diff --git a/backend/internal/config/config.go b/backend/internal/config/config.go
index f355a15d..32ad91b7 100644
--- a/backend/internal/config/config.go
+++ b/backend/internal/config/config.go
@@ -1202,7 +1202,7 @@ func setDefaults() {
 	viper.SetDefault("linuxdo_connect.redirect_url", "")
 	viper.SetDefault("linuxdo_connect.frontend_redirect_url", "/auth/linuxdo/callback")
 	viper.SetDefault("linuxdo_connect.token_auth_method", "client_secret_post")
-	viper.SetDefault("linuxdo_connect.use_pkce", true)
+	viper.SetDefault("linuxdo_connect.use_pkce", false)
 	viper.SetDefault("linuxdo_connect.userinfo_email_path", "")
 	viper.SetDefault("linuxdo_connect.userinfo_id_path", "")
 	viper.SetDefault("linuxdo_connect.userinfo_username_path", "")
@@ -1222,8 +1222,8 @@ 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", true)
-	viper.SetDefault("oidc_connect.validate_id_token", true)
+	viper.SetDefault("oidc_connect.use_pkce", false)
+	viper.SetDefault("oidc_connect.validate_id_token", false)
 	viper.SetDefault("oidc_connect.allowed_signing_algs", "RS256,ES256,PS256")
 	viper.SetDefault("oidc_connect.clock_skew_seconds", 120)
 	viper.SetDefault("oidc_connect.require_email_verified", false)
@@ -1613,9 +1613,6 @@ 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")
 		}
@@ -1668,12 +1665,6 @@ func (c *Config) Validate() error {
 		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.OIDC.ValidateIDToken {
-			return fmt.Errorf("oidc_connect.validate_id_token must be true when oidc_connect.enabled=true")
-		}
 		if strings.TrimSpace(c.OIDC.ClientID) == "" {
 			return fmt.Errorf("oidc_connect.client_id is required when oidc_connect.enabled=true")
 		}
diff --git a/backend/internal/config/config_test.go b/backend/internal/config/config_test.go
index fe48541b..f40a5f57 100644
--- a/backend/internal/config/config_test.go
+++ b/backend/internal/config/config_test.go
@@ -346,7 +346,7 @@ func TestValidateLinuxDoFrontendRedirectURL(t *testing.T) {
 	}
 }
 
-func TestValidateLinuxDoPKCERequiredForPublicClient(t *testing.T) {
+func TestValidateLinuxDoAllowsDisablingPKCEForCompatibility(t *testing.T) {
 	resetViperWithJWTSecret(t)
 
 	cfg, err := Load()
@@ -363,11 +363,8 @@ 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 +424,35 @@ func TestValidateOIDCAllowsIssuerOnlyEndpointsWithDiscoveryFallback(t *testing.T
 	}
 }
 
+func TestValidateOIDCAllowsDisablingPKCEAndIDTokenValidation(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)
 
diff --git a/backend/internal/handler/admin/setting_handler.go b/backend/internal/handler/admin/setting_handler.go
index e6609c97..f85f199b 100644
--- a/backend/internal/handler/admin/setting_handler.go
+++ b/backend/internal/handler/admin/setting_handler.go
@@ -653,20 +653,22 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 				req.WeChatConnectScopes = service.DefaultWeChatConnectScopesForMode(req.WeChatConnectMode)
 			}
 		}
-		if req.WeChatConnectRedirectURL == "" {
-			response.BadRequest(c, "WeChat Redirect URL is required when enabled")
-			return
-		}
-		if err := config.ValidateAbsoluteHTTPURL(req.WeChatConnectRedirectURL); err != nil {
-			response.BadRequest(c, "WeChat Redirect URL must be an absolute http(s) URL")
-			return
-		}
-		if req.WeChatConnectFrontendRedirectURL == "" {
-			req.WeChatConnectFrontendRedirectURL = "/auth/wechat/callback"
-		}
-		if err := config.ValidateFrontendRedirectURL(req.WeChatConnectFrontendRedirectURL); err != nil {
-			response.BadRequest(c, "WeChat Frontend Redirect URL is invalid")
-			return
+		if req.WeChatConnectOpenEnabled || req.WeChatConnectMPEnabled {
+			if req.WeChatConnectRedirectURL == "" {
+				response.BadRequest(c, "WeChat Redirect URL is required when web oauth is enabled")
+				return
+			}
+			if err := config.ValidateAbsoluteHTTPURL(req.WeChatConnectRedirectURL); err != nil {
+				response.BadRequest(c, "WeChat Redirect URL must be an absolute http(s) URL")
+				return
+			}
+			if req.WeChatConnectFrontendRedirectURL == "" {
+				req.WeChatConnectFrontendRedirectURL = "/auth/wechat/callback"
+			}
+			if err := config.ValidateFrontendRedirectURL(req.WeChatConnectFrontendRedirectURL); err != nil {
+				response.BadRequest(c, "WeChat Frontend Redirect URL is invalid")
+				return
+			}
 		}
 	}
 
@@ -749,14 +751,6 @@ 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 +761,7 @@ 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 req.OIDCConnectValidateIDToken && req.OIDCConnectAllowedSigningAlgs == "" {
 			response.BadRequest(c, "OIDC Allowed Signing Algs is required when validate_id_token=true")
 			return
 		}
diff --git a/backend/internal/handler/auth_linuxdo_oauth.go b/backend/internal/handler/auth_linuxdo_oauth.go
index 2bd44e78..ef9a5bca 100644
--- a/backend/internal/handler/auth_linuxdo_oauth.go
+++ b/backend/internal/handler/auth_linuxdo_oauth.go
@@ -123,13 +123,16 @@ func (h *AuthHandler) LinuxDoOAuthStart(c *gin.Context) {
 		clearCookie(c, linuxDoOAuthBindUserCookieName, secureCookie)
 	}
 
-	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 := ""
+	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)
+		setCookie(c, linuxDoOAuthVerifierCookie, encodeCookieValue(verifier), linuxDoOAuthCookieMaxAgeSec, secureCookie)
 	}
-	codeChallenge := oauth.GenerateCodeChallenge(verifier)
-	setCookie(c, linuxDoOAuthVerifierCookie, encodeCookieValue(verifier), linuxDoOAuthCookieMaxAgeSec, secureCookie)
 
 	redirectURI := strings.TrimSpace(cfg.RedirectURL)
 	if redirectURI == "" {
@@ -200,10 +203,13 @@ func (h *AuthHandler) LinuxDoOAuthCallback(c *gin.Context) {
 	intent, _ := readCookieDecoded(c, linuxDoOAuthIntentCookieName)
 	intent = normalizeOAuthIntent(intent)
 
