingAuthSession.Create().
+		SetSessionToken("linuxdo-complete-choice-session").
+		SetIntent("login").
+		SetProviderType("linuxdo").
+		SetProviderKey("linuxdo").
+		SetProviderSubject("linuxdo-choice-subject-1").
+		SetResolvedEmail("linuxdo-choice-subject-1@linuxdo-connect.invalid").
+		SetBrowserSessionKey("linuxdo-choice-browser").
+		SetUpstreamIdentityClaims(map[string]any{
+			"username": "linuxdo_user",
+		}).
+		SetLocalFlowState(map[string]any{
+			oauthCompletionResponseKey: map[string]any{
+				"step":                  oauthPendingChoiceStep,
+				"redirect":              "/dashboard",
+				"email":                 "fresh@example.com",
+				"resolved_email":        "fresh@example.com",
+				"force_email_on_signup": true,
+			},
+		}).
+		SetExpiresAt(time.Now().UTC().Add(10 * time.Minute)).
+		Save(ctx)
+	require.NoError(t, err)
+
+	body := bytes.NewBufferString(`{"invitation_code":"invite-1"}`)
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/oauth/linuxdo/complete-registration", body)
+	req.Header.Set("Content-Type", "application/json")
+	req.AddCookie(&http.Cookie{Name: oauthPendingSessionCookieName, Value: encodeCookieValue(session.SessionToken)})
+	req.AddCookie(&http.Cookie{Name: oauthPendingBrowserCookieName, Value: encodeCookieValue("linuxdo-choice-browser")})
+	c.Request = req
+
+	handler.CompleteLinuxDoOAuthRegistration(c)
+
+	require.Equal(t, http.StatusOK, recorder.Code)
+	responseData := decodeJSONBody(t, recorder)
+	require.Equal(t, "pending_session", responseData["auth_result"])
+	require.Equal(t, oauthPendingChoiceStep, responseData["step"])
+	require.Equal(t, true, responseData["force_email_on_signup"])
+	require.Empty(t, responseData["access_token"])
+
+	userCount, err := client.User.Query().Count(ctx)
+	require.NoError(t, err)
+	require.Zero(t, userCount)
+
+	storedSession, err := client.PendingAuthSession.Get(ctx, session.ID)
+	require.NoError(t, err)
+	require.Nil(t, storedSession.ConsumedAt)
+}
+
+func TestCompleteLinuxDoOAuthRegistrationBindsIdentityWithoutAdoptionFlags(t *testing.T) {
+	handler, client := newOAuthPendingFlowTestHandler(t, false)
+	ctx := context.Background()
+
+	session, err := client.PendingAuthSession.Create().
+		SetSessionToken("linuxdo-complete-no-adoption-session").
+		SetIntent("login").
+		SetProviderType("linuxdo").
+		SetProviderKey("linuxdo").
+		SetProviderSubject("linuxdo-subject-no-adoption").
+		SetResolvedEmail("linuxdo-subject-no-adoption@linuxdo-connect.invalid").
+		SetBrowserSessionKey("linuxdo-browser-no-adoption").
+		SetUpstreamIdentityClaims(map[string]any{
+			"username":               "linuxdo_user",
+			"suggested_display_name": "LinuxDo Legacy",
+			"suggested_avatar_url":   "https://cdn.example/linuxdo-legacy.png",
+		}).
+		SetExpiresAt(time.Now().UTC().Add(10 * time.Minute)).
+		Save(ctx)
+	require.NoError(t, err)
+
+	body := bytes.NewBufferString(`{"invitation_code":"invite-1"}`)
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/oauth/linuxdo/complete-registration", body)
+	req.Header.Set("Content-Type", "application/json")
+	req.AddCookie(&http.Cookie{Name: oauthPendingSessionCookieName, Value: encodeCookieValue(session.SessionToken)})
+	req.AddCookie(&http.Cookie{Name: oauthPendingBrowserCookieName, Value: encodeCookieValue("linuxdo-browser-no-adoption")})
+	c.Request = req
+
+	handler.CompleteLinuxDoOAuthRegistration(c)
+
+	require.Equal(t, http.StatusOK, recorder.Code)
+	responseData := decodeJSONBody(t, recorder)
+	require.NotEmpty(t, responseData["access_token"])
+	require.NotEmpty(t, responseData["refresh_token"])
+
+	userEntity, err := client.User.Query().
