Subject: Re: [bitcoindev] [BIP Proposal] Limit ScriptPubkey Size >= 520 Bytes Consensus.

From: Andrew Poelstra <[email-masked]>
Date: Thu, 2 Oct 2025 22:19:43 +0000

On Thu, Oct 02, 2025 at 01:42:06PM -0700, PortlandHODL wrote:
> Proposing: Softfork to after (n) block height; the creation of outpoints 
> with greater than 520 bytes in the ScriptPubkey would be consensus invalid. 
>

Personally, I like this. Unlike restrictions on opcode behavior or
witness data, it is impossible for there to be any existing UTXOs which
"might turn out to need" scriptpubkeys greater than 520 bytes. In a
post-covenant world I suppose this could change.

There is a risk of confiscation of coins which have pre-signed but
unpublished transactions spending them to new outputs with large
scriptPubKeys. Due to long-standing standardness rules, and the presence
of P2SH (and now P2WSH) for well over a decade, I'm skeptical that any
such transactions exist.

In any case, if confiscation is a worry, as always we can exempt the
current UTXO set from the rule -- if you are only spending outputs that
existed prior to the new rule, your new UTXOs are allowed to be large.

I would even suggest going lower than 520 bytes.

-- 
Andrew Poelstra
Director, Blockstream Research
Email: apoelstra at wpsoftware.net
Web:   https://www.wpsoftware.net/andrew

The sun is always shining in space
    -Justin Lewis-Webster

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