TL;DR
OneKey only charges a one-time fee when you purchase a PT with a non-underlying asset. Buying with the underlying asset, holding PT, and redeeming at maturity (to any asset) — none of these incur any swap fee.
1. When are fees charged? When are they not?
1.1 Fee rules at a glance
Scenario | Swap path | Fee |
Buying PT directly with the underlying asset | underlying → PT | Free |
Buying PT with another asset (OneKey auto-routes) | Token A → underlying → PT | One-time dynamic fee |
Holding PT | — | Free |
Redeeming at maturity to any asset | PT → underlying → any token | Free |
⚙️ About "auto-routing" The swap paths above are executed automatically by OneKey in the background. In the app, you only see one action: "you paid Token A and received PT." The intermediate routing is completed in a single signature — no manual steps required.
This auto-routing capability is the service OneKey provides — finding the best execution path on the market for you. The dynamic fee is what pays for this service.
1.2 Concrete examples
A few common PTs:
PT you want to buy | Underlying asset | Buy with the underlying(free) | Buy with another asset(one-time dynamic fee) |
sUSDe | sUSDe | sUSDe → PT | USDC / USDT / ETH → sUSDe → PT |
USDe | USDe | USDe → PT | USDC / USDT / ETH → USDe → PT |
weETH | weETH | weETH → PT | ETH / WETH / USDC → weETH → PT |
sUSDS | sUSDS | sUSDS → PT | USDS / DAI / USDC → sUSDS → PT |
wstETH | wstETH | wstETH → PT | ETH / WETH / USDC → wstETH → PT |
💡 Quick check: Open the Fixed Income page in OneKey App. The asset listed there is the underlying asset. If you already hold it, your purchase is free. If you don't, OneKey auto-routes for you and charges a single dynamic fee.
2. How does the dynamic fee change?
The dynamic fee is determined by two real-time variables:
Effective APY (EAPY): the implied annualized yield along the current execution path
Time to Maturity (TTM): the remaining time until the PT matures
The fee adjusts automatically — always in the direction that favors you:
Scenario | Fee tendency |
High APY + long time to maturity | Higher fee (still capped by the global limit) |
Lower APY | Fee scales down automatically |
Close to maturity | Fee keeps falling, drops to 0 on maturity day |
Market slippage is already high | OneKey does not stack any additional swap fee |
💡 Three design principles working in your favor:
You earn less, you pay less. The fee is tied to your potential yield space and always stays below a fixed share of your theoretical return — your earnings can never be eaten up by fees.
The closer to maturity, the lower the fee. As remaining time shrinks, the fee approaches zero. Buy a PT on the day of maturity and OneKey charges nothing.
If the market is already costing you, OneKey steps aside. When liquidity is thin and market slippage is already high, you've effectively paid a market cost on this trade. In that case, the routing fee waives itself to protect your net return.
3. What protection mechanisms are in place?
To keep your costs predictable, the final fee is bound by two strict constraints:
Principal protection cap: the fee's share of your theoretical yield is hard-capped. Across any combination of APY and time-to-maturity, the fee will never exceed a fixed proportion of your theoretical return.
Global cap: an absolute upper limit on the fee, guarding against abnormal APY readings or parameter misconfigurations.
The final fee is set by whichever of these two is stricter. However the market moves, you will never be charged more than expected.
4. Why dynamic fees instead of fixed fees?
When designing the fee model, we evaluated two common alternatives — both have serious drawbacks:
Positive slippage: pricing is opaque; you can't predict the actual cost beforehand.
Pure flat fee: in low-yield or near-maturity scenarios, it can eat directly into your principal — leaving you with the awkward "looks like I earned, ended up losing."
That's why OneKey chose a dynamic fee model. The core idea is revenue sharing + principal protection:
When you earn more, OneKey takes a small proportional share, supporting sustainable service revenue.
When you earn little or nothing, the fee scales down — even to zero — so a fee can never push you into a loss.
5. FAQ
Q1: Is there a fee when I buy PT directly with the underlying asset?
A: No. When you already hold the underlying asset for that PT, OneKey doesn't charge any fee.
Q2: Is there a fee for redeeming at maturity?
A: No — regardless of which asset you redeem to. At maturity you can redeem into the underlying asset, or directly into USDC, USDT, ETH, or any other asset — OneKey doesn't charge any swap fee in any of these cases.
Q3: Why does the fee I see change every time?
A: The dynamic fee responds to APY, time-to-maturity, and market liquidity in real time. The closer to maturity or the larger the market slippage, the lower the fee you'll see.
Q4: Will the fee really drop to 0 near maturity?
A: Yes. The fee continuously declines as remaining time shrinks, and falls to 0 on the day of maturity.
Q5: If market slippage is already high, does OneKey pile on top?
A: No. When the path's own slippage is already high, OneKey steps aside and doesn't charge a platform fee.
Q6: Could the fee suddenly spike under extreme market conditions?
A: No. The system has a global cap that holds in any market condition.
Q7: Could the fee push me into an overall loss?
A: Under the dynamic fee model, the fee always stays below a fixed share of your theoretical return — your earnings won't get eaten up. That said, your actual return can still be affected by market interest-rate changes, slippage when selling PT on the secondary market before maturity, and other factors outside the fee mechanism.