# Liquidity Injector

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**Source:** `src/liquidityInjector/LiquidityInjector.sol`
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## Contract summary

The LiquidityInjector has a special privilege to call `BondToken.mintByLI()` to create BT without backing FW. This is the only way BT can be minted outside the normal FW→BT+CT yield-split path.

## Functions

### `injectLiquidity(params, amount)`

1. Validates `params.irm == address(0)` (fixed-rate market identifier)
2. Calls `BondToken.mintByLI(address(this), amount)` to create BT
3. Approves and supplies BT to the lending market via `lendingMarket.supply()`
4. Increments `marketStats[marketId]`

### `withdrawLiquidity(params, amount)`

1. Checks available liquidity (total supply − total borrows, capped by balance)
2. Withdraws BT from the lending market
3. Burns BT via `BondToken.burnByLI()`
4. Decrements `marketStats[marketId]`

## Invariants

* Owner-only for inject and withdraw
* BT is never held in a resting state — always in the lending market or burned
* `marketStats` tracks net injected amount per market
* Available liquidity check prevents disrupting existing borrows