Stream addon, prevent watched flag and XFILE::CFileFactory::CreateLoader error

I have two problems I think are somewhat related. I’m making an addon to play any online stream supported by streamlink, but once I build the list of playable URLs, all items that have the watched flag show an error and warning like the following:

Code:
11:35:05 T:8044 WARNING: XFILE::CFileFactory::CreateLoader - unsupported protocol(plugin) in plugin://plugin.video.streamlink-player/?action=play&url=http%3A%2F%2Fwww.npo.nl%2Flive%2Fnpo-1
11:35:05 T:8044   ERROR: InputStream: Error opening, plugin://plugin.video.streamlink-player/?action=play&url=http%3A%2F%2Fwww.npo.nl%2Flive%2Fnpo-1

I would like to somehow tell Kodi to not mark any stream as watched ever, since it makes little sense for such a plugin. This in itself would seem to take care of the other problem probably, but I’m also hoping to prevent that in a more elegant way. I’m assuming Kodi is trying to extract thumbnails and resolution and stuff, but the problem is that the URL will not be resolved until it is requested to be played. Since the URL is temporary and the resolving takes time, there’s also no way to do it during the creation of the list.

My addon.py and addon.xml.

Is there a native way to tell Kodi the plugin provides live streams?