Chaos is one of CCP's private test servers. In order to make it available to external testers, information about its patches would be available in the launcher, even though regular players could not log onto it.
As of mid May 2017, access to Chaos' patches & files has been restricted to authorized users only. This effectively means that we can no longer datamine anything on Chaos.
Chaos' files being public often meant that CCP had to delay QA & development efforts until things were in a much more finalized state, because of the speculation and complaints the datamining would inevitably bring. Although the change may be disappointing to some, the end result is likely to be a smoother development process, which is a good thing for everyone.
Singularity remains open for all your early speculation needs.
