Stacks Bitcoin Bonds Let Holders Earn BTC While Keeping Coins in Self-Custody

Stacks’ Bitcoin bond puts two assets at the center of a new yield model: holders keep their Bitcoin on Bitcoin’s Layer 1, while STX supplies the capacity required to participate. Each six-month bond targets a 3% annual yield paid in BTC. The BTC reward comes from miners competing to produce Stacks blocks, rather than from lending participants’ coins.

That structure makes the bond a useful test of whether Bitcoin can support financial products without asking holders to transfer custody to a lender or platform. It also gives STX a specific role: Bitcoin bond participants must lock STX worth 5% of their bonded BTC’s value for the full term.

A yield stream tied to Stacks mining

The rewards originate in Proof of Transfer, Stacks’ consensus mechanism. Miners commit BTC through Bitcoin transactions to compete for the right to produce a Stacks block. The winning miner receives STX block rewards and transaction fees; the BTC committed by miners is distributed to network participants. Today, that means holders who bond BTC and lock the required STX.

For bondholders, the distinction is material. Their Bitcoin isn’t lent out, rehypothecated or moved off Bitcoin Layer 1 to generate the reward. Instead, miners spend BTC as part of their competition for Stacks blocks, and that BTC flows to participants. Proof of Transfer has distributed 4,224 BTC since Stacks launched in January 2021.

The yield target for each bond is set before it opens and stays fixed for its term. That 3% annual target describes the bond’s stated terms; it doesn’t change the source of rewards, which is miner BTC committed to the network.

How participants bond BTC

A participant commits BTC for six months while retaining custody of the coins on Bitcoin Layer 1. To take part, the holder also locks STX worth 5% of the BTC position’s value. The STX remains locked until the bond matures, when it becomes available again. New bonding periods open roughly monthly.

The amount of STX required depends on the BTC amount, the capacity ratio and the relative prices of BTC and STX:

STX required = BTC bonded × capacity ratio × (BTC price ÷ STX price).

Because the 5% requirement is measured by value, the number of STX needed can shift as either asset’s price changes. A rise in BTC relative to STX raises the STX amount required per bonded bitcoin; a rise in STX relative to BTC lowers it.

The first bond, called the Genesis Bond, sold out in September 2026 and had 230 BTC bonded at quarter-end. Its initial participants included 21Shares, HashKey Cloud, UTXO Management—the asset management arm of public Bitcoin treasury company Nakamoto Inc.—and Sypher Capital. Bonding Period 2 added 505 BTC, bringing the combined amount to about 735 BTC. It also involved liquid Bitcoin staking.

The current phase, PoX-5, is a bootstrap with a whitelist of anchor participants. The planned PoX-6 phase, scheduled for 2027, is expected to replace that approach with an open auction.

Why STX demand follows Bitcoin participation

STX functions as capacity for Bitcoin bonds. Every new BTC position requires a corresponding amount of STX to be held and locked, creating demand tied to outside Bitcoin capital rather than solely to activity within the Stacks token economy. The locked STX is unavailable to sell or trade during the six-month bond term, then unlocks at maturity.

Bonding Period 2 required 6.7 million STX for 505 BTC. Across the network, staked STX increased from 392 million after the PoX-5 hard fork to 493 million after that bonding period, a rise of about 26%.

Bond 3 and Bond 4 are each planned at 1,000 BTC, roughly twice the size of Bonding Period 2. At the earlier period’s approximate rate of 13,300 STX per BTC, a 1,000 BTC bond would lock about 13.3 million STX. If monthly bonds of that size continued, six overlapping cohorts would hold about 79.8 million STX at once. That estimate assumes Bonding Period 2 prices and a six-month term.

The mechanism resembles a token buyback in that it temporarily reduces the amount of STX available to trade. Its funding source and duration differ: a buyback draws on protocol treasury or revenue, while bond capacity is demanded by BTC holders and each STX cohort returns to circulation at maturity. Sustained demand therefore depends on new bonds replacing maturing ones.

Scale depends on prices and bond volume

At Bonding Period 2 prices, 10,000 bonded BTC would require about 133 million STX—roughly 27% of the 493 million STX then staked. The same price assumptions imply approximately 9.8 million STX for the first two bonds’ combined 735 BTC, 13.3 million for 1,000 BTC, and 66.5 million for 5,000 BTC.

These figures are illustrations, not forecasts. The number of STX needed changes with BTC and STX prices, while actual demand depends on how much Bitcoin holders choose to bond. The scale comparison shows the model’s direct link: more BTC entering bonds means more STX capacity must be locked under the current terms.

There is a possible feedback loop in the design. More STX locked as capacity could support STX’s value, making block rewards more valuable to miners and potentially encouraging them to commit more BTC. More miner BTC could then support additional bonds at their preset yield target. That chain depends on market behavior and participation; it isn’t guaranteed by the bonding formula.

Planned changes could widen access and utility

Two upgrades planned for 2027 could change how capacity is allocated and how bondholders use their BTC. Neither is live yet.

Under PoX-6, Stacks plans to move from whitelisted allocations to an open auction in which STX bids determine how much BTC each participant can bond. That would make access to capacity competitive, with a limited amount allocated through bidding.

A separate planned lending product would let bonded BTC back a stablecoin loan while continuing to earn BTC yield. The concept combines a bond position with borrowing against it, allowing a holder to retain the yield-producing position while accessing liquidity. Stacks already has BTC deployed in lending through protocols including Zest Protocol, but the proposed product for bonded BTC remains a future development.

Bitcoin-based assets also trade on Stacks DeFi venues such as Bitflow, the network’s main decentralized exchange. The ecosystem includes products such as Hermetica’s Bitcoin-backed, yield-bearing synthetic dollar. Stacks activity settles with Bitcoin finality, linking these applications to Bitcoin’s security model.

STX’s role beyond the bond

The bond gives STX a concrete capacity function, while its broader role could extend across Bitcoin lending and trading on Stacks. Bonding BTC requires STX; transactions on the network pay fees in STX; and the planned borrowing product would build on the same bonded position. Fees go to miners producing Stacks blocks, connecting network activity with the BTC miners commit.

For now, the clearest evidence is operational: the first two bonding periods attracted about 735 BTC, and Bonding Period 2 locked 6.7 million STX. Whether the model grows will depend on continued participation, the capacity available in future periods, and delivery of the planned auction and lending features. If those pieces take hold, the bond could become an entry point for Bitcoin holders seeking yield while keeping custody on Bitcoin Layer 1.