Drift between recalibrations
A scoring engine that recalibrates on a weekly or monthly cadence is silent about what happens in between. Most regime shifts (a marine heatwave, a stratospheric warming, an unexpected snowpack collapse) play out in days — fast enough to materially mis-call activities, slow enough that nobody catches them until the next refit. Insurance underwriters who price against our scores need to know we'll catch it in real time, and they need an audit trail proving so.
A lower one-sided CUSUM over daily BSS
Per cell (activity × sub-spot × horizon), every day, we compute the Brier Skill Score from the previous day's paired outcomes. A Page-style tabular CUSUM tracks the cumulative below-baseline deviation. The baseline (μ₀, σ) excludes the recent 14-day window so a slow concept drift can't quietly redefine "normal". Slack k = 0.5σ; severity thresholds at h = 2σ / 3σ / 5σ map to the watch / warning / critical ladder below. Recovery (5 sustained days below watch threshold) auto-resolves the event.
BSS drift past 2 standard deviations from baseline. Logged in drift_events; surfaces in the score response's confidenceDetail.drift_flag. No alerting, no recalibration.
BSS drift past 3σ. Slack alert to platform ops; triggers an emergency recalibration job against the affected cell only (no platform-wide blast). Tenant scores on that cell carry an elevated drift_flag.
BSS drift past 5σ — sustained, multi-day, materially below climatology. Paging escalation + recalibration as warning + automatic SPC charter regeneration (audit-trail record stamped with the event).
A charter you can hand to a regulator
The SPC charter is a versioned document covering: monitored cells, baseline windows, severity ladder, escalation policy, alerting policy, recalibration policy, and the full event log for the requested time range. Available in two formats:
Machine-readable
Schema.org-typed, ingestible by compliance pipelines. Use this for automated annual ORSA cycles, MGA renewal packs, or anywhere a regulator's tooling will parse it directly.
POST /v1/admin/drift/charter (Accept: application/ld+json)Reader-friendly
Pure-JS vector render (pdfkit), embeds a BSS time-series chart with the zero-skill reference line and the event annotations. Drops straight into a Lloyd's syndicate binding application or an MGA pitch.
POST /v1/admin/drift/charter (Accept: application/pdf)Mapped to three standards
The charter isn't a marketing artefact — it's structured to satisfy the specific compliance requirements that gate parametric underwriting. Each row below maps a section of the charter to the corresponding regulatory citation.
The drift monitor satisfies the §IV.B "ongoing model performance monitoring" requirement — independent, automated, with severity-based escalation and an immutable event log. Charter regeneration handles §IV.D "model change management".
The charter documents "appropriate processes to ensure all relevant external and internal risks are taken into account" — specifically the forecast-model risk component. SPC is the standard mechanism the industry accepts.
MS13 §3.4 requires "a documented process for detecting and responding to deteriorations in model performance". The L9 monitor + charter is that process, with the drift_events table as the audit trail Lloyd's underwriting committee can subpoena.
confidenceDetail.drift_flag
Every /v1/score response on a cell with an open drift event carries an inline flag. Your client can read it and decide: widen tolerances, route to a human reviewer, or just surface "we're less confident than usual here" to the end user. No separate API call, no polling.
{
"score": 64,
"verdict": "marginal",
"confidence": 0.71,
"confidenceDetail": {
"mode": "forecast",
"drift_flag": {
"severity": "warning",
"cell": "kitesurfing / tarifa-balneario / 24h",
"fired_at": "2026-05-18T04:00:00Z",
"days_in_decline": 6,
"recalibration_triggered": true
},
...
}
}The parametric MGA on-ramp
If you're an MGA or a Lloyd's syndicate evaluating Goable as a parametric primitive provider, the SPC charter is one of the three artefacts you'll want — the others are the forecast verification feed and per-cell skill estimates. The partnerships desk routes you to the right contracting + DPA shape.