Taproot activation and Speedy Trial

Wonder

1. Why did the community agree on Schnorr signatures but fight for a year over how to turn them on?
2. What changes when miners get only four months to signal support instead of an open-ended window?
3. Why did Taproot wait five months between lock-in and activation?

Explore

1. Taproot, comprising BIPs 340, 341 and 342, introduced Schnorr signatures and new spending rules. Technically, the proposal faced little resistance; developers agreed on the merits of compact signatures and improved privacy. Yet activation remained stalled because the community had not settled how to deploy soft forks after the contentious SegWit era. The code was merged into Bitcoin Core in October 2020 and shipped, inactive, in version 0.21.0 (January 2021), but no consensus existed on whether to use BIP9 signaling or a user-activated mechanism.
2. The debate centered on ‘lockinontimeout’ (LOT), a variant of BIP8 where nodes force activation at the end of a signaling window regardless of miner support. Proponents argued this prevented miner veto; opponents feared it threatened network stability by forcing a split if miners disagreed. This tension had persisted since the 2017 SegWit deadlock, where prolonged negotiation and the threat of UASF ultimately forced a compromise. The community sought a method that respected both developer intent and economic reality without coercion.
3. ‘Speedy Trial’, devised by Russell O’Connor and written up by David Harding in March 2021, was the compromise. It modified BIP9 by using a short signaling window with a high threshold, allowing miners to signal readiness quickly. If they failed to do so, the proposal could be abandoned or revisited. This approach avoided the coercive nature of LOT while accelerating the process compared to standard BIP9, which had left SegWit unactivated for about nine months of signaling. The name reflected the compressed timeline: either activation succeeded swiftly, or data was generated for future proposals.
4. Speedy Trial shipped in Bitcoin Core version 0.21.1 in May 2021. It used signaling bit 2, set its start and timeout by median time past, and fixed a minimum activation height of 709,632 so that wallets and services had months to prepare. The window opened on 24 April 2021 and closed on 11 August 2021. Miners had about three and a half months to signal. If they did not reach the threshold, no automatic UASF was triggered, preserving the status quo but forcing a clear decision point.
5. Miners locked in Taproot during June 2021, well before the August deadline. The rapid signaling showed broad support among miners. Consequently, Taproot activated on 14 November 2021 at block 709,632, its minimum activation height. This marked a clear success for the Speedy Trial mechanism: it achieved activation without community splits or prolonged deadlock. Critics noted that even a short signaling window leaves miners an effective veto.
6. The debate over activation methods remains live for subsequent proposals like covenants. While Speedy Trial worked for Taproot due to its uncontroversial nature, its applicability to contentious changes is uncertain. Future developers must weigh the risk of miner veto against the threat of network instability. The 2021 episode demonstrated that economic nodes and miners can align quickly when technical merit is clear, but that alignment does not guarantee consensus on more divisive rule changes.

Key facts

Exercise nine, six, three, one

Fact check

Dates, figures and claims checked against the published sources listed below.

• BIP340: Schnorr Signatures for secp256k1 (P. Wuille, J. Nick & T. Ruffing)
• BIP341: Taproot: SegWit version 1 spending rules (P. Wuille, J. Nick & A. Towns)
• Bitcoin Core 0.21.1 Release Notes (May 2021)
• D. Harding, 'Speedy Trial' proposal on bitcoin-dev mailing list (March 2021)
• Optech Newsletter coverage of Taproot activation (November 2021)