Presently, the JPATH_CACHE path constant is a "dynamic" constant based on the running application; it is always defined as JPATH_BASE . '/cache resulting in separate filesystem caches for the frontend, backend, and installation applications. This is the only cache store to create separate cache storage locations based on the active application; using any other handler stores all data in a single store regardless of application. Additionally, this behavior is inconsistent with the $cache_path configuration value that is now exposed in 3.7 which uses a single path for all filesystem related caching if set.

I propose that as of 4.0, JPATH_CACHE has a constant value of JPATH_ADMINISTRATOR . '/cache resulting in the filesystem cache using a single storage location for all data, removing the need for some conditional behaviors, and in general making this configuration more consistent with other adapters.