Wait until your baby turns one and sits up firmly unassisted. Strong neck...

https://www.foxtrot-bookmarks.win/most-kids-are-ready-for-bike-seats-around-age-one-check-for-strong-neck

Wait until your baby turns one and sits up firmly unassisted. Strong neck control is vital for safety before you consider a bike ride. Choose front seats for close connection, rear mounts for extra support, or trailers for maximum stability