Writing a compiler with an agent: what worked and what did not

I am writing a small compiler as a hobby and used the agent a lot. It was great at the parser and the tests, and bad at register allocation, where it kept proposing textbook algorithms that did not fit my IR.

Biggest lesson: let it write tests from the spec first, then implement against them.

Very similar experience with a database engine. Great at scaffolding, needs a lot of steering on the core algorithms.

Tests from the spec first is the best advice in this whole forum.