For Protocol Developers

What is CTX No-CPI?

vaea-flash-ctx is an on-chain crate that lets any Solana program verify it's executing inside a flash loan — without consuming any CPI depth. One function call. Zero cross-program invocation.

ℹ️ Note

This documentation is for Solana program developers building protocols in Rust (Anchor or native). If you're building a bot, liquidator, or script that needs to borrow capital, see the SDK documentation instead.

Why CTX Exists

Many protocols need to know if their instruction is executing inside a flash loan. A lending protocol might want to restrict certain actions during flash loans. A vault protocol might need to confirm that borrowed funds will be repaid atomically.

The naive approach — calling the flash loan program via CPI to ask "is there an active loan?" — consumes one CPI level. On Solana, the limit is 4 levels. In complex call chains (Protocol → Jupiter → AMM → Token Program), one lost level can make the transaction impossible.

CTX solves this by reading a 99-byte PDA instead. Account read. Not a CPI. Zero depth consumed.

How It Works

When a user borrows via VAEA's begin_flash instruction, the on-chain program creates a FlashState PDA (99 bytes). This account exists only for the duration of the transaction. Your program receives this account as a read-only input and calls vaea_flash_ctx::verify(), which:

✅ Checks owner

flash_state.owner must be the VAEA program ID

✅ Validates PDA

Seeds match ["flash", payer, token_mint]

✅ Scans sysvar

Confirms begin_flash before and end_flash after

✅ Returns context

amount, token_mint, fee, payer, source_tier

What verify() Returns

On success, verify() returns a FlashContext struct with all the loan details your program needs:

Field	Type	Description
amount	u64	Borrowed amount in native token units
token_mint	Pubkey	Mint address of the borrowed token
fee	u64	VAEA fee in native units
payer	Pubkey	Public key of the borrower
source_tier	u8	0 = SDK, 1 = UI, 2 = Protocol CPI
slot_created	u64	Slot when the flash loan began

Package

Crate	Registry	Install	Dependencies
vaea-flash-ctx	crates.io	`vaea-flash-ctx = "0.1"`	solana-program only — no Anchor required

Status

Milestone	Status
Devnet deployment	✅ Live
vaea-flash-ctx crate	✅ Ready
Mainnet launch	April 2026
crates.io publication	Post-mainnet

💡 Tip

Program ID (devnet): HoYiwkNB7a3gmZXEkTqLkborNDc976vKEUAzBm8YpK5E. The crate source is available in the VAEA monorepo.