diff --git a/public/css/aurora.css b/public/css/aurora.css
index 647b86ee..c9147394 100644
--- a/public/css/aurora.css
+++ b/public/css/aurora.css
@@ -579,8 +579,10 @@ input[type=date]:focus, select:focus {
 .gw-relnotes{font-size:12px;color:var(--muted);text-decoration:underline;text-underline-offset:2px;opacity:.8}
 .gw-relnotes:hover{opacity:1;color:var(--text)}
 
-/* Issue 11: Gateway detail — 3-column (1/3 each) sub-card grid */
-.gw-detail-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:14px}
+/* Issue 11: Gateway detail — exactly 3 columns (1/3 each), max 3 side by side; collapse on narrow */
+.gw-detail-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:14px}
+@media(max-width:1100px){.gw-detail-grid{grid-template-columns:repeat(2,minmax(0,1fr))}}
+@media(max-width:760px){.gw-detail-grid{grid-template-columns:1fr}}
 .gw-detail-grid .gw.full{grid-column:1/-1}
 /* Fix 3: "Discovered devices" + "Scan targets" at 1/2 width each in their own row */
 .gw-half-row{display:grid;grid-template-columns:1fr 1fr;gap:14px;grid-column:1/-1}
diff --git a/tests/aurora_theme.test.js b/tests/aurora_theme.test.js
index 3ec87543..f27a516e 100644
--- a/tests/aurora_theme.test.js
+++ b/tests/aurora_theme.test.js
@@ -1456,11 +1456,11 @@ describe('aurora theme — gateways UX fixes (Issues 8/9/10/11)', () => {
     assert.match(js, /grid2\.appendChild\(auroraVersionsCard\(g\)\)/, 'auroraRenderDetail() calls auroraVersionsCard(g)');
   });
 
-  it('Issue 11: auroraRenderDetail uses gw-detail-grid and aurora.css has responsive column rule', () => {
+  it('Issue 11: auroraRenderDetail uses gw-detail-grid with exactly 3 columns (1/3 each)', () => {
     const js = fs.readFileSync(path.join(__dirname, '..', 'public', 'js', 'gateways.js'), 'utf8');
     const css = fs.readFileSync(path.join(__dirname, '..', 'public', 'css', 'aurora.css'), 'utf8');
     assert.match(js, /el\('div',\s*'gw-detail-grid'\)/, 'auroraRenderDetail() uses gw-detail-grid class');
-    assert.match(css, /\.gw-detail-grid\s*\{[^}]*repeat\(auto-fit,minmax\(280px,1fr\)\)/, 'gw-detail-grid uses responsive auto-fit column layout');
+    assert.match(css, /\.gw-detail-grid\s*\{[^}]*repeat\(3,minmax\(0,1fr\)\)/, 'gw-detail-grid uses exactly 3 columns (1/3 each)');
   });
 });