Cache-isolation preprint separates hardware timing evidence from simulated defenses

Discuss shared assistant confidentiality with security, data stewards and the service owner. Ask which groups share infrastructure and which documents enter prompts. Offer a bounded architecture and assurance review using synthetic content. The value hypothesis is identifying an unexamined information boundary before wider adoption. This paper can motivate questions but cannot quantify a customer's likelihood of compromise, demonstrate an institutional incident or certify a defense. Request production evidence from suppliers and avoid presenting simulation outputs as observed breach reduction.

Map authenticated users to every cache and retrieval store in the proposed service. Require synthetic fixtures, isolated test identities and explicit permission boundaries. Compare allowed reuse within a principal with prohibited reuse across principals, recording server and client telemetry under realistic load. Inspect semantic retrieval separately from exact-match caching. Validate the actual engine and release instead of importing a paper's configuration. A useful proof of value demonstrates traceable identity enforcement and measures the resulting capacity cost; it does not establish universal protection against all side channels.

Security engineering should own the threat model with platform operators and application maintainers. Implement an inventory of shared state, change approval and incident escalation. Dependencies include trustworthy identity propagation, test capacity and staff able to interpret timing measurements. Train maintainers to revisit the boundary when routes or storage change. Proposed acceptance requires documented ownership for every shared store, reproducible tests of allowed and denied reuse, and a demonstrated containment procedure. Review before sensitive records enter the service. Risks include incomplete identity mapping and mistaking laboratory controls for operational assurance.