Stacks (STX) Bitcoin Bonds: How BTC Earns While Staying in Self-Custody

Key Takeaways

• Stacks’ Bitcoin bond lets holders earn yield paid in BTC, with a 3% target annual yield per bond, while their Bitcoin stays on the Layer 1 (L1), in their own custody. The yield comes from BTC that miners spend to mine Stacks blocks, not from lending out participants' coins.

• Every bonded Bitcoin requires STX worth 5% of its value to be held and locked for the six-month term, making STX the staking capacity for Bitcoin. The first two bonds brought in about 735 BTC, and Bonding Period 2 alone locked 6.7 million STX.

• Two upgrades planned for 2027 are designed to deepen demand for STX capacity, alongside STX’s longer-term role as the gateway to Bitcoin capital markets. Neither upgrade is live yet.

This article is brought to you by Stacks. 

Most Bitcoin does nothing. It sits in cold storage, ETPs and corporate treasuries, holding value but earning nothing. Until now, making it productive has usually meant handing it to someone else: a lender, an exchange or a yield platform. That trade-off between yield and custody is exactly what the 2022 lender collapses exposed.

Stacks offers a different route. Through its Bitcoin bond, holders lock BTC on the Bitcoin Layer 1 (L1), maintain custody of their coins, and earn yield paid in BTC. The bond is the first building block of what Stacks calls Bitcoin Capital Markets: markets where Bitcoin earns, collateralizes and trades while staying secured by Bitcoin finality.

This article covers what that gives a Bitcoin holder, how the bond works, and why STX sits at the center of it as the staking capacity every bonded Bitcoin requires.

What Bitcoin Capital Markets Give a BTC Holder

Holders of stocks and bonds take three things for granted: their assets can earn, they can be borrowed against, and they can be traded. For Bitcoin, each of these has typically required leaving the Bitcoin network or giving up custody. Stacks is built to deliver all three while the underlying security stays with Bitcoin.

• Earn: Bond BTC for a fixed term and earn yield paid in BTC. The Bitcoin stays on the L1, in the holder's custody, for the life of the bond.

• Collateralize (planned for 2027): A planned self-custodial lending product would let bonded BTC back a stablecoin loan while it keeps earning yield. The existing Stacks ecosystem already has hundreds of BTC deployed in lending through protocols such as Zest Protocol.

• Trade: Bitcoin-based assets trade on Stacks DeFi venues such as Bitflow, the network's main DEX, alongside products like Hermetica's Bitcoin-backed, yield-bearing synthetic dollar.

Activity on Stacks settles with Bitcoin finality, so it inherits the security of the Bitcoin network rather than relying on a separate chain's guarantees.

Institutions now hold Bitcoin as a form of capital through ETPs, corporate treasuries and custodians, and many want to put it to work without handing custody to a lender or platform. The Stacks bond lets them earn BTC yield while their Bitcoin stays on the L1.

How the Bitcoin Bond Works

A Bitcoin bond lets a participant commit BTC for a fixed term and earn BTC in return, without moving that BTC off the Bitcoin L1. In practice, it works in four steps:

1. Bond BTC. The participant bonds Bitcoin for a six-month term. The BTC stays on the Bitcoin L1, in the holder's custody.

2. Pair it with STX. Each bond requires STX as staking capacity, currently worth 5% of the BTC value bonded. That STX stays locked until the bond matures.

3. Earn BTC. Participants earn rewards paid in native BTC. Each bond has a 3% target annual yield, set before the bond opens and fixed for its term. The next section explains where that BTC comes from.

4. Mature and repeat. At the end of the term, the bond matures and the STX unlocks, with new bonding periods open roughly every month.

The first bond, the Genesis Bond, sold out in September 2026. Its first participants were 21Shares, HashKey Cloud, UTXO Management (the asset management arm of public Bitcoin treasury company Nakamoto Inc) and Sypher Capital. At quarter-end, it had 230 BTC bonded.

Bonding Period 2 widened participation through liquid Bitcoin staking and added 505 BTC, bringing the combined total to about 735 BTC.

The current phase, PoX-5, is a deliberate bootstrap with a whitelist of anchor participants. The end-state design, PoX-6, is planned for 2027 as an open auction (covered below). According to Stacks, no other product currently offers BTC-denominated yield for self-custodial Bitcoin staking.

Where the BTC Yield Comes From

The yield is paid by Stacks miners. It does not come from lending out participants' Bitcoin, and it is not paid in a newly issued token.

The source is Stacks' consensus mechanism, Proof of Transfer (PoX). It works like this:

1. Miners bid BTC. To win the right to produce a Stacks block, miners commit BTC in a transaction on the Bitcoin network. The more BTC a miner commits, the better its chance of winning the block.

2. The winning miner earns STX. The miner that produces the block receives the Stacks block reward, paid in STX, plus transaction fees.

3. The BTC goes to participants. The BTC that miners commit is not burned or kept by Stacks. It is transferred to the network's participants, which today means those who bond BTC and lock STX capacity.

In effect, miners pay BTC to receive STX from economic activity, and that BTC flows to bond participants. Proof of Transfer has distributed 4,224 BTC this way since the network launched in January 2021.

For a Bitcoin holder, this means:

• The yield comes from outside your position. Your BTC is not lent, rehypothecated or moved off the L1 to generate it. The BTC you earn is spent by miners competing for Stacks blocks.

• Each bond has a 3% target annual yield, set before the bond opens and fixed for its term.

STX: The Staking Capacity for Bitcoin

The asset being staked in a Stacks bond is Bitcoin. STX is the capacity that unlocks it. To bond BTC and earn BTC yield, a participant must hold and lock STX worth a set share of the bonded BTC, currently 5%, for the full bond term.

