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The vault is the heart of the protocol — a PDA that holds state and delegates authorization and fees to pluggable programs. A manager has execution rights under constraints, never direct fund control.

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The Vault struct

pub struct Vault {
    pub policy_account: Pubkey, // Pluggable validation program
    pub seed: String,           // PDA seed
    pub authority: Pubkey,      // Manager address
}
Vaults are PDAs with customizable seeds. The policy_account points at the authorization program; the authority is the manager who can propose and execute transactions under that policy’s constraints.

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The Transaction struct

pub struct Transaction {
    pub nonce: u64,
    pub did_execute: bool,
    pub vault: Pubkey,
    pub program_id: Pubkey,
    pub data: Vec<u8>,
    pub accounts: Vec<TransactionAccount>,
}
A proposed CPI is stored in a Transaction PDA before it can execute. did_execute is a one-shot replay guard.

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PDAs explained

A Program-Derived Address is a deterministic Solana address derived from a program plus a seed — it has no private key, so only the owning program can sign for it. Hyro uses two distinct PDAs to separate duties:
PDASeedsRole
vault.authority[vault]Signs outbound capital and executed CPIs
vault_share_signer["vault_share_signer", vault]Owns the vault token account, mints/burns LP shares

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The non-custodial security triangle

A manager never signs as the vault. To act, the manager:
1

Proposes via create_tx

Calls create_tx with a proposed CPI — target program id, accounts, and instruction data — stored in a Transaction PDA. The core fires validate(Creation), which the policy may reject.
2

Executes via execute_tx

Later, execute_tx fires validate(Execution) and, only on approval, replays the proposed CPI with invoke_signed under the vault’s authority PDA.
The manager holds execution rights under constraints, never custody. The proposal and its execution are authorized independently — this is the multisig-like pattern at the core of the protocol.

Validation CPI

The validate interface, in detail.

Program topology

How the programs connect.