Claude's getting pretty impressive. Orca/C for the Apple IIgs, the official on-device compiler, has been source-available for a while now, but it's written entirely in Pascal (because that compiler already existed when they started on C). Claude successfully converted it into 100% C that builds on modern PC/Mac and the conversion passes 100% of the over 500 regression tests.
Similarly, someone has now made a Windows version of Ample (a dedicated GUI for macOS that makes it much, much easier to emulate Apple machines in MAME) using Claude.