So i tested my app from the link given by shopify-cli and it works fine.
i.e.
https://123.ngrok.io/auth?shop=abc.myshopify.com
then after hosting it on vercel
i tried installing from the partners dashboard, app setting page
more actions >> Test on development store >> install app
now this results in a link of the form:
https://foo.vercel.app/?hmac=bar&shop=buz.myshopify.com×tamp=163750xxxx
and here the app does not get the host param, then app bridge just spits out errors
about missing host param
not really sure what to do here