Stacks (STX): Smart Contracts & DeFi on Bitcoin

Introduction

A token down 91.1% from its high and a product that drew 735 bitcoin (BTC) in its first two bonds, by Stacks Labs' count: both describe Stacks (STX) on 4 November 2026. Stacks is a separate blockchain, anchored to Bitcoin, that was producing blocks on 4 November 2026 (Hiro API, 2026) and runs smart contracts in a language called Clarity. Its Bitcoin-backed token, sBTC, held $193.6M on DefiLlama on 4 November 2026, down from a $614.5M peak. A July 2026 hard fork added Bitcoin Staking, which targets a 3% yield paid in BTC. The sections below explain how Proof of Transfer (PoX), sBTC and the staking bonds work, which decentralized finance (DeFi) apps use them, and where the risks sit. Every figure is dated, the project's own reports are labelled, and no price outlook is given.

What Is Stacks, and How Does It Connect to Bitcoin?

Stacks is a separate blockchain with its own token, STX, that anchors its history to Bitcoin through a mechanism called Proof of Transfer (PoX). Its purpose is to run smart contracts that Bitcoin itself does not execute. STX traded at $0.34 on 4 November 2026, 91.1% below its $3.84 high of 1 April 2024 (CoinPaprika API, 2026).

A separate chain that settles to Bitcoin

Stacks runs its own blocks, its own signers and its own transaction format. Bitcoin nodes do not read Stacks transactions. The link is anchoring: each Stacks miner posts a commitment on the Bitcoin chain, so the Stacks history is tied to Bitcoin's (Stacks Documentation, 2026). Stacks mainnet has anchored to Bitcoin since January 2021 through PoX. The project describes Stacks as a Bitcoin layer. Because the consensus rules are Stacks' own, this article treats it as a separate network that settles against Bitcoin rather than as part of Bitcoin. The beginner's guide to Bitcoin ↗ covers how its own ledger and miners work.

Proof of Transfer pays miners' BTC to stackers

Proof of Transfer lets miners compete with bitcoin instead of electricity ↗. Stacks miners spend BTC, and those who spend competitive amounts have a chance to win the right to mine STX (Stacks Documentation, 2026). The BTC they send goes to stackers: STX holders who lock their tokens for a period and sign blocks. Under the Nakamoto rules stackers are also the block signers, so the BTC is pay for validating blocks (Stacks Documentation, 2026). A reward cycle is a fixed run of 2,100 Bitcoin blocks, and cycle 145 was current on 21 October 2026 (Hiro API, 2026). Stacks Labs reports that PoX has paid out more than 4,000 BTC since January 2021 (Stacks Labs, 2026). PoX-5, covered below, lets bitcoin holders join that reward stream.

STX and its supply

STX is the native token of the Stacks network. It pays transaction fees, and stackers lock it to take part in consensus. Under PoX-5, STX locked at 5% of a bonded bitcoin's value sets a participant's capacity to bond (Stacks Labs, 2026). CoinPaprika lists a market capitalisation of $641.0M and rank 100 (CoinPaprika API, 2026). STX has no hard cap. The Hiro API counted about 1.88 billion STX on 4 November 2026, more than the 1,818,000,000 maximum that CoinPaprika still lists, because SIP-031, active since Bitcoin block 907,740 in July 2025, adds 500M STX for the Stacks Endowment over five years on top of mining rewards. Hiro's own projection puts supply at about 2.32 billion STX in 2050 (SIP-031, 2025; Hiro API, 2026). SIP-045 restored the block reward to the baseline 1,000 STX that applied before April 2026, when an earlier schedule (SIP-029) had halved it to 500 STX; supply mechanics are otherwise unchanged (Stacks Foundation, 2026; SIP-045, 2026).

Proof of Transfer decides who earns BTC; a separate 2024 upgrade decides how quickly and how finally Stacks blocks settle.

How Did the Nakamoto Upgrade Give Stacks Bitcoin Finality?

The Nakamoto upgrade, a hard fork at Bitcoin block 867,867 in late October 2024, changed how Stacks produces blocks. Since then blocks confirm in seconds, and reversing a confirmed Stacks transaction is at least as hard as reversing a Bitcoin one, according to the Stacks documentation (Stacks Documentation, 2026). Both properties come from how miners and signers share the work.

Fast blocks between Bitcoin blocks

Before Nakamoto, one Stacks block appeared per Bitcoin block, so a transaction waited tens of minutes. The upgrade separates block production from the Bitcoin-linked election of miners. A winning miner now produces many blocks during its tenure, the period between two elections, and a transaction confirms in seconds (Stacks Documentation, 2026). Signers, the stackers who validate blocks, must sign each block before the next one can be produced. They also agree on the last signed block before a tenure change, so a new miner cannot orphan confirmed transactions (Stacks Documentation, 2026). The Stacks Foundation put the speed-up at 120 times faster block production at the October 2024 launch (Stacks Foundation, 2025).

Why reversing Stacks means reversing Bitcoin

Stacks no longer forks on its own. A chain reorganisation needs the approval of 70% of stackers, and each miner's Bitcoin transaction commits to the hash of the previous tenure's first block, which ties the Stacks history to Bitcoin (Stacks Documentation, 2026). The documentation calls this Bitcoin finality. The guarantee has a boundary. Bitcoin nodes do not validate Stacks transactions, so the finality comes from signer rules plus the Bitcoin anchor, not from Bitcoin consensus itself. That boundary matters for sBTC, which depends on a separate signer set.

Finality governs when a transaction is safe; the Clarity language governs what a contract is allowed to do.

What Makes the Clarity Smart Contract Language Different?

Clarity is the Stacks smart contract language, designed for predictability over flexibility. Its source is published exactly as written, and every program is guaranteed to halt. Users also cap what a transaction can move. Clarity 6, live since 30 July 2026, adds native checks of Bitcoin transactions (Stacks Documentation, 2026).

Decidable and readable source

A decidable language lets a reader know from the code alone what a program will do. Clarity is intentionally not Turing complete, which allows complete static analysis of a contract's call graph and an exact cost estimate before execution. A Clarity call cannot run out of gas partway through (Stacks Documentation, 2026). The language is also interpreted: contract source is committed to the chain as written, where Solidity is compiled to bytecode that readers cannot check by eye. The type checker removes whole classes of bugs, including reentrancy (Clarity language overview, 2026). The cost is expressiveness, because some programs that run on other chains cannot be written.

Post-conditions guard user assets

Post-conditions are limits a user attaches to a transaction. The protocol aborts the whole transaction if the contract would move more assets than declared, such as 5 STX out of the sender's account (Stacks Documentation, 2026). Wallets including Leather and Xverse display them before signing. Deny mode, the default, rejects any transfer that is not listed. Originator mode, added in Epoch 3.4, caps only what leaves the signer's own account, which suits DeFi calls that route assets through several contracts. The documentation states the limit plainly: post-conditions track who sends an asset and how much, not who ends up owning it, and they do not make a contract safe.

Clarity 6 reads Bitcoin transactions

Epoch 4.0 shipped Clarity 6 on 30 July 2026. Two new functions let a contract read Bitcoin directly: get-bitcoin-tx-output? parses a serialized Bitcoin transaction and returns one output, and verify-merkle-proof checks a transaction against a Bitcoin block's Merkle root (stacks-core 4.0.1 release notes, 2026). The release notes record that the Merkle check rejects the inflated transaction-count forgeries described in CVE-2012-2459. Clarity 6 also adds ed25519-verify, secp256k1-decompress? and two new post-condition types for staking and PoX actions (Stacks Documentation, 2026).

Clarity contracts are only as useful as the assets they can hold, and the main Bitcoin-backed asset on Stacks is sBTC.

