What access do you need to fix a checkout bug?

Ideally three things: (1) admin access to read checkout, shipping, payment and agreement config; (2) SSH or a deploy path to read var/log/exception.log and ship the fix; and (3) a staging environment (we’ll clone live if there isn’t one). If you can only give live admin access at first, we can still start by reproducing the bug as a shopper and reading the on-screen and console errors.