This reminded of me porting low-level JS library and its tests (~10k loc) to Java about 6 months ago (so mostly it was Sonnet 4)

My goal was to have 1:1 port, so later I can easily port newer commits from original repo. It wasn’t smooth, but it the end it worked

Findings:

* simple prompt like port everything didn’t work as Sonnet was falling into the loop of trying to fix code that it couldn’t understand, so at the end it just deleted that part :))

* I had to switch to file by file basis, focus Claude on the base code then move to files that use the base code

* Sonnet had some problems of following 1:1 instruction, I saw missing parts of functions, missing comments, even simple instruction to follow same order of functions in the file (had to tell explicitly to list functions in the file and then create separate TODO to port each)