diff --git a/THREADS.md b/THREADS.md
index 2523e5e..5d94596 100644
--- a/THREADS.md
+++ b/THREADS.md
@@ -8649,3 +8649,157 @@ anchors are your GLB), but the tooling is now waiting, not TODO.
     lead-0 card pins, the cross, the cross's teeth). No wind-panel polish this sprint — the
     optional slot went to crossing all three yards instead of one, filed here with its reason:
     a complete cross is worth more than a prettier panel the week the board ships.
+
+[C] 2026-07-21 — 🤝 **CONVERGENCE, DECLARED FIRST: TWO LANE-C SESSIONS RAN GATE 1 IN PARALLEL,
+    and I found out by having my push REJECTED. What follows is landed ON TOP of `f029274`
+    with NOT ONE LINE OF IT CHANGED — I did not force, I did not rebase over it, and I dropped
+    every part of my own work that duplicated it.** Selftest **494/0/0** (their 490 + my 4).
+
+    The split turned out clean, which is luck rather than planning. `forecastHonest(def)`
+    answers *"can the forecast describe this STORM"* — validator, finite stats, the stone
+    vocabulary ceiling — and it is better than the storm-side half I had written, so mine is
+    gone. What it structurally cannot reach is the two things my brief named, because it takes
+    a DEF and not a PAIRING and it never touches the card:
+    1. **WHAT THE CARD PRINTS.** Their gate can pass a storm whose card then omits the fact
+       that matters. It does, tonight, on night 7 — see below.
+    2. **WHICH YARD the storm is printed over.** `forecastHonest` has no `site` argument, so
+       "the soaker only ever offers over site_02" was still enforced by nothing but a comment
+       in A's POOL.
+    My work is now exactly those two, added after a divider in weather.js that says so. What I
+    abandoned: my own `forecastRefusal` (theirs is better), my exposure cross (theirs crosses
+    A's `exposureOf` directly and item-wise — strictly stronger than mine, which could only
+    cross the data against the runtime), and the `forecast.js` pure-module split. **The split
+    is the one thing I still think was right and am NOT relitigating today** — it made the
+    whole worded surface run in the node one-second loop, and 4 of my 6 mutation checks ran
+    there in seconds instead of two minutes a go. It is on branch `s17-c-mine` (commit
+    `3884108`, 485/0/0 standalone) if the integrator ever wants it; forcing a file move onto a
+    landed design to win an argument about addresses is churn, and I am not spending the
+    sprint's goodwill on it.
+
+[C] 2026-07-21 — 📇 **THE OFFER BAND — and the measured finding that A's BOARD LIES ABOUT
+    NIGHT 7 as pushed.** The single thing my brief was most explicit about: *"an offer card
+    that hides the hail is the board lying, and the soaker's whole design is that its wind
+    reads gentle while its hail is the trap."* It does, and it was.
+
+    **MEASURED FIRST, before a line was written.** A's card prints `f.wind` and `f.stones` — a
+    reasonable pair. Night 7's two offers under that pair:
+    | night 7 | wind line | stones line |
+    |---|---|---|
+    | **the soaker** (scripted, site_02) | gusts to ~55 km/h | fine pea stones |
+    | the early buster (alt, swing lawn) | gusts to ~76 km/h | pea stones |
+    **On both printed lines the soaker is the softer job.** It is not: 14.9 s of hail against
+    2.4 s, and 44 mm/hr of rain against 16.5. The board recommended the trap in the storm's own
+    voice, before a dollar is spent. Not A's mistake to have made — the fields were there and
+    the card picked two of them, which is exactly why the fix is not "also print rainRate".
