diff --git a/lib/esm-bridge.cjs b/lib/esm-bridge.cjs
new file mode 100644
index 0000000..d9baa7b
--- /dev/null
+++ b/lib/esm-bridge.cjs
@@ -0,0 +1,14 @@
+'use strict';
+
+const pathFn = require('path');
+const { pathToFileURL } = require('url');
+
+// Hexo runs files under scripts/ as CJS text in a vm sandbox, where ESM syntax
+// and direct dynamic import() are unavailable (hexojs/hexo#5525). Each script is
+// therefore a one-line CJS stub calling this bridge, which lives outside the vm
+// and can import() the real ESM module from lib/. Delete the stubs and this file
+// once hexo loads ESM scripts natively (hexojs/hexo#5820).
+exports.load = function load(hexo, relToLib) {
+    const url = pathToFileURL(pathFn.join(__dirname, relToLib));
+    return import(url.href).then(m => m.default(hexo));
+};
diff --git a/lib/filters/after_post_render.js b/lib/filters/after_post_render.js
new file mode 100644
index 0000000..89e2870
--- /dev/null
+++ b/lib/filters/after_post_render.js
@@ -0,0 +1,39 @@
+import pathFn from 'path';
+
+export default function register(hexo) {
+    function image_version(oldPath, { thumbProfile = 'body', hugeProfile = 'huge' } = {}) {
+        const dir = pathFn.dirname(oldPath);
+        let base = pathFn.basename(oldPath);
+
+        // if base already starts with a prefix
+        for (const key in hexo.config.responsive_images.sizes) {
+            if (base.startsWith(key + '_')) {
+                thumbProfile = key;
+                base = base.slice(key.length + 1);
+                break;
+            }
+        }
+
+        if (dir === '.') {
+            return {
+                thumb: thumbProfile + '_' + base,
+                huge: hugeProfile + '_' + base,
+            };
+        }
+        return {
+            thumb: dir + '/' + thumbProfile + '_' + base,
+            huge: dir + '/' + hugeProfile + '_' + base,
+        };
+    }
+
+    function mediumZoomFilter(post) {
+        post.content = post.content.replace(/(<img[^>]*?) src="([^"]+)"/img, (match, p1, p2) => {
+            hexo.log.info('Responsive image', p2);
+            const { thumb, huge } = image_version(p2);
+            return `${p1} data-zoom-src="${huge}" src="${thumb}"`;
+        });
+    }
+
+    // the priority must before the next theme's img lazy load filter's 0
+    hexo.extend.filter.register('after_post_render', mediumZoomFilter, -10);
+}
diff --git a/lib/tags/open_sidebar.js b/lib/tags/open_sidebar.js
new file mode 100644
index 0000000..2df16c2
--- /dev/null
+++ b/lib/tags/open_sidebar.js
@@ -0,0 +1,23 @@
+import _ from 'lodash';
+
+/**
+ * A link to open sidebar. Basically only adds open-sidebar class to the tag.
+ *
+ * Syntax:
+ *   {% open_sidebar text [, title] %}
+ */
+export default function register(hexo) {
+    function openSidebarTag(args) {
+        var [text, title] = args.join(' ').split(',');
+        if (!text) return;
+
+        if (title) {
+            title = _.trim(title);
+            title = `title="${title}"`;
+        }
+        // the href has to be a fragment, so it's pjax safe
+        return `<a href="#" class="open-sidebar" ${title} >${text}</a>`;
+    }
+
+    hexo.extend.tag.register('open_sidebar', openSidebarTag, { ends: false });
+}
diff --git a/lib/tags/post_link.js b/lib/tags/post_link.js
new file mode 100644
index 0000000..3059fbd
--- /dev/null
+++ b/lib/tags/post_link.js
@@ -0,0 +1,39 @@
+import { htmlTag } from 'hexo-util';
+
+/**
+ * Post link tag
+ *
+ * Syntax:
+ *   {% post_link slug[#fragment] [title] %}
+ */
+export default function register(hexo) {
+    const Post = hexo.model('Post');
+
+    function postLinkTag(args) {
+        let slug = args.shift();
+
+        if (!slug) return;
+
+        let frag = '';
+        [slug, frag] = slug.split('#');
+        if (!frag) {
+            frag = '';
+        }
+
+        if (frag.length > 0) {
+            frag = '#' + frag;
+        }
+
+        let post = Post.findOne({ slug });
+        if (!post) return;
+
+        let title = args.length ? args.join(' ') : post.title;
+
+        return htmlTag('a', {
+            href: hexo.config.root + post.path + frag,
+            title: title
+        }, title);
+    }
+
