diff --git a/frontend/src/index.css b/frontend/src/index.css
index 4f69c0c5..21d79e7f 100644
--- a/frontend/src/index.css
+++ b/frontend/src/index.css
@@ -288,7 +288,11 @@ html[data-theme="light"] {
 }
 
 html {
-  font-size: calc(16px * var(--font-scale));
+  /* Snap the scaled root font-size to a whole pixel. The base is rem-derived app-wide, so a fractional
+     root (e.g. 16px * 1.02 = 16.32px) makes every box height fractional — and when a reflow changes a
+     section's row count, the sub-pixel remainder shifts everything below it by ~0.5px, a visible 1px
+     jitter at DPR=1. round() keeps the font-scale feature but quantises to crisp integer metrics. */
+  font-size: round(calc(16px * var(--font-scale)), 1px);
   background: var(--bg);
 }