---
id: TASK-2
title: Port RiskTrancheManager to Solidity
status: To Do
assignee: []
created_date: '2026-04-03 21:38'
labels:
  - solidity
  - core
  - risk
dependencies:
  - TASK-1
references:
  - /home/jeffe/Github/myco-bonding-curve/src/primitives/risk_tranching.py
  - /home/jeffe/Github/myco-bonding-curve/param_sweep_v2.csv
priority: high
---

## Description

<!-- SECTION:DESCRIPTION:BEGIN -->
Translate src/primitives/risk_tranching.py to Solidity.

Core functions to implement:
- deposit_collateral() — accept ERC-20 collateral into system
- mint_tranche(tier, amount) — mint Senior/Mez/Junior tranche tokens
- redeem_tranche(tier, amount) — burn tranche tokens, return collateral
- distribute_yield(amount) — waterfall: Senior target first → Mez → Junior residual
- apply_loss(amount) — reverse waterfall: Junior absorbs first → Mez → Senior
- apply_collateral_change(new_total) — route gains/losses through proper waterfalls
- check_liquidation() — flag tranches below min CR
- rebalance_collateral() — redistribute backing across tranches

Key design decisions:
- Each tranche is a separate ERC-20 (myUSD-S, myUSD-M, $MYCO-J)
- Fixed-point math via WAD (1e18) — no floating point
- Parameter sweep results: optimal SR=1.5, MZ=1.2 for medium vol
- Storage: TrancheState struct per tier, total_collateral, cumulative yield/loss tracking
- Access control: only authorized contracts (bonding curve, CCIP receiver) can call state-changing functions
<!-- SECTION:DESCRIPTION:END -->

## Acceptance Criteria
<!-- AC:BEGIN -->
- [ ] #1 Senior/Mez/Junior tranche minting respects collateral ratios
- [ ] #2 Yield waterfall distributes Senior-first correctly
- [ ] #3 Loss absorption follows Junior-first correctly
- [ ] #4 Liquidation flags trigger at correct CR thresholds
- [ ] #5 100+ Foundry fuzz tests pass
- [ ] #6 Gas benchmarks documented
<!-- AC:END -->