OneKey USDT0 to USDC Swap on Arbitrum: Gas Error, Sponsored Fee and What I Actually Received
Tested: October 29–30, 2026 | Real funds | OneKey App + Hyperliquid
I started with 445 USDT0 on Arbitrum and wanted to convert it into USDC before using Hyperliquid.
My first route through CoW Swap failed because the approval step required ETH for gas. I then switched to Binance Web3, where OneKey showed a “Send Free” option during the transaction flow.
The swap eventually completed through Binance Web3, and I ended up with 444.3212 USDC in my OneKey wallet.
This is what actually happened — including the gas error, the sponsored fee option, the final amount I received, and how I then connected OneKey to Hyperliquid.
Note: OneKey labels the token as “USDT” in parts of the swap interface. The asset I used on Arbitrum was USDT0.
Quick Results
| Item | What happened |
|---|---|
| Starting amount | 445 USDT0 |
| Network | Arbitrum |
| Target asset | USDC |
| First route | CoW Swap |
| First problem | Insufficient ETH during approval |
| Successful route | Binance Web3 |
| Sponsored fee | “Send Free” appeared during the Binance Web3 flow |
| Final balance | 444.3212 USDC |
| Hyperliquid connection | WalletConnect |
| Hyperliquid deposit | 10 USDC tested |
The important distinction is that a swap quote, a sponsored network fee, and the amount you finally receive are not the same thing.
1. My Test Setup
I used OneKey as my self-custody wallet to prepare funds for a small Hyperliquid test.
I already held 445 USDT0 on Arbitrum. Since I wanted USDC for Hyperliquid, I opened OneKey’s swap interface and compared the available routes.
One useful feature was being able to see different providers and estimated outputs inside the wallet.
But the route with the best-looking quote was not the route I eventually used.
2. Comparing USDT0 to USDC Swap Quotes
One of the first CoW Swap quotes showed approximately 444.5097 USDC for my 445 USDT0.
My OneKey app was set to Korean during this test. All screenshots below are original, unedited records of my transactions.
I opened the order review screen to continue.
At this point, 444.5097 USDC was only an estimated output. The swap had not been completed.
That distinction became important almost immediately.
3. Why Did My OneKey Swap Fail With an Insufficient ETH Error?
The CoW Swap route failed during the approval step.
OneKey showed that I did not have enough ETH on Arbitrum to complete the required transaction.
Error message:
“Insufficient ETH balance. Keep at least 0.00000261 ETH to cover the network fee.”
This happened even though I had enough USDT0 for the swap itself.
The reason is that a token swap can involve a separate on-chain token approval. In my case, that approval required ETH for gas.
So the problem was not that I lacked USDT0.
I lacked enough of the network’s native gas token to complete that particular approval flow.
Rather than adding ETH immediately, I went back and compared another route.
4. What Does “OneKey Sponsored” or “Send Free” Mean?
OneKey showed several available providers, including Binance Web3.
The Binance Web3 route showed an estimated output of approximately 444.4128 USDC.
I selected that route.
During the Binance Web3 flow, OneKey displayed a “Send Free” option on the confirmation screen.
Screen message:
“OneKey Sponsored — Network fee: 0. Send Free.”
Unlike the CoW Swap route I had tried earlier, the Binance Web3 route showed OneKey’s “Send Free” option during the transaction flow.
This was particularly useful after the earlier ETH gas problem.
OneKey provides gas sponsorship for certain eligible transactions. When a transaction qualifies, the confirmation screen can show that OneKey is covering the applicable network fee.
But there is an important distinction:
Sponsored fee does not mean the entire swap is free.
The swap can still involve differences caused by the quoted exchange rate, provider fees, price impact, or other execution costs.
I therefore treated “Send Free” as evidence that the specific eligible network fee shown in that step was sponsored — not as proof that every cost associated with the swap had disappeared.
Availability can also vary. If the sponsored option does not appear on your own confirmation screen, do not assume OneKey will cover the gas fee.
5. How Much USDC Did I Actually Receive?
The swap ultimately completed through Binance Web3.
I started with:
445 USDT0
And after the conversion, my OneKey wallet showed:
444.3212 USDC
That gives us three different numbers from the same experiment:
| Stage | Amount |
|---|---|
| Starting balance | 445 USDT0 |
| Earlier CoW Swap quote | ~444.5097 USDC |
| Binance Web3 quote | ~444.4128 USDC |
| Final OneKey balance | 444.3212 USDC |
The numerical difference between the starting amount and final balance was 0.6788 tokens, or roughly 0.153% relative to the starting amount.
But I would not call that a 0.153% OneKey fee.
USDT0 and USDC are different assets, and the final difference can reflect the exchange rate, route execution, and transaction-related costs.
The practical lesson is simpler:
Compare what you send, the live quote, and what actually arrives.
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6. Connecting OneKey to Hyperliquid
Once I had USDC, I moved on to Hyperliquid.
I traded on the official Hyperliquid interface. OneKey held my keys and handled the wallet approvals.
On desktop, I selected WalletConnect on Hyperliquid, scanned the QR code with the OneKey app, and approved the connection on my phone.
Hyperliquid also required me to enable trading through a wallet signature.
A signature is not automatically the same thing as sending funds, but that does not mean every signature request should be approved blindly.
Read what the wallet is asking you to sign, especially when a request involves token permissions, contract interactions, or transfers.
And never enter your recovery phrase into a trading website.
7. Depositing USDC Into Hyperliquid
I deliberately used a small amount for the test rather than sending my entire balance.
Before depositing, check the route and minimum shown in the current Hyperliquid interface. Deposit methods have changed over time, and different routes can have different requirements.
I entered 10 USDC.
OneKey then showed the transaction confirmation.
During my test, the Hyperliquid interface displayed a 0.2 USDC deposit cost, and 9.8 USDC was reflected in my trading balance.
That was what I observed during this particular test. I would not treat 0.2 USDC as a permanent or universal Hyperliquid deposit fee.
I also encountered wallet signature and contract interaction screens during the process.
Review these requests individually rather than treating them as routine confirmation buttons.
8. I Also Tested Trading and Withdrawal
I continued the experiment after the deposit.
I opened a small BTC perpetual futures position and later withdrew funds back to OneKey.
After a separate 2 USDC withdrawal test, my OneKey transaction history showed:
+1.8 USDC received
I also encountered a separate one-time account activation charge during the first withdrawal process.
Those costs belong to the Hyperliquid test, not to the earlier OneKey USDT0 → USDC swap.
For the full deposit, trading fee, activation fee, and withdrawal breakdown:
Hyperliquid Deposit, Trading Fees & Withdrawal: What I Actually Paid
Frequently Asked Questions
Can I swap USDT0 to USDC in OneKey?
Yes. I completed a 445 USDT0 → USDC swap on Arbitrum through Binance Web3 inside OneKey.
The available providers, quotes, and execution conditions can change, so check the live information in your own wallet.
Why did my OneKey swap fail even though I had enough USDT0?
My first CoW Swap route required an on-chain token approval, and I did not have enough ETH on Arbitrum for that step.
Having enough of the token you want to swap does not necessarily mean you have enough of the network’s native token for every transaction.
What does “Send Free” mean in OneKey?
In my test, OneKey displayed “Send Free” during the Binance Web3 flow.
OneKey provides gas sponsorship for certain eligible transactions, meaning it can cover the applicable network fee for that step.
Check your own confirmation screen because eligibility can vary.
Does OneKey Sponsored mean the swap is completely free?
No.
Gas sponsorship can cover an eligible network fee, but the swap can still involve exchange-rate differences, provider costs, price impact, or other transaction-related costs.
Can I connect OneKey to Hyperliquid?
Yes. I connected OneKey to Hyperliquid through WalletConnect during this test.
Do I need ETH to swap on Arbitrum?
It depends on the route and transaction.
My CoW Swap approval required ETH and failed because my balance was insufficient. Another eligible transaction later showed OneKey’s sponsored “Send Free” option.
Do not assume either outcome will apply to every swap.
Final Thoughts
My test started with 445 USDT0 and ended with 444.3212 USDC after the swap completed through Binance Web3.
The more interesting part was what happened in between.
The first CoW Swap route ran into an ETH gas problem. Another route showed OneKey’s sponsored fee option. And the amount I finally received was different from both earlier quotes.
That is why I would not judge a wallet swap by a single advertised number.
Check the route, check what the wallet is asking you to approve, and compare the live quote with what actually arrives.
From there, I was able to connect OneKey to Hyperliquid through WalletConnect, deposit a small amount of USDC, trade, and withdraw back to the wallet.
Check the route, check what the wallet is asking you to approve, and compare the live quote with what actually arrives.
Tested October 29–30, 2026. Wallet interfaces, providers, sponsorship eligibility, fees, supported networks, and Hyperliquid deposit methods can change.
Risk disclosure: This article documents my own test and is for educational purposes only. It is not financial advice. Crypto swaps and decentralized perpetual futures involve market, liquidation, smart-contract, wallet, and transaction risks.
Affiliate disclosure: This draft currently contains no affiliate links. If compensated links are added later, they will be clearly disclosed.