October 6, 2025
SIP-033 Update: Clarity 4 Is On The Way
Hey Stackers, we’re here with an update on an incredible SIP that’s been working it’s way down the pipe: SIP-033. This SIP brings us the next version of Clarity containing five new built-in functions all bundled in what we're calling Clarity 4. These are improvements that builders and core developers have been working toward together over the past few months — it’s now time to finalize the Governance aspects so that these new features can hit mainnet as soon as possible. As these changes are consensus breaking, the community will be asked to participate in an open vote as per the usual SIP approval process.
The SIP draft is now ‘finalized,’ though the authors welcome additional commentary and feedback. The Technical CAB has convened and is working to cast their vote by Monday, October 6th. Based on the technical nature of this SIP, they are the only CAB required to cast a vote, but as always, the authors are happy to hear from members of other CABs. In general, the draft has been well circulated among these community leaders already and includes clear support from key builders listed below.
The SIP draft is now ‘finalized,’ though the authors welcome additional commentary and feedback. The Technical CAB has convened and is working to cast their vote by Monday, October 6th. Based on the technical nature of this SIP, they are the only CAB required to cast a vote, but as always, the authors are happy to hear from members of other CABs. In general, the draft has been well circulated among these community leaders already and includes clear support from key builders listed below.
What Clarity 4 Brings to Builders:
Information taken directly from this detailed forum post.
This enables on-chain contract code validation, for example allowing contract A to validate that contract B follows a specific template and is therefore safe to interact with. This is especially useful for enabling bridges and marketplaces to safely and trustlessly support a dynamic set of assets.
These allow a contract to safely call arbitrary external contracts (e.g. passed in as traits) while ensuring that if the executed code moves assets beyond those specified, the changes will be rolled back.
This function will enable developers to easily convert values like bool s and principal s into their ASCII string representations, facilitating the generation of string-based messages for interacting with cross-chain protocols.
This keyword will allow developers to easily access the timestamp of the block currently being processed, enabling time-based logic and features in their smart contracts. This is especially important for DeFi applications.
SIP-033 introduces secp256r1-recover?and secp256r1-verify functions in Clarity 4, enabling on-chain verification of secp256r1 signatures. This provides the cryptographic foundation developers need to build passkey-based authentication, potentially enabling features like hardware-secured wallets and biometric transaction signing.
Anticipated Timeline (+/- 7 days):
- Now: Upgrade being tested for release (testing and auditing will continue through 10/30).
- October 6th: Technical CAB Approval expected
- October 10th: Open session with Brice, the lead author and core developer from Stacks Labs (details will be added to the main Stacks calendar shortly)
- October 16th: Open community vote kicks off
- October 30th: Open community vote closes
- November 6th: Projected hard fork date
Reminder on SIP Approval Thresholds
To activate this SIP, the following voting conditions must be met:
- At least 80 million stacked STX must vote (quorum)
- At least 80% of all stacked STX must be in favor of the proposal (approval)
- At least 80% of all unstacked STX must be in favor of the proposal (approval)
Community Support
The upcoming Clarity 4 release brings several functions and improvements that directly respond to builder needs across the Stacks ecosystem.
For the ALEX team, new functions like contract-hash? and restrict-assets? are especially important. These are foundational for advancing work on Dynamic Automated Market Makers (DAMM), a core element of ALEX’s 2025 roadmap. By tightening asset control and giving contracts more flexible checks, these functions make it easier to design safer and more sophisticated trading mechanisms.
Several other Clarity 4 additions came directly from developer feedback:
For the ALEX team, new functions like contract-hash? and restrict-assets? are especially important. These are foundational for advancing work on Dynamic Automated Market Makers (DAMM), a core element of ALEX’s 2025 roadmap. By tightening asset control and giving contracts more flexible checks, these functions make it easier to design safer and more sophisticated trading mechanisms.
Several other Clarity 4 additions came directly from developer feedback:
- to-ascii (link) was originally requested by a Wormhole contributor and makes string conversions simpler and reduces overhead for cross-chain integrations. It’s a small change that clears away unnecessary complexity.
- block-time (link) was requested by the Zest team to compute yield accrual based on real time rather than block counts, which is crucial for accurate DeFi lending and yield products.
- secp256r1 support adds a new curve that enables smart wallets based on modern passkeys. This opens the door for wallet experiences that look more like web2 logins (simple, secure, and familiar) while remaining trustless and on-chain.
Builder Perspectives
To show how these new features impact real-world projects, here’s what ecosystem teams are saying about Clarity 4:
“Clarity 4 provides a native way to verify smart contracts on-chain. It allows builders to add mechanisms to trust third-party contracts. It will be a great step towards better protocol interoperability.” -- Marvin, Co-founder at Ryder
“SIP-033 is a game-changer for security and UX. On-chain contract allowlists and in-contract post-conditions let me build trustless bridges and marketplaces hardened against proxy attacks, adding another security layer on top of off-chain verification. Plus, native passkey support means wallets without seed phrases that spin up in 3 seconds with Face ID—smooth onboarding with true self-custody.” -- Rafa, Senior Engineering Manager at Hiro and Core Stacks Contributor
“The main reason we need Clarity 4 is the new function that returns a contract’s code body hash. This will let us add safety measures like on-chain pool verification. It’s one of the last features we’re waiting on for HODLMM. There will also be new functions that allow a contract to set post-conditions, which we can use to better protect assets.” -- Bought, Lead Smart Contract Engineer at Bitflow
“[Clarity 4] allows for ‘verified pools’ on-chain via code-body-of, which ensures the pool contract’s code is an exact match of the standard template. Without it, we’d need a wrapper service to keep up with pools at launch. With Clarity 4, core contracts know immediately whether a pool is verified or not. Unverified pools can still launch, but users will know they may be malicious.” -- Dylan Floyd, CEO at Bitflow
As the voting window approaches, detailed information will be provided on how to cast your vote.