Its not about agents then. Its about every individual platform providing the means to implement a secure set of permissions for agents AND then not messing up the assignment of permissions to the agent. Even then, a flaw in the authorization design will lead to agent finding it anyway.
You're right, It must be unifying.
The answer is the same as asking how a random human using your routing num or SSN and being 100% the human can't abuse it or leak while "normally" finishing most work. Solve for people and an AI solution naturally falls out.
If you're a SV eng I'd tell you to DM if interested but alas.