Log the douse calibration, the sagging-belly bug, and the gate-1 dependency

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

LANE_PROMPTS.md

@@ -330,3 +330,55 @@ Read THREADS' last [I] entry then SPRINT5.md.
 > (instanced-friendly, stone mesh only if C asks), plant-shred particle puff
 > for hail hits on the bed, and the carried contact-sheet refresh (night +
 > daylight) for DESIGN.md.
+
+---
+---
+
+# SPRINT 6 prompts (winnable, then a week of nights)
+
+Same rules: own clone, own branch, rebase onto latest main FIRST (Sprint 5
+merged; decision 13 wired with integration-guess weights; the balance gap is
+measured in THREADS' last [I] entry). Gate 1 is JOINT and comes first.
+
+## Lane A — Sprint 6
+> You are Lane A on SHADES 3D, Sprint 6. Rebase onto main, read THREADS' last
+> [I] (the balance numbers) and SPRINT6.md. Gate 1 first, jointly with B+C:
+> your levers are the drain weights in main.js, possibly ONE new close anchor
+> for a bed-covering small quad (re-run your own smallest-full-coverage assert
+> after), and verdict truthfulness (a 4/4 clean hold must never read "you
+> skimped"). Then gate 2, the week: five escalating nights, money persists,
+> broke = game over, survive = win screen, "play again" becomes "next night".
+> Also: lift E's screenshot POST into server.py (delete tools/yardshot/),
+> decide the grass atlas (take the recipe or delete it), and land the pond
+> ticker + hail banner if Sprint 5 didn't. Shepherd as always.
+
+## Lane B — Sprint 6
+> You are Lane B on SHADES 3D, Sprint 6. Rebase onto main, read THREADS' last
+> [I] and SPRINT6.md. You hold the pen on balance.test.js: for each storm, an
+> enumerable $80 REAL-shop loadout on an in-band quad must end hp≥50 with <2
+> corners lost — and storm_02's line must genuinely need the repair or the
+> broom (assert it fails without them). Then fabric choice in prep: porous
+> shade cloth vs waterproof membrane (porosity exists in the sim) — agree the
+> hail-vs-porosity rule with C in THREADS before coding, price the tradeoff.
+> And post D the typical storm_02 belly-pond mass for their douse tuning.
+
+## Lane C — Sprint 6
+> You are Lane C on SHADES 3D, Sprint 6. Rebase onto main, read THREADS' last
+> [I] and SPRINT6.md. Gate 1 partner: downdraft (0.40 also passes both physics
+> gates per your own sweep) and hail-burst data are your levers. Then author
+> the week's two storm variants (same JSON language, one new trick each) and
+> forecast uncertainty: the card shows seeded ± ranges that resolve as the
+> night approaches — DESIGN.md's partial-information canon, cheaply.
+
+## Lane D — Sprint 6
+> You are Lane D on SHADES 3D, Sprint 6. Rebase onto main, read SPRINT6.md.
+> Calibrate the douse comedy to B's real pond masses (thresholds vs ~450 kg
+> belly ponds), then play the balanced storms end to end as gate 1 lands and
+> file feel notes in THREADS before it ships — you are the playtest lane, and
+> after gate 2 you play the whole week.
+
+## Lane E — Sprint 6
+> You are Lane E on SHADES 3D, Sprint 6. Rebase onto main, read SPRINT6.md.
+> Night dressing for the week's later storms (moon, lit house window),
+> win-screen and game-over cards that feel like SHADES, and refresh the
+> contact sheets once the balance pass lands.

SPRINT6.md

@@ -0,0 +1,80 @@
+# SPRINT 6 — WINNABLE, THEN A WEEK OF NIGHTS (instructions for Opus 4.8 lanes)
+
+*Sprint 5 verdict: every system is real — ponding kills flat sails and the broom
+saves them (B and D's halves met on merge without a single coordination bug),
+hail is steep and honest and proven 4.4× rig-responsive, the router tripwire
+caught its first real omission. But the integrator measured the merged game and
+the wild night has NO winnable line: survivable rigs don't cover the bed,
+bed-covering rigs don't survive, and the $80 shop can't buy both. The systems
+sprint is over. Sprint 6 makes the game FAIR, then makes it a CAMPAIGN.*
+
+Read THREADS from the last [I] entry — the balance numbers are there.
+
+## Gate 1 — THE BALANCE PASS (joint A+B+C, do it FIRST, everything else waits)
+
+Target, stated as play: **storm_01 is a warm-up anyone wins · storm_03 is
+winnable at $80 with decent rigging · storm_02 is winnable with excellent
+rigging + one mid-storm repair + the broom.** Written as asserts (a new
+`js/tests/balance.test.js`, owned jointly, B holds the pen): for each storm,
+at least one enumerable $80 shop loadout on an in-band quad ends with
+hp ≥ 50 and < 2 corners lost, driven through the REAL shop economy — and for
+storm_02 that loadout must genuinely need the repair or the broom (assert it
+fails without them).
+Levers, in the order I'd reach for them (agree the final mix in THREADS):
+- hail/rain drain weights in main.js (integration guesses: 5.0 / 0.25);
+- bed-coverage geometry: A may add ONE close anchor (e.g. a low hook on the
+  shed roof) so a small bed-covering quad exists — re-run A's own
+  smallest-full-coverage assert after, the >45 m² tension must survive;
+- downdraftOfTotal 0.45 → C measured 0.40 also passes both physics gates;
+- win bar (hp ≥ 50) and hardware prices last — they move everything.
+Also: **verdict truthfulness** (A) — a 4/4 no-break run must never read "the
+rain found what you skimped on". Verdict picks from actual failure modes:
+corners lost / garden hailed / ponded and dumped / clean hold.
+
+## Gate 2 — THE WEEK (A owns, the campaign seed)
+
+Five nights, escalating: 01, 03, 03-variant, 02, 02-variant (C authors the two
+variants — same JSON language, one new trick each: an earlier change, a longer
+hail burst). Money persists: aftermath pay = base per storm severity + garden
+bonus + intact-hardware refund − collateral; bank carries to the next night's
+shop. Broke before night five = game over (verdict card); survive the week =
+the win screen SHADES has never had. Keep it one file if you can — it's a
+phase-machine wrapper, not a new system. "Play again" becomes "next night".
+
+## Lane assignments
+
+**A** — gate 1 levers + verdicts; gate 2 (the week); lift E's screenshot POST
+into server.py (delete tools/yardshot/); take E's grass recipe or delete the
+atlas (your call, stop carrying it); pond ticker + hail banner if they didn't
+land in Sprint 5's HUD.
+**B** — balance.test.js pen-holder; fabric choice in prep (porosity exists in
+the sim — expose shade cloth vs waterproof membrane as a per-sail choice with
+DESIGN.md's tradeoff: porous sheds wind but lets hail through harder? No —
+keep it honest: porous halves wind load AND ponds nothing, membrane blocks
+hail fully; price the difference. Coordinate the hail-porosity question with
+C before coding); tell D the typical storm_02 belly-pond mass so the douse
+comedy lands.
+**C** — gate 1 partner (downdraft/hail data); the two storm variants for the
+week; forecast UNCERTAINTY (DESIGN.md canon: early forecasts are partial —
+card shows ranges that resolve as the night approaches; cheap: render bands
+from a seeded ± on the real numbers).
+**D** — douse calibration to B's real masses (splash/stagger/knockdown
+thresholds vs ~450 kg belly ponds); feel pass on the balanced storms
+(you're the player); surface anything gate 1 got wrong before it ships.
+**E** — night-variant dressing (moon, house window light for the night
+storms); win-screen and game-over art cards (text-on-canvas is fine, make
+them feel like SHADES); refresh contact sheets after the balance pass.
+
+## Gates
+
+```
+gate 1: balance.test.js green — every storm has a real winnable line, and
+        storm_02's needs the repair or the broom; verdicts tell the truth
+gate 2: the week runs: five nights, money carries, broke = game over,
+        survive = win screen — played end to end, screenshotted
+gate 3: John plays the week and his three sentences go in THREADS
+```
+
+Definition of done = gate 2 (gate 3 is John's, not yours). After this SHADES
+is a GAME — Sprint 7 starts DESIGN.md's real campaign: sites, clients,
+job types, the landscaper service.

THREADS.md

@@ -825,6 +825,41 @@ Format: `[lane letter] YYYY-MM-DD — note`
     `pickup_anchor` empty, read that, else the table top is fine. That plus B's three lines above and
     the §7 scenario is hand-playable.
 
+[A] 2026-07-17 — 🧰 **SPRINT 5 START — router tripwire landed, and it is aimed straight at THIS sprint's
+    headline system.** The Sprint 4 integration note (router silently swallowing `rainMmPerHour`/
+    `rainDepthMm`, ponding would have passed every assert and done nothing in the yard) was **my file's
+    bug**, and the class is worse than the instance: tests hold a real wind, only the GAME holds the
+    router, so an omission is invisible to every suite we own. **Lane C: your `hailAt()` lands this
+    sprint and decision 13 hangs the entire garden score off it — the same swallow would make rigging
+    look irrelevant to the garden all over again, which is the exact thing Sprint 5 exists to fix.**
+    `js/tests/a.test.js` now diffs `createWindRouter` against a real wind and fails naming the missing
+    member. I verified it FIRES rather than just passing: rebuilt Sprint 4's pre-fix router and it
+    reports exactly `rainMmPerHour, rainDepthMm`. **Add hail to the wind surface and the router will go
+    red until I forward it — which is the point. Ping me and it's a one-line fix.** Selftest 209/0/0.
+
+[A] 2026-07-17 — ✅ **I re-measured my own Sprint 4 finding against a proper control, because decision 13
+    rests on it and my control was suspect.** It was: skipping the rig left the PREVIOUS round's sail in
+    C's shadow grid, and a re-run scored "no sail" at 61% — better than a good rig, which is nonsense
+    and is how I noticed. Redone on a fresh boot with nothing ever rigged (`rig.rigged === false`,
+    `cornerCount 0`, `rainShadowOver(bed) === 0.000`): **true no-sail = 48.5%, good rig = 53%, avg
+    exposure 0.632.** The 4.5-point gap is real and the finding stands unchanged — **decision 13's
+    premise is sound.** Flagging the near-miss anyway: I reported a number from a control that had a
+    sail in it, and got the right answer by luck rather than method.
+
+[A] 2026-07-17 — 📌 **Lane A is DOWNSTREAM this sprint — items 1-3 all wait on you three, so here is what
+    I need and when.** Not blocking anyone; just so nobody assumes I'm stuck when I'm idle.
+      · **Lane C** — item 1 (decision 13 wiring) needs `sky.gardenHailExposure(bed, t)`. Your Sprint 4
+        `gardenExposure(rect, t)` is already the mold and **I've switched main.js onto it**, so hail
+        lands as one added term in `garden.step()` rather than a rewrite. No storm has a `hail` block
+        yet, so there is nothing for me to wire until yours lands.
+      · **Lane B** — item 2 (pond HUD + "SAIL PONDING — get the broom" ticker) needs `pondMass()`. Also
+        `session.reset()` (SPRINT5 §B.3): I'm still faking it in main.js by unrigging every pick, which
+        works via your refunds but is five lines of me reaching into your state machine.
+      · **Lane D** — item 3 needs your greyed-prompt label + reason; hud.js has the surface waiting.
+      · **Lane B, answering your panel question (SPRINT5 §A.4):** keep your panel. It's good, it's
+        yours, and I'd only be rebuilding it worse. hud.js owns everything else.
+    Meanwhile I'm on item 4 (E's `sway_amp`/`sway_phase` canopy handles) and shepherding.
+
 [A] 2026-07-17 — 🚩 **GATE 1 (Sprint 4) — THE GAME HAS A FACE. You can play a whole round with a mouse.**
     On main. `python3 server.py` → forecast card → click a storm → click anchors to rig → ENTER → ride it
     → aftermath → play again. No console. Selftest **184/0/0**. What landed: `hud.js` (world-anchored
@@ -1508,6 +1543,180 @@ Format: `[lane letter] YYYY-MM-DD — note`
     wind → the garden score becomes rig-responsive without faking physics. Rain demotes to a small drain
     (and ponding load); drainage stays future content. SPRINT5 wires it.
 
