Manual:$wgResourceLoaderMaxQueryLength/en

Details
Maximum query string length for resource loader requests.

If set to a positive number, ResourceLoader will not generate URLs whose query string is more than this many characters long, and will instead use multiple requests with shorter query strings. This degrades performance, but may be needed if your web server has a low - less than let's say 1024 - query string length limit or a low value for suhosin.get.max_value_length that you can't increase.

If set to a negative number, ResourceLoader will assume there is no query string length limit.

When installing MediaWiki, the installer will automatically detect an appropriate value for this setting, and set it in the automatically generated  file.