See the post before you post it.

A draft is written as plain text but doesn't arrive as plain text: a URL
ending in .jpg becomes a picture, a youtu.be link becomes a player, a
nostr: reference becomes the note it points at, an npub becomes a name.
The only way to find out how yours would land was to send it.

The eye beside the paperclip — on the composer and on a reply — opens a
preview. It runs the draft through noteBody, the very renderer the feed
uses, so this isn't a lookalike of the real thing: it IS the real thing,
in a dashed frame with a PREVIEW label so it can never be mistaken for
the post itself. It follows the draft live while it's open (and only
while it's open — a render per keystroke is not free).

Attaching a picture opens it by itself. Showing you what you attached is
the answer to the question attaching it raises, and it costs no tap.

tools/compose-preview-test.js covers both the composer and a reply: the
picture renders rather than sitting there as a URL, the YouTube link
becomes a player, the preview tracks typing, and it puts itself away.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_019mrt228Upn9nNCwGixzSLx

4 files changed, 206 insertions, 5 deletions

diff --git a/src/features/messages.js b/src/features/messages.js
index 6cb3322..667c516 100644
--- a/src/features/messages.js
+++ b/src/features/messages.js
@@ -3464,12 +3464,16 @@ export function messagesFeature(ctx) {
     const row = (ev) => noteRow(ev.pubkey, ev, displayName(ev.pubkey), { open: false, focus: ev.id === s.focusId && ev.id !== c.rootId });
     // The reply box sits INLINE, right under the note it answers — it used
     // to live at the bottom of the thread, where nobody scrolled to find it.
-    const replyBox = () => h('div', { class: 'row', style: 'gap:8px;align-items:center;padding:2px 0 10px' },
+    const replyBox = () => h('div', { class: 'col', style: 'gap:8px;padding:2px 0 10px' },
+      s.preview ? draftPreview(s.draft) : null,
+      h('div', { class: 'row', style: 'gap:8px;align-items:center' },
       h('input', {
         type: 'text', class: 'grow thread-reply-input', placeholder: t('threadReplyHint'),
         value: s.draft || '',
-        onInput: (e) => { s.draft = e.target.value; },
-        onKeydown: (e) => { if (e.key === 'Enter') e.target.parentElement.querySelector('.thread-reply-send')?.click(); },
+        // a render per keystroke only while the preview is open; the morph
+        // leaves a focused field alone, so this can't fight the typing
+        onInput: (e) => { s.draft = e.target.value; if (s.preview) render(); },
+        onKeydown: (e) => { if (e.key === 'Enter') e.target.closest('.col').querySelector('.thread-reply-send')?.click(); },
       }),
       // A reply can carry a picture too — same upload, same imeta tag, same
       // paperclip. The URL lands in the draft, which is what every client
@@ -3487,9 +3491,11 @@ export function messagesFeature(ctx) {
             s.draft = ((s.draft || '').replace(/\s+$/, '') + ' ' + url).trim();
             const inp = document.querySelector('.thread-reply-input');
             if (inp) inp.value = s.draft;
+            s.preview = true; // same as the composer: show what was attached
           });
         },
       }),
+      previewBtn(!!s.preview, () => { s.preview = !s.preview; render(); }),
       h('button', {
         class: 'btn-primary thread-reply-send', disabled: !!s.sending || !!ui.postUploading,
         onClick: async () => {
@@ -3508,7 +3514,7 @@ export function messagesFeature(ctx) {
           } catch (e) { if (!e.silent) toast(e.message); }
           s.sending = false; render();
         },
-      }, s.sending ? h('span', { class: 'spinner sm' }) : t('threadReplySend')));
+      }, s.sending ? h('span', { class: 'spinner sm' }) : t('threadReplySend'))));
     // rows with the reply box slotted under the focused note (the root when
     // nothing narrower is focused; appended at the end if the focused note
     // hasn't loaded yet, so the box never disappears entirely)
@@ -3990,8 +3996,34 @@ export function messagesFeature(ctx) {
     const next = (cur ? cur + '\n' : '') + url;
     ui.profCompose = next;
     setDraft(POST_DRAFT, next);
+    // you just attached a picture; showing it IS the answer to the question
+    // attaching one raises
+    ui.postPreview = true;
   });
   const CLIP = '<svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" style="display:block"><path d="M21.44 11.05l-9.19 9.19a6 6 0 0 1-8.49-8.49l9.19-9.19a4 4 0 0 1 5.66 5.66l-9.2 9.19a2 2 0 0 1-2.83-2.83l8.49-8.48"/></svg>';
+  const EYE = '<svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" style="display:block"><path d="M1 12s4-8 11-8 11 8 11 8-4 8-11 8-11-8-11-8z"/><circle cx="12" cy="12" r="3"/></svg>';
+
+  // ---- draft preview --------------------------------------------------------
+  // A post is written as plain text, but it doesn't ARRIVE as plain text: a
+  // URL ending in .jpg becomes a picture, a youtu.be link becomes a player, a
+  // nostr: reference becomes the note it points at, an npub becomes a name.
