Skip unresolved container query CSS

Exclude linked container-query groups when their current applicability cannot be resolved, with a browser regression proving inactive styles do not leak.

AI assistance disclosure: This commit was prepared with Codex under maintainer direction.

cli/engine/browser/injected/index.mjs

@@ -1321,6 +1321,13 @@ if (IS_BROWSER) {
       try { return CSS.supports(condition); }
       catch { return true; }
     }
+    if (constructorName === 'CSSContainerRule' || /^\s*@container\b/i.test(rule?.cssText || '')) {
+      // The platform exposes no matchMedia-equivalent for container queries,
+      // and selector matches do not prove that the element's query container
+      // satisfies the condition. Omit the group rather than report styles that
+      // are inactive for the current layout.
+      return false;
+    }
     return true;
   }
 

cli/engine/detect-antipatterns-browser.js

@@ -8225,6 +8225,13 @@ if (IS_BROWSER) {
       try { return CSS.supports(condition); }
       catch { return true; }
     }
+    if (constructorName === 'CSSContainerRule' || /^\s*@container\b/i.test(rule?.cssText || '')) {
+      // The platform exposes no matchMedia-equivalent for container queries,
+      // and selector matches do not prove that the element's query container
+      // satisfies the condition. Omit the group rather than report styles that
+      // are inactive for the current layout.
+      return false;
+    }
     return true;
   }
 

tests/detect-antipatterns-browser.test.mjs

@@ -1405,6 +1405,11 @@ describe('detectUrl — browser-only fixtures', () => {
       })));
       const linkedFindings = await linkedPage.evaluate(() => window.impeccableDetect({ serialize: true })
         .flatMap(group => group.findings || []));
+      const inactiveContainerBackground = await linkedPage.$eval(
+        '.inactive-container-stripes',
+        element => getComputedStyle(element).backgroundImage,
+      );
+      assert.equal(inactiveContainerBackground, 'none');
       const grids = linkedFindings.filter(finding => finding.type === 'codex-grid-background');
       assert.equal(grids.length, 1, JSON.stringify({ linkedFindings, linkedCssom }));
       assert.equal(grids[0].severity, 'advisory');

tests/fixtures/antipatterns/linked-url-patterns.css

@@ -40,6 +40,17 @@ main > ::before {
   }
 }
 
+.container-query-host {
+  container-type: inline-size;
+  width: 240px;
+}
+
+@container (width > 900px) {
+  .inactive-container-stripes {
+    background: repeating-linear-gradient(45deg, #eee, #eee 10px, #fafafa 10px, #fafafa 20px);
+  }
+}
+
 .unused-linked-transition {
   transition: width 200ms ease;
 }

tests/fixtures/antipatterns/linked-url-patterns.html

@@ -11,6 +11,9 @@
     <div class="flag-linked-grid">Rendered decorative grid</div>
     <div class="inactive-media-stripes">Inactive media stripes</div>
     <div class="inactive-supports-stripes">Inactive supports stripes</div>
+    <div class="container-query-host">
+      <div class="inactive-container-stripes">Inactive container-query stripes</div>
+    </div>
   </main>
 </body>
 </html>