The May 2021 hard fork was the first to be comprised of CHIPs.
A CasH Improvement Proposal (CHIP) is a change request for the Bitcoin Cash protocol. CHIPs can be written and published by any member of the Bitcoin Cash community. They are evaluated publicly, giving the authors an opportunity to make any clarifications or adjustments based on feedback from the rest of the community. Once there is sufficient support for a CHIP amongst node developers, it is scheduled for release in a future hard fork. Changes from multiple CHIPs may be included in a single hard fork.
Along with the creation of the CHIP system, the expectation of biannual releases was relaxed. If no CHIPs have support, there will be no hard-fork.
The May 2021 hard fork is comprised the following CHIPs:
- Unconfirmed Transaction Chain Limit
- Multiple OP_RETURNs for Bitcoin Cash