Latency matters if you want programmers to be able to work interactively. We multitask because LLMs are too slow.

That's happened before, with people submitting batch jobs in the mainframe era, people working on big projects that take an hour to compile, or people waiting for code reviews.

However, even if the LLMs become fast, the coding agent will likely bottleneck on running tools. You will need to keep your tests fast, too.