diff --git a/design/potidaea/app.html b/design/potidaea/app.html
index 4dd46fb..4a1272c 100644
--- a/design/potidaea/app.html
+++ b/design/potidaea/app.html
@@ -731,6 +731,44 @@
     .ma-ico { width: 32px; height: 32px; }
   }
 
+  /* ============ Swap-sheet error chip ============ */
+  /* Compact error surface on the review sheet: red mark + short code chip +
+   * one-line headline + copy / details toggle. Full text lives in a
+   * collapsible block below so raw broadcast/covenant dumps don't blow up
+   * the sheet vertically. */
+  .wc-sheet-err {
+    font-family: var(--font-mono); font-size: 11px;
+    color: #ff7a8a;
+    background: rgba(255,122,138,.06);
+    border: 1px solid rgba(255,122,138,.28);
+    border-radius: 10px;
+    padding: 10px 12px; margin: 10px 0;
+    line-height: 1.55;
+  }
+  .wc-sheet-err .wc-err-row { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
+  .wc-sheet-err .wc-err-mark { color: #ff7a8a; font-size: 13px; }
+  .wc-sheet-err .wc-err-code {
+    font-family: var(--font-mono); font-size: 9px; letter-spacing: .08em;
+    padding: 2px 6px; border-radius: 4px;
+    color: #ff7a8a; border: 1px solid rgba(255,122,138,.32);
+    background: rgba(255,122,138,.08);
+    white-space: nowrap; flex: none;
+  }
+  .wc-sheet-err .wc-err-head { flex: 1; min-width: 0; color: var(--ink-bright); font-size: 12px; }
+  .wc-sheet-err .wc-err-btn {
+    background: transparent; border: 1px solid rgba(255,122,138,.22);
+    color: rgba(255,122,138,.7); border-radius: 5px;
+    padding: 2px 6px; font-family: var(--font-mono); font-size: 11px; line-height: 1;
+    cursor: pointer; transition: color .15s, border-color .15s;
+    flex: none;
+  }
+  .wc-sheet-err .wc-err-btn:hover { color: #ff7a8a; border-color: rgba(255,122,138,.5); }
+  .wc-sheet-err .wc-err-full {
+    margin-top: 8px; padding-top: 8px; border-top: 1px dashed rgba(255,122,138,.22);
+    font-family: var(--font-mono); font-size: 10.5px; color: var(--ink-soft);
+    max-height: 240px; overflow: auto; word-break: break-word; white-space: pre-wrap;
+  }
+
   /* ============ Tx-receipt mini-buttons (copy / view on explorer) ============ */
   /* Small square action buttons that sit next to a rendered txid across
    * the swap done sheet, wizard genesis done, and publish overlay. */
@@ -752,6 +790,12 @@
    * card, not a half-empty grid behind it. */
   #v-swap.v-swap-welcome-mode .od-layout { display: none; }
   .welcome-overlay { display: flex; align-items: center; justify-content: center; min-height: calc(100vh - 140px); padding: 40px 20px; }
+  /* Explicit [hidden] override — an author `display: flex` rule wins over
+   * the user-agent stylesheet's `[hidden] { display: none }`, so we have
+   * to spell it out or the container keeps eating a full viewport of
+   * vertical space (and shoves the real swap layout to the bottom of the
+   * page) even when overlay.hidden = true. */
+  .welcome-overlay[hidden] { display: none !important; }
   .welcome-card {
     max-width: 640px; width: 100%;
     background: var(--surface-1); border: 1px solid var(--border);
diff --git a/design/potidaea/src/main.ts b/design/potidaea/src/main.ts
index 838d088..12e3eb8 100644
--- a/design/potidaea/src/main.ts
+++ b/design/potidaea/src/main.ts
@@ -788,15 +788,87 @@ function applyOptimisticSwapDelta(kind: 'claim' | 'redeem', amountUnits: bigint,
   try { paintOdAll(); } catch { /* noop */ }
 }
 
+/** Classify a raw error message into a short code + one-line headline the
+ *  user can scan without reading a wall of text. Broadcast errors from
+ *  Bitauth / cashscript often dump the failing tx as a multi-KB hex blob;
+ *  the review sheet is not the place for that. Full text stays in the
+ *  details section for copy-and-paste debugging. */
+function classifySwapError(raw: string): { code: string; headline: string; full: string } {
