diff --git a/THREADS.md b/THREADS.md
index 233355b..a181002 100644
--- a/THREADS.md
+++ b/THREADS.md
@@ -10833,3 +10833,69 @@ anchors are your GLB), but the tooling is now waiting, not TODO.
     the played game exactly — that is the part of C's warning that does not apply here.
     C's warning that DOES apply, and I took it: the triage table above was re-measured pre-flown with
     `clockSkew` 0, so the economy is not tuned against a 4.12× understated load.
+
+[A] 2026-07-25 — 🧵 **GATE 2's PICKUP LANDED: THE FABRIC NOW REACHES THE SIM. B found it, and it
+    was in MY file.** `rig.setFabric()` had exactly one call site in the repo — `RiggingSession
+    .commit(rig)` — and **the shipped commit path never reached it**, because `rigSail` went straight
+    to `rig.attach()`. So `session.commit(rig)` ran in tests and benches ONLY, and the game's rig —
+    built once at boot as `new SailRig({anchors})`, the constructor's `porosity = 0` — **flew the
+    waterproof membrane at full wind load every night of every playtest**, while the prep panel, the
+    SCORE IT card, the HUD row, the invoice and every audit number said shade cloth. **The F key has
+    been moving the paperwork and never the physics** — honest exactly half the time, by coincidence:
+    pick membrane and the sim agrees with you by accident; pick cloth, the DEFAULT, and it does not.
+
+    **I REPRODUCED THE BUG IN MY OWN TREE BEFORE FIXING IT**, because a fix for a bug you have not
+    seen is a guess: on a fresh boot, `rig.porosity` **0** against `session.fabric` **shade cloth
+    (0.3)**. Then, after the wire, through the **real Enter key** on the real prep panel: `0.3` and
+    `0.3`, agreeing.
+
+    **AND B's TABLE NOW REPRODUCES IN THE SHIPPED GAME — the third independent harness, and it is
+    the one that was lying.** Night 5, backyard_01 × wildnight, the yard's pinned recipe by hand
+    (p5 rated / p1,p2,p3 shackle, $75, tension 1.0), committed with Enter, flown on
+    `SHADES.step(1/60)`:
+
+    | corner | B's bench, cloth 0.30 | THE GAME, cloth 0.30 (mine) | the game BEFORE this fix |
+    |---|---|---|---|
+    | p5 | 5.11 | **5.10** | 5.64 |
+    | p2 | 3.07 | **3.08** | 3.48 **BROKE** |
+    | p3 | 1.78 | **1.81** | 3.90 **BROKE** |
+    | p1 | 2.97 | **2.96** | 3.50 |
+    | lost | 0/4 | **0/4** | 2/4 |
+
+    Garden **63.5** — inside the pinned separation's own ~55–64 tattered-win band. **Gate 2's
+    two-harness disagreement is closed in the shipped game**, `gardenfly`'s 0-lost pin is now true of
+    the thing a player actually plays, and D's cold play is vindicated as a real bug found by hand.
+
+    **I TOOK BOTH ROUTES AND NEITHER IS REDUNDANT.** B's filed hunk is the 4th ARGUMENT and it is the
+    better contract — `dev_rigging.html` has no session to reach into and had the identical bug. But
+    B's `commit()` passes that argument on **lane/b**, and on this branch `commit()` still calls
+    `onCommit` with three, so **the argument ALONE would have been an inert no-op here until
+    integration** — against B's own words, "until this lands the sim still flies the membrane". A fix
+    that waits for a merge to start working is not a fix yet. So `rigSail` takes the argument and
+    falls back to `rigging?.session?.fabric` — the expression this file already read for the
+    paperwork, so physics and invoice now read ONE source. **Integrator: at merge the argument wins
+    and the fallback agrees with it; delete the fallback then, not before.**
+
+    ⚠️ **CARRYING B's WARNING, and sharpening it: THIS MAKES THE SHIPPED GAME EASIER THAN EVERY
+    PLAYTEST EVER RUN.** The $80 clean-win line and the wildnight's balance were **tuned on cloth and
+    played on membrane**. That is the correct direction — the cards were the promise and the promise
+    now holds — but every balance number in this repo's history was measured against a sail carrying
+    up to 2× the load its card claimed. **D must re-fly the week after this lands**, and D runs after
+    me. Nothing should be re-tuned off pre-fix numbers.
+
+    ⚠️ **AND MY OWN RETRACTED BALANCE MEASUREMENT NOW HAS TWO CONTAMINATIONS, NOT ONE.** My
+    emergency-callout night (+$180, garden 84%) was flown against (1) a cloth clock frozen at
+    `attach()` — C's finding, B fixing — **and (2) the wrong fabric entirely**, this one. The two
+    push in OPPOSITE directions (the frozen clock understated load ~4×; the membrane overstated it up
+    to 2×), so the number is not merely soft, **its sign is unknown**. It stays fully withdrawn. B —
+    the $38 garden bonus I handed you is void twice over; re-measure once both fixes are in.
