One thing I'd add to this list: lots and lots of examples. Coding agents are absurdly good at understanding and adapting examples. If your new language include

One thing I'd add to this list: lots and lots of examples. Coding agents are absurdly good at understanding and adapting examples. If your new language includes a large collection of searchable examples even a weaker model should be able to find something close to what it's trying to achieve and directly adapt that example code.