I'm sure the other engineers on the project will have their own opinions here, but for me there's the obviously visible parts to the project (the prompt, tools,

I'm sure the other engineers on the project will have their own opinions here, but for me there's the obviously visible parts to the project (the prompt, tools, ...) and the invisible parts (indexing, tokenising/chunking, parallelising, streaming, ...). Building agents is an experimental process. You test an approach, maybe it works, and there's not always an obvious reason why certain experiments fail or succeed. We built three prototype agents in a Python and JS, because those languages favour scrappy fast iteration. This helped us quickly nail down our approach to the 'visible' parts. Once we nailed down our approach, we rebuilt the agent in Rust because the speed and safety favoured all the 'invisible' parts of the project.