Idle Tranche Strategy

[vany365]

Description: Idle Perpetual Yield Tranches Strategy for Yearn

Commit (hash):

Tag:

Repo: https://github.com/Idle-Finance/yearn-tranche-strategy

Scope: (List link to files)

• File.sol

Due Diligence: (attach link to due diligence document, see template here)

Additional References or Repo (Link to underlying protocols or relevant documents):

Deployed Contract (etherscan link):

Review Ongoing By:

• [ ] Dev 1
• [ ] Dev 2

Review Completed By:

• [ ] Dev 1
• [ ] Dev 2

[massun-onibakuchi]

Estimated APY, taking into account the effect of auto-compounding interest and harvests

Junior Tranche

some of apy are incorrect.

Senior Tranche

[dudesahn]

Spamming all mainnet strategies in review—please please consider checking ethereum baseFee prices for harvestTrigger similar to what I do here; and just in general planning around automating as much as you can with harvestTrigger:

    // check if the current baseFee is below our external target
    function isBaseFeeAcceptable() internal view returns (bool) {
        return
            IBaseFee(0xb5e1CAcB567d98faaDB60a1fD4820720141f064F)
                .isCurrentBaseFeeAcceptable();
    }

Happy to discuss if you have any questions 🙂

[saltyfacu]

@wavey and @tonkers will help here :)

[decaf-addict]

already in BaseStrategy, can be removed https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L33-L34

[decaf-addict]

remove, not used https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L103 https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L116

[decaf-addict]

opinion: leave this blank to allow gov to sweep any token

https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L526-L544

[massun-onibakuchi]

@tonkers-kuma

remove, not used

https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L103

https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L116

router is used to fetch asset price in ethToWant()

[massun-onibakuchi]

23996c2fbc3bf1cf5f0a928c2a2a788f9695360d

[decaf-addict]

Grouping all these comments together bc I'm reviewing on the plane w/o internet.

General: is the idea of this strategy to deploy a set of 2 contracts (junior + senior) together and have yearn manage the weight distribution? Do you have any tools better inform us on what to adjust to? What's the benefit of this tranche strategy if the depositor has to manage the balance of the weights themselves?

General: What kind of operation are the tranches doing under the hood to create yield? What's the risk profile in term of strategy and also exposure to other protocols?

can leave blank, use gas oracle pattern instead. https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L561-L586

remove: https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L752

use safemath https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L662

is the tranche token interest bearing? What about the gauge token? Looks like the amount could be of either type of token. Just making sure that there doesn't need to be a conversion here https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L642

could be wise to also build in some defensive codes here like Math.max(toWithdraw, stakedBal) https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L646

Will this revert if _trancheAmount isn't available to withdraw? https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L651 If yes, add check for max safe withdrawable amount https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L698

nit: inconsistent use of _ in several methods https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L708

stakedBal.add() not needed https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L340

Specify junior or senior https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L290

don't leave reward tokens and idle tokens behind https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L485

[bugduino]

Thanks for the review @tonkers-kuma. For the General part: You should rather select only one of the 2 tranches, according to your risk profile and that's it, Idle automatically 'split' the interest and redirects it to the 2 tranches according to the, dynamic, APR split ratio. Of course potentially one can also deposit in both tranches, using 2 instances of this strategy, and manage the ratio between the 2 according to any logic.

Funds deposited via tranches will get then redeposited in one of the lending provider that we support (currently Lido, Convex, Euler, Clearpool) and rewards harvested and reinvested for the underlying. All senior tranches, approved by the governance via snapshots, can also get some IDLE via Idle Gauges. Some tranches, may have also additional rewards distributed, via gauges Multireward contracts, eg for Lido tranche we distribute LDO proportionally to the TVL. Of course in case of hacks or any loss, senior holders will be the first to receive funds.

All tranche tokens are interest bearing tokens. Senior tranches deposited in a gauge will give back to the user a gauge-deposit token, we use LiquidityGaugeV3 from Curve. If the gauge also has rewards, like for Lido senior tranche, then the tranche token deposited in the gauge will start getting also these additional rewards automatically

(Btw the dynamic split, vs a fixed split ratio, will be the default for all tranches on our side in the next few days)

For the implementation comments I'll let @massun-onibakuchi add some more info

[massun-onibakuchi]

use gas oracle pattern instead.

what's gas oracle pattern?

[massun-onibakuchi]

Specify junior or senior

https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L290

tranche.name() returns somthinIdleCDO AA Tranche - wstETH (AA_wstETH) ,which contains Junior or Senior. AA Tranche means ~Junior tranche~ senior one.

[massun-onibakuchi]

Will this revert if _trancheAmount isn't available to withdraw? yearn-tranche-strategy/contracts/Strategy.sol](https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L651

https://github.com/Idle-Finance/yearn-tranche-strategy/commit/beb107efaa0f8c6090c102fa74e8878def9b51e3

If yes, add check for max safe withdrawable amount

no. _withdrawTranche() will not revert unless the strategy try to withdraw amount greater than actual balance

[massun-onibakuchi]

is the tranche token interest bearing? What about the gauge token? Looks like the amount could be of either type of token. Just making sure that there doesn't need to be a conversion here

tranche token is interest bearing token. same amount of gauge tokens are minted/ burned when users depositing/withdrawing their tranche to/from Gauge. a conversion rate between gauge token and tranche is always 1.

[massun-onibakuchi]

opinion: leave this blank to allow gov to sweep any token https://github.com/Idle-Finance/yearn-tranche-strategy/issues/5#issuecomment-1192263148

[bugduino]

Specify junior or senior

https://github.com/Idle-Finance/yearn-tranche-strategy/blob/beb107efaa0f8c6090c102fa74e8878def9b51e3/contracts/Strategy.sol#L290

tranche.name() returns somthinIdleCDO AA Tranche - wstETH (AA_wstETH) ,which contains Junior or Senior. AA Tranche means Junior tranche

To be clear, AA is the Senior tranche while BB is the junior one

[massun-onibakuchi]

sorrry,I made a mistake

[decaf-addict]

use gas oracle pattern instead.

what's gas oracle pattern?

one of the comments above by Dudesahn https://github.com/Idle-Finance/yearn-tranche-strategy/issues/3#issuecomment-1138055945

[decaf-addict]

comments left in PR https://github.com/Idle-Finance/yearn-tranche-strategy/pull/6#pullrequestreview-1067778406

[tapired]

did the reviews in other issues, LGTM

[0xValJohn]

Placing this issue on hold until we determine a way forward.

[bugduino]

@0xValJohn if you need more info let me know, we removed also gauges in the meantime so there are less steps involved in general. Not sure what was the blocker here