Can you please provide more detail when it's best to use runtime type checks? For webapps with strict TS config, I'm failing to see the advantage. Runtime errors can occur when crossing boundaries from server API to UI but when you discover the exceptions, you go fix your contract.

1st it's easier to identify which contract is inaccurate, or even whether the contract is inaccurate or not in the first place

2nd it's more convenient for both the end-user and the developers that errors are handled this way