diff --git a/web/package-lock.json b/web/package-lock.json
index 05b9dd9..f94dd2c 100644
--- a/web/package-lock.json
+++ b/web/package-lock.json
@@ -7,6 +7,11 @@
     "": {
       "name": "web",
       "version": "0.0.0",
+      "dependencies": {
+        "marked": "^18.1.2",
+        "turndown": "^7.2.4",
+        "turndown-plugin-gfm": "^1.0.2"
+      },
       "devDependencies": {
         "@sveltejs/vite-plugin-svelte": "^7.3.1",
         "svelte": "^5.57.2",
@@ -63,6 +68,12 @@
         "@jridgewell/sourcemap-codec": "^1.4.14"
       }
     },
+    "node_modules/@mixmark-io/domino": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/@mixmark-io/domino/-/domino-2.2.0.tgz",
+      "integrity": "sha512-Y28PR25bHXUg88kCV7nivXrP2Nj2RueZ3/l/jdx6J9f8J4nsEGcgX0Qe6lt7Pa+J79+kPiJU3LguR6O/6zrLOw==",
+      "license": "BSD-2-Clause"
+    },
     "node_modules/@oxc-project/types": {
       "version": "0.155.0",
       "resolved": "https://registry.npmjs.org/@oxc-project/types/-/types-0.155.0.tgz",
@@ -818,6 +829,18 @@
         "@jridgewell/sourcemap-codec": "^1.6.0"
       }
     },
+    "node_modules/marked": {
+      "version": "18.1.2",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-18.1.2.tgz",
+      "integrity": "sha512-DfOnvLAQ6WYeWxWO1u4RyFOeqyHup6dks5PPqnoFiooU7ipRvidO/2j8plhAHIiZg574E9ZlzSjUiPMLAzFkgg==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 20"
+      }
+    },
     "node_modules/nanoid": {
       "version": "3.3.20",
       "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.20.tgz",
@@ -998,6 +1021,25 @@
         "url": "https://github.com/sponsors/SuperchupuDev"
       }
     },
+    "node_modules/turndown": {
+      "version": "7.2.4",
+      "resolved": "https://registry.npmjs.org/turndown/-/turndown-7.2.4.tgz",
+      "integrity": "sha512-I8yFsfRzmzK0WV1pNNOA4A7y4RDfFxPRxb3t+e3ui14qSGOxGtiSP6GjeX+Y6CHb7HYaFj7ECUD7VE5kQMZWGQ==",
+      "license": "MIT",
+      "dependencies": {
+        "@mixmark-io/domino": "^2.2.0"
+      },
+      "engines": {
+        "node": ">=18",
+        "npm": ">=9"
+      }
+    },
+    "node_modules/turndown-plugin-gfm": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/turndown-plugin-gfm/-/turndown-plugin-gfm-1.0.2.tgz",
+      "integrity": "sha512-vwz9tfvF7XN/jE0dGoBei3FXWuvll78ohzCZQuOb+ZjWrs3a0XhQVomJEb2Qh4VHTPNRO4GPZh0V7VRbiWwkRg==",
+      "license": "MIT"
+    },
     "node_modules/vite": {
       "version": "8.3.5",
       "resolved": "https://registry.npmjs.org/vite/-/vite-8.3.5.tgz",
diff --git a/web/package.json b/web/package.json
index f314b8c..c191b9f 100644
--- a/web/package.json
+++ b/web/package.json
@@ -12,5 +12,10 @@
     "@sveltejs/vite-plugin-svelte": "^7.3.1",
     "svelte": "^5.57.2",
     "vite": "^8.3.5"
+  },
+  "dependencies": {
+    "marked": "^18.1.2",
+    "turndown": "^7.2.4",
+    "turndown-plugin-gfm": "^1.0.2"
   }
 }
diff --git a/web/src/App.svelte b/web/src/App.svelte
index 2d5b5b9..6eb236a 100644
--- a/web/src/App.svelte
+++ b/web/src/App.svelte
@@ -2,6 +2,7 @@
   import { onMount } from 'svelte'
   import { api } from './lib/api.js'
   import { parseRoute, buildHash, currentHash } from './lib/route.js'
