The BIP110ers are proceeding with their proof of work change hard fork.

Here is a list of changes:

1. Flag-day hard fork:
   At block 961,640, the consensus rules change. SHA256d blocks become invalid from that height onward.
2. BLAKE2b proof of work:
   SHA256d mining is replaced with BLAKE2b. The initial target is shifted by 22 bits, equivalent to roughly 218 TH/s for 10-minute blocks.

The existing 2,016-block difficulty-adjustment system remains unchanged.

3. New block-header format:
   Post-fork blocks use a mandatory 164-byte version-2 header instead of Bitcoin’s traditional 80-byte header.

It adds the block height, transaction count, expanded nonce fields, ASIC profiles, time-offset data, an XOR key and a merge-mining field.

4. Transaction-count commitment:
   The header directly commits to the number of transactions in the block. This addresses the Merkle-tree ambiguity behind CVE-2017-12842.
5. Block-withholding mitigation:
   Miners can optionally use a secret XOR key so workers cannot identify complete valid blocks and selectively withhold them.
6. Unified sighash:
   A new opt-in SIGHASH_UNIFIED format works across legacy, SegWit and Taproot inputs.

It provides linear signature hashing, commits to every input amount and gives one-way replay protection.

Old signatures remain valid, so these protections only apply when the spender opts in.

7. Temporary RDTS rules:
   From block 961,640 until the parent block’s median-time-past reaches 1 September 2027, blocks are limited to 800,000 weight units, approximately 300 kB.
8. Temporary script restrictions:
   During RDTS:

• Stack elements are limited to 256 bytes.
• Taproot trees are limited to seven levels.
• Taproot annexes are forbidden.
• OP_IF and OP_NOTIF are forbidden in Tapscript.
• Unknown witness and Taproot upgrade mechanisms are invalid.
• Inputs spending coins created before the fork are grandfathered.

9. Activation headline:
   The first BLAKE2b block must contain a specific, externally configured news headline in its coinbase transaction.
10. Future hooks:
    The new header reserves infrastructure for merge-mined sidechains and 40-bit timestamps, but those features are not fully activated yet.

Summary by zender on X.

Here is Luke Dashjr's post about the new coin:

source

If you look at mempool.guide, you may notice something about the blocks after 961640:

All blocks seem to be less than 800k weight units.

This is quite a bit less than the 4 million WU of Bitcoin blocks. While there doesn't seem to be any explicit change to the block size limit in the release candidate, it's a little odd that all the new BIP110 blocks are adhering to this lower limit.