From: Sjors Provoost <sjors@sprovoost.nl>
To: Bitcoin Development Mailing List <bitcoindev@googlegroups.com>
Cc: Matt Corallo <lf-lists@mattcorallo.com>,
Anthony Towns <aj@erisian.com.au>
Subject: Re: [bitcoindev] [BIP Draft] 24 bits for nVersion nonce space instead of 16
Date: Wed, 8 Apr 2026 18:16:01 +0200 [thread overview]
Message-ID: <D52CEDCC-C7EF-429E-802F-F28DC9241FF0@sprovoost.nl> (raw)
In-Reply-To: <acfCTzCqIalFuOdi@erisian.com.au>
This could lead to friction around who gets to allocate these scarce 5 bits, as well as
potential confusion when people and client software interpret contentious bits differently.
What if we reserve bit 0 to indicate that the actual signal can be found in the coinbase
transaction? The signal itself can be as simple as OP_RETURN BIP-XXXX.
The chosen string doesn't matter. We can keep referring to "deployment bits", where
bits > 28 represent the new method. That gives us practically unlimited bits and no
need to ever repurpose them.
A quick vibe coding session suggests this is straightforward to implement. [0]
The two implementation caveats:
- BIP22 will need an extension to feed the new coinbase OP_RETURN fields to
mining pool software (IPC clients like Stratum v2 work out of the box)
- headers are no longer sufficient to track signalling [1]
- Sjors
[0] https://github.com/Sjors/bitcoin/commits/2026/05/version/
[1] v31.0 will make the coinbase is easily accessible via RPC: https://github.com/bitcoin/bitcoin/pull/34512
> Op 28 mrt 2026, om 12:58 heeft Anthony Towns <aj@erisian.com.au> het volgende geschreven:
>
> On Thu, Feb 26, 2026 at 05:12:03PM -0500, Matt Corallo wrote:
>> ==Specification==
>> 24 bits from the block header nVersion field, starting from 5 and ending at
>> 28 inclusive (0x1fffffe0), are reserved for nonce use and removed from BIP8
>> and BIP9 specifications. A mask of 0xe000001f should be applied to nVersion
>> bits so bits 5-28 inclusive will be ignored for soft-fork signalling and
>> unknown soft-fork warnings.
>
> This conflicts with the proposed use of bit 5 for signalling CTV activation
> over the next twelve months mentioned at:
>
> * https://groups.google.com/g/bitcoindev/c/HC2bn4QOR-M/m/TF8qJidzAAAJ
> * https://delvingbitcoin.org/t/bip-119-ctv-activation-client/2242
> * https://github.com/ctv-activation/activation-client/blob/06ddbdf01bc8ce181b01c7497010bff74c2b79c6/src/kernel/chainparams.cpp#L121-L127
>
> I don't think there's any meaningful support for that activation proposal,
> but thought it was worth pointing out for completeness.
>
> BIP110 is currently signalling via bit 4 until block 963648; LNHANCE
> is possibly signalling on bit 3 between May last year and Jan 2028.
>
> Previously, CSV signalled on bit 0, segwit on bit 1, segwit reduced
> threshold (bip 91) on bit 4, and taproot on bit 2.
>
> Cheers,
> aj
>
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next prev parent reply other threads:[~2026-04-08 16:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-26 22:12 Matt Corallo
2026-02-27 15:34 ` 'Antoine Poinsot' via Bitcoin Development Mailing List
2026-03-09 19:45 ` 'Antoine Poinsot' via Bitcoin Development Mailing List
2026-03-28 11:58 ` Anthony Towns
2026-04-08 16:16 ` Sjors Provoost [this message]
2026-04-08 20:11 ` 'Antoine Poinsot' via Bitcoin Development Mailing List
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