That makes STX a capacity asset, a different category of token design. Most token demand comes from inside a protocol's own economy: fees, governance or rewards paid in the same token. Here, demand comes from outside: from Bitcoin holders who want to earn yield. Every Bitcoin that enters a bond creates proportional demand for STX that must be held and locked.

The amount of STX a bond requires depends on three values based on the below formula:

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

Because the capacity ratio is set in value terms, the number of STX needed moves with both prices. If BTC rises relative to STX, each bonded Bitcoin requires more STX. If STX rises relative to BTC, it requires fewer.

Institutional STX locked as capacity is taken off the market for the bond’s six-month term and can’t be sold or traded until the bond matures.

What the First Two Bonds Show

The first two bonds show the mechanism working. Bonded BTC more than doubled from 230 BTC in the Genesis Bond to 505 BTC in Bonding Period 2. Bonding Period 2 alone required 6.7 million STX to be locked alongside its 505 BTC.

Across the network, staked STX rose from 392 million after the PoX-5 hard fork to 493 million after Bonding Period 2, an increase of about 26%.

Bonds run for six months, and new bonding periods open monthly. Each new bond adds a fresh cohort of locked STX, on top of earlier cohorts that have not matured yet. Bonds 3 and 4 will each be 1,000 BTC, about double the size of Bonding Period 2. The table below shows how locked STX would build up if every new bond were that size.

Illustrative only. Assumes monthly bonds of 1,000 BTC each at Bonding Period 2 prices (about 13,300 STX per BTC) and a six-month term.

With six overlapping cohorts, about 79.8 million STX would be locked at any given time, around 16% of the 493 million STX currently staked, and larger bonds would raise that level further. Taking that much STX off the market could also support its value, which would make STX block rewards more valuable to miners, incentivizing them to spend more BTC to win those blocks. Because each bond’s 3% target annual yield is set in advance, more BTC from miners means more Bitcoin can be bonded at that target, so each bond helps create room for a larger one.

How Bonds Compare to Token Buybacks

The closest familiar comparison is a token buyback. Both create a demand sink that takes tokens out of circulation, but they are funded and sustained very differently.

Locked STX is not removed for good: each cohort unlocks when its bond matures. The demand holds up only if new bonds keep replacing maturing ones, which is why the overlapping monthly cohorts above are central to the model. In exchange, the sink is funded by external Bitcoin rather than by the protocol spending its own resources, and it grows with every bond.

What 10,000 Bonded BTC Would Mean for STX

At Bonding Period 2 prices, 10,000 bonded BTC would require about 133 million STX to be held and locked, roughly 27% of the 493 million STX currently staked.

The calibration point is Bonding Period 2 itself: 6.7 million STX for 505 BTC, or roughly 13,300 STX per bonded Bitcoin. Applying that rate to larger bond sizes gives the following:

Illustrative only, at Bonding Period 2 prices. Because the capacity ratio is set in value terms, the STX amounts move with both the BTC and STX prices.

For perspective, 10,000 BTC is a small slice of the Bitcoin held by ETPs and corporate treasuries today. The table is illustrative rather than a forecast, but it shows that STX demand scales directly with the amount of Bitcoin that chooses to earn yield through Stacks.

The Roadmap: Three Levers for STX Demand? 

Two upgrades planned for 2027 are designed to deepen demand for STX capacity. Neither is live yet.

Lever 1: An open auction for capacity (planned, PoX-6). Today, capacity goes to a whitelist of anchor participants. Under PoX-6, STX bids would determine how much BTC each participant can bond. Allocation would shift from whitelisted capacity to competitive bidding for a limited supply, turning STX capacity into a market in its own right.

Lever 2: Self-custodial borrowing (planned). A planned lending product would let bonded BTC, still earning yield, back a stablecoin loan. This mirrors the bond-and-repo pairing in traditional finance, where a bond earns its coupon while also serving as collateral for borrowing. For a Bitcoin holder, the same BTC would be productive twice: earning BTC yield and unlocking liquidity, all without leaving self-custody.

Greater capital efficiency makes bonding more attractive, more bonding raises demand for STX capacity, and an open auction lets that demand compete for a limited supply. Together, they would turn a single yield product into a capital market.

Lever 3: STX as the gateway to Bitcoin capital markets (long term). Beyond the two 2027 upgrades, STX’s longer-term role is as the entry point to the markets that form on Stacks. Staking BTC requires STX capacity, every transaction on Stacks pays its fees in STX, and borrowing against staked BTC is planned to build on that same staked position. Those fees go to the miners who produce Stacks blocks, so more activity on Stacks raises how much BTC miners are willing to commit, which flows back to staked BTC and can support more capacity for Bitcoin to come in and earn. For institutions and individual holders alike, that makes STX the gateway holding they need to deploy BTC into whichever yield, credit and trading markets develop on Stacks over time. As those markets grow, so does the role of the asset that gives access to them.

Conclusion: The First Primitive of Bitcoin Capital Markets

For Bitcoin holders, the Stacks bond answers a long-standing trade-off: BTC can now earn BTC yield while staying on the L1, in the holder's own custody. With planned lending and an active Stacks DeFi ecosystem, the same Bitcoin can also be collateralized and traded, all settled with Bitcoin finality.

The bond is the first primitive of these Bitcoin Capital Markets, and STX is the asset that unlocks access to them. Every Bitcoin that bonds requires STX to be held and locked. The first two bonds have already brought in about 735 BTC from participants including 21Shares and HashKey Cloud. If more of the Bitcoin sitting idle in treasuries and ETPs follows, demand for that capacity grows with it.

This article is for informational purposes only and is not financial advice.