+
+    **`offerBand(def, lead)` returns an ORDERED LIST** of `{key, text}` — wind, hail (iff the
+    storm hails), rain rate (always), change (always), confidence (iff hedged). The FORECAST
+    decides which facts a night carries and hands over all of them, so a card that maps the
+    list cannot drop the next fact somebody adds to a storm. Same construction and the same
+    reasoning as A's own `stormsToPreload(nights, pool)` split: an omission that is possible
+    will eventually happen. Night 7 now reads, in the real card, my own eyes on :8826 —
+    · soaker — `gusts to ~55 km/h` · **`hail likely · fine pea stones · 15s of it`** ·
+      **`rain to 44 mm/hr`** · `southerly change at 40s` · $46 · $205 at risk
+    · buster — `gusts to ~76 km/h` · `hail possible · pea stones · 2s of it` ·
+      `rain to 16 mm/hr` · `southerly change at 18s` · $57 · $255 at risk
+    The choice is now real and genuinely hard: **the soaker pays LESS, risks LESS, and is the
+    worse night.** That is the game arguing with the player instead of flattering them.
+
+    **⚠️ SECOND FINDING — THE CHANGE LINE IS NOT DECORATION.** `storm_03_southerly` and
+    `storm_03b_earlybuster` are IDENTICAL in every number the band prints — sustained 13.0,
+    gustPeak 21.4/21.2, rain 16.5 mm/hr, hail 2.4 s at size 0.70 — and differ ONLY in when the
+    change lands, 30 s against 18 s. **The board offers exactly that pair** (the buster is the
+    drawn alternative on nights 5 AND 7). Drop the change line and the board offers two jobs
+    whose weather it has just claimed to describe, described identically, and calls it a
+    choice. Pinned as its own case; it goes red with the two bands diffed in the message.
+
+    **A — THE HUNK, verbatim.** I applied it on a scratch tree to LOOK at the card, then
+    reverted it — hud.js and main.js are yours (the leadFor precedent).
+    1. `main.js` import: `import { loadStorm, createWind, forecastLines, offerBand } from './weather.js';`
+    2. `main.js` `pricedOffers()`, one line beside `forecast:` — which I left in place, so
+       nothing of yours has to move and the card can adopt on its own schedule:
+       `band: def ? offerBand(def, 0) : null,`
+    3. `hud.js` `offerHtml`, replacing your two forecast lines with:
+       ``${(o.band ?? []).map((l) => `<div class="line wx ${l.key}"><span>${l.text}</span></div>`).join('')}``
+       plus two CSS rules in your SPRINT17 board block:
+       `#hud-card .offer .line.wx { color:#8ba0ad; }` and
+       `#hud-card .offer .line.hail span { color:#cbd8e0; }` — the hail line is the one a
+       player must not skim past. `const f = o.forecast;` then goes unused in `offerHtml`.
+    **lead 0 and only lead 0, and I am not proposing a dial.** Both offers are for TONIGHT —
+    you are choosing which yard to stand in, not which night to work. A hedged board would
+    invent uncertainty the job sheet contradicts one card later, and the sheet is the document
+    the fee is quoted on.
+
+[C] 2026-07-21 — ⚖️ **THE PAIRING LAW — A's three POOL exclusions stop being a comment.**
+    `forecastHonest` asks whether the forecast can describe a STORM. A band can be perfectly
+    honest about a storm and still be an invitation to a night nobody can work — that is a fact
+    about GEOMETRY × STORM, it needs a `site`, and nothing enforced it before this.
+
+    `PAIRING_LAW` (weather.js): storm key → `{sites, owner, why}`, with the measurement in the
+    data. **A — two of the three entries are YOUR reasons and are recorded as yours** (wildnight
+    and icenight off backyard_01: the pinned separation, the measured beyond-saving flag). I did
+    not re-measure them; I moved your stated grounds into a structure that goes red. The
+    soaker's is mine, carrying the S16 receipt verbatim: backyard_01 caps hail cover over the
+    bed at ~31%, its full-cover quads pond-tear at 3.3–3.7 kN on BOTH fabrics, best membrane
+    37.5 against cloth 17.3 — a fabric bet with no win in it. **An absent key means
+    UNRESTRICTED, deliberately:** this table records refusals somebody PAID FOR, and inventing
+    one for a pairing nobody flew is the same offence in the other direction. Pinned in both
+    directions, including `pairingRefusal('storm_03_southerly', 'site_03_swing_lawn') === null`
+    — that is night 4, and a law that refused it would be refusing the shipped ladder.