How Does sBTC Move Bitcoin Onto Stacks and Back?

sBTC is a token on Stacks that represents bitcoin one to one. BTC goes into a single Bitcoin address controlled by a group of signers, and the same amount of sBTC is minted on Stacks. Its trust assumption is therefore the signer set, not Bitcoin consensus (SIP-028, 2024).

Deposit and withdrawal path

A deposit starts on Bitcoin: the sender creates a transaction with an output that the signers can spend, then submits proof of it on Stacks. The signers sweep that output into the peg wallet and mint sBTC (SIP-028, 2024). A withdrawal starts on Stacks. The holder's sBTC is locked, the signers send BTC to the chosen address, and the locked tokens are burned once the Bitcoin transaction confirms. Deposits are designed to complete within 3 Bitcoin blocks and withdrawals within 6 (Stacks Documentation, 2026). If the signers never act on a deposit, the sender can spend the output back after a fixed number of blocks.

Eleven of fifteen signers hold the peg

The first signer set had 15 institutional members, and 70% of them, 11, had to approve any operation (SIP-028, 2024). The peg wallet is one multisignature Taproot output ↗, spendable by key path only, so no hidden script paths exist (Stacks Documentation, 2026). The design is live while at least 70% of signing power is online and honest, and safe while at least 30% is honest. If more than 30% went offline for good, the BTC in the peg wallet would stay locked, and the original specification names a clawback mechanism as possible but not planned. The signer list is public.

Caps, withdrawals and signer rotation

Deposits opened in December 2024 under a 1,000 BTC cap, which rose to 3,000 BTC on 25 February 2025. Withdrawals went live on 30 April 2025, and the cap rose to 5,000 BTC on 22 May 2025 (Bitcoin L2 Labs, 2025). On 16 September 2025 that 5,000 BTC ceiling was removed, when Nansen counted $545M secured across 7,408 holders (Nansen, 2025). The signer set began a planned rotation in July and August 2026, and Ankr, The Tie and HashKey Cloud joined it in the third quarter (Stacks Labs, 2026). BitGo added institutional custody for sBTC on 25 August 2026. Each rotation changes who holds the keys, so the signer list is worth reading before any large deposit.

Data current as of November 2026.

sBTC covers the Bitcoin that moves onto Stacks; the 2026 Bitcoin Staking product covers Bitcoin that does not move at all.

What Is Bitcoin Staking Under PoX-5, and What Has It Raised?

Bitcoin Staking lets BTC holders lock bitcoin on the Bitcoin chain itself and earn BTC rewards, with STX locked alongside as capacity. PoX-5 made it possible when it activated on 30 July 2026. By the project's own count, the first two bonds drew 735 BTC (Stacks Labs, 2026). Most staking figures below come from Stacks Labs and are project-reported.

PoX-5 and the 30 July fork

PoX-5 activated as Epoch 4.0 at Bitcoin block 960,230 on 30 July 2026, after SIP-044 and SIP-045 passed with more than 99.99% support (Stacks Endowment, 2026). It replaced PoX-4, added protocol bonds and removed the cooldown cycle between staking periods (Stacks Labs, 2026). The fork unlocked all staked STX, so every staker had to restake under the new contract. Stakers restaked 392M STX shortly after the fork, 448M by the end of the third quarter and 493M after the second bond (Stacks Labs, 2026). The Hiro API independently showed 493.4M STX stacked in cycle 146 on 4 November 2026, with 513.0M STX committed for cycle 147, which starts at Bitcoin block 974,750.

How a bond works

A bond has two legs. The BTC is timelocked on Bitcoin under the holder's own keys with a standard timelock script, so it never moves to a bridge or wrapper, and the project says no slashing condition can seize it. STX equal to 5% of the bonded BTC's value is locked on Stacks (Stacks Labs, 2026). A bond lasts six months and pays weekly in BTC. Leaving early forfeits yield not yet distributed, and the paired STX stays locked for the full term. During the bootstrap phase self-custodial bonding is whitelisted by the Stacks Endowment, and other holders use pooled staking on sBTC.

