| **CCIPRelayBridge** | `0xF9A32F37099c582D28b4dE7Fca6eaC1e5259f939` | Holds WETH; releases to recipient when relay router calls `ccipReceive`. **Must be funded with WETH** for payouts. **WETH9-only** — no other tokens accepted. |
**Token mapping:** Chain 138 → Mainnet address mapping and which tokens the relay bridge supports are in [TOKEN_MAPPING_AND_MAINNET_ADDRESSES.md](TOKEN_MAPPING_AND_MAINNET_ADDRESSES.md). Source of truth: `config/token-mapping.json`.
| **Bridge** (LINK fee) | `0xcacfd227A040002e49e2e01626363071324f820a` | Pay fee in Chain 138 LINK. Default in `CCIPWETH9_BRIDGE_CHAIN138`. |
| **Bridge** (native ETH fee) | `0x63cbeE010D64ab7F1760ad84482D6cC380435ab5` | Pay fee in native ETH. |
Both bridges have **mainnet destination** set to **CCIPRelayBridge** (`0xF9A32F37099c582D28b4dE7Fca6eaC1e5259f939`), so all 138→mainnet sends are delivered via the relay.
---
## End-to-End Flow
1. User on Chain 138 calls bridge `sendCrossChain(mainnetSelector, recipient, amount)` (e.g. via `scripts/bridge/run-send-cross-chain.sh`).
2. Bridge pulls WETH from user, calls router `ccipSend(...)` with `receiver = abi.encode(CCIPRelayBridge)`.
3. Router emits `MessageSent` (no Chainlink relayer).
4.**Relay service** (Node) watches the Chain 138 router for `MessageSent`, builds `Any2EVMMessage`, and calls mainnet **CCIPRelayRouter.relayMessage(CCIPRelayBridge, message)**.
5. Relay router calls **CCIPRelayBridge.ccipReceive(message)**; bridge transfers WETH to `recipient` on mainnet.
---
## Running the Relay Service
1.**Fund mainnet CCIPRelayBridge** with WETH so it can pay recipients:
```bash
# Option A: Script (transfers deployer's full WETH balance by default)
If the default RPC rate-limits (429), set `ETHEREUM_MAINNET_RPC` to Infura or Alchemy in `smom-dbis-138/.env`.
2.**Grant relayer role** (if not already): The relay tx will revert with "transaction execution reverted" (no revert data) until the relayer address has `RELAYER_ROLE` on the mainnet router. As the router's admin (deployer), run:
# .env: RPC_URL_138, RPC_URL_MAINNET or ETHEREUM_MAINNET_RPC (Infura/Alchemy recommended to avoid 429), PRIVATE_KEY (relayer), CCIP_RELAY_*
npm start
```
For mainnet RPC, set `RPC_URL_MAINNET` in `services/relay/.env` or `ETHEREUM_MAINNET_RPC` in `smom-dbis-138/.env`. Prefer Infura (`https://mainnet.infura.io/v3/<PROJECT_ID>`) or Alchemy; see [RPC_ENDPOINTS_MASTER.md](../04-configuration/RPC_ENDPOINTS_MASTER.md).
Config defaults in `services/relay/src/config.js` point to the router and bridges above; override with env vars if needed.
### If relay tx reverts with "transaction execution reverted"
1.**Relayer role:** Ensure the relayer has `RELAYER_ROLE`: run `./scripts/bridge/grant-relayer-role-mainnet.sh` (use `RPC_URL_MAINNET=https://ethereum.publicnode.com` if Infura returns 403).
2.**Bridge WETH:** The mainnet CCIPRelayBridge must hold at least the amount being relayed. If the bridge balance is lower than the transfer amount, fund it:
