Sitecore SXA - XP navigation bar site resolving

Sitecore Experience Editor - navigation bar site resolving issue

Situation

We inherited a Sitecore 10.2 setup with a number of sites created with old school MVC. Nothing really fancy, just a bunch of sites just as many other solutions probably. The setup is a little weird (just as many "inherited" solutions, right...) and the customer is not used to working in the XP editor. 

When we were asked to add one more site, we decided to go for a headless approach and installed JSS and SXA on the environment. This is all working fine - all sites are running fine and I dare to say the new site is much more towards all best practices. And also introducing the XP editor - especially to add new components to a page. With the SXA extensions that is working like a charm.

Although we noticed one little issue. The navigation bar in the XP editor didn't work as expected. 

We can open a page in the XP editor and it works - the url looks like

https://dev/?sc_mode=edit&sc_itemid=...&sc_lang=en&sc_version=1&sc_site=portal.

But when we then use the navigation bar to go to another page we get an error because the sc_site parameter in the url is wrong:

https://dev/site1/?sc_mode=edit&sc_itemid=...&sc_lang=en&sc_site=site1&sc_ee_fb=false.

When we manually change the sc_site parameter back to "portal" it works. It seems that it takes the first site in the site definition list.

Site configuration

First thing to check is the site configuration. That seemed to be fine - we also checked the SXA Site Manager and that as well was all ok. 

Note here that the mvc sites are in the config (files), the SXA site is configured in Sitecore (items). This makes is tricky to order them.

There is a SiteResolving config section from SXA where you can add sites that should be resolved after the SXA sites. Just to be sure we added all sites to that list in the config:

<siteResolving patch:source="Sitecore.XA.SitesToResolveAfterSxa.config">
  <site name="exm" resolve="after" />
  <site name="website" resolve="after" />
  ....
</siteResolving>

When all sites are added you can see in the SXA Site Manager that the SXA site moved up and that is now our first site.

Unfortunately, that didn't solve our issue. The site resolving in the navigation bar is still wrong. 

The solution

We contacted Sitecore Support. I thought about trying to find the responsible code to see if I could fix it myself - didn't do that as it would take too much time for something that is not convenient but also not blocking. 

And finally none of those options solved it, but well - let's call it luck. I can't remember why I decided to add a targetHostName in the site definition of the new SXA site. But I did - and actually that fixed our issue. The site resolving is working fine now.

We still don't know exactly why and don't want to spend time searching for a root cause but it is solved and might solve a site resolving issue for you as well. If anyone would know the root cause, please do share though.