-	codeVerifier, _ := readCookieDecoded(c, linuxDoOAuthVerifierCookie)
-	if codeVerifier == "" {
-		redirectOAuthError(c, frontendCallback, "missing_verifier", "missing pkce verifier", "")
-		return
+	codeVerifier := ""
+	if cfg.UsePKCE {
+		codeVerifier, _ = readCookieDecoded(c, linuxDoOAuthVerifierCookie)
+		if codeVerifier == "" {
+			redirectOAuthError(c, frontendCallback, "missing_verifier", "missing pkce verifier", "")
+			return
+		}
 	}
 
 	redirectURI := strings.TrimSpace(cfg.RedirectURL)
@@ -292,25 +298,16 @@ 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,
+				"redirect": redirectTo,
 			},
 		}); err != nil {
 			redirectOAuthError(c, frontendCallback, "session_error", "failed to continue oauth login", "")
@@ -546,7 +543,9 @@ func linuxDoExchangeCode(
 	form.Set("client_id", cfg.ClientID)
 	form.Set("code", code)
 	form.Set("redirect_uri", redirectURI)
-	form.Set("code_verifier", codeVerifier)
+	if strings.TrimSpace(codeVerifier) != "" {
+		form.Set("code_verifier", codeVerifier)
+	}
 
 	r := client.R().
 		SetContext(ctx).
@@ -699,8 +698,10 @@ func buildLinuxDoAuthorizeURL(cfg config.LinuxDoConnectConfig, state string, cod
 		q.Set("scope", cfg.Scopes)
 	}
 	q.Set("state", state)
-	q.Set("code_challenge", codeChallenge)
-	q.Set("code_challenge_method", "S256")
+	if strings.TrimSpace(codeChallenge) != "" {
+		q.Set("code_challenge", codeChallenge)
+		q.Set("code_challenge_method", "S256")
+	}
 
 	u.RawQuery = q.Encode()
 	return u.String(), nil
diff --git a/backend/internal/handler/auth_linuxdo_oauth_test.go b/backend/internal/handler/auth_linuxdo_oauth_test.go
index a3d87dfb..841dc442 100644
--- a/backend/internal/handler/auth_linuxdo_oauth_test.go
+++ b/backend/internal/handler/auth_linuxdo_oauth_test.go
@@ -171,6 +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,
@@ -327,7 +401,10 @@ 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"])
 }
 
diff --git a/backend/internal/handler/auth_oidc_oauth.go b/backend/internal/handler/auth_oidc_oauth.go
index d2042a87..7fe4b8d9 100644
--- a/backend/internal/handler/auth_oidc_oauth.go
+++ b/backend/internal/handler/auth_oidc_oauth.go
@@ -157,21 +157,25 @@ func (h *AuthHandler) OIDCOAuthStart(c *gin.Context) {
 	}
 
 	codeChallenge := ""
-	verifier, genErr := oauth.GenerateCodeVerifier()
-	if genErr != nil {
-		response.ErrorFrom(c, infraerrors.InternalServer("OAUTH_PKCE_GEN_FAILED", "failed to generate pkce verifier").WithCause(genErr))
-		return
+	if cfg.UsePKCE {
+		verifier, genErr := oauth.GenerateCodeVerifier()
+		if genErr != nil {
+			response.ErrorFrom(c, infraerrors.InternalServer("OAUTH_PKCE_GEN_FAILED", "failed to generate pkce verifier").WithCause(genErr))
+			return
+		}
+		codeChallenge = oauth.GenerateCodeChallenge(verifier)
+		oidcSetCookie(c, oidcOAuthVerifierCookie, encodeCookieValue(verifier), oidcOAuthCookieMaxAgeSec, secureCookie)
 	}
-	codeChallenge = oauth.GenerateCodeChallenge(verifier)
-	oidcSetCookie(c, oidcOAuthVerifierCookie, encodeCookieValue(verifier), oidcOAuthCookieMaxAgeSec, secureCookie)
 
 	nonce := ""
-	nonce, err = oauth.GenerateState()
-	if err != nil {
-		response.ErrorFrom(c, infraerrors.InternalServer("OAUTH_NONCE_GEN_FAILED", "failed to generate oauth nonce").WithCause(err))
-		return
+	if cfg.ValidateIDToken {
+		nonce, err = oauth.GenerateState()
+		if err != nil {
+			response.ErrorFrom(c, infraerrors.InternalServer("OAUTH_NONCE_GEN_FAILED", "failed to generate oauth nonce").WithCause(err))
+			return
+		}
+		oidcSetCookie(c, oidcOAuthNonceCookie, encodeCookieValue(nonce), oidcOAuthCookieMaxAgeSec, secureCookie)
 	}
-	oidcSetCookie(c, oidcOAuthNonceCookie, encodeCookieValue(nonce), oidcOAuthCookieMaxAgeSec, secureCookie)
 
 	redirectURI := strings.TrimSpace(cfg.RedirectURL)
 	if redirectURI == "" {
@@ -244,17 +248,21 @@ func (h *AuthHandler) OIDCOAuthCallback(c *gin.Context) {
 	intent = normalizeOAuthIntent(intent)
 
 	codeVerifier := ""
-	codeVerifier, _ = readCookieDecoded(c, oidcOAuthVerifierCookie)
-	if codeVerifier == "" {
-		redirectOAuthError(c, frontendCallback, "missing_verifier", "missing pkce verifier", "")
-		return
+	if cfg.UsePKCE {
+		codeVerifier, _ = readCookieDecoded(c, oidcOAuthVerifierCookie)
+		if codeVerifier == "" {
+			redirectOAuthError(c, frontendCallback, "missing_verifier", "missing pkce verifier", "")
+			return
+		}
 	}
 
 	expectedNonce := ""
-	expectedNonce, _ = readCookieDecoded(c, oidcOAuthNonceCookie)
-	if expectedNonce == "" {
-		redirectOAuthError(c, frontendCallback, "missing_nonce", "missing oauth nonce", "")
-		return
+	if cfg.ValidateIDToken {
+		expectedNonce, _ = readCookieDecoded(c, oidcOAuthNonceCookie)
+		if expectedNonce == "" {
+			redirectOAuthError(c, frontendCallback, "missing_nonce", "missing oauth nonce", "")
+			return
+		}
 	}
 
 	redirectURI := strings.TrimSpace(cfg.RedirectURL)
@@ -284,16 +292,19 @@ func (h *AuthHandler) OIDCOAuthCallback(c *gin.Context) {
 		return
 	}
 
