smart-contracts/backlog/tasks/task-2 - Port-RiskTrancheManager-to-Solidity.md

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

Description

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

Acceptance Criteria

• #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