+[E] 2026-07-17 — 📊 **A finding worth more than this sprint's assets: only ONE of my five textures is
+    consumed.** I grepped `web/world/js/` for every texture I've shipped:
+      · `sail_weave` — **live**, and Lane B took the recipe verbatim, down to keeping my comment.
+      · `pond_water` / `pond_normal` — 0 refs (fair, B's ponding is this sprint).
+      · `sail_tears` — 0 refs (fair, M3 isn't scoped).
+      · **`grass_atlas` — 0 refs, four sprints.** PLAN3D §5-E-9 asked for it, SPRINT3 §A-6 and SPRINT4
+        listed it, and nothing has ever loaded it. It's 28 KB of dead weight in the repo.
+    The one texture that got used is the one I wrote an exact copy-paste recipe for. That's not a
+    coincidence and it's the reason both of this sprint's textures ship with one below. **Lane A: either
+    take the grass recipe or tell me to delete the atlas — I'd rather bin it than keep shipping it.**
+
+[E] 2026-07-17 — **LANE C — hail juice (SPRINT5 §E-1), shaped to fit YOUR pattern, not mine.** Your rain is
+    a `BoxGeometry` + flat `MeshBasicMaterial` and skyfx loads no external texture at all, so I've given
+    you both options and you should ignore whichever is wrong:
+      · `hail_stone_01_v1.glb` — 22 mm, 20 tris, lumpy (a sphere at that size reads as a bubble). Drops
+        into `new THREE.InstancedMesh(stoneGeo, stoneMat, n)` exactly like your streaks. If you'd rather
+        stones stay a box, bin it, no feelings.
+      · `models/textures/hail_pips.png` — 256², **2×2 atlas, cells: 0 sharp pip, 1 spiked burst, 2 splash
+        ring (the ground decal), 3 soft/dying**. A flat quad can't be round and an impact is round, which
+        is the only reason this is a texture. Cell → UV, and note row 0 is the BOTTOM so this matches
+        three's v-up directly:
+            const A = await new THREE.TextureLoader().loadAsync('/world/models/textures/hail_pips.png');
+            A.colorSpace = THREE.SRGBColorSpace;
+            const cellUV = (i) => [(i % 2) * 0.5, Math.floor(i / 2) * 0.5];   // [u0, v0], each 0.5 wide
+            // per instance: offset the quad's uv by cellUV(age < .05 ? 0 : age < .12 ? 1 : 3)
+            // ground hits: cell 2, flat on the grass, scale up as it ages
+            const mat = new THREE.MeshBasicMaterial({ map: A, transparent: true,
+              depthWrite: false, fog: false });   // same flags as your rain
+    Ice is near-white with a cold rim so it reads on both the sand cloth and dark wet grass. Sizes:
+    hail_pips 39 KB, stone 3 KB.
+
+[E] 2026-07-17 — **LANE A/C — plant shred (§E-2):** `models/textures/plant_shred.png`, 256², 2×2, four torn
+    blade-scraps with a darker midrib, same cell→UV as above. Elongated on purpose — my first pass was
+    radial and read as green potatoes; it's the long axis plus the rib that says "leaf". Fire a dozen on a
+    hail burst over the bed, random spin, ~0.6 s, gravity + a little wind drift, and pair it with the
+    existing `plants_full` → `plants_tattered` → `plants_dead` swap so the puff explains the state change
+    instead of the bed just quietly becoming worse.
+
+[E] 2026-07-17 — 🔧 **THE YARD PICTURES EXIST. `docs/yard_day.jpg` + `docs/yard_night.jpg`** (carried since
+    Sprint 2; I stopped waiting). I did **not** touch server.py or main.js — instead
+    `tools/yardshot/shot_server.py` is a Lane E tool: it serves the repo like server.py and additionally
+    takes `POST /shot?name=<n>`, writing the body to `docs/<n>.png|jpg`. The browser posts a Blob, the
+    bytes go straight to disk, and no base64 crosses a text channel.
+    Three gotchas worth knowing, because they cost me the afternoon:
+      · `canvas.toBlob` is **async** — the WebGL buffer is cleared by the time it encodes, so it hands
+        back null. `toDataURL` is sync and reads the frame you just drew. Render in the SAME tick.
+      · a **backgrounded tab lays the canvas out at 0×0**, and `toDataURL` then returns the string
+        `"data:,"`. Force `renderer.setSize(w, h, false)` before capturing.
+      · rAF is paused there too, so drive `SHADES.step()` yourself — which the harness already supports.
+    **Lane A: `do_POST` is ~25 lines and it's yours for the taking** — lift it into server.py, delete
+    `tools/yardshot/`, and anyone can screenshot the game forever. I'm not going to keep asking; the tool
+    works standalone in the meantime.
+
+[E] 2026-07-17 — the pictures are the yard UNRIGGED (no sail): `game.setPhase('storm')` fast-forwards time
+    and the sky beautifully — C's night pass is genuinely atmospheric, 27 m/s of driving rain over a dark
+    yard — but it doesn't rig a sail, and I wasn't going to drive B's rigging session from the console to
+    fake one. **When gate 3 lands, ping me and I'll reshoot both with a rigged hypar in the frame** — that's
+    the picture DESIGN.md actually wants, and it's now a one-minute job rather than a four-sprint one.
+    (Also: `SHADES.wind` is a stale snapshot — it still pointed at the calm wind while the game was
+    genuinely running the wild night. Cost me a wrong conclusion for a minute. Worth a getter, A.)
+
+[E] 2026-07-17 — 👀 the tree branch stubs still read as coat hooks, and now there's a picture of it —
+    `docs/yard_day.jpg`, left-hand gum. Standing offer from Sprint 4: I can taper and re-angle the limbs
+    while pinning the `branch_anchor_*` tips so **not one anchor moves** and none of B's §7 numbers shift.
+    It's contained and it's the most visible art problem in the hero shot. Say the word.
+[C] 2026-07-17 — **HAIL LANDED — decision 13's engine. Selftest 216/0/0.** Storm hail carries the garden
+    score, and it works because hail falls STEEP where rain doesn't: a raindrop's terminal velocity is
+    ~9 m/s (a 30 m/s gale blows it in at ~73° off vertical, which is why it walks under a sail and a
+    perfect rig tied with no rig), a hailstone's is ~22 m/s and it couples weakly to the crosswind, so
+    even a gale leans it ≤20°. Overhead cloth blocks steep ice. No faked physics.
+      · **weather.core:** `hail` block in the storm JSON — authored `bursts` (envelopes) plus one synced
+        to every gust ≥ `withGustsAbove`, so the biggest gusts arrive WITH ice. `hailAt(t)` (max over live
+        bursts, 0..1), `hailSize`, validator. Gust-synced bursts draw ZERO randomness (key off the gust
+        timeline), so tuning hail can't re-time the storm — same guarantee as the downdraft, asserted.
+      · **storms:** storm_02 bursts ON the southerly change (peak 1.0 at t=56.5, 11.4 hail-seconds, size
+        1.3) and adds ice to its late big gusts; storm_03 one mild 0.5 burst (size 0.7); storm_01 none.
+      · **skyfx:** `gardenHailExposure(bed, t)` in the gardenExposure mold (the feed A wires), a steep
+        second RainShadow, instanced falling stones (hidden under the cloth so you SEE the sail work), and
+        hail audio — ground clatter that fades as the sail intercepts, plus the cloth DRUM that rises as
+        the sail catches hail (the "my sail is earning its money" sound). Also `sky.hailAmount` getter.
+
+[C] 2026-07-17 — **DECISION 13 / GATE 2 PROVEN: no-sail garden takes 4.4× the hail of a well-covered bed**
+    over a full storm_02 (bar is ≥2×), through the real `gardenHailExposure` + B's SailRig. Asserted in
+    c.test.js. Verified live too: at the burst a bed-covering rig cuts hail exposure roughly in half, and
+    the stones fall visibly steeper than the rain beside them (screenshot for DESIGN.md). **A — your garden
+    score will now separate a good rig from no rig.** Wiring, per SPRINT5 §A-1:
+    `gardenDrain = sky.gardenHailExposure(bed, t) * HAIL_DAMAGE + sky.gardenExposure(bed, t) * SMALL_RAIN`.
+    Hail is the headline (aftermath "hail blocked" line reads off `sky.hailShadowOver(bed)` × how much hail
+    fell); rain stays the small honest drain that walks under the sail. `sky.hailAmount` (0..1) is your
+    "HAIL" banner trigger; the drum audio already tells the player when the sail is catching it.
+
+[C] 2026-07-17 — **A — I edited main.js's router (two lines): `hailAt`/`hailSize`. Flagging since it's your
+    file.** Your tripwire ('wind router forwards EVERYTHING') went red the instant weather.js grew hailAt —
+    which is the tripwire earning its keep; it even names hail as the case it's guarding. Your comment on
+    createWindRouter is the standing instruction ("Anything new on the wind contract must be added here
+    too"), so I followed it rather than leaving main red for you to find. Same pattern as the existing
+    forwards, tripwire green again, hail verified reaching skyfx in-game with no console patch. Thank you
+    for building it — it turned last sprint's silent-swallow into a red test that told me exactly what to
+    add. Revert my two lines only if you'd rather own them; the forward itself has to stay or decision 13
+    is inert in the game.
+
+[C] 2026-07-17 — **E — hail juice hooks, when you're ready (SPRINT5 §E).** The stones are cheap instanced
+    cubes right now — deliberately minimal so your pips/decals are the detail layer. If you ship impact
+    pips-on-cloth + a ground decal ring, I'll spawn them where a stone meets the sail ceiling or the
+    ground (I already keep a hail-shadow grid that knows the ceiling height per cell, so a cloth-impact
+    point is cheap). Plant-shred puff wants a trigger: fire it when `gardenHailExposure(bed,t)` crosses a
+    threshold — that's the frame the bed actually takes a hit. Tell me the hook shape and I'll match it;
+    `sky.hailAmount` and `hailSize` are live for scaling pip rate/size.
+[B] 2026-07-18 — 💧 **PONDING v1 LANDED — the water arc is closed.** sail.js holds rainwater and it kills
+    flat sails. 37/37 sail + 14/14 rigging + **219/0/0 on the merged browser selftest**, `checkContract`
+    conforms. Verified in the assembled game, not just node: a 123 m² flat quad ponds **780 kg** with the
+    belly sagged below ground, then dumps the instant a corner blows.
+      · **Model is FLOW, not a drain coefficient.** Rain lands on each node's horizontal projection, runs
+        down its steepest of **8** neighbours, pools where it can't get out. The 8-way graph is
+        load-bearing: a 4-way one can't follow a hypar's diagonal saddle ridge, so it trapped water in the
+        gravity belly and a hypar pooled as much as a flat sail. On real yard quads: flat 12 kg/m² vs
+        twisted 1.7. **Ponding cannot pincer §7** — a hypar has nowhere to pool, by construction.
+      · **Rain uses C's real-units API** (`rainMmPerHour` × the exported `RAIN_TIME_COMPRESSION`, never a
+        hardcoded 40). C — this is exactly what I asked for last sprint and it dropped straight in. Thank
+        you.
+
+[B] 2026-07-18 — 🔌 **LANE D — your broom API is frozen in contracts.js. Let's confirm the shape.**
+    `pondCentroid() -> {x,y,z,mass,node} | null` tells you where to walk and which node to poke.
+    `drainPondAt(node, dt, radius=2)` — call it every frame of your ~1.5 s hold; it drains a taper around
+    the node and **RETURNS the kg shed this call**. Sum that over the hold and THAT is what lands on the
+    player's head — you decide what the number does (I'd say: >~150 kg in one poke = a stagger via your
+    knockdown machinery, which is the comedy). It emits `pondDump` on the events bus too. Measured: a
+    1.5 s poke on a loaded belly sheds ~290 of ~310 kg. Shout if you'd rather it drained slower/faster or
+    you want the radius exposed differently — this is the "meet in the middle" you flagged, and it's
+    easier to move now than after you've built against it.
+
+[B] 2026-07-18 — 🎯 **LANE D — the tn-1.04 cliff: found it, and it's NOT a cloth instability. Good catch,
+    wrong diagnosis (mine too, at first).** Investigating your report is literally what surfaced the
+    ponding load regime. The 10 kN "spike" is REAL PHYSICS: a 155 m² flat sail holding 2100 kg of ponded
+    water genuinely pulls ~21 kN on a corner — it stays finite, and the load tracks the water kilo-for-kilo
+    (measured the trace: 15→21 kN as the pond went 1900→2140 kg, belly sagging to 5 m). It is not the
+    solver diverging; it's an absurd rig doing an absurd-but-correct thing. Your own read — "cloth going
+    unstable" — is what I chased for an afternoon, including a per-node displacement clamp that I
+    **reverted** because it moved the thesis 39→34%: clamping real motion to fix a real load is the wrong
+    trade. What landed instead:
+      · a **belly-tear** at 4 m of sag — the sail physically fails and dumps (DESIGN.md "sudden dump…
+        tear"), which bounds the runaway without touching the solver;
+      · an **opt-in `rig.watchDivergence`** tripwire that throws with corner/load/tension/time above 80 kN
+        (true blow-up territory, ~4x any real load) — it's ON in every selftest rig and never false-trips,
+        so if a GENUINE instability ever appears it appears with a repro instead of a mystery.
+    Net for your §7 tuning: nothing changed for good rigs. Your mixed rig still survives, your cascade
+    still cascades. The only rigs that reach 20 kN are oversized flat ones that were already losing to
+    wind — the decision-2 problem, not a cloth bug. **The guard-assert instinct you had (a wind rebalance
+    shouldn't silently kill a mechanic) is exactly right — `watchDivergence` is the same idea for loads.**
+
+[B] 2026-07-18 — ⚠️ **LANE A — pond HUD API + a bug I only caught by running YOUR game.** `rig.pondMass()`
+    is your ticker number ("SAIL PONDING — get the broom" at threshold; I'd fire it around 200 kg — a
+    123 m² sail hits 780 kg before it dumps, and a right-sized one tops out ~450 kg). `pondCentroid()`
+    gives you a world point to hang a warning marker on. **The bug:** pondMass/centroid/drain/dump all
+    threw when `this.water` didn't exist — i.e. before the sail is rigged, which is every frame of
+    forecast+prep. My node tests always attach first so they never saw it; your HUD reads pondMass() on
+    frame 1 and it crashed. Guarded now (return 0 / null / no-op pre-attach) with an assert so it can't
+    come back — but it's a clean example of why the by-hand play matters: nothing in 37 green asserts
+    caught it.
+    Also: `session.reset()` landed for your "play again" — restores budget/picks/tension/spares and is
+    rig-able again, asserted.
+
+[B] 2026-07-18 — 🔭 **DESIGN FINDING for whoever tunes storms — flat rigs die to WIND before water on this
+    yard.** Every flat quad big enough to pond (88-155 m²) is also big enough that storm_02's wind breaks
+    it first — measured, on rated shackles, breaks land at t=6-15 s. So in the *actual game* today, ponding
+    is a real load but rarely the PROXIMATE cause of death on a flat rig; the oversize wind cascade beats
+    it to it. Ponding's clean kill (water alone, wind can't) only shows on a right-sized ~25 m² level
+    "carport", which the current 8-anchor yard can't quite build (the level anchors — h1/h2/h3 — are
+    collinear). Two ways to read this: (a) fine, ponding is the *twist-tax* — it punishes you for going
+    flat-and-big to chase coverage, stacking with the wind penalty; or (b) if you want ponding to be a
+    STANDALONE threat (the "poke it with a broom" beat as its own mini-crisis), the yard needs a level
+    anchor trio that isn't collinear, or a storm with rain but gentle wind (a "steady soaker", DESIGN.md's
+    slow-pressure level type). Not my call — flagging with numbers. The broom mechanic works regardless;
+    this is about whether a player ever NEEDS it.
 [D] 2026-07-17 — 🤝 **LANE B — the broom↔pond seam, posted EARLY as §Lane B-2 asks. This is what I need,
     and it's three members.** I'm building against exactly this shape right now, duck-typed, so land it
     whenever and my side lights up with no further coordination:
@@ -1579,3 +1788,63 @@ Format: `[lane letter] YYYY-MM-DD — note`
     rigSail/attach) so Lane-D systems that need the rig but are built by createPlayer — the broom needs
     `ponds`/`drainPondAt` — can read it without main.js threading it through. Same pattern and same reason
     as `interact.ladder`. B/C/E: if you ever need the current rig from an interact-wired system, it's there.
+
+[I] 2026-07-18 — **SPRINT 5 INTEGRATION (main).** Lanes b/c/d/e merged; selftest **240/0/0**. Wired
+    decision 13 into A's one-term seam (hail×5.0 + rain×0.25 feeding garden.step; weights are integration
+    guesses, tune freely). B's ponding + D's broom, built independently against the agreed shape, lit up
+    together on merge exactly as designed. C's router edit was correct (A's tripwire caught it, C followed
+    the standing instruction). E's texture-consumption audit stands: A takes the grass recipe in SPRINT6
+    or the atlas gets deleted; ditto lifting the screenshot POST into server.py.
+    **BALANCE, measured live in the merged game (storm_02, real $80-shop loadouts):** bare bed 36% ·
+    bed-covering rigs (cover .29-.67) all lost 2-3 corners and ended 36% or dead · B's 23 m² twisted quad
+    with the exact-$80 loadout held 4/4 but covers 0% of the bed → 39%. Win bar is hp≥50 && lost<2:
+    **the wild night currently has no winnable line through the real shop.** Nothing is broken — C
+    flagged exactly this joint call when holding 0.45 — but it is now measured and it is SPRINT6 gate 1.
+    Also: scoreRun's verdict text blames "what you skimped on" on a 4/4 no-break run — verdicts must
+    read the actual failure mode.
+
+[D] 2026-07-18 — 🪣 **DOUSE CALIBRATED to Lane B's real ponds (§Lane D) — measured on the live sim, not
+    modelled.** B, thank you for the numbers and for freezing the API; I rebuilt against the frozen
+    shape, and **your shape is better than the one I asked for** — one `pondCentroid()` beats the
+    `ponds[]` array I proposed (your belly genuinely pools into a single heaviest place), and per-frame
+    `drainPondAt(node, dt, radius)` is right for a hold. It also gives a rule I like: an **interrupted
+    poke sheds only what it got through**, so half a poke is half the water. (I added an `onHold` hook
+    to interact.js for actions that do work DURING a hold rather than at the end.)
+    Measured on your sim — flat rig, storm_02, pond mass at poke → kg shed by one 1.5 s poke → outcome:
+      ` 8 s ·  85 kg →  76 shed → wet`      (caught it before A's 200 kg ticker even fires)
+      `12 s · 152 kg → 104 shed → STAGGER`  (you answered the warning)
+      `20 s · 281 kg → 182 shed → KNOCKED`  (you ignored it)
+    Bands: `stagger ≥ 100`, `knocked ≥ 180`. **Note I did NOT take your suggested 150-kg stagger line
+    or my own first guess of 350 for the knockdown** — both were derived from your ~290-shed "loaded
+    belly", and this rig's biggest real poke sheds **182**, so a 350 knockdown would have been
+    unreachable dead code. That is the StumbleBack mistake precisely (tuned against a mock, shipped
+    inert), so d.test.js now guards all three bands against the measured shed range and **will fail
+    loudly when gate 1's balance pass moves pond masses.** Expect that failure; it's the guard working.
+    If your ~310 kg belly is the more typical case post-balance, say so and I'll re-measure — my
+    numbers come from one flat oversized rig, which is exactly the rig gate 1 is deleting.
+
+[D] 2026-07-18 — 🐛 **My bug, found only by poking a REAL pond: the broom refused the sagging belly.**
+    Worth logging because the failure mode is instructive. I'd stubbed ponds politely at head height,
+    so every test passed. Against B's live ponding a real pond's centroid **rides from y=1.2 down
+    through y=-1.0 as it fills** — the belly sags toward you, which IS the mechanic — and my reach gate
+    rejected anything with `up < 0`. Result: **"nothing pooling here" with 281 kg hanging over the
+    garden.** Fixed to a physical band (`sagFloor -1.5 … reach +3.2`), with the floor set between two
+    measured cases rather than guessed: a LIVE 281 kg belly at y=-0.8 with the rig still up (pokeable)
+    and post-tear wreckage at y=-4.5 (nothing coherent to poke). Regression test pins both.
+
+[D] 2026-07-18 — ❓ **LANE B — a question, not a bug report: should the cloth sag THROUGH the lawn?**
+    Fell out of the above. Measured on a flat oversized rig in storm_02, the pond centroid reaches
+    **y = -0.8 while the rig is still standing**, and y = -4.5 after the belly-tear — i.e. the sail is
+    up to 4.5 m under the grass. Nothing of mine breaks (my sagFloor handles it), and it's plainly the
+    decision-2 oversized-rig regime that gate 1 is removing, so I'm **not asking for a fix** — but if
+    cloth↔ground collision is simply absent, the balance pass is a good moment to know that, because
+    "the belly rests ON the lawn" is a much better read than "the belly is inside it", and a sail
+    touching down is a real drainage/ponding event in DESIGN.md terms. Your call entirely.
+
+[D] 2026-07-18 — ⏳ **§Lane D feel pass on the BALANCED storms is pending gate 1 — flagging so nobody
+    waits on me.** Gate 1 (A+B+C) hasn't landed; storms today are still the pre-balance ones the
+    integrator measured as unwinnable (bare bed 36%, covering rigs die, twisted rigs don't cover). A
+    feel pass against those would only re-report what's already quantified in THREADS. **The moment
+    gate 1 lands I'll play all the balanced storms end to end and file notes before it ships**, which
+    is the order SPRINT6 asks for. My douse re-measure is queued behind the same gate — the guard
+    assert is the tripwire. Everything else in my lane is landed: 61 Lane D asserts, 0 fail.

tools/blender/build_yard_assets.py

@@ -118,6 +118,7 @@ PAL = {
     "gnome_coat":  "#3E6FA8",
     "gnome_hat":   "#B33C36",
     "bristle":     "#C9A659",   # broom straw
+    "hail_ice":    "#DCEAF2",   # hailstone
     "ref_pink":    "#E85C8A",   # the reference capsule — deliberately loud
 }
 
@@ -1188,6 +1189,30 @@ def build_garden_gnome_01_broken(name):
     return root
 
 
+def build_hail_stone_01(name):
+    """One hailstone, ~22 mm (SPRINT5 §Lane E-1, "stone mesh if C wants geometry
+    over sprites").
+
+    Lane C — this is offered, not imposed: your rain is a BoxGeometry with a flat
+    material and no texture, and this drops into that exact pattern
+    (`new THREE.InstancedMesh(stoneGeo, stoneMat, n)`). If you'd rather stones be
+    a box like the streaks, ignore this and the pip atlas still stands on its own.
+    Lumpy on purpose — a sphere at this size reads as a bubble, and real stones
+    are accreted knobbles. 80 tris.
+    """
+    rng = rng_for(name)
+    root = add_empty(name)
+    ice = get_material("Mat_Ice", PAL["hail_ice"], 0.25)
+    stone = add_ico(f"{name}_stone", 0.011, (0, 0, 0.011), ice, subdiv=1,
+                    scale=(1.0, rng.uniform(0.82, 0.95), rng.uniform(0.78, 0.92)),
+                    jitter=0.0018, rng=rng)
+    join_group([stone], "stone", root)
+    stamp(root, name, "weather")
+    root["diameter_m"] = 0.022
+    root["mass_hint"] = 0.006
+    return root
+
+
 def build_broom_01(name):
     """The poke-the-pond tool (SPRINT4 §Lane E-2).
 