+    hexo.extend.tag.register('post_link', postLinkTag, { ends: false });
+}
diff --git a/lib/tags/random_xkcd.js b/lib/tags/random_xkcd.js
new file mode 100644
index 0000000..e955f37
--- /dev/null
+++ b/lib/tags/random_xkcd.js
@@ -0,0 +1,40 @@
+import util from 'util';
+import crypto from 'crypto';
+
+import xkcdApi from 'xkcd-api';
+
+const xkcd_get = util.promisify(xkcdApi.get);
+
+export default function register(hexo) {
+    async function randomXkcd() {
+        // Hexo >= 7 invokes tags with the nunjucks render context as `this`, which has no
+        // `site`. Go through hexo's locals instead, which works on every version.
+        const comics = hexo.locals.get('data').xkcd || [];
+        const infos = await Promise.all(comics.map(c => xkcd_get(c)));
+        // build a JSON list with less info to include in the page
+        const list = infos.map(el => ({
+            num: el.num,
+            alt: el.alt,
+            title: el.title,
+            img: el.img
+        }));
+
+        const tag_id = crypto.randomBytes(4).toString('hex');
+        return `<a id="${tag_id}" ref="external" target="_blank"><img data-proofer-ignore/></a>
+    <script type="text/javascript" data-pjax>
+        (() => {
+            window.xkcd_infos = window.xkcd_infos || ${JSON.stringify(list)};
+            const thecomic = xkcd_infos[Math.floor(Math.random() * xkcd_infos.length)];
+            const atag = document.getElementById("${tag_id}");
+            if (atag) {
+                atag.setAttribute('href', 'https://xkcd.com/' + thecomic.num);
+                atag.firstChild.setAttribute('src', thecomic.img);
+                atag.firstChild.setAttribute('alt', thecomic.title);
+                atag.firstChild.setAttribute('title', thecomic.alt);
+            }
+        })();
+    </script>`;
+    }
+
+    hexo.extend.tag.register('random_xkcd', randomXkcd, { ends: false, async: true });
+}
diff --git a/package.json b/package.json
index fc08830..80292e1 100644
--- a/package.json
+++ b/package.json
@@ -2,6 +2,7 @@
   "name": "hexo-site",
   "version": "0.0.0",
   "private": true,
+  "type": "module",
   "hexo": {
     "version": "8.1.2"
   },
diff --git a/scripts/filters/after_post_render.js b/scripts/filters/after_post_render.js
index e19d57a..e413dd0 100644
--- a/scripts/filters/after_post_render.js
+++ b/scripts/filters/after_post_render.js
@@ -1,44 +1,3 @@
 'use strict';
-
-const pathFn = require('path');
-
-function image_version(oldPath, { thumbProfile = 'body', hugeProfile = 'huge' } = {}) {
-    const dir = pathFn.dirname(oldPath);
-    let base = pathFn.basename(oldPath);
-
-    // if base already starts with a prefix
-    for (const key in hexo.config.responsive_images.sizes) {
-        if (base.startsWith(key + '_')) {
-            thumbProfile = key;
-            base = base.slice(key.length + 1);
-            break;
-        }
-    }
-
-    if (dir === '.') {
-        return {
-            thumb: thumbProfile + '_' + base,
-            huge: hugeProfile + '_' + base,
-        };
-    }
-    return {
-        thumb: dir + '/' + thumbProfile + '_' + base,
-        huge: dir + '/' + hugeProfile + '_' + base,
-    };
-}
-
-function mediumZoomFilter(post) {
-    const content = post.content;
-    post.content = post.content.replace(/(<img[^>]*?) src="([^"]+)"/img, (match, p1, p2) => {
-        hexo.log.info('Responsive image', p2);
-        const { thumb, huge } = image_version(p2);
-        return `${p1} data-zoom-src="${huge}" src="${thumb}"`;
-    });
-
-    if (content.includes('img')) {
-        // console.log('after render', content);
-    }
-}
-
-// the priority must before the next theme's img lazy load filter's 0
-hexo.extend.filter.register('after_post_render', mediumZoomFilter, -10);
+// CJS stub: hexo runs scripts/ files as CJS in a vm; real logic is ESM in lib/. See lib/esm-bridge.cjs.
+await require('../../lib/esm-bridge.cjs').load(hexo, 'filters/after_post_render.js');
diff --git a/scripts/tags/open_sidebar.js b/scripts/tags/open_sidebar.js
index 541d8e2..179aa5e 100644
--- a/scripts/tags/open_sidebar.js
+++ b/scripts/tags/open_sidebar.js
@@ -1,23 +1,3 @@
 'use strict';
-
-const _ = require('lodash');
-
-/**
