Senior and Junior tranches
How an Akashi Invest vault splits one pool of USDC into a protected tranche and a first-loss tranche.
An Akashi Invest vault takes USDC, invests it across several Solana venues, and books the result into two tranches. Each tranche has its own SPL share token, so a vault has two share mints. Shares are transferable.
| Senior | Junior | |
|---|---|---|
| Losses | Absorbed after Junior is exhausted | Absorbed first |
| Yield | A share of gains, minus a premium paid to Junior | The rest of the gains, including Senior's premium |
| Withdrawal | Small delay (0–1 h, set per vault) | Notice period; completes within 24 h unless the coverage floor holds it |
Coverage
Coverage is the Junior share of the vault: Junior value / (Senior value + Junior value). It is the cushion standing in front of Senior. Each vault fixes a minimum coverage at creation:
- a Senior deposit is refused if it would push coverage below the minimum;
- a Junior withdrawal is only funded up to the amount that keeps coverage at or above the minimum.
Example from the design: at 700,000 Senior / 300,000 Junior with a 20 % floor, at most 500,000 more Senior can enter, and at most 125,000 of Junior can leave.
How gains are split
Gains are first shared pro rata, then Senior pays Junior a premium from its part. The premium follows a curve set at creation: the thinner the coverage, the more Senior pays for it.
Worked example: Senior 700,000, Junior 300,000 (coverage 30 %, premium 30 %), net gain 10,000.
- Senior receives
10,000 × 0.7 × (1 − 0.3) = 4,900, a 0.70 % return for the period. - Junior receives
5,100, a 1.70 % return for the period.
How losses are taken
A loss comes out of Junior first. Only if Junior is wiped out does Senior lose value. A small loss that stays within Junior is an ordinary bad period; a larger one, or any loss that reaches Senior, puts the vault into a recovery state.
Share prices
Each tranche's share price is its booked value divided by its share supply (with small virtual offsets so the first share is priced at exactly 1.0). Withdrawals are priced when they are funded, not when they are requested: shares in the queue keep earning, or absorbing losses, until then.
What the devnet version covers
The deployed program implements the core path: vault creation, Senior/Junior shares, USDC deposits, allocation by the executor, P&L booking, and request → fund → claim withdrawals. Governance timelocks, guardian actions, incident handling and real protocol adapters are designed but not implemented yet.