When you say "parse codebases" is this uploading a couple thousand lines in a few different files? Or pasting in 75 lines into the chat box? Or something else?
$ find web -type f \( -name '.go' -o -name '.tsx' \) | tar -cf code.tar -T; cat code.tar | pbcopy
Then I paste it in and say "can you spot any bugs in the API usage? Write out a list of tasks for a senior engineer to get the codebase in basically perfect shape," or something along those lines.
Alternately: "write a go module to support X feature, and implement the react typescript UI side as well. Use the existing styles in the tsx files you find; follow these coding guidelines, etc. etc."