Do I need H1B re-stamping?

[mekia]

My H1B stamp (with previous employer) is valid until Sep 2026. I changed employer and my new I797 is valid until February 2028.

Do I need new / re-stamping if I leave the country and come back in January 2026? If not, when would I need it - after Sep 2026 or Before Sep 2026?

Also not sure if it matters but I got a new passport and my h1b stamp is on previous passport router login 192.168.l.l.link/