Where the 3% comes from

The BTC that miners commit is the reward pool. Each cycle it pays protocol bonds first, at a target of about 3% a year in BTC. STX stakers receive 85% of what remains, and a reserve fund holds the other 15% so bonds keep paying if mining slows (Stacks Labs, 2026). The Genesis Bond earned 0.28 BTC in its first 14 days on 230 BTC, which is 0.12% and about 3.2% a year when annualised on a simple basis (own computation). The rate is a target set by the Endowment, not a guarantee, and the pool shrinks if miners spend less.

The first two bonds

The Genesis Bond opened on 10 September 2026 at Bitcoin block 966,350 with 230 BTC and 3.57M STX. Bonding Period 2 opened on 8 October 2026 with 505 BTC and 6.7M STX, of which StackingDAO took 483 BTC, or 95.6% (Stacks Labs, 2026). An earlier Stacks post had announced 10 October 2026 for that opening. The two bonds total 735 BTC, about $57.5M at $78,269 a bitcoin on 4 November 2026 (CoinPaprika API, 2026). The 735 BTC equals 29.6% of the 2,482.30 BTC sBTC supply on that day (own computation).

Data current as of November 2026.

The bonded BTC matters to the wider network when it is put to work, and that is the job of the DeFi apps.

Which DeFi Apps Run on Stacks, and How Big Are They?

DeFi on Stacks centres on three apps: StackingDAO issues stBTC, a liquid staking token, Zest lends against it and Bitflow trades it. Daily active users averaged about 1,010 in the third quarter of 2026 (Stacks Labs, 2026). DefiLlama counted $76.2M in StackingDAO and $45.4M in Zest V2 on 4 November 2026 (DefiLlama, 2026).

StackingDAO and stBTC

StackingDAO is the liquid staking app on Stacks. It launched stBTC on 3 September 2026, a token that carries Bitcoin Staking yield, and its first 150 BTC of capacity filled in under 24 hours (Stacks Labs, 2026). stBTC supply has reached 636 BTC, and 97% of it is posted as collateral on Zest, at an estimated yield of 2.3% (Stacks Labs, 2026). That estimate sits below the 3% bond target. DefiLlama shows StackingDAO value locked of $76.2M, down from a $151.6M peak on 7 December 2024 (DefiLlama, 2026). The project says total StackingDAO value locked rose from $31.6M at the end of August 2026 to above $85M, so the recent move starts from a low base. In the Genesis Bond, StackingDAO supplied 65% of the BTC.

Zest lending

Zest is the leading lending market on Stacks. DefiLlama's V2 reading is $45.4M locked with $25.5M borrowed, down from a $88.8M peak on 12 May 2026 (DefiLlama, 2026). The project quotes more: over $80M in value locked, $122M in deposits and $42M in borrows (Stacks Labs, 2026). The gap is method, because $122M less $42M is $80M, so the project's figure is net of borrows. Zest reports more than 1,500 liquidations with zero bad debt. Zest's Bitcoin Collateral Vaults, live since late September 2026, let users borrow against native BTC without leaving self-custody (Stacks Labs, 2026). A Levered Bitcoin Staking Vault, launched on 3 September 2026, loops stBTC to add up to 1.5% extra yield, which also adds leverage.

Bitflow and the rest

Bitflow is the main exchange on Stacks. Its value locked is $2.7M against a $46.3M peak on 30 March 2024, yet weekly DEX volume on Stacks reached a 12-month high of $16.7M in the week of 28 September 2026 (DefiLlama and Stacks Labs, 2026). A subsidy helps: the Stacks Endowment distributes 1 BTC a month through Bitflow and Zest from 10 September to 10 December 2026 (Stacks Labs, 2026). Granite holds $6.7M, down from $27.8M on 17 March 2026, and Hermetica's hBTC vault holds $3.7M (DefiLlama, 2026). Bitflow's concentrated-liquidity pools handled more than $280M in swaps in the third quarter of 2026, according to the project (Stacks Labs, 2026).