+  // You could only find out by posting. This runs the draft through noteBody
+  // — the very renderer the feed uses — so the preview is not a lookalike of
+  // the real thing, it IS the real thing.
+  function draftPreview(text) {
+    const body = String(text || '').trim();
+    return h('div', { class: 'draft-preview' },
+      h('div', { class: 'draft-preview-tag' }, t('composePreviewTag')),
+      body
+        ? h('div', { class: 'note-text', style: 'white-space:pre-wrap;overflow-wrap:anywhere' }, ...noteBody(body))
+        : h('div', { class: 'small faint' }, t('composePreviewEmpty')));
+  }
+  const previewBtn = (on, toggle) => h('button', {
+    class: 'attach-btn' + (on ? ' on' : ''),
+    title: on ? t('composePreviewHide') : t('composePreview'),
+    'aria-label': on ? t('composePreviewHide') : t('composePreview'),
+    onClick: toggle,
+  }, h('span', { style: 'display:flex', html: EYE }));
   function postComposer() {
     if (ui.profCompose == null && !draftFor(POST_DRAFT)) return null;
     const text = composeText();
@@ -4000,8 +4032,16 @@ export function messagesFeature(ctx) {
         rows: '3', placeholder: t('profComposePh'),
         style: 'font-family:var(--sans);min-height:64px',
         value: text,
-        onInput: (ev) => { ui.profCompose = ev.target.value; setDraft(POST_DRAFT, ev.target.value); },
+        onInput: (ev) => {
+          ui.profCompose = ev.target.value;
+          setDraft(POST_DRAFT, ev.target.value);
+          // only while the preview is open — otherwise typing costs a render
+          // per keystroke for nothing. The morph never rewrites a focused
+          // field, so this can't fight the typing.
+          if (ui.postPreview) render();
+        },
       }),
+      ui.postPreview ? draftPreview(text) : null,
       h('div', { class: 'row gap6' },
         h('button', { class: 'btn-primary grow', disabled: !!ui.postUploading, onClick: async () => {
           const body = composeText().trim();
@@ -4025,6 +4065,7 @@ export function messagesFeature(ctx) {
           class: 'attach-btn', title: t('feedAttach'), 'aria-label': t('feedAttach'), disabled: !!ui.postUploading,
           onClick: () => document.getElementById('post-file')?.click(),
         }, ui.postUploading ? h('span', { class: 'spinner sm' }) : h('span', { style: 'display:flex', html: CLIP })) : null,
+        previewBtn(!!ui.postPreview, () => { ui.postPreview = !ui.postPreview; render(); }),
         h('input', {
           type: 'file', id: 'post-file', accept: 'image/*,video/*', style: 'display:none',
           onChange: async (e) => { const f = e.target.files && e.target.files[0]; e.target.value = ''; await attachMedia(f); },
diff --git a/src/i18n.js b/src/i18n.js
index 6a46823..5ec5986 100644
--- a/src/i18n.js
+++ b/src/i18n.js
@@ -715,6 +715,10 @@ const STR = {
     arkLnPaidTitle: 'Paid!',
     or: 'or',
     nlSignIn: 'Sign in',
+    composePreview: 'Preview',
+    composePreviewHide: 'Hide preview',
+    composePreviewTag: 'Preview',
+    composePreviewEmpty: 'Nothing to preview yet.',
     onbWelcomeTitle: 'Welcome to coinos',
     onbWelcomeBody: 'Bitcoin you actually hold. Your wallet is twelve words — nobody else ever has them, and they work in any wallet, anywhere.',
     onbStart: 'Create a new wallet',
diff --git a/src/style.css b/src/style.css
index c9b4368..fc25801 100644
--- a/src/style.css
+++ b/src/style.css
@@ -598,6 +598,19 @@ html.no-scroll { overflow: hidden; scrollbar-gutter: auto; }
 .quote-card.clickable { cursor: pointer; }
 .quote-card.clickable:hover { border-color: var(--line-strong); }
 .quote-loading { flex-direction: row; align-items: center; gap: 8px; }
+/* What a draft will look like once it's out there. Framed and labelled, so
+   it can hold real post content — pictures, players, quoted notes — without
+   ever being mistaken for the post itself. */
+.draft-preview {
+  border: 1px dashed var(--line-strong); border-radius: 10px;
+  padding: 10px 12px; background: var(--surface2);
+  display: flex; flex-direction: column; gap: 6px;
+}
+.draft-preview-tag {
+  font-size: 11px; font-weight: 650; letter-spacing: .04em;
+  text-transform: uppercase; color: var(--faint);
+}
+.attach-btn.on { color: var(--accent-ink); border-color: var(--accent); }
 .quote-card .note-text { font-size: 14px; }
 .quote-name { font-weight: 600; font-size: 14px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
 .quote-card .note-img { max-height: 220px; }
diff --git a/tools/compose-preview-test.js b/tools/compose-preview-test.js
new file mode 100644
index 0000000..aac7941
--- /dev/null
+++ b/tools/compose-preview-test.js
@@ -0,0 +1,143 @@
+// A post is written as plain text but doesn't arrive as plain text: a .jpg
+// URL becomes a picture, a youtu.be link becomes a player, a nostr: ref
+// becomes the note it points at. Until now the only way to find out how
+// yours would land was to post it.
