diff --git a/app/src/components/ui/ui-layout.cy.js b/app/src/components/ui/ui-layout.cy.js
index e1496b80..e391befc 100644
--- a/app/src/components/ui/ui-layout.cy.js
+++ b/app/src/components/ui/ui-layout.cy.js
@@ -955,6 +955,45 @@ describe('a progress bar has room for the label inside it', () => {
         });
     });
 
+    themeNames.forEach((theme) => {
+        it(`draws no outline of its own in ${theme}, and is the size it was with one`, () => {
+            /*
+             * The border came off.  Both halves matter: the bar must not be the 1px smaller
+             * inside that removing an outline usually makes it -- it is not, because
+             * `box-sizing: border-box` is global and the declared height was always the outer
+             * box -- and the empty part of the track has to keep an edge of its own now that
+             * no line is drawing one, which is why the track paints `--head` rather than the
+             * `--bg` / `--panel` pair that a bar sits on.
+             *
+             * Measured against `rem`, not px: 1.375rem and 7.5rem move with `--ui-scale`.
+             */
+            cy.mountUI(bar({percent: 40, label: 'CPU Usage'}), {theme});
+
+            cy.get('.wrolpi-progress').should(($bar) => {
+                const style = getComputedStyle($bar[0]);
+                ['Top', 'Right', 'Bottom', 'Left'].forEach(side =>
+                    expect(style[`border${side}Width`], `no border on the ${side} edge`)
+                        .to.equal('0px'));
+
+                const rem = 16 * uiScale();
+                expect($bar[0].getBoundingClientRect().height, 'the bar is the height it was')
+                    .to.be.closeTo(1.375 * rem, 0.5);
+                expect(parseFloat(style.minWidth), 'and the width it was')
+                    .to.be.closeTo(7.5 * rem, 0.5);
+            });
+
+            // The Panel the bar sits on, which is what the track has to stay off.
+            cy.get('.wrolpi-progress').should(($bar) => {
+                const track = getComputedStyle($bar[0]).backgroundColor;
+                const panel = getComputedStyle($bar[0].closest('.wrolpi-panel')).backgroundColor;
+                expect(track, 'the track paints a surface of its own')
+                    .to.not.match(/^rgba\(.*,\s*0(\.0+)?\)$/);
+                expect(contrast(toRgb(track), toRgb(panel)), 'track against the panel under it')
+                    .to.be.greaterThan(1.05);
+            });
+        });
+    });
+
     it('keeps a long label on one line', () => {
         /*
          * `white-space: nowrap` on the label.  The first version of this asserted the bar did
diff --git a/app/src/components/ui/ui.css b/app/src/components/ui/ui.css
index 0ab395bc..a3289aa2 100644
--- a/app/src/components/ui/ui.css
+++ b/app/src/components/ui/ui.css
@@ -1160,14 +1160,19 @@ html .mantine-Notification-closeButton:hover {
  * `overflow: hidden` is what keeps the indeterminate band inside the bar.  Without it the
  * band slides from `margin-left: -35%` to `100%` in full view, so the animation ran from
  * outside the left edge to outside the right one, painting over whatever sat beside it.
+ *
+ * No border: the track is drawn by its own fill instead, so `--head` rather than `--bg`.
+ * A bar sits on a Panel as often as on the page, and `--bg` is invisible against one of
+ * those two by definition -- `--head` is off both in every theme.  Height and min-width
+ * are the outer box (`box-sizing: border-box` is global), so dropping the 1px border left
+ * the bar exactly the size it was.
  */
 .wrolpi-progress {
     position: relative;
     height: 1.375rem;
     min-width: 7.5rem;
     overflow: hidden;
-    background: var(--bg);
-    border: 1px solid var(--border);
+    background: var(--head);
 }
 
 /*
@@ -1260,10 +1265,6 @@ html .mantine-Notification-closeButton:hover {
  * is lighter than black by definition.  Left as it is, deliberately, rather than
  * asserted at a threshold chosen to pass.
  */
-html[data-theme="light"] .wrolpi-progress {
-    background: var(--panel);
-}
-
 html[data-theme="light"] .wrolpi-progress-fill {
     filter: brightness(1.75) saturate(0.55);
 }