Problem

When a policy evaluation engine experiences a timeout or unrecognized input from an LLM prompt hallucination, standard web architecture often degrades gracefully (fail-open) to maintain uptime. In autonomous orchestration, this permits fatal state mutation.

Approach

HELM enforces a strict fail-closed boundary. If the Guardian component cannot yield an explicit ALLOW verdict within the timeout period, it yields DENY_TIMEOUT. The agent is notified of the rejection and must re-plan.

Invariants

Absence of ALLOW is DENY.
Timeout equates to DENY.
Malformed proposals equate to DENY without evaluation.

Artifacts

HELM Unified Canonical Standard v1.2
Gate Simulator

References

Saltzer & Schroeder (1975). The Protection of Information in Computer Systems.