Select factory-authorized dealers have access to assist clients in "speccing" their vehicles.
You are then guided through setting up your own username and password (which you should never share). You also enroll in 2FA and optionally whitelist your static IP. Koenigsegg Configurator Username And Password
Older models like the Agera or CCX occasionally have older, simplified configurators hosted on archival or enthusiast sites. Koenigsegg Configurator Username And Password