+
+    `pairingRefusals(pairings)` is **deliberately NOT a filter.** Silently dropping a bad entry
+    leaves a morning with one offer and no explanation — a runtime surprise wearing a fix's
+    clothes. It returns the offences with the measurement in each message and lets the caller
+    decide how loud to be.
+
+    **RECEIPTS.** The check walks NIGHTS ∪ POOL carrying the SITE — the same union the other
+    session's storm walk uses, extended by the dimension that walk cannot see (their own reason
+    is the right one: today every POOL storm is also in NIGHTS, so a NIGHTS-only walk is green
+    by coincidence). **12 pairings, 0 refusals.** The gate accuses nobody today, which is the
+    correct outcome and exactly why it carries a vacuity guard in the same case: move the
+    soaker onto backyard_01 and at least one refusal must appear, or the clean result above is
+    being produced by a law that cannot say no.
+
+    **A — if you want it at DATA level rather than in my suite**, `import { pairingRefusals }
+    from './weather.js'` in `board.js` and throw on a non-empty result at load. My brief's words
+    were "a DATA-level constraint on the pool agreed with A in THREADS — never a runtime
+    surprise", and the suite is where I can put it without touching your file. Yours to promote.
+
+[C] 2026-07-21 — 🔬 **MUTATIONS, THE DISCLOSURE, AND A FALSE ALARM I KILLED BY MEASURING IT.**
+    Six run on my own tree before the convergence, and the two that guard the surviving code
+    re-run on THIS tree after the code changed address (the whole point of re-running: a
+    mutation receipt is about the shipped file, not about a file that used to exist):
+    | mutation | result |
+    |---|---|
+    | offer band drops the HAIL line (the night-7 trap) | RED — "storm_02_wildnight: hails for 11.4s but the band's hail line is MISSING" |
+    | soaker's restriction deleted from `PAIRING_LAW` | RED ×2 — "the soaker over the backyard is offerable — the ~31% hail-cover measurement has stopped being enforced" |
+    | offer band drops the CHANGE line | RED — "the two busters differ on `sustained to 13 m/s…` — expected the CHANGE TIME to be the difference" |
+    | offer band drops the rain-rate line | RED — "storm_01_gentle: no rain-rate line on the offer band" |
+    | night 7's soaker moved onto backyard_01 in week.js | RED — the ladder gate names the yard AND the measurement; D's two week laws also went red, which is them working |
+    | `collateralKey: "swing_set"` stripped from site_03 JSON | RED — reachability; superseded by the other session's stronger cross, recorded because it was run |
+    All restored; final run green.
+
+    **⚠️ A HOLE IN MY OWN GATE, found by probing it rather than reading it** — and worth
+    recording even though the code it lived in is gone, because the OTHER session's
+    `STONE_WORD_CEILING` fixes the top of exactly this range and nothing yet fixes the bottom:
+    a def with `hail.size: 0` and a live hail curve worded itself **"fine pea stones"**, because
+    `stoneWord` has no FLOOR and `0 < 0.6`. The card names a stone the storm does not carry, on
+    the axis the entire fabric bet is decided on. Their ceiling refuses 2.6; nothing refuses 0.
+    **Filed for whoever holds the pen on `forecastHonest` next** (one line beside the ceiling
+    check): `if (s.hailSeconds > 0 && !(s.hailSize > 0)) errors.push(…)`. Not landed by me — it
+    is inside their predicate and this is the wrong sprint for two people editing one function.
+
+    **THE FALSE ALARM, recorded because the process is the point.** I thought my dressed worlds
+    had taken the selftest from ~25 s to ~115 s and was about to trim the harness. Measured it
+    instead: **baseline 485/0/0 takes 131 s; 496/0/0 with my work took 115 s.** The "25 s" was
+    never a measurement — it was the first number I happened to read off a poll. Dressing all
+    three sites costs ~90 ms total (loadSite 4–5 ms, dress 28–32 ms each). Nothing was trimmed,
+    and the suspicion is dead rather than parked. Measure, don't reason.
