I worked at Slack earlier this year. Slack adopted Cursor as an option in December of 2024 if memory serves correctly. I had just had a project cut due to a lot of unfortunate reasons so I was working on it with one other engineer. It was a rewrite of a massive and old Python code base that ran Slack's internal service catalog. The only reason I was able to finish rewrites of the backend, frontend, and build an SLO sub-system is because of coding agents. Up until December I'd been doing that entire rewrite through sixteen hour days and just pure sweat equity.

Again, that codebase is millions of lines of Python code and frankly the agents weren't as good then as they are now. I carefully used globbing rules in Cursor to navigate coding and testing standards. I had a rule that functioned as how people use agents.md now, which was put on every prompt. That honestly got me a lot more mileage than you'd think. A lot of the outcomes of these tools are how you use them and how good your developer experience is. If professional software engineers have to think about how to navigate and iterate on different parts of your code, then an LLM will find it doubly difficult.