diff --git a/tools/site_audit/gardenfly.js b/tools/site_audit/gardenfly.js
index a73193d..33ccbd8 100644
--- a/tools/site_audit/gardenfly.js
+++ b/tools/site_audit/gardenfly.js
@@ -89,14 +89,14 @@ export function hardwareByName(name) {
  * @param {Array}  [o.ids]     4 anchor ids; null/omitted = bare bed (the control)
  * @param {Array|object} [o.hw] hardware per pick (aligned with ids), or one tier for all 4
  * @param {number} [o.tension]
- * @param {number} [o.porosity] fabric flown. DEFAULT 0.30 (shade cloth — the
- *                             fabric a competent player flies, same as sweep.js,
- *                             and every pinned number to date was measured on
- *                             it); pass 0 for membrane. SPRINT16: the F key is
- *                             live and storm_06's whole bet is membrane-vs-
- *                             cloth, so the audit engine must be able to fly
- *                             both — C's gate-3.1 pin and B's membrane-balance
- *                             tables ride this parameter.
+ * @param {number} [o.porosity] fabric: 0.30 = shade cloth (the default every
+ *                            audit number to date was flown on — unchanged),
+ *                            0 = membrane. SPRINT16 gate 3.1 measures the
+ *                            fabric bet through THIS chain, same driver as
+ *                            every other garden number, so cloth-vs-membrane
+ *                            differ by exactly one variable. [Lane C addition,
+ *                            THREADS 2026-07-20 — B: contest at integration if
+ *                            you want a different door.]
  * @returns {{ hp, state, byHail, byRain, cornersLost, peaks, marginal, cost }}
  */
 export function flyGarden({ anchors, bed, stormDef, siteDef = null, use = null, ids = null, hw = null, tension = 1.0, porosity = 0.30 }) {
@@ -107,6 +107,8 @@ export function flyGarden({ anchors, bed, stormDef, siteDef = null, use = null,
   if (ids) {
     const hwArr = Array.isArray(hw) ? hw : Array(4).fill(hw ?? hardwareByName('rated shackle'));
     cost = hwArr.reduce((s, h) => s + (h.cost || 0), 0);
+    // shade cloth (porosity 0.30) unless the caller is measuring the fabric
+    // bet — same default as sweep.js, so nothing pre-SPRINT16 moves.
     rig = new SailRig({ anchors, gridN: 10, porosity }).attach(ids, hwArr, tension);
     // D's skipped-attach trap: a rig without its shadow mesh scores as a bare
     // bed and the number LOOKS plausible. Refuse to fly it.