I'm using OutboundPathProcessorInterface. I notice a few odd things about its behavior.
- In adding, for example, "/x" to the path, it works in some cases, like admin/structure, but not others, like admin/content or the path I'm interested in, which is defined in a view. This is despite my setting the module's weight to 999 in its install file (before installing), so presumably no other module would be altering the path downstream.
- Where it does work, such as admin/structure, the page with the original path loads, with the original URL in the address bar, but all menu links have the altered path.
- When I watch it in xdebug, AFTER I alter the path with the query string in $options the URL comes through the function again, with the path set to the original value.