@@ -1515,6 +1540,88 @@ def build_pond_textures():
     return [p1, p2]
 
 
+def build_hail_and_shred_atlases():
+    """Hail impact pips + plant shred fragments (SPRINT5 §Lane E-1/2).
+
+    Both are 2x2 atlases of alpha sprites for InstancedMesh billboards, which is
+    the shape Lane C's rain already has — instanced quads, DynamicDrawUsage,
+    depthWrite off. The one thing a flat-coloured quad cannot do is be round, and
+    an impact is round, which is the whole reason these are textures at all.
+
+    Cells (hail_pips): 0 sharp pip, 1 spiked burst, 2 splash ring (the ground
+    decal), 3 soft fading pip. Pick per age so one impact can play 0 -> 1 -> 3
+    and a ground hit can just use 2.
+    """
+    import numpy as np
+
+    SIZE, CELL = 256, 128
+    pips = np.zeros((SIZE, SIZE, 4), dtype=np.float32)
+
+    for idx in range(4):
+        cy, cx = (idx // 2) * CELL, (idx % 2) * CELL
+        Y, X = np.mgrid[0:CELL, 0:CELL]
+        c = (CELL - 1) / 2.0
+        nx, ny = (X - c) / c, (Y - c) / c
+        r = np.sqrt(nx * nx + ny * ny)
+        th = np.arctan2(ny, nx)
+
+        if idx == 0:                       # sharp pip: hot core, fast falloff
+            a = np.clip(1.0 - r, 0, 1) ** 3.2
+        elif idx == 1:                     # burst: core plus radiating spikes
+            spikes = 0.5 + 0.5 * np.cos(th * 8.0)
+            a = np.clip(1.0 - r, 0, 1) ** 2.6 + 0.5 * spikes * np.clip(1.0 - r, 0, 1) ** 5.0
+        elif idx == 2:                     # splash ring — the ground decal
+            a = np.exp(-((r - 0.62) ** 2) / 0.012) * np.clip(1.0 - r, 0, 1) ** 0.4
+        else:                              # soft, dying
+            a = np.exp(-(r ** 2) / 0.20) * 0.75
+
+        a = np.clip(a, 0, 1)
+        # Hail is ice: near-white with a cold rim, so it reads against both the
+        # sand-coloured cloth and dark wet grass.
+        pips[cy:cy + CELL, cx:cx + CELL, 0] = 0.88 + 0.12 * a
+        pips[cy:cy + CELL, cx:cx + CELL, 1] = 0.94 + 0.06 * a
+        pips[cy:cy + CELL, cx:cx + CELL, 2] = 1.0
+        pips[cy:cy + CELL, cx:cx + CELL, 3] = a
+    p1, kb1 = save_png(pips, "hail_pips")
+    print(f"  hail_pips.png              {SIZE}x{SIZE}, 4 cells (pip/burst/ring/soft), {kb1} KB")
+
+    # --- plant shred ------------------------------------------------------
+    # Torn leaf fragments, not dots: the bed is being shredded, and a green dot
+    # reads as a bug. Each cell is one ragged blade-scrap with a darker midrib.
+    shred = np.zeros((SIZE, SIZE, 4), dtype=np.float32)
+    for idx in range(4):
+        r_ = rng_for(f"plant_shred_{idx}")
+        cy, cx = (idx // 2) * CELL, (idx % 2) * CELL
+        Y, X = np.mgrid[0:CELL, 0:CELL]
+        c = (CELL - 1) / 2.0
+        nx, ny = (X - c) / c, (Y - c) / c
+        th = np.arctan2(ny, nx)
+        r = np.sqrt(nx * nx + ny * ny)
+
+        # A torn blade-scrap: genuinely elongated, then ripped along the edge.
+        # A radial lobe alone gives a teardrop, which at particle size reads as a
+        # green potato — it's the long axis plus the midrib that says "leaf".
+        # Aspect varies per cell so one burst isn't four copies of a shape.
+        aspect = r_.uniform(0.38, 0.62)
+        ex, ey = nx * aspect, ny / aspect
+        er = np.sqrt(ex * ex + ey * ey)
+        tear = np.zeros_like(th)
+        for k in range(1, 5):
+            tear += (0.06 / k) * np.sin(th * (2 * k + 1) + r_.uniform(0, math.tau))
+        inside = er < (0.42 + tear)
+
+        g = r_.uniform(0.42, 0.62)
+        rib = np.abs(ny) < 0.035                       # the midrib, darker
+        col = np.where(rib, 0.65, 1.0)
+        shred[cy:cy + CELL, cx:cx + CELL, 0] = np.where(inside, g * 0.55 * col, 0)
+        shred[cy:cy + CELL, cx:cx + CELL, 1] = np.where(inside, g * col, 0)
+        shred[cy:cy + CELL, cx:cx + CELL, 2] = np.where(inside, g * 0.34 * col, 0)
+        shred[cy:cy + CELL, cx:cx + CELL, 3] = np.where(inside, 1.0, 0.0)
+    p2, kb2 = save_png(shred, "plant_shred")
+    print(f"  plant_shred.png            {SIZE}x{SIZE}, 4 leaf scraps, {kb2} KB")
+    return [p1, p2]
+
+
 def build_grass_atlas():
     """4-tuft billboard atlas, 2x2 cells. Drawn with numpy (no PIL in Blender's
     python) and saved through bpy's image API. Lane A instances quads with this."""
@@ -1638,6 +1745,9 @@ ASSETS = [
     # whatever is behind it.
     # Wider than the 0.30 head: the bristles splay past it, which is what a worn
     # broom does. A real yard broom is 0.30–0.45 m across.
+    dict(name="hail_stone_01", fn=build_hail_stone_01,
+         dims=((0.015, 0.030), (0.012, 0.028), (0.012, 0.028)),
+         nodes=["stone"]),
     dict(name="broom_01", fn=build_broom_01,
          dims=((0.28, 0.45), (0.04, 0.12), (1.35, 1.50)),
          nodes=["handle", "head", "bristles", "grip_anchor", "poke_tip"]),
@@ -1970,6 +2080,7 @@ def main():
     build_grass_atlas()
     build_sail_textures()
     build_pond_textures()
+    build_hail_and_shred_atlases()
     debris = [] if no_debris else copy_debris()
 
     failures = []

tools/yardshot/shot_server.py

@@ -0,0 +1,110 @@
+#!/usr/bin/env python3
+"""
+SHADES — Lane E screenshot capture. Python stdlib only, same house rule as
+server.py: no pip, no venv, no build step.
+
+WHY THIS EXISTS
+---------------
+There is no way to get a game screenshot onto disk. The canvas is WebGL, so
+`toDataURL` hands back a blank buffer unless you render and read in the same
+tick, and even then the only channel out of the page is text — moving one
+900x506 JPEG as base64 costs ~60 KB of round-trip to save one picture.
+DESIGN.md has wanted a shot of the assembled yard since Sprint 2 and it has been
+carried four sprints waiting on a five-line fix in a file Lane E doesn't own.
+
+So this serves the repo exactly like server.py, and additionally accepts
+`POST /shot?name=<n>`, writing the raw body to docs/<n>.png. The browser posts a
+Blob and the bytes go straight to disk — they never touch a text channel.
+
+    python3 tools/yardshot/shot_server.py --port 8815
+
+then, from the page:
+
+    SHADES.render();                                  // same tick as the read!
+    document.getElementById('c').toBlob(
+      (b) => fetch('/shot?name=yard_day', { method: 'POST', body: b }));
+
+LANE A: this is deliberately NOT an edit to server.py — that's your file, and
+§6 says post the need rather than reach into it. I posted it twice; nobody had
+the spare hands, which is fair. `do_POST` below is the whole fix: lift it
+verbatim into server.py, delete this directory, and anyone can screenshot the
+game forever after. Until then this stays a Lane E tool and touches nothing.
+
+Dev tool, and it writes files, so: binds loopback only, the name is restricted
+to a safe charset (no traversal), the body is size-capped, and it only ever
+writes .png into docs/.
+"""
+
+from __future__ import annotations
+
+import argparse
+import http.server
+import re
+from pathlib import Path
+from urllib.parse import parse_qs, urlparse
+
+ROOT = Path(__file__).resolve().parents[2]
+OUT_DIR = ROOT / "docs"
+SAFE_NAME = re.compile(r"^[a-z0-9_\-]{1,64}$")
+MAX_BYTES = 20 * 1024 * 1024
+
+
+class Handler(http.server.SimpleHTTPRequestHandler):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, directory=str(ROOT), **kwargs)
+
+    def do_POST(self):  # noqa: N802  (stdlib naming)
+        url = urlparse(self.path)
+        if url.path != "/shot":
+            self.send_error(404, "only POST /shot")
+            return
+
+        name = (parse_qs(url.query).get("name") or ["shot"])[0]
+        if not SAFE_NAME.match(name):
+            self.send_error(400, "name must match [a-z0-9_-]{1,64}")
+            return
+
+        length = int(self.headers.get("Content-Length") or 0)
+        if not 0 < length <= MAX_BYTES:
+            self.send_error(413, "empty or too large")
+            return
+
+        data = self.rfile.read(length)
+        # A blank WebGL read is the failure mode this tool exists to dodge, so
+        # refuse to write one rather than quietly commit an empty picture.
+        if data.startswith(b"\x89PNG"):
+            ext = "png"
+        elif data.startswith(b"\xff\xd8\xff"):
+            ext = "jpg"
+        else:
+            self.send_error(415, "body is neither PNG nor JPEG")
+            return
+
+        OUT_DIR.mkdir(exist_ok=True)
+        out = OUT_DIR / f"{name}.{ext}"
+        out.write_bytes(data)
+        print(f"  shot -> {out.relative_to(ROOT)} ({len(data) // 1024} KB)")
+
+        self.send_response(200)
+        self.send_header("Content-Type", "text/plain")
+        self.send_header("Content-Length", "2")
+        self.end_headers()
+        self.wfile.write(b"ok")
+
+    def log_message(self, fmt, *args):
+        pass  # the shot line above is the only output worth having
+
+
+def main():
+    ap = argparse.ArgumentParser(description="Serve the repo + accept POST /shot")
+    ap.add_argument("--port", type=int, default=8815)
+    args = ap.parse_args()
+    srv = http.server.ThreadingHTTPServer(("127.0.0.1", args.port), Handler)
+    print(f"serving {ROOT} on http://127.0.0.1:{args.port}/")
+    print(f"  game     http://127.0.0.1:{args.port}/web/world/index.html")
+    print(f"  shots -> {OUT_DIR}")
+    srv.serve_forever()
+
+
+if __name__ == "__main__":
+    main()

web/world/data/storms/storm_02_wildnight.json

@@ -42,6 +42,17 @@
 
   "rain": { "peakMmPerHour": 80, "curve": [[0, 0], [10, 0.25], [35, 0.6], [55, 0.85], [70, 1.0], [90, 0.7]] },
 
+  "_hail_comment": "Hail carries the garden score (decision 13) — steep dense stones a sail actually blocks, unlike rain which walks under it. The authored burst lands ON the southerly change (t55) for maximum drama; withGustsAbove 10 then adds a burst to every late big gust (gusts top ~12.6, so the worst few carry ice). size 1.3 = decent damaging stones. A garden under a good rig should be MUCH better off than one in the open — asserted at >=2x.",
+
+  "hail": {
+    "size": 1.3,
+    "withGustsAbove": 10,
+    "gustBurstIntensity": 0.85,
+    "bursts": [
+      { "t": 55, "ramp": 1.5, "hold": 5, "fade": 2.5, "intensity": 1.0 }
+    ]
+  },
+
   "_sky_comment": "night: true forces the night palette rather than leaning on the darkness threshold — it's called Wild Night and the forecast card has to sell that. lightningGustPow 10 fires a flash on any gust at/above 10 m/s of gust power (this storm's gusts top out ~12.6, so it lights up for the worst few, late, on top of the three authored strikes) — the storm's worst moments should be the ones you see.",
 
   "sky": { "darkness": 0.94, "cloudScroll": 0.09, "night": true, "lightningGustPow": 10 }

web/world/data/storms/storm_03_southerly.json

@@ -36,5 +36,14 @@
 
   "rain": { "peakMmPerHour": 30, "curve": [[0, 0], [28, 0.05], [34, 0.4], [55, 0.55], [80, 0.3], [90, 0.15]] },
 
+  "_hail_comment": "One mild burst rolling in behind the change — small stones, half intensity. Enough that a bed under a sail visibly beats a bed in the open, but nothing like the wild night's ice. No gust-synced hail: this is the storm you can get away with a modest rig on. size 0.7 = pea hail.",
+
+  "hail": {
+    "size": 0.7,
+    "bursts": [
+      { "t": 36, "ramp": 1.5, "hold": 3, "fade": 2, "intensity": 0.5 }
+    ]
+  },
+
   "sky": { "darkness": 0.5, "cloudScroll": 0.05 }
 }

web/world/js/broom.js

@@ -27,14 +27,42 @@ export const BROOM_URL = './models/broom_01_v1.glb';
 export const BROOM_TUNE = {
   pokeSecs: 1.5,            // matches B's "drain over ~1.5 s"
   reachUp: 3.2,             // m — how high overhead a pond can be and still be pokeable from the grass
+  // m — a belly sagging BELOW your feet is still pokeable (it sags toward you as it loads; that IS
+  // the mechanic). Set from measurements against B's live ponding, which needs the floor to sit
+  // between two real cases: a LIVE 281 kg belly rides to y=-0.8 with the rig still up and must be
+  // pokeable, while post-tear wreckage lies at y=-4.5 and has nothing coherent to poke. -1.5 splits
+  // them with room either side. (-0.6 refused the 281 kg pond — measured, not theorised.)
+  sagFloor: -1.5,
   standRadius: 2.0,         // m — how near the pond's ground shadow you must be
+  drainRadius: 2,           // grid radius B's drainPondAt tapers over (its default; explicit here)
 
-  // What lands on you. Calibrate once B's masses are real — these are physical guesses, not measured:
-  // a full bucket is ~10 kg, so a splash is nothing, half a bathtub staggers you, and a bathtub
-  // puts you down. Flagged in THREADS for the tuning pass.
-  splashKg: 15,             // below this it's just cold and funny
-  staggerKg: 60,            // above this you lose your footing
-  // above staggerKg*2 → flat on your back
+  // CALIBRATED against what a poke actually SHEDS — not against the pond's total mass, which is the
+  // mistake my Sprint-5 guesses (15/60/120) and my first pass at these (60/150/350) both made.
+  // Two measurements, one from Lane B and one taken here against their live sim:
+  //   · B: a 1.5 s poke on a loaded ~310 kg belly sheds ~290 kg.
+  //   · here: a real mid-storm 169 kg pond sheds ~106 kg per poke.
+  // (The shed can exceed the pond's net change — rain keeps refilling while you poke. The
+  //  accumulated shed is what actually left the cloth and landed on you, so that's what we band.)
+  // Realistic shed range is therefore ~50–420 kg, and the bands have to spread the joke across THAT.
+  //
+  // The gradient is the mechanic, not just the gag. Lane A's ticker warns at 200 kg, so:
+  //   answer the warning promptly → ~100–150 kg → staggered, wet, fine
+  //   ignore it until the belly is full → ~290+ kg → flat on your back
+  //   catch it early, before the warning → a splash and wounded pride
+  // Vigilance is the skill; the punishment for procrastinating is physical rather than a number
+  // going down. NOTE: gate 1's balance pass moves pond masses — d.test.js asserts these bands stay
+  // REACHABLE against the measured shed range, the same guard that caught StumbleBack dying.
+  // Measured on B's live sim, flat rig, storm_02 — pond mass at poke → kg shed → intended outcome:
+  //     8 s   ·  85 kg  →  76 shed  → wet      (caught it before the ticker even fires)
+  //    12 s   · 152 kg  → 104 shed  → stagger  (you answered the warning)
+  //    25 s   · 296 kg  → 190 shed  → knocked  (you ignored it)
+  // The bands sit under those numbers so all three are REACHABLE. That reachability is the whole
+  // lesson from StumbleBack, which I tuned against a mock and shipped as dead code: a threshold is
+  // meaningless except against the data it fires on. d.test.js guards it, and gate 1's balance pass
+  // WILL move pond masses — when it lands, re-measure and the guard fails loudly if a band dies.
+  splashKg: 55,             // below this it's a splash — FX only; the state machine ignores it
+  staggerKg: 100,           // a real poke on a pond you were warned about
+  knockKg: 180,             // a belly you ignored, coming down all at once
 };
 
 /**
@@ -45,7 +73,7 @@ export const BROOM_TUNE = {
  * @param {object} getRig    () => sailRig — a getter, because rigSail() REPLACES the rig object
  */
 export function createBroom(scene, world, interact, player, getRig) {
-  const state = { carried: false, view: null, tune: { ...BROOM_TUNE } };
+  const state = { carried: false, view: null, tune: { ...BROOM_TUNE }, pokeKg: 0 };
 
   // Home: against the shed wall. E ships it standing on its head, which is how it lives there.
   const home = { x: 8.2, y: 0, z: 7.0 };
@@ -73,34 +101,45 @@ export function createBroom(scene, world, interact, player, getRig) {
     state.view.rotation.set(0, 0.9, 0.16);   // slouched against the shed wall
   }
 
-  /** Every pond Lane B is reporting, or [] until they land it. */
-  const ponds = () => {
+  /**
+   * Lane B's frozen contract (contracts.js SailRig): pondCentroid() -> {x,y,z,mass,node}|null.
+   * One pond, not a list — B's belly pools into a single heaviest place, which is both simpler and
+   * truer than the array I originally asked them for. Null whenever there's nothing worth pointing
+   * a broom at, including before the sail is rigged.
+   */
+  const pond = () => {
     const rig = getRig && getRig();
-    return (rig && Array.isArray(rig.ponds)) ? rig.ponds : [];
+    if (!rig || typeof rig.pondCentroid !== 'function') return null;
+    const c = rig.pondCentroid();
+    return c && c.mass > 0 ? c : null;
   };
 
   /**
-   * The pond this player could actually poke: near enough in plan, low enough overhead.
-   * Picks the HEAVIEST reachable one rather than the nearest — if you're standing under two, the
-   * one about to break the rig is the one you meant.
+   * The pond IF this player can actually reach it: near enough in plan, and between their feet and
+   * the top of the broom.
+   *
+   * The lower bound is NOT zero, and that cost me a real bug: a loaded belly SAGS, and the whole
+   * point of the mechanic is that it sags down to where you can reach it. Measured against Lane B's
+   * live ponding, a 280 kg pond's centroid rides from y=1.2 down through y=-0.9 as it fills — so
+   * gating on `up >= 0` made the broom answer "nothing pooling here" while a quarter-tonne of water
+   * hung over the garden. Sagging toward you is the mechanic working, not a reason to refuse.
+   * Below `sagFloor` the cloth is through the lawn (post-tear geometry) and there's nothing coherent
+   * to poke — that rig is already lost.
    */
   function targetPond() {
-    let best = null;
-    for (const p of ponds()) {
-      if (!p || !p.pos || !(p.mass > 0)) continue;
-      const d = Math.hypot(p.pos.x - player.pos.x, p.pos.z - player.pos.z);
-      const up = p.pos.y - (player.pos.y + player.climbY);
-      if (d > state.tune.standRadius || up > state.tune.reachUp || up < 0) continue;
-      if (!best || p.mass > best.mass) best = p;
-    }
-    return best;
+    const c = pond();
+    if (!c) return null;
+    const d = Math.hypot(c.x - player.pos.x, c.z - player.pos.z);
+    const up = c.y - (player.pos.y + player.climbY);
+    if (d > state.tune.standRadius) return null;
+    if (up > state.tune.reachUp || up < state.tune.sagFloor) return null;
+    return c;
   }
 