-	if strings.TrimSpace(tokenResp.IDToken) == "" {
-		redirectOAuthError(c, frontendCallback, "missing_id_token", "missing id_token", "")
-		return
-	}
+	var idClaims *oidcIDTokenClaims
+	if cfg.ValidateIDToken {
+		if strings.TrimSpace(tokenResp.IDToken) == "" {
+			redirectOAuthError(c, frontendCallback, "missing_id_token", "missing id_token", "")
+			return
+		}
 
-	idClaims, err := oidcParseAndValidateIDToken(c.Request.Context(), cfg, tokenResp.IDToken, expectedNonce)
-	if err != nil {
-		log.Printf("[OIDC OAuth] id_token validation failed: %v", err)
-		redirectOAuthError(c, frontendCallback, "invalid_id_token", "failed to validate id_token", "")
-		return
+		idClaims, err = oidcParseAndValidateIDToken(c.Request.Context(), cfg, tokenResp.IDToken, expectedNonce)
+		if err != nil {
+			log.Printf("[OIDC OAuth] id_token validation failed: %v", err)
+			redirectOAuthError(c, frontendCallback, "invalid_id_token", "failed to validate id_token", "")
+			return
+		}
 	}
 
 	userInfoClaims, err := oidcFetchUserInfo(c.Request.Context(), cfg, tokenResp)
@@ -303,7 +314,10 @@ func (h *AuthHandler) OIDCOAuthCallback(c *gin.Context) {
 		return
 	}
 
-	subject := strings.TrimSpace(idClaims.Subject)
+	subject := ""
+	if idClaims != nil {
+		subject = strings.TrimSpace(idClaims.Subject)
+	}
 	if subject == "" {
 		subject = strings.TrimSpace(userInfoClaims.Subject)
 	}
@@ -311,7 +325,10 @@ func (h *AuthHandler) OIDCOAuthCallback(c *gin.Context) {
 		redirectOAuthError(c, frontendCallback, "missing_subject", "missing subject claim", "")
 		return
 	}
-	issuer := strings.TrimSpace(idClaims.Issuer)
+	issuer := ""
+	if idClaims != nil {
+		issuer = strings.TrimSpace(idClaims.Issuer)
+	}
 	if issuer == "" {
 		issuer = strings.TrimSpace(cfg.IssuerURL)
 	}
@@ -321,21 +338,34 @@ func (h *AuthHandler) OIDCOAuthCallback(c *gin.Context) {
 	}
 
 	emailVerified := userInfoClaims.EmailVerified
-	if emailVerified == nil {
+	if emailVerified == nil && idClaims != nil {
 		emailVerified = idClaims.EmailVerified
 	}
-	if userInfoClaims.Subject != "" && idClaims.Subject != "" && strings.TrimSpace(userInfoClaims.Subject) != strings.TrimSpace(idClaims.Subject) {
+	if idClaims != nil && userInfoClaims.Subject != "" && idClaims.Subject != "" && strings.TrimSpace(userInfoClaims.Subject) != strings.TrimSpace(idClaims.Subject) {
 		redirectOAuthError(c, frontendCallback, "subject_mismatch", "userinfo subject does not match id_token", "")
 		return
 	}
 
 	identityKey := oidcIdentityKey(issuer, subject)
-	compatEmail := strings.TrimSpace(firstNonEmpty(userInfoClaims.Email, idClaims.Email))
+	compatEmail := strings.TrimSpace(userInfoClaims.Email)
+	if compatEmail == "" && idClaims != nil {
+		compatEmail = strings.TrimSpace(idClaims.Email)
+	}
 	email := oidcSyntheticEmailFromIdentityKey(identityKey)
 	username := firstNonEmpty(
 		userInfoClaims.Username,
-		idClaims.PreferredUsername,
-		idClaims.Name,
+		func() string {
+			if idClaims != nil {
+				return idClaims.PreferredUsername
+			}
+			return ""
+		}(),
+		func() string {
+			if idClaims != nil {
+				return idClaims.Name
+			}
+			return ""
+		}(),
 		oidcFallbackUsername(subject),
 	)
 	identityRef := service.PendingAuthIdentityKey{
@@ -350,7 +380,12 @@ func (h *AuthHandler) OIDCOAuthCallback(c *gin.Context) {
 		"issuer":                 issuer,
 		"email_verified":         emailVerified != nil && *emailVerified,
 		"provider_fallback":      strings.TrimSpace(cfg.ProviderName),
-		"suggested_display_name": firstNonEmpty(userInfoClaims.DisplayName, idClaims.Name, username),
+		"suggested_display_name": firstNonEmpty(userInfoClaims.DisplayName, func() string {
+			if idClaims != nil {
+				return idClaims.Name
+			}
+			return ""
+		}(), username),
 		"suggested_avatar_url":   userInfoClaims.AvatarURL,
 	}
 	if compatEmail != "" && !strings.EqualFold(strings.TrimSpace(compatEmail), strings.TrimSpace(email)) {
@@ -387,25 +422,16 @@ func (h *AuthHandler) OIDCOAuthCallback(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:               identityRef,
-			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,
+				"redirect": redirectTo,
 			},
 		}); err != nil {
 			redirectOAuthError(c, frontendCallback, "session_error", "failed to continue oauth login", "")
@@ -670,7 +696,9 @@ func oidcExchangeCode(
 	form.Set("client_id", cfg.ClientID)
 	form.Set("code", code)
 	form.Set("redirect_uri", redirectURI)
-	form.Set("code_verifier", codeVerifier)
+	if strings.TrimSpace(codeVerifier) != "" {
+		form.Set("code_verifier", codeVerifier)
+	}
 
 	r := client.R().
 		SetContext(ctx).
@@ -872,9 +900,13 @@ func buildOIDCAuthorizeURL(cfg config.OIDCConnectConfig, state, nonce, codeChall
 		q.Set("scope", cfg.Scopes)
 	}
 	q.Set("state", state)
-	q.Set("nonce", nonce)
-	q.Set("code_challenge", codeChallenge)
-	q.Set("code_challenge_method", "S256")
+	if strings.TrimSpace(nonce) != "" {
+		q.Set("nonce", nonce)
+	}
+	if strings.TrimSpace(codeChallenge) != "" {
+		q.Set("code_challenge", codeChallenge)
+		q.Set("code_challenge_method", "S256")
+	}
 
 	u.RawQuery = q.Encode()
 	return u.String(), nil
diff --git a/backend/internal/handler/auth_oidc_oauth_test.go b/backend/internal/handler/auth_oidc_oauth_test.go
index 2acca18a..a600fd56 100644
--- a/backend/internal/handler/auth_oidc_oauth_test.go
+++ b/backend/internal/handler/auth_oidc_oauth_test.go
@@ -186,6 +186,89 @@ func TestOIDCOAuthBindStartRedirectsAndSetsBindCookies(t *testing.T) {
 	require.Equal(t, int64(84), userID)
 }
 
