Strata

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High-Level Overview of the Protocol

The protocol is composed of two ERC-4626 Vaults (tranches): Junior (Jrt) and Senior (Srt). Both vaults are implemented as Meta Vaults:

• Each has a Base Asset.

• They can also accept additional tokens supported by the underlying Strategy.

  • Example: the Ethena Strategy uses USDe as the Base Asset and also accepts sUSDe.

All vault shares are denominated in the Base Asset. User actions (deposit, withdraw, etc.) are forwarded to the CDO contract (the core orchestrator).

The CDO contract has two major components:

1. Strategy
2. Accounting

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Strategy

The Strategy contract is responsible for asset management. It receives assets from the CDO, stakes them, and must be able to return them when requested.

At any point in time, the Strategy reports its total TVL (incl. yield).

When returning assets, the Strategy uses different mechanisms:

• Direct return: e.g. sUSDe can be returned instantly to an Srt user.
• ERC20 Cooldown: Strategy locks tokens in a cooldown contract. Tokens can be finalized/withdrawn after the cooldown period.
• Unstaking Cooldown: e.g. for USDe, the Strategy requests withdrawal from Ethena's sUSDe, which itself has a cooldown period.

Each withdrawal request is handled independently per user. New requests do not extend or affect earlier requests.

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Accounting

The Accounting contract performs pure calculations for:

• jrtTVL
• srtTVL

From these, each vault derives its ERC-4626 exchangeRate and totalAssets.

Update Cycle

On every protocol action (deposit, withdrawal), Accounting is updated:

1. Strategy reports current totalTVL at current block timestamp t1.

2. Accounting compares against the last saved totalTVL at t0.

3. Strategy Gain is calculated:

   gain = totalTVL(t1) - totalTVL(t0)
   

   (For sUSDe, this amount is always >= 0)

4. A portion of the gain may be redirected to reserveTVL (if the reserve percentage is set).

5. The remaining gain goes to Junior TVL.

6. Calculate Senior's desired gain and subtract from Junior's TVL.

Gain Splitting

• Senior Gain Desired (Target): Based on the Senior tranche's target index (APR target), last srtTVL and deltaT.

Two cases:

Case A: Strategy Gain >= Senior Gain Desired

• Seniors receive their full target.

• Juniors receive the remaining gain.

• So finally:

  jrtTVL + srtTVL + reserveTVL == totalTVL
  

Case B: Strategy Gain < Senior Gain Desired

• Any Senior APR shortfall is covered by the Junior tranche

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Deposit Flow (Example with Jrt)

1. Update Accounting

   • Refresh Strategy TVL and calculate gains for the period t0 → t1.
   • Adjust Junior/Senior TVLs according to Gain Splitting rules.

2. Calculate Shares (ERC-4626)

   • jrtTVL is the vault's totalAssets().
   • User's deposited assets are exchanged for shares proportional to current jrtTVL.

3. Forward Assets to Strategy

   • User's tokens are passed into the Strategy for staking.
   • jrtTVL is incremented accordingly.

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Withdrawals

Withdrawals follow the same process:

• First, Accounting updates TVLs at current block t1.
• Then, ERC-4626 totalAssets() is used to determine how many assets a user receives for redeeming shares.
• Strategy may return assets directly or via cooldown mechanisms, as described above.

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APRs Feed

The APR Feed contract provides dynamic parameters:

• APR Target (base rate)
• APR Base

Whenever these values change, the Feed updates the Accounting contract, which recalculates the Senior Target Index accordingly.

Test

npm i
npm run compile
# OR in watch mode
npm run watch

npm run test

# OR single file
npx atma test ./test/tranches/ERC4626.spec.ts

# OR single file in watch mode
npx atma test ./test/tranches/ERC4626.spec.ts --watch

Deploy

To localhost:

# start hh node
npm run node
# deploy/check unchanged

npm run deploy-local

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(c) 2025