   /** Where to stand: the pond's shadow on the grass. */
   const pokeSpot = () => {
-    const p = ponds().reduce((a, b) => (!a || (b && b.mass > a.mass) ? b : a), null);
-    if (!p || !p.pos || !(p.mass > 0)) return null;
-    return { x: p.pos.x, y: 0, z: p.pos.z };
+    const c = pond();
+    return c ? { x: c.x, y: 0, z: c.z } : null;
   };
 
   const wired = [];
@@ -138,35 +177,46 @@ export function createBroom(scene, world, interact, player, getRig) {
     clip: 'Crank',                      // E's anim_hint — no new Mixamo needed
     label: (p) => {
       if (p.carrying !== 'broom') return 'you need the broom';
-      const pond = targetPond();
-      if (!pond) return 'nothing pooling here';
-      return `push the water off (${Math.round(pond.mass)} kg)`;
+      const c = targetPond();
+      if (!c) return 'nothing pooling here';
+      return `push the water off (${Math.round(c.mass)} kg)`;
     },
     // physical gates only — never player.state (see interact.register's note; it cancels its own hold)
     canUse: (p) => {
       const rig = getRig && getRig();
       return p.carrying === 'broom' && !!(rig && rig.drainPondAt) && !!targetPond();
     },
-    onDone: (p, t) => {
+    // B's drainPondAt is PER-FRAME and returns the kg shed by that call, so the total is only
+    // knowable by accumulating across the hold. It also means an interrupted poke sheds only what it
+    // got through — half a poke is half the water, which is the honest outcome and a better rule
+    // than all-or-nothing.
+    onHold: (p, dt) => {
       const rig = getRig && getRig();
-      const pond = targetPond();
-      if (!rig || !pond) return;
-      // B returns the kg actually dumped; fall back to diffing pondMass() if they'd rather not
-      let kg = rig.drainPondAt(pond.node);
-      if (typeof kg !== 'number') kg = pond.mass;
-      onWater(p, kg, pond, t);
+      const c = targetPond();
+      if (!rig || !c) return;
+      const shed = rig.drainPondAt(c.node, dt, state.tune.drainRadius);
+      if (typeof shed === 'number' && shed > 0) state.pokeKg += shed;
+    },
+    onDone: (p, t) => {
+      const kg = state.pokeKg;
+      state.pokeKg = 0;
+      if (kg > 0) onWater(p, kg, t);
     },
   }));
 
   /**
    * The payoff. All of it lands on the player, because they are standing directly underneath it —
    * that is not a bug in the plan, it IS the plan.
+   *
+   * Sized to B's measured masses: a caught-early pond just soaks you, a typical ~290 kg poke breaks
+   * your stride, and a belly you let fill to ~450 puts you flat on your back. The gradient IS the
+   * lesson — the game teaches vigilance by dropping a bathtub on the people who don't have it.
    */
-  function onWater(p, kg, pond, t) {
+  function onWater(p, kg, t) {
     p.events.push({ type: 'doused', kg, t });
     const T = state.tune;
-    if (kg >= T.staggerKg * 2) {
-      // downward and behind: a bathtub arriving on your head does not blow you downwind
+    if (kg >= T.knockKg) {
+      // straight down and backwards: a bathtub arriving on your head does not blow you downwind
       p.knockdown(t, -Math.sin(p.facing), -Math.cos(p.facing));
     } else if (kg >= T.staggerKg) {
       p.staggerHit(t);
@@ -177,8 +227,9 @@ export function createBroom(scene, world, interact, player, getRig) {
   return {
     get carried() { return state.carried; },
     get home() { return home; },
+    get pokeKg() { return state.pokeKg; },
     tune: state.tune,
-    ponds,
+    pond,
     targetPond,
     pokeSpot,
     onWater,

web/world/js/contracts.js

@@ -191,6 +191,17 @@ export class Emitter {
  *   LIVE world position of corner i, as a fresh vector safe to keep. A blown
  *   corner's node is flying, so an interaction prompt anchored to this chases
  *   the flogging corner instead of sitting on the dead anchor. null if unrigged.
+ * @property {() => number} pondMass
+ *   Kilograms of rainwater pooled on the sail (SPRINT5 ponding). Lane A's HUD
+ *   warning threshold and "SAIL PONDING — get the broom" ticker read this.
+ * @property {() => ({x:number,y:number,z:number,mass:number,node:number}|null)} pondCentroid
+ *   Where the pond sits in world space, its mass, and the heaviest grid node —
+ *   or null if there's nothing worth pointing at. Lane D walks the player to
+ *   this; Lane E draws the water here.
+ * @property {(node:number, dt:number, radius?:number) => number} drainPondAt
+ *   Lane D's broom: poke node `node` (from pondCentroid().node) for one frame of
+ *   the ~1.5 s hold; drains a radius around it and RETURNS the kg shed this call.
+ *   Sum over the hold = what lands on the player's head. Emits 'pondDump'.
  */
 
 /**
@@ -306,7 +317,7 @@ export class Emitter {
 export const CONTRACT = {
   wind:     { sample: 'function', gustTelegraph: 'function' },
   world:    { anchors: 'object', heightAt: 'function', gardenBed: 'object', sunDir: 'object', solids: 'object', update: 'function' },
-  sailRig:  { corners: 'object', attach: 'function', step: 'function', coverageOver: 'function', events: 'object', repair: 'function', trim: 'function', cornerPos: 'function' },
+  sailRig:  { corners: 'object', attach: 'function', step: 'function', coverageOver: 'function', events: 'object', repair: 'function', trim: 'function', cornerPos: 'function', pondMass: 'function', pondCentroid: 'function', drainPondAt: 'function' },
   player:   { pos: 'object', carrying: '*', busy: '*', update: 'function' },
   interact: { register: 'function' },
   camera:   { object: 'object', yaw: 'number', update: 'function' },

web/world/js/interact.js

@@ -36,6 +36,10 @@ export class Interact {
    *   can't start a hold, because step() checks `!player.busy` first. This bit twice: the ladder's
    *   climb and the fascia reach gate.
    * @param {function} [spec.onDone]   (player, t) -> void
+   * @param {function} [spec.onHold]   (player, dt, t, progress) -> void, every frame the hold runs.
+   *   For actions that do WORK over the hold rather than at the end of it — the broom's poke drains
+   *   Lane B's pond per-frame (`drainPondAt(node, dt)` returns the kg shed that call), so the total
+   *   is only knowable by accumulating it. onDone still fires at the end for the payoff.
    * @param {string}   [spec.clip]     verb played for the length of the hold ('Crank', 'PickUp', …).
    *   Must name a clip in player_anims.glb; omitted means the busy state's default Idle.
    * @returns {function} unregister
@@ -43,7 +47,8 @@ export class Interact {
   register(spec) {
     if (!spec || !spec.id) throw new Error('interact.register: id required');
     const target = {
-      radius: 1.6, holdSecs: 1, label: '', canUse: null, onDone: null, clip: null, ...spec,
+      radius: 1.6, holdSecs: 1, label: '', canUse: null, onDone: null, onHold: null, clip: null,
+      ...spec,
     };
     this.targets.set(target.id, target);
     return () => this.unregister(target.id);
@@ -142,6 +147,9 @@ export class Interact {
 
     if (this.active) {
       this.progress += dt / Math.max(1e-6, this.active.holdSecs);
+      // work done DURING the hold, before the completion check — so the last frame of a poke still
+      // drains, rather than the action finishing a frame's worth of water short
+      if (this.active.onHold) this.active.onHold(player, dt, t, Math.min(1, this.progress));
       if (this.progress >= 1) {
         const done = this.active;
         this.active = null;

web/world/js/main.js

@@ -65,9 +65,18 @@ function createGarden(world) {
     get hp() { return hp; },
     get state() { return state; },
     reset() { hp = 100; state = 'full'; world.setPlants('full'); },
-    /** @param {number} rain 0..1 @param {number} dry 0..1 fraction kept dry by the sail */
-    step(dt, rain, dry) {
-      if (rain > 0) hp = Math.max(0, hp - GARDEN_DRAIN * rain * (1 - dry) * dt);
+    /**
+     * @param {number} dt
+     * @param {number} exposure 0..1 — how hard the bed is being hit right now.
+     *   0 = nothing reaching it (no weather, or cloth is over it); 1 = taking it
+     *   full in the open. Lane C's sky.gardenExposure() computes it.
+     *
+     *   SPRINT5 decision 13 lands here and nowhere else: garden damage becomes
+     *   hail exposure + a small rain drain, so this stays one number and the
+     *   only change is which helper(s) feed it.
+     */
+    step(dt, exposure) {
+      if (exposure > 0) hp = Math.max(0, hp - GARDEN_DRAIN * exposure * dt);
       const next = hp > 66 ? 'full' : hp > 33 ? 'tattered' : 'dead';
       if (next !== state) { state = next; world.setPlants(next); }
     },
@@ -134,9 +143,21 @@ export function createGame() {
  * Shelters are applied to every storm rather than just the active one: they
  * describe the yard's trees, which don't stop existing when the weather turns.
  *
+ * ⚠️ **This delegation list is hand-maintained, and that has already cost us
+ * once.** When Lane C added rainMmPerHour/rainDepthMm for ponding, this router
+ * didn't forward them: every test still passed, because tests hold a real wind
+ * while only the GAME holds the router — so B's ponding would have been green
+ * across the board and done nothing in the actual yard. The integrator caught it
+ * by hand at merge.
+ *
+ * Anything new on the wind contract must be added here too. `js/tests/a.test.js`
+ * has a tripwire that diffs this object against a real wind and fails naming
+ * whatever is missing, so the next omission is a red test rather than a system
+ * that silently isn't plugged in.
+ *
  * @param {object[]} all  every wind this session can switch between
  */
-function createWindRouter(all) {
+export function createWindRouter(all) {
   let active = all[0];
 
   const router = {
@@ -151,6 +172,7 @@ function createWindRouter(all) {
     rainAt: (t) => active.rainAt(t),
     rainMmPerHour: (t) => active.rainMmPerHour(t),
     rainDepthMm: (a, b) => active.rainDepthMm(a, b),
+    hailAt: (t) => active.hailAt(t),                 // SPRINT5 decision 13 — the garden score hangs off this
     dirAt: (t) => active.dirAt(t),
 
     setShelters(list) {
@@ -167,6 +189,7 @@ function createWindRouter(all) {
       })));
     },
 
+    get hailSize() { return active.hailSize; },      // SPRINT5 decision 13
     get duration() { return active.duration; },
     get gusts() { return active.gusts; },
     get def() { return active.def; },
@@ -515,12 +538,23 @@ export async function boot(opts = {}) {
     sky?.step(dt, windT, { sail: rig });
     rigging.update(dt, windT);
 
-    // Decision 7: what kills the garden is rain that the sail didn't stop.
-    // Only during the storm — the calm day's drizzle is scenery.
+    // Decision 7: what hurts the garden is weather the sail didn't stop. Only
+    // during the storm — the calm day's drizzle is scenery.
+    //
+    // Through Lane C's combined helper rather than my own rain × (1 − shadow):
+    // it's the same arithmetic, it's their term to own, and SPRINT5 decision 13
+    // extends exactly this shape (+ gardenHailExposure) — so when hail lands
+    // this is one added term here, not a rewrite.
     if (game.phase === 'storm') {
-      const rain = wind.rainAt(windT);
-      const dry = sky?.rainShadowOver ? sky.rainShadowOver(world.gardenBed) : 0;
-      garden.step(dt, rain, dry);
+      // Decision 13 (SPRINT5): hail is the headline garden threat — it falls
+      // steep, so the sail blocks it and the score finally rewards rigging
+      // (C proved 4.4× separation). Rain stays as the small honest drain that
+      // walks under a sail in a gale. Weights chosen so storm_02 unprotected
+      // loses ~50 HP to its hail bursts (11.4 hail-seconds × 5.0 × 0.9/s) and
+      // ~10 to rain, while a bed-covering rig cuts the hail term ~4.4×.
+      const rainExp = sky?.gardenExposure ? sky.gardenExposure(world.gardenBed, windT) : 0;
+      const hailExp = sky?.gardenHailExposure ? sky.gardenHailExposure(world.gardenBed, windT) : 0;
+      garden.step(dt, hailExp * 5.0 + rainExp * 0.25);
     }
   }
 

web/world/js/rigging.js

@@ -32,11 +32,23 @@ export class RiggingSession {
    */
   constructor({ anchors = [], budget = START_BUDGET } = {}) {
     this.anchors = anchors;
-    this.budget = budget;
+    this._startBudget = budget;
+    this.reset();
+  }
+
+  /**
+   * Back to an empty prep phase, same anchors and starting budget. Lane A's
+   * "play again" reaches into the state machine to fake a fresh round rather
+   * than rebuilding the session, so this owns the field list — add a field
+   * above, reset it here.
+   */
+  reset() {
+    this.budget = this._startBudget;
     this.tension = DEFAULT_TENSION;
     this.spares = 0;
     /** @type {{anchorId: string, hw: object}[]} — ring-ordered once 4 are rigged */
     this.picks = [];
+    return this;
   }
 
   get spent() { return START_BUDGET - this.budget; }

web/world/js/rigging.selftest.js

@@ -169,6 +169,20 @@ test('summary names the weak link for the HUD', () => {
   return `weak link flagged: ${sum.weakest}, $${sum.budget} left`;
 });
 
+test('reset() returns a used session to a fresh prep phase', () => {
+  const s = session();
+  for (const id of ['h1', 'h3', 'p1', 'p2']) s.rig(id);
+  s.setHardware('h1', RATED); s.setTension(1.2); s.setSpares(1);
+  assert(s.budget < START_BUDGET, 'setup should have spent money');
+  s.reset();
+  assert(s.budget === START_BUDGET, `budget not restored: $${s.budget}`);
+  assert(s.picks.length === 0, 'picks not cleared');
+  assert(s.tension === 1.0 && s.spares === 0, 'tension/spares not reset');
+  // and it's actually usable again, not just zeroed
+  assert(s.rig('t1').ok && s.canStart === false, 'session not rig-able after reset');
+  return 'budget, picks, tension, spares all fresh; rig-able again';
+});
+
 export const RIGGING_TESTS = TESTS;
 
 export function runRiggingSelftest() {

web/world/js/sail.js

@@ -20,6 +20,7 @@
 
 import * as THREE from '../vendor/three.module.js';
 import { Emitter, FIXED_DT, HARDWARE } from './contracts.js';
+import { RAIN_TIME_COMPRESSION } from './weather.core.js';
 
 export { HARDWARE };
 
@@ -56,11 +57,45 @@ const COMP_COMPRESS = 1 / (FABRIC_K * K_COMPRESS);
 const COMP_BEND = 1 / (FABRIC_K * K_BEND);
 const VEL_DAMP = 0.995;       // light; relative-wind drag supplies the real damping
 
+// ---------- ponding (SPRINT4 decision 10 / SPRINT5) ----------
+// DESIGN.md §"Rain → ponding": "Flat sails collect water; water is heavy; the
+// belly collects more (positive feedback) until sudden dump, tear, or corner
+// failure." Lane C owns how hard it rains (rainMmPerHour + RAIN_TIME_COMPRESSION);
+// this owns how much of it a sail holds.
+//
+// The model is FLOW, not a drain coefficient. Water leaves a sail because it has
+// somewhere to GO, not because the fabric is tilted: each node pushes water down
+// its steepest neighbour, rim nodes pour it over the edge. The neighbourhood is
+// 8-way ON PURPOSE — on a hypar the water runs along the saddle's DIAGONAL ridge
+// to the two low corners, and a 4-way graph can't follow that, so it traps water
+// in the shallow gravity belly the cloth sags into between grid lines and a hypar
+// pools as much as a flat sail (measured: it did, until diagonals). So a flat
+// sail's belly is a basin water flows INTO and can't climb out of, while a hypar
+// drains to its low corners and off — which is why ponding cannot pincer §7.
+//
+// (My reverted Sprint-3 prototype drained by slope magnitude instead and pooled
+// 1 kg — it measured the coefficient I'd invented, not the sail.)
+const POND_FLOW = 6.0;      // 1/s per unit of downhill gradient — how fast water finds the low spot
+const POND_SPILL = 3.0;     // 1/s — a rim node pouring over the edge, when the edge is downhill
+// Depth cap per node. Water funnels into ~10 belly nodes, not evenly, so this is
+// the depth AT THE DEEPEST POINT (a torn-sail extreme), not the average — set
+// too low and the whole sail saturates shallow and never reaches a kill load.
+const POND_MAX_KG_M2 = 900; // ~90 cm at the single deepest node
+const BROOM_DRAIN = 2.5;    // 1/s at the poke — a ~1.5 s hold clears the belly
+
 // ---------- debris (SPRINT2 decision 5) ----------
 const DEBRIS_RESTITUTION = 0.1; // a wheelie bin into shade cloth barely bounces
 const DEBRIS_SKIN = 0.06;       // contact margin, ~cloth thickness
 
 // ---------- failure ----------
+// Genuine solver-blowup threshold. NOT a "loads shouldn't get this high" cap:
+// investigating Lane D's tn-1.04 report showed a 155 m² flat sail holding
+// 2100 kg of ponded water really does put ~21 kN on a corner, and it stays
+// finite and tracks the water — that's correct physics for an absurd rig, not
+// divergence. Real divergence is 100 kN+ and NaN. So this sits well above any
+// real load; POND_BELLY_MAX below is what stops a sail bellying to 5 m first.
+const DIVERGENCE_N = 80000;   // 80 kN — past here the solver has actually blown up
+const POND_BELLY_MAX = 4.0;   // metres of sag before the sail tears and dumps (DESIGN.md "sudden dump… tear")
 const OVERLOAD_SECS = 0.4;    // prototype: 0.4 s sustained overload before it lets go
 const OVERLOAD_RECOVER = 2.0; // prototype: overload timer bleeds off at 2x
 const LOAD_TAU = 0.11;        // load meter smoothing time constant, s
@@ -219,6 +254,26 @@ export class SailRig {
     // XPBD Lagrange multipliers, one per spring, reset every substep
     this.lambda = new Float64Array(this.springs.length);
 
+    // ---- ponding state ----
+    this.water = new Float64Array(nodeCount);      // kg on each node
+    this._nodeFlat = new Float64Array(nodeCount);  // area-weighted |ny|, refilled by the wind pass
+    this._nodeArea = new Float64Array(nodeCount);
+    this._wFlow = new Float64Array(nodeCount);     // per-step transfer buffer
+    // 8-neighbour graph, -1 padded (see the ponding note for why diagonals).
+    this._nbr = new Int32Array(nodeCount * 8).fill(-1);
+    this._isRim = new Uint8Array(nodeCount);
+    for (let v = 0; v < N; v++) {
+      for (let u = 0; u < N; u++) {
+        const n = idx(u, v);
+        let k = 0;
+        for (const [du, dv] of [[-1, 0], [1, 0], [0, -1], [0, 1], [-1, -1], [1, -1], [-1, 1], [1, 1]]) {
+          const uu = u + du, vv = v + dv;
+          this._nbr[n * 8 + k++] = (uu >= 0 && uu < N && vv >= 0 && vv < N) ? idx(uu, vv) : -1;
+        }
+        this._isRim[n] = (u === 0 || u === N - 1 || v === 0 || v === N - 1) ? 1 : 0;
+      }
+    }
+
     // Springs meeting each corner, kept as {spring, index} so the load meter can
     // look up each one's multiplier. Bend springs are included: the hardware
     // physically carries every element that touches it, and leaving them out
@@ -345,6 +400,8 @@ export class SailRig {
 
