Mi Tanda — Contracts

On-chain ROSCA (rotating savings club) dApp targeting Arbitrum One and Base. Mi Tanda brings Latin America's tanda savings tradition onchain with built-in defaulter insurance, automatic NFT receipts, and rotating artist/sponsor collections.

Architecture

Six contracts:

• MitandaErrors.sol — single source of truth for all custom errors
• TandaManager.sol — singleton factory: token allowlist, VRF orchestrator, fee config, sponsored collection registry
• Tanda.sol — per-tanda state machine, deployed as EIP-1167 clones from a single implementation
• MitandaPassNFT.sol — soulbound proof-of-membership (EIP-5192)
• MitandaCompletionNFT.sol — soulbound completion badge, stackable for reputation
• MitandaReceiptNFT.sol — transferable payout receipt with frozen-at-mint sponsored art

Plus src/interfaces/ITanda.sol for clone-safe Manager → Tanda calls.

Key features

• Insurance model: 10% premium per cycle, refunded to honest finishers, forfeited by defaulters and split among the honest
• Sponsored collections: rotating slot for artists/brands; receipts mint with the active collection's art
• Private tandas: EIP-712 signed invite tickets for friend-group tandas with Privy onboarding
• VRF v2.5: Chainlink-randomized payout order
• Pull payments: all credits land in pendingWithdrawals, claimed via withdraw()
• Custom errors throughout: zero require-strings

Status

In active development for hackathon submission. Tests and deploy scripts pending.

Build

forge build

See CLAUDE.md for full architecture documentation.