[ryebit]

The hard fork the NY agreement mentions was a protocol upgrade that was scheduled for 11/16/2017. The Segwit upgrade took hold, but the second "2mb hard fork" part proved very contentious, and was later cancelled/suspended citing lack of community support. (That fork was frequently called B2X or S2X).

There is some argument about who all actually signed on to the NY agreement - whether they represented the community at large, or just a smaller non-binding group. The contentiousness was overtly regarding the "2mb" increase's long-term consequences, but IMO it may have also been because adopting it would have essentially kicked out the existing software development group, replacing with a smaller less experienced group.

If the hard fork had happened, the NY agreement asserted it would have simply upgraded the BTC protocol; rather than create a new coin. Agreeing exchanges would have had to go along with the protocol upgrade. But concensus never formed, particularly among exchanges & businesses that didn't sign the NYA.

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Bitcoin Cash / BCH was a separate coin that forked off of BTC around the same time as the NYA, but wasn't part of the NYA. It increased the block size (the "2mb" bit), but explicitly rejects segregated witness and some related changes. It's kinda odd it happened, because those involved in BCH were leaders in the NY agreement itself; so BCH be seen as an early repudiation of the NY agreement by it's own champions.