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Deploying and Managing a V3 Vault

V3 makes it as simple as possible for anyone to deploy and manage their Vaults. No longer will Yearn be the only manager of Vaults, gate-keeping who can be debt allocator, or what strategies should be added to a vault. Now, anyone can deploy, manage, and earn fees from their vision and preferences for everything from risk profile, fee model, decentralization, etc.

In V3 our "Meta Vaults" or "Vaults of Vaults" are designed to be efficient 4626 compliant debt allocators that can have many different "strategies" attached to them and will direct funds to these strategies based on the vault's management choice. The vaults are built to be "plug and play" meaning managers can simply deploy, add their strategies, and start the yield generation. But they also hold many customization factors, allowing different managers to differentiate themselves and experiment with different optionalities.

Running your vault requires no need to know how to code. Anyone desiring to manage their strategies and allocations can simply deploy and run their vault.


  • vault: ERC-4626 compliant contract that accepts deposits, issues shares, and allocates funds to different strategies to earn yield.
  • shares: A tokenized representation of a depositor's share of the underlying balance of a vault.
  • strategy: Any ERC-4626 compliant contract that can be added to a vault that earns yield on an underlying asset.
  • debt: The amount of the underlying asset that a vault has sent to a strategy to earn yield.
  • report: The function where a vault accounts for any profits or losses a strategy has accrued, charges applicable fees, and locks profit to be distributed to depositors.


Each release of the vaults will have its own "Vault Factory" deployed to make it as simple and trustless as possible to deploy your vault. The vault factory utilizes ERC-5202 blueprint pattern to allow anyone to trustlessly deploy their vault which is an exact copy of the previously deployed "blueprint" vault for that specific version.

** Vaults not deployed through the factory will not be recognized as part of the Yearn ecosystem and may cause issues during runtime.

To deploy your vault, simply find the factory's address for the most recent release here and call Factory.deploy_new_vault(params).

The needed parameters are:

asset: The ERC-20 compliant token used as the underlying asset to earn yield for the vault. name: The name for your vault that will apply to the token issues to depositors. symbol: The symbol the token issued to depositors will use. role_manager: The address in charge of giving permissions to other addresses which allow access to certain permissioned functions. profit_max_unlock_time: In seconds, profits reported from strategies will be unlocked.

The blueprint ERC standard lowers the gas cost compared to a traditional off-chain deployment, however, deployments of the vaults are still expected to be relatively expensive costing over 400k gas.

Once deployed, you can get your vault's address from either the Factory function's return value or the NewVault event emitted by the factory.

The vault should be automatically verified when deployed. However, if it is not you can follow the verification steps on Etherscan using the VaultV3.vy for your specific API Version.

NOTE: The vault factory utilizes create2 opcode to deploy vaults to deterministic addresses. This means the same address can not deploy two vaults with the same default parameters for 'asset', 'name' and 'symbol'.


Once deployed, additional setup steps and variables can be configured if desired.


The first is to set up the Roles for your specific vault. The vaults use a role-based system for access control to the permissioned functions. The roles are a Vyper Enumerator pattern based on Python.

Each permissioned function in the Vaults has its own "role" that can call that specific function. For example, to call add_strategy(new_strategy: address) the address must have the ADD_STRATEGY_MANAGER role. Roles can be held by any number of addresses or by no address. There is also the option to "open" any role, meaning the function becomes permissionless. (This is not recommended for most permissioned functions and should be done carefully.)

The same address can hold every role, each role can be helped by a different address or any combination desired.

To give an account a specific role can simply call vault.set_role(account, role) where 'role' is the int representing all the roles you would like the 'account' to hold. A full explanation of python enumerators is beyond the scope of this doc, but the corresponding int to each role can be viewed here


# Set `account` to be the ADD_STRATEGY_MANAGER
vault.set_role(account, 1)

# Set `account` to be the REVOKE_STRATEGY_MANAGER
vault.set_role(account, 2)

vault.set_role(account, 3)

# Set `account` to hold every role
vault.set_role(account, 8191)

# Set `account` to hold no roles
vault.set_role(account, 0)

NOTE: The vault role_manager can not call any permissioned function by default, and would have to give itself any roles that it should have.

Deposit Limit

Each vault will default to have a deposit limit set to 0. Which means all deposits will revert.

