MediaWiki 1.26, in where ResourceLoader became fully asynchronous.
* $wgMasterWaitTimeout was removed (deprecated in 1.24).
* Fields in ParserOptions are now private. Use the accessors instead.
+* Custom LESS functions (defined via $wgResourceLoaderLESSFunctions)
+ have been removed, after being deprecated in 1.24.
=== New features in 1.26 ===
* (T51506) Now action=info gives estimates of actual watchers for a page.
* (T53283) load.php sometimes sends 304 response without full headers
* (T65198) Talk page tabs now have a "rel=discussion" attribute
* (T98841) {{msgnw:}} now preserves comments even when subst: is not used.
+* (T104142) $wgEmergencyContact and $wgPasswordSender now use their default
+ value if set to an empty string.
=== Action API changes in 1.26 ===
* New-style continuation is now the default for action=continue. Clients may