Flash Loan

Atomic flash loans with configurable fees and LP share-based liquidity pools

Pending Anchor 0.32

Program ID 2chVPk6DV21qWuyUA2eHAzATdFSHM7ykv1fVX7Gv6nor

Repository ExpertVagabond/solana-flash-loan

Default Fee 9 bps (0.09%)

Cluster Devnet

Instructions

IX initialize_pool

Creates a new lending pool for a specific SPL token mint.

Parameter	Type	Description
`fee_basis_points`	`u16`	Flash loan fee in basis points (9 = 0.09%)

IX deposit

Deposits tokens into the lending pool, receiving LP shares proportional to the pool value.

Parameter	Type	Description
`amount`	`u64`	Amount of tokens to deposit

IX withdraw

Burns LP shares and returns the proportional token amount (including accrued fees).

Parameter	Type	Description
`shares_to_burn`	`u64`	Number of LP shares to redeem

IX borrow_flash_loan

Borrows tokens atomically from the pool. Creates a receipt PDA that must be closed by repay_flash_loan within the same transaction.

Parameter	Type	Description
`amount`	`u64`	Amount of tokens to borrow

IX repay_flash_loan

Repays the borrowed amount plus fee. Closes the receipt PDA and refunds rent to the borrower. Fee accrues to the pool, increasing LP share value.

Parameter	Type	Description
No parameters — reads amount and fee from receipt PDA

IX update_pool_config

Admin-only instruction to update pool fee or pause/unpause the pool.

Parameter	Type	Description
`new_fee_basis_points`	`Option<u16>`	New fee (0–10000 bps)
`is_active`	`Option<bool>`	Pause or unpause the pool

Accounts

LendingPool

Field	Type	Description
`admin`	`Pubkey`	Pool creator and admin authority
`token_mint`	`Pubkey`	SPL token mint for this pool
`vault`	`Pubkey`	PDA-owned token vault
`total_deposits`	`u64`	Total deposits (grows with fees)
`total_shares`	`u64`	Total LP shares issued
`total_fees_earned`	`u64`	Lifetime fee counter
`fee_basis_points`	`u16`	Fee rate (9 = 0.09%)
`is_active`	`bool`	Whether the pool accepts loans
`bump`	`u8`	PDA bump seed

DepositReceipt

Field	Type	Description
`pool`	`Pubkey`	Lending pool this deposit belongs to
`depositor`	`Pubkey`	Depositor's wallet
`shares`	`u64`	LP shares owned
`last_deposit_ts`	`i64`	Timestamp of last deposit
`bump`	`u8`	PDA bump seed

FlashLoanReceipt

Field	Type	Description
`pool`	`Pubkey`	Pool being borrowed from
`borrower`	`Pubkey`	Borrower's wallet
`amount`	`u64`	Amount borrowed
`fee`	`u64`	Fee owed
`bump`	`u8`	PDA bump seed

PDA Derivation

lending_pool

seeds = [b"lending_pool", token_mint]

pool_vault

seeds = [b"pool_vault", pool]

deposit_receipt

seeds = [b"deposit_receipt", pool, depositor]

flash_loan_receipt

seeds = [b"flash_loan_receipt", pool, borrower]

Error Codes

InvalidFee Fee must be between 0 and 10000 basis points

InsufficientLiquidity Not enough tokens in the pool for the requested loan

InvalidAmount Flash loan amount must be greater than zero

PoolPaused Pool is paused by admin

Unauthorized Signer does not match expected authority

MintMismatch Token mint does not match pool's token mint

MathOverflow Arithmetic overflow

InsufficientShares Not enough LP shares for withdrawal

Usage Example

import { getProgram, findLendingPoolPda, findFlashLoanReceiptPda } from "./src";

const flashLoan = getProgram("flashLoan", provider);

// Derive PDAs
const [poolPda] = findLendingPoolPda(tokenMint);
const [receiptPda] = findFlashLoanReceiptPda(poolPda, borrower.publicKey);

// Borrow + repay in same transaction
const borrowIx = await flashLoan.methods
  .borrowFlashLoan(new BN(1_000_000))
  .accounts({ pool: poolPda, vault, borrowerTokenAccount, borrower: borrower.publicKey })
  .instruction();

// ... your arbitrage/swap logic here ...

const repayIx = await flashLoan.methods
  .repayFlashLoan()
  .accounts({ pool: poolPda, flashLoanReceipt: receiptPda, vault, borrowerTokenAccount })
  .instruction();

// Submit as single atomic transaction
const tx = new Transaction().add(borrowIx, /* swap ixs */, repayIx);

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