One size, four coins: paying a Monad swap in MON, USDC, wETH or wBTC

A person thinks in MON. The wallet does not only hold MON. It holds WETH, WBTC and a Circle dollar that this chain lists as USDCm. If the only button is “enter 50 MON”, the wrapped coins sit there until someone unwraps or swaps them in a separate step, and that step is a fee. The desk’s answer is to keep the size in MON and let the coin you already hold pay it, in one hop through WMON, without unwrapping first. This page is the arithmetic and the rules. It is not a suggestion that you should rotate.

The size is MON, even when the coin is not

You pick 1, 5, 10, 25, 50, 100 or 500, or you type a figure. That figure is MON. It is not dollars and it is not ether. A 50 MON idea, paid in wETH, spends the quantity of wETH that 50 MON buys at the WETH pool’s slot0. Paid in wBTC, it spends the matching quantity of wBTC. Paid in USDC, it spends the raw 6-decimal amount that 50 MON buys in the WMON/USDC pool. The card you receive is still “in 50 MON” when the inventory covered it. If the inventory is a little short of 50 and still a real stack, above half a MON of value, the button stays lit and the fill spends the whole stack. The size you typed remains the intent. The fill records what actually left.

Work a wETH example with the numbers on the screen. A pool near 106,657 MON per WETH prices 0.000464 WETH at about 49.5 MON. A strict 50 MON button stays dark, and the owner reasonably concludes that wETH cannot be used. The desk now treats a stack above 0.5 MON as an execution. It spends the 0.000464, not a rounded-up quantity the wallet does not have. The same rule applies to USDC and wBTC. Dust below half a MON does not light. A same-asset button never lights: you do not buy WETH with WETH, or USDCm with USDC.

The chip is the idea, in MON. The lit button is the inventory that can fund it. A dark button is a coin that cannot, not a hidden opportunity.

What each button actually sends

MON spends native MON, from the wallet if it holds the size above the gas reserve, or from the vault if the vault holds it. The path is WMON into the asset on that asset’s pool fee. USDC spends USDCm. The path is USDC to WMON on the 500 fee, then WMON to the asset on the asset’s fee. The position is recorded as paid in USDC, and a later close of that fill returns USDC rather than MON. wETH and wBTC spend the wrapped token. The path is the wrapped token to WMON, then WMON to the asset. Nothing is unwrapped. The wrapped token is the input. The position is recorded in MON terms so the card can be read beside the others, and the close of a MON-paid fill returns MON.

Gas is always MON. A wrapped or dollar payment still needs a little native MON for the signature, on the order of 0.005 MON. If neither the wallet nor the vault has that, every non-MON button stays dark even when the inventory is large. That is not a bug in the inventory. It is the chain billing the sender in the native coin, which the gas-pricing page states and which wallets still surprise people with.

Which card you are allowed to buy

The opportunity list is four assets, in this order, whether or not the tape has “called” them: USDC, wETH, wBTC, cbBTC. A call used to hide the other three. It does not any more. USDC is bought with MON, wETH or wBTC. wETH is bought with MON, USDC or wBTC. wBTC is bought with MON, USDC or wETH. cbBTC takes any of the four except itself. The button lights from balances and the spot already in memory. It does not wait for a quoter. If the spot has not been read yet, the button stays dark for that paint and lights on the next one. Do not tap a dark button and call it a failure of the pool. Read the balance row. If the row is near zero, the button is telling the truth.

A worked 50 MON paid three ways

Assume spots of 106,657 MON per WETH, 3,677,000 MON per WBTC, and 45.93 MON per USDC, which is the same fact as a dollar buying that many MON. Fifty MON is about 0.000469 WETH, about 0.0000136 WBTC, and about 1.09 USDC. If the wallet holds more than those quantities, the three buttons light and each spends about those quantities, haircut slightly so the second hop’s fee is inside the size rather than a surprise. If the wallet holds 0.000464 WETH, the wETH button still lights and spends 0.000464, and the card’s spent MON is the spot value of that quantity, not a fictional 50. If the wallet holds 24 USDC, the USDC button lights at the full 50 MON idea, because 1.09 is well inside 24. The other 22.9 USDC stays where it was.

What you should not infer

A lit button is not a recommendation. It is executability. The card’s target and stop are the play you already saw, not a forecast. Paying in wETH to buy wBTC is a rotation, and the two pool fees are the cost of changing your mind. Paying in USDC to buy wETH is the same kind of decision. The desk will not block the button because the fee is larger than today’s drift. You pressed it. It also will not unwrap a coin you did not ask to unwrap. If you wanted MON in the wallet, the close is a separate step, and the trading-key page describes which address is allowed to receive it.