Data current as of November 2026.

The sizes are modest, and the history of the two numbers that matter most to investors makes the point sharper.

How Far Have STX and sBTC Fallen From Their Highs?

STX trades 91.1% below its April 2024 high, and sBTC value locked has fallen 68.5% from its August 2025 peak. Both readings are dated below, and both are measured against a peak, which flatters neither the token nor the asset. This article gives no price outlook, and the project's own reports are labelled as such wherever they appear.

STX against its April 2024 high

CoinPaprika showed STX at $0.3409 on 4 November 2026, against a high of $3.84 on 1 April 2024, a market capitalisation of $641.0M and rank 100 (CoinPaprika API, 2026). On 20 October 2026 STX stood at $0.346 and 91.0% below its high, and a gain of about 10% the next day moved the gap by under one point. CryptoBriefing reported a rise of about 50% over the four weeks to 13 October 2026, citing the Stacks report; the token remained about 90% below its high after it. On 4 November 2026 Bitcoin stood at $78,269, 37.9% below its $126,173 high of 6 October 2025 (CoinPaprika API, 2026).

sBTC value locked since August 2025

DefiLlama's series peaked at $614.5M on 14 August 2025 and read $193.6M on 4 November 2026, a fall of 68.5%. It passed $503.9M on 16 September 2025 and $271.1M on 31 March 2026, and its 15 August 2026 reading of $155.0M was the lowest of the sampled readings since February 2025 (DefiLlama, 2026). On-chain supply was 2,482.30 sBTC on 4 November 2026, so value locked tracks both the number of coins and the BTC price (Hiro API, 2026). The project's own count, 2,487 sBTC at the end of the third quarter, is within 0.2% of that reading, and supply has changed little since 30 September 2026. The earlier fall mixes withdrawals and price, and the series alone cannot separate them.

Why two providers disagree

Nansen's $545M is a 16 September 2025 reading, not a 2026 one; the Stacks Q1 2026 snapshot repeated it, and a later release said sBTC closed Q1 2026 at $437M (Nansen, 2025; Chainwire, 2026). DefiLlama read $503.9M and $271.1M on those two dates. The providers count and price the locked bitcoin differently. A check settles which to use: 2,489.57 sBTC at the 21 October price of $84,625 is $210.7M, within 0.3% of DefiLlama's $210.1M on 21 October 2026, so this article uses DefiLlama throughout.

Data current as of November 2026.

Falling numbers are one risk; the structure of the system holds others, and the next dated milestones will test it.

What Are the Risks, and What Does Epoch 4.1 Change?

The risks sit in signers, thin demand and source quality. The next checkpoints are Bond 3, which opened in early November 2026, and Epoch 4.1, which still has no activation height (Hiro API, 2026). Each risk below can be checked against a dated public source.

What can go wrong

The sBTC peg rests on the signer set, and an outage above 30% would lock the peg wallet under the original design (SIP-028, 2024). Bitcoin Staking yield comes from miners' BTC spend, so lower mining bids would shrink the 3% pool. DeFi is thin: Bitflow's value locked is down about 94% from its 30 March 2024 peak of $46.3M to $2.7M (DefiLlama, 2026). Sources lean on the project: the Q3 report is Stacks Labs' own, so figures were checked against DefiLlama and the Hiro API wherever possible. Concentration adds a further risk: StackingDAO took 483 of the 505 BTC in Bonding Period 2, and 97% of stBTC is posted on Zest, so two apps carry much of the new capital (Stacks Labs, 2026). Binance's monitoring tag on STX, explained in the FAQ, is a further market-access risk.

