Deposit

Send USDC to the ksUSD vault and get ksUSD back at the current share price. How many tokens you get depends on that price, so a deposit made later buys fewer tokens, each worth more.

New here? Read What is ksUSD? first.

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The instruction

deposit(usdc_amount: u64)

One transaction does all three steps, or none of them:

• Moves your USDC into the vault's USDC account

• Mints ksUSD to you at the current share price

• Updates the vault's record of what it holds

The accounts below use two Solana conventions. A PDA is an account the program controls directly, with no private key behind it. An ATA is the standard token account a wallet holds a given token in.

Account	Mutability	Purpose
vault	mut	Vault PDA (seeds: [b"vault"])
vault_usdc_account	mut	Vault's USDC ATA — receives the deposit
ksusd_mint	mut	ksUSD share mint — vault PDA is authority
user_usdc_account	mut	Depositor's USDC source ATA
user_ksusd_account	mut	Depositor's ksUSD destination ATA
user	signer	Depositor
phoenix_trader	—	Phoenix trader account — read to true up the venue's contribution to NAV before pricing. Pinned to vault.phoenix_trader
sol_oracle	—	Pyth SOL/USD — values the perp leg for that same correction. Pinned to vault.sol_oracle
token_program	—	SPL token program

phoenix_trader and sol_oracle are required on every deposit, not only in Normal mode. While the vault is Parked they are read and ignored; in Normal mode the deposit re-books the venue's real equity into NAV first, so the shares you mint are priced against the position as it actually stands.

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Share-price math

In plain terms, one division:

ksUSD you get = USDC you send ÷ current share price

Deposit $100 while a share is worth $1.03 and you get 97.09 ksUSD. Deposit $100 while it's worth $1.00 and you get 100. Either way you own $100 of the vault the moment the transaction lands; the price only decides how many tokens that is.

The same thing in the integers the program actually stores:

effective_nav_usdc = cached_nav_usdc − queue_pending_usdc − pending_perf_fees_usdc
share_price_1e9    = effective_nav_usdc × 1e9 / max(total_shares, 1)
shares_to_mint     = usdc_amount × 1e9 / share_price_1e9    // both sides 6 decimals

share_price_1e9 is dollars scaled by 1e9, so 1_030_000_000 reads as $1.03. Multiplying by 1e9 before dividing by it cancels the scale out, which is why usdc_amount and shares_to_mint are both plain 6-decimal amounts. The division truncates, so any fraction of a base unit is left in the vault rather than minted, so it can never round in the depositor's favour at other holders' expense.

deposit calls accrue_perf_fees before it prices your mint. That advances the high-water mark to the current price first, so you're never charged a performance fee on gains the vault made before you arrived.

The first deposit into an empty vault mints shares 1:1 at $1.00, since the starting share_price_1e9 is 1_000_000_000. Every deposit after that mints fewer shares, because the share price has drifted up with the carry earned so far. Full derivation and a worked example in NAV & share pricing.

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Capacity

The vault ships with a $500k deposit cap. That isn't a demand estimate. It is roughly the largest short Phoenix's book can absorb, and it re-sizes as the venue grows.

It's a hard cap rather than a soft target because the vault only earns while its dollars are in the hedge. Whatever it can't short sits in USDC lending instead. A cap set above what the venue can hold doesn't add yield; it dilutes the part that does, until ksUSD is a Kamino deposit wearing a wrapper, carrying all of the operational risk for none of the carry.

So the cap tracks the venue:

max short = min( 15% of Phoenix SOL-PERP OI , 25% of the 30-day MEDIAN daily volume )

The volume limb is a quarter of a day's flow because exit is harder than entry: that is about what a clean unwind can take. On Phoenix's numbers measured 16 September 2026 the open-interest limb binds, by roughly 2.2×: $4.73M of OI gives $709k, against $1.59M from volume. In early August it was the other way round, so the rule takes whichever is tighter.

The word median matters. A few spike days can sit inside any 30-day window and pull the mean above the median, and sizing off the mean would imply a short the venue couldn't absorb on an ordinary day.

The ramp

Phase	Cap	Opens when Phoenix has
Launch (private beta)	$500k	roughly today's book
Next tier	$1M	roughly twice today's open interest
Public	$5M → $25M	a far deeper book

Tiers open against the live book, not on a date. There is no second Solana perp venue deep enough to split the short across, so the ramp follows Phoenix.

Reading the cap live

deposit_cap_usdc is a u64 on the Vault account. 0 pauses deposits outright, u64::MAX means uncapped, anything else is a hard ceiling.

const vault = await program.account.vault.fetch(vaultPda);

// Headroom is measured against CACHED nav, not effective nav: queued
// withdrawals are netted out of TVL but still occupy
// cap room, so effective NAV would overstate what you can actually deposit.
const remaining = BN.max(
  vault.depositCapUsdc.sub(vault.cachedNavUsdc),
  new BN(0)
);

Admins move the cap with update_params. Recompute it against the live book first, rather than trusting a constant, since both inputs move week to week.

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Guardrails

A deposit can be blocked by any of three things:

• The vault is paused. The admin can pause it with set_pause in an emergency.

• The deposit cap is hit. A deposit reverts with DepositCapExceeded if cached_nav_usdc + usdc_amount > deposit_cap_usdc. See Capacity above.

• The amount is zero. usdc_amount must be greater than 0.

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TypeScript example

import { Program, BN } from "@coral-xyz/anchor";
import { PublicKey } from "@solana/web3.js";
import { TOKEN_PROGRAM_ID, getAssociatedTokenAddressSync } from "@solana/spl-token";

const PROGRAM_ID = new PublicKey("E7tpCcxtvuTXLAckBGWb1AsndpLQ1Y9hQA3iGYSXz2vJ");

const [vaultPda] = PublicKey.findProgramAddressSync(
  [Buffer.from("vault")],
  PROGRAM_ID
);

const vault = await program.account.vault.fetch(vaultPda);
const userUsdcAta  = getAssociatedTokenAddressSync(vault.usdcMint,  user.publicKey);
const userKsusdAta = getAssociatedTokenAddressSync(vault.ksusdMint, user.publicKey);
const vaultUsdcAta = getAssociatedTokenAddressSync(vault.usdcMint,  vaultPda, true);

const tx = await program.methods
  .deposit(new BN("100_000_000"))         // 100 USDC (6 decimals)
  .accountsStrict({
    vault: vaultPda,
    vaultUsdcAccount: vaultUsdcAta,
    ksusdMint: vault.ksusdMint,
    userUsdcAccount: userUsdcAta,
    userKsusdAccount: userKsusdAta,
    user: user.publicKey,
    phoenixTrader: vault.phoenixTrader,   // required on every deposit
    solOracle: vault.solOracle,
    tokenProgram: TOKEN_PROGRAM_ID,
  })
  .rpc();

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Events

DepositEvent is emitted on success:

pub struct DepositEvent {
    pub user: Pubkey,
    pub usdc_amount: u64,
    pub shares_minted: u64,
    pub share_price_1e9: u64,
    pub new_total_shares: u64,
    pub timestamp: i64,
}

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Related

• Withdraw — instant vs. queued paths

• Check position & NAV

• NAV & share pricing

• Errors