Gpt5 isn't an improvement to me, but Claude sonnet4.5, handle terragrunt way, way better than the previous version did. It also go search AWS documentation by itself, and parse external documents way better. That's not LLM improvement, to be clear (except the terragrunt thing), I think it's improvement in data acquisition and a better inference engine. On react project it seems way, way less messy also, I have to use it more but the inference engine seems clearer. At least less prone to circular code, where it's stuck in a loop. It seems to be exiting the loop faster, even when the output isn't satisfactory (which isn't an issue to me, most of my prompt have more or less 'only write functions template, do not write the inside logic if it has to contain more than a loop', I fill the blanks myself)