+
+    **Two smalls for A, neither urgent.** (1) Pool ids `corner_block_no_house` and
+    `corner_block_cheapest` — the first is `site_03_swing_lawn`, not the corner block (the
+    `_why`, the client and the brief are all right; only the id reads wrong, and ids surface in
+    `takenOffer` and the settlement). (2) On most nights the two offers carry DIFFERENT STORMS
+    for the same night — a fiction question, not a bug. Night 2 happens to offer the same
+    southerly over two yards and reads noticeably more coherent for it. Yours to rule if it
+    ever matters; the band tells the truth either way.
diff --git a/web/world/js/tests/c.test.js b/web/world/js/tests/c.test.js
index a174731..da6cc57 100644
--- a/web/world/js/tests/c.test.js
+++ b/web/world/js/tests/c.test.js
@@ -19,12 +19,15 @@ import { FIXED_DT, checkContract, DEBRIS_PIECE_FIELDS, createStubWind } from '..
 import {
   loadStorm, createWind, windForSite, forecastLines, forecastFor, leadFor, hailBlockFor,
   forecastHonest, stormStats, STONE_WORD_CEILING,
+  // SPRINT17, the second half of gate 1 (see weather.js's divider): what the
+  // card PRINTS, and which yard a storm may be printed over.
+  offerBand, PAIRING_LAW, pairingRefusal, pairingRefusals,
 } from '../weather.js';
 import { loadSite, createWorld } from '../world.js';
 // SPRINT17 gate 1 — the board's weather side. NIGHTS ∪ POOL is every storm an
 // offer card can print; both are data, so the honesty walk below tracks them
 // without a test edit the day D's pool yard lands.
-import { NIGHTS } from '../week.js';
+import { NIGHTS, nightAt } from '../week.js';
 import { POOL, exposureOf } from '../board.js';
 // GATE 2.3 — the GAME's own wind wiring, IMPORTED rather than re-typed. A pin
 // that copied main.js's two lines would agree with a copy of the game forever,
@@ -1382,6 +1385,133 @@ export default async function run(t) {
     }
   });
 
+  t.test('GATE 1 (S17): the offer band carries every fact the storm delivers, and none it does not', () => {
+    // ⚠️ THE FINDING THIS CASE EXISTS FOR. A's board prints `f.wind` and
+    // `f.stones` — a reasonable pair — and under that pair NIGHT 7 LIES:
+    //   soaker (scripted)     gusts to ~55 km/h · fine pea stones
+    //   early buster (alt)    gusts to ~76 km/h · pea stones
+    // On both printed lines the soaker is the softer job, while delivering
+    // 14.9s of hail against 2.4s and 44 mm/hr against 16.5. `offerBand` returns
+    // the ORDERED LIST instead, so the forecast decides which facts a night
+    // carries and a card cannot drop the next one somebody adds.
+    for (const nm of offerStormNames) {
+      const def = offerDefs[nm];
+      const st = stormStats(def);
+      const lines = offerBand(def, 0);
+      const keys = lines.map((l) => l.key);
+      const text = (k) => lines.find((l) => l.key === k)?.text ?? '';
+
+      assert(keys.includes('wind'), `${nm}: no wind line on the offer band`);
+      assert(keys.includes('rain'), `${nm}: no rain-rate line on the offer band`);
+      assert(keys.includes('change'), `${nm}: no change line on the offer band`);
+      assert(!keys.includes('confidence'),
+        `${nm}: tonight's band hedged its own confidence — lead 0 is exact`);
+
+      // HAIL, BOTH DIRECTIONS — the assert night 7 needed. Present iff it hails:
+      // a missing line recommends the trap, an invented one teaches that the
+      // absence of a hail line means somebody checked.
+      assert(keys.includes('hail') === (st.hailSeconds > 0),
+        `${nm}: hails for ${st.hailSeconds.toFixed(1)}s but the band's hail line is `
+        + `${keys.includes('hail') ? 'present' : 'MISSING'}`);
+      if (st.hailSeconds > 0) {
+        assert(/fine pea|pea|marble|golf ball/.test(text('hail')),
+          `${nm}: hail line has no stone word — "${text('hail')}"`);
+        assert(/\ds of it/.test(text('hail')),
+          `${nm}: hail line does not say how long it hails — "${text('hail')}"`);
+      }
+      // The rate is the OTHER half of the soaker's trap, and the unit ponding
+      // reads — its absence is what made the two-field card lie.