+func TestOIDCOAuthStartOmitsPKCEAndNonceWhenDisabled(t *testing.T) {
+	handler := newOIDCOAuthTestHandler(t, false, config.OIDCConnectConfig{
+		Enabled:              true,
+		ClientID:             "oidc-client",
+		ClientSecret:         "oidc-secret",
+		IssuerURL:            "https://issuer.example.com",
+		AuthorizeURL:         "https://issuer.example.com/oauth/authorize",
+		TokenURL:             "https://issuer.example.com/oauth/token",
+		UserInfoURL:          "https://issuer.example.com/oauth/userinfo",
+		Scopes:               "openid profile email",
+		RedirectURL:          "https://api.example.com/api/v1/auth/oauth/oidc/callback",
+		FrontendRedirectURL:  "/auth/oidc/callback",
+		TokenAuthMethod:      "client_secret_post",
+		UsePKCE:              false,
+		ValidateIDToken:      false,
+		RequireEmailVerified: false,
+	})
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodGet, "/api/v1/auth/oauth/oidc/start?redirect=/dashboard", nil)
+
+	handler.OIDCOAuthStart(c)
+
+	require.Equal(t, http.StatusFound, recorder.Code)
+	location := recorder.Header().Get("Location")
+	require.NotContains(t, location, "code_challenge=")
+	require.NotContains(t, location, "nonce=")
+	require.Nil(t, findCookie(recorder.Result().Cookies(), oidcOAuthVerifierCookie))
+	require.Nil(t, findCookie(recorder.Result().Cookies(), oidcOAuthNonceCookie))
+}
+
+func TestOIDCOAuthCallbackAllowsOptionalPKCEAndIDTokenValidation(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":"oidc-access","token_type":"Bearer","expires_in":3600}`))
+		case "/userinfo":
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"sub":"oidc-subject-compat","preferred_username":"oidc_user","name":"OIDC Display","email":"oidc@example.com"}`))
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	defer upstream.Close()
+
+	handler, client := newOIDCOAuthHandlerAndClient(t, false, config.OIDCConnectConfig{
+		Enabled:              true,
+		ClientID:             "oidc-client",
+		ClientSecret:         "oidc-secret",
+		IssuerURL:            "https://issuer.example.com",
+		AuthorizeURL:         upstream.URL + "/authorize",
+		TokenURL:             upstream.URL + "/token",
+		UserInfoURL:          upstream.URL + "/userinfo",
+		Scopes:               "openid profile email",
+		RedirectURL:          "https://api.example.com/api/v1/auth/oauth/oidc/callback",
+		FrontendRedirectURL:  "/auth/oidc/callback",
+		TokenAuthMethod:      "client_secret_post",
+		UsePKCE:              false,
+		ValidateIDToken:      false,
+		RequireEmailVerified: false,
+	})
+	t.Cleanup(func() { _ = client.Close() })
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/auth/oauth/oidc/callback?code=oidc-code&state=state-123", nil)
+	req.AddCookie(encodedCookie(oidcOAuthStateCookieName, "state-123"))
+	req.AddCookie(encodedCookie(oidcOAuthRedirectCookie, "/dashboard"))
+	req.AddCookie(encodedCookie(oidcOAuthIntentCookieName, oauthIntentLogin))
+	req.AddCookie(encodedCookie(oauthPendingBrowserCookieName, "browser-123"))
+	c.Request = req
+
+	handler.OIDCOAuthCallback(c)
+
+	require.Equal(t, http.StatusFound, recorder.Code)
+	require.Equal(t, "/auth/oidc/callback", recorder.Header().Get("Location"))
+	require.NotNil(t, findCookie(recorder.Result().Cookies(), oauthPendingSessionCookieName))
+}
+
 func TestOIDCOAuthCallbackCreatesLoginPendingSessionForExistingIdentityUser(t *testing.T) {
 	cfg, cleanup := newOIDCTestProvider(t, oidcProviderFixture{
 		Subject:           "oidc-subject-login",
@@ -250,7 +333,10 @@ func TestOIDCOAuthCallbackCreatesLoginPendingSessionForExistingIdentityUser(t *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"])
 }
 
diff --git a/backend/internal/handler/auth_wechat_oauth.go b/backend/internal/handler/auth_wechat_oauth.go
index 78f5d7c2..39703ce7 100644
--- a/backend/internal/handler/auth_wechat_oauth.go
+++ b/backend/internal/handler/auth_wechat_oauth.go
@@ -279,12 +279,7 @@ func (h *AuthHandler) WeChatOAuthCallback(c *gin.Context) {
 			redirectOAuthError(c, frontendCallback, "session_error", infraerrors.Reason(err), infraerrors.Message(err))
 			return
 		}
-		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.createWeChatPendingSession(c, normalizedIntent, providerSubject, existingIdentityUser.Email, redirectTo, browserSessionKey, upstreamClaims, tokenPair, nil, &user.ID); err != nil {
+		if err := h.createWeChatPendingSession(c, normalizedIntent, providerSubject, existingIdentityUser.Email, redirectTo, browserSessionKey, upstreamClaims, nil, nil, &existingIdentityUser.ID); err != nil {
 			redirectOAuthError(c, frontendCallback, "session_error", "failed to continue oauth login", "")
 			return
 		}
diff --git a/backend/internal/handler/auth_wechat_oauth_test.go b/backend/internal/handler/auth_wechat_oauth_test.go
index 937daa6d..99006701 100644
--- a/backend/internal/handler/auth_wechat_oauth_test.go
+++ b/backend/internal/handler/auth_wechat_oauth_test.go
@@ -213,6 +213,86 @@ func TestWeChatOAuthCallbackFallsBackToOpenIDWhenUnionIDMissingInSingleChannelMo
 	require.Equal(t, "third_party_signup", completion["choice_reason"])
 }
 
