Risk engine

A pure function. Given a proposal, account state and exchange limits, it returns allow or deny plus the clamped values. The model cannot talk its way past it.

Limits

Field	Meaning
`markets`	Allow-list of coins. Anything else is refused.
`maxLeverage`	Your cap. Clamped further to the exchange cap read live from Hyperliquid meta (BTC 40x, ETH 25x at time of writing). A higher cap is clamped, never errors.
`marginPerTradeUsd`	Margin per position, also clamped to withdrawable balance.
`maxOpenPositions`	Concurrent positions across all markets. One position per market.
`maxDailyLossUsd`	Optional kill switch. Once realized PnL since 00:00 UTC (fees included) reaches the negative of this, no new positions open. Closing stays allowed.

Behavior

Clamp: leverage and margin over the limit are reduced and the reduction is reported back to the model.
Deny: disallowed market, duplicate position, full book, kill switch tripped, non-positive inputs, or notional under Hyperliquid's $10 minimum.

import { evaluate } from "perpad";
evaluate(
  { coin: "BTC", side: "long", leverage: 100, marginUsd: 900 },
  { openCoins: [], withdrawableUsd: 1000, dailyPnlUsd: 0, exchangeMaxLeverage: { BTC: 40 } },
  { markets: ["BTC"], maxLeverage: 50, marginPerTradeUsd: 100, maxOpenPositions: 1 },
);
// { allowed: true, adjusted: { leverage: 40, marginUsd: 100 }, reasons: [...clamped] }

Dry-run any proposal from an MCP client with the check_risk tool.