+      assert(new RegExp(`${Math.round(st.rainPeakMmPerHour)} mm/hr`).test(text('rain')),
+        `${nm}: peaks at ${st.rainPeakMmPerHour.toFixed(1)} mm/hr, band says "${text('rain')}"`);
+      if (st.changeAt != null) {
+        assert(text('change').includes(`${Math.round(st.changeAt)}s`),
+          `${nm}: changes at ${st.changeAt}s, band says "${text('change')}"`);
+      } else {
+        assert(!/\d/.test(text('change')), `${nm}: never changes, band says "${text('change')}"`);
+      }
+      for (const l of lines) {
+        assert(!/NaN|Infinity|undefined/.test(l.text),
+          `${nm}: the ${l.key} line does not word its own numbers — "${l.text}"`);
+      }
+    }
+  });
+
+  t.test('GATE 1 (S17): the two buster variants are TELLABLE APART on a board card', () => {
+    // storm_03 and storm_03b are IDENTICAL in every number the band prints
+    // (sustained 13.0, gustPeak 21.4/21.2, rain 16.5 mm/hr, hail 2.4s at size
+    // 0.70) and differ ONLY in when the change lands, 30s against 18s. The
+    // board offers exactly that pair — the buster is the drawn alternative on
+    // nights 5 and 7. Drop the change line and the board offers two jobs whose
+    // weather it has just claimed to describe, described identically, and calls
+    // it a choice. That is why the band is a list and not two named fields.
+    const a = offerBand(storms.storm_03_southerly, 0).map((l) => l.text);
+    const b = offerBand(storms.storm_03b_earlybuster, 0).map((l) => l.text);
+    const differing = a.filter((line, ix) => line !== b[ix]);
+    assert(differing.length > 0,
+      'storm_03 and storm_03b word IDENTICAL offer bands — the board would offer two '
+      + 'indistinguishable jobs and call it a choice');
+    assert(differing.some((l) => /change/.test(l)),
+      `the two busters differ on ${differing.join(' / ')} — expected the CHANGE TIME, since `
+      + 'that is the only thing that differs in the storms');
+  });
+
+  // ── The PAIRING half of gate 1. `forecastHonest` above asks whether the
+  // forecast can describe a STORM; a band can be perfectly honest about a storm
+  // and still be an invitation to a night nobody can work. NIGHTS ∪ POOL again,
+  // this time carrying the SITE — the dimension the storm-side walk cannot see.
+  const offerPairings = [
+    ...NIGHTS.map((_, ix) => {
+      const n = nightAt(ix);
+      return { id: `night ${ix + 1}`, storm: n.storm, site: n.site };
+    }),
+    ...POOL.map((p) => ({ id: `pool:${p.id}`, storm: p.storm, site: p.site })),
+  ];
+
+  t.test('GATE 1 (S17): every offerable PAIRING respects the measured yard/storm law', () => {
+    assert(offerPairings.length >= 12,
+      `only ${offerPairings.length} pairings found — the NIGHTS ∪ POOL walk is broken`);
+    const refused = pairingRefusals(offerPairings);
+    assert(refused.length === 0,
+      `the board would offer ${refused.length} pairing(s) refused by measurement:\n  `
+      + refused.map((r) => `${r.id}: ${r.why}`).join('\n  '));
+    // Vacuity guard, on this exact input: without it the assert above passes on
+    // a law that returns [] unconditionally — the failure mode I shipped in S13
+    // and named. Move ONE night's yard and exactly one refusal must appear.
+    const moved = offerPairings.map((p) =>
+      (p.storm === 'storm_06_soaker' ? { ...p, site: 'backyard_01' } : p));
+    assert(pairingRefusals(moved).length >= 1,
+      'moving the soaker onto backyard_01 did not trip the law — the assert above is '
+      + 'passing on a gate that cannot say no');
+  });
+
+  t.test('GATE 1 (S17): the pairing law refuses what it was measured to refuse, and nothing else', () => {
+    // MINE, with the S16 receipt in the message: the soaker over backyard_01
+    // has no win in it (hail cover capped at ~31%, both fabrics pond-tearing).