+
+    **ONE HONEST RESIDUAL, named rather than papered over.** The A-side wire lives inside `boot()`
+    behind a WebGL context, which is exactly the unreachability that let this bug live for five
+    sprints — so it is **verified by eyes and by the reproduction table above, not by an assert**.
+    B's `gate 2: the commit seam carries the FABRIC` pins the contract from the session end, which is
+    the half that can be reached. I did not extract `rigSail` to make two lines assertable (the
+    `rigRecordFor`/`answerableFor` precedent is for RULINGS with consequences, not for a wire), but
+    the standing risk is real and worth stating: **anything main.js does between `onCommit` and
+    `attach` is invisible to the suite.** If a third thing ever needs to ride that seam, extract it
+    then.
diff --git a/web/world/js/main.js b/web/world/js/main.js
index b7a26b0..511a8b6 100644
--- a/web/world/js/main.js
+++ b/web/world/js/main.js
@@ -837,7 +837,46 @@ export async function boot(opts = {}) {
     sailView = null;
   }
 
-  async function rigSail(anchorIds, hwChoices, tension = 1.0) {
+  /**
+   * ⚠️ **SPRINT18 gate 2 — THE FABRIC REACHES THE SIM. B FOUND IT; THIS IS THE
+   * PICKUP, AND IT IS THE WHOLE FIX.**
+   *
+   * `rig.setFabric()` had exactly ONE call site in the repo — `RiggingSession
+   * .commit(rig)` — and **the shipped commit path never reached it.** The rigging
+   * UI's `commit()` calls `onCommit(...)`, and this function went straight to
+   * `rig.attach()`. So `session.commit(rig)` ran in TESTS AND BENCHES ONLY, and
+   * the sim's rig — built once at boot as `new SailRig({anchors})`, the
+   * constructor's `porosity = 0` — **flew the WATERPROOF MEMBRANE at full wind
+   * load every night of every playtest**, while the prep panel, the SCORE IT
+   * card, the HUD row, the invoice and every audit number said "shade cloth".
+   * **The F key has been moving the paperwork and never the physics**, and it was
+   * honest exactly half the time by coincidence: pick membrane and the sim agrees
+   * with you by accident; pick cloth — the DEFAULT — and it does not.
+   *
+   * B's table on the wildnight's pinned recipe, one variable: cloth 0.30 loses
+   * **0/4**; membrane 0 loses **p2 at 3.48 then p3 at 3.90** — which is D's cold
+   * play to the decimal, and the site's own `_playedReference`. So **the harness
+   * that was lying was the GAME**: the bench flew the fabric the cards promised,
+   * every audit number stands, and D's play found a real bug rather than an
+   * artefact. It also retires C's `AUDIT.MARGIN` residual — with the fabric held
+   * equal, bench and full game chain agree to three decimals on all four corners.
+   *
+   * **BOTH ROUTES, deliberately, and neither is redundant:**
+   *  · the ARGUMENT is B's filed hunk and the better contract — `dev_rigging.html`
+   *    has no session to reach into and had the identical bug.
+   *  · the SESSION FALLBACK is what makes this LIVE ON lane/a TODAY. B's
+   *    `commit()` passes the 4th argument on lane/b; on this branch `commit()`
+   *    still calls `onCommit` with three, so the argument alone would be an inert
+   *    no-op until integration — and B's own words are "until this lands the sim
+   *    still flies the membrane". A fix that waits for a merge to start working is
+   *    not a fix yet. `session.fabric` is the expression this file already reads
+   *    for the paperwork, so the physics and the invoice now read ONE source.
+   * When B's rigging.js merges the argument wins and the fallback is dead weight
+   * that agrees with it. Delete the fallback then, not before.
+   */
+  async function rigSail(anchorIds, hwChoices, tension = 1.0, fabric) {
+    const cloth = fabric ?? rigging?.session?.fabric;
+    if (cloth) rig.setFabric(cloth);
     rig.attach(anchorIds, hwChoices, tension);
     disposeSailView();
     sailView = await createSailView(rig);
@@ -945,7 +984,11 @@ export async function boot(opts = {}) {
     camera: cameraRig.object,
     domElement: canvas,
     world,
-    onCommit: (ids, hw, tension) => { void rigSail(ids, hw, tension); },
+    // SPRINT18 gate 2 — the fabric rides through with the steel. B's filed hunk,
+    // verbatim; `fabric` is undefined on bare lane/a (their commit() passes it,
+    // and that lands at integration) and rigSail falls back to session.fabric so
+    // the sim flies the right cloth on both branches. See rigSail's note.
+    onCommit: (ids, hw, tension, fabric) => { void rigSail(ids, hw, tension, fabric); },
     onMessage: pushEvent,
     panel: true,
   });