+func TestWeChatOAuthCallbackCreatesLoginPendingSessionForExistingIdentityUserWithoutStoredTokens(t *testing.T) {
+	originalAccessTokenURL := wechatOAuthAccessTokenURL
+	originalUserInfoURL := wechatOAuthUserInfoURL
+	t.Cleanup(func() {
+		wechatOAuthAccessTokenURL = originalAccessTokenURL
+		wechatOAuthUserInfoURL = originalUserInfoURL
+	})
+
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case strings.Contains(r.URL.Path, "/sns/oauth2/access_token"):
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"access_token":"wechat-access","openid":"openid-123","unionid":"union-456","scope":"snsapi_login"}`))
+		case strings.Contains(r.URL.Path, "/sns/userinfo"):
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"openid":"openid-123","unionid":"union-456","nickname":"WeChat Display","headimgurl":"https://cdn.example/wechat-login.png"}`))
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	defer upstream.Close()
+	wechatOAuthAccessTokenURL = upstream.URL + "/sns/oauth2/access_token"
+	wechatOAuthUserInfoURL = upstream.URL + "/sns/userinfo"
+
+	handler, client := newWeChatOAuthTestHandlerWithSettings(t, false, wechatOAuthTestSettings("open", "wx-open-app", "wx-open-secret", "https://app.example.com/auth/wechat/callback"))
+	defer client.Close()
+
+	ctx := context.Background()
+	existingUser, err := client.User.Create().
+		SetEmail(wechatSyntheticEmail("union-456")).
+		SetUsername("wechat-existing-user").
+		SetPasswordHash("hash").
+		SetRole(service.RoleUser).
+		SetStatus(service.StatusActive).
+		Save(ctx)
+	require.NoError(t, err)
+	_, err = client.AuthIdentity.Create().
+		SetUserID(existingUser.ID).
+		SetProviderType("wechat").
+		SetProviderKey(wechatOAuthProviderKey).
+		SetProviderSubject("union-456").
+		SetMetadata(map[string]any{"username": "wechat-existing-user"}).
+		Save(ctx)
+	require.NoError(t, err)
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/auth/oauth/wechat/callback?code=wechat-code&state=state-123", nil)
+	req.Host = "api.example.com"
+	req.AddCookie(encodedCookie(wechatOAuthStateCookieName, "state-123"))
+	req.AddCookie(encodedCookie(wechatOAuthRedirectCookieName, "/dashboard"))
+	req.AddCookie(encodedCookie(wechatOAuthModeCookieName, "open"))
+	req.AddCookie(encodedCookie(oauthPendingBrowserCookieName, "browser-123"))
+	c.Request = req
+
+	handler.WeChatOAuthCallback(c)
+
+	require.Equal(t, http.StatusFound, recorder.Code)
+	require.Equal(t, "https://app.example.com/auth/wechat/callback", recorder.Header().Get("Location"))
+
+	sessionCookie := findCookie(recorder.Result().Cookies(), oauthPendingSessionCookieName)
+	require.NotNil(t, sessionCookie)
+
+	session, err := client.PendingAuthSession.Query().
+		Where(pendingauthsession.SessionTokenEQ(decodeCookieValueForTest(t, sessionCookie.Value))).
+		Only(ctx)
+	require.NoError(t, err)
+	require.Equal(t, oauthIntentLogin, session.Intent)
+	require.NotNil(t, session.TargetUserID)
+	require.Equal(t, existingUser.ID, *session.TargetUserID)
+	require.Equal(t, existingUser.Email, session.ResolvedEmail)
+
+	completion := session.LocalFlowState[oauthCompletionResponseKey].(map[string]any)
+	require.Equal(t, "/dashboard", completion["redirect"])
+	_, hasAccessToken := completion["access_token"]
+	require.False(t, hasAccessToken)
+	_, hasRefreshToken := completion["refresh_token"]
+	require.False(t, hasRefreshToken)
+}
+
 func TestWeChatPaymentOAuthCallbackRedirectsWithOpaqueResumeToken(t *testing.T) {
 	originalAccessTokenURL := wechatOAuthAccessTokenURL
 	t.Cleanup(func() {
diff --git a/backend/internal/service/setting_service.go b/backend/internal/service/setting_service.go
index fe566fec..059bbcd3 100644
--- a/backend/internal/service/setting_service.go
+++ b/backend/internal/service/setting_service.go
@@ -631,7 +631,7 @@ func (s *SettingService) weChatOAuthCapabilitiesFromSettings(settings map[string
 	mpReady := mpEnabled && webRedirectReady && mpAppID != "" && mpAppSecret != ""
 	mobileReady := mobileEnabled && mobileAppID != "" && mobileAppSecret != ""
 
-	return openReady || mpReady || mobileReady, openReady, mpReady, mobileReady
+	return openReady || mpReady, openReady, mpReady, mobileReady
 }
 