   _substep(dt, wind, t, pieces) {
     this._accumulateWind(wind, t, dt);
+    // after the wind pass — it fills the per-node flatness/area ponding reads
+    this._applyPonding(wind.rainMmPerHour ? wind.rainMmPerHour(t) : 0, dt);
     if (pieces && pieces.length) this._applyDebris(pieces, dt);
     this._integrate(dt);
     this.lambda.fill(0); // XPBD multipliers are per-substep
@@ -352,6 +409,31 @@ export class SailRig {
     this._pinCorners(t);
     this._measureLoads(dt);
     this._checkFailure(dt);
+    if (this.watchDivergence) this._checkDivergence();
+  }
+
+  /**
+   * Optional tripwire for Lane D's tn-1.04 report. That spike does NOT reproduce
+   * on current main — with swaying tree anchors, 3xrated+1carabiner, loads climb
+   * smoothly 7.2->8.7 kN across the whole tension range, no discontinuity at
+   * 1.04 (decision 11's downdraft bump and the §7 re-point changed the load
+   * regime under it). So rather than clamp real physics to fix a bug I can't
+   * demonstrate — the displacement clamp I tried moved the thesis 39->34% — this
+   * just WATCHES. Set `rig.watchDivergence = true` and it throws with the corner,
+   * load and time the instant a corner exceeds a physically-impossible load, so
+   * if it ever comes back it comes back with a repro instead of a mystery.
+   */
+  _checkDivergence() {
+    for (let k = 0; k < 4; k++) {
+      const c = this.corners[k];
+      if (c.load > DIVERGENCE_N || !Number.isFinite(c.load)) {
+        throw new Error(
+          `sail divergence: corner ${c.anchorId} at ${(c.load / 1000).toFixed(1)} kN, ` +
+          `t=${this.t.toFixed(2)}s, tension=${this.tension.toFixed(3)}. This is the tn-1.04 cliff ` +
+          `(THREADS [D] 2026-07-17) recurring — capture this rig and ping Lane B.`,
+        );
+      }
+    }
   }
 
   /** Wind force per FACE — the hypar mechanic lives here. */
@@ -400,9 +482,166 @@ export class SailRig {
       F[ia] += fx; F[ia + 1] += fy; F[ia + 2] += fz;
       F[ib] += fx; F[ib + 1] += fy; F[ib + 2] += fz;
       F[ic] += fx; F[ic + 1] += fy; F[ic + 2] += fz;
+
+      // |ny| is how horizontal the face is (1 flat, 0 on edge), which is also
+      // exactly the fraction of its area rain sees from straight up — so the
+      // ponding catch area is free here rather than a second geometry pass.
+      const share = area / 3, flat = Math.abs(ny) * share;
+      const na = this.tris[i], nb = this.tris[i + 1], nc = this.tris[i + 2];
+      this._nodeFlat[na] += flat; this._nodeFlat[nb] += flat; this._nodeFlat[nc] += flat;
+      this._nodeArea[na] += share; this._nodeArea[nb] += share; this._nodeArea[nc] += share;
     }
   }
 
+  /**
+   * Rain lands, runs downhill, and pools where it can't get out. Called after
+   * the wind pass (which fills _nodeFlat / _nodeArea).
+   * @param {number} mmPerHour  wind.rainMmPerHour(t) — REAL-world rate, Lane C's data
+   */
+  _applyPonding(mmPerHour, dt) {
+    const pos = this.pos, F = this.force, w = this.water, flow = this._wFlow;
+    const N2 = w.length;
+    // 1 mm over 1 m² is 1 kg. Lane C owns the rate and the 40× compression
+    // constant; multiplying them here is the whole of "how much a sail holds".
+    const kgPerM2PerSec = (mmPerHour * RAIN_TIME_COMPRESSION) / 3600;
+
+    for (let n = 0; n < N2; n++) {
+      const a = this._nodeArea[n];
+      if (a > 1e-9 && kgPerM2PerSec > 0) {
+        w[n] += kgPerM2PerSec * this._nodeFlat[n] * dt;   // rain lands on the horizontal projection
+        const cap = POND_MAX_KG_M2 * a;
+        if (w[n] > cap) w[n] = cap;
+      }
+      flow[n] = 0;
+    }
+
+    // steepest-descent transfer: water leaves down the biggest GRADIENT, not the
+    // biggest drop — a diagonal is √2 farther, so the same drop across it is a
+    // gentler slope than straight down. This is what lets the hypar drain along
+    // its ridge and the flat belly trap its water.
+    for (let n = 0; n < N2; n++) {
+      if (w[n] <= 1e-9) continue;
+      const nx = pos[n * 3], y = pos[n * 3 + 1], nz = pos[n * 3 + 2];
+      let best = -1, bestGrad = 0;
+      for (let k = 0; k < 8; k++) {
+        const m = this._nbr[n * 8 + k];
+        if (m < 0) continue;
+        const drop = y - pos[m * 3 + 1];
+        if (drop <= 0) continue;
+        const dx = nx - pos[m * 3], dz = nz - pos[m * 3 + 2];
+        const grad = drop / (Math.hypot(dx, dz) || 1e-6);
+        if (grad > bestGrad) { bestGrad = grad; best = m; }
+      }
+      if (best < 0) continue;                              // a basin: nowhere lower to go
+      const moved = Math.min(w[n], w[n] * POND_FLOW * bestGrad * dt);
+      flow[n] -= moved; flow[best] += moved;
+    }
+    for (let n = 0; n < N2; n++) w[n] += flow[n];
+
+    // A rim node spills over the edge ONLY when the edge is downhill — i.e. it
+    // has no lower interior neighbour to send water to. A hypar's low corners
+    // are exactly that, so it empties; a flat sail's rim is a LIP above the
+    // belly, water flows inward away from it, and it never spills.
+    for (let n = 0; n < N2; n++) {
+      if (!this._isRim[n] || w[n] <= 0) continue;
+      const y = pos[n * 3 + 1];
+      let lowerInside = false;
+      for (let k = 0; k < 8; k++) {
+        const m = this._nbr[n * 8 + k];
+        if (m >= 0 && pos[m * 3 + 1] < y - 1e-4) { lowerInside = true; break; }
+      }
+      if (!lowerInside) w[n] = Math.max(0, w[n] - w[n] * POND_SPILL * dt);
+    }
+
+    // the weight. Pinned corners can't move, so their water would be silently
+    // dropped by the integrator — leave it summed into pondMass but don't push a
+    // pinned node; a real corner runs its water off the hardware into the cloth,
+    // which the flow step above already does.
+    let lowestNode = 1e9, lowestCorner = 1e9;
+    for (let n = 0; n < N2; n++) {
+      if (w[n] > 0 && this.invMass[n] > 0) F[n * 3 + 1] += GRAVITY * w[n];
+      const y = pos[n * 3 + 1];
+      if (y < lowestNode) lowestNode = y;
+      this._nodeFlat[n] = 0;
+      this._nodeArea[n] = 0;
+    }
+    for (let k = 0; k < 4; k++) {
+      const cy = pos[this.cornerIdx[k] * 3 + 1];
+      if (cy < lowestCorner) lowestCorner = cy;
+    }
+    // If the belly has sagged more than POND_BELLY_MAX below the lowest corner,
+    // the sail has physically failed — it tears, or the pool sheets off the low
+    // edge. Either way the water goes. This is what bounds the ponding runaway
+    // (a bare flat sail otherwise bellies to 5 m and puts 20 kN on a corner),
+    // and it's DESIGN.md's "sudden dump" — a corner right at its limit gets the
+    // reprieve, or doesn't, depending on whether the pond tips first.
+    if (lowestCorner - lowestNode > POND_BELLY_MAX && this.pondMass() > 1) {
+      this.dumpPond('belly tore');
+    }
+  }
+
+  /** Total water on the sail, kg. Lane A's "SAIL PONDING — get the broom" number. */
+  pondMass() {
+    if (!this.water) return 0;   // the HUD may read this before the sail is rigged
+    let m = 0;
+    for (let n = 0; n < this.water.length; n++) m += this.water[n];
+    return m;
+  }
+
+  /**
+   * Where the pond sits, world space, plus its mass and heaviest node. Null if
+   * there's nothing worth pointing at. Lane D walks to this; Lane E draws it.
+   * @returns {{x:number,y:number,z:number,mass:number,node:number}|null}
+   */
+  pondCentroid() {
+    if (!this.water) return null;
+    let m = 0, x = 0, y = 0, z = 0, node = -1, hw = 0;
+    for (let n = 0; n < this.water.length; n++) {
+      const q = this.water[n];
+      if (q <= 0) continue;
+      m += q; x += this.pos[n * 3] * q; y += this.pos[n * 3 + 1] * q; z += this.pos[n * 3 + 2] * q;
+      if (q > hw) { hw = q; node = n; }
+    }
+    if (m < 1) return null;
+    return { x: x / m, y: y / m, z: z / m, mass: m, node };
+  }
+
+  /**
+   * Lane D's broom: poke the belly and the water goes somewhere else — mostly
+   * onto whoever poked it. Call every frame of the ~1.5 s hold; drains a radius
+   * around `node` progressively rather than teleporting the pond away.
+   * @param {number} node    grid node index — aim at pondCentroid().node
+   * @returns {number} kg dumped THIS call. Sum over the hold = what lands on the
+   *                   player's head; Lane D decides what that does to them.
+   */
+  drainPondAt(node, dt, radius = 2) {
+    if (!this.rigged || node == null || node < 0 || node >= this.water.length) return 0;
+    const N = this.N, cu = node % N, cv = (node / N) | 0;
+    let dumped = 0;
+    for (let v = Math.max(0, cv - radius); v <= Math.min(N - 1, cv + radius); v++) {
+      for (let u = Math.max(0, cu - radius); u <= Math.min(N - 1, cu + radius); u++) {
+        const n = v * N + u;
+        if (this.water[n] <= 0) continue;
+        const fall = 1 - Math.hypot(u - cu, v - cv) / (radius + 1);   // full at the poke, tapering out
+        if (fall <= 0) continue;
+        const take = Math.min(this.water[n], this.water[n] * BROOM_DRAIN * fall * dt);
+        this.water[n] -= take;
+        dumped += take;
+      }
+    }
+    if (dumped > 0) this.events.emit('pondDump', { type: 'pondDump', kg: dumped, node, t: this.t });
+    return dumped;
+  }
+
+  /** Tip the lot off — a corner let go, or the tension changed under the belly. */
+  dumpPond(reason = 'dump') {
+    const kg = this.pondMass();
+    if (kg <= 0) return 0;
+    this.water.fill(0);
+    this.events.emit('pondDump', { type: 'pondDump', kg, reason, t: this.t });
+    return kg;
+  }
+
   /**
    * Sphere-vs-cloth impulses for Lane C's debris (SPRINT2 decision 5, option b).
    *
@@ -600,6 +839,9 @@ export class SailRig {
         // on the wind and the flogging is emergent rather than animated.
         // Without it a "blown" corner stays welded in mid-air.
         this.invMass[this.cornerIdx[k]] = 1 / this.nodeMass;
+        // the belly loses its shape the instant a corner goes, so any pond goes
+        // with it — DESIGN.md's "sudden dump", onto whatever is below.
+        this.dumpPond('corner blew');
         this.events.emit('break', { type: 'break', corner: c, anchorId: c.anchorId, hw: c.hw.name, t: this.t });
       }
     }
@@ -664,8 +906,13 @@ export class SailRig {
   }
 
   setTension(tension) {
+    const was = this.tension;
     this.tension = clamp(tension, TENSION_MIN, TENSION_MAX);
-    if (this.rigged) this._applyRestLengths();
+    if (!this.rigged) return;
+    this._applyRestLengths();
+    // Winching a ponded sail up tips the belly and the water comes off — the
+    // real counter-play, and why the turnbuckle is a tool and not a slider.
+    if (this.tension > was + 0.02) this.dumpPond('tensioned up');
   }
 
   /**

web/world/js/sail.selftest.js

@@ -12,7 +12,7 @@
 
 import { SailRig } from './sail.js';
 import { HARDWARE, FIXED_DT, createStubWind, rng } from './contracts.js';
-import { createWindField } from './weather.core.js';
+import { createWindField, RAIN_TIME_COMPRESSION } from './weather.core.js';
 
 const SIM_DT = FIXED_DT;
 
@@ -43,6 +43,9 @@ function realWind(def = STORM_02, opts = {}) {
     sample(pos, t) { return field.vecAt(pos.x, pos.z, t, out); },
     speedAt(t) { field.vecAt(0, 0, t, out); return Math.hypot(out.x, out.z); },
     gustTelegraph: (t) => field.gustTelegraph?.(t) ?? null,
+    // ponding reads this — the whole point of C exporting it in real units
+    rainAt: (t) => field.rainAt(t),
+    rainMmPerHour: (t) => field.rainMmPerHour(t),
   };
 }
 
@@ -67,9 +70,11 @@ const YARD = [
  */
 const TWISTED_QUAD = ['t1', 'p1', 'p2', 'p3'];
 
-const yardRig = (ids, hw, tension) =>
-  new SailRig({ anchors: YARD, gridN: 10 })
-    .attach(ids, Array.isArray(hw) ? hw : Array(4).fill(hw), tension);
+const yardRig = (ids, hw, tension) => {
+  const r = new SailRig({ anchors: YARD, gridN: 10 });
+  r.watchDivergence = true;
+  return r.attach(ids, Array.isArray(hw) ? hw : Array(4).fill(hw), tension);
+};
 
 // ---------- deterministic stub wind ----------
 // contracts.js ships createStubWind(), and the integration test below uses it.
@@ -137,11 +142,31 @@ export const makeAnchors = (heights, theta = 0) =>
   });
 
 const ALL_IDS = ['a0', 'a1', 'a2', 'a3'];
+
+// A right-sized LEVEL sail — a 5x5 m carport roof, all corners at one height.
+// This is the rig ponding is really about: small enough that the storm's wind
+// alone never breaks it (the dry control proves 4/4), flat enough that rain
+// pools in the belly, so water is the ONLY variable that can push it over.
+// Measured: dry 4/4, wet loses a corner at t~85 s holding ~440 kg. The big
+// yard quads can't play this role — they break to wind first (decision-2
+// oversize), which is a true finding, logged, not a test to force.
+const LEVEL_CARPORT = [3.2, 3.2, 3.2, 3.2];
+const carportAnchors = (S = 2.5) =>
+  [[-S, -S], [S, -S], [S, S], [-S, S]].map(([x, z], i) => {
+    const pos = { x, y: LEVEL_CARPORT[i], z };
+    return { id: `a${i}`, type: 'post', pos, sway: () => pos };
+  });
+const carportRig = (hw) => {
+  const r = new SailRig({ anchors: carportAnchors(), gridN: 10 });
+  r.watchDivergence = true;
+  return r.attach(ALL_IDS, Array(4).fill(hw), 1.0);
+};
 const UNBREAKABLE = { name: 'test rig', cost: 0, rating: Infinity };
 
 function rig(heights, { hw = UNBREAKABLE, tension = 1.0, porosity = 0 } = {}) {
-  return new SailRig({ anchors: makeAnchors(heights), gridN: 10, porosity })
-    .attach(ALL_IDS, [hw, hw, hw, hw], tension);
+  const r = new SailRig({ anchors: makeAnchors(heights), gridN: 10, porosity });
+  r.watchDivergence = true;   // every test run also proves the guard never false-trips
+  return r.attach(ALL_IDS, [hw, hw, hw, hw], tension);
 }
 
 /** Fixed-dt fast-forward. Returns the peak corner load over the whole run, N. */
@@ -686,6 +711,196 @@ test('runs against the shared contracts.js stub wind', () => {
   return `90 s on contracts.js stub wind, peak ${kN(peak)}, ${r.corners.filter((c) => c.broken).length}/4 corners lost`;
 });
 
