Want to move your assets between TON and Ethereum (or BNB Chain, or Base, or Polygon)? STON.fi cross-chain swap execution will soon be able to do that. The engine doing the heavy lifting is called Omniston, STON.fi’s cross-chain execution layer, and the whole thing runs on smart contracts.
By the end of this guide, you’ll know what’s happening when you click “swap,” you’ll have walked through three real-world scenarios where cross-chain matters, and you’ll have a short checklist to run before you confirm anything.
First, what does “cross-chain” mean?
Cross-chain means moving value between two blockchains that have no native way to talk to each other. Some piece of software has to coordinate them, because neither chain can read the other’s ledger on its own.
Think of each blockchain as its own city with its own ledger. TON has one, Ethereum has another. They don’t naturally exchange information, so if you want to move value from one to the other, something has to coordinate the handoff.
The old-school approach was traditional bridges: lock your asset in a big shared pot on one side, mint a wrapped IOU version on the other. The problem with that design is the pot itself, because pooling large amounts of value in one contract has historically made bridges a recurring target for exploits.
STON.fi takes a different route. There’s no shared pot and no wrapped token, just smart contract logic that coordinates two chains directly.
A quick note before going further: if both assets you’re working with already live on TON, you don’t need any of this. A regular same-chain swap on STON.fi is faster and simpler. Cross-chain only makes sense when your destination asset lives somewhere else, like on an EVM-compatible chain. (“EVM” just means the chain runs Ethereum’s Virtual Machine, so it speaks the same contract language. Ethereum, BNB Chain, Base, and Polygon are all in that family.)
What happens during a swap
A cross-chain swap on STON.fi locks your source asset on one chain and links it to a matching locked asset on the destination chain, so both sides release together or both refund together. Here’s how that works under the hood.
When you start a cross-chain swap, your source asset gets locked inside something called a Hashed Timelock Contract, or HTLC for short, on the TON side. At the same time, a counterparty in the Omniston network, called a resolver, locks the matching destination asset inside its own HTLC on the EVM chain.
Both contracts share the same cryptographic lock, called a hashlock. When that lock opens, you claim your destination asset and the resolver claims your source asset. If the lock doesn’t open within the time window, everything goes back to where it came from automatically, with no support ticket required.
This is the part worth tattooing somewhere: every cross-chain swap on STON.fi is all-or-nothing. Either both sides receive exactly what was quoted, or no funds move at all. There’s no middle state where your money is stuck in limbo.
One thing to keep in mind: how long the EVM side takes to settle depends on that chain’s block times, not TON’s.
The quick-reference rundown
Before going deeper, here are the practical facts worth knowing upfront:
- Nobody holds your funds at any point in the swap; the smart contracts handle custody.
- The TON-side fee shows up in the app preview before you confirm, and any unused TON gas comes back to you.
- If a swap fails, funds return to the sender automatically.
- EVM-side fees are whatever the destination chain charges; TON has no say in that.
- No KYC is required at any stage; connecting a wallet is enough to proceed.
- Speed varies by destination, since TON itself settles quickly while EVM chains take however long their own blocks take.
What happens between clicking “swap” and seeing it confirm
The full path runs from a quote being fetched in the background, through both HTLCs locking on their respective chains, to the cryptographic secret being revealed so both sides can claim. Here’s how that sequence plays out in detail.
1. Before any transaction actually broadcasts, the interface is already busy behind the scenes. The moment you pick your source and destination assets, the app pings multiple liquidity sources through Omniston to fetch a competitive quote from connected resolvers. You set your slippage tolerance, you see the estimated gas fee, and all of this is visible before you commit to anything.
2. Once you confirm, the HTLC on TON locks your source asset, and the protocol coordinates with a resolver who locks the destination asset in a matching HTLC on the EVM chain.
- Here’s a small thing that trips people up: TON processes contract actions across several blocks rather than all at once. So if you see a “pending” status sitting there for a bit, that’s expected behavior, not an error.
- Two safety nets are running underneath all of this. The first is TON itself, because if a message can’t reach its target contract for some reason, TON’s built-in bounce mechanism sends the locked asset back to whoever sent it.
- The second is the HTLC timelock: if the cryptographic secret that unlocks the swap doesn’t get revealed in time, say because the destination side never finished its lock, the source funds become refundable to the sender. Either way, refunds happen on their own.
3. On the EVM side, once both HTLCs are locked and the secret is revealed, the destination asset releases to your wallet address. The resolver then uses that same secret to claim the source-side asset on TON, and the interface confirms the swap once both chains have recorded the change.
