fix severe lag caused by bad Discord css

src/plugins/_core/fixDiscordCss.ts

@@ -0,0 +1,59 @@
+/*
+ * Vencord, a Discord client mod
+ * Copyright (c) 2026 Vendicated and contributors
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+import { Devs } from "@utils/constants";
+import { Logger } from "@utils/Logger";
+import definePlugin, { StartAt } from "@utils/types";
+
+let observer: MutationObserver;
+
+function cleanSheet(sheet: CSSStyleSheet) {
+    try {
+        const rules = sheet.cssRules;
+        if (!rules) return;
+
+        for (let i = 0; i < rules.length; i++) {
+            const rule = rules[i];
+
+            if ((rule as CSSStyleRule).selectorText?.includes(":has(.gameOption_")) {
+                new Logger("FixDiscordCss").info("Removed problematic CSS rule", rule.cssText);
+                sheet.deleteRule(i);
+                observer.disconnect();
+                break;
+            }
+        }
+    } catch (e) { }
+}
+
+function handleNode(node: Node) {
+    if (node.nodeType !== Node.ELEMENT_NODE || !(node as HTMLElement).matches('link[rel="stylesheet"]')) return;
+
+    const linkNode = node as HTMLLinkElement;
+
+    if (linkNode.sheet) {
+        cleanSheet(linkNode.sheet);
+    } else {
+        node.addEventListener("load", () => cleanSheet(linkNode.sheet!), { once: true });
+    }
+}
+
+export default definePlugin({
+    name: "FixDiscordCss",
+    description: "Fixes Discord's css lag",
+    authors: [Devs.Ven],
+    required: true,
+
+    startAt: StartAt.DOMContentLoaded,
+
+    start() {
+        observer = new MutationObserver(mutations => {
+            for (const m of mutations) {
+                m.addedNodes.forEach(handleNode);
+            }
+        });
+        observer.observe(document.head, { childList: true });
+    }
+});