+		Where(dbuser.EmailEQ(session.ResolvedEmail)).
+		Only(ctx)
+	require.NoError(t, err)
+	require.Equal(t, "linuxdo_user", userEntity.Username)
+
+	identity, err := client.AuthIdentity.Query().
+		Where(
+			authidentity.ProviderTypeEQ("linuxdo"),
+			authidentity.ProviderKeyEQ("linuxdo"),
+			authidentity.ProviderSubjectEQ("linuxdo-subject-no-adoption"),
+		).
+		Only(ctx)
+	require.NoError(t, err)
+	require.Equal(t, userEntity.ID, identity.UserID)
+
+	decision, err := client.IdentityAdoptionDecision.Query().
+		Where(identityadoptiondecision.PendingAuthSessionIDEQ(session.ID)).
+		Only(ctx)
+	require.NoError(t, err)
+	require.NotNil(t, decision.IdentityID)
+	require.Equal(t, identity.ID, *decision.IdentityID)
+	require.False(t, decision.AdoptDisplayName)
+	require.False(t, decision.AdoptAvatar)
+}
+
+func TestCompleteLinuxDoOAuthRegistrationRejectsIdentityOwnershipConflictBeforeUserCreation(t *testing.T) {
+	handler, client := newOAuthPendingFlowTestHandler(t, false)
+	ctx := context.Background()
+
+	existingOwner, err := client.User.Create().
+		SetEmail("owner@example.com").
+		SetUsername("owner-user").
+		SetPasswordHash("hash").
+		SetRole(service.RoleUser).
+		SetStatus(service.StatusActive).
+		Save(ctx)
+	require.NoError(t, err)
+
+	_, err = client.AuthIdentity.Create().
+		SetUserID(existingOwner.ID).
+		SetProviderType("linuxdo").
+		SetProviderKey("linuxdo").
+		SetProviderSubject("linuxdo-conflict-subject").
+		Save(ctx)
+	require.NoError(t, err)
+
+	session, err := client.PendingAuthSession.Create().
+		SetSessionToken("linuxdo-complete-conflict-session").
+		SetIntent("login").
+		SetProviderType("linuxdo").
+		SetProviderKey("linuxdo").
+		SetProviderSubject("linuxdo-conflict-subject").
+		SetResolvedEmail("linuxdo-conflict-subject@linuxdo-connect.invalid").
+		SetBrowserSessionKey("linuxdo-conflict-browser").
+		SetUpstreamIdentityClaims(map[string]any{
+			"username": "linuxdo_user",
+		}).
+		SetExpiresAt(time.Now().UTC().Add(10 * time.Minute)).
+		Save(ctx)
+	require.NoError(t, err)
+
+	body := bytes.NewBufferString(`{"invitation_code":"invite-1"}`)
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/oauth/linuxdo/complete-registration", body)
+	req.Header.Set("Content-Type", "application/json")
+	req.AddCookie(&http.Cookie{Name: oauthPendingSessionCookieName, Value: encodeCookieValue(session.SessionToken)})
+	req.AddCookie(&http.Cookie{Name: oauthPendingBrowserCookieName, Value: encodeCookieValue("linuxdo-conflict-browser")})
+	c.Request = req
+
+	handler.CompleteLinuxDoOAuthRegistration(c)
+
+	require.Equal(t, http.StatusConflict, recorder.Code)
+	payload := decodeJSONBody(t, recorder)
+	require.Equal(t, "AUTH_IDENTITY_OWNERSHIP_CONFLICT", payload["reason"])
+
+	userCount, err := client.User.Query().
+		Where(dbuser.EmailEQ("linuxdo-conflict-subject@linuxdo-connect.invalid")).
+		Count(ctx)
+	require.NoError(t, err)
+	require.Zero(t, userCount)
+
+	storedSession, err := client.PendingAuthSession.Get(ctx, session.ID)
+	require.NoError(t, err)
+	require.Nil(t, storedSession.ConsumedAt)
+}
+
 func newLinuxDoOAuthTestHandler(t *testing.T, invitationEnabled bool, oauthCfg config.LinuxDoConnectConfig) *AuthHandler {
 	t.Helper()
 	handler, _ := newLinuxDoOAuthHandlerAndClient(t, invitationEnabled, oauthCfg)