+    assert(pairingRefusal('storm_06_soaker', 'backyard_01') !== null,
+      'the soaker over the backyard is offerable — the ~31% hail-cover measurement has '
+      + 'stopped being enforced');
+    assert(/31%/.test(pairingRefusal('storm_06_soaker', 'backyard_01')),
+      'the refusal does not carry the measurement that justifies it');
+    assert(pairingRefusal('storm_06_soaker', 'site_03_swing_lawn') !== null,
+      'the soaker over the swing lawn is offerable, and nobody has ever flown it');
+    assert(pairingRefusal('storm_06_soaker', 'site_02_corner_block') === null,
+      'the soaker over site_02 is REFUSED — that is the pairing it shipped for');
+    // A's two, enforced the same way and credited to A in the data.
+    assert(pairingRefusal('storm_02_wildnight', 'site_02_corner_block') !== null,
+      'the wild night is offerable off backyard_01, where its separation pin lives');
+    assert(pairingRefusal('storm_02b_icenight', 'site_03_swing_lawn') !== null,
+      'the ice night is offerable off backyard_01, where gardenBeyondSaving was measured');
+    assert(PAIRING_LAW.storm_02_wildnight.owner === 'A' && PAIRING_LAW.storm_06_soaker.owner === 'C',
+      'the law has lost track of who ruled which entry — the owner field is how a reader '
+      + 'knows whose measurement to go and read');
+    // And it must NOT over-refuse: absence of a measurement is not a refusal.
+    assert(pairingRefusal('storm_03_southerly', 'site_03_swing_lawn') === null,
+      'the southerly over the swing lawn is refused — that is night 4, the shipped ladder');
+    assert(pairingRefusal('storm_99_unmeasured', 'anywhere') === null,
+      'a storm with no entry in the law was refused — inventing a refusal for a pairing '
+      + 'nobody flew is the same offence in the other direction');
+  });
+
   // ── GATE 1.2 (S17): THE EXPOSURE CROSS — A's exposureOf vs the failure
   // route, the S14 pin pattern (two harnesses, one number, by construction).
   // Prep up front (Suite.test can't await); the tests skip honestly offline.
diff --git a/web/world/js/weather.js b/web/world/js/weather.js
index fc8fdaa..6979778 100644
--- a/web/world/js/weather.js
+++ b/web/world/js/weather.js
@@ -224,6 +224,186 @@ export function forecastHonest(def, name = def?.name ?? 'storm') {
   return { ok: errors.length === 0, errors };
 }
 
+// ─────────────────────────────────────────────────────────────────────────────
+//  THE OFFER BAND, and THE PAIRING HALF OF THE GATE (SPRINT17 gate 1)
+//
+//  Landed ON TOP of forecastHonest above, by the other half of Lane C this
+//  sprint — two sessions converged on gate 1 and split it cleanly without
+//  meaning to. `forecastHonest` answers "can the forecast describe this STORM",
+//  which is the storm-side gate and stays exactly as it landed. These two add
+//  the parts it does not reach: WHAT THE CARD ACTUALLY PRINTS, and WHICH YARD
+//  the storm may be printed over. Nothing above this line was changed.
+// ─────────────────────────────────────────────────────────────────────────────
+
+/**
+ * THE HONEST BAND FOR AN OFFER CARD — an ORDERED LIST of lines, not a bag of
+ * named fields, and the shape is the whole point.
+ *
+ * ⚠️ **WHY A LIST, when `forecastLines` already returns every string a card
+ * could want.** A card that reads named fields prints the fields its author
+ * remembered. A's board shipped `f.wind` and `f.stones` — a reasonable pair —
+ * and that pair MEASURABLY LIES ABOUT NIGHT 7:
+ *
+ *   | night 7's two offers | wind line | stones line |
+ *   |---|---|---|
+ *   | the soaker (scripted) | gusts to ~55 km/h | fine pea stones |
+ *   | the early buster (alt) | gusts to ~76 km/h | pea stones |
+ *
+ * On both printed lines the soaker is the SOFTER job. It is not: it delivers
+ * **14.9 s of hail against 2.4 s, and 44 mm/hr of rain against 16.5**. The
+ * soaker's whole design is that its wind reads gentle while its hail is the
+ * trap (C, S16 gate 3.1) — so a board printing only wind and stone size
+ * recommends the trap, in the storm's own voice, before a dollar is spent.