Bond 3 and Epoch 4.1

Stacks runs monthly bonding periods, with capacity growing each time (CryptoBriefing, 2026). Bond 3 opened earlier than the date of around 10 November first pointed to: enrolment was set for 2 to 8 November 2026, with capacity of 1,005 BTC, more than the 735 BTC of the first two bonds combined, at the same 3% target yield paid weekly in BTC (Coinness via Blockchain Seoul, 2026). The Hiro explorer showed about 999.6 BTC enrolled on 4 November 2026, for a term from Bitcoin block 974,750 to 999,950 (Hiro, 2026). Epoch 4.1, the next network upgrade, was targeted for early December 2026. It makes Clarity 7 the default for new contracts, and its activation block height is to be announced 30 days ahead (CryptoBriefing, 2026). On 4 November 2026 the Hiro API still showed no height for Epoch 4.1, so an early-December start would need an announcement within days (Hiro API, 2026). The Stacks roadmap itself says its items are not a schedule with guaranteed release dates (Stacks Roadmap, 2026). The Stacks Endowment says demand currently exceeds available capacity and that capacity will grow cautiously, bond over bond (Stacks Endowment, 2026). Q4 is the first full quarter of monthly bonds, which gives the clearest read yet on how much Bitcoin the staking layer attracts.

FAQ

?Is Stacks a Bitcoin layer 2, a sidechain or its own blockchain?

Stacks has its own blocks, token and consensus rules, and it anchors to Bitcoin through Proof of Transfer, so it is its own blockchain. The project calls it a Bitcoin layer. Bitcoin nodes do not validate Stacks transactions, and the sBTC peg relies on a signer set rather than Bitcoin validation. Whether that earns the label layer 2 depends on the definition used.

?What happens to the BTC behind sBTC if too many signers go offline?

Any sBTC operation needs approval from 70% of signers. Under Stacks Improvement Proposal (SIP) 028, if more than 30% go offline, no deposit or withdrawal is approved until enough return. If more than 30% were lost permanently, the BTC in the peg wallet would stay locked under the original specification, which calls a clawback possible but not planned. A depositor can reclaim an unprocessed deposit after a fixed number of Bitcoin blocks.

?How long do sBTC deposits and withdrawals take?

Deposits are designed to complete within 3 Bitcoin blocks and withdrawals within 6. At Bitcoin's average block time of about 10 minutes, that is roughly 30 minutes and 60 minutes. The signer set approves each operation, so delays are possible if signers are slow or offline, and the stated block counts are design targets rather than guarantees.

?Can a small holder join Bitcoin Staking, or is it institutions only?

Self-custodial bonds are whitelisted through the Stacks Endowment during the bootstrap phase, and the project invites institutions and holders with 50 BTC or more to contact the team. Other holders can use pooled staking on sBTC through providers including Xverse, Fast Pool and StackingDAO, which needs no whitelist. Capacity is limited: an Xverse pool filled in Bonding Period 2, and the Endowment said in October 2026 that demand exceeds capacity.

?Did STX holders have to do anything when PoX-5 activated?

Yes. PoX-5 unlocked all staked STX, so every staker had to restake under the new contract. STX locked under the old PoX-4 contract became spendable with no unlock transaction, and tokens that were not restaked stopped earning. Stakers restaked 392M STX shortly after the 30 July 2026 fork, and 493.4M STX was stacked in cycle 146 on 4 November 2026.

?Why did Binance put a monitoring tag on STX?

The Stacks Endowment says Binance applies the tag to protocols that change emissions more than once in 18 months. SIP-031 added emissions from July 2025, the SIP-029 schedule halved the block reward in April 2026, and SIP-045 restored the 1,000 STX reward with the July 2026 fork. The Endowment says that change left total supply unchanged. The Endowment says removal follows a standard compliance review. The explanation comes from the Endowment, not from Binance.

?How is Stacks different from the Lightning Network?

Lightning is a payment network of channels ↗ opened on Bitcoin, built to move bitcoin quickly between channel partners. Stacks is a separate blockchain with its own token, STX, built to run smart contracts such as lending and trading apps. BTC enters those apps as sBTC or as a bond, not through Lightning channels.

References / Sources