Do not assume same RPC belongs to the same chain

[ferranbt]

I think contender uses the RPC endpoint as a chain identification, however, this is not always true. For example, you can run different local devnets that will have the same endpoint (e.g localhost:8545).

An alternative would be using the genesis hash of the chain.

[zeroXbrock]

you're correct, it does use RPC_URL as identification, which can sometimes lead to confusion (esp. on localhost). Genesis hash is a great idea!