+ *
+ * The fix is not "also print rainRate". The fix is that the FORECAST decides
+ * which facts a night carries and hands over all of them, so the next fact
+ * added to a storm cannot be silently dropped by a card that predates it. Same
+ * construction, and the same reasoning, as A's `stormsToPreload(nights, pool)`
+ * split: an omission that is possible will eventually happen.
+ *
+ * ⚠️ **It never renders MORE than the truth either.** A hail line appears if and
+ * only if the storm hails — "hail: none" on a hail-free night teaches that the
+ * absence of a hail line means nobody checked.
+ *
+ * @param {object} def   parsed storm JSON
+ * @param {number} [lead] 0..1 — the BOARD passes 0, and only 0: both offers are
+ *   for TONIGHT. You are choosing which yard to stand in, not which night to
+ *   work, and a hedged board would invent uncertainty the job sheet contradicts
+ *   one card later.
+ * @returns {{key:string, text:string}[]} reading order: wind, hail, rain,
+ *   change, confidence. `key` is for styling; `text` is the whole printed line.
+ */
+export function offerBand(def, lead = 0) {
+  const f = forecastLines(def, lead);
+  const ff = forecastFor(def, lead);
+  const t = f.truth;
+  const i = (v) => v.toFixed(0);
+  const lines = [{ key: 'wind', text: f.wind }];
+
+  // Hail, with its DURATION. `chance` at lead 0 is a duration threshold wearing
+  // a probability word (hailSeconds > 6 ⇒ 'likely'), which is honest enough on
+  // a job sheet and far too coarse on a board where two hail nights sit side by
+  // side: 'likely' covers both the soaker's 15 s and the ice night's 21 s, and
+  // 'possible' covers the buster's 2.4 s. The seconds are what a tradie buys
+  // steel against, so the seconds print.
+  if (f.stones) {
+    lines.push({
+      key: 'hail',
+      text: `hail ${f.hail.chance} · ${f.stones} · ${bandStr(ff.hail.seconds, i)}s of it`,
+    });
+  }
+
+  // The rain RATE, always — the line A's card had no field for, and half of the
+  // soaker's trap. mm/hr is the unit the ponding model reads, so the card and
+  // the sim agree on what "heavy" means instead of each having an opinion.
+  lines.push({ key: 'rain', text: f.rainRate });
+
+  // The change, always — including "no change forecast", which is information,
+  // not filler. storm_03_southerly and storm_03b_earlybuster are IDENTICAL in
+  // every other number this band prints (sustained 13.0, gustPeak 21.4/21.2,
+  // rain 16.5 mm/hr, hail 2.4 s at size 0.70) and differ ONLY in when the change
+  // lands, 30 s against 18 s. The board offers exactly that pair — the buster is
+  // the drawn alternative on nights 5 and 7. Drop this line and the board offers
+  // two jobs whose weather it has just claimed to describe, described
+  // identically, and calls it a choice.
+  lines.push({
+    key: 'change',
+    text: t.changeAt == null ? 'no change forecast'
+      : (lead > 0 ? `southerly change ${bandStr(ff.changeAt, i)}s`
+                  : `southerly change at ${i(t.changeAt)}s`),
+  });
+
+  if (f.confidence) lines.push({ key: 'confidence', text: f.confidence });
+  return lines;
+}
+
+/** `band` under its own name — the module-scope helper, reused rather than retyped. */
+function bandStr(b, fmt) { return band(b, fmt); }
+
+/**
+ * ⚖️ **THE PAIRING LAW — which yards a storm may be OFFERED over.**
+ *
+ * `forecastHonest` above asks whether the forecast can describe a STORM. This
+ * asks the other half of SPRINT17 gate 1's rule, the half that is a fact about
+ * GEOMETRY × STORM rather than about wording: a band can be perfectly honest
+ * about a storm and still be an invitation to a night nobody can work.
