Voice to text and biometrics are noisy sources, so a big part of the problem is dealing with that noise.

Typing is not a noisy source. It should be reliable and deterministic.

Protecting an agent from fairly obvious attacks should also be deterministic.

The fundamental issue is, that "we" somehow decided it would be a good idea to throw all the fundamental ideas of computing (determinism, context, separation between data and execution,...) away and try to solve the issues by running a probabilistic/stochastic word generator on top of deterministic circuits instead at 10 magnitude worse efficiency.

It's not a fundamental issue. Determinism and "separation between data and execution" are artificial constructs, make-believe universe in which we design classical code, and a whole lot of hardware engineering goes into allowing us to briefly forget it's all fake.

Real world is probabilistic in practical / metrological, if not fundamental sense, and separation between data and execution does not exist. Our reality does not support such separation.

> a probabilistic/stochastic word generator on top of deterministic circuits instead at 10 magnitude worse efficiency

It's 10 magnitude better efficiency end-to-end, if you factor in design time you'd have to spend to get your "deterministic circuits" (which really aren't, we just paper over it) into shape so they deterministically solve a specific problem, for each problem you want to solve - where with the "stochastic word generator", you just need to change the text prompt.

Typing is absolutely a noisy source.