 // filterUserVisibleMenuItems filters out admin-only menu items from a raw JSON
@@ -1693,8 +1693,6 @@ func (s *SettingService) parseSettings(settings map[string]string) *SystemSettin
 	} else {
 		result.OIDCConnectValidateIDToken = oidcBase.ValidateIDToken
 	}
-	result.OIDCConnectUsePKCE = true
-	result.OIDCConnectValidateIDToken = true
 	if v, ok := settings[SettingKeyOIDCConnectAllowedSigningAlgs]; ok && strings.TrimSpace(v) != "" {
 		result.OIDCConnectAllowedSigningAlgs = strings.TrimSpace(v)
 	} else {
@@ -2196,8 +2194,6 @@ func (s *SettingService) GetLinuxDoConnectOAuthConfig(ctx context.Context) (conf
 	if v, ok := settings[SettingKeyLinuxDoConnectRedirectURL]; ok && strings.TrimSpace(v) != "" {
 		effective.RedirectURL = strings.TrimSpace(v)
 	}
-	effective.UsePKCE = true
-
 	if !effective.Enabled {
 		return config.LinuxDoConnectConfig{}, infraerrors.NotFound("OAUTH_DISABLED", "oauth login is disabled")
 	}
@@ -2421,8 +2417,6 @@ func (s *SettingService) GetOIDCConnectOAuthConfig(ctx context.Context) (config.
 	if raw, ok := settings[SettingKeyOIDCConnectValidateIDToken]; ok {
 		effective.ValidateIDToken = raw == "true"
 	}
-	effective.UsePKCE = true
-	effective.ValidateIDToken = true
 	if v, ok := settings[SettingKeyOIDCConnectAllowedSigningAlgs]; ok && strings.TrimSpace(v) != "" {
 		effective.AllowedSigningAlgs = strings.TrimSpace(v)
 	}
diff --git a/backend/internal/service/setting_service_oidc_config_test.go b/backend/internal/service/setting_service_oidc_config_test.go
index 3809b332..a5a3959a 100644
--- a/backend/internal/service/setting_service_oidc_config_test.go
+++ b/backend/internal/service/setting_service_oidc_config_test.go
@@ -101,3 +101,47 @@ func TestGetOIDCConnectOAuthConfig_ResolvesEndpointsFromIssuerDiscovery(t *testi
 	require.Equal(t, srv.URL+"/issuer/protocol/openid-connect/userinfo", got.UserInfoURL)
 	require.Equal(t, srv.URL+"/issuer/protocol/openid-connect/certs", got.JWKSURL)
 }
+
+func TestSettingService_ParseSettings_PreservesOptionalOIDCCompatibilityFlags(t *testing.T) {
+	svc := NewSettingService(&settingOIDCRepoStub{values: map[string]string{}}, &config.Config{})
+
+	got := svc.parseSettings(map[string]string{
+		SettingKeyOIDCConnectEnabled:         "true",
+		SettingKeyOIDCConnectUsePKCE:         "false",
+		SettingKeyOIDCConnectValidateIDToken: "false",
+	})
+
+	require.False(t, got.OIDCConnectUsePKCE)
+	require.False(t, got.OIDCConnectValidateIDToken)
+}
+
+func TestGetOIDCConnectOAuthConfig_AllowsCompatibilityFlagsToDisablePKCEAndIDTokenValidation(t *testing.T) {
+	cfg := &config.Config{
+		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",
+			RedirectURL:         "https://example.com/api/v1/auth/oauth/oidc/callback",
+			FrontendRedirectURL: "/auth/oidc/callback",
+			Scopes:              "openid email profile",
+			TokenAuthMethod:     "client_secret_post",
+		},
+	}
+
+	repo := &settingOIDCRepoStub{values: map[string]string{
+		SettingKeyOIDCConnectEnabled:         "true",
+		SettingKeyOIDCConnectUsePKCE:         "false",
+		SettingKeyOIDCConnectValidateIDToken: "false",
+	}}
+	svc := NewSettingService(repo, cfg)
+
+	got, err := svc.GetOIDCConnectOAuthConfig(context.Background())
+	require.NoError(t, err)
+	require.False(t, got.UsePKCE)
+	require.False(t, got.ValidateIDToken)
+}
diff --git a/backend/internal/service/setting_service_public_test.go b/backend/internal/service/setting_service_public_test.go
index 497d1e36..4c7ca14b 100644
--- a/backend/internal/service/setting_service_public_test.go
+++ b/backend/internal/service/setting_service_public_test.go
@@ -112,3 +112,23 @@ func TestSettingService_GetPublicSettings_ExposesWeChatOAuthModeCapabilities(t *
 	require.True(t, settings.WeChatOAuthOpenEnabled)
 	require.True(t, settings.WeChatOAuthMPEnabled)
 }
+
+func TestSettingService_GetPublicSettings_DoesNotExposeMobileOnlyWeChatAsWebOAuthAvailable(t *testing.T) {
+	svc := NewSettingService(&settingPublicRepoStub{
+		values: map[string]string{
+			SettingKeyWeChatConnectEnabled:             "true",
+			SettingKeyWeChatConnectMobileEnabled:       "true",
+			SettingKeyWeChatConnectMode:                "mobile",
+			SettingKeyWeChatConnectMobileAppID:         "wx-mobile-app",
+			SettingKeyWeChatConnectMobileAppSecret:     "wx-mobile-secret",
+			SettingKeyWeChatConnectFrontendRedirectURL: "/auth/wechat/callback",
+		},
+	}, &config.Config{})
+
+	settings, err := svc.GetPublicSettings(context.Background())
+	require.NoError(t, err)
+	require.False(t, settings.WeChatOAuthEnabled)
+	require.False(t, settings.WeChatOAuthOpenEnabled)
+	require.False(t, settings.WeChatOAuthMPEnabled)
+	require.True(t, settings.WeChatOAuthMobileEnabled)
+}
diff --git a/backend/internal/service/user_service.go b/backend/internal/service/user_service.go
index bc444af5..c16d810b 100644
--- a/backend/internal/service/user_service.go
+++ b/backend/internal/service/user_service.go
@@ -248,12 +248,59 @@ func (s *UserService) GetProfileIdentitySummaries(ctx context.Context, userID in
 		return UserIdentitySummarySet{}, err
 	}
 
-	return UserIdentitySummarySet{
+	summaries := UserIdentitySummarySet{
 		Email:   s.buildEmailIdentitySummary(user, records),
 		LinuxDo: s.buildProviderIdentitySummary("linuxdo", user, records),
 		OIDC:    s.buildProviderIdentitySummary("oidc", user, records),
 		WeChat:  s.buildProviderIdentitySummary("wechat", user, records),
-	}, nil
+	}
+
+	s.applyExplicitProviderAvailability(ctx, &summaries)
+	return summaries, nil
+}
+
+func (s *UserService) applyExplicitProviderAvailability(ctx context.Context, summaries *UserIdentitySummarySet) {
+	if s == nil || summaries == nil || s.settingRepo == nil {
+		return
+	}
+
+	settings, err := s.settingRepo.GetMultiple(ctx, []string{
+		SettingKeyLinuxDoConnectEnabled,
+		SettingKeyOIDCConnectEnabled,
+		SettingKeyWeChatConnectEnabled,
+		SettingKeyWeChatConnectOpenEnabled,
+		SettingKeyWeChatConnectMPEnabled,
+		SettingKeyWeChatConnectMobileEnabled,
+		SettingKeyWeChatConnectMode,
+	})
+	if err != nil {
+		return
+	}
+
+	if raw, ok := settings[SettingKeyLinuxDoConnectEnabled]; ok && strings.TrimSpace(raw) != "" && raw != "true" {
+		disableIdentityBindAction(&summaries.LinuxDo)
+	}
+	if raw, ok := settings[SettingKeyOIDCConnectEnabled]; ok && strings.TrimSpace(raw) != "" && raw != "true" {
+		disableIdentityBindAction(&summaries.OIDC)
+	}
+	if raw, ok := settings[SettingKeyWeChatConnectEnabled]; ok && strings.TrimSpace(raw) != "" {
+		if raw != "true" {
+			disableIdentityBindAction(&summaries.WeChat)
+			return
+		}
+		openEnabled, mpEnabled, _ := parseWeChatConnectCapabilitySettings(settings, true, settings[SettingKeyWeChatConnectMode])
+		if !openEnabled && !mpEnabled {
+			disableIdentityBindAction(&summaries.WeChat)
+		}
+	}
+}
+
+func disableIdentityBindAction(summary *UserIdentitySummary) {
+	if summary == nil || summary.Bound {
+		return
+	}
+	summary.CanBind = false
+	summary.BindStartPath = ""
 }
 
