feat: formatting buttons on the question editor — a toolbar, not a WYSIWYG

"How do I bold? add a list etc?" — answered, and the interesting part is
what it is not.

Milkdown was the obvious choice; it is already in the project. Round-
tripping a question stem through it first showed why not: bullets come
back as `*` with blank lines inserted between them, tables are repadded,
and anything it does not recognise is escaped. The first two reflow text
nobody edited — and learners' highlights are stored as character offsets
into that exact string, so a reflow on any save moves every one of them.

So the text stays byte-for-byte as typed and the buttons only insert
syntax at the cursor: bold, italic, code, bullet and numbered lists
(every selected line, and already-bulleted lines left alone), heading,
a table skeleton, inline maths. The Markdown preview that was already
there shows the result.

Frontend 308/308.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TqXevQJhxFrM7jJg82cgZN

docs/TODO.md

@@ -95,9 +95,14 @@ Captured so nothing is lost while the article writing runs.
 ### Editor and figures
 - [x] **Rich editing on the question page** — no new platform needed: Milkdown
       is already installed and used for articles, courses and the quick modal.
-- [ ] **Milkdown on the stem and the options**, replacing the plain textareas.
-      Note the stem carries manual-highlight offsets, so check what a WYSIWYG
-      rewrite does to them before switching.
+- [x] **Formatting on the stem, options and explanation** — done 2026-09-11,
+      but NOT with Milkdown, and the check is why. Round-tripping a stem
+      through it showed: bullets come back as `*` with blank lines inserted,
+      tables are repadded, and `[[id|Title]]` is escaped to `\[\[…]]`. The
+      first two reflow text nobody edited, which moves every saved highlight
+      offset; the third breaks cross-references outright (fixed separately,
+      since ArticleEditor already used Milkdown). A toolbar over the plain
+      textarea gives the same buttons and changes nothing it was not asked to.
 - [x] **Many figures per question** — `question_media` links a question to any
       number of images in the bank, each with a role (stem or explanation), a
       label the prose can refer to ("Figure 1") and an order. The 346 existing

frontend/src/components/MarkdownToolbar.css

@@ -0,0 +1,25 @@
+/* Formatting buttons over a plain textarea. */
+
+.mdbar {
+  display: flex; gap: 4px; flex-wrap: wrap; align-items: center;
+  padding: 6px; margin-bottom: -1px;
+  background: var(--bg);
+  border: 1px solid var(--border); border-radius: 8px 8px 0 0;
+}
+.mdbar button {
+  min-width: 32px; min-height: 32px; padding: 4px 9px;
+  font: inherit; font-size: 0.8rem; line-height: 1;
+  background: var(--card-bg); color: var(--text-muted);
+  border: 1px solid var(--border); border-radius: 6px; cursor: pointer;
+}
+.mdbar button:hover { color: var(--primary); border-color: var(--primary); }
+
+/* The field below joins on to the bar. */
+.mdbar + textarea { border-top-left-radius: 0; border-top-right-radius: 0; }
+
+@media (max-width: 560px) {
+  /* Touch targets, and the bar scrolls rather than wrapping to three rows. */
+  .mdbar { flex-wrap: nowrap; overflow-x: auto; scrollbar-width: none; }
+  .mdbar::-webkit-scrollbar { display: none; }
+  .mdbar button { min-height: 40px; flex-shrink: 0; }
+}

