BIP-36: Silo V3

Proposed: July 3, 2023

Status: Passed

Link: Snapshot

Proposer

Beanstalk Farms

Proposer Wallet: 0xf9d183af486a973b7921ceb5fdc9908d12aab440

Summary

Problem

Withdrawal Freeze Removal

Currently there is a Withdrawal Freeze that lasts from the time of Withdrawal until the end of the Season. This provides an unnecessarily complex UX as Farmers are forced to perform 2 on-chain actions at different times (Withdraw then Claim). For example, this limits the potential for using Deposits throughout DeFi via Pipeline as Deposits cannot atomically be swapped for the underlying. Furthermore, the supply overhang creates an economic inefficiency for Beanstalk and the lockup release at the same time creates an economic disadvantage for small Farmers when exiting the Silo.

Delayed Earned Bean Seigniorage

If the Withdrawal Freeze is removed with no changes to Earned Bean distribution, Beanstalk becomes susceptible to an attack where an account can Deposit whitelisted assets in the Silo, call gm and Withdraw the assets in the same transaction, gaining risk-free Bean seigniorage in the process.

Stems Upgrade

The Seeds per BDV reward for a whitelisted asset is static and can only be set upon whitelisting. This makes it such that (1) Seeds per BDV rewards cannot easily be updated via BIP and (2) no system for autonomously updating Seeds per BDV rewards can exist.

Indexing Deposits by Season results in scenarios where Farmers may forfeit Stalk when Converting from a whitelisted asset to another with a lower Seeds per BDV.

Seeds are implemented without decimals, limiting the economic flexibility of Silo incentives.

Currently Beanstalk does not have a gas efficient way to read the total Deposited BDV in the Silo. In a future Seed Gauge System, Beanstalk may need to calculate average Seeds per BDV across all Deposited assets.

Unripe Seed Parity at 0

Currently Beanstalk rewards 2 and 4 Seeds per BDV for urBEAN Deposits and urBEAN3CRV Deposits, respectively. There is a significant amount of Deposited urBEAN3CRV that could be Converted to repeg the Bean price. Beanstalk does not benefit from incentivizing Farmers to keep their Unripe assets in the Silo. Furthermore, the excessive accrual of Grown Stalk to Unripe asset holders during this extended period without Bean minting continues to make new Deposits less attractive.

ERC-1155 Deposits

Silo Deposits do not implement any standard interface, significantly limiting the composability of Bean's positive carry. Protocols such as Tractor, Depot, etc. need to implement Deposit specific functionality in order to support them. Protocols such as Seaport do not support Deposits.

Proposed Solution

Withdrawal Freeze Removal

Remove the Withdrawal Freeze entirely, allowing Farmers to Withdraw assets in the Silo directly to Circulating or Farm balances in a single transaction.

Specification

Delayed Earned Bean Seigniorage

Revise the distribution of Earned Beans such that they Vest after the Vesting Period after the gm function is called. Set the Vesting Period to 10 blocks.

In practice, this means that a Farmer who Mows their Grown Stalk during the Vesting Period will be credited with that Stalk when Earned Beans are distributed next.

Specification

Stems Upgrade

Introduce Stems for each token on the Deposit Whitelist, where Stems represent the Stalk Grown per BDV of Deposited value. This value starts at 0 at the time of Stem deployment (the Silo V3 BIP), or when a new token is added to the Deposit Whitelist.

Index Deposits based on Stems instead of by Season. A higher Stem count corresponds to an older Deposit. Storing Deposits based on Seasons does not allow for flexibility in Seeds per BDV values. With Stems, Seeds per BDV values can now be changed via governance and can have up to 6 decimals.

Store the total Deposited BDV of each whitelisted asset in the Silo. This enables future work on a Seed Gauge System that could need to calculate the average Seeds per BDV across all Deposited assets.

Storing Deposits based on Stems enables the cleanup of the Silo V1 and V2 storage systems into a single storage method that supports ERC-1155s. This requires a migration function (mowAndMigrate), in which Farmers submit all of their Deposits and the function that verifies their existence, removes them from the old storage slots, and migrates them into the Stem-based slots with ERC-1155 support.

A gas-saving migration function (mowAndMigrateNoDeposits) is available for accounts with no current Deposits.

As a result of the Stems migration, Farmers can now mow their Grown Stalk for each individual whitelisted asset. mowMultiple is added to allow Farmers to Mow their Grown Stalk for multiple whitelisted assets at once.

