# Yearn V3 Framework

### [**TokenizedStrategy**](https://docs.yearn.fi/developers/smart-contracts/V3/TokenizedStrategy) **Implementation**

The **TokenizedStrategy** contract is a single, immutable contract deployed at [`0xBB51...feD0`](https://etherscan.io/address/0xBB51273D6c746910C7C06fe718f30c936170feD0), responsible for handling all ERC-4626 functionality across Yearn strategies. Key features include:

* **Accounting and Share Mechanics**: Manages ERC-4626 accounting for deposits, withdrawals, and share balances.
* **Profit/Loss Management**: Calculates profits and losses while managing fee accrual.
* **Profit Unlocking**: Implements profit unlocking mechanisms based on configurable parameters.
* **Pure Logic Contract**: Contains no storage and operates purely as a shared logic layer across all strategies.

### [**BaseStrategy**](https://docs.yearn.fi/developers/smart-contracts/V3/BaseStrategy) **Delegation**

The **BaseStrategy** employs a proxy pattern to delegate functionality to the TokenizedStrategy while maintaining isolated storage for each strategy. Key characteristics include:

* **Fallback Delegation**: Forwards unimplemented calls to the TokenizedStrategy via `fallback`.
* **Delegatecall Execution**: Executes shared logic in the context of the individual strategy’s storage.
* **Standardized Hooks**: Provides predefined hooks for implementing custom logic:
  * `_deployFunds`: Allocates funds for strategy deployment.
  * `_freeFunds`: Releases funds for withdrawals.
  * `_harvestAndReport`: Manages profit reporting and harvesting.

### Vault Storage Model

Yearn V3 centralizes strategy storage using the **BASE\_STRATEGY\_STORAGE** slot, which contains the `StrategyData` structure. This structure standardizes storage across all strategies and includes the following fields:

**StrategyData Structure**

1. **Share and Asset Accounting**:
   * `ERC20 asset`: Underlying token managed by the strategy.
   * `uint8 decimals`: Precision of the token.
   * `uint256 totalSupply`: Total number of shares issued.
   * `mapping balances`: Individual share balances.
   * `uint256 totalAssets`: Total assets held by the strategy.
2. **Profit Management**:
   * `uint256 profitUnlockingRate`: Unlock rate for profits (per second).
   * `uint96 fullProfitUnlockDate`: Target date for complete profit unlocking.
   * `uint32 profitMaxUnlockTime`: Maximum profit unlocking duration.
   * `uint16 performanceFee`: Percentage of performance fees.
   * `address performanceFeeRecipient`: Address receiving performance fees.
   * `uint96 lastReport`: Timestamp of the last report.
3. **Access Control**:
   * `address management`: Current management address.
   * `address pendingManagement`: Pending management address.
   * `address keeper`: Keeper address for routine operations.
   * `address emergencyAdmin`: Emergency administrator address.
4. **Status**:
   * `uint8 entered`: Reentrancy guard state.
   * `bool shutdown`: Emergency shutdown status.

Each **BaseStrategy**, including Term Strategy Vaults, maintains an isolated instance of this data structure in the fixed **BASE\_STRATEGY\_STORAGE** slot. Logic from the TokenizedStrategy interacts with this storage via `delegatecall`, ensuring modularity and isolation for all strategies.