BIP 8
Version bits with lock-in by height
Original title: Version bits with lock-in by height
- Status
- Complete
- Type / Layer
- Informational
- Author
- Shaolin Fry, Luke Dashjr
- Assigned
- Status verified
- Source
- github.com/bitcoin/bips/blob/master/bip-0008.mediawiki
Summary
An alternative to BIP9 for activating soft forks, written to correct what its authors saw as BIP9's mistakes. First, start and timeout are measured in block heights rather than POSIX timestamps: block time can be inaccurate, deliberately or not, and BIP9's "first retarget after a given time" trigger was unintuitive, whereas height increases by exactly one per block and makes thresholds exactly calculable. Second, it introduces an activation parameter (lockinontimeout) that can guarantee activation once the timeout is reached. Under BIP9, a proposal simply expires if miner signalling never crosses the threshold within the window, which hands a small minority of non-signalling hashrate an effective veto. BIP8 combines two paths: accelerated activation when a supermajority of hashrate signals, and flag-day activation after a reasonable period otherwise — resting on the premise that consensus rules are ultimately enforced by full nodes, not by miners.
Why it matters
It reframes soft-fork activation from "waiting for miner consensus" to a process where the economic majority can set a deadline. During the 2021 debate over how to activate Taproot it was one of the two main options considered, alongside the BIP9-derived Speedy Trial that was ultimately used.
Related BIPs
Related articles
This page carries a summary, not a translation. The original document is authoritative, and the metadata above — including Status — was transcribed from the bips repository on the verification date shown. Always consult the original when implementing or verifying.