Recently, while working on an in-progress open-source framework called Projector, I ran into a (not particularly novel) issue: one of it's internal packages (core) had grown during this period, and was not nearly as flyweight as it needed to be in the browser. The result was 10-20kbs of unnecessary machinery getting pulled in.
I noticed this while running examples. I was consistently hitting a wall in bundle sizes that was surprisingly difficult to get past, even for someone as stubborn and relentless as I am. Naturally, I turned to Claude and ChatGPT to help me with this, and ended up using ChatGPT 5.5 with Codex as I find that, with the "precise" output mode, it tends to be a little more honest than Opus 4.8 these days.
I shared exported HAR network logs with it, having it go through the chunks to confirm where the bulk was; consistently, it confirmed that the issue was around an entangling of authoring/resolution code with runtime code in core that was pulling in too much to the browser.
The technical details here aren't really important, but I'm using them to illustrate a larger point.
We then iterated through a lot of different solutions—I setup a "goal" in codex with benchmarks to hit, and gave it a bunch of constraints, context, and tooling. Finally, after about 2-3 hours of looping against that goal, it completed.