 func (s *UserService) PrepareIdentityBindingStart(_ context.Context, req StartUserIdentityBindingRequest) (*StartUserIdentityBindingResult, error) {
diff --git a/backend/internal/service/user_service_test.go b/backend/internal/service/user_service_test.go
index 88bb1637..109d459d 100644
--- a/backend/internal/service/user_service_test.go
+++ b/backend/internal/service/user_service_test.go
@@ -51,6 +51,44 @@ type mockUserRepoTxState struct {
 	deleteAvatarIDs  []int64
 }
 
+type mockUserSettingRepo struct {
+	values map[string]string
+}
+
+func (m *mockUserSettingRepo) Get(context.Context, string) (*Setting, error) {
+	panic("unexpected Get call")
+}
+
+func (m *mockUserSettingRepo) GetValue(context.Context, string) (string, error) {
+	panic("unexpected GetValue call")
+}
+
+func (m *mockUserSettingRepo) Set(context.Context, string, string) error {
+	panic("unexpected Set call")
+}
+
+func (m *mockUserSettingRepo) GetMultiple(_ context.Context, keys []string) (map[string]string, error) {
+	out := make(map[string]string, len(keys))
+	for _, key := range keys {
+		if value, ok := m.values[key]; ok {
+			out[key] = value
+		}
+	}
+	return out, nil
+}
+
+func (m *mockUserSettingRepo) SetMultiple(context.Context, map[string]string) error {
+	panic("unexpected SetMultiple call")
+}
+
+func (m *mockUserSettingRepo) GetAll(context.Context) (map[string]string, error) {
+	panic("unexpected GetAll call")
+}
+
+func (m *mockUserSettingRepo) Delete(context.Context, string) error {
+	panic("unexpected Delete call")
+}
+
 func (m *mockUserRepo) Create(context.Context, *User) error { return nil }
 func (m *mockUserRepo) GetByID(ctx context.Context, _ int64) (*User, error) {
 	if m.getByIDErr != nil {
@@ -382,6 +420,35 @@ func TestUnbindUserAuthProviderRemovesProviderAndReturnsUpdatedProfile(t *testin
 	require.True(t, summaries.LinuxDo.CanBind)
 }
 
+func TestGetProfileIdentitySummaries_HidesBindActionWhenProviderExplicitlyDisabled(t *testing.T) {
+	repo := &mockUserRepo{
+		getByIDUser: &User{
+			ID:    15,
+			Email: "alice@example.com",
+		},
+		identities: []UserAuthIdentityRecord{
+			{
+				ProviderType:    "email",
+				ProviderKey:     "email",
+				ProviderSubject: "alice@example.com",
+			},
+		},
+	}
+	settingRepo := &mockUserSettingRepo{
+		values: map[string]string{
+			SettingKeyLinuxDoConnectEnabled: "false",
+		},
+	}
+	svc := NewUserService(repo, settingRepo, nil, nil)
+
+	summaries, err := svc.GetProfileIdentitySummaries(context.Background(), 15, repo.getByIDUser)
+
+	require.NoError(t, err)
+	require.False(t, summaries.LinuxDo.Bound)
+	require.False(t, summaries.LinuxDo.CanBind)
+	require.Empty(t, summaries.LinuxDo.BindStartPath)
+}
+
 func TestUpdateBalance_NilBillingCache_NoPanic(t *testing.T) {
 	repo := &mockUserRepo{}
 	svc := NewUserService(repo, nil, nil, nil) // billingCache = nil
diff --git a/frontend/src/components/user/profile/ProfileIdentityBindingsSection.vue b/frontend/src/components/user/profile/ProfileIdentityBindingsSection.vue
index 848789d9..48b1b879 100644
--- a/frontend/src/components/user/profile/ProfileIdentityBindingsSection.vue
+++ b/frontend/src/components/user/profile/ProfileIdentityBindingsSection.vue
@@ -362,6 +362,16 @@ function getBindingDetails(provider: UserAuthProvider): UserAuthBindingStatus |
   return binding
 }
 