frontend/src/components/MarkdownToolbar.jsx

@@ -0,0 +1,89 @@
+import './MarkdownToolbar.css'
+
+/**
+ * Markdown formatting buttons over a plain textarea.
+ *
+ * Not a WYSIWYG. Milkdown is the WYSIWYG and it is used elsewhere, but it
+ * rewrites what it is given: bullets come back as `*` with blank lines between
+ * them, tables are repadded, and anything it does not recognise gets escaped.
+ * For a question stem that is a problem twice over — learners' highlights are
+ * stored as character offsets into this exact text, so a reflow moves every one
+ * of them, and the reflow would happen on any save, including one where nothing
+ * was really edited.
+ *
+ * So the text stays exactly as typed and the buttons only insert syntax at the
+ * cursor. Bold is still one click; nothing else moves.
+ */
+
+const WRAP = 'wrap'
+const LINE = 'line'
+const BLOCK = 'block'
+
+const ACTIONS = [
+  { key: 'bold', label: 'B', title: 'Bold', kind: WRAP, before: '**', after: '**', style: { fontWeight: 800 } },
+  { key: 'italic', label: 'I', title: 'Italic', kind: WRAP, before: '*', after: '*', style: { fontStyle: 'italic' } },
+  { key: 'code', label: '<>', title: 'Code', kind: WRAP, before: '`', after: '`' },
+  { key: 'bullets', label: '• List', title: 'Bullet list', kind: LINE, prefix: '- ' },
+  { key: 'numbers', label: '1. List', title: 'Numbered list', kind: LINE, prefix: '1. ' },
+  { key: 'heading', label: 'H', title: 'Heading', kind: LINE, prefix: '### ' },
+  {
+    key: 'table', label: 'Table', title: 'Insert a table', kind: BLOCK,
+    text: '\n| Test | Value | Reference |\n| --- | --- | --- |\n|  |  |  |\n',
+  },
+  { key: 'math', label: '∑', title: 'Inline maths', kind: WRAP, before: '$', after: '$' },
+]
+
+export default function MarkdownToolbar({ textareaRef, value, onChange, label = 'Formatting' }) {
+  const apply = (action) => {
+    const field = textareaRef.current
+    if (!field) return
+    const start = field.selectionStart ?? 0
+    const end = field.selectionEnd ?? 0
+    const text = value || ''
+    let next = text
+    let caret = end
+
+    if (action.kind === WRAP) {
+      const selected = text.slice(start, end)
+      next = text.slice(0, start) + action.before + selected + action.after + text.slice(end)
+      // With nothing selected the cursor lands between the markers, ready to
+      // type; with a selection it lands after it.
+      caret = selected ? end + action.before.length + action.after.length : start + action.before.length
+    } else if (action.kind === LINE) {
+      // Whole lines, so selecting three lines makes three bullets.
+      const lineStart = text.lastIndexOf('\n', start - 1) + 1
+      const lineEnd = text.indexOf('\n', end)
+      const stop = lineEnd === -1 ? text.length : lineEnd
+      const block = text.slice(lineStart, stop)
+      const numbered = action.prefix === '1. '
+      const lines = block.split('\n').map((line, index) => (
+        line.startsWith(action.prefix) || (numbered && /^\d+\. /.test(line))
+          ? line
+          : (numbered ? `${index + 1}. ` : action.prefix) + line))
+      const replaced = lines.join('\n')
+      next = text.slice(0, lineStart) + replaced + text.slice(stop)
+      caret = lineStart + replaced.length
+    } else {
+      next = text.slice(0, start) + action.text + text.slice(end)
+      caret = start + action.text.length
+    }
+
+    onChange(next)
+    // The caret has to be restored after React has written the new value.
+    requestAnimationFrame(() => {
+      field.focus()
+      field.setSelectionRange(caret, caret)
+    })
+  }
+
+  return (
+    <div className="mdbar" role="toolbar" aria-label={label}>
+      {ACTIONS.map(action => (
+        <button type="button" key={action.key} title={action.title} aria-label={action.title}
+          style={action.style} onClick={() => apply(action)}>
+          {action.label}
+        </button>
+      ))}
+    </div>
+  )
+}