Three scenarios where this matters in real life
The mechanics get clearer with examples. Below are three situations where cross-chain swaps actually come up, each one showing a slightly different angle of how the system handles things.
- Scenario one: USDT on BNB Chain to a TON-native jetton. Say you’re holding USDT on BNB Chain and you want exposure to a token that lives natively on TON. (A “jetton” is just TON’s version of a standard token, similar to how ERC-20 works on Ethereum, and wallets and DEXes on TON recognize jettons automatically.) Through STON.fi, your USDT locks in an HTLC on BNB Chain, and a resolver, which is a professional liquidity provider in the Omniston network, locks the equivalent jetton in a matching HTLC on TON. Both sides use the same cryptographic lock. When it opens, you get the jetton, the resolver gets the USDT, and no wrapped token is minted along the way.
- Scenario two: Toncoin-equivalent value over to Ethereum. Maybe you want to use a protocol that only lives on Ethereum. The usual path would be sending to a centralized exchange, paying deposit fees, doing the KYC, swapping, withdrawing, paying withdrawal fees, then waiting. STON.fi skips that whole detour. The same HTLC-and-resolver flow handles it, your destination wallet on Ethereum receives the asset once the EVM-side contract confirms, and no account registration is needed at any stage.
- Scenario three: the one that didn’t go through. This is the scenario worth reading carefully, because it’s the one most guides gloss over. Say the EVM-side contract can’t complete the swap, maybe because the destination address had a formatting problem, or because gas prices on the EVM chain spiked past what you’d set at confirmation. The HTLC timelock handles it automatically: once the time window expires, the locked asset on the TON side comes back to your wallet. The Omniston interface also tells you exactly what happened, using explicit status labels of fully filled, partially filled, or aborted, so you always know where you stand.
How this stacks up against bridges and centralized exchanges
The practical differences come down to three things: who holds the money, what the fees look like, and what happens when something breaks. The table below summarizes how each approach handles those three.
| STON.fi cross-chain | Traditional bridge | Centralized exchange | |
| Custody | Non-custodial throughout; STON.fi never holds or can access user funds | Bridge contract holds assets during transit; pooled value in one place has historically attracted exploits | Exchange holds funds throughout; you depend on the platform’s solvency |
| Source-chain fees | TON gas paid in TON, shown before you confirm; unused amounts refunded | Varies; Ethereum bridges can hit $1–$10+ during congestion | Trading fees plus withdrawal fees, depending on the platform |
| If it fails | Automatic return to sender via HTLC timelock, with no support queue | Varies; some bridges require manual recovery | Depends on the exchange’s support response time |
| KYC | No | No | Usually yes |
| Best for | Moving assets between TON and EVM networks, or between EVM networks (Ethereum, Base, BNB Chain, Polygon) | General EVM-to-EVM moves where a dedicated bridge is already in use | Users whose assets are already sitting on a centralized exchange |
One detail: the source-chain fee doesn’t decide the destination-chain fee. EVM-side gas comes from whatever the destination chain charges, and Ethereum, BNB Chain, Base, and Polygon all set their own prices, which move with congestion.
Five things to check before you confirm
A short pre-swap checklist can prevent the most common cross-chain mistakes, most of which come from address format errors and slippage settings. Here are the five worth running through every time.
Address format errors are probably the most avoidable mistake in cross-chain, and they still happen constantly. EVM addresses start with 0x, while TON addresses look completely different. Pasting one format into the other field will either fail outright or route incorrectly, so confirming the destination network and address format should come before anything else.
Then:
- Slippage tolerance. Set it too tight for a volatile asset and the swap may reject; for stablecoins, you can usually set it lower.
- Token verification. If you don’t recognize the token, check that its contract link shows a green verified badge, which confirms it matches a known, audited deployment.
- TON balance. Keep at least 0.3–0.4 TON in your source wallet before starting. The STON.fi SDK uses a default of 0.3 TON for swap-related calls, and a wallet running near zero can stall the transaction.
- The “You will receive” field. Glance at it one more time before final confirmation. If the number looks lower than expected, revisit your slippage or wait for a fresh quote.
Final thoughts
STON.fi cross-chain execution model launching soon moves assets between TON and EVM networks using smart contract logic, which means predictable fees, automatic failure handling, and no custodian anywhere in the flow. Cross-chain is the right tool when your destination asset lives on a different network. When both assets already live on TON, a same-chain swap is the simpler call.
STON.fi is the interface, and Omniston is the execution layer underneath. Because of how that execution layer is built, every cross-chain swap either completes exactly as quoted or returns every locked asset in full.