- * A link to open sidebar. Basically only adds open-sidebar class to the tag.
- *
- * Syntax:
- *   {% open_sidebar text [, title] %}
- */
-function openSidebarTag(args) {
-    var [text, title] = args.join(' ').split(',');
-    if (!text) return;
-
-    if (title) {
-        title = _.trim(title);
-        title = `title="${title}"`;
-    }
-    // the href has to be a fragment, so it's pjax safe
-    return `<a href="#" class="open-sidebar" ${title} >${text}</a>`;
-};
-
-hexo.extend.tag.register('open_sidebar', openSidebarTag, { ends: false });
+// CJS stub: hexo runs scripts/ files as CJS in a vm; real logic is ESM in lib/. See lib/esm-bridge.cjs.
+await require('../../lib/esm-bridge.cjs').load(hexo, 'tags/open_sidebar.js');
diff --git a/scripts/tags/post_link.js b/scripts/tags/post_link.js
index 35bf98c..a9e446b 100644
--- a/scripts/tags/post_link.js
+++ b/scripts/tags/post_link.js
@@ -1,38 +1,3 @@
 'use strict';
-
-const { htmlTag } = require('hexo-util');
-const Post = hexo.model('Post');
-
-/**
- * Post link tag
- *
- * Syntax:
- *   {% post_link slug[#fragment] [title] %}
- */
-function postLinkTag(args) {
-    let slug = args.shift();
-
-    if (!slug) return;
-
-    let frag = '';
-    [slug, frag] = slug.split('#');
-    if (!frag) {
-        frag = '';
-    }
-
-    if (frag.length > 0) {
-        frag = '#' + frag;
-    }
-
-    let post = Post.findOne({ slug });
-    if (!post) return;
-
-    let title = args.length ? args.join(' ') : post.title;
-
-    return htmlTag('a', {
-        href: hexo.config.root + post.path + frag,
-        title: title
-    }, title);
-};
-
-hexo.extend.tag.register('post_link', postLinkTag, { ends: false });
\ No newline at end of file
+// CJS stub: hexo runs scripts/ files as CJS in a vm; real logic is ESM in lib/. See lib/esm-bridge.cjs.
+await require('../../lib/esm-bridge.cjs').load(hexo, 'tags/post_link.js');
diff --git a/scripts/tags/random_xkcd.js b/scripts/tags/random_xkcd.js
index 5ff9be7..484f103 100644
--- a/scripts/tags/random_xkcd.js
+++ b/scripts/tags/random_xkcd.js
@@ -1,38 +1,3 @@
 'use strict';
-
-const util = require('util');
-const crypto = require('crypto');
-
-const xkcd_get = util.promisify(require('xkcd-api').get);
-
-async function randomXkcd() {
-    // Hexo >= 7 invokes tags with the nunjucks render context as `this`, which has no
-    // `site`. Go through hexo's locals instead, which works on every version.
-    const comics = hexo.locals.get('data').xkcd || [];
-    const infos = await Promise.all(comics.map(c => xkcd_get(c)));
-    // build a JSON list with less info to include in the page
-    const list = infos.map(el => ({
-        num: el.num,
-        alt: el.alt,
-        title: el.title,
-        img: el.img
-    }));
-
-    const tag_id = crypto.randomBytes(4).toString('hex');
-    return `<a id="${tag_id}" ref="external" target="_blank"><img data-proofer-ignore/></a>
-    <script type="text/javascript" data-pjax>
-        (() => {
-            window.xkcd_infos = window.xkcd_infos || ${JSON.stringify(list)};
-            const thecomic = xkcd_infos[Math.floor(Math.random() * xkcd_infos.length)];
-            const atag = document.getElementById("${tag_id}");
-            if (atag) {
-                atag.setAttribute('href', 'https://xkcd.com/' + thecomic.num);
-                atag.firstChild.setAttribute('src', thecomic.img);
-                atag.firstChild.setAttribute('alt', thecomic.title);
-                atag.firstChild.setAttribute('title', thecomic.alt);
-            }
-        })();
-    </script>`;
-}
-
-hexo.extend.tag.register('random_xkcd', randomXkcd, { ends: false, async: true });
+// CJS stub: hexo runs scripts/ files as CJS in a vm; real logic is ESM in lib/. See lib/esm-bridge.cjs.
+await require('../../lib/esm-bridge.cjs').load(hexo, 'tags/random_xkcd.js');
diff --git a/tests/helpers/index.js b/tests/helpers/index.js
index b226dd0..dbf5741 100644
--- a/tests/helpers/index.js
+++ b/tests/helpers/index.js
@@ -1,7 +1,10 @@
-const fs = require('fs/promises');
-const pathFn = require('path');
-const { JSDOM } = require('jsdom');
+import fs from 'fs/promises';
+import pathFn from 'path';
+import { fileURLToPath } from 'url';
 
