Default-cache readiness alternatives — 2026-08-10
Status: INCOMPLETE. Issue #6178 tracks real integration/policy-engine runs and independent resource/cost witnesses.
Capability boundary
internal/vcachescore.DefaultReadiness, consumed by fak cachevalue status, decides whether cache behavior is ready for default-on posture. It requires independently proven cold-path correctness, the versioned fak.cache.default_usefulness.v1 verdict, explicit provider/kernel/context/external/forecast evidence planes with correct provenance, and no unsupported active-cache path.
This contract covers only that readiness gate. Aggregate usefulness scoring, economics, agentic activation, concentration/index planning, and artifact construction remain distinct benchmark debt in this multi-capability package.
Same-workload oracle
Every arm evaluates five ordered reports:
- fully witnessed planes and correct cold path — ready;
- provider-only evidence — blocked, default-usefulness reason;
- kernel evidence mislabeled
OBSERVED— blocked, provenance reason; - unsupported external active-cache path — blocked, unsupported-capability reason;
- otherwise-ready report with cold-path correctness removed — blocked, cold-path reason.
Correctness requires all five verdicts and reason classes. A scalar score that happens to separate some fixtures is not sufficient.
Arms
| Arm | Class | Local status | Boundary |
|---|---|---|---|
| fak native default-cache readiness gate | native | available | real DefaultReadiness over committed report schema |
| usefulness-score threshold only | tuned no-policy baseline | available, incorrect | committed readiness score threshold, no provenance/cold-path policy |
| fak + Prometheus | first-class integration | unavailable | real metric export, rules, and read-back |
| fak + OpenTelemetry | first-class integration | unavailable | real collector/exporter policy and read-back |
| OPA/Rego | external | unavailable | pinned OPA and real Rego policy |
| Prometheus rules | external | unavailable | pinned Prometheus rule evaluation |
| Datadog monitors | external | unavailable | real ingestion and monitor evaluation |
| LangSmith evaluations | external | unavailable | real trace/evaluation boundary |
Unavailable product arms retain Available=false and zero measurements. An in-process imitation would not witness the named product.
Completion metrics
All arms must report true-ready, true-blocked, false-ready, false-blocked, reason mismatches, latency and throughput, CPU, peak RSS, input/network/storage bytes, setup/operator time, service/license charges, and total cost. Reproduction requires pinned versions/configuration, raw decisions, and independent read-back.
TestCompareDefaultReadinessLocalKeepsPolicyAlternativesExplicit locks the inventory, local oracle, baseline failure, and unavailable-arm zeros. BenchmarkDefaultReadinessFiveCases exercises all five real native decisions per iteration. Local timing is not a cross-product claim; no alternative is ranked until #6178 has complete real-boundary witnesses.