diff --git a/internal/web/static/app.css b/internal/web/static/app.css
index bdba0f8..f5543da 100644
--- a/internal/web/static/app.css
+++ b/internal/web/static/app.css
@@ -603,6 +603,10 @@ a.admin-link:hover { color: var(--fg); text-decoration: underline; }
   .editor-wrap { min-height: 45vh; }
   .editor { font-size: 15px; }
   .gutter { font-size: 15px; }
+  /* #167: the paste-view gutter must track .code's font size, not the editor
+     gutter's — mismatched font sizes make gutline rows taller/shorter than
+     code rows and every number drifts off its line start */
+  .code .gutter { font-size: var(--code-fs); }
   .editor-head { flex-wrap: wrap; }
   .editor-head-title { flex: 1 1 100%; }
   .editor-head input { min-width: 0; font-size: 16px; }
diff --git a/internal/web/static/paste-lines.js b/internal/web/static/paste-lines.js
index a71d8ba..4d9e7d6 100644
--- a/internal/web/static/paste-lines.js
+++ b/internal/web/static/paste-lines.js
@@ -54,7 +54,16 @@
     // is closest to its line's top.
     var bodyTop = body.getBoundingClientRect().top;
     var lh = parseFloat(getComputedStyle(body).lineHeight) || 1;
-    var totalRows = Math.max(lines.length, Math.ceil(body.getBoundingClientRect().height / lh));
+    var maxBottom = 0;
+    for (var j = 0; j < lines.length; j++) {
+      var btm = lines[j].getBoundingClientRect().bottom - bodyTop;
+      if (btm > maxBottom) maxBottom = btm;
+    }
+    // Rows needed through the last visual row of the deepest line (ceil, so a
+    // partially-filled last row still gets its gutter span).
+    // Rows needed: floor(last line bottom / lh) + 1 — the row a line STARTS on
+    // must exist even when its bottom lands exactly on the body's edge.
+    var totalRows = Math.max(lines.length, Math.floor(maxBottom / lh) + 1);
     gutter.textContent = '';
     var frag = document.createDocumentFragment();
     var spans = [];
@@ -97,7 +106,7 @@
   // size change (paste of lots of text, window resize, zoom). Only width
   // changes of the code column affect wrapping, so observe width only —
   // height changes caused by our own renumbering must not re-trigger.
-  var mo = new MutationObserver(renumber);
+  var mo = new MutationObserver(function () { setTimeout(renumber, 0); });
   mo.observe(document.documentElement, { attributes: true, attributeFilter: ['data-wrap'] });
   var lastW = body.getBoundingClientRect().width;
   if (window.ResizeObserver) {