+import { JSDOM } from 'jsdom';
+
+const __dirname = pathFn.dirname(fileURLToPath(import.meta.url));
 const PUBLIC_DIR = pathFn.resolve(__dirname, "..", "..", "public");
 
 async function recursiveRoutes(basedir, prefixUrl) {
@@ -18,27 +21,23 @@ async function recursiveRoutes(basedir, prefixUrl) {
     return fileRoutes.concat(subRoutes);
 }
 
-async function listRoutes() {
+export async function listRoutes() {
     return await recursiveRoutes(pathFn.join(PUBLIC_DIR, 'blog'), '/');
 }
 
-async function getRoute(path) {
+export async function getRoute(path) {
     return await JSDOM.fromFile(pathFn.join(PUBLIC_DIR, path));
 }
 
-async function getRouteFile(path) {
+export async function getRouteFile(path) {
     return await fs.readFile(pathFn.join(PUBLIC_DIR, path), { encoding: 'utf-8' });
 }
 
-async function getHexo(level) {
-    const Hexo = require('hexo');
+export async function getHexo(level) {
+    // import lazily so tests not using hexo don't pay for loading it
+    const { default: Hexo } = await import('hexo');
     const hexo = new Hexo();
     hexo.log.level = level || 40 // WARN;
     await hexo.init();
     return hexo;
 }
-
-module.exports.getRoute = getRoute;
-module.exports.getRouteFile = getRouteFile;
-module.exports.getHexo = getHexo;
-module.exports.listRoutes = listRoutes;
diff --git a/tests/math-rendering.js b/tests/math-rendering.js
index ce130ff..1a1ea2f 100644
--- a/tests/math-rendering.js
+++ b/tests/math-rendering.js
@@ -1,6 +1,8 @@
-const test = require('ava');
-const fs = require('fs/promises');
-const { getHexo } = require('./helpers');
+import fs from 'fs/promises';
+
+import test from 'ava';
+
+import { getHexo } from './helpers/index.js';
 
 const saveHtml = false;
 
diff --git a/tests/ocs_site_verification.js b/tests/ocs_site_verification.js
index 6315ab7..9341136 100644
--- a/tests/ocs_site_verification.js
+++ b/tests/ocs_site_verification.js
@@ -1,5 +1,6 @@
-const test = require('ava');
-const { getRoute } = require('./helpers');
+import test from 'ava';
+
+import { getRoute } from './helpers/index.js';
 
 test('home page contains OCS site verification', async t => {
     const dom = await getRoute('index.html');
diff --git a/tests/post.js b/tests/post.js
index c64eddd..45f0584 100644
--- a/tests/post.js
+++ b/tests/post.js
@@ -1,5 +1,6 @@
-const test = require('ava');
-const { getRoute, listRoutes } = require('./helpers');
+import test from 'ava';
+
+import { getRoute, listRoutes } from './helpers/index.js';
 
 test('has tags in header', async t => {
     const dom = await getRoute('blog/2016/08/20/gsoc-kdevelop-lldb-final-report/index.html');
diff --git a/tests/prism-rendering.js b/tests/prism-rendering.js
index 8eb77c4..bba4aec 100644
--- a/tests/prism-rendering.js
+++ b/tests/prism-rendering.js
@@ -1,5 +1,6 @@
-const test = require('ava');
-const { getRouteFile } = require('./helpers');
+import test from 'ava';
+
+import { getRouteFile } from './helpers/index.js';
 
 test('prism bundle contains language', async t => {
     const js = await getRouteFile('assets/prism-bundle.js');