smart-contracts/backlog/docs/402_CRDT_CrossChain_Fiat_Research.md

# 402 / CRDT Tokens / Cross-Chain / Fiat Integration Research

## 1. HTTP 402 Payment Required Protocol

### x402 (Coinbase/Cloudflare) — EVM + Stablecoin Rail

x402 is the EVM-native micropayment protocol using the HTTP 402 status code. Launched May 2025, V2 in September 2025.

**How it works:**
1. Client requests paid resource
2. Server returns `HTTP 402` with payment details (amount, token, chain, recipient)
3. Client signs an EIP-3009 `transferWithAuthorization` (gasless for USDC/EURC) or Permit2 for any ERC-20
4. Client re-sends with payment proof in header
5. Facilitator settles on-chain; server delivers resource

**Key details:**
- Canonical proxy: `0x402085c248EeA27D92E8b30b2C58ed07f9E20001` (same address on all chains via CREATE2)
- Chains: Base, Base Sepolia, Polygon
- USDC on Base: `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`
- Any ERC-20 via Permit2 (`x402ExactPermit2Proxy`)
- 1,000 tx/month free tier on hosted facilitator
- 100M+ payments processed, $35M+ value by late 2025
- SDK: `@x402/core`, `@x402/evm`, `@x402/express`, `@x402/next`, `@x402/fetch`, `@x402/paywall`
- Docs: https://docs.cdp.coinbase.com/x402/welcome
- Spec: https://github.com/coinbase/x402

### L402 (Lightning Labs) — Bitcoin Lightning Rail

L402 uses Lightning Network invoices + macaroon bearer credentials.

- `WWW-Authenticate: L402 token="<macaroon>", invoice="<bolt11>"`
- Client pays invoice, gets preimage, sends `Authorization: L402 <base64(macaroon:preimage)>`
- Stateless HMAC verification — no database lookup
- Macaroon caveats for rate limits, expiry, service tiers
- Cloudflare processing 1B+ 402 responses/day
- Docs: https://docs.lightning.engineering/the-lightning-network/l402

### Community Token Use Cases
- **API metering**: Pay per request for community data APIs, AI inference
- **Content paywalls**: `@x402/paywall` for token-gated content
- **Agent-to-agent commerce**: AI agents pay with community tokens via Permit2
- **Revenue routing**: Custom facilitator routes fees to community treasury

### No L402↔EVM bridge exists — choose one rail per use case.

---

## 2. CRDT Tokens

### Status: Research Only — No Production Implementations

CRDTs (Conflict-free Replicated Data Types) allow concurrent, independent updates across replicas that automatically converge without coordination.

### UAT20 — Most Developed Proposal
- arXiv Feb 2025: https://arxiv.org/abs/2502.08919
- Solves: Liquidity fragmentation across rollups (USDC on Arbitrum ≠ USDC on Optimism)
- Each rollup holds a CRDT replica of unified user balance
- Transfers are local operations, periodically broadcast to L1 and propagated
- Conflict resolution via two-phase commit (reject one concurrent spend)
- Status: **Preprint only, not implemented**

### Other Academic Work
- **FabricCRDT**: CRDT integration for Hyperledger Fabric (permissioned chains)
- **OrderlessChain**: CRDT-based BFT blockchain eliminating global ordering

### Relationship to Existing Tech
| | State Channels | CRDT Tokens | Optimistic Rollups |
|---|---|---|---|
| Setup | On-chain deposit required | None | Bridge deposit |
| Coordination | All parties online | Independent, offline-capable | Sequencer |
| Finality | Fast off-chain | Eventual consistency | 7-day dispute period |
| Best for | Bilateral payments | Multi-party ledgers | General compute |

### Practical Implication
CRDT tokens are not deployable today. The existing `src/crdt/` modules in myco-bonding-curve (labor_crdt.py, batch_settlement.py, intent_matching.py) are **ahead of the industry**. UAT20 provides a blueprint for future cross-rollup balance unification.

---

## 3. Cross-Chain Interoperability

### Protocol Comparison

| Protocol | Chains | Model | Speed | Security | Best For |
|---|---|---|---|---|---|
| **CCIP** | 60+ | Message passing | 10-30 min | Risk Management Network (separate oracle set) | State sync, programmable transfers |
| **LayerZero V2** | 132 | DVN + Executor | 1-5 min | Configurable DVN set | Native multichain token (OFT) |
| **Wormhole NTT** | 40+ | Guardian network | 1-15 min | Global Accountant (supply monitoring) | Token sovereignty, Solana support |
| **Axelar GMP** | 50+ | DPoS validators | 5-20 min | 2/3 validator majority | Cosmos/IBC chains |
| **Across (ERC-7683)** | 15+ | Intent/relayer | ~seconds | Economic (relayer fronts funds) | Fast user deposits |
| **LI.FI** | 20+ bridges | Aggregator | Varies | Routes through best bridge | User UX abstraction |

### Recommended Architecture for MycoFi

**Layer 1 — State Sync: Chainlink CCIP**
- Hub on Base, spokes on ETH/ARB/OP/Polygon
- Arbitrary messaging for bonding curve state (price, reserve, tranche health)
- Programmable token transfers: send collateral + instructions atomically
- Risk Management Network prevents corruption
- Docs: https://docs.chain.link/ccip

**Layer 2 — Native Token: LayerZero OFT or Wormhole NTT**
- OFT: widest DEX/protocol integration, `npx create-lz-oapp` quickstart
- NTT: full ownership/upgradeability of token contracts
- For $MYCO and tranche tokens (myUSD-S, myUSD-M)
- Docs: https://docs.layerzero.network/v2/home/token-standards/oft-standard

**Layer 3 — Fast UX: Across + ERC-7683 or LI.FI**
- Near-instant deposits from any chain (relayers front funds)
- ERC-7683 is becoming the standard (Uniswap, Optimism Superchain adopted it)
- LI.FI auto-routes through optimal bridge
- Spec: https://www.erc7683.org/

### CCIP Cross-Chain Token (CCT) Standard
- `BurnMintTokenPool`: Burns on source, mints on destination (for tokens you control)
- `LockReleaseTokenPool`: Lock/release pattern (for external tokens)
- Self-serve registration via Token Manager UI
- Docs: https://docs.chain.link/ccip/concepts/cross-chain-tokens

---

## 4. Fiat On/Off Ramps

### Provider Matrix

| Provider | Base Chain | Custom ERC-20 | Cost | Best For |
|---|---|---|---|---|
| **Coinbase Onramp** | Native (free USDC) | No (ETH/USDC only) | Free for USDC | Base-native users, gasless |
| **Bridge.xyz** | Yes | Yes (xUSD issuance) | Enterprise pricing | Custom stablecoin, B2B |
| **Transak** | Yes | Yes (with listing) | 1-5% | Global coverage, 170+ tokens |
| **MoonPay** | Yes | Yes (with review) | 1-4.5% | Consumer UX, fraud handling |
| **Ramp Network** | Yes | Yes (via partnership) | Varies | Fast go-live (~2 weeks) |
| **Stripe Onramp** | Limited | No | Stripe fees | Existing Stripe merchants |
| **Onramper** | Aggregated | Aggregated | Routes to cheapest | Multi-provider routing |

### Recommended Architecture

**Immediate (USDC rail):**
```
User fiat → Coinbase Onramp → USDC on Base (free, gasless)
  → bondingCurve.buy(usdcAmount) → Community token minted
```

**Phase 2 (Custom stablecoin via Bridge.xyz):**
```
User fiat → Bridge.xyz → Community-branded stablecoin (cUSD)
  → xUSD backing → bonding curve → Community token
```

**Phase 3 (Direct listing):**
- List community token on Transak/MoonPay once volume/analytics thresholds met
- Apply: https://transak.com/token-listing-application

### Bridge.xyz Key Details
- Custom stablecoin issuance (`xUSD`): Deploy branded stablecoin, 1:1 USD-backed
- API: `POST /v0/transfers` for fiat↔stablecoin swaps
- Reserve transparency endpoints
- Backed by Stripe ($1B valuation)
- Contact: sales@bridge.xyz
- Docs: https://apidocs.bridge.xyz

### Regulatory Considerations
- **Using licensed onramp (Transak, MoonPay, Coinbase)** offloads MSB/KYC/AML obligations
- **GENIUS Act (July 2025)**: Federal stablecoin law — applies if token is fiat-pegged, requires 1:1 reserves + monthly audits
- **Howey Test**: Design community tokens as utility/governance, NOT investment instruments
- **Practical**: Fiat → USDC (via licensed onramp) → bonding curve is the safe path