Without OP_CAT, Bruce Liu says Bitcoin is as “useful as a jumbo jet without wings” capable of much more than it’s allowed to do, but stuck on the ground while Ethereum and Solana soar.
Liu, the founder of OPCAT_Labs, says a single opcode, OP_CAT, could transform Bitcoin from static digital gold into programmable money that rivals other Layer-1 chains.
OP_CAT is a long-disabled opcode in Bitcoin’s code that, if re-enabled, would allow developers to concatenate data in scripts and unlock a range of new possibilities, from vaults and covenants to decentralized exchanges and zero-knowledge proofs.
The Bitcoin blockchain, if OP_CAT was re-enabled, would be as programmable as Ethereum or Solana, said Liu.
“OP_CAT is not new code. It was never deleted, just commented out and disabled. We are not adding my opcode or somebody else’s. It’s Satoshi’s,” Liu told CoinDesk during an interview on the sidelines of BTC Asia in Hong Kong.
But the push for OP_CAT doesn’t come without friction.
Satoshi disabled it in 2010 over concerns it could enable denial-of-service attacks. Opponents argue that any new opcode introduces “unknown unknowns,” threatening Bitcoin’s hard-won stability. Others take a philosophical stance: Bitcoin should remain digital gold, rather than chasing Ethereum’s programmability.
Liu pushes back by appealing to Satoshi Nakamoto’s design.
“If Bitcoin was only for payments, why did Satoshi include Script at all?” he asked. “OP_CAT isn’t my invention, it’s Satoshi’s code. It was never deleted, only disabled.”
Liu says OP_CAT would bring Script to life – the basic programming language built into the Bitcoin blockchain – allowing Bitcoin to do more than just payments and enabling features like vaults or even basic DeFi.
OP_CAT, he said, would unlock more of that potential, letting developers build things like vaults, covenants, or even simple DeFi apps on Bitcoin.
To reinforce the point, he points back to Nakamoto’s own explanation of why Script existed in the first place.
In a 2010 Bitcointalk post, Nakamoto wrote that Bitcoin’s design was effectively “set in stone” from its first release, so he wanted it to accommodate every type of transaction he could imagine.
Hard-coding each one would have created endless special cases, Satoshi explained, so instead the Bitcoin creator introduced Script as a general solution that let users define their own conditions while nodes only needed to check if those conditions were met.
Already, the company launched a fork of Bitcoin in a virtual machine with OP_CAT enabled to demonstrate its potential, complete with SDKs, APIs and a JavaScript-like programming language designed to make building on Bitcoin accessible to Web2 developers.
The OP_CAT Lobby
The other half of Liu’s plan is political. Alongside Mate Tokay, an early Bitcoin entrepreneur, who co-founded Bitcoin.com with Roger Ver, OPCAT_Labs is spearheading what they describe as an “Alliance” of OP_CAT supporters.
The goal is to coordinate otherwise scattered efforts from groups like Taproot Wizards, StarkWare, and independent developers.
“Previously, OP_CAT advocacy was leaderless,” Liu said. “Ninety percent of people we speak with are in favor, but the loudest voices are the ones against. We want to organize support into something visible, semi-official, and coordinated.”
Tokay frames it as an education campaign for influential stakeholders, fund managers, institutions, and even lawmakers, who he says are too focused on BTC treasuries to notice the programmability debate.
“If they knew what OP_CAT unlocks, they’d be even more excited about Bitcoin’s future,” he said.
By next year’s Bitcoin Asia conference, Liu hopes to show working DeFi apps on Bitcoin and progress toward an organized lobbying front.
He frames it as unlocking potential that’s been there all along. “We’re not changing Bitcoin,” he said. “We’re unfolding its wings.”
