Check the RPC chain before reading balances or sending

An RPC URL is configuration, not proof of network identity. Check the chain it actually serves before trusting any balance, allowance or simulation result.

EIP-1474 includes eth_chainId in the RPC interface. Normalize the returned quantity and compare it with the intended chain. Do this during startup and when introducing a fallback endpoint; a human-readable hostname or environment-variable name is not enough.

Fail closed on mismatch

If the configured BNB Smart Chain client reports a different chain, mark that client unavailable. Do not adapt the trade to the unexpected network automatically. Identical addresses across chains can contain different contracts and balances.

Bind provider requests and RPC reads to one chain configuration. A common error is quoting on one network while a generic public client remains attached to another. The resulting allowance can appear sufficient, but it describes unrelated state.

Recheck the write boundary

The wallet has its own chain context. EIP-1193 defines the chainChanged event and the relationship to eth_chainId. Before a write, verify both the prepared transaction's chain and the wallet's active chain. A correct backend RPC does not make the browser wallet correct.

Keep chain mismatch errors distinct from RPC outages. Operators need to repair configuration, not simply increase timeout values or retry more often.

A useful test points a configured client at a mock reporting another chain. No token read, approval request or submission should follow. Repeat for a fallback endpoint selected only after the primary fails; backup infrastructure deserves the same identity checks as the primary path.