Hostasis enables users to deposit sDAI and automatically direct the accrued yield to fund their Swarm postage stamps for permanent decentralized hosting.

• Users deposit sDAI against a specific Swarm stampId.
• Each deposit tracks sDAIAmount, principalDAI, totalYieldClaimed, stampId, and depositTime.
• Yield is measured in wxDAI terms using SDAI.convertToAssets(1e18).
• harvest() is permissionless. It pays a harvester fee, allocates keeper fees, swaps the remaining wxDAI into BZZ, and opens a batch distribution window.
• processBatch(batchSize) is permissionless. It distributes BZZ across active users and pays the caller from the keeper fee pool.
• Harvests are serialized. A second harvest() is blocked until the current distribution finishes.
• While a distribution is active, deposit, depositWithPermit, topUp, topUpWithPermit, and withdraw are blocked so the harvest snapshot cannot be mutated mid-cycle.
• updateStampId() remains available so a user can correct a bad batch id before keepers process their entry.

The core contract is src/PostageYieldManagerUpgradeable.sol.

Important details:

• The contract is deployed behind a Transparent Proxy.
• SDAI is the savings token on Gnosis.
• DAI in the code is actually the wxDAI ERC-20 address on Gnosis.
• Swaps are done directly against a Uniswap V3-compatible BZZ/wxDAI pool.
• Swarm top-ups use topUp(bytes32 batchId, uint256 topupAmountPerChunk), so the contract converts each user's BZZ allocation into a per-chunk amount using the batch depth.

The main accounting structs are:

struct Deposit {
    uint256 sDAIAmount;
    uint256 principalDAI;
    uint256 totalYieldClaimed;
    bytes32 stampId;
    uint256 depositTime;
}

struct DistributionState {
    uint256 totalBZZ;
    uint256 cursor;
    uint256 totalYieldDAI;
    uint256 snapshotRate;
    uint256 snapshotTotalSDAI;
    bool active;
}

• deposit(uint256 sDAIAmount, bytes32 stampId)
• depositWithPermit(uint256 sDAIAmount, bytes32 stampId, uint256 deadline, uint8 v, bytes32 r, bytes32 s)

Each deposit stores the current wxDAI value as principalDAI. That is the basis used to prevent later depositors from inheriting earlier yield.

• topUp(uint256 depositIndex, uint256 sDAIAmount)
• topUpWithPermit(uint256 depositIndex, uint256 sDAIAmount, uint256 deadline, uint8 v, bytes32 r, bytes32 s)

Top-ups increase both sDAIAmount and principalDAI at the current exchange rate.

• withdraw(uint256 depositIndex, uint256 sDAIAmount)

Withdrawals return sDAI shares, not wxDAI. The contract reduces principalDAI proportionally to the amount withdrawn.

• previewYield() returns total contract yield in wxDAI.
• previewUserYield(address user, uint256 depositIndex) returns the current unrealized yield for one deposit.

harvest() does the following:

1. Reverts if a previous distribution is still active.
2. Computes total yield from totalSDAI and totalPrincipalDAI.
3. Converts that realized yield into sDAI shares and redeems them to wxDAI.
4. Pays the harvester fee to msg.sender.
5. Adds the keeper fee allocation to keeperFeePool.
6. Swaps the remaining wxDAI into BZZ.
7. Stores a distribution snapshot so keepers can process users in batches.

Important nuance: harvest reduces global totalSDAI immediately. Individual deposit balances are updated later during processBatch().

processBatch(uint256 batchSize) iterates across activeUsers from the current cursor:

• It computes each deposit's yield share using the harvest snapshot.
• It converts that yield share into a BZZ allocation.
• It converts the BZZ allocation into a per-chunk Swarm top-up based on batchDepth(stampId).
• It reduces each deposit's sDAIAmount by the realized yield shares consumed in that harvest.
• It pays the keeper a proportional share of keeperFeePool.

Distribution is based on yield earned, not raw sDAI balance. That matters when users entered at different exchange rates.

Defaults set in initialize():

• minYieldThreshold = 0.01 ether
• harvesterFeeBps = 50 (0.5%)
• keeperFeeBps = 100 (1%)

Owner controls:

• setBzzWxdaiPool(address)
• setMinYieldThreshold(uint256)
• setHarvesterFee(uint256) capped at 200 bps
• setKeeperFee(uint256) capped at 500 bps

External dependencies hardcoded in the deploy script:

• sDAI: 0xaf204776c7245bF4147c2612BF6e5972Ee483701
• wxDAI: 0xe91D153E0b41518A2Ce8Dd3D7944Fa863463a97d
• BZZ: 0xdBF3Ea6F5beE45c02255B2c26a16F300502F68da
• Swarm PostageStamp: 0x45a1502382541Cd610CC9068e88727426b696293
• BZZ/wxDAI pool: 0x7583b9C573FA4FB5Ea21C83454939c4Cf6aacBc3

Repo-configured frontend target:

• PostageYieldManager proxy: 0x3E4cc34e228841606DE7EEb5245Bc30cA979AF23

• src/: Solidity contracts and interfaces
• test/unit/: Foundry unit and invariant tests
• script/: deploy and upgrade scripts
• keeper/: Node-based harvester/keeper bot
• hostasis-frontend/: Next.js frontend

Build:

forge build

Run tests:

forge test

Deploy the proxy:

forge script script/DeployUpgradeable.s.sol --rpc-url gnosis --broadcast

Upgrade an existing proxy:

PROXY_ADDRESS=<proxy> forge script script/UpgradeContract.s.sol --rpc-url gnosis --broadcast

If the ABI changed, update the frontend copy:

./update-frontend-abi.sh

• harvest() is not owner-only. Any account can harvest and earn the configured harvester fee.
• processBatch() is not owner-only. Any account can process a batch and earn keeper fees.
• Small BZZ allocations can round down to zero if they are less than one token per chunk for a given Swarm batch depth.
• The system is not audited.

The current behavior is covered primarily by:

• test/unit/PostageYieldManager.t.sol
• test/unit/KeeperIncentives.t.sol
• test/unit/PostageYieldManagerInvariants.t.sol

These tests cover:

• principal accounting across deposits at different exchange rates
• permissionless harvest and batch processing
• keeper and harvester fee flows
• multi-harvest regression cases
• invariant checks around solvency and rounding dust

MIT