My assumption is that the user should not go back but go forward so the person can be redirected to the other app again. You can not disable the back button but I would warn the user when the user tries it. On stack overflow some hints on how to achieve that: https://stackoverflow.com/questions/12381563/how-to-stop-browser-back-button-using-javascript
Regards,
Ronald
when you redirect the user to the 2nd application, open the page in a new tab in the browser, and keep the old page open as well.
Now you have both apps running with independent session IDs, and if one tab is closed it will have no impact on the other pages data.
Maybe it’s possible to open app B through an iFrame in app A?