it's very good at this BTW

I've found it's terrible at digesting a few codebases I've needed to deal with (to wit, 2007-era C# which used lots of libraries which were popular then, and 1993-era Visual Basic which also used from third party library that no LLM seems to understand the first thing about).

	▲	simonw 3 hours ago \| parent \| next [-]
		I had great results recently with ~22 year old PHP: https://simonwillison.net/2025/Jul/1/mid-2000s/ It even guessed the vintage correctly! > This appears to be a custom template system from the mid-2000s era, designed to separate presentation logic from PHP code while maintaining database connectivity for dynamic content generation.
	▲	nl 3 hours ago \| parent \| prev [-]
		I suspect the problem with VB is that VB 4 and 5 (which I think was that era) were so closely tied to the IDE it is difficult to work out what is going on without it. (I did Delphi back when VB6 was the other option so remember this problem well)