Yield Boost technical overview

status

🚧 Yield Boost is not yet live. This documentation describes the intended design.

What is it?

Linea Yield Boost is a protocol-level mechanism implemented on the Public network that automatically stakes a proportion of the ETH held in the LineaRollup and distributes the staking rewards back into the Linea ecosystem. When a user bridges ETH from Ethereum (L1) to Linea (L2) via the LineaRollup, these assets may be programmatically deposited into a dedicated Lido v3 stVault on Ethereum Mainnet. The resulting staking rewards are distributed back into the Linea ecosystem to incentivize liquidity providers (LPs) and support DeFi protocols.

This page maps the high-level architecture of Yield Boost, including where ETH flows and which roles control each movement.

High-level architecture

LineaRollup deposits on the L1 are staked via a Lido V3 stVault, known as the `StakingVault, to generate beacon chain rewards, which are distributed on Linea (L2). The following is a breakdown of the major components and flows of the Yield Boost system.

Key participants

• User: Interacts with the system by bridging ETH to and from Linea via the LineaRollup.
• Security Council: A multisig composed of Linea and external industry members responsible for safeguarding the network, managing incidents, and mitigating operational risks.
• Lido Oracle Committee: A 5-of-9 committee of independent operators who monitor validator states and submit regular, audited reports to Lido's smart contracts.
• Node operator: The Linea-assigned entity bound to the agreed deposit trigger to stake ETH from the StakingVault, and validate the beacon chain to earn rewards.
• NativeYieldAutomationService: An offchain service that executes onchain routine operations, including yield reporting, rebalancing the liquidity buffer, and settling system obligations. It operates in a default YIELD_REPORTING mode and switches to an OSSIFICATION_PROCESSOR mode if the Security Council initiates the ossification process.
• LidoUpgradeMonitor: An offchain service that monitors Lido's onchain governance for contract upgrade proposals and alerts the Security Council.

L1 ETH flow

When a user deposits ETH from Ethereum Mainnet (L1) into the LineaRollup contract to use it on Linea (L2), that ETH remains on the L1 and may be staked on Ethereum’s beacon chain to earn rewards. The following components manage how that ETH moves from the LineaRollup into the StakingVault how rewards are handled, and how the ETH is returned to the user on the L1 when they withdraw it from Linea.

• LineaRollup: L1 bridge contract and message service that holds user-deposited ETH collateral and serves as the accounting anchor for Yield Boost.
• YieldManager: L1 contract that moves ETH between the LineaRollup and the StakingVault, and calculates net yield after fees and liabilities.
• StakingVault: Lido V3 stVault that holds ETH awaiting beacon chain staking; all validator withdrawals return here before moving back to the LineaRollup.
• Beacon chain: Ethereum's proof-of-stake consensus layer where node operators lock/stake ETH to secure the network and earn staking rewards.
• Node operator: Selected operators run beacon chain validators on behalf of Linea.
• Automation service: Offchain service that triggers routine onchain operations: moving ETH to/from staking, topping up reserves, and reporting yield.

The following diagram details the flow:

The node operator's deposit trigger is part of an automated process whose logic is agreed beforehand. The node operator is only responsible for running the validator infrastructure.

Yield reporting and L2 distribution

The yield earned from the beacon chain is transferred to the L2 for distribution. The following components are involved:

• YieldManager: L1 accounting and settlement contract (see L1 Eth flow).
• Dashboard: Lido V3 management layer around the StakingVault; handles fee accounting and deposit/withdrawal operations.
• Lido: Third-party staking protocol that provides the StakingVault and dashboard infrastructure used by Yield Boost.
• Fee recipient: Address that collects the staking rewards earned by the node operator.
• Security Council: Linea governance multisig (see Key participants).
• L2MessageService: L2 contract that receives messages from L1 and unlocks the corresponding ETH on L2.
• L2YieldDistributor: Distributes L2 unlocked ETH staking rewards to designated recipients.
• LineaRollup: see above.

The following steps and diagram detail the flow:

1. The automation service triggers a yield report on the YieldManager.
2. The YieldManager reads the vault's totalValue from the dashboard. This value—the sum of beacon chain stake and vault balance—is updated daily by the Lido Oracle Committee.
3. Yield is the difference between the current totalValue and the last stored checkpoint, minus outstanding obligations.
4. If the StakingVault has sufficient funds, the YieldManager settles obligations: stETH borrow liabilities and protocol fees go to Lido, and operator fees go to the node operator's fee recipient. If funds are insufficient, settlement is skipped and obligations carry forward.
5. The YieldManager reports the remaining net yield to the LineaRollup.
6. The LineaRollup emits a synthetic MessageSent event. The L2MessageService picks it up and unlocks the corresponding ETH on L2.
7. The L2YieldDistributor sends the unlocked ETH to designated recipients.

