diff --git a/CLAUDE.md b/CLAUDE.md
index 3cab993..6ed861e 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -151,13 +151,15 @@ After any edit to it:
 ```sh
 npx tsc -p .
 node tests/page-smoke.js
+node --test tests/page-unit.js
 ```
 
 The first type-checks `web/src` (loosely: `strict` is off, and `$` returns `any`). The second
 builds the page as shipped and runs its script against a stub DOM, checking every selector it
 wires at load actually exists. That check exists because a patch once anchored on a deleted
 function, `String.replace` silently matched nothing, and the whole UI died with a
-`ReferenceError` while every server-side test passed.
+`ReferenceError` while every server-side test passed. The third loads the same built script and
+calls its helpers directly (#234): a pure function added to the page gets its check there.
 
 Patching that file by guessing an anchor string has failed repeatedly. Read the exact block first
 (`sed -n 'START,ENDp'`), match it verbatim, and assert the replacement happened rather than hoping.
@@ -168,6 +170,7 @@ Patching that file by guessing an anchor string has failed repeatedly. Read the
 cargo test                # ~80 tests: parsing, filters, retention, schedules, SQL, per-user state
 npx tsc -p .              # type-checks web/src
 node tests/page-smoke.js
+node --test tests/page-unit.js  # the page's own functions, called directly, in a second
 node tests/native-bridge.js  # the page hands playback to a native shell
 node tests/contrast.js    # every theme's palette against WCAG AA
 npx playwright test       # 66 browser tests against a real daemon on fixture feeds
diff --git a/tests/page-unit.js b/tests/page-unit.js
new file mode 100644
index 0000000..4d9b393
--- /dev/null
+++ b/tests/page-unit.js
@@ -0,0 +1,132 @@
+// Unit tests for the page's own functions (#234): the script as shipped, loaded into the stub DOM
+// page-smoke.js uses, and its helpers called directly. The browser suite tests what people do;
+// this tests the small pieces it is made of, in a second, with nothing running.
+//
+//   node --test tests/page-unit.js
+//
+// The files in web/src are one script, not modules. Its top-level `function`s are properties of
+// the context; its top-level `const`s are not, but a script run in the same context sees them, as
+// a second <script> on a page would, so `run` evaluates an expression there.
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const { makeContext, vm } = require('./dom-stub.js');
+const { buildPage } = require('../web/build.mjs');
+
+const { html, js } = buildPage('index.html');
+const { ctx } = makeContext(html, js);
+vm.createContext(ctx);
+vm.runInContext(js, ctx, { filename: 'index.html<script>', timeout: 5000 });
+const run = expr => vm.runInContext(expr, ctx);
+// Time as the page sees it, for the helpers that count from now.
+const NOW = 1_800_000_000;
+run(`Date.now = () => ${NOW * 1000}`);
+
+test('esc makes text safe to put in markup and attributes', () => {
+  assert.equal(run(`esc('<a href="x">Tom & Jerry\\'s</a>')`), '&lt;a href=&quot;x&quot;&gt;Tom &amp; Jerry&#39;s&lt;/a&gt;');
+  assert.equal(run('esc(null)'), '');
+  assert.equal(run('esc(undefined)'), '');
+});
+
+test('clock reads seconds as a player does', () => {
+  assert.equal(run('clock(0)'), '0:00');
+  assert.equal(run('clock(65)'), '1:05');
+  assert.equal(run('clock(3661)'), '1:01:01');
+  assert.equal(run('clock(59.9)'), '0:59');
+  assert.equal(run('clock(-5)'), '0:00');
+  assert.equal(run('clock(undefined)'), '0:00');
+});
+
+test('mb sizes a file in the unit that reads best', () => {
+  assert.equal(run('mb(0)'), '');
+  // An article's small image is not "0 KB" or "0 MB".
+  assert.equal(run('mb(100)'), '1 KB');
+  assert.equal(run('mb(2048)'), '2 KB');
+  assert.equal(run('mb(5 * 1048576)'), '5 MB');
+  assert.equal(run('mb(1.5 * 1073741824)'), '1.5 GB');
+});
+
+test('ago says how long since, and never for nothing', () => {
+  assert.equal(run('ago(0)'), 'never');
+  assert.equal(run(`ago(${NOW - 10})`), '1m ago');
+  assert.equal(run(`ago(${NOW - 45 * 60})`), '45m ago');
+  assert.equal(run(`ago(${NOW - 5 * 3600})`), '5h ago');
+  assert.equal(run(`ago(${NOW - 3 * 86400})`), '3d ago');
+  // Past a month, a date: whatever the locale, it names the year.
