A grassroots movement is gaining traction around two bitcoin improvement proposals (BIP) as candidates for Bitcoin’s next soft fork, specifically BIPs 119 and 348.
BIPs serve as the formal avenue for discussing proposed modifications to Bitcoin. In theory, if a BIP accrues enough support, it can be integrated into Bitcoin through a soft fork or a routine update to Bitcoin Core. These proposals are often referred to by informal names, and a single soft fork can encompass multiple BIPs. BIP 119 introduces OP_CHECKTEMPLATEVERIFY (CTV), while BIP 348 presents OP_CHECKSIGFROMSTACK (CSFS).
Bitcoin’s technical community usually engages in thorough debates regarding these BIPs. The Taproot Wizards—a group of Bitcoin developers known particularly for their Bitcoin NFTs—created an informative graphic to clarify the complex and often circular nature of these discussions.
Essentially, the process for a Bitcoin soft fork necessitates an approximate gauge of support from the various stakeholders in Bitcoin, including developers, custodians, investors, and miners. The optimal indicator of this support remains Bitcoin miners, who demonstrate their backing for code changes by signaling modifications within their mined blocks. Typically, Bitcoin Core requires 95% of blocks over a designated timeframe to signal their support before finalizing the update for activation.
Nonetheless, there is no concrete guideline to define what constitutes “widespread support,” and consensus within the Bitcoin community is an ongoing, evolving concept. Miners provide a measurable means of signaling change, given their countable status within the Bitcoin network, making it challenging to achieve real-world consensus due to Bitcoin’s decentralized nature.
Throughout February and March, we have observed a clear shift as a number of developers explicitly voiced their support for these two BIPs.
What Do the Proposals Entail?
Over the past few weeks, various Western Bitcoin developers have expressed their backing for CTV and CSFS via Twitter, signaling a cohesive stance in favor of select changes to Bitcoin.
CTV and CSFS provide new methods for scripting within Bitcoin. Bitcoin script functions as the lower-level programming language for Bitcoin, utilized for tasks such as creating and sending transactions. Proposed by former Bitcoin core contributor Jeremy Rubin, CTV has existed for more than five years, while CSFS was formalized more recently in November 2024 by Rubin and Brandon Black.
These two BIPs would facilitate “covenants” on Bitcoin, which simply limit how a wallet can spend Bitcoin in future transactions. Covenants are generally expected to greatly enhance self-custody, fee management, and improve existing Bitcoin technologies such as Lightning, Ark, and contract-based applications.
Moreover, developers view these proposals as “narrowly defined,” meaning that if activated, the likelihood of them being exploited for unintended purposes is minimal. The Bitcoin developer community is usually very cautious about any modifications to Bitcoin. For instance, although BIP 119 has been stable for almost five years, there was a time not long ago when CTV was deemed too aggressive for activation.
A Long Journey Ahead
You might recall the strong resistance Rubin faced during his earlier campaign for CTV—from high-profile Bitcoin advocates such as Adam Back and Jimmy Song. The critiques generated considerable opposition within the Bitcoin community, ultimately leading Rubin to withdraw from Bitcoin development altogether.
So, what has changed? Recent support for the OP_CAT opcode (BIP 347) seems to have expanded the Overton Window regarding acceptable Bitcoin proposals, positioning CTV & CSFS as comparatively “conservative” alternatives. It’s worth noting that many supporters of OP_CAT are also in favor of BIPs 119 and 348 (and a majority of proposals in general).
What lies ahead? More discussion is expected. Developers are set to convene at several technical conferences, including OPNEXT in April, BTC++ in July, and TABConf in October. As developers start to build a rough consensus, the soft fork’s actual activation will depend on miners, the community, and investors.
However, there is no standardized procedure for executing a “soft fork” on Bitcoin, leaving many questions unanswered. Will a potential soft fork encompass only CTV and CSFS? Will OP_CAT—frequently part of this opcode suite—join the discussion? How will an actual soft fork activation transpire? And will other stakeholders, especially Bitcoin miners, pay attention?
One thing is certain: brace yourself for an abundance of abbreviations.