Yield Boost - ETH fund flow
Overview​
The Linea Yield Boost system stakes LineaRollup funds on Ethereum L1 via Lido V3 stVaults to generate beacon chain rewards, which are reported to L2 for distribution. This document maps where ETH flows and which roles control each movement.
High-level architecture​
L1 ETH flow​
Yield reporting and L2 distribution​
Legend
- Solid line - actual fund movement (ETH/stETH transfer)
- Dashed line - function call or event (no funds move)
- Red - privileged operator
- Blue - permissionless
- Green - L2
Roles and fund movement permissions​
| Role | Held By | ETH Movement Authorized |
|---|---|---|
YIELD_PROVIDER_STAKING_ROLE | Automation Service | LineaRollup → YieldManager → StakingVault |
YIELD_PROVIDER_UNSTAKER_ROLE | Automation Service | Validators → StakingVault → YieldManager → LineaRollup |
YIELD_REPORTER_ROLE | Automation Service | Settles obligations from StakingVault (LST liabilities, protocol fees, operator fees); emits synthetic yield message to L2 |
STAKING_PAUSE_CONTROLLER_ROLE | Security Council | None (pauses/unpauses beacon deposits) |
OSSIFICATION_INITIATOR_ROLE | Security Council | Initiates full withdrawal of all staked funds |
OSSIFICATION_PROCESSOR_ROLE | Automation Service | Progressive withdrawal during ossification |
SET_YIELD_MANAGER_ROLE | Security Council | None (configuration) |
| Permissionless | Anyone | fund() donations; unstakePermissionless() + replenishWithdrawalReserve() during deficit |
Fund flow scenarios​
1. Staking​
Surplus ETH in LineaRollup (above minimum reserve) is routed to the StakingVault for beacon chain staking.
2. Yield reporting​
The Automation Service triggers yield reporting. Before the net surplus is relayed to L2, the YieldManager settles outstanding obligations.
No L1 ETH moves for the yield report itself - obligation payments (solid arrows) are the only L1 ETH transfers. The MessageSent event is synthetic: it relays the net surplus to L2 for distribution without bridging ETH.
3. Reserve replenishment - operator​
Two-phase process: first trigger beacon chain withdrawal, then route funds to LineaRollup once they arrive in the vault.
4. Permissionless flows​
When LineaRollup balance drops below the minimum reserve, anyone can trigger unstaking and reserve replenishment
unstakePermissionless() is capped to the remaining deficit minus available liquidity in the YieldManager and provider. replenishWithdrawalReserve() is similarly capped to the current deficit.
5. LST withdrawal - last resort​
When LineaRollup lacks sufficient ETH for a user withdrawal, stETH is minted against StakingVault collateral and sent directly to the user.
This creates an LST liability that accrues interest; the system prioritizes repaying it from subsequent fund flows and yield.
6. Ossification withdrawal​
Security Council initiates vault ossification; Automation Service progressively withdraws all funds.
Quick reference​
| Fund Movement | Source | Destination | Trigger | Role Required |
|---|---|---|---|---|
| Stake excess reserve | LineaRollup | StakingVault | Automation | YIELD_PROVIDER_STAKING_ROLE |
| Beacon chain deposit | StakingVault | Validators | Node Operator decision | Node Operator |
| Report yield to L2 | synthetic MessageSent event | L2YieldDistributor | Automation | YIELD_REPORTER_ROLE |
| Operator replenish reserve | StakingVault | LineaRollup | Reserve below target | YIELD_PROVIDER_UNSTAKER_ROLE |
| Permissionless unstake | Validators | StakingVault | Reserve below minimum | Permissionless |
| Permissionless replenish reserve | StakingVault | LineaRollup | Reserve below minimum | Permissionless |
| LST withdrawal | Lido Protocol (minted against StakingVault collateral) | User | Insufficient ETH | Permissionless (user) |
| Ossification withdrawal | StakingVault | LineaRollup | Security Council initiates | OSSIFICATION_INITIATOR_ROLE + OSSIFICATION_PROCESSOR_ROLE |
| Donation | External | LineaRollup / StakingVault | Voluntary | Permissionless |