+  import MarkdownEditor from './lib/MarkdownEditor.svelte'
 
   let user = $state(null)
   let loading = $state(true)
@@ -888,7 +889,7 @@
                 <option value="done">DONE</option>
               </select>
             </label>
-            <label>Description<textarea bind:value={editDesc}></textarea></label>
+            <MarkdownEditor bind:value={editDesc} label="Description" />
             <button class="primary" onclick={saveTicket}>Save</button>
 
             <h3>Time</h3>
diff --git a/web/src/app.css b/web/src/app.css
index cc40c47..07426e9 100644
--- a/web/src/app.css
+++ b/web/src/app.css
@@ -109,6 +109,13 @@ code {
   padding: 0.05em 0.35em;
   font-size: 0.9em;
 }
+pre code {
+  background: none;
+  border: none;
+  border-radius: 0;
+  padding: 0;
+  font-size: inherit;
+}
 
 .app-shell {
   width: 100%;
@@ -444,3 +451,144 @@ td, th {
 th { color: var(--muted); font-weight: 600; }
 label { display: grid; gap: 0.3rem; color: var(--muted); font-size: 0.9rem; }
 label > :is(input, select, textarea) { color: var(--ink); }
+
+.md-editor {
+  display: grid;
+  gap: 0.35rem;
+}
+.md-editor-head {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 0.75rem;
+  flex-wrap: wrap;
+}
+.md-editor-label {
+  color: var(--muted);
+  font-size: 0.9rem;
+}
+.md-editor-modes {
+  display: inline-flex;
+  border: 1px solid var(--line);
+  border-radius: 6px;
+  overflow: hidden;
+  background: #10151a;
+}
+.md-editor-modes button {
+  padding: 0.3rem 0.75rem;
+  border-radius: 0;
+  font-size: 0.82rem;
+  color: var(--muted);
+  background: transparent;
+}
+.md-editor-modes button:hover {
+  color: var(--ink);
+  background: color-mix(in srgb, var(--panel-2) 70%, transparent);
+}
+.md-editor-modes button.active {
+  color: var(--ink);
+  background: color-mix(in srgb, var(--accent) 28%, transparent);
+}
+.md-toolbar {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.15rem;
+  padding: 0.25rem;
+  border: 1px solid var(--line);
+  border-bottom: none;
+  border-radius: 6px 6px 0 0;
+  background: var(--panel-2);
+}
+.md-toolbar button {
+  padding: 0.3rem 0.55rem;
+  font-size: 0.82rem;
+  border-radius: 4px;
+  color: var(--muted);
+}
+.md-toolbar button:hover {
+  color: var(--ink);
+  background: color-mix(in srgb, var(--panel) 80%, transparent);
+}
+.md-visual,
+.md-source {
+  min-height: 14rem;
+  border: 1px solid var(--line);
+  border-radius: 0 0 6px 6px;
+  padding: 0.75rem 0.85rem;
+  background: #10151a;
+  color: var(--ink);
+  outline: none;
+}
+.md-source {
+  border-radius: 6px;
+  resize: vertical;
+  font-family: "IBM Plex Mono", "SF Mono", ui-monospace, monospace;
+  font-size: 0.9rem;
+  line-height: 1.5;
+}
+.md-visual {
+  overflow-y: auto;
+  line-height: 1.55;
+}
+.md-visual:focus,
+.md-source:focus {
+  border-color: color-mix(in srgb, var(--accent) 55%, var(--line));
+}
+.md-visual :first-child { margin-top: 0; }
+.md-visual :last-child { margin-bottom: 0; }
+.md-visual h1,
+.md-visual h2,
+.md-visual h3 {
+  margin: 0.85em 0 0.4em;
+  font-weight: 650;
+  color: #f0f4f8;
+}
+.md-visual h1 { font-size: 1.35rem; }
+.md-visual h2 { font-size: 1.15rem; }
+.md-visual h3 { font-size: 1.05rem; }