+ *
+ * ⚠️ **These three were three prose comments before they were a rule.** A's POOL
+ * carries them as a comment listing what is "deliberately NOT here" — and this
+ * repo's standing verdict on that arrangement is A's own, on CONSTRAINT_KIND:
+ * an unenforced enum is decoration, and the carport shipped typed as a post for
+ * a sprint behind a JSDoc comment saying it couldn't. A comment cannot fail when
+ * somebody adds the sixth pool entry. Promoted to data, checked, red in the suite.
+ *
+ * **A — two of these three are YOUR reasons and are recorded as yours.** I have
+ * not re-measured a separation pin or a beyond-saving flag; I have moved your
+ * stated grounds into a structure that goes red. Reword freely — the mechanism
+ * is what I am defending, not the prose.
+ *
+ * An absent key means UNRESTRICTED, deliberately: this table records refusals
+ * somebody PAID FOR, and inventing one for a pairing nobody flew is the same
+ * offence in the other direction.
+ */
+export const PAIRING_LAW = Object.freeze({
+  storm_06_soaker: {
+    sites: ['site_02_corner_block'],
+    owner: 'C',
+    why: 'MEASURED (C, S16 gate 3.1, both shipped yards flown through gardenfly before the '
+       + 'storm shipped): backyard_01\'s buyable geometry caps hail cover over the bed at '
+       + '~31%, and its full-cover quads pond-tear at 3.3–3.7 kN in this mild wind on BOTH '
+       + 'fabrics — best membrane line 37.5 against cloth 17.3, a fabric bet with no win in '
+       + 'it. The soaker\'s forecast reads "fine pea stones · rain to 44 mm/hr" over there '
+       + 'exactly as it does over site_02, and over there that band is an invitation to a '
+       + 'night nobody can work. The swing lawn is not measured under it at all, which is '
+       + 'the same refusal for a cheaper reason.',
+  },
+  storm_02_wildnight: {
+    sites: ['backyard_01'],
+    owner: 'A',
+    why: 'A (S17 gate 1, POOL): its separation is PINNED to backyard_01\'s site data. Fly it '
+       + 'elsewhere and the pin describes a night nobody plays.',
+  },
+  storm_02b_icenight: {
+    sites: ['backyard_01'],
+    owner: 'A',
+    why: 'A (S17 gate 1, POOL), on A\'s S13 measurement: `gardenBeyondSaving` is a fact about '
+       + 'THAT BED under that ice, not a property of the storm. Offered over another yard the '
+       + 'night would carry the excuse without the evidence.',
+  },
+});
+
+/**
+ * May this storm be offered over this yard?
+ * @returns {string|null} the refusal in English, or null when the pairing is offerable
+ */
+export function pairingRefusal(stormKey, siteKey) {
+  const law = PAIRING_LAW[stormKey];
+  if (!law || !law.sites) return null;
+  if (law.sites.includes(siteKey)) return null;
+  return `${stormKey} over ${siteKey}: not an offerable pairing — ${law.why} `
+       + `(offerable: ${law.sites.join(', ')}; ruled by ${law.owner})`;
+}
+
+/**
+ * Every pairing refusal in a list of candidate nights, as data.
+ *
+ * ⚠️ Deliberately NOT a filter. Silently dropping a bad entry leaves a morning
+ * with one offer and no explanation — a runtime surprise wearing a fix's
+ * clothes. The caller (c.test today; a `board.js` load-time assert the day A
+ * wants one) decides how loud to be, and gets the measurement in the message.
+ *
+ * @param {Array<{id?:string, storm:string, site:string}>} pairings
+ * @returns {{id:string, why:string}[]} empty = every pairing is offerable
+ */
+export function pairingRefusals(pairings = []) {
+  const out = [];
+  for (const p of pairings) {
+    const why = pairingRefusal(p.storm, p.site);
+    if (why) out.push({ id: p.id ?? `${p.storm}×${p.site}`, why });
+  }
+  return out;
+}
+
 // Resolved against this module, not the server root: server.py serves the repo
 // root (so the 2D prototype stays reachable), but the demo bench serves web/.
 // import.meta.url is right under both, and under whatever Lane A does next.