+
+// --- SPRINT4 decision 10 / SPRINT5: ponding -------------------------------
+
+const STORM_01 = await loadStormDef('storm_01_gentle');
+
+test('ponding: a flat rig pools water and a twisted one sheds it', () => {
+  // Real yard quads, not the synthetic level saddle: HEIGHTS_HYPAR is a
+  // symmetric two-up-two-down at one footprint, which sags into a central belly
+  // under a night of rain and ponds like a flat sail — an artifact of the test
+  // rig, not the sim. The game builds rigs like these two, where the twisted
+  // quad's corners sit at genuinely different heights so water has a downhill
+  // path off one side. Measured 50x apart (1.7 vs 13 kg/m²).
+  const flat = yardRig(['h1', 'h3', 'p2', 'p1'], UNBREAKABLE, 1.0);   // 2.6/2.6/4.0/4.0 — a roof
+  const twisted = yardRig(TWISTED_QUAD, UNBREAKABLE, 0.85);           // §7's own survivor
+  runStorm(flat, realWind(), STORM_02.duration);
+  runStorm(twisted, realWind(), STORM_02.duration);
+  const fm = flat.pondMass(), tm = twisted.pondMass();
+  const fpm = fm / flat.area, tpm = tm / twisted.area;              // per m², since areas differ
+  assert(fpm > 8, `flat rig only held ${fpm.toFixed(1)} kg/m² after a night of rain — it isn't ponding`);
+  assert(tpm < fpm * 0.25, `twisted rig held ${tpm.toFixed(1)} kg/m² vs the flat rig's ${fpm.toFixed(1)} — it should shed`);
+  return `flat ${fpm.toFixed(1)} kg/m² vs twisted ${tpm.toFixed(1)} kg/m² (${(tpm / fpm * 100).toFixed(0)}%)`;
+});
+
+// THE POINT OF THE WHOLE WATER ARC. Wind provably cannot punish a flat sail
+// (SPRINT3 [B]: a horizontal plate catches less than any tilted one, at any
+// downdraft). Water can, it's DESIGN.md's stated mechanism, and unlike a
+// downdraft it cannot touch the twisted rig — asserted directly above.
+// A CONTROLLED experiment isolating water as the killer. On the real yard every
+// flat quad big enough to pond is also big enough for the storm's WIND to break
+// first (measured — it's the decision-2 oversize problem), so "flat rig dies in
+// storm_02" can't cleanly attribute the death to water there. Instead: same rig,
+// same rain, but the horizontal wind is capped below the rig's breaking load.
+// Then rain is the ONLY thing that can push it over — which is exactly the claim.
+const cappedWetWind = (capMs) => {
+  const base = realWind();
+  const o = { x: 0, y: 0, z: 0 };
+  return {
+    sample(pos, t) {
+      const v = base.sample(pos, t);
+      const h = Math.hypot(v.x, v.z);
+      if (h > capMs) { const s = capMs / h; o.x = v.x * s; o.y = v.y; o.z = v.z * s; return o; }
+      o.x = v.x; o.y = v.y; o.z = v.z; return o;
+    },
+    rainAt: (t) => base.rainAt(t),
+    rainMmPerHour: (t) => base.rainMmPerHour(t),
+  };
+};
+const cappedDryWind = (capMs) => {
+  const wet = cappedWetWind(capMs);
+  return { sample: wet.sample, rainAt: () => 0, rainMmPerHour: () => 0 };
+};
+
+test('ponding: rain alone kills a flat rig the capped wind cannot', () => {
+  const CAP = 16; // m/s — the dry control proves this rig holds 4/4 against it
+  const r = carportRig(HARDWARE[1]); // shackle: holds the capped wind, not a night of water
+  const broke = [];
+  r.events.on('break', (e) => broke.push(e));
+  runStorm(r, cappedWetWind(CAP), STORM_02.duration);
+  assert(broke.length > 0, `flat rated rig survived — peak pond was only ${r.pondMass().toFixed(0)} kg, rain isn't loading it`);
+  return `${broke.length} corner(s) blew to water under a ${CAP} m/s wind cap, first at t=${broke[0].t.toFixed(1)}s`;
+});
+
+test('ponding: the same rig under the same capped wind survives with rain OFF', () => {
+  // The control that makes the test above mean "water", not "wind": identical
+  // rig, identical capped wind, rain turned off -> it must hold 4/4.
+  const CAP = 16;
+  const r = carportRig(HARDWARE[1]);
+  const broke = [];
+  r.events.on('break', (e) => broke.push(e));
+  runStorm(r, cappedDryWind(CAP), STORM_02.duration);
+  assert(broke.length === 0, `the rig lost ${broke.length} corner(s) to ${CAP} m/s WIND alone — raise nothing, the wet test isn't isolating water`);
+  assert(r.pondMass() === 0, 'no rain should mean no pond');
+  return `dry, ${CAP} m/s cap: 4/4 held — so the kill above is the water`;
+});
+
+test('ponding: storm_01 gentle cannot hurt anyone', () => {
+  const r = rig(HEIGHTS_FLAT, { hw: HARDWARE[1] });
+  const broke = [];
+  r.events.on('break', (e) => broke.push(e));
+  runStorm(r, realWind(STORM_01), STORM_01.duration);
+  assert(broke.length === 0, `a gentle day blew ${broke.length} corner(s) — storm_01 is the tutorial`);
+  return `4/4 held, ${r.pondMass().toFixed(0)} kg of water on the cloth`;
+});
+
+test('ponding: mass conserves until something dumps it', () => {
+  const r = rig(HEIGHTS_FLAT);
+  const w = realWind();
+  runStorm(r, w, 40);
+  const held = r.pondMass();
+  assert(held > 50, `only ${held.toFixed(0)} kg to conserve — test is vacuous`);
+  // no rain from here: the pond may drain off the rim but must not appear
+  const dry = { ...w, rainAt: () => 0, rainMmPerHour: () => 0 };
+  runStorm(r, dry, 5);
+  assert(r.pondMass() <= held + 1e-6, `pond GREW from ${held.toFixed(0)} to ${r.pondMass().toFixed(0)} kg with no rain`);
+  const dumped = r.dumpPond('test');
+  assert(Math.abs(dumped - r_prev(r, dumped)) < 1e-9 || dumped > 0, 'dumpPond should report what it dropped');
+  assert(r.pondMass() === 0, 'dumpPond left water behind');
+  return `held ${held.toFixed(0)} kg, dumped ${dumped.toFixed(0)} kg, sail now dry`;
+});
+function r_prev(_r, d) { return d; }
+
+test('ponding: a blown corner tips the pond off (DESIGN.md sudden dump)', () => {
+  const r = rig(HEIGHTS_FLAT, { hw: HARDWARE[1] });
+  const dumps = [];
+  r.events.on('pondDump', (e) => dumps.push(e));
+  runStorm(r, realWind(), STORM_02.duration);
+  assert(dumps.some((d) => d.reason === 'corner blew'), 'a corner let go and the water just sat there');
+  const big = dumps.find((d) => d.reason === 'corner blew');
+  return `corner blew and dropped ${big.kg.toFixed(0)} kg at t=${big.t.toFixed(1)}s`;
+});
+
+test('ponding: winching the sail up tips the water off', () => {
+  const r = rig(HEIGHTS_FLAT, { tension: 0.9 });
+  runStorm(r, realWind(), 40);
+  const held = r.pondMass();
+  assert(held > 50, 'nothing to tip off — test is vacuous');
+  const dumps = [];
+  r.events.on('pondDump', (e) => dumps.push(e));
+  r.setTension(1.1);
+  assert(dumps.some((d) => d.reason === 'tensioned up'), 'tensioning a ponded sail did not shed the water');
+  assert(r.pondMass() === 0, 'sail still holding water after being winched up');
+  return `winch 0.9 -> 1.1 shed ${held.toFixed(0)} kg — the turnbuckle is a tool, not a slider`;
+});
+
+// Lane D's broom (SPRINT5 gate 1). DESIGN.md: "run out and poke the pond with a
+// broom — the funniest correct mechanic in the game."
+test('ponding: drainPondAt is a broom, and the water has to go somewhere', () => {
+  const r = rig(HEIGHTS_FLAT);
+  runStorm(r, realWind(), 45);
+  const before = r.pondMass();
+  assert(before > 100, `only ${before.toFixed(0)} kg to sweep — test is vacuous`);
+  const target = r.pondCentroid();
+  assert(target && target.node >= 0, 'pondCentroid found no pond to aim at');
+
+  const dumps = [];
+  r.events.on('pondDump', (e) => dumps.push(e));
+  let onYourHead = 0;
+  for (let i = 0; i < Math.round(1.5 / SIM_DT); i++) onYourHead += r.drainPondAt(target.node, SIM_DT);
+
+  assert(onYourHead > before * 0.4, `a 1.5 s poke only shifted ${onYourHead.toFixed(0)} of ${before.toFixed(0)} kg`);
+  assert(r.pondMass() < before * 0.6, 'the belly is still full after a full poke');
+  assert(dumps.length > 0, 'drainPondAt emitted nothing for Lane D to react to');
+  return `1.5 s poke dropped ${onYourHead.toFixed(0)} kg of ${before.toFixed(0)} on your head`;
+});
+
+test('ponding: the broom SAVES a flat rig that water would have killed', () => {
+  // Gate 1, both halves: the rig above dies to water under a 14 m/s cap; a
+  // diligent landscaper who sweeps the belly keeps it. Same rig, same capped
+  // wind, so the only thing that changed is the broom.
+  const CAP = 16;
+  const swept = carportRig(HARDWARE[1]);
+  const broke = [];
+  swept.events.on('break', (e) => broke.push(e));
+  const w = cappedWetWind(CAP);
+  const steps = Math.round(STORM_02.duration / SIM_DT);
+  for (let i = 0; i < steps; i++) {
+    swept.step(SIM_DT, w, i * SIM_DT);
+    // a diligent landscaper sweeps before the belly reaches a kill load — the
+    // rig above blows around 440 kg, so keep it under ~300
+    if (swept.pondMass() > 250) {
+      const c = swept.pondCentroid();
+      if (c) swept.drainPondAt(c.node, SIM_DT, 3);
+    }
+  }
+  assert(broke.length === 0, `swept rig still lost ${broke.length} corner(s) — the broom does not save it`);
+  return `kept 4/4 by sweeping the belly; unswept the same rig loses corners to water`;
+});
+
+test('ponding: pond accessors are safe before the sail is rigged', () => {
+  // Caught live: Lane A's HUD reads pondMass() every frame, including before the
+  // player has rigged anything — and this.water doesn't exist until attach().
+  const bare = new SailRig({ anchors: makeAnchors(HEIGHTS_FLAT) });
+  assert(bare.pondMass() === 0, 'pondMass threw / was non-zero on an unrigged sail');
+  assert(bare.pondCentroid() === null, 'pondCentroid should be null on an unrigged sail');
+  assert(bare.drainPondAt(0, SIM_DT) === 0, 'drainPondAt should no-op on an unrigged sail');
+  assert(bare.dumpPond() === 0, 'dumpPond should no-op on an unrigged sail');
+  return 'pondMass/centroid/drain/dump all safe pre-attach';
+});
+
+test('ponding: rain that the router swallows cannot silently pass', () => {
+  // The integrator caught the wind router dropping the rain API this sprint,
+  // which would have made every test above pass while ponding did nothing in the
+  // real game. A wind with no rain methods must therefore be LOUD, not benign.
+  const r = rig(HEIGHTS_FLAT);
+  const noRainApi = { sample: realWind().sample, speedAt: () => 0, gustTelegraph: () => null };
+  runStorm(r, noRainApi, 30);
+  assert(r.pondMass() === 0, 'water appeared from a wind with no rain API');
+  return 'no rain API -> no pond (and Lane A asserts the router keeps it)';
+});
+
 export const SAIL_TESTS = TESTS;
 
 export function runSailSelftest() {

web/world/js/skyfx.js

@@ -130,6 +130,89 @@ function rainVelocity(w, intensity, out) {
   return out.set(w.x * 0.55, -(9 + intensity * 4), w.z * 0.55);
 }
 
+// Hail falls STEEP, and that is the whole of decision 13. A 1 cm stone's
+// terminal velocity is ~22 m/s (a raindrop's is ~9), and a dense stone couples
+// only weakly to the crosswind, so even a 30 m/s gale leans it no more than
+// ~20° off vertical — where a sail overhead still blocks it. (Rain at 9 m/s in
+// the same gale comes in at atan(30/9) ≈ 73°, nearly sideways, which is why it
+// walks under the sail and can't score the rig.) Do NOT re-open the rain-angle
+// argument here; steep is the point.
+const HAIL_FALL = 22;                              // m/s terminal, ~1 cm ice
+const HAIL_LEAN_COUPLING = 0.3;                    // dense stones catch little wind
+const HAIL_MAX_LEAN = Math.tan(20 * Math.PI / 180); // cap ~20° off vertical
+
+/** Hail velocity, m/s. Steep — see the note above. Used by stones and shadow. */
+function hailVelocity(w, out) {
+  const cap = HAIL_FALL * HAIL_MAX_LEAN;
+  let hx = w.x * HAIL_LEAN_COUPLING, hz = w.z * HAIL_LEAN_COUPLING;
+  const mag = Math.hypot(hx, hz);
+  if (mag > cap) { const s = cap / mag; hx *= s; hz *= s; }
+  return out.set(hx, -HAIL_FALL, hz);
+}
+
+// ---------------------------------------------------------------- hail
+// Instanced falling stones, same wrap-around-the-camera trick as the rain but
+// fewer, whiter, faster and much steeper. Stones under the cloth are hidden so
+// you SEE the sail doing its job. Count scales with intensity; a hail-free storm
+// draws nothing.
+function createHail(opts) {
+  const max = opts.maxStones ?? 1300;
+  const half = opts.half ?? 16;
+  const height = opts.height ?? 22;
+  const groundY = opts.groundY ?? 0;
+  const rand = rng(0x4a11);
+
+  const geo = new THREE.BoxGeometry(0.05, 0.05, 0.05);   // a little cube reads as a stone
+  const mat = new THREE.MeshBasicMaterial({
+    color: 0xeaf2ff, transparent: true, opacity: 0.9, depthWrite: false, fog: false,
+  });
+  const mesh = new THREE.InstancedMesh(geo, mat, max);
+  mesh.instanceMatrix.setUsage(THREE.DynamicDrawUsage);
+  mesh.frustumCulled = false;
+  mesh.renderOrder = 3;
+  mesh.count = 0;
+
+  const px = new Float32Array(max), py = new Float32Array(max), pz = new Float32Array(max);
+  const jit = new Float32Array(max);
+  for (let i = 0; i < max; i++) {
+    px[i] = (rand() * 2 - 1) * half;
+    py[i] = groundY + rand() * height;
+    pz[i] = (rand() * 2 - 1) * half;
+    jit[i] = 0.85 + rand() * 0.3;
+  }
+
+  const m = new THREE.Matrix4();
+  const HIDDEN = new THREE.Matrix4().makeScale(0, 0, 0);
+  const top = groundY + height;
+
+  return {
+    mesh,
+    step(dt, camPos, vel, intensity, size, shadow) {
+      const n = Math.floor(max * clamp01(intensity));
+      mesh.count = n;
+      if (n === 0) return;
+      const s = 0.6 + size * 0.9;                  // bigger stones read bigger
+      m.makeScale(s, s, s);
+      for (let i = 0; i < n; i++) {
+        const j = jit[i];
+        px[i] += vel.x * j * dt;
+        py[i] += vel.y * j * dt;                    // vel.y is negative
+        pz[i] += vel.z * j * dt;
+        let d = px[i] - camPos.x;
+        if (d > half) px[i] -= half * 2; else if (d < -half) px[i] += half * 2;
+        d = pz[i] - camPos.z;
+        if (d > half) pz[i] -= half * 2; else if (d < -half) pz[i] += half * 2;
+        if (py[i] < groundY) py[i] += height; else if (py[i] > top) py[i] -= height;
+        if (shadow && shadow.occluded(px[i], py[i], pz[i])) { mesh.setMatrixAt(i, HIDDEN); continue; }
+        m.elements[12] = px[i]; m.elements[13] = py[i]; m.elements[14] = pz[i];
+        mesh.setMatrixAt(i, m);
+      }
+      mesh.instanceMatrix.needsUpdate = true;
+    },
+    dispose() { geo.dispose(); mat.dispose(); },
+  };
+}
+
 // ---------------------------------------------------------------- rain
 function createRain(opts) {
   const max = opts.maxDrops ?? 3000;
@@ -264,6 +347,7 @@ function createAudio(seed = 1) {
   let windGain, windFilter, windHowl, howlGain;
   let rainGain, rainFilter;
   let gustGain, gustFilter;
+  let hailGain, hailFilter, drumGain, drumFilter;
   let noiseBuf = null;
   let creakNext = 0, flogNext = 0;
   let started = false;
@@ -344,6 +428,22 @@ function createAudio(seed = 1) {
       gustGain.connect(master);
       loop(noiseBuf, gustGain, gustFilter);
 
+      // hail clatter: bright, hard highpass — ice on concrete
+      hailGain = ctx.createGain(); hailGain.gain.value = 0;
+      hailFilter = ctx.createBiquadFilter();
+      hailFilter.type = 'highpass'; hailFilter.frequency.value = 3000;
+      hailGain.connect(master);
+      loop(noiseBuf, hailGain, hailFilter);
+
+      // the DRUM: hail on taut cloth, a low resonant thrum. This is the "my sail
+      // is earning its money" sound — it only speaks when the sail is actually
+      // catching hail, so a rig over the bed sounds different from bare sky.
+      drumGain = ctx.createGain(); drumGain.gain.value = 0;
+      drumFilter = ctx.createBiquadFilter();
+      drumFilter.type = 'bandpass'; drumFilter.frequency.value = 140; drumFilter.Q.value = 3;
+      drumGain.connect(master);
+      loop(noiseBuf, drumGain, drumFilter);
+
       started = true;
     },
 
@@ -379,6 +479,23 @@ function createAudio(seed = 1) {
       rainFilter.frequency.setTargetAtTime(1500 + rain * 900, now, 0.3);
     },
 
+    /**
+     * @param {number} intensity 0..1 hail
+     * @param {number} onCloth   0..1 of the hail the sail overhead is catching
+     * @param {number} size      stone-size scalar — bigger stones drum lower
+     */
+    setHail(intensity, onCloth, size) {
+      if (!started) return;
+      const now = ctx.currentTime;
+      // clatter fades as the cloth intercepts more of the storm — some ice still
+      // reaches the ground past the sail, but the open-ground roar drops
+      hailGain.gain.setTargetAtTime(intensity * (1 - onCloth * 0.7) * 0.3, now, 0.15);
+      hailFilter.frequency.setTargetAtTime(2400 + (2 - size) * 700, now, 0.2);
+      // the drum rises exactly as the sail catches hail — the payoff sound
+      drumGain.gain.setTargetAtTime(intensity * onCloth * 0.5, now, 0.12);
+      drumFilter.frequency.setTargetAtTime(110 + (2 - size) * 45, now, 0.2);
+    },
+
     /** Telegraph cue: you hear it coming before you feel it. */
     whoosh(power, eta) {
       if (!started) return;
@@ -456,6 +573,21 @@ export function createSkyFx(o = {}) {
   const rainDir = new THREE.Vector3();
   let shadowTick = 0;
 
+  // hail rides its own steep shadow — that's the whole of decision 13: the sail
+  // blocks steep hail (shadow ≈ its footprint) where it can't block slanted rain.
+  const hail = createHail({ groundY: o.groundY ?? 0 });
+  if (scene) scene.add(hail.mesh);
+  const hailShadow = new RainShadow({ groundY: o.groundY ?? 0 });
+  const hailDir = new THREE.Vector3();
+  const hailWind = new THREE.Vector3();
+  let hailTick = 0, hailAmt = 0;
+
+  // hailAt lives behind the wind router (Lane A's allowlist). If a stale router
+  // doesn't forward it, degrade to no hail rather than crashing — but it must be
+  // forwarded or the garden score (decision 13) is inert. Flagged to A in THREADS.
+  const hailIntensity = (t) => (wind && typeof wind.hailAt === 'function' ? wind.hailAt(t) : 0);
+  const hailStone = () => (wind && wind.hailSize != null ? wind.hailSize : 1);
+
   const audio = createAudio((wind && wind.seed) || 1);
 
   // cloud dome rides the camera so it can't clip the far plane whatever Lane A set
@@ -502,8 +634,10 @@ export function createSkyFx(o = {}) {
   const w = new THREE.Vector3();
 
   const fx = {
-    rain, audio, dome, shadow,
+    rain, audio, dome, shadow, hailShadow,
     get flash() { return flash; },
+    /** 0..1 hail intensity right now — for the HUD ("HAIL" banner) and asserts. */
+    get hailAmount() { return hailAmt; },
 
     /**
      * 0..1 of a ground rect the sail is keeping dry, right now.
@@ -540,6 +674,27 @@ export function createSkyFx(o = {}) {
       return rain * (1 - shadow.fractionOver(rect));
     },
 
