# CCIP Bridge ↔ Ethereum Mainnet Connection

**Last Updated:** 2026-02-12  
**Status:** Active

---

## Overview

Chain 138 does not use Chainlink’s public CCIP network (custom chain). Cross-chain sends from Chain 138 to Ethereum mainnet use:

1. **Chain 138:** Custom router + WETH9 bridge (emits `MessageSent`).
2. **Mainnet:** Deployed **CCIPRelayRouter** and **CCIPRelayBridge** that accept relayed messages.
3. **Relay service:** Off-chain process that watches Chain 138 for `MessageSent` and calls mainnet relay router to deliver.

---

## Mainnet Contracts (Ethereum)

| Contract           | Address | Role |
|--------------------|---------|------|
| **CCIPRelayRouter** | `0xAd9A228CcEB4cbB612cD165FFB72fE090ff10Afb` | Receives relayed messages; calls bridge `ccipReceive`. Relayer must have `RELAYER_ROLE`. |
| **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. |
| WETH9              | `0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2` | Canonical mainnet WETH. |

**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`.

---

## Chain 138 Setup

| Role   | Address | Notes |
|--------|---------|------|
| **Router** (LINK fee) | `0x42DAb7b888Dd382bD5Adcf9E038dBF1fD03b4817` | Emits `MessageSent`; relay service listens here. |
| **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)
   ./scripts/bridge/fund-mainnet-relay-bridge.sh
   # Option B: Specific amount (wei)
   ./scripts/bridge/fund-mainnet-relay-bridge.sh 1000000000000000000

   # Or manually:
   cast send 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2 \
     "transfer(address,uint256)" \
     0xF9A32F37099c582D28b4dE7Fca6eaC1e5259f939 \
     <amount_wei> \
     --rpc-url $ETHEREUM_MAINNET_RPC --private-key $PRIVATE_KEY --legacy
   ```
   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:
   ```bash
   ./scripts/bridge/grant-relayer-role-mainnet.sh
   ```
   Or manually: `cast send 0xAd9A228CcEB4cbB612cD165FFB72fE090ff10Afb "grantRelayerRole(address)" 0x4A666F96fC8764181194447A7dFdb7d471b301C8 --rpc-url $ETHEREUM_MAINNET_RPC --private-key $PRIVATE_KEY --legacy`

3. **Start the relay service:**
   ```bash
   cd smom-dbis-138/services/relay
   # .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:
   ```bash
   RPC_URL_MAINNET=https://ethereum.publicnode.com ./scripts/bridge/fund-mainnet-relay-bridge.sh 1000000000000000
   ```
   (1e15 wei = 0.001 WETH.)

---

## References

- [TOKEN_MAPPING_AND_MAINNET_ADDRESSES.md](TOKEN_MAPPING_AND_MAINNET_ADDRESSES.md) — Full token mapping (138↔Mainnet), relay-supported tokens, and recommendations.
- [SEND_ETH_TO_MAINNET_REVERT_TRACE.md](SEND_ETH_TO_MAINNET_REVERT_TRACE.md) — Revert history and deployed LINK/native-ETH bridges.
- [scripts/README.md §8](../../scripts/README.md) — Send command and env.
- [services/relay/README.md](../../smom-dbis-138/services/relay/README.md) — Relay service deployment and config.
- [CONTRACT_ADDRESSES_REFERENCE.md](../11-references/CONTRACT_ADDRESSES_REFERENCE.md) — Chain 138 addresses.