There are no penalties for waiting to migrate from Silo V2 (or V1) to Silo V3, but an account must be migrated in order to interact with the Silo again after the commitment of the Silo V3 BIP.

Specification

Unripe Seed Parity at 0

Set the Seeds per BDV for both urBEAN and urBEAN3CRV to 0.

The Beanstalk DAO expressed a preference for setting the Unripe Seeds per BDV rewards to be equal in Temp-Check-1, and specifically expressed a preference for them both being set to 0 in Temp-Check-2.

ERC-1155 Deposits

Implement Silo Deposits using the ERC-1155 standard. ERC-1155s support an id and a value, matching the semi-fungible nature of Silo Deposits wherein they are non-fungible across Stems and fungible within the same number of Stems.

The ERC-20 and ERC-721 standards would not suffice for Silo Deposits:

ERC-1155 tokens will be distributed to Farmers upon mowAndMigrate.

Specification

Technical Rationale

Withdrawal Freeze Removal

Adding the ability to send Withdrawn assets directly to the Farmer's Farm or Circulating balance without the need for a separate transaction reduces the friction of interacting with Beanstalk.

Introducing a LegacyClaimWithdrawalFacet facilitates backwards compatibility for Farmers with unclaimed Withdrawals at the time of this upgrade.

Stems Upgrade

Implementing Stems allows for Seeds per BDV to be changed via governance and set with greater precision, improving the economic flexibility of Silo incentives.

Providing a way for Beanstalk to calculate the average Seeds per BDV across all Deposited assets in a gas-efficient manner can be used to facilitate a future Seed Gauge System.

Allowing Farmers to mow or mowMultiple with distinct whitelisted assets increases the customizability of interacting with the Silo.

ERC-1155 Deposits

Implementing Silo Deposits as ERC-1155 tokens improves the composability of Beanstalk.

Economic Rationale

Withdrawal Freeze Removal

Improving the composability of Beanstalk and reducing the number of separate transactions required to interact with it improves the user experience and utility of Beanstalk and Beans.

Delayed Earned Bean Seigniorage

Removing the Withdrawal Freeze with no changes to Earned Bean distribution would create the opportunity to receive Bean seigniorage without taking on any exposure to the Bean price. Implementing a vesting period for Earned Beans mitigates this attack vector. In addition, a vesting period requires any related multi-block MEV attack to sustain the attack over at least that many blocks.

Stems Upgrade

Improving the efficiency of the Silo and customizability of Seeds per BDV rewards improves the utility of Beanstalk and Beans.

Eliminating situations where Stalk is unnecessarily forfeited during Conversions reduces the friction of interacting with Beanstalk.

Unripe Seed Parity at 0

There is an incentive not to Convert urBEAN3CRV to urBEAN given the loss of Seeds. Unripe Seed Parity reduces the incentive not to Convert urBEAN3CRV to urBEAN dramatically. Given that the potential sellable Beans to due to the Chop Penalty is so small compared to the liquidity in the pool, Beanstalk should incentivize more Converts from urBEAN3CRV to urBEAN. This should significantly contribute to peg maintenance in the short term.

There is no need to use Seeds per BDV rewards to create opportunity cost associated with Withdrawing and Redepositing Unripe assets. Excessive Grown Stalk per BDV Deposited associated with Unripe assets is likely hurting Beanstalk's ability to attract new Depositors.

ERC-1155 Deposits

The positive carry of Beans is generally not accessible in DeFi given the lack of composability with Silo Deposits. Improving the composability of Silo Deposits by tokenizing them as ERC-1155s improves the user experience and utility of Beanstalk and Beans.

Contract Changes

Initialization Contract

The init function on the following InitBipNewSilo contract is called:

Silo Facet

The following SiloFacet is removed from Beanstalk:

The following SiloFacet is added to Beanstalk:

SiloFacet Function Changes

Name Selector Action Type New Functionality
balanceOf 0x00fdd58e Add View ✓
balanceOfBatch 0x4e1273f4 Add View ✓
balanceOfEarnedBeans 0x3e465a2e Replace View
balanceOfEarnedSeeds 0x602aa123 Remove View
balanceOfEarnedStalk 0x341b94d5 Replace View
balanceOfGrownStalk 0x249564aa Remove View ✓
balanceOfGrownStalk 0x8915ba24 Add View ✓
balanceOfPlenty 0x896651e8 Replace View ✓
balanceOfRainRoots 0x69fbad94 Replace View
balanceOfRoots 0xba39dc02 Replace View
balanceOfSeeds 0x4916bc72 Remove View
balanceOfSop 0xa7bf680f Replace View
balanceOfStalk 0x8eeae310 Replace View
claimPlenty 0x45947ba9 Replace Call
deposit 0xf19ed6be Replace Call
getDeposit 0x8a6a7eb4 Remove View
getDeposit 0x61449212 Add View
getDepositId 0x98f2b8ad Add View ✓
getSeedsPerToken 0x9f9962e4 Add View ✓
getTotalDeposited 0x0c9c31bd Replace View
getTotalDepositedBDV 0x9d6a924e Add View ✓
grownStalkForDeposit 0x3a1b0606 Add View ✓
inVestingPeriod 0x0b2939d1 Add View ✓
lastSeasonOfPlenty 0xbe6547d2 Replace View
lastUpdate 0xcb03fb1e Replace View
migrationNeeded 0xc38b3c18 Add View ✓
update 0x1c1b8772 Remove Call
mow 0x150d5173 Add Call ✓
mowMultiple 0x7d44f5bb Add Call ✓
plant 0x779b3c5c Replace Call
safeBatchTransferFrom 0x2eb2c2d6 Add Call ✓
safeTransferFrom 0xf242432a Add Call ✓
seasonToStem 0x896ab1c6 Add View ✓
stemStartSeason 0xbc771977 Add View ✓
stemTipForToken 0xabed2d41 Add View ✓
tokenSettings 0xe923e8d4 Replace View
totalEarnedBeans 0xfd9de166 Replace View
totalRoots 0x46544166 Replace View
totalSeeds 0xd8bd0d9d Remove View
totalStalk 0x7b52fadf Replace View
transferDeposit 0x9e32d261 Remove Call ✓
transferDeposit 0x081d77ba Add Call ✓
transferDeposits 0x0d2615b1 Remove Call ✓
transferDeposits 0xc56411f6 Add Call ✓
withdrawDeposit 0x7af9a0ce Remove Call
withdrawDeposit 0xe348f82b Add Call ✓
withdrawDeposits 0xb189d9c8 Remove Call
withdrawDeposits 0x27e047f1 Add Call ✓
withdrawFreeze 0x55926690 Remove View

SiloFacet Event Changes

Name Change
AddDeposit Updated to reflect new Deposit accounting system
AddWithdrawal Removed
RemoveDeposit Updated to reflect new Deposit accounting system
RemoveDeposits Updated to reflect new Deposit accounting system
SeedsBalanceChanged Removed
TransferBatch Emitted when multiple Deposits are removed or transferred
TransferSingle Emitted when a Deposit is created, removed or transferred

Legacy Claim Withdrawal Facet

The following LegacyClaimWithdrawalFacet is added to Beanstalk:

LegacyClaimWithdrawalFacet Function Changes

Name Selector Action Type New Functionality
claimWithdrawal 0x488e94dc Replace Call
claimWithdrawals 0x764a9874 Replace Call
getTotalWithdrawn 0xb1c7a20f Replace View
getWithdrawal 0xe23c96a4 Replace View

LegacyClaimWithdrawalFacet Event Changes

None.

Season Facet

The following SeasonFacet is removed from Beanstalk:

The following SeasonFacet is added to Beanstalk:

SeasonFacet Function Changes

Name Selector Action Type New Functionality
abovePeg 0x2a27c499 Replace View
gm 0x64ee4b80 Replace Call
paused 0x5c975abb Replace View
plentyPerRoot 0xe60d7a83 Replace View
poolDeltaB 0x471bcdbe Replace View
rain 0x43def26e Replace View
season 0xc50b0fb0 Replace View
seasonTime 0xca7b7d7b Replace View
sunrise 0xfc06d2a6 Replace Call
sunriseBlock 0x3b2ecb70 Replace View
time 0x16ada547 Replace View
totalDeltaB 0x06c499d8 Replace View
weather 0x686b6159 Replace View

SeasonFacet Event Changes

None.

Migration Facet

The following MigrationFacet is added to Beanstalk:

MigrationFacet Function Changes

Name Selector Action Type New Functionality
balanceOfGrownStalkUpToStemsDeployment 0x505f43ea Add View ✓
balanceOfLegacySeeds 0x1be2cfd8 Add View ✓
getDepositLegacy 0xa9be1acb Add View ✓
mowAndMigrate 0x1f4f3d55 Add Call ✓
mowAndMigrateNoDeposits 0xaed942e9 Add Call ✓

MigrationFacet Event Changes

None.

Approval Facet

The following ApprovalFacet is added to Beanstalk:

ApprovalFacet Function Changes

Name Selector Action Type New Functionality
approveDeposit 0x1302afc2 Replace Call
decreaseDepositAllowance 0xd9ee1269 Replace Call
depositAllowance 0x2a6a8ef5 Replace View
depositPermitDomainSeparator 0x8966e0ff Replace View
depositPermitNonces 0x843bc425 Replace View
increaseDepositAllowance 0x5793e485 Replace Call
isApprovedForAll 0xe985e9c5 Add View ✓
permitDeposit 0x120b5702 Replace Call
permitDeposits 0xd5770dc7 Replace Call
setApprovalForAll 0xa22cb465 Add Call ✓

ApprovalFacet Event Changes

Name Change
ApprovalForAll New event

Convert Facet

The following ConvertFacet is removed from Beanstalk:

The following ConvertFacet is added to Beanstalk:

ConvertFacet Function Changes

Name Selector Action Type New Functionality
convert 0x3b2a1b28 Remove Call
convert 0xb362a6e8 Add Call ✓
enrootDeposit 0xd5d2ea8c Remove Call
enrootDeposit 0x0b58f073 Add Call ✓
enrootDeposits 0x83b9e85d Remove Call
enrootDeposits 0x88fcd169 Add Call ✓
getAmountOut 0x4aa06652 Replace View
getMaxAmountIn 0x24dd285c Replace View

ConvertFacet Event Changes

Name Change
RemoveDeposit New event
RemoveDeposits Updated to reflect new Deposit accounting system
TransferBatch New event

Whitelist Facet

The following WhitelistFacet is removed from Beanstalk:

The following WhitelistFacet is added to Beanstalk:

WhitelistFacet Function Changes

Name Selector Action Type New Functionality
dewhitelistToken 0x86b40a1b Replace Call
updateStalkPerBdvPerSeasonForToken 0xf18d9ed0 Add Call ✓
whitelistToken 0xd8a6aafe Replace Call ✓

WhitelistFacet Event Changes

Name Change
UpdatedStalkPerBdvPerSeason New event
WhitelistToken Updated to reflect new Deposit accounting system

Metadata Facet

The following MetadataFacet is added to Beanstalk:

MetadataFacet Function Changes

Name Selector Action Type New Functionality
imageURI 0x8f742d16 Add View ✓
uri 0x0e89341c Add View ✓

MetadataFacet Event Changes

None.

Token Facet

The following TokenFacet(s) are being removed from Beanstalk:

The following TokenFacet is added to Beanstalk:

TokenFacet Function Changes

Name Selector Action Type New Functionality
approveToken 0xda3e3397 Replace Call
decreaseTokenAllowance 0x0bc33ce4 Replace Call
getAllBalance 0xfdb28811 Replace View
getAllBalances 0xb6fc38f9 Replace View
getBalance 0xd4fac45d Replace View
getBalances 0x6a385ae9 Replace View
getExternalBalance 0x4667fa3d Replace View
getExternalBalances 0xc3714723 Replace View
getInternalBalance 0x8a65d2e0 Replace View
getInternalBalances 0xa98edb17 Replace View
increaseTokenAllowance 0xb39062e6 Replace Call
onERC1155BatchReceived 0xbc197c81 Add View ✓
onERC1155Received 0xf23a6e61 Add View ✓
permitToken 0x7c516e94 Replace Call
tokenAllowance 0x8e8758d8 Replace View
tokenPermitDomainSeparator 0x1f351f6a Replace View
tokenPermitNonces 0x4edcab2d Replace View
transferInternalTokenFrom 0xd3f4ec6f Replace Call
transferToken 0x6204aa43 Replace Call
unwrapEth 0xbd32fac3 Replace Call
wrapEth 0x1c059365 Replace Call

TokenFacet Event Changes

None.

Beans Minted

None.

Audit

The commit hash of this BIP is 9f286e1f1b1e67bc40d35aaf4b16e5c6d83ebdd9.

Halborn has performed an audit of this BIP up to commit hash 24bf3d33355f516648b02780b4b232181afde200. You can view the final audit report here.

Changes between the two commits:

Effective

Immediately upon commitment.