Most scoring systems collapse a rich picture into a single number — a weighted average, a normalised score, a traffic light that hides the threshold. The consumer sees "0.73" and has no way to ask how confident is that? or how close to the edge? without reverse-engineering the formula.
ASSAY's scorer refuses to produce a number. It maps every commitment to one of four verdict stops — robust, marginal, tight, violated — via a signed margin band, using signs only. No interior cut, no invented epsilon, no decimal in any cell face (ASSAY-DEC-9).
The signs-only rule
The scorer computes a margin band [m_lo, m_hi] — the interval between what the plan delivers (banded) and what the commitment demands (a threshold). The verdict is read from the signs alone:
m_lo = 0 → marginal (the lower edge just touches)
m_lo < 0 ≤ m_hi → tight (the band straddles the threshold)
m_hi < 0 → violated (the whole band fails)
This is the unique four-stop mapping that satisfies oracle O-3: the verdict changes only at band edges, never inside a band. Move a threshold by one unit inside the band and the verdict stays put. Push it past a band edge and the verdict flips — at exactly the point the underlying assessment actually changes its mind.
The honest matrix
The s2Matrix component renders plans × commitments as a grid of these four-stop chips. No decimal appears in any cell. The margin band is available on hover, shown only on demand (G2) — never as a headline number.
| C1 depth | C2 width | C3 clearance | C4 capacity | |
|---|---|---|---|---|
| P1 strait-early | robust | robust | marginal | tight |
| P2 sweep-first | marginal | tight | robust | robust |
Illustrative widget, fixture data. The matrix shows Meridian plans P1/P2 scored against commitments C1–C4 under the BASE scenario. The four-stop chips are the same colour language the shipped s2Matrix component uses. Frozen as shipped on 2026-07-13.
Try it: drag the threshold
The slider below implements the real signs-only rule. The assessed band is fixed at [9, 13] (the O-3 oracle values). Drag the threshold and watch the verdict flip only at the band edges — never inside the band.
Illustrative widget, real rule. The verdict mapping is the same signs-only algorithm the shipped scorer uses. The assessed band [9, 13] is the O-3 oracle case from the Meridian vignette. Frozen as shipped on 2026-07-13.
O-3: the oracle that tests the mapping
Oracle O-3 is a hand-computed test case (vignette §9) that sweeps a threshold across the scored band. The four-stop rule must change verdict at exactly the band edges [9, 13] — and nowhere else. Any rule with an interior cut (a midpoint, a weighted average, an arbitrary epsilon) would flip inside the band, failing O-3. The signs-only rule is the unique survivor.
Sources & trace
- Scorer — src/score.ts · src/interval.ts
- Honest matrix — src/components/s2Matrix.ts
- Four-stop mapping — 03-score-plan.md §3 (the signed-margin decision)
- Oracle cases — O-1, O-2, O-3 in the Meridian vignette §9
- No-decimal rule — ASSAY-DEC-9 in the decision register