git.stella-ops.org/docs/modules/policy/prep/2025-11-20-policy-engine-30-002-prep.md

Policy Engine · Simulation Bridge Prep (POLICY-ENGINE-30-002)

• Date: 2025-11-20
• Depends on: Overlay projection (30-001)
• Working directory: src/Policy/StellaOps.Policy.Engine

Simulation request schema

• tenant (string)
• rules[] (string) — ruleIds to simulate; if empty, simulate all active rules.
• overlays[] (optional) — inline OverlayProjection objects to test hypothetical changes without persisting.
• paths[] — array of PathScope inputs.
• mode (preview|whatif) — preview returns decisions only; whatif also returns delta vs current overlays.
• seed (int, optional) — for deterministic randomization if simulations sample paths.

Response schema

• decisions[] — per PathScope result: pathScope, decision, reasons[], ruleId, version, effectiveAt.
• deltas[] (only for whatif) — entries with ruleId, baselineDecision, candidateDecision, diffReason.
• metrics — echo of counters: evaluated, allowed, denied, warned, deferred for quick UI.

Determinism rules

• When seed absent, use fixed seed 0xC0DEC0DE for any randomized sampling.
• Responses ordered by input paths[] index, then ruleId.

Acceptance for prep completion

• Simulation schemas are frozen; downstream UI/CLI harnesses can rely on shapes and ordering.
• Delta semantics clarified to unblock change-event publication (30-003).