frontend/src/components/MarkdownToolbar.test.jsx

@@ -0,0 +1,77 @@
+import { describe, expect, it, vi } from 'vitest'
+import { render, screen } from '@testing-library/react'
+import userEvent from '@testing-library/user-event'
+import { useRef, useState } from 'react'
+import MarkdownToolbar from './MarkdownToolbar'
+
+function Harness({ initial = '' }) {
+  const ref = useRef(null)
+  const [value, setValue] = useState(initial)
+  return (
+    <>
+      <MarkdownToolbar textareaRef={ref} value={value} onChange={setValue} />
+      <textarea ref={ref} value={value} aria-label="Body" onChange={e => setValue(e.target.value)} />
+    </>
+  )
+}
+
+const box = () => screen.getByLabelText('Body')
+const select = (from, to) => {
+  box().setSelectionRange(from, to)
+  box().focus()
+}
+
+describe('markdown formatting buttons', () => {
+  it('wraps a selection and leaves the rest alone', async () => {
+    render(<Harness initial="fever and cough" />)
+    select(0, 5)
+    await userEvent.click(screen.getByRole('button', { name: 'Bold' }))
+    expect(box()).toHaveValue('**fever** and cough')
+  })
+
+  it('with nothing selected, opens the markers ready to type between', async () => {
+    render(<Harness initial="abc" />)
+    select(3, 3)
+    await userEvent.click(screen.getByRole('button', { name: 'Italic' }))
+    expect(box()).toHaveValue('abc**')
+  })
+
+  it('bullets every line of a selection, not just the first', async () => {
+    render(<Harness initial={'Temp 39.1\nHR 148\nRR 40'} />)
+    select(0, 22)
+    await userEvent.click(screen.getByRole('button', { name: 'Bullet list' }))
+    expect(box()).toHaveValue('- Temp 39.1\n- HR 148\n- RR 40')
+  })
+
+  it('numbers a list in sequence', async () => {
+    render(<Harness initial={'Croup\nEpiglottitis'} />)
+    select(0, 17)
+    await userEvent.click(screen.getByRole('button', { name: 'Numbered list' }))
+    expect(box()).toHaveValue('1. Croup\n2. Epiglottitis')
+  })
+
+  it('does not bullet a line that is already a bullet', async () => {
+    render(<Harness initial={'- Temp 39.1\nHR 148'} />)
+    select(0, 18)
+    await userEvent.click(screen.getByRole('button', { name: 'Bullet list' }))
+    expect(box()).toHaveValue('- Temp 39.1\n- HR 148')
+  })
+
+  it('inserts a table skeleton at the cursor', async () => {
+    render(<Harness initial="Labs:" />)
+    select(5, 5)
+    await userEvent.click(screen.getByRole('button', { name: 'Insert a table' }))
+    expect(box().value).toContain('| Test | Value | Reference |')
+    expect(box().value.startsWith('Labs:')).toBe(true)
+  })
+
+  it('leaves everything else exactly as typed — no reflow', async () => {
+    // The whole reason this is not a WYSIWYG: a stem carries learners'
+    // highlight offsets, so untouched text must come back byte for byte.
+    const original = 'Labs:\n\n| Na | 128 |\n| --- | --- |\n\n- one\n- two\n'
+    render(<Harness initial={original} />)
+    select(0, 0)
+    await userEvent.click(screen.getByRole('button', { name: 'Bold' }))
+    expect(box().value).toBe(`****${original}`)
+  })
+})

frontend/src/pages/QuestionEditPage.jsx

@@ -1,10 +1,11 @@
-import { useState, useEffect, useCallback, useMemo } from 'react'
+import { useRef, useState, useEffect, useCallback, useMemo } from 'react'
 import { Link, useLocation, useNavigate, useParams } from 'react-router-dom'
 import api from '../api/client'
 import CategoryDrilldown from '../components/CategoryDrilldown'
 import RichText from '../components/RichText'
 import ImagePicker from '../components/ImagePicker'
 import FigureManager from '../components/FigureManager'
+import MarkdownToolbar from '../components/MarkdownToolbar'
 import { uploadUrl } from '../utils/uploads'
 import './QuestionEditPage.css'
 
@@ -42,6 +43,8 @@ export default function QuestionEditPage({ mode = 'edit' }) {
   const [showVersions, setShowVersions] = useState(false)
   // Which image field the picker is filling, or null when it is closed.
   const [picking, setPicking] = useState(null)
+  const stemRef = useRef(null)
+  const explanationRef = useRef(null)
   // Back to wherever you opened this from — the bank with its filters, an
   // article, the manager — rather than always to the bank you may not have used.
   const { state } = useLocation()
@@ -205,7 +208,9 @@ export default function QuestionEditPage({ mode = 'edit' }) {
             <div className="qe-card-body">
               <label className="qe-field">
                 <span>Stem</span>
-                <textarea className="qe-stem" value={form.question_text} aria-label="Question text"
+                <MarkdownToolbar textareaRef={stemRef} value={form.question_text}
+                  label="Stem formatting" onChange={v => setField('question_text', v)} />
+                <textarea ref={stemRef} className="qe-stem" value={form.question_text} aria-label="Question text"
                   onChange={e => setField('question_text', e.target.value)} />
               </label>
               {form.question_text && (
@@ -276,8 +281,10 @@ export default function QuestionEditPage({ mode = 'edit' }) {
             <div className="qe-card-body">
               <label className="qe-field">
                 <span>Overall explanation</span>
-                <textarea className="qe-explanation" value={form.explanation} aria-label="Explanation"
-                  onChange={e => setField('explanation', e.target.value)} />
+                <MarkdownToolbar textareaRef={explanationRef} value={form.explanation}
+                  label="Explanation formatting" onChange={v => setField('explanation', v)} />
+                <textarea ref={explanationRef} className="qe-explanation" value={form.explanation}
+                  aria-label="Explanation" onChange={e => setField('explanation', e.target.value)} />
               </label>
             </div>
           </section>