Bitcoin’s trillion-dollar asset base has always sat at the edge of decentralized finance, too large to ignore and too technically constrained to use. On July 22, 2026, the Sui Foundation took the most architecturally specific run at that problem yet: it launched the Hashi testnet, a protocol that lets Bitcoin serve as programmable DeFi collateral while the underlying BTC never leaves the Bitcoin network. More than 25 institutional partners — including BitGo, Cumberland, an OCC-chartered bank called Erebor, and SEC-registered investment adviser Wave Digital Assets — are already stress-testing lending and credit applications ahead of a mainnet release that has no announced date.
The testnet matters because the two dominant solutions to this problem — wrapping Bitcoin into tokens like WBTC, or bridging it to another chain — have both proven to be sources of persistent institutional risk. Cross-chain bridges and cross-chain messaging protocols have caused billions of dollars in losses from hacks and exploits, according to Immunefi data. Wrapped Bitcoin carries counterparty exposure to its custodian — an exposure that sharpened in August 2024 when BitGo transferred WBTC custody to a partner linked to crypto figure Justin Sun, raising governance questions that have not fully dissipated. Hashi proposes a third path: threshold cryptography that grants Sui-based smart contracts verifiable control over Bitcoin UTXOs without physically moving the BTC.
The tax barrier has historically compounded the security barrier. Moving BTC into a wrapped format — or bridging it to another chain — has been analyzed as a potential taxable exchange under IRS property-treatment rules, a friction point that institutional treasury and compliance departments have cited as a barrier. Attorneys at Fenwick, an AmLaw 100 firm ranked 69th on the 2025 list and widely recognized in digital assets, published an analysis on the Sui Foundation’s blog in April 2026 concluding that locking BTC through Hashi and receiving hBTC should not constitute a taxable event under U.S. federal income tax law. Hashi addresses both barriers in this testnet cycle.
How Hashi Keeps Bitcoin on Bitcoin
The technical mechanism is not a bridge. When a user deposits BTC into Hashi, the funds go to a unique 2-of-2 multisig Bitcoin address generated for that Sui account. Neither party to that multisig — the Hashi validator committee nor the Guardian Layer’s enclave — can move the BTC alone. Both signatures are required for every withdrawal.
Under the hood, Sui validators running Hashi monitor the Bitcoin network. After a quorum confirms the deposit, they mint an equivalent amount of hBTC — a fungible token — on Sui. That hBTC is what moves through Sui’s DeFi ecosystem: protocols like Suilend, AlphaLend, and Fluid can accept it as collateral, set loan-to-value ratios, link to price oracles from CF Benchmarks, and issue stablecoin liquidity against it. When the borrower repays, the Hashi validators generate a threshold Schnorr signature via multi-party computation (MPC), the Guardian Layer provides the second signature, and the 2-of-2 Bitcoin transaction releases the UTXOs back to any Bitcoin address the user specifies.
MPC here means something specific. Rather than a single private key controlling the BTC — which creates a single point of failure — Hashi distributes key material across the Sui validator committee using a protocol where no individual validator ever holds the complete signing key. The system is secure as long as fewer than 33 to 50 percent of staking power is colluding, and remains live as long as fewer than 20 to 33 percent of staking power is unresponsive. These parameters may be tightened in future versions.
The distinction from WBTC’s mint-and-burn model: WBTC requires a custodian to hold the native BTC and a merchant layer to handle compliance. The user’s BTC moves to BitGo’s custody. Hashi’s BTC never leaves the Bitcoin blockchain; it stays locked in a multisig UTXO controlled by cryptographic threshold logic rather than a corporate custodian.
What the Guardian Layer Actually Does
The biggest technical disclosure in Tuesday’s testnet announcement was the Guardian Layer — a separate security mechanism Hashi revealed publicly for the first time alongside the testnet launch.
The Guardian Layer is a withdrawal co-signer implemented as a cloud hardware enclave, separate from the MPC validator committee. It enforces configurable limits, monitoring large withdrawals or abnormal thresholds and either slowing or blocking them before BTC can leave the system. Independent key provisioners hold encrypted shares of the guardian’s Bitcoin key. All operations produce immutable logs stored outside the enclave.
The architectural purpose is defense-in-depth against the most dangerous failure mode in multi-validator systems: collusion. If the MPC committee threshold were somehow exceeded — meaning more validators colluded than the security parameters allow — the Guardian Layer would still need to be independently compromised before any BTC could be stolen. The two security mechanisms are designed to be independent; compromising one does not compromise the other.
For DeFi generally, this addresses a structural weakness in smart-contract execution. Once a smart contract is deployed, it typically executes automatically with no override. Hashi’s architecture introduces a configurable human-in-the-loop checkpoint for large-value events — a design concession to institutional risk management that pure DeFi protocols have historically rejected, and that institutional treasury managers have historically required.
Clearing the Tax Barrier
Institutional adoption of Bitcoin DeFi has historically faced two separate walls: security and tax. Hashi addressed both in this testnet cycle.
Attorneys at Fenwick, a law firm ranked 69th on the 2025 AmLaw 100 and widely recognized in digital assets, published an analysis on the Sui Foundation’s blog in April 2026 concluding that locking BTC through Hashi and receiving hBTC should not constitute a taxable event under U.S. federal income tax law. The reasoning turns on a specific structural distinction: hBTC is a receipt token confirming ownership of the underlying Bitcoin, not a distinct asset created through an exchange. No disposition of BTC occurs under Fenwick’s reading of existing U.S. tax principles.
This matters because moving BTC into a wrapped format — or bridging it to another chain — has been analyzed as a potential taxable exchange under IRS property-treatment rules, a friction point that institutional treasury and compliance departments have cited as a barrier. The Fenwick analysis is not a binding IRS ruling, and Hashi explicitly recommends that individuals consult their own tax advisors. What a formal opinion from an AmLaw 100 firm does accomplish is giving compliance departments documented analysis to evaluate rather than a void.
How Hashi Fits a Crowded BTCfi Market
Hashi is not operating in a vacuum. The Bitcoin-in-DeFi-without-wrapping space has attracted multiple serious entrants in the past year alone, and understanding where Hashi fits requires acknowledging them.
Babylon Protocol, which partnered with Aave in December 2025 to enable native Bitcoin collateral through trustless vaults on Ethereum, takes a Bitcoin-native approach that does not require a separate L1 like Sui. Zest Protocol launched Bitcoin Collateral Vaults in May 2026, extending lending directly to Bitcoin L1 using pre-signed transactions. tBTC uses decentralized bonded node operators to secure BTC without a single custodian.
Hashi’s differentiation argument rests on three specific claims. First, Sui’s parallel execution engine — capable of high throughput at low fees — enables faster collateral processing and liquidation logic than Ethereum-based approaches. Second, the Guardian Layer adds a second independent security backstop that pure MPC systems do not have. Third, the institutional coalition — including an OCC-chartered bank and an SEC-registered investment adviser — means Hashi launches with compliance and regulatory infrastructure already embedded, rather than needing to be built after the fact.
Whether those differentiators prove sufficient is precisely what the testnet phase is designed to determine. The protocol’s partners include formal-verification auditors Certora and OtterSec, whose work on the smart contracts will be a prerequisite to mainnet. As CryptoTimes observed the day of the testnet launch, Hashi will need to demonstrate that its security model, operational processes, and partner integrations perform as intended before the protocol can achieve broader adoption.
Who Is Building on Hashi Testnet
The 25-plus testnet partners span the institutional stack. On custody and wallet infrastructure: BitGo, Blockdaemon, Cobo, Fordefi (by Paxos), Ledger, SwissBorg, and Cubist, which provides cross-chain collateral infrastructure. On liquidity: Bullish, Cumberland, Erebor (OCC bank), and FalconX. On DeFi protocols building the lending and borrowing interfaces: AlphaLend, Bluefin, Current, Fluid, Navi, Scallop, and Suilend.
Wave Digital Assets stands out in the asset management tier. The SEC-registered investment adviser has committed to three years of best efforts to prioritize the tokenization of Bitcoin-yield-bearing bond products on Sui using Hashi as the underlying collateral layer, according to the Sui Foundation’s testnet announcement. That three-year time horizon signals conviction about the space, not merely testnet curiosity.
CF Benchmarks is providing oracle pricing, Soter Insure is offering Bitcoin-denominated institutional insurance against covered custody failures, and Asymptotic, Certora, and OtterSec are running smart-contract security and formal verification audits.
Institutional BTC lenders speaking at Consensus 2026 in Miami made clear what institutional borrowers need from any Bitcoin DeFi system: transparency about where collateral is stored, explicit no-rehypothecation guarantees, and identifiable counterparties. Hashi’s on-chain visibility into collateral health and its architecture — which keeps BTC in verifiable UTXOs rather than pooled custody — directly addresses the first two requirements. The third — identifiable counterparties — is addressed through the institutional partner structure and the Guardian Layer’s logging and audit trail.
What Testnet Means — and What Comes Next
Developers, custodians, and financial institutions can begin building on Hashi today. The SDK documentation, integration guide, and technical resources are available at sui.io/hashi. The testnet phase is explicitly a stress-testing period, not a product launch: partners are validating integrations and operational workflows before real capital enters the system.
The Sui Foundation has not announced a mainnet date. What the testnet launch establishes is that the ecosystem buildout — custody, liquidity, DeFi applications, insurance, and security auditing — is functional enough to begin testing under coordinated institutional conditions. The timeline to mainnet will be determined by the quality of that testing.
The broader stakes are real. Less than 0.5 percent of Bitcoin’s market cap is currently deployed in DeFi, according to Sui’s public communications. Total outstanding crypto-collateralized loans reached $73.6 billion by Q3 2025, an all-time high, according to research from Spark. If Hashi’s architecture survives institutional scrutiny through the testnet phase, it would represent one of the more credible infrastructure bets on where that ratio goes next.
Frequently Asked Questions
What is the difference between Hashi’s hBTC and Wrapped Bitcoin (WBTC)?
When you deposit BTC into Hashi, your Bitcoin stays on the Bitcoin blockchain in a 2-of-2 multisig address that neither Hashi validators nor any single party can spend alone. The hBTC you receive on Sui is a receipt confirming your ownership — not a new asset. WBTC works differently: a custodian (BitGo) physically holds your BTC, and an equivalent ERC-20 token is minted on Ethereum. This introduces custodian counterparty risk, peg risk, and regulatory exposure to the custodian that Hashi’s architecture is specifically designed to eliminate. According to attorneys at Fenwick, this structural distinction is also the basis for the conclusion that Hashi deposits and redemptions should not trigger U.S. taxable events, unlike some wrapped-token transactions.
Is depositing Bitcoin in Hashi a taxable event in the United States?
Attorneys at Fenwick, an AmLaw 100 firm recognized for digital asset expertise, analyzed Hashi’s mechanics and concluded that depositing BTC and receiving hBTC, and later redeeming hBTC for BTC, should not constitute taxable events under current U.S. federal income tax principles. The analysis rests on hBTC’s classification as a receipt token representing continued Bitcoin ownership rather than a separate property. This is not a binding IRS ruling, and Hashi recommends consulting a personal tax advisor. The conclusion contrasts with some bridging and wrapping arrangements, where the transfer of BTC to a custodian in exchange for a distinct token has been analyzed as a potential taxable exchange.
What happens to my Bitcoin if Hashi validators collude or the system is hacked?
The Guardian Layer is specifically designed for this scenario. All BTC collateral is secured by a 2-of-2 multisig requiring both an MPC signature from the Hashi validator committee and a separate signature from the Guardian Layer’s hardware enclave, as described in the Hashi technical documentation. The two signers are architecturally independent: compromising the validator committee does not automatically compromise the Guardian. The Guardian enforces configurable limits and can block suspicious large withdrawals before they execute. Independent key provisioners hold encrypted shares of the guardian’s Bitcoin key, and all operations produce immutable external logs. That said, Hashi is still in testnet — no mainnet capital has been deployed — and the security model has not yet been stress-tested under adversarial conditions at scale. The formal verification audits by Certora and OtterSec are part of what the testnet phase is designed to complete.
How does Hashi compare to other native-Bitcoin DeFi protocols like Babylon?
Babylon Protocol, which partnered with Aave in December 2025 to enable native BTC collateral through trustless vaults, takes a Bitcoin-native approach that does not require a separate layer-1 blockchain. Zest Protocol launched Bitcoin Collateral Vaults in May 2026 on Bitcoin L1 using pre-signed transactions. Hashi’s approach routes BTC activity through Sui, which claims advantages in throughput, fee efficiency, and parallel execution for collateral management. Hashi also adds the Guardian Layer as a distinct secondary security mechanism and has assembled a compliance-anchored institutional ecosystem — including an OCC-chartered bank and an SEC-registered investment adviser — that differentiates its institutional positioning. Whether the tradeoff of routing through Sui’s validator set is worth those advantages is a question the testnet phase is designed to help answer.