Wait until your baby hits their first birthday or sits confidently on their own...

https://noon-wiki.win/index.php/How_Tight_Should_the_Harness_Be_in_a_Child_Bike_Seat%3F

Wait until your baby hits their first birthday or sits confidently on their own before you ride together. Your little co-pilot needs strong neck muscles to hold their head up in a helmet. Front-mounted seats offer a great view and keep them close