+.md-visual p { margin: 0.5em 0; }
+.md-visual ul,
+.md-visual ol {
+  margin: 0.5em 0;
+  padding-left: 1.4rem;
+}
+.md-visual li { margin: 0.2em 0; }
+.md-visual li > input[type="checkbox"] {
+  width: auto;
+  margin-right: 0.4rem;
+  accent-color: var(--accent);
+  vertical-align: middle;
+}
+.md-visual a { color: var(--accent); }
+.md-visual pre,
+.md-visual code {
+  font-family: "IBM Plex Mono", "SF Mono", ui-monospace, monospace;
+  font-size: 0.88em;
+}
+.md-visual pre {
+  margin: 0.6em 0;
+  padding: 0.65rem 0.75rem;
+  border: 1px solid var(--line);
+  border-radius: 4px;
+  background: #0c1014;
+  overflow-x: auto;
+  white-space: pre-wrap;
+}
+.md-visual pre code {
+  background: none;
+  border: none;
+  padding: 0;
+  font-size: inherit;
+  color: inherit;
+}
+.md-visual blockquote {
+  margin: 0.6em 0;
+  padding: 0.15rem 0 0.15rem 0.75rem;
+  border-left: 3px solid color-mix(in srgb, var(--accent) 50%, var(--line));
+  color: var(--muted);
+}
+.md-visual hr {
+  border: none;
+  border-top: 1px solid var(--line);
+  margin: 1em 0;
+}
diff --git a/web/src/lib/MarkdownEditor.svelte b/web/src/lib/MarkdownEditor.svelte
new file mode 100644
index 0000000..084eec6
--- /dev/null
+++ b/web/src/lib/MarkdownEditor.svelte
@@ -0,0 +1,136 @@
+<script>
+  import { markdownToHtml, htmlToMarkdown } from './markdown.js'
+
+  let { value = $bindable(''), label = 'Description' } = $props()
+
+  let mode = $state('visual')
+  let visualEl = $state(null)
+  let lastApplied = ''
+  let appliedTo = null
+
+  function enableCheckboxes(root) {
+    if (!root) return
+    root.querySelectorAll('input[type="checkbox"]').forEach((box) => {
+      box.disabled = false
+      box.onchange = readVisual
+    })
+  }
+
+  function applyVisual(md) {
+    if (!visualEl) return
+    visualEl.innerHTML = markdownToHtml(md || '')
+    enableCheckboxes(visualEl)
+    lastApplied = md || ''
+    appliedTo = visualEl
+  }
+
+  function readVisual() {
+    if (!visualEl) return
+    value = htmlToMarkdown(visualEl.innerHTML)
+    lastApplied = value
+  }
+
+  function setMode(next) {
+    if (next === mode) return
+    if (mode === 'visual') readVisual()
+    mode = next
+  }
+
+  $effect(() => {
+    if (mode !== 'visual') return
+    const el = visualEl
+    if (!el) return
+    const md = value ?? ''
+    // Remount (mode switch) or external value change (e.g. restore revision)
+    if (el !== appliedTo || md !== lastApplied) applyVisual(md)
+  })
+
+  function exec(cmd, arg) {
+    visualEl?.focus()
+    document.execCommand(cmd, false, arg)
+    readVisual()
+  }
+
+  function insertChecklist() {
+    visualEl?.focus()
+    document.execCommand(
+      'insertHTML',
+      false,
+      '<ul><li><input type="checkbox"> Task</li></ul>',
+    )
+    enableCheckboxes(visualEl)
+    readVisual()
+  }
+
+  function promptLink() {
+    const url = window.prompt('URL')
+    if (!url) return
+    exec('createLink', url)
+  }
+
+  function formatCodeBlock() {
+    visualEl?.focus()
+    const sel = window.getSelection()
+    const text = sel?.toString() || 'code'
+    // Prefer <pre><code> so turndown emits a fenced markdown block.
+    const escaped = text
+      .replace(/&/g, '&amp;')
+      .replace(/</g, '&lt;')
+      .replace(/>/g, '&gt;')
+    document.execCommand('insertHTML', false, `<pre><code>${escaped}</code></pre>`)
+    readVisual()
+  }
+</script>
+
+<div class="md-editor">
+  <div class="md-editor-head">
+    <span class="md-editor-label">{label}</span>
+    <div class="md-editor-modes" role="tablist">
+      <button
+        type="button"
+        role="tab"
+        class:active={mode === 'visual'}
+        aria-selected={mode === 'visual'}
+        onclick={() => setMode('visual')}
+      >Visual</button>
+      <button
+        type="button"
+        role="tab"
+        class:active={mode === 'markdown'}
+        aria-selected={mode === 'markdown'}
+        onclick={() => setMode('markdown')}
+      >Markdown</button>
+    </div>
+  </div>
+
+  {#if mode === 'visual'}
+    <div class="md-toolbar" role="toolbar" aria-label="Formatting">
+      <button type="button" title="Bold" onclick={() => exec('bold')}><b>B</b></button>
+      <button type="button" title="Italic" onclick={() => exec('italic')}><i>I</i></button>
+      <button type="button" title="Heading" onclick={() => exec('formatBlock', 'h2')}>H</button>
+      <button type="button" title="Bullet list" onclick={() => exec('insertUnorderedList')}>• List</button>
+      <button type="button" title="Numbered list" onclick={() => exec('insertOrderedList')}>1.</button>
+      <button type="button" title="Checklist" onclick={insertChecklist}>☑</button>
+      <button type="button" title="Link" onclick={promptLink}>Link</button>
+      <button type="button" title="Code block" onclick={formatCodeBlock}>Code</button>
+    </div>
+    <div
+      class="md-visual"
+      contenteditable="true"
+      role="textbox"
+      aria-multiline="true"
+      aria-label={label}
+      bind:this={visualEl}
+      oninput={readVisual}
+      onblur={readVisual}
+    ></div>
+  {:else}
+    <textarea
+      class="md-source"
+      bind:value
+      aria-label="{label} (Markdown)"
+      placeholder="Write Markdown…"
+      spellcheck="true"
+    ></textarea>
+  {/if}
+</div>
diff --git a/web/src/lib/markdown.js b/web/src/lib/markdown.js
new file mode 100644
index 0000000..cba525d
--- /dev/null
+++ b/web/src/lib/markdown.js
@@ -0,0 +1,42 @@
+import { marked } from 'marked'
+import TurndownService from 'turndown'
+import { gfm } from 'turndown-plugin-gfm'
+
+marked.setOptions({
+  gfm: true,
+  breaks: false,
+})
+
+const turndown = new TurndownService({
+  headingStyle: 'atx',
+  codeBlockStyle: 'fenced',
+  bulletListMarker: '-',
+  emDelimiter: '*',
+})
+turndown.use(gfm)
+
+// Browsers' formatBlock('pre') often yields bare <pre> without <code>.
+// Default turndown only fences <pre><code>; keep bare <pre> as fenced blocks.
+turndown.addRule('barePre', {
+  filter(node) {
+    return (
+      node.nodeName === 'PRE' &&
+      !(node.firstChild && node.firstChild.nodeName === 'CODE')
+    )
+  },
+  replacement(_content, node) {
+    const text = node.textContent.replace(/\n$/, '')
+    return `\n\n\`\`\`\n${text}\n\`\`\`\n\n`
+  },
+})
+
+export function markdownToHtml(md) {
+  if (!md || !md.trim()) return '<p><br></p>'
+  return marked.parse(md)
+}
+
+export function htmlToMarkdown(html) {
+  if (!html) return ''
+  const md = turndown.turndown(html)
+  return md.replace(/\n{3,}/g, '\n\n').trim()
+}