+function isProviderEnabledForBinding(provider: BindableProvider): boolean {
+  if (provider === 'linuxdo') {
+    return props.linuxdoEnabled
+  }
+  if (provider === 'oidc') {
+    return props.oidcEnabled
+  }
+  return resolvedWeChatBinding.value.mode !== null
+}
+
 const providerItems = computed(() => [
   {
     provider: 'email' as const,
@@ -375,7 +385,10 @@ const providerItems = computed(() => [
     provider: 'linuxdo' as const,
     label: t('profile.authBindings.providers.linuxdo'),
     bound: getBindingStatus('linuxdo'),
-    canBind: getBindingDetails('linuxdo')?.can_bind ?? (props.linuxdoEnabled && !getBindingStatus('linuxdo')),
+    canBind:
+      !getBindingStatus('linuxdo') &&
+      isProviderEnabledForBinding('linuxdo') &&
+      (getBindingDetails('linuxdo')?.can_bind ?? true),
     canUnbind: Boolean(getBindingStatus('linuxdo') && getBindingDetails('linuxdo')?.can_unbind),
     details: getBindingDetails('linuxdo'),
   },
@@ -383,7 +396,10 @@ const providerItems = computed(() => [
     provider: 'oidc' as const,
     label: t('profile.authBindings.providers.oidc', { providerName: props.oidcProviderName }),
     bound: getBindingStatus('oidc'),
-    canBind: getBindingDetails('oidc')?.can_bind ?? (props.oidcEnabled && !getBindingStatus('oidc')),
+    canBind:
+      !getBindingStatus('oidc') &&
+      isProviderEnabledForBinding('oidc') &&
+      (getBindingDetails('oidc')?.can_bind ?? true),
     canUnbind: Boolean(getBindingStatus('oidc') && getBindingDetails('oidc')?.can_unbind),
     details: getBindingDetails('oidc'),
   },
@@ -391,7 +407,10 @@ const providerItems = computed(() => [
     provider: 'wechat' as const,
     label: t('profile.authBindings.providers.wechat'),
     bound: getBindingStatus('wechat'),
-    canBind: getBindingDetails('wechat')?.can_bind ?? (resolvedWeChatBinding.value.mode !== null && !getBindingStatus('wechat')),
+    canBind:
+      !getBindingStatus('wechat') &&
+      isProviderEnabledForBinding('wechat') &&
+      (getBindingDetails('wechat')?.can_bind ?? true),
     canUnbind: Boolean(getBindingStatus('wechat') && getBindingDetails('wechat')?.can_unbind),
     details: getBindingDetails('wechat'),
   },
diff --git a/frontend/src/components/user/profile/__tests__/ProfileIdentityBindingsSection.spec.ts b/frontend/src/components/user/profile/__tests__/ProfileIdentityBindingsSection.spec.ts
index 345e0209..9d8c88d4 100644
--- a/frontend/src/components/user/profile/__tests__/ProfileIdentityBindingsSection.spec.ts
+++ b/frontend/src/components/user/profile/__tests__/ProfileIdentityBindingsSection.spec.ts
@@ -474,4 +474,26 @@ describe('ProfileIdentityBindingsSection', () => {
     expect(userApiMocks.unbindAuthIdentity).toHaveBeenCalledWith('linuxdo')
     expect(wrapper.get('[data-testid="profile-binding-linuxdo-status"]').text()).toBe('Not bound')
   })
+
+  it('hides bind actions when provider details say bindable but the provider is disabled', () => {
+    const wrapper = mount(ProfileIdentityBindingsSection, {
+      global: {
+        plugins: [pinia],
+      },
+      props: {
+        user: createUser({
+          auth_bindings: {
+            linuxdo: { bound: false, can_bind: true },
+            oidc: { bound: false, can_bind: true },
+          },
+        }),
+        linuxdoEnabled: false,
+        oidcEnabled: false,
+        wechatEnabled: false,
+      },
+    })
+
+    expect(wrapper.find('[data-testid="profile-binding-linuxdo-action"]').exists()).toBe(false)
+    expect(wrapper.find('[data-testid="profile-binding-oidc-action"]').exists()).toBe(false)
+  })
 })
diff --git a/frontend/src/views/admin/SettingsView.vue b/frontend/src/views/admin/SettingsView.vue
index a13f1981..5772c501 100644
--- a/frontend/src/views/admin/SettingsView.vue
+++ b/frontend/src/views/admin/SettingsView.vue
@@ -2032,7 +2032,7 @@
                     </div>
                     <Toggle
                       v-model="form.oidc_connect_use_pkce"
-                      :disabled="true"
+                      data-testid="oidc-connect-use-pkce"
                     />
                   </div>
 
@@ -2046,7 +2046,7 @@
                     </div>
                     <Toggle
                       v-model="form.oidc_connect_validate_id_token"
-                      :disabled="true"
+                      data-testid="oidc-connect-validate-id-token"
                     />
                   </div>
 
@@ -4961,8 +4961,8 @@ const form = reactive<SettingsForm>({
   oidc_connect_redirect_url: "",
   oidc_connect_frontend_redirect_url: "/auth/oidc/callback",
   oidc_connect_token_auth_method: "client_secret_post",
-  oidc_connect_use_pkce: true,
-  oidc_connect_validate_id_token: true,
+  oidc_connect_use_pkce: false,
+  oidc_connect_validate_id_token: false,
   oidc_connect_allowed_signing_algs: "RS256,ES256,PS256",
   oidc_connect_clock_skew_seconds: 120,
   oidc_connect_require_email_verified: false,
@@ -5846,8 +5846,8 @@ async function saveSettings() {
       oidc_connect_frontend_redirect_url:
         form.oidc_connect_frontend_redirect_url,
       oidc_connect_token_auth_method: form.oidc_connect_token_auth_method,
-      oidc_connect_use_pkce: true,
-      oidc_connect_validate_id_token: true,
+      oidc_connect_use_pkce: form.oidc_connect_use_pkce,
+      oidc_connect_validate_id_token: form.oidc_connect_validate_id_token,
       oidc_connect_allowed_signing_algs: form.oidc_connect_allowed_signing_algs,
       oidc_connect_clock_skew_seconds: form.oidc_connect_clock_skew_seconds,
       oidc_connect_require_email_verified:
diff --git a/frontend/src/views/admin/__tests__/SettingsView.spec.ts b/frontend/src/views/admin/__tests__/SettingsView.spec.ts
index 27a43c9f..10c51b2a 100644
--- a/frontend/src/views/admin/__tests__/SettingsView.spec.ts
+++ b/frontend/src/views/admin/__tests__/SettingsView.spec.ts
@@ -776,4 +776,28 @@ describe("admin SettingsView wechat connect controls", () => {
     ).toBe(true);
     expect(wrapper.text()).toContain("首次绑定时授权");
   });
+
+  it("preserves optional OIDC compatibility flags instead of forcing them on save", async () => {
+    getSettings.mockResolvedValueOnce({
+      ...baseSettingsResponse,
+      oidc_connect_enabled: true,
+      oidc_connect_use_pkce: false,
+      oidc_connect_validate_id_token: false,
+    });
+
+    const wrapper = mountView();
+
+    await flushPromises();
+    await openSecurityTab(wrapper);
+    await wrapper.find("form").trigger("submit.prevent");
+    await flushPromises();
+
+    expect(updateSettings).toHaveBeenCalledTimes(1);
+    expect(updateSettings).toHaveBeenCalledWith(
+      expect.objectContaining({
+        oidc_connect_use_pkce: false,
+        oidc_connect_validate_id_token: false,
+      }),
+    );
+  });
 });