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SegWit2x Minority Fork Thrown Into Question as BTC1 Nodes Stall

Last Updated March 4, 2021 5:01 PM
Josiah Wilmoth
Last Updated March 4, 2021 5:01 PM

The chances of a SegWit2x minority fork materializing appear slim, as the fork-compatible software appears to be beset by bugs on the day of the fork’s scheduled activation.

While SegWit2x had been “called off” by its leading advocates last week, a small percentage of miners continued to signal for the fork, leaving the door open that the fork could proceed anyway. The probability was minor — and the chain would be unlikely to survive long anyway — but the threat was serious enough that Coinbase published an update yesterday  informing their users about potential post-fork scenarios. Consequently, all eyes were on the bitcoin blockchain as it approached block 494784 — the supposed trigger for the fork.

However, BTC1 nodes — nodes developed to be compatible with the SegWit2x chain — stalled at blockheight 494782, even though the main blockchain continued to add blocks.

Source: Coin Dance

John Newbery, a developer a Chaincode Labs, attributed the hiccup to an off-by-one error , noting that that the related piece of code was committed to the BTC1 codebase without review.

However, SegWit2x lead developer Jeff Garzik said that the nodes were operating as intended. Since the bitcoin genesis block has a height of “0,” block 494783 is technically counted as the 494784th block. 

Consequently, the nodes are stuck at blockheight 494782 while they await a block larger than 1MB to be mined. Garzik says that “No one is mining [the] canceled fork,” so the chain will continue sitting at 494782 indefinitely.

Nevertheless, the official SegWit2x announcement  did not make it clear that the fork would take place at the 494784th block — not block 494784. As several SegWit2x critics pointed out on Twitter, this confusion could have caused bitcoin exchanges and other third-party custodial services to take “snapshots” at the wrong block when determining how many airdropped coins each customer should receive after the fork.

But the problems did not stop there. There was apparently also a bug with the mining software that prevented miners from actually triggering the fork by mining a block larger than 1MB. This bug was also spotted by Newbery, and Garzik pushed out an update  to bypass that issue. Newbery claims to have identified more errors in the BTC1 codebase, but he says he will not reveal them since he has “no intention of helping create a disruptive hard fork.”

In any case, the markets are souring on the potential for SegWit2x proponents to create a viable blockchain. Yesterday, SegWit2x futures had been trading above $200 on Bitfinex. This was much lower than it had been prior to its “suspension,” but higher than the value of Bitcoin Gold — a fork that has already been deployed and is actively functioning as a distinct cryptocurrency. At present, SegWit2x futures are valued at just $130, which represents a 24-hour decline of nearly 50%.