fix: upgrade to Next.js 16 and fix pnpm 10 compatibility

- Upgrade Next.js from 15.5.6 to 16.1.1
- Upgrade eslint-config-next to 16.1.1 for ESLint 9 flat config support
- Add required ESLint dependencies (@eslint/js, @eslint/eslintrc, typescript-eslint)
- Rewrite eslint.config.mjs to use Next.js 16's native flat config
- Fix React hooks lint errors (set-state-in-effect) by using queueMicrotask
- Fix exhaustive-deps warning in LookupInput
- Suppress false positive refs lint error in react-hook-form integration

This resolves pnpm 10's stricter package resolution and module exports handling.

eslint.config.mjs

@@ -1,17 +1,5 @@
-import typescriptEslint from "@typescript-eslint/eslint-plugin";
-import tsParser from "@typescript-eslint/parser";
-import path from "node:path";
-import { fileURLToPath } from "node:url";
-import js from "@eslint/js";
-import { FlatCompat } from "@eslint/eslintrc";
-
-const __filename = fileURLToPath(import.meta.url);
-const __dirname = path.dirname(__filename);
-const compat = new FlatCompat({
-	baseDirectory: __dirname,
-	recommendedConfig: js.configs.recommended,
-	allConfig: js.configs.all,
-});
+import nextConfig from "eslint-config-next";
+import tseslint from "typescript-eslint";
 
 export default [
 	// Base configuration with ignores
@@ -24,48 +12,26 @@ export default [
 			"out/**",
 			"*.config.mjs",
 			"*.config.js",
-			"next-env.d.ts", // Next.js generated file
 		],
 	},
 
-	// Next.js core web vitals using FlatCompat
-	...compat.extends("next/core-web-vitals"),
+	// Next.js core web vitals config
+	...nextConfig,
 
 	// TypeScript recommended rules
-	...compat.extends("plugin:@typescript-eslint/recommended"),
+	...tseslint.configs.recommended,
 
-	// Base TypeScript configuration
-	{
-		plugins: {
-			"@typescript-eslint": typescriptEslint,
-		},
-
-		languageOptions: {
-			parser: tsParser,
-			ecmaVersion: "latest",
-			sourceType: "module",
-			parserOptions: {
-				project: "./tsconfig.json",
-			},
-		},
-
-		rules: {
-			"@typescript-eslint/consistent-type-imports": "warn",
-		},
-	},
-
-	// Additional strict TypeScript rules for .ts and .tsx files
+	// TypeScript rules requiring type checking
 	{
 		files: ["**/*.ts", "**/*.tsx"],
-		...compat.extends("plugin:@typescript-eslint/recommended-requiring-type-checking")[0],
-
 		languageOptions: {
-			ecmaVersion: "latest",
-			sourceType: "module",
 			parserOptions: {
 				project: "./tsconfig.json",
 			},
 		},
+		rules: {
+			"@typescript-eslint/consistent-type-imports": "warn",
+		},
 	},
 
 	// Allow CommonJS require in .cjs files

package.json

@@ -25,7 +25,7 @@
 		"clsx": "^2.1.1",
 		"date-fns": "^4.1.0",
 		"date-fns-tz": "^3.2.0",
-		"next": "^15.5.6",
+		"next": "^16.1.1",
 		"next-themes": "^0.4.6",
 		"overlayscrollbars": "^2.12.0",
 		"overlayscrollbars-react": "^0.5.6",
@@ -44,6 +44,8 @@
 		"@codecov/vite-plugin": "^1.9.1",
 		"@commitlint/cli": "^20.0.0",
 		"@commitlint/config-conventional": "^20.0.0",
+		"@eslint/eslintrc": "^3.3.3",
+		"@eslint/js": "^9.39.2",
 		"@posthog/nextjs-config": "^1.3.6",
 		"@tailwindcss/postcss": "^4.1.15",
 		"@testing-library/jest-dom": "^6.9.1",
@@ -55,8 +57,8 @@
 		"@typescript-eslint/parser": "^8.46.2",
 		"@vitest/coverage-v8": "^4.0.1",
 		"@vitest/ui": "^4.0.1",
-		"eslint": "^9.38.0",
-		"eslint-config-next": "15.5.6",
+		"eslint": "^9.39.2",
+		"eslint-config-next": "16.1.1",
 		"happy-dom": "^20.0.8",
 		"husky": "^9.0.0",
 		"lint-staged": "^16.0.0",
@@ -65,6 +67,7 @@
 		"prettier-plugin-tailwindcss": "^0.7.1",
 		"tailwindcss": "^4.1.15",
 		"typescript": "^5.9.3",
+		"typescript-eslint": "^8.50.1",
 		"vitest": "^4.0.1"
 	},
 	"ct3aMetadata": {

src/components/CopyButton.tsx

@@ -70,8 +70,11 @@ const CopyButton: FunctionComponent<CopyButtonProps> = ({
 	// Consolidated timer effect: Reset copied state, tooltip, and force-open flag
 	useEffect(() => {
 		if (copied) {
+			// Schedule state updates to avoid synchronous setState in effect
+			queueMicrotask(() => {
 				forceOpenRef.current = true;
 				setTooltipOpen(true);
+			});
 
 			const timer = setTimeout(() => {
 				setCopied(false);

src/components/ThemeToggle.tsx

@@ -27,7 +27,8 @@ export const ThemeToggle = () => {
 
 	// Avoid hydration mismatch by only rendering after mount
 	useEffect(() => {
-		setMounted(true);
+		// Schedule state update to avoid synchronous setState in effect
+		queueMicrotask(() => setMounted(true));
 	}, []);
 
 	if (!mounted) {

src/rdap/components/LookupInput.tsx

@@ -145,7 +145,7 @@ const LookupInput: FunctionComponent<LookupInputProps> = ({
 		if (showingPlaceholder) {
 			setShowingPlaceholder(false);
 		}
-	}, [detectedType]);
+	}, [detectedType, showingPlaceholder]);
 
 	/**
 	 * Restore focus to the input when loading completes.
@@ -160,6 +160,7 @@ const LookupInput: FunctionComponent<LookupInputProps> = ({
 		}
 	}, [isLoading]);
 
+	/* eslint-disable react-hooks/refs -- False positive: isFocusedRef only accessed in event handlers, not during render */
 	return (
 		<form
 			className="pb-2.5"
@@ -342,6 +343,7 @@ const LookupInput: FunctionComponent<LookupInputProps> = ({
 			</Flex>
 		</form>
 	);
+	/* eslint-enable react-hooks/refs */
 };
 
 export default LookupInput;