+//
+// The preview runs the draft through noteBody — the renderer the feed uses —
+// so it isn't a lookalike, it's the same thing. This checks that what the
+// preview shows is what a real post shows, for the same text.
+//
+// Run: bun tools/compose-preview-test.js
+import puppeteer from 'puppeteer-core';
+import { generateMnemonic } from '@scure/bip39';
+import { wordlist } from '@scure/bip39/wordlists/english';
+import { cacheKeyFor } from '../src/wallet.js';
+import { buildHtml } from '../build.js';
+const sleep = (ms) => new Promise((r) => setTimeout(r, ms));
+let ok = true;
+const check = (n, c, d = '') => { console.log(` ${c ? '✓' : '✗'} ${n}${d ? ' — ' + d : ''}`); if (!c) ok = false; };
+
+const html = await buildHtml({ minify: true, pwa: false });
+const server = Bun.serve({ port: 5294, fetch: () => new Response(html, { headers: { 'content-type': 'text/html' } }) });
+const browser = await puppeteer.launch({ executablePath: '/usr/bin/google-chrome', headless: 'new', args: ['--no-sandbox'] });
+const page = await browser.newPage();
+const errs = [];
+page.on('pageerror', (e) => errs.push(String(e)));
+const click = (t) => page.evaluate((x) => { const e = [...document.querySelectorAll('button')].find((n) => n.textContent.trim().toLowerCase().includes(x)); if (e) { e.click(); return true; } return false; }, t);
+const waitText = async (x, ms = 25000) => { for (let i = 0; i < ms / 250; i++) { if ((await page.evaluate(() => document.body.innerText)).toLowerCase().includes(x)) return true; await sleep(250); } return false; };
+const type = (sel, v) => page.evaluate((s, val) => {
+  const e = document.querySelector(s);
+  if (!e) return false;
+  e.focus(); e.value = val;
+  e.dispatchEvent(new Event('input', { bubbles: true }));
+  return true;
+}, sel, v);
+
+const DRAFT = 'look at this https://coinos.io/punks/7.webp and this https://youtu.be/dQw4w9WgXcQ';
+
+try {
+  await page.setViewport({ width: 390, height: 844 });
+  await page.goto('http://localhost:5294/', { waitUntil: 'domcontentloaded' });
+  await page.evaluate(() => localStorage.setItem('btc-wallet-network', 'regtest'));
+  await page.reload({ waitUntil: 'domcontentloaded' });
+  await sleep(400);
+  await click('create a new wallet'); await sleep(500);
+  await click('import existing'); await sleep(400);
+  await page.waitForSelector('textarea');
+  const mn = generateMnemonic(wordlist);
+  await page.type('textarea', mn);
+  await click('open wallet');
+  await waitText('receive', 20000);
+  // a post in the feed, so there is something to reply to
+  const base = cacheKeyFor(mn + '\n');
+  await page.evaluate(([k, n]) => {
+    localStorage.setItem(k + ':follows', JSON.stringify({ tags: [['p', n.pubkey]], c: '', at: Math.floor(Date.now() / 1000) }));
+    localStorage.setItem(k + ':feedNotes', JSON.stringify([n]));
+  }, [base, {
+    id: 'f'.repeat(63) + '1', pubkey: '3bf0c63fcb93463407af97a5e5ee64fa883d107ef9e558472c4eb9aaaefa459d',
+    kind: 1, created_at: Math.floor(Date.now() / 1000) - 60, content: 'a post to answer', tags: [],
+  }]);
+  await page.reload({ waitUntil: 'domcontentloaded' });
+  await waitText('receive', 20000);
+
+  // into the feed, where posts are written
+  await page.evaluate(() => { const b = [...document.querySelectorAll('button')].find((e) => /message/i.test(e.getAttribute('aria-label') || '')); if (b) b.click(); });
+  await sleep(1000);
+  await page.evaluate(() => { const e = [...document.querySelectorAll('.item')].find((n) => /feed/i.test(n.textContent)); if (e) e.click(); });