+  const full = raw.trim();
+  // Pattern → { code, headline extractor }
+  const patterns: Array<{ re: RegExp; code: string; head?: (m: RegExpMatchArray) => string }> = [
+    { re: /^insufficient\s+([a-z0-9]+):.*need\s+(\d+).*have\s+(\d+)/i, code: 'E-INSUFFICIENT',
+      head: (m) => `Not enough ${m[1].toUpperCase()} — need ${m[2]}, have ${m[3]}` },
+    { re: /amount too small|below dust|feeSats\s*>=?/i, code: 'E-DUST',
+      head: () => 'Amount below the covenant’s dust floor' },
+    { re: /change below dust/i, code: 'E-CHANGE-DUST',
+      head: () => 'BCH change would fall below the dust threshold' },
+    { re: /covenant may be draining|no state utxo/i, code: 'E-COVENANT-STATE',
+      head: () => 'Registry covenant state UTXO missing' },
+    { re: /64: bad-txns-inputs-missingorspent|missing inputs/i, code: 'E-STALE-UTXO',
+      head: () => 'Chosen UTXOs already spent — endpoint index is stale' },
+    { re: /min relay fee|not enough fee/i, code: 'E-FEE-LOW',
+      head: () => 'Miner fee too low to relay' },
+    { re: /timeout|connect failed|not connected|electrum:/i, code: 'E-NET',
+      head: () => 'Electrum endpoint unreachable' },
+    { re: /require\s+statement\s+failed|failed\s+at\s+input/i, code: 'E-COVENANT',
+      head: (m) => {
+        const m2 = full.match(/DeviantOpenMintFT\.cash:(\d+)/i);
+        return m2 ? `Covenant require() failed at line ${m2[1]}` : 'Covenant require() failed';
+      } },
+    { re: /leftover dust padding/i, code: 'E-LEFTOVER-DUST',
+      head: () => 'Leftover after redeem would fall below dust' },
+    { re: /^redeem too small/i, code: 'E-REDEEM-SMALL',
+      head: () => 'Redeem amount too small to cover miner fee' },
+  ];
+  for (const p of patterns) {
+    const m = full.match(p.re);
+    if (m) return { code: p.code, headline: p.head ? p.head(m) : m[0], full };
+  }
+  // Fallback — take the first sentence-ish chunk (up to first period, dash,
+  // or 90 chars) as the headline; everything else lives in details.
+  const first = full.split(/[.\n]|—/, 1)[0].trim().slice(0, 90);
+  return { code: 'E-OTHER', headline: first || 'Swap failed', full };
+}
+
 function setSheetError(msg: string): void {
   let el = document.getElementById('wc-sheet-err') as HTMLElement | null;
   if (!el) {
     el = document.createElement('div'); el.id = 'wc-sheet-err';
-    el.style.cssText = 'font-family:var(--font-mono);font-size:11px;color:#ff7a8a;background:rgba(255,122,138,.08);border:1px solid rgba(255,122,138,.28);border-radius:8px;padding:8px 10px;margin:10px 0;';
     const rev = document.getElementById('reviewSheet');
     rev?.insertBefore(el, rev.firstChild);
   }
-  el.textContent = '✗ ' + msg;
+  el.className = 'wc-sheet-err';
+  const { code, headline, full } = classifySwapError(msg);
+  const detailsCollapsed = full.length > 120;
+  el.innerHTML =
+    '<div class="wc-err-row">' +
+      '<span class="wc-err-mark">✗</span>' +
+      '<span class="wc-err-code" title="Error reference">' + escHtml(code) + '</span>' +
+      '<span class="wc-err-head">' + escHtml(headline) + '</span>' +
+      '<button class="wc-err-btn" data-err-copy="1" title="Copy full error text">⧉</button>' +
+      (detailsCollapsed
+        ? '<button class="wc-err-btn" data-err-toggle="1" title="Show / hide full text">⌄</button>'
+        : '') +
+    '</div>' +
+    (detailsCollapsed
+      ? '<div class="wc-err-full" hidden>' + escHtml(full) + '</div>'
+      : (full !== headline ? '<div class="wc-err-full">' + escHtml(full) + '</div>' : ''));
+  el.querySelector<HTMLButtonElement>('[data-err-copy]')?.addEventListener('click', async (ev) => {
+    ev.stopPropagation();
+    try {
+      await navigator.clipboard.writeText('[' + code + '] ' + full);
+      const btn = ev.currentTarget as HTMