This document describes how to configure **addDestination** on each CCIP WETH9/WETH10 bridge and how to **fund bridges with LINK** for cross-chain fees. Use it after deploying bridges via `deploy-all-mainnets-with-mapper-oracle-pmm.sh ccip` (or DeployAll per chain).
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## 1. Overview
- Each **CCIPWETH9Bridge** and **CCIPWETH10Bridge** must have destination chains set via `addDestination(uint64 chainSelector, address receiverBridge)`.
- Only the bridge **admin** can call `addDestination`. Use the same deployer key (or the key that owns admin) when running scripts.
- For each pair of chains (e.g. Ethereum ↔ Chain 138), you add the **destination chain selector** and the **receiver bridge address** on the other chain.
- CCIP fees can be paid in **LINK** (or native token depending on contract). Ensure each bridge contract has enough **LINK** (and/or native) to pay for `ccipSend` fees.
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## 2. Chain Selectors and .env Bridge Variables
Use these from `.env` (or [Chainlink CCIP Supported Networks](https://docs.chain.link/ccip/supported-networks)):
Repeat for each destination chain (BSC, Polygon, Base, Optimism, Avalanche, Cronos, Gnosis, Chain 138) using the correct selector and the corresponding bridge address on that chain.
- CCIP charges fees for each cross-chain message; bridges typically pay in **LINK** (or native) depending on the contract’s `feeToken` and `ccipSend` usage.
- **Per chain**: Ensure the **bridge contract** holds enough **LINK** (and native for gas) so it can pay CCIP fees when users call `sendCrossChain` (or equivalent).
- **Destination-only receipt** on a chain does not by itself require LINK on that chain's bridge contract, because `ccipReceive(...)` does not pay the CCIP fee.
- **Outbound sending** from a chain does require a fee payment path on that chain's bridge contract.
- Current WEMIX nuance:
-`CCIPWETH9Bridge` may be configured for native-fee mode by setting `feeToken = address(0)`.
-`CCIPWETH10Bridge` still requires LINK in the current implementation.
1. Get LINK on the same chain as the bridge (e.g. from an exchange or faucet).
2. Transfer LINK to the **bridge contract address** (the same address you use for `addDestination`), or use any approved mechanism (e.g. admin top-up function if the contract has one).
- **LINK token addresses** per chain are in `.env` (e.g. `CCIP_GNOSIS_LINK_TOKEN`, `CCIP_ETH_LINK_TOKEN`, etc.) and on [Chainlink CCIP Supported Networks](https://docs.chain.link/ccip/supported-networks).
- **Script:** Run `scripts/deployment/fund-ccip-bridges-with-link.sh` to send LINK to all CCIP bridges (sources `.env`). Flags: `--link <amount>` (default 10 LINK), `--dry-run` (print `cast` only), **`--cap-to-deployer`** (per chain: each bridge gets `min(--link, deployer_balance // bridges_on_chain)` so you can use only deployer LINK without matching 10 LINK on every chain). See script header in `scripts/deployment/fund-ccip-bridges-with-link.sh`.
- **Chain 138 custom CCIP router:** `CCIPRouter.sol` on Chain 138 is **event-only** — `ccipSend` records `MessageSent` and collects LINK fees but **does not deliver**`tokenAmounts` to destination chains. Do **not** use `FundBridgeLinkViaCcip138` / `bridge-link-via-chain138-*.sh` for operator bridge funding until a full token-delivery router is deployed. Preflight: `scripts/verify/verify-chain138-ccip-router-token-delivery.sh`.
Use --dry-run to print commands only. Step A uses `--gas-limit` (default 200000) to avoid RPC estimateGas issues on Chain 138; "destination already exists" means that lane is already configured. Step B: optional `.env` overrides for high-fee chains: `BRIDGE_ETH_GAS_PRICE=40000000`, `BRIDGE_ARBITRUM_GAS_PRICE=25000000`, `BRIDGE_AVALANCHE_GAS_PRICE=140000000`.
## 6. Checklist (post-deploy)
- [ ] Run `configure-all-ccip-bridge-destinations.sh` (and retry any failed chains).
- [ ] For each deployed bridge (WETH9 and WETH10) on each chain, call `addDestination` for every **other** chain you want to support (using that chain’s selector and the receiver bridge address).
- [ ] Fund each bridge contract with LINK (and native if needed) on its chain.
- [ ] Run a small test transfer per lane (e.g. 138 ↔ Ethereum, 138 ↔ BSC) and verify on explorers.
- Bridge config (138 ↔ Mainnet): `scripts/deployment/configure-bridge-destinations.sh` (note: may use different ABI; prefer `addDestination(uint64,address)` for CCIPWETH9/CCIPWETH10)