+  await sleep(2500);
+  const opened = await click('new post');
+  check('the composer opens', opened && !!(await page.$('textarea')));
+
+  await type('textarea', DRAFT);
+  await sleep(400);
+  check('no preview until it is asked for', !(await page.$('.draft-preview')));
+
+  await page.evaluate(() => [...document.querySelectorAll('button')]
+    .find((b) => /preview/i.test(b.getAttribute('aria-label') || ''))?.click());
+  await sleep(2500);
+  const shown = await page.evaluate(() => {
+    const p = document.querySelector('.draft-preview');
+    if (!p) return null;
+    return {
+      imgs: [...p.querySelectorAll('img')].map((i) => i.getAttribute('src') || i.src).filter(Boolean),
+      yt: !!p.querySelector('.yt-embed'),
+      text: p.innerText,
+    };
+  });
+  check('the preview appears', !!shown);
+  check('...with the picture rendered, not its URL', !!shown && shown.imgs.some((u) => /punks\/7\.webp/.test(u)),
+    shown ? shown.imgs.length + ' image(s)' : '');
+  check('...and the YouTube link as a player', !!shown && shown.yt);
+  check('...and the raw URLs are not left lying in the text', !!shown && !shown.text.includes('https://youtu.be/'),
+    shown ? JSON.stringify(shown.text.slice(0, 60)) : '');
+
+  // live: keep typing and the preview follows
+  await type('textarea', DRAFT + ' plus a word');
+  await sleep(900);
+  check('it follows the draft as you type',
+    /plus a word/.test(await page.evaluate(() => (document.querySelector('.draft-preview') || {}).innerText || '')));
+
+  // and it puts itself away
+  await page.evaluate(() => [...document.querySelectorAll('button')]
+    .find((b) => /hide preview/i.test(b.getAttribute('aria-label') || ''))?.click());
+  await sleep(500);
+  check('and it closes again', !(await page.$('.draft-preview')));
+
+  // ---- and the same thing on a reply -------------------------------------
+  await click('cancel');
+  await sleep(400);
+  // open a thread: any post in the feed does
+  const intoThread = await page.evaluate(() => {
+    const r = document.querySelector('.notes-feed > .row');
+    if (!r) return false;
+    r.click();
+    return true;
+  });
+  if (!intoThread) {
+    console.log(' — no post in the feed to reply to, skipping the reply half');
+  } else {
+    await sleep(2500);
+    const box = await page.$('.thread-reply-input');
+    check('a thread has a reply box', !!box);
+    if (box) {
+      await type('.thread-reply-input', 'my answer https://coinos.io/punks/3.webp');
+      await sleep(300);
+      check('a reply has no preview until asked either', !(await page.$('.draft-preview')));
+      await page.evaluate(() => [...document.querySelectorAll('button')]
+        .find((b) => /^preview$/i.test(b.getAttribute('aria-label') || ''))?.click());
+      await sleep(1500);
+      const rp = await page.evaluate(() => {
+        const p = document.querySelector('.draft-preview');
+        return p ? { imgs: p.querySelectorAll('img').length, text: p.innerText } : null;
+      });
+      check('the reply previews the same way', !!rp && rp.imgs > 0,
+        rp ? rp.imgs + ' image(s)' : 'no preview');
+      check('...showing the picture instead of its URL', !!rp && !rp.text.includes('punks/3.webp'),
+        rp ? JSON.stringify(rp.text.slice(0, 50)) : '');
+    }
+  }
+
+  check('no page errors', errs.length === 0, errs.slice(0, 2).join(' | '));
+} finally { await browser.close(); server.stop(true); }
+console.log(ok ? '\n✅ what you see is what they get' : '\n❌ failed');
+process.exit(ok ? 0 : 1);