Prototype
Pick a policy, switch individual signals on and off, then sit the exam and try to break it. Everything runs in this browser; nothing is uploaded. The point of the prototype is to make the difference between detecting and preventing obvious before anyone buys either.
Permissions, the on-device face model, and a two-second capture of how this candidate normally sits. Calibrating against their own neutral pose is what stops an off-centre laptop camera from reading as "looking away" for the whole exam.
Look at the screen and hold still while this is captured.
Every signal is appended with a sequence number and chained to the hash of the one before it, so a candidate who disputes the verdict can be shown an ordered log whose entries are consistent with each other.
To be precise about what that does and does not prove: this chain is computed in the browser, and the browser holds both the entries and their hashes — so it demonstrates internal consistency only. Anyone able to edit the log can recompute the whole chain around their edit. Authenticity needs the chain written and signed server-side, from signals the server received. In production the browser reports; the server seals and decides.