The Stacks community approved SIP-045, the Bitcoin Staking upgrade, with more than 99% of votes cast in favor, Stacks co-creator Muneeb Ali said, setting up a hard fork targeted for around July 29 at roughly Bitcoin block 907,740.
The upgrade, formally "PoX-5: Bitcoin Staking and Emission Schedule Alignment," lets participants lock BTC in a timelocked contract on Bitcoin's base layer — under their own keys — and pair it with locked STX to earn yield paid in bitcoin. A companion proposal, SIP-044, which brings Clarity 6 and new staking post-conditions, passed alongside it. Voting opened July 6; hard-fork votes require at least 80% approval from stacked STX.
"Bitcoin is the world's most trusted asset precisely because of its design and safety principles on the L1," Ali said when the Bitcoin Staking whitepaper was published in May. "Holders can now earn yield denominated in BTC, trustlessly, while their Bitcoin stays exactly where it belongs."
How the Mechanism Works
Stakers fund a timelocked UTXO on Bitcoin using OP_CHECKLOCKTIMEVERIFY, pair it with an STX lock equal to at least 5% of the bond, and commit for roughly six months. The Stacks contract verifies the Bitcoin-side lock with an SPV proof — no custodian or trusted bridge. Yield comes from the BTC that miners already bid through Proof of Transfer: paired bonds get a target of about 3% APY in BTC, STX-only stackers take 85% of the excess, and 15% builds a reserve that buffers shortfalls. There is no slashing; principal returns in full when the timelock expires.
The bootstrap phase caps capacity at 3,000 BTC, managed by the Stacks Endowment with whitelisted partners and about 10% open to pools. A public testnet went live this week, and a "Genesis Bond" is targeted for late August.
SIP-045 also reverses April's emissions cut, restoring the STX coinbase to 1,000 STX per Bitcoin block from 500 — a meaningful supply increase bundled with the staking mechanism.
Yield Without Leaving Bitcoin
Stacks has distributed more than 4,200 BTC — roughly $500 million — in stacking rewards since Proof of Transfer went live in 2021, and its sBTC bridged asset holds about $186 million, per DefiLlama, down from a Q1 peak of $545 million as BTC's price fell.
The vote result did nothing for the token. STX trades at $0.144, down 13% in 24 hours, per CoinGecko, sharply underperforming Bitcoin's 1.9% decline.