tldr:

dhh says 37signal's apps for Hey (their email platform moving to native)

backend for their email platform is now Rust - written by agents

says Rust produces small binaries - cutting number of servers needed from 110 to 10. hell they could serve peak traffic on a Raspberry Pi

says now that agents write all the code - use faster / native languages.

rails or ruby hardly get a mention besides that they might be well placed to capture web apps written by agents.