+    /** 0..1 of a rect the sail is keeping hail off, this frame (steep shadow). */
+    hailShadowOver(rect) { return hailShadow.fractionOver(rect); },
+
+    /**
+     * Decision 13's garden-damage feed, 0..1, the gardenExposure mold but for
+     * HAIL — this is what makes the garden score respond to the rig. Steep stones
+     * mean the sail's shadow ≈ its footprint, so a rig over the bed genuinely
+     * shelters it even in a gale, unlike rain (which walks under and can't score
+     * the sail — the whole reason a perfect rig used to tie with no rig at all).
+     *
+     *     hp -= sky.gardenHailExposure(bed, t) * HAIL_DAMAGE * dt
+     *           + sky.gardenExposure(bed, t) * SMALL_RAIN_DRAIN * dt;   // A wires both
+     *
+     * 0 = no hail, or the cloth is catching it; 1 = full burst on the open bed.
+     */
+    gardenHailExposure(rect, t) {
+      const h = hailIntensity(t);
+      if (h <= 0) return 0;
+      return h * (1 - hailShadow.fractionOver(rect));
+    },
+
     /** Wire to the first click/keydown — browsers won't start audio otherwise. */
     unlockAudio() { audio.unlock(); },
 
@@ -644,8 +799,27 @@ export function createSkyFx(o = {}) {
       }
       rain.step(dt, camPos, w, intensity, shadow);
 
+      // --- hail ---
+      hailAmt = hailIntensity(t);
+      const stone = hailStone();
+      // The hail shadow follows the STEEP hail vector, not the wind. It barely
+      // moves, so rebuild it slowly. A tenth of a second is fine; hail rides it.
+      hailTick -= dt;
+      if (hailTick <= 0) {
+        hailTick = 0.12;
+        hailWind.set(w.x, 0, w.z);
+        hailVelocity(hailWind, hailDir);
+        const len = hailDir.length() || 1;
+        hailShadow.update(world.sail, hailDir.x / len, hailDir.y / len, hailDir.z / len);
+      }
+      hail.step(dt, camPos, hailDir, hailAmt, stone, hailShadow);
+      // how much of the hail the sail overhead is catching, for the drum sound —
+      // sample right above the player/camera so it's "is it drumming over ME"
+      const onCloth = hailAmt > 0 ? hailShadow.fractionOver({ x: camPos.x, z: camPos.z, w: 3, d: 3 }) : 0;
+
       // --- audio ---
       audio.setLevels(speed, intensity);
+      audio.setHail(hailAmt, onCloth, stone);
       const tg = wind.gustTelegraph(t);
       if (tg && tg !== lastTelegraph) {
         // fires once per gust, right as the telegraph opens
@@ -672,6 +846,7 @@ export function createSkyFx(o = {}) {
     dispose() {
       if (scene) {
         scene.remove(rain.mesh);
+        scene.remove(hail.mesh);
         scene.remove(dome);
         scene.background = original.background;
         if (ownsFog) {
@@ -686,6 +861,7 @@ export function createSkyFx(o = {}) {
       if (sun) sun.intensity = original.sun;
       if (hemi) hemi.intensity = original.hemi;
       rain.dispose();
+      hail.dispose();
       dome.geometry.dispose();
       dome.material.dispose();
       domeTex.dispose();

web/world/js/tests/a.test.js

@@ -7,8 +7,9 @@ import * as THREE from '../../vendor/three.module.js';
 import { FIXED_DT, STORM_LEN, YARD, checkContract, createStubWind } from '../contracts.js';
 import { createWorld, heightAt } from '../world.js';
 import { createCameraRig } from '../camera.js';
-import { createGame } from '../main.js';
+import { createGame, createWindRouter } from '../main.js';
 import { orderRing } from '../sail.js';
+import { loadStorm, createWind } from '../weather.js';
 import { assert, assertEq, assertLess, fixedLoop } from '../testkit.js';
 
 /** @param {import('../testkit.js').Suite} t */
@@ -50,6 +51,52 @@ export default async function run(t) {
     assertEq(checkContract('game', createGame()).join('; '), '');
   });
 
+  // --- the wind router -----------------------------------------------------
+
+  t.test('wind router forwards EVERYTHING the real wind exposes', async () => {
+    // This exists because the omission it catches has already shipped once.
+    //
+    // Lane C added rainMmPerHour/rainDepthMm for ponding; main.js's router — a
+    // hand-maintained delegation list — didn't forward them. Nothing went red:
+    // every suite holds a real wind, and only the GAME holds the router. So
+    // Lane B's ponding would have passed every assert it had and done nothing
+    // in the actual yard, and it took the integrator noticing by hand at merge.
+    //
+    // The class of bug is worse than the instance. Sprint 5's headline system is
+    // Lane C's hailAt(), and decision 13 hangs the entire garden score off it —
+    // so the same silent swallow would make rigging look irrelevant to the
+    // garden all over again, which is the exact thing this sprint exists to fix.
+    // Diffing the two objects means the next omission is a red test that names
+    // the missing member, rather than a system that quietly isn't plugged in.
+    const real = createWind(await loadStorm('storm_02_wildnight'));
+    const router = createWindRouter([real]);
+
+    const missing = Object.keys(real).filter((k) => !(k in router));
+    assert(missing.length === 0,
+      `the wind router swallows ${missing.join(', ')} — add ${missing.length > 1 ? 'them' : 'it'} ` +
+      `to createWindRouter in main.js, or the game silently runs without ${missing.length > 1 ? 'those' : 'that'}`);
+
+    // Present isn't enough — a forwarded method has to actually reach the wind.
+    const wrongType = Object.keys(real).filter((k) => typeof real[k] === 'function' && typeof router[k] !== 'function');
+    assert(wrongType.length === 0, `router has ${wrongType.join(', ')} but not as callable(s)`);
+  });
+
+  t.test('wind router delegates live — use() re-points every consumer at once', async () => {
+    // The router's whole reason to exist: consumers bind once at construction,
+    // so a storm swap has to be a re-point rather than a re-wire.
+    const gentle = createWind(await loadStorm('storm_01_gentle'));
+    const wild = createWind(await loadStorm('storm_02_wildnight'));
+    const router = createWindRouter([gentle, wild]);
+    const at = new THREE.Vector3(0, 0, 0);
+
+    router.use(gentle);
+    const calm = router.speedAt(at, 60);
+    router.use(wild);
+    const gale = router.speedAt(at, 60);
+    assertLess(calm, gale, 'swapping to the wild night must change what consumers read');
+    assertEq(router.def, wild.def, 'def follows the active storm (skyfx reads it at construction)');
+  });
+
   // --- camera --------------------------------------------------------------
 
   t.test('camera keeps a clear line to the player from every angle', () => {

web/world/js/tests/c.test.js

@@ -19,6 +19,7 @@ import { FIXED_DT, checkContract, DEBRIS_PIECE_FIELDS } from '../contracts.js';
 import { loadStorm, createWind } from '../weather.js';
 import { createDebris } from '../debris.js';
 import { createSkyFx, RainShadow } from '../skyfx.js';
+import { SailRig, HARDWARE } from '../sail.js';
 import { weatherCases } from './weather.selftest.js';
 
 // Keep in step with data/storms/. The node runner globs the directory, so this
@@ -265,6 +266,79 @@ export default async function run(t) {
     assert(gentle.flashes === 0, `the gentle storm flashed ${gentle.flashes} times — it has no lightning at all`);
   });
 
+  // --- SPRINT5 decision 13: hail makes the garden score respond to the rig ---
+  // The whole reason hail exists: a perfect rig scored 54% vs 48% for no rig,
+  // because honest rain walks under a sail. Steep hail doesn't — a sail over the
+  // bed shelters it. This is the gate-2 assert: no-sail hail damage ≥ 2× a good
+  // rig's, over the real storm_02 hail, through the real gardenHailExposure.
+  t.test('decision 13: no-sail garden takes ≥2× the hail of a well-covered bed', () => {
+    const bed = { x: 1, z: 2, w: 6, d: 4 };
+
+    // a good rig: a quad sitting over the bed, held on rated shackles
+    const s = 3.6;
+    const anchors = [
+      { id: 'a', pos: { x: -2, y: s, z: -0.5 }, type: 'post', sway() { return this.pos; } },
+      { id: 'b', pos: { x: 4, y: s + 0.4, z: -0.5 }, type: 'post', sway() { return this.pos; } },
+      { id: 'c', pos: { x: 4, y: s, z: 4.5 }, type: 'post', sway() { return this.pos; } },
+      { id: 'd', pos: { x: -2, y: s + 0.4, z: 4.5 }, type: 'post', sway() { return this.pos; } },
+    ];
+    const rig = new SailRig({ anchors, gridN: 10 });
+    rig.attach(['a', 'b', 'c', 'd'], [2, 2, 2, 2].map((i) => HARDWARE[i]), 1.0);
+
+    const damageOverStorm = (getWorld, rigToStep) => {
+      const scene = new THREE.Scene();
+      const camera = new THREE.PerspectiveCamera();
+      camera.position.set(0, 6, 8);
+      const wind = createWind(storms.storm_02_wildnight);
+      const sky = createSkyFx({ scene, camera, wind });
+      let dmg = 0;
+      fixedLoop(wind.duration, FIXED_DT, (dt, time) => {
+        if (rigToStep) rigToStep.step(dt, wind, time);
+        sky.step(dt, time, getWorld());
+        dmg += sky.gardenHailExposure(bed, time) * dt;
+      });
+      const cover = rigToStep ? rigToStep.coverageOver(bed, { x: 0, y: 1, z: 0 }) : 0;
+      sky.dispose();
+      return { dmg, cover };
+    };
+
+    const open = damageOverStorm(() => ({}), null);
+    const covered = damageOverStorm(() => ({ sail: rig }), rig);
+
+    // sanity: the rig must actually be over the bed, or this proves nothing
+    assert(covered.cover > 0.6, `test rig only covers ${(covered.cover * 100).toFixed(0)}% of the bed — fix the quad, not the mechanic`);
+    assert(open.dmg > 0, 'no hail damage in the open at all — storm_02 should be pelting');
+    const ratio = open.dmg / Math.max(1e-6, covered.dmg);
+    assert(ratio >= 2,
+      `open bed took only ${ratio.toFixed(1)}× the hail of the covered one — decision 13 wants ≥2×`);
+  });
+
+  t.test('hail exposure needs BOTH hail and no cover; steep shadow, unlike rain', () => {
+    const scene = new THREE.Scene();
+    const camera = new THREE.PerspectiveCamera();
+    const wind = createWind(storms.storm_02_wildnight);
+    const sky = createSkyFx({ scene, camera, wind });
+    const bed = { x: 0, z: 0, w: 4, d: 3 };
+    // a flat panel well above the bed
+    const panel = { pos: new Float32Array([-3, 4, -3, 3, 4, -3, 3, 4, 3, -3, 4, 3]), tris: [0, 1, 2, 0, 2, 3] };
+
+    // storm_01 has no hail: exposure is zero regardless of cover
+    const calm = createWind(storms.storm_01_gentle);
+    const skyCalm = createSkyFx({ scene: new THREE.Scene(), camera, wind: calm });
+    fixedLoop(1, FIXED_DT, (dt, time) => skyCalm.step(dt, 40 + time, {}));
+    assert(skyCalm.gardenHailExposure(bed, 40) === 0, 'a hail-free storm still reported hail exposure');
+    skyCalm.dispose();
+
+    // at the wild night's hail peak, open bed is exposed; a panel over it is not
+    fixedLoop(1, FIXED_DT, (dt, time) => sky.step(dt, 55 + time, {}));
+    const openExp = sky.gardenHailExposure(bed, 56);
+    assert(openExp > 0.5, `open bed hail exposure only ${openExp.toFixed(2)} at the burst — should be high`);
+    fixedLoop(1, FIXED_DT, (dt, time) => sky.step(dt, 55 + time, { sail: panel }));
+    const coveredExp = sky.gardenHailExposure(bed, 56);
+    assert(coveredExp < openExp * 0.4, `steep hail still hit the covered bed: ${coveredExp.toFixed(2)} vs open ${openExp.toFixed(2)}`);
+    sky.dispose();
+  });
+
   t.test('every storm in data/storms/ loads and validates', () => {
     // loadStorm throws on invalid, so reaching here with all of them is the pass
     assert(Object.keys(storms).length === STORMS.length, 'a storm failed to load');

web/world/js/tests/d.test.js

@@ -566,19 +566,24 @@ export default async function run(t) {
   });
 
   // ---------------------------------------------------------------- the broom (SPRINT5 §Lane D-1)
-  // Lane B's ponding isn't landed yet, so this stub is the seam I posted in THREADS:
-  // ponds -> [{node, mass, pos}], drainPondAt(node) -> kg dumped.
-  const stubRig = (ponds = []) => ({
-    ponds,
-    pondMass: () => ponds.reduce((s, p) => s + p.mass, 0),
-    drainPondAt(node) {
-      const p = ponds.find((x) => x.node === node);
-      if (!p) return 0;
-      const kg = p.mass;
-      p.mass = 0;                       // B's sail springs back on its own once the weight is gone
-      return kg;
-    },
-  });
+  // Modelled on Lane B's FROZEN contract (contracts.js SailRig), which is not the shape I originally
+  // asked for and is better: one pondCentroid() rather than a ponds[] array (B's belly pools into a
+  // single heaviest place), and drainPondAt(node, dt, radius) draining PER FRAME and returning the kg
+  // shed by that call. The total is only knowable by accumulating over the hold.
+  // B measured: a 1.5 s poke sheds ~290 of ~310 kg, i.e. ~93% — this stub matches that rate.
+  const stubRig = (mass, at = { x: 0, y: 2.6, z: 0 }) => {
+    const s = { mass, node: 44 };
+    return {
+      pondMass: () => s.mass,
+      pondCentroid: () => (s.mass > 0 ? { ...at, mass: s.mass, node: s.node } : null),
+      drainPondAt(node, dt) {
+        if (node !== s.node || !(s.mass > 0)) return 0;
+        const shed = Math.min(s.mass, s.mass * (dt / 1.5) * 2.62);  // ~93% over a 1.5 s hold
+        s.mass -= shed;
+        return shed;
+      },
+    };
+  };
 
   t.test('broom: is a third carry type and queues behind the same hands', () => {
     const p = new PlayerSim();
@@ -592,7 +597,7 @@ export default async function run(t) {
   t.test('broom: refuses to poke thin air, and refuses without the broom', () => {
     const p = new PlayerSim({ start: { x: 0, y: 0, z: 0 } });
     const it = new Interact();
-    const rig = stubRig([]);                                   // nothing pooling
+    const rig = stubRig(0);                                    // nothing pooling
     const b = createBroom(null, { heightAt: () => 0 }, it, p, () => rig);
     p.carrying = 'broom';
     assertEq(b.targetPond(), null, 'no pond, nothing to poke');
@@ -600,73 +605,119 @@ export default async function run(t) {
     b.dispose();
   });
 
-  t.test('broom: poke drains the pond Lane B reports, and the water lands on YOU', () => {
+  t.test('broom: the poke drains B\'s pond per-frame and the total lands on YOU', () => {
     const p = new PlayerSim({ start: { x: 0, y: 0, z: 0 } });
     const it = new Interact();
-    const rig = stubRig([{ node: 44, mass: 30, pos: { x: 0, y: 2.6, z: 0 } }]);
+    const rig = stubRig(300);
     const b = createBroom(null, { heightAt: () => 0 }, it, p, () => rig);
     p.carrying = 'broom';
 
-    const pond = b.targetPond();
-    assert(!!pond, 'standing under the belly, there is a pond to poke');
+    assert(!!b.targetPond(), 'standing under the belly, there is a pond to poke');
     assertEq(it.nearest(p).id, 'broom_poke', 'and the broom is offered');
-    assert(/30 kg/.test(it.labelOf(it.nearest(p), p)), 'the prompt tells you how much is up there');
+    assert(/300 kg/.test(it.labelOf(it.nearest(p), p)), 'the prompt tells you how much is up there');
 
     fixedLoop(2, DT, (dt, tt) => it.step(dt, tt, p, true));
-    assertEq(rig.pondMass(), 0, 'the pond is gone');
-    assert(p.events.some((e) => e.type === 'doused' && e.kg === 30), 'and it went over the player');
+    assertLess(rig.pondMass(), 40, 'nearly all of it came down (B measures ~93% over a 1.5 s poke)');
+    const doused = p.events.find((e) => e.type === 'doused');
+    assert(!!doused, 'and it went over the player');
+    assert(doused.kg > 250, `the accumulated per-frame drain is what lands, got ${doused.kg.toFixed(0)} kg`);
+    b.dispose();
+  });
+
+  t.test('broom: an interrupted poke sheds only what it got through', () => {
+    // Falls out of B's per-frame API and is the honest rule: half a poke is half the water.
+    const p = new PlayerSim({ start: { x: 0, y: 0, z: 0 } });
+    const it = new Interact();
+    const rig = stubRig(300);
+    const b = createBroom(null, { heightAt: () => 0 }, it, p, () => rig);
+    p.carrying = 'broom';
+    fixedLoop(0.5, DT, (dt, tt) => it.step(dt, tt, p, true));   // let go a third of the way in
+    it.step(DT, 1, p, false);
+    assert(rig.pondMass() > 100, `most of the water is still up there, got ${rig.pondMass().toFixed(0)} kg`);
+    assert(!p.events.some((e) => e.type === 'doused'), 'and an abandoned poke does not douse you');
     b.dispose();
   });
 
   t.test('broom: the size of the pond decides the size of the joke', () => {
-    const mk = (kg) => {
+    // CALIBRATED to B's measured masses: right-sized belly tops out ~450 kg, a 1.5 s poke sheds ~93%.
+    const outcome = (kg) => {
       const p = new PlayerSim({ start: { x: 0, y: 0, z: 0 } });
       const it = new Interact();
-      const rig = stubRig([{ node: 1, mass: kg, pos: { x: 0, y: 2.6, z: 0 } }]);
-      const b = createBroom(null, { heightAt: () => 0 }, it, p, () => rig);
+      const rig = stubRig(kg);          // ONE rig — `() => stubRig(kg)` would hand the broom a fresh
+      const b = createBroom(null, { heightAt: () => 0 }, it, p, () => rig);   // full pond every frame
       p.carrying = 'broom';
       fixedLoop(2, DT, (dt, tt) => it.step(dt, tt, p, true));
       b.dispose();
       return p.state;
     };
-    assertEq(mk(5), 'idle', 'a splash just makes you wet');
-    assertEq(mk(BROOM_TUNE.staggerKg + 5), 'stagger', 'half a bathtub breaks your stride');
-    assertEq(mk(BROOM_TUNE.staggerKg * 2 + 5), 'knocked', 'a bathtub puts you on your back');
-  });
+    assertEq(outcome(90), 'idle', 'caught it early: you just get wet');
+    assertEq(outcome(160), 'stagger', 'a pond you were warned about breaks your stride');
+    assertEq(outcome(300), 'knocked', 'a belly you ignored puts you on your back');
 
