# Step 2 — Device app lib

- **EVM/Chain 138:** Use existing `@ledgerhq/hw-app-eth`; no new device app lib. Ensure `chainId: 138` in transaction building/signing.
- **app-ethereum (C):** If upstream Ledger app-ethereum does not list Chain 138, add the line from `network-entry-chain138.c` to `src/network.c`. Our fork already has it at `pr-workspace/app-ethereum/src/network.c` line 42.
- **Icons:** If Ledger requires a network icon, use their icon process (see Device App Kit docs). Chain 138 can share the generic Ethereum-style icon until a custom one is added.