Bitcoin Classic
The early-2016 client that proposed a one-time 2 MB hard fork (BIP-109) after Bitcoin XT stalled.
The wiki's angle: Classic was the smaller ask after XT, and it was stalled less by code than by an industry letter: the Hong Kong Roundtable statement, signed days after Classic's first release, promised a Core hard fork instead.[3][2]
The proposal
BIP-109 raised the block size limit from 1,000,000 to 2,000,000 bytes and added a new limit of 1,300,000,000 bytes hashed to compute signatures per block[1]. Miners signalled with bit 0x10000000; once 750 of the preceding 1,000 blocks carried it, a 28-day grace period would begin[1]. If it was not triggered by 1 January 2018 the BIP was to be considered withdrawn[1].
The client
The first Bitcoin Classic release, version 0.11.2, was announced on 10 February 2016 as “focused on doubling the transaction capacity of Bitcoin”[2]. It was based on Bitcoin Core 0.11.2 and compatible with its blockchain files and wallet[2].
Outcome
Ten days after that release, the Hong Kong Roundtable statement committed its signers to run only Bitcoin Core-compatible consensus systems for the foreseeable future[3]. BIP-109 never activated and its status in the BIPs repository is Closed[1]. Bitcoin XT adopted Classic's 2 MB bump in January 2016[4].
References
- primaryBIP-109 (Two million byte size limit with sigop and sighash limits) [archived]
- primaryBitcoin Classic 0.11.2 release announcement (GitHub, 10 Feb 2016) [archived]
- primaryBitcoin Roundtable, “Bitcoin Roundtable Consensus”, Medium, 20 Feb 2016 (Wayback Machine copy)
- secondaryBitcoin Wiki (en.bitcoin.it), “Bitcoin XT” [archived]