Legend

• Solid line: Fund movement (ETH/stETH transfer)
• Dashed line: Function call or event (no funds move)
• Red: Privileged operator
• Blue: Permissionless
• Green: L2

Roles and permissions

The Yield Boost system is governed by a set of roles and permissions that control the flow of funds and the operations of the system. The following roles and permissions are defined:

Role	Held by	Permissions
YIELD_PROVIDER_STAKING_ROLE	Automation Service	Rebalance excess ETH from the LineaRollup into the StakingVault
YIELD_PROVIDER_UNSTAKER_ROLE	Automation Service	Rebalance ETH back from node operators into the LineaRollup
YIELD_REPORTER_ROLE	Automation Service	Trigger yield reporting, which may involve payment of fees and liabilities from staking rewards
STAKING_PAUSE_CONTROLLER_ROLE	Security Council	Pause or resume node operator deposits (no ETH movement)
OSSIFICATION_INITIATOR_ROLE	Security Council	Begin permanent shutdown of the staking vault; Lido may require fee settlement before proceeding
OSSIFICATION_PROCESSOR_ROLE	Automation Service	Finalize vault ossification; Lido may require fee settlement before proceeding
SET_YIELD_MANAGER_ROLE	Security Council	Configure which YieldManager contract the LineaRollup uses (no ETH movement)
Permissionless	Anyone	Donate ETH to the LineaRollup or vault; trigger unstaking and reserve top-up when the LineaRollup balance is too low

Fund flows

Each scenario below traces a specific ETH movement end-to-end, showing the contracts involved and the role that triggers it.

1. Staking (routine) — the Automation Service rebalances surplus ETH from the LineaRollup into the StakingVault for validator staking.
2. Reserve replenishment (routine) — the Automation Service rebalances ETH back from validators into the LineaRollup when the withdrawal reserve runs low.
3. Yield reporting (routine) — earned rewards are calculated, obligations settled, and net yield relayed to L2.
4. Permissionless flows (fallback) — anyone can trigger unstaking and replenishment when the reserve drops below minimum.
5. LST withdrawal (last resort) — if the LineaRollup does not control enough ETH to fulfill a user's withdrawal, the user can claim stETH instead.
6. Ossification withdrawal (terminal) — all staked funds are progressively withdrawn after the Security Council ossifies the vault.

1. Staking

Surplus ETH in the LineaRollup (above the minimum reserve) is routed to the StakingVault for beacon chain staking.

2. Reserve replenishment

Replenishing the withdrawal reserve is a two-phase process: first the beacon chain withdrawal is triggered, then funds are routed back to the LineaRollup once they arrive in the vault.

3. Yield reporting

The Automation Service triggers yield reporting. Before the net surplus is relayed to Linea, the YieldManager settles outstanding obligations.

No ETH is bridged during yield reporting. The MessageSent event is synthetic: it tells Linea how much new yield is available without actually bridging any ETH.

Staking rewards grow the L1 collateral by the same amount that the L2 mints, so the system stays fully collateralized.

4. Permissionless flows

When the LineaRollup balance drops below the minimum reserve, anyone can trigger the YieldManager to initiate 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

If the LineaRollup lacks sufficient ETH to fulfill a withdrawal, the withdrawal recipient can explicitly request an LST withdrawal. In this case, stETH is minted against the StakingVault collateral and sent to the same address designated to receive the withdrawal. This provides a last-resort mechanism.

This creates an LST liability that accrues interest; the system prioritizes repaying it from subsequent fund flows and yield.

6. Ossification withdrawal

Ossification permanently locks the StakingVault implementation, opting out of future Lido upgrades. Ossification is initiated by the Security Council; the Automation Service then progressively withdraws all staked funds back to the LineaRollup.

Risk mitigation

The Yield Boost system is designed to be resilient to various risks, including:

• Slashing
• Withdrawal delay

Slashing

If a validator makes conflicting attestations or block proposals, they may have their staked ETH confiscated, and the staking rewards lost. This is known as slashing, and is a general risk associated with the validator role.

While the risk of slashing is rare (only 0.04% of all Ethereum validators have ever been slashed, and the slashed amounts are on average less than .001% of that validator's staked ETH), the Yield Boost system has the following mitigations in place:

• Node operators will only be selected for participation in the Yield Boost system if they have never been slashed. Selected node operators must also have a diverse infrastructure with more than 99.9% uptime, safeguards to prevent double-signing, and world-class security practices.
• 20% of node operator validator rewards will be retained for a year to create an insurance fund to cover slashing events. If the Yield Boost system is impacted by a slashing event it will be eligible to access this fund.

Withdrawal delay

In certain market conditions, such as a sharp increase in the demand for bridging ETH to Ethereum, the withdrawal reserve may be depleted. This can cause a delay in the withdrawal of ETH from Linea back to Ethereum.

The Yield Boost system has the following mitigations in place:

• The withdrawal reserve is maintained at a minimum of 40% of the Total Value Staked (TVS).
• The Automation Service will trigger a rebalancing of funds to replenish the withdrawal reserve after a withdrawal transaction is initiated.
• In the unlikely event that the withdrawal reserve is depleted, users can trigger unstaking to replenish the withdrawal reserve.
• As a last resort, users can withdraw their funds as stETH rather than ETH.

Quick reference

Fund movement	Source	Destination	Trigger	Role required
Stake excess reserve	LineaRollup	StakingVault	Automation Service	YIELD_PROVIDER_STAKING_ROLE
Beacon chain deposit	StakingVault	Node operators	Node Operator decision	Node Operator
Report yield to L2	synthetic MessageSent event	L2YieldDistributor	Automation Service	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 for user withdrawal	Permissionless (user)
Ossification withdrawal	StakingVault	LineaRollup	Security Council initiates	OSSIFICATION_INITIATOR_ROLE + OSSIFICATION_PROCESSOR_ROLE
Donation	External	LineaRollup / StakingVault	Voluntary	Permissionless

Next steps

See the Yield Boost overview page for a more general overview of Yield Boost, including the user experience and withdrawal resilience strategy.

See the Security Council record page for a record of the Security Council transaction implementing this protocol.