diff --git a/web/src/reader/reader.ts b/web/src/reader/reader.ts
index 49bdd18b..a64e2e1d 100644
--- a/web/src/reader/reader.ts
+++ b/web/src/reader/reader.ts
@@ -1896,7 +1896,12 @@ document.addEventListener("alpine:init", () => {
         }
         if (best === null) return;
         if (isStart) {
-          r[0] = Math.min(Math.max(best, 0), r[0] + r[2] - MIN);
+          // A start-edge drag pins the FAR edge: shrink the size by the
+          // same amount the left moves (keeping the size would drag the
+          // rect's right edge along — found by device test).
+          const far = r[0] + r[2];
+          r[0] = Math.min(Math.max(best, 0), far - MIN);
+          r[2] = far - r[0];
         } else {
           r[2] = Math.min(Math.max(best - r[0], MIN), 1 - r[0]);
         }
@@ -1913,7 +1918,10 @@ document.addEventListener("alpine:init", () => {
           }
         }
         if (grab.edge === "top") {
-          r[1] = Math.min(Math.max(best, 0), r[1] + r[3] - MIN);
+          // Mirror of the left edge: a top-edge drag pins the bottom.
+          const bottom = r[1] + r[3];
+          r[1] = Math.min(Math.max(best, 0), bottom - MIN);
+          r[3] = bottom - r[1];
         } else {
           r[3] = Math.min(Math.max(best - r[1], MIN), 1 - r[1]);
         }