Once ready, the address with the DEPOSIT_LIMIT_MANAGER will need to call vault.set_deposit_limit(deposit_limit)


There are other options that a vault manager can set that are not necessary for the vault to function but may be desired for further customization.

minimum_total_idle: An amount specified in the underlying asset that the vault will force to remain free in the vault during debt updates to make servicing withdraws cheaper. profit_max_unlock_time: The time in which profits reported by the strategies will be distributed to depositors. This can be adjusted to match the current report cycle of the vault's strategies to create a continuous stream of APY paid out to depositors.

Running the Vault

Strategy Management

The job of a vault is to manage debt between strategies that do the yield generation. 3 roles control what strategies are added to the vault, ADD_STRATEGY_MANAGER, REVOKE_STRATEGY_MANAGER, and FORCE_REVOKE_MANAGER.

A strategy can be any contract that has the needed 4626 interface for the vault to interact with it. This includes Tokenized Strategies, 3rd party 4626 vaults, and other Yearn meta vaults.

To add a strategy first call vault.add_strategy(strategy_address). Each strategy gets added with a default 'max_debt' of 0. This means the MAX_DEBT_MANAGER will need to call vault.update_max_debt_for_strategy(strategy, max_debt).

Once a strategy has been added and given a max_debt, the DEBT_MANAGER role can allocate funds.

To remove a strategy, first remove all the debt from the strategy and then call vault.revoke_strategy(strategy).

If a strategy has issues and cannot pay all of its debt back vault.force_revoke_strategy(strategy) can be used to forcefully remove the strategy.

NOTE: Forcefully removing a strategy that still has debt will cause a loss to be recorded and a reduction of Price Per Share.

Debt Updates

The DEBT_MANAGER role is in charge of allocating funds between the strategies added to a vault.

All debt updates are denominated in the underlying asset and are restricted by the max_debt for each strategy and the minimum_total_idle for the specific vault.

Debt updates will also respect the strategies specific maxWithdraw and maxDeposit.

To deposit or withdraw vault funds from a strategy simply call vault.update_debt(strategy, desired_debt) where desired debt is the end amount denominated in the underlying asset that the strategy should have after the full debt update.

NOTE: If a strategy has unrealized losses you cannot lower its debt. NOTE: It is recommended to report a strategy's gain before withdrawing 100% of debt from the strategy.


To properly record any profits/losses from a strategy, charge fees, and lock profits for distribution to depositors, the REPORTING_MANAGER will need to "report" for each strategy via vault.process_report(strategy).

This function will trigger all necessary logic to record a strategy's gain since the last report and begin distributing that profit to depositors over the vault's specific profit_max_unlock_time.

NOTE: To charge fees you will need first to have added an 'accountant' to your vault that will hold the fee logic and receive the fees that are charged.

NOTE: All profit and loss calculations use the strategies 'convertToAssets' function. If this function can be manipulated it can lead to incorrect profits or losses being recorded by the vault



You will need to add a separate contract as the vault's 'accountant' to charge fees.


The accountant is called by the vault during every report with the strategy that is reporting and the gain or loss it's reporting. The accountant will then return the total fees or refunds that should be charged by the vault during that report and paid to the accountant.

Accountants can hold any logic that vault managers want to dictate fees or simply charge normal performance or management fees. A ready-to-use Generic Accountant can easily be used with any vault for those who wish just to charge standard fees.

See Here:

Default Queue

Each vault has a default_queue based on the strategies added and removed from the vault. The default_queue is used to service withdraws when no custom queue is passed. This queue is simply ordered by the time when strategies were added: where the oldest strategy is at the beginning of the queue.

If a different ordering is desired or management wants to remove a certain strategy from the default queue, the QUEUE_MANAGER role can set a new queue.


Where new_default_queue is an array of strategies with a max length of 10, in which all strategies are currently active in the vault.

Good to Know

What Tokens Not to Use

There are certain tokens whose native behavior makes them incompatible with being the underlying asset of a vault and should be avoided.

A few examples of this are:

  • Rebasing Tokens
  • Fee on Transfer
  • Re-entrancy Tokens (ERC-777)

Any token whose normal functionality breaks the ERC-20 standard may not be compatible with V3 vaults.