Fees and settlement

Where money is

All USDC in the pool sits in one token account, the pool's vault, owned by the Hindsight program. Each participant's share of it is their confidential balance: a commitment on chain whose opening only they hold. The program keeps the vault and the commitments consistent at every step: the openings of all balances and of every outstanding note add up to the pool's principal, and the vault holds at least that.

j \sum b_{j} + i \in notes \sum v_{i} = principal \leq vault

Deposits and withdrawals move the principal with the tokens. Transfers, accepts and returns move value between commitments and leave the principal where it is.

Fees

Hindsight charges one fee: 5 basis points on deposits and withdrawals, the two moments a USDC amount is public anyway. Transfers carry no fee, so nothing about a confidential payment depends on its amount. The fee is in USDC and taken from the amount that moves:

You	The fee	What arrives
Deposit 10,000 USDC	5.00 USDC	9,995.00 USDC in your confidential balance
Send 4,200 USDC	none	4,200.00 USDC in the payee's note
Withdraw 1,000 USDC	0.50 USDC	999.50 USDC in your wallet; your balance drops by 1,000

The fee is $f = ⌊ a \times 5/10, 000 ⌋$ base units of the amount $a$ : it rounds down, so any rounding stays with you.

All of it is the protocol's, and it goes straight to the protocol fee account: a token account of a program address that no key signs for, in the same transaction as your deposit or withdrawal. They leave it only through the buyback, which buys $HINDSIGHT on the market and burns it in the same transaction.

You also pay Solana's own network fee, in SOL, for each transaction your wallet signs, and the rent below.

The pool's policy

These are the live values from the pool's policy on chain:

The pool’s policy, read from the chain	Now

The return timeout is how long a payee has to accept or return a note. After it, the note's sender can take the note back.

Rent

Accounts on Solana hold a small rent deposit in SOL:

Your key record and your account hold rent while they exist. Once your balance is zero, Close your account on the Account page closes both and returns all of that rent to your wallet; the page shows the exact amount. Your device proves the balance is zero without revealing anything else, and you can open the account again later.
Each note holds rent from the transfer until the payee accepts it. Accepting closes the note and refunds its rent to the sender.

Settlement

A payment settles when the payee accepts it: from then on its amount is part of the payee's balance commitment and the note is closed. Until then it is a note in the payee's inbox, and the sender's balance no longer includes it. A payee withdraws to their wallet whenever they choose; the withdrawal is final when its transaction is.