The layers
A PT on a savings dollar usually sits on a stack: the PT, the SY wrapper, the savings token, the dollar token beneath it, and whatever backs that dollar. Some markets add more: a vault that holds the token, or a wrapper that only changes the number of decimals a token is counted in. Each layer is a contract, and each can have its own rules for getting out.
Vaults (ERC-4626)
Many yield tokens are vault shares under the ERC-4626 standard: a deposit mints shares, and each share is a claim on part of the vault's assets, which grow as the vault earns and shrink if it loses. The standard says how to deposit and withdraw, and a withdrawal it accepts is paid at once, but it lets a vault limit or switch off withdrawals. A vault whose assets need time to unwind usually adds a request-then-claim step, standardised separately as ERC-7540.
Cooldowns, queues and unbonding
- A cooldown is a fixed wait between asking to withdraw and receiving the asset, set in the contract. The asset pages give the figure the issuer publishes and, where the contract reports one, the figure read from it.
- A withdrawal queue serves requests in order as assets come back. Its length depends on how many others are waiting.
- Unbonding is the wait a staking network imposes before staked tokens can move.
- Some tokens can be redeemed only by approved holders after identity checks; everyone else leaves by selling.
Any of these can be longer under stress than in a normal week, and the token's market price can stay below its redemption value while they last.
Who can change a contract
Most of these contracts can be changed. An upgradeable contract (a proxy) runs code that its admin can replace; others have an owner who can pause them, change fees or set limits. Who holds that power, and how fast it can be used, is part of what the token is.
- A single key can act at once.
- A multisig needs several signatures, for example 3 of 5, and can still act at once when they agree.
- A timelock makes every change it controls wait a set delay, such as 48 hours, during which anyone can see it coming. Powers outside it, such as a pause, may still act at once.
- An immutable contract's code cannot be replaced. It may still have an owner who can set some parameters, such as fees.
The asset pages name the holder of these powers where it could be read from the chain or found in the issuer's documents, with the date it was read.
Audits and bug bounties
An audit is a review of the code by a named firm at a point in time: it covers the code it lists, as that code stood then. A bug bounty is a standing offer to pay whoever reports a flaw. The asset pages link to the reports and programmes themselves. Neither is a statement that the code is safe.