> ## Documentation Index
> Fetch the complete documentation index at: https://docs.exponent.finance/llms.txt
> Use this file to discover all available pages before exploring further.

# APY and Protection

> Calculate current tranche APY and Senior protection metrics

Use APY and protection helpers to preview how a market allocates yield and how a proposed deposit changes Senior protection.

## Current APY

```typescript theme={null}
const underlyingApy = 0.10; // 10%

const seniorApy = market.calculateSeniorApy(underlyingApy);
const juniorApy = market.calculateJuniorApy(underlyingApy);

console.log("Senior APY:", seniorApy);
console.log("Junior APY:", juniorApy);
```

| Function                            | Parameters              | Returns  | Description                         |
| ----------------------------------- | ----------------------- | -------- | ----------------------------------- |
| `calculateSeniorApy(underlyingApy)` | `underlyingApy: number` | `number` | Current marginal APY for Senior LPs |
| `calculateJuniorApy(underlyingApy)` | `underlyingApy: number` | `number` | Current marginal APY for Junior LPs |

`underlyingApy` is a decimal rate. Use `0.10` for 10%.

## APY after deposit

```typescript theme={null}
import { TrancheSide } from "@exponent-labs/exponent-sdk/client/tranching";

const seniorApyAfterDeposit = market.calculateSeniorApyAfterDeposit({
  trancheSide: TrancheSide.Senior,
  amountIn: 1_000_000_000n, // raw SY units for the proposed deposit
  underlyingApy: 0.10,      // 10% underlying APY
});

const juniorApyAfterDeposit = market.calculateJuniorApyAfterDeposit({
  trancheSide: TrancheSide.Junior,
  amountIn: 1_000_000_000n, // raw SY units for the proposed deposit
  underlyingApy: 0.10,      // 10% underlying APY
});
```

| Parameter           | Type               | Description                                                                       |
| ------------------- | ------------------ | --------------------------------------------------------------------------------- |
| `trancheSide`       | `TrancheSide`      | Tranche receiving the proposed deposit                                            |
| `amountIn`          | `bigint`           | Proposed SY amount for the preview, in raw SY token units                         |
| `underlyingApy`     | `number`           | Underlying APY as a decimal rate                                                  |
| `syExchangeRate`    | `number \| string` | Optional decimal exchange-rate override. `1.05` means 1.05 NAV per raw SY unit    |
| `syExchangeRateRaw` | `bigint`           | Optional raw fixed-point exchange-rate override. `1_000_000_000_000n` means `1.0` |

The preview converts `amountIn` with the SY exchange rate into raw fixed-point NAV. It does not apply token mint decimals for display.

## Senior protection after deposit

```typescript theme={null}
const protection = market.calculateSeniorProtectionAfterDeposit({
  trancheSide: TrancheSide.Junior,
  amountIn: 1_000_000_000n, // raw SY units for the proposed deposit
});

console.log("Protected-until price:", protection.protectionPerBaseToken);
console.log("Max drawdown before Senior loss:", protection.maxDrawdownBeforeSeniorLossPct);
```

| Return field                     | Description                                                               |
| -------------------------------- | ------------------------------------------------------------------------- |
| `protectionPerBaseToken`         | Price floor per base token implied by current Junior protection           |
| `maxDrawdownBeforeSeniorLossPct` | Percent market drawdown Junior can absorb before Senior starts losing NAV |

<Note>
  These helpers preview local math. They do not submit a transaction or reserve capacity.
</Note>