Introduction
Fyber in one page — borrow dollars against tokenized US stock exposure, at a rate you set yourself, on contracts that nobody can change.
Fyber is an on-chain lombard loan. You deposit Robinhood stock tokens — SPY, QQQ and a small, fixed list of others — on Robinhood Chain, and you borrow dollars against them without selling. The dollars are fyUSD, a stablecoin you can convert 1:1 into USDG at any time through the protocol's own swap module.
Three things make it different from every other lending market on this chain:
- You set your own interest rate. Not a curve, not a governance vote, not an algorithm that reprices you at 3 a.m. You pick a number at or above the tier floor, and nobody can raise it. Ever.
- Depositors are paid by borrowers, and only by borrowers. Every unit of yield in the Stability Pool has a named payer: it is interest a borrower actually paid, minted straight to the pool as it accrues.
- Nothing can be changed after deployment. There is no admin function, no proxy, no timelock, no parameter setter anywhere in the nineteen contracts. The only human power that exists is the power to close, it is held by a 2-of-3 Safe, and it expires 365 days after launch.
Guarantee
Repaying your debt and adding collateral are never blocked. Not by market state, not by a paused oracle, not by a frozen branch, not by the Closer key, not by anyone. These two functions do not even call the price oracle.
Rules R-4.4.1, P2
What you can do
| If you have | You can | Page |
|---|---|---|
| Stock tokens | Borrow fyUSD against them, at a rate you choose | Borrow |
| An open position | Add collateral, repay, borrow more, change your rate, close | Manage your position |
| USDG or fyUSD | Deposit into a Stability Pool and earn the interest borrowers pay | Earn |
| fyUSD | Swap it for USDG at a fixed price, or redeem it against collateral | PSM, Redemption |
A worked example
You hold 20 SPY tokens, worth $10,000. You deposit them and ask for 5,000 fyUSD at 4% a year.
How it is calculated
collateral ratio = 10,000 ÷ 5,003.84 = 199.8%, above the 125% minimum
liquidation price = 5,003.84 × 1.15 ÷ 20 = $287.72 per token, a 42.5% fall from $500
The extra 3.84 is the origination fee: seven days of interest at your own rate, added to the debt rather than taken out of what you receive. Ninety days later your debt is 5,053.19 fyUSD. You approve that amount, call close(), and your 20 SPY come back.
Rules R-1.1.1, R-5.6.1, R-14.1
The five collateral branches
Five branches are deployed on day one and the list is closed forever. Two are live immediately; three sit dormant and switch themselves on when on-chain metrics — depth, market capitalisation, feed history, Stability Pool size — cross fixed thresholds. No key can force an activation, and no key can prevent one.
| Branch | Tier | Status at launch | Max loan-to-value |
|---|---|---|---|
| SPY | 1 | Active | 80% (125% collateral ratio) |
| QQQ | 1 | Active | 80% |
| VOO or IVV | 1 | Dormant, earliest day 90 | 80% |
| GLD | 2 | Dormant, earliest day 90 | 75% (133.33% collateral ratio) |
| IWM | 2 | Dormant, earliest day 150 | 75% |
A sixth collateral is not an upgrade. It is a different protocol, deployed separately, and you would choose to move to it or not.
Rules R-12.3.1, R-12.3.2
What the protocol is built on
Six properties, each readable on-chain rather than taken on trust:
- Immutable contracts, no admin keys. No proxy, no setter, no timelock, no administrator role. Nobody can mint against your position, pause your repayment, blacklist an address or change a number.
- Interest from real borrowers. Depositors are paid what borrowers actually pay. The Earn pages show two computed figures and the formula behind each, never a target.
- Open at every hour. Borrowing, repaying, redeeming and withdrawing work every hour of every day. Repaying and adding collateral are never paused, in any state.
- Backed by index certificates. Every fyUSD is over-collateralised by tokenized broad-market certificates held raw in a branch contract, never lent out, never pooled across branches.
- Readable on-chain. Every parameter, every formula, every liquidation and every reserve figure is on-chain and reproducible. If a number is shown here, you can recompute it.
- One key, and it expires. It can freeze for at most 72 hours or close for good. It can neither mint nor change anything, and it stops working 365 days after deployment.
Risk
Immutability cuts both ways. A parameter that turns out to be wrong cannot be corrected — it is corrected in a new deployment, which you would have to move to yourself. A component that fails does not get replaced; its branch shuts down in an orderly way and everyone exits. Read Risk summary before you deposit anything.
Where to start
If you hold stock tokens and want dollars: Borrow. If you hold dollars and want yield: Earn. If you want to know whether you are allowed to use this at all: Jurisdictions.
Last reviewed: 2026-09-07 · Spec v0.4