+  assert.match(run(`ago(${NOW - 90 * 86400})`), /2026/);
+});
+
+test('due says how long until a feed is checked', () => {
+  assert.equal(run(`due(${NOW - 1})`), 'due now');
+  assert.equal(run(`due(${NOW + 10})`), 'in 1m');
+  assert.equal(run(`due(${NOW + 90 * 60})`), 'in 2h');
+  assert.equal(run(`due(${NOW + 3 * 86400})`), 'in 3d');
+});
+
+test('DeadAir savings read as time', () => {
+  assert.equal(run('spanText(40)'), '40 s');
+  assert.equal(run('spanText(12 * 60 + 5)'), '12 min');
+  assert.equal(run('spanText(3 * 3600 + 12 * 60)'), '3 h 12 min');
+  assert.equal(run('shorter(45)'), '45 s shorter');
+  assert.equal(run('shorter(150)'), '3 min shorter');
+});
+
+test('initials and plural', () => {
+  assert.equal(run(`initials('The Verge')`), 'TV');
+  assert.equal(run(`initials('accidental tech podcast')`), 'AT');
+  assert.equal(run(`initials('')`), '?');
+  assert.equal(run(`initials('!!!')`), '?');
+  assert.equal(run(`plural(1, 'feed')`), '1 feed');
+  assert.equal(run(`plural(0, 'feed')`), '0 feeds');
+  assert.equal(run(`plural(2, 'feed')`), '2 feeds');
+});
+
+test("kindOf names a file by its type, or else its address's extension", () => {
+  const kind = enc => run(`kindOf(${JSON.stringify(enc)})`);
+  assert.equal(kind({ mime: 'image/png' }), 'image');
+  assert.equal(kind({ mime: 'Video/MP4' }), 'video');
+  assert.equal(kind({ mime: 'audio/mpeg' }), 'audio');
+  assert.equal(kind({ mime: 'application/pdf' }), 'pdf');
+  assert.equal(kind({ mime: 'application/x-bittorrent' }), 'torrent');
+  assert.equal(kind({ url: 'https://x/ep.MP3?token=1' }), 'mp3');
+  assert.equal(kind({ url: 'https://x/download' }), 'file');
+  assert.equal(kind({ url: 'https://x/a.toolongext' }), 'file');
+  assert.equal(kind({}), 'file');
+});
+
+test('an item without a title is named by its file', () => {
+  const name = e => run(`entryName(${JSON.stringify(e)})`);
+  assert.deepEqual({ ...name({ title: 'Episode 1' }) }, { text: 'Episode 1', derived: false });
+  assert.deepEqual({ ...name({ title: '  ', enclosures: [{ url: 'https://x/My%20Show%20101.mp3?x=1' }] }) },
+    { text: 'My Show 101', derived: true });
+  // A name that does not decode is shown as it is, not dropped.
+  assert.deepEqual({ ...name({ enclosures: [{ url: 'https://x/100%.mp3' }] }) }, { text: '100%', derived: true });
+});
+
+test('the directory sorts by name as people read, and by subscribers', () => {
+  const sorted = (list, by) => run(`${JSON.stringify(list)}.sort(${by}).map(p => p.title)`);
+  assert.deepEqual([...sorted([{ title: 'ep 10' }, { title: 'Ep 2' }, { title: 'ep 1' }], 'byName')], ['ep 1', 'Ep 2', 'ep 10']);
+  assert.deepEqual([...sorted([{ title: 'B', subscribers: 1 }, { title: 'C', subscribers: 5 }, { title: 'A', subscribers: 1 }], 'bySubs')],
+    ['C', 'A', 'B']);
+});
+
+test('feeds with something unread go first, in the order they came', () => {
+  const ids = run(`[{id:'a',unread:0},{id:'b',unread:3},{id:'c',unread:0},{id:'d',unread:1}].sort(unreadFirst).map(f => f.id)`);
+  assert.deepEqual([...ids], ['b', 'd', 'a', 'c']);
+});
+
+test('words for filters split on commas, blanks dropped', () => {
+  assert.deepEqual([...run(`splitWords(' one, two words ,, three ')`)], ['one', 'two words', 'three']);
+  assert.deepEqual([...run(`splitWords('')`)], []);
+});
+
+test("a file plays from DeadAir's playlist when it has one", () => {
+  assert.equal(run(`mediaSrc({ id: 7, deadair: null })`), '/media/7');
+  assert.equal(run(`mediaSrc({ id: 7 })`), '/media/7');
+  assert.equal(run(`mediaSrc({ id: 7, deadair: 0 })`), '/media/7/deadair.m3u8');
+});
+
+test('a Patreon feed is told by its address', () => {
+  assert.equal(run(`isPatreon({ url: 'https://www.patreon.com/rss/show?auth=x' })`), true);
+  assert.equal(run(`isPatreon({ url: 'https://example.com/feed' })`), false);
+  assert.equal(run('isPatreon(null)'), false);
+});