diff --git a/service/internal/api/api.go b/service/internal/api/api.go
index 629d039..f2c81da 100644
--- a/service/internal/api/api.go
+++ b/service/internal/api/api.go
@@ -392,6 +392,8 @@ func (api *oliveTinAPI) ExecutionStatus(ctx ctx.Context, req *connect.Request[ap
 func (api *oliveTinAPI) Logout(ctx ctx.Context, req *connect.Request[apiv1.LogoutRequest]) (*connect.Response[apiv1.LogoutResponse], error) {
 	user := auth.UserFromApiCall(ctx, req, api.cfg)
 
+	auth.RevokeSessionForProvider(api.cfg, user.Provider, user.SID)
+
 	log.WithFields(log.Fields{
 		"username": user.Username,
 		"provider": user.Provider,
diff --git a/service/internal/auth/otoauth2/restapi_auth_oauth2.go b/service/internal/auth/otoauth2/restapi_auth_oauth2.go
index a84e1f6..351a13b 100644
--- a/service/internal/auth/otoauth2/restapi_auth_oauth2.go
+++ b/service/internal/auth/otoauth2/restapi_auth_oauth2.go
@@ -391,6 +391,12 @@ func (h *OAuth2Handler) lookupOAuth2UserByState(state string) (*authTypes.Authen
 	return user, true
 }
 
+func (h *OAuth2Handler) RevokeSession(sid string) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	delete(h.registeredStates, sid)
+}
+
 func (h *OAuth2Handler) CheckUserFromOAuth2Cookie(context *authTypes.AuthCheckingContext) *authTypes.AuthenticatedUser {
 	cookie, err := context.Request.Cookie("olivetin-sid-oauth")
 	if err != nil || cookie.Value == "" {
diff --git a/service/internal/auth/sessions.go b/service/internal/auth/sessions.go
index f11fc8a..c8d7416 100644
--- a/service/internal/auth/sessions.go
+++ b/service/internal/auth/sessions.go
@@ -25,8 +25,9 @@ type SessionStorage struct {
 }
 
 var (
-	sessionStorage      *SessionStorage
-	sessionStorageMutex sync.RWMutex
+	sessionStorage       *SessionStorage
+	sessionStorageMutex  sync.RWMutex
+	oauth2SessionRevoker func(sid string)
 )
 
 func init() {
@@ -58,6 +59,38 @@ func RegisterUserSession(cfg *config.Config, provider string, sid string, userna
 	saveUserSessions(cfg)
 }
 
+// RegisterOAuth2SessionRevoker registers a callback to revoke OAuth2 sessions on logout.
+// OAuth2 uses its own session storage; the API calls this when provider is oauth2.
+func RegisterOAuth2SessionRevoker(fn func(sid string)) {
+	oauth2SessionRevoker = fn
+}
+
+// RevokeSessionForProvider invalidates the session for the given provider and SID (e.g. on logout).
+// Local auth uses shared SessionStorage; OAuth2 uses a separate storage and revoker.
+func RevokeSessionForProvider(cfg *config.Config, provider string, sid string) {
+	if sid == "" {
+		return
+	}
+	if provider == "oauth2" && oauth2SessionRevoker != nil {
+		oauth2SessionRevoker(sid)
+		return
+	}
+	RevokeUserSession(cfg, provider, sid)
+}
+
+// RevokeUserSession removes a session from storage so it can no longer be used (e.g. on logout).
+func RevokeUserSession(cfg *config.Config, provider string, sid string) {
+	sessionStorageMutex.Lock()
+	defer sessionStorageMutex.Unlock()
+
+	if sessionStorage.Providers[provider] != nil {
+		delete(sessionStorage.Providers[provider].Sessions, sid)
+		if cfg != nil {
+			saveUserSessions(cfg)
+		}
+	}
+}
+
 // GetUserSession retrieves a user session
 func GetUserSession(provider string, sid string) *UserSession {
 	sessionStorageMutex.Lock()
diff --git a/service/internal/httpservers/frontend.go b/service/internal/httpservers/frontend.go
index c1c1a1f..399c6fd 100644
--- a/service/internal/httpservers/frontend.go
+++ b/service/internal/httpservers/frontend.go
@@ -101,6 +101,7 @@ func StartFrontendMux(cfg *config.Config, ex *executor.Executor) {
 
 	oauth2handler := otoauth2.NewOAuth2Handler(cfg)
 	auth.AddAuthChainFunction(oauth2handler.CheckUserFromOAuth2Cookie)
+	auth.RegisterOAuth2SessionRevoker(oauth2handler.RevokeSession)
 
 	mux.HandleFunc("/oauth/login", oauth2handler.HandleOAuthLogin)
 	mux.HandleFunc("/oauth/callback", oauth2handler.HandleOAuthCallback)