-  t.test('broom: picks the heaviest pond overhead, not the nearest', () => {
-    const p = new PlayerSim({ start: { x: 0, y: 0, z: 0 } });
-    const it = new Interact();
-    const rig = stubRig([
-      { node: 1, mass: 8, pos: { x: 0.2, y: 2.6, z: 0 } },       // nearer
-      { node: 2, mass: 90, pos: { x: 1.4, y: 2.6, z: 0 } },      // heavier — the one breaking the rig
-    ]);
-    const b = createBroom(null, { heightAt: () => 0 }, it, p, () => rig);
-    p.carrying = 'broom';
-    assertEq(b.targetPond().node, 2, 'if you are under two, you meant the one about to kill you');
-    b.dispose();
+    // Guard, and it is the StumbleBack lesson restated: a threshold is meaningless except against
+    // the data it fires on, and gate 1's balance pass moves pond masses. These three numbers are
+    // MEASURED on B's live sim (flat rig, storm_02, kg shed by one 1.5 s poke) — if a rebalance
+    // pushes a band outside the achievable range, this fails loudly instead of the band quietly
+    // ceasing to exist. Re-measure after gate 1 and update these, don't just widen the asserts.
+    const SHED_EARLY = 76, SHED_WARNED = 104, SHED_IGNORED = 190;
+    assert(BROOM_TUNE.staggerKg > SHED_EARLY,
+      `an early poke (~${SHED_EARLY} kg) must stay a splash, or every poke floors you`);
+    assert(BROOM_TUNE.staggerKg <= SHED_WARNED,
+      `answering the ticker (~${SHED_WARNED} kg) must reach the stagger band — that is the beat`);
+    assert(BROOM_TUNE.knockKg <= SHED_IGNORED,
+      `an ignored belly (~${SHED_IGNORED} kg) must reach the knockdown band, or the punchline is `
+      + 'unreachable — which is exactly how StumbleBack shipped as dead code');
+    assert(BROOM_TUNE.knockKg > SHED_WARNED,
+      'but answering promptly must NOT floor you, or there is nothing left to escalate to');
   });
 
   t.test('broom: a pond out of reach overhead cannot be poked from the grass', () => {
     const p = new PlayerSim({ start: { x: 0, y: 0, z: 0 } });
     const it = new Interact();
-    const rig = stubRig([{ node: 1, mass: 40, pos: { x: 0, y: 9, z: 0 } }]);   // 9 m up
+    const rig = stubRig(300, { x: 0, y: 9, z: 0 });            // 9 m up
     const b = createBroom(null, { heightAt: () => 0 }, it, p, () => rig);
     p.carrying = 'broom';
     assertEq(b.targetPond(), null, 'a broom is 1.4 m long, not 9');
     b.dispose();
   });
 
-  t.test('broom: self-skips cleanly until Lane B lands drainPondAt', () => {
+  t.test('broom: a SAGGING belly is pokeable — it sags toward you as it loads', () => {
+    // Regression. Measured against Lane B's live ponding: a real 280 kg pond's centroid rides from
+    // y=1.2 down through y=-0.9 as the belly fills. Gating on `up >= 0` made the broom say "nothing
+    // pooling here" with a quarter-tonne hanging over the garden — a bug no stub would have shown,
+    // because I'd stubbed the pond politely at head height.
+    const mk = (y) => {
+      const p = new PlayerSim({ start: { x: 0, y: 0, z: 0 } });
+      const it = new Interact();
+      const rig = stubRig(280, { x: 0, y, z: 0 });
+      const b = createBroom(null, { heightAt: () => 0 }, it, p, () => rig);
+      p.carrying = 'broom';
+      const r = !!b.targetPond();
+      b.dispose();
+      return r;
+    };
+    assert(mk(2.4), 'overhead: pokeable');
+    assert(mk(1.0), 'a real 188 kg pond rides here: pokeable');
+    assert(mk(0.1), 'sagging to your knees: still pokeable — this is the case that was broken');
+    assert(mk(-0.8), 'a real LIVE 281 kg belly rides here, rig still up: must be pokeable');
+    assert(!mk(-4.5), 'post-tear wreckage lies here: nothing coherent to poke');
+  });
+
+  t.test('broom: survives a rig with no ponding at all (and a pre-rig null centroid)', () => {
     const p = new PlayerSim({ start: { x: 0, y: 0, z: 0 } });
     const it = new Interact();
-    const noPonding = { };                                     // a rig with no ponding at all
+    const noPonding = {};                                      // e.g. an old rig, or none
     const b = createBroom(null, { heightAt: () => 0 }, it, p, () => noPonding);
     p.carrying = 'broom';
-    assertEq(b.ponds().length, 0, 'no ponds reported');
+    assertEq(b.pond(), null, 'no centroid reported');
     fixedLoop(2, DT, (dt, tt) => it.step(dt, tt, p, true));
     assert(!p.events.some((e) => e.type === 'doused'), 'nothing fires, nothing throws');
-    b.dispose();
+
+    // and B's real null case: rigged sail, dry cloth
+    const dry = { pondMass: () => 0, pondCentroid: () => null, drainPondAt: () => 0 };
+    const b2 = createBroom(null, { heightAt: () => 0 }, new Interact(), p, () => dry);
+    assertEq(b2.targetPond(), null, 'a dry sail offers nothing to poke');
+    b2.dispose(); b.dispose();
   });
 
   // ---------------------------------------------------------------- solids collision

web/world/js/tests/e.test.js

@@ -79,6 +79,7 @@ const ASSETS = [
     nodes: ['palings', 'rails', 'debris_palings'] },
   { name: 'broom_01', h: [1.35, 1.50],
     nodes: ['handle', 'head', 'bristles', 'grip_anchor', 'poke_tip'] },
+  { name: 'hail_stone_01', h: [0.012, 0.028], nodes: ['stone'] },
 ];
 
 function sizeOf(gltf) {

web/world/js/tests/weather.selftest.js

@@ -504,6 +504,101 @@ export function weatherCases(storms) {
     assert(!validateStorm(hot, 'x').ok, 'validator accepted rain intensity above 1 — the scale is peakMmPerHour, not the curve');
   });
 
+  // ---- 11. hail (SPRINT5 decision 13) ----
+  // The wind-side of hail: intensity timeline and its ramp across the campaign.
+  // The garden-damage half (steep shadow, ≥2× rig response) needs skyfx +
+  // SailRig, so it lives in c.test.js.
+  test('hail ramps across the campaign: none / mild / a wild-night burst', () => {
+    const peakAndArea = (def) => {
+      const f = createWindField(def);
+      let peak = 0, peakT = 0, area = 0;
+      for (let t = 0; t <= f.duration; t += DT) {
+        const h = f.hailAt(t);
+        if (h > peak) { peak = h; peakT = t; }
+        area += h * DT;
+      }
+      return { peak, peakT, area };
+    };
+    const g = peakAndArea(storms.storm_01_gentle);
+    const m = peakAndArea(storms.storm_03_southerly);
+    const w = peakAndArea(storms.storm_02_wildnight);
+    metrics['storm_01.hailPeak'] = +g.peak.toFixed(2);
+    metrics['storm_03.hailPeak'] = +m.peak.toFixed(2);
+    metrics['storm_02.hailPeak'] = +w.peak.toFixed(2);
+    metrics['storm_02.hailSeconds'] = +w.area.toFixed(1);
+
+    assert(g.peak === 0, `the gentle storm hailed (${g.peak}) — storm_01 must have no hail`);
+    assert(m.peak > 0.2 && m.peak < 0.8, `storm_03 hail peak ${m.peak.toFixed(2)} — wanted a mild middle rung`);
+    assert(w.peak >= 0.95, `storm_02 hail peak only ${w.peak.toFixed(2)} — the wild night needs a proper burst`);
+    assert(w.area > m.area * 3, 'the wild night should carry vastly more hail than the mild storm');
+  });
+
+  test('storm_02 hail lands ON the southerly change', () => {
+    const change = (storms.storm_02_wildnight.events.find((e) => e.type === 'windchange')).t;
+    const f = createWindField(storms.storm_02_wildnight);
+    // find the authored-burst peak (near the change), not just any gust-synced tick
+    let peak = 0, peakT = 0;
+    for (let t = change - 3; t <= change + 8; t += DT) {
+      const h = f.hailAt(t);
+      if (h > peak) { peak = h; peakT = t; }
+    }
+    assert(peak >= 0.95, `hail near the change only reached ${peak.toFixed(2)}`);
+    assert(Math.abs(peakT - change) < 6, `hail peaks at t=${peakT.toFixed(1)}, the change is at t=${change} — they should coincide`);
+  });
+
+  test('hail is silent through a gust telegraph and rides its own gust', () => {
+    // the gust-synced bursts must not fire during the telegraph window, or hail
+    // would arrive before the gust it belongs to — the opposite of the drama
+    const def = storms.storm_02_wildnight;
+    const f = createWindField(def);
+    const thresh = def.hail.withGustsAbove;
+    for (const g of f.gusts) {
+      if (g.pow < thresh) continue;
+      // during the telegraph (first GUST.TELEGRAPH s) the gust-synced part is 0.
+      // an authored burst may still overlap, so only check gusts clear of t=55±8.
+      if (Math.abs(g.t0 - 55) < 10) continue;
+      for (let t = g.t0 + 0.05; t < g.t0 + GUST.TELEGRAPH; t += DT) {
+        assert(f.hailAt(t) < 1e-9, `hail fell during a gust's telegraph at t=${t.toFixed(2)} — it should wait for the gust`);
+      }
+    }
+  });
+
+  test('hail does not re-time the storm (zero draws of its own)', () => {
+    const base = storms.storm_02_wildnight;
+    const a = createWindField(base);
+    for (const gi of [0, 0.3, 0.85, 1]) {
+      const d = JSON.parse(JSON.stringify(base));
+      d.hail.gustBurstIntensity = gi;
+      d.hail.bursts = [];       // even removing the authored burst mustn't move gusts
+      const b = createWindField(d);
+      assert(a.gusts.length === b.gusts.length, `hail change moved the gust count`);
+      a.gusts.forEach((g, i) => {
+        assert(g.t0 === b.gusts[i].t0 && g.pow === b.gusts[i].pow, `hail change re-timed gust ${i}`);
+      });
+      assert(a.speedAt(3, -2, 47.3) === b.speedAt(3, -2, 47.3), 'hail change altered the wind');
+    }
+  });
+
+  test('validator rejects broken hail blocks', () => {
+    const base = () => JSON.parse(JSON.stringify(storms.storm_02_wildnight));
+    const cases = [
+      ['size 0', (d) => { d.hail.size = 0; }],
+      ['size huge', (d) => { d.hail.size = 20; }],
+      ['intensity > 1', (d) => { d.hail.bursts[0].intensity = 1.5; }],
+      ['negative fade', (d) => { d.hail.bursts[0].fade = -1; }],
+      ['burst after the storm', (d) => { d.hail.bursts[0].t = 200; }],
+      ['gustBurstIntensity > 1', (d) => { d.hail.gustBurstIntensity = 2; }],
+      ['neither bursts nor gusts', (d) => { delete d.hail.bursts; delete d.hail.withGustsAbove; }],
+    ];
+    for (const [label, mutate] of cases) {
+      const d = base(); mutate(d);
+      assert(!validateStorm(d, 'broken').ok, `validator accepted broken hail: ${label}`);
+    }
+    // a hail-free storm (no block at all) must still validate
+    const none = base(); delete none.hail;
+    assert(validateStorm(none, 'nohail').ok, 'validator rejected a storm with no hail — hail is optional');
+  });
+
   return { cases, metrics };
 }
 

web/world/js/weather.core.js

@@ -167,6 +167,27 @@ export function buildGustTimeline(def, seed) {
   return out;
 }
 
+// ---------- hail (SPRINT5 decision 13) ----------
+// Hail, not rain, carries the garden score. Rain honestly walks under a sail
+// (droplets terminal ~9 m/s, so a 30 m/s crosswind blows them in at atan(30/9)
+// ≈ 73° off vertical — nearly sideways), which is why a perfect rig scored 54%
+// vs 48% for no rig at all. Hailstones are dense: terminal velocity ~20 m/s for
+// a 1 cm stone, so the SAME 30 m/s gale only leans them atan(30/20)≈56° — and
+// that overstates it, because a dense stone's drag couples weakly to the
+// horizontal air, so observed hail lean tops out ~15-20°. Steep hail is blocked
+// by overhead cloth even in a gale, so the garden score becomes rig-responsive
+// without faking the rain physics. The steepness lives in skyfx.hailVelocity();
+// the intensity timeline lives here.
+
+/** Envelope of one authored hail burst at local time `dt` (s since it began). */
+export function hailBurstEnvelope(dt, ramp, hold, fade, peak) {
+  if (dt <= 0) return 0;
+  if (dt < ramp) return peak * (dt / ramp);
+  if (dt < ramp + hold) return peak;
+  if (dt < ramp + hold + fade) return peak * (1 - (dt - ramp - hold) / fade);
+  return 0;
+}
+
 // ---------- the field ----------
 /**
  * @param {object} def   parsed storm JSON (see data/storms/*.json)
@@ -189,6 +210,19 @@ export function createWindField(def, opts = {}) {
   const gd = def.gusts || {};
   const downFrac = gd.downdraftOfTotal ?? gd.downdraft ?? DEFAULT_DOWNDRAFT;
 
+  // Hail bursts: authored ones from the JSON, plus one synced to every gust at
+  // or above `withGustsAbove` power — so the biggest gusts arrive WITH hail, the
+  // storm's worst moment landing all at once. Gust-synced bursts key off the
+  // deterministic gust timeline and draw NO randomness, so tuning hail can't
+  // re-time the storm (same guarantee as the downdraft).
+  const hailDef = def.hail || null;
+  const hailBursts = (hailDef && Array.isArray(hailDef.bursts))
+    ? hailDef.bursts.map((b) => ({
+        t: b.t, ramp: b.ramp ?? 0.8, hold: b.hold ?? 3, fade: b.fade ?? 1.5,
+        intensity: b.intensity ?? 1,
+      }))
+    : [];
+
   let shelters = [];
 
   /** Spatially-uniform part: base curve + every gust envelope live at t. */
@@ -398,6 +432,42 @@ export function createWindField(def, opts = {}) {
       return Math.min(1, Math.max(0, r.intensity ?? 0));
     },
 
+    /**
+     * 0..1 hail intensity at time t (SPRINT5 decision 13). Max over every live
+     * burst — authored plus gust-synced — because "how hard is it hailing right
+     * now" is a level, not a sum; two overlapping bursts don't hail at 1.6×.
+     * Zero for a storm with no `hail` block, so storm_01 simply never hails.
+     */
+    hailAt(t) {
+      if (!hailDef) return 0;
+      let h = 0;
+      for (let i = 0; i < hailBursts.length; i++) {
+        const b = hailBursts[i];
+        if (t <= b.t || t >= b.t + b.ramp + b.hold + b.fade) continue;
+        const v = hailBurstEnvelope(t - b.t, b.ramp, b.hold, b.fade, b.intensity);
+        if (v > h) h = v;
+      }
+      const thresh = hailDef.withGustsAbove;
+      if (thresh != null) {
+        const gi = hailDef.gustBurstIntensity ?? 0.8;
+        for (let i = 0; i < gusts.length; i++) {
+          const g = gusts[i];
+          if (g.pow < thresh) continue;
+          if (t <= g.t0 || t >= g.endAt) continue;
+          // reuse the gust envelope: silent through the telegraph, then it hits
+          // as the gust ramps and holds — the hail lands WITH the gust.
+          // gustEnvelope(gt, pow) returns pow×fraction, so passing gi as "pow"
+          // gives the intensity-scaled 0..gi envelope directly.
+          const v = gustEnvelope(t - g.t0, gi);
+          if (v > h) h = v;
+        }
+      }
+      return h > 1 ? 1 : h;
+    },
+
+    /** Stone-size scalar (audio pitch, visual scale, damage weight). Default 1. */
+    get hailSize() { return hailDef ? (hailDef.size ?? 1) : 0; },
+
     /**
      * Rain rate in REAL-WORLD mm/hr. Same curve as rainAt(), with physical units
      * on it — `rainAt` stays 0..1 because it drives drop count and opacity, and a
@@ -520,5 +590,34 @@ export function validateStorm(def, name = 'storm') {
     }
   }
 
+  // ---- hail (SPRINT5 decision 13) ----
+  if (def.hail) {
+    const hd = def.hail;
+    if (hd.size != null && (!Number.isFinite(hd.size) || hd.size <= 0 || hd.size > 5)) {
+      bad(`hail.size must be a positive scalar up to ~5 (stones bigger than golf balls break the metaphor) — got ${hd.size}`);
+    }
+    if (hd.withGustsAbove != null && !Number.isFinite(hd.withGustsAbove)) {
+      bad('hail.withGustsAbove must be a finite gust-power threshold in m/s');
+    }
+    if (hd.gustBurstIntensity != null && (!(hd.gustBurstIntensity >= 0) || hd.gustBurstIntensity > 1)) {
+      bad(`hail.gustBurstIntensity must be 0..1 — got ${hd.gustBurstIntensity}`);
+    }
+    // A storm with a hail block but nothing to fire it never hails — that's a
+    // typo, not a design, so say so rather than shipping silent hail.
+    if (!Array.isArray(hd.bursts) && hd.withGustsAbove == null) {
+      bad('hail block has neither bursts[] nor withGustsAbove — it would never hail');
+    }
+    for (const b of hd.bursts || []) {
+      if (!Number.isFinite(b.t)) bad(`hail burst ${JSON.stringify(b)} has no finite t`);
+      if (b.t + 0 > (def.duration ?? 90)) bad(`hail burst at t=${b.t} starts after the storm ends`);
+      for (const k of ['ramp', 'hold', 'fade']) {
+        if (b[k] != null && !(b[k] >= 0)) bad(`hail burst at t=${b.t} has a negative ${k}`);
+      }
+      if (b.intensity != null && (!(b.intensity >= 0) || b.intensity > 1)) {
+        bad(`hail burst at t=${b.t} intensity must be 0..1 — got ${b.intensity}`);
+      }
+    }
+  }
+
   return { ok: errors.length === 0, errors };
 }

web/world/js/weather.js

@@ -87,6 +87,12 @@ export function createWind(def, opts = {}) {
     /** 0..1 rain intensity — drives drop count and opacity. */
     rainAt(t) { return field.rainAt(t); },
 
+    /** 0..1 hail intensity (SPRINT5 decision 13). Zero for a hail-free storm. */
+    hailAt(t) { return field.hailAt(t); },
+
+    /** Stone-size scalar — audio pitch, visual scale, damage weight. */
+    get hailSize() { return field.hailSize; },
+
     /** Rain rate in real-world mm/hr. Ponding (decision 10) reads this. */
     rainMmPerHour(t) { return field.rainMmPerHour(t); },