Safest Bitcoin Bridges for Native BTC: Custody and Trust Models

Every bridge in this guide calls itself non-custodial. That label doesn't tell you everything. What matters is where your BTC sits while the swap settles, who controls that address, and what happens if something goes wrong.

We went through the documentation for seven protocols that accept native BTC and mapped out each one's custody and trust model. None of them holds your BTC in a company-controlled account, but each one asks you to trust a different set of parties.

Looking for the bigger picture on quotes and chain coverage? Start with our guide to the best Bitcoin bridges for native BTC.

Key takeaways

• None of the seven protocols holds your BTC in a company account, but each relies on a different set of parties.
• BOB Gateway gives each order its own Bitcoin deposit address. Once your BTC confirms, a solver delivers your output in a single atomic transaction, or your BTC is refunded.
• Garden Finance settles through hash time-locked contracts (HTLCs) on both chains, so you can reclaim your funds yourself if a swap stalls.
• THORChain and Chainflip hold swap liquidity in shared vaults secured by threshold signatures across node operators or validators.
• tBTC holds deposits under Threshold's 51-of-100 signer model and mints a BTC-backed token for DeFi.

Contents

1. Which Bitcoin bridge is safest for native BTC?
2. What does "non-custodial" mean for a Bitcoin bridge?
3. Where does your BTC go?
4. Is BOB Gateway non-custodial?
5. How does Garden Finance's HTLC model work?
6. How do THORChain and Chainflip's threshold vaults work?
7. How do solver and MPC-based bridges work?
8. Is tBTC a Bitcoin bridge?
9. Which Bitcoin bridges are trust-minimized?
10. Have any of these protocols had security incidents?
11. What should you check before bridging BTC?
12. Which Bitcoin bridge should you choose for security?
13. Frequently asked questions
14. Move native BTC with BOB Gateway

Which Bitcoin bridge is safest for native BTC?

It depends on which failure you're most worried about. There's no single ranking.

• If you want a refund you can trigger yourself when a counterparty disappears, Garden Finance's HTLC design gives you that by construction.
• If you don't want your BTC entering a shared vault, BOB Gateway gives each order its own deposit address and one solver, with an automatic refund if the swap can't complete.
• If you're comfortable with a distributed validator set holding liquidity, THORChain and Chainflip both use threshold-signature vaults that no single operator controls.

Table 1. The strongest option for each safety priority.

What does "non-custodial" mean for a Bitcoin bridge?

"Non-custodial" tells you that no single company holds your BTC in an account it controls. It doesn't tell you whether your BTC passes through a validator set, a solver, a relayer or a timelocked contract, and each of those could potentially fail in different ways. A protocol can avoid a central custodian and still depend on a threshold of signers, a solver's willingness to fill, or a relayer staying online.

A more useful question is: can anyone block, delay or wrongly settle your transaction, and what happens if they do? That's how we compare each protocol below.

Where does your BTC go?

Every protocol here sends your BTC somewhere other than your own wallet before you receive the destination asset. What differs is who controls that address and what has to happen before funds move again.

Table 2. Custody and settlement design for each protocol, from each protocol's documentation as of 16 September 2026.

Sources: BOB Gateway, Garden Finance, THORChain, Chainflip, NEAR Chain Signatures, Relay

Is BOB Gateway non-custodial?

Yes. Gateway is non-custodial. It doesn't hold your BTC in a company account, and it doesn't lock your BTC in a bridge contract and issue a token against it. A BTC-to-token Gateway swap works like this (Gateway docs):

1. You request a quote. Gateway returns a signed quote with routing, fees and your guaranteed minimum output.
2. You create an order and get a unique Bitcoin deposit address for it.
3. You sign one Bitcoin transaction to that address.
4. Once the deposit is confirmed, the solver delivers your output in a single atomic transaction. If it can't, your BTC is refunded.
5. The asset arrives on the destination chain.

What you rely on is narrower than "trust nobody". You need a solver willing to fill at the quoted rate, and if it can't, your order is refunded. For swaps back to BTC, your funds sit in escrow until BOB's Bitcoin light client verifies the solver's BTC payment, so a delay can't release your funds.

If a swap can't settle at the quoted terms, the solver re-quotes and retries for about an hour, then refunds the order to the refund address on your order (Gateway FAQ).

BOB Gateway has been audited by Pashov and Common Prefix. See the audit list.

How does Garden Finance's HTLC model work?

Garden settles each swap through HTLCs on both chains. When a solver accepts your order, both sides lock funds under the same condition: revealing a secret unlocks both legs at once. If the secret is never revealed, either side can reclaim its own funds once the timelock expires, without the other side's help. That gives Garden a useful property: if a solver stops responding, you can trigger the refund yourself instead of waiting on a third party. Garden also states that it can't freeze users' assets (garden.finance). It's a different approach from Gateway's solver-locks-first model, and it protects against a different type of failure.

How do THORChain and Chainflip's threshold vaults work?

Both hold liquidity in vaults that no single operator controls. Non-custodial means something different here: your BTC enters a shared vault that holds every user's liquidity on that chain, rather than a contract tied to your transaction alone.

THORChain. Each vault's key is split across the nodes in a shard using a threshold signature scheme (TSS). No single node holds the full key, and moving funds out requires a supermajority of that shard's nodes to sign (TSS and vault docs). Shards default to 20 nodes, and membership rotates through a regular churn. Node operators must bond more than 1.5 times the value of the vault they help secure. THORChain's May 2026 incident report identifies its TSS implementation as GG20 (exploit report).

Chainflip. Vaults are secured by an Authority Set of up to 150 validators, with 100 of 150 required to sign under the FROST threshold scheme (protocol overview).

Table 3. How THORChain and Chainflip secure their vaults, from each protocol's documentation as of 16 September 2026. Neither is custodial in the exchange-account sense, and neither is a single-transaction escrow.

How do solver and MPC-based bridges work?

NEAR Intents and Relay both use solver networks, but your BTC passes through different infrastructure before a solver fills your order.

NEAR Intents takes BTC through bridge infrastructure like the Omni Bridge or PoA Bridge, or through NEAR's Chain Signatures, an MPC network made up of eight nodes (Chain Signatures docs). A Verifier contract on NEAR finalizes settlement once a solver fills your intent.

Relay has three main parts: a Depository that holds user deposits on each origin chain, a Hub on Relay Chain that tracks solver balances, and an Allocator that generates the MPC withdrawal payloads solvers use to get reimbursed (architecture docs). A solver fills your order on the destination chain with its own capital. An Oracle confirms the deposit and the fill, and only then can the solver withdraw from the Depository.

In both designs, your BTC sits under MPC or bridge-operator control until the solver's fill is verified. Neither protocol publishes a fixed Bitcoin confirmation count for native BTC deposits.

Is tBTC a Bitcoin bridge?

tBTC solves a different problem. Depositing BTC doesn't get you a destination asset of your choice. It mints tBTC, a 1:1 BTC-backed token secured by Threshold's 51-of-100 signer model, which you can later redeem for BTC.

That makes tBTC a fit if you want BTC exposure inside Ethereum DeFi, not if you want BTC turned into a stablecoin or ETH in one step. A minority of signers can't move funds on their own, but it's still one shared signer set holding every depositor's BTC.

Which Bitcoin bridges are trust-minimized?

Trust-minimized isn't the same as self-custody. Self-custody means you control your funds at every point, and no cross-chain swap can offer that during settlement, because your BTC has to leave your wallet on one chain before or as you receive an asset on another.

What varies is how many parties you rely on and what each one could do if it misbehaved.

Table 4. Fewer parties and narrower failure modes generally mean a more trust-minimized design. It's a spectrum, not a yes or no.

Gateway and Garden both limit trust to one solver per order. That's a different exposure from a vault where the same operator set secures every user's funds at once.

Have any of these protocols had security incidents?

Five protocols covered here or in our main bridge guide disclosed security incidents in 2026: THORChain, Garden Finance, Chainflip and Relay from this guide, and Symbiosis, which appears in our main bridge guide. A past incident doesn't prove a design is unsound today, but it belongs in any honest comparison.

THORChain. On 15 May 2026, node operators spotted unauthorized outbound transactions from one vault, and trading was halted. THORChain's report puts the loss at about $10.7 million, revised up from an early estimate, and attributes it to a flaw in its GG20 TSS implementation that leaked key material over time (exploit report). Trading resumed on 23 June 2026.

Garden Finance. On 26 July 2026, Garden took its app offline after an attacker compromised an independent solver's off-chain database and drained about $450,000 in solver-owned funds, as reported by the security firm Blockaid (crypto.news). Garden said its contracts and user funds weren't affected, and it was returning quotes normally by 14 September 2026.

Symbiosis. On 11 September 2026, Symbiosis disclosed that an attacker had exploited its Bitcoin Bridge, and it paused the bridge while its other routes kept running. It says it recovered about 15 BTC into a team-controlled multisig. As of 13 September 2026, the Bitcoin Bridge was still paused, with BTC swaps running through partner routes (The Block).

Chainflip. On 12 September 2026, an attacker took 736,442 USDT from Chainflip's Tron vault in six unauthorized payouts. Chainflip's incident report says the attacker attached their own memo to a Tron transaction its validators had already signed. The protocol then treated it as a separate swap and paid the same deposit out twice. Chainflip says all other funds were unaffected, and it paused the network while it investigated (incident report). It restarted the Tron route on 17 September 2026 with new accounting for liquidity providers, and it has committed to making affected users whole (Phemex).

Relay. On 29 September 2026, Relay disclosed that its API had exposed pending orders before they executed. MEV bots used this to front-run trades between 12 and 26 September, so about 5,600 users received worse prices. Bots made about $136,000, and the median user lost about $12. No funds were taken from Relay's contracts. Relay is compensating affected users with about $312,000 and paid a $50,000 bounty to Outputlayer, the security team that reported it (ChainCatcher).

What should you check before bridging BTC?

Ask the same five questions of any protocol: where does your BTC go, who controls that address, what verifies settlement, what happens if the other side goes quiet, and what do you receive at the end?

A protocol that does well on one question can still fall short on another. Garden's self-triggered refund is a strong safeguard, but you still depend on a solver being willing to fill in the first place. THORChain and Chainflip remove that single-solver dependency, but your funds sit in a shared vault with everyone else's.

Which Bitcoin bridge should you choose for security?

Match the protocol to the risk you care about most.

Table 5. Which protocol fits which security priority.

Move native BTC with BOB Gateway

Every protocol here keeps your BTC out of a company account, but they don't all ask you to trust the same things. With BOB Gateway, each order gets its own deposit address, the solver delivers in a single atomic transaction or refunds your BTC, and nothing sits in a shared vault.

Security models change over time, so check each protocol's current docs before you move a large amount.

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