The latest (tip-of-tree) protocol changes frequently and may break at any time. However it captures the full capabilities of the Protocol, whereas the stable release is a subset. There is no backwards compatibility support guaranteed for the capabilities it introduces.
Latest browser_protocol.json version updated:
Date: Fri Mar 24 14:50:42 2017 -0700
Latest js_protocol.json version updated:
Date: Thu Mar 9 21:19:04 2017 -0800