Directional perp venues fail because the LP vault is the permanent counterparty to a crowded book. PrismPerp never asks a vault to hold that bag: it reprices the imbalance until someone else wants it.
borrowRate_dominant = baseFee × ( (OI_dominant + depth) / (OI_counter + depth) )²- baseFee
- 0.18% of notional per 8h at launch; the owner can move it, never above 1%
- depth
- 100,000 USDG: the open interest below which imbalance is not charged as a thin book
On a deep book at 50/50 the multiplier is 1 and both sides pay the base rate. At 80/20 the dominant side pays 16× base; at 90/10, 81×. The counter side pays nothing, which is what pulls the book back. Depth is what keeps the first trader into an empty market — a one-sided book by definition, with the pool on the other side — from paying the saturated rate: a lone 1,000 USDG position pays about 1.02× base. On a real book depth still matters: at 90/10 a 1,000,000 USDG book pays 25× base and a 10,000,000 one 68×, so 81× is the limit as a book deepens. The multiplier is capped at 10,000×, so a nearly empty side can never produce a rate nobody can pay.
| Skew (L/S), deep book | Multiplier | Effective 8h fee | Regime |
|---|---|---|---|
| 50 / 50 | 1.0× | 0.18% | Balanced |
| 65 / 35 | 3.4× | 0.62% | Normal drift |
| 80 / 20 | 16.0× | 2.88% | Crowded |
| 90 / 10 | 81.0× | 14.58% | Crowded |
Borrow accrues into a cumulative index per side and is charged when a position closes, into the pool that is every position's counterparty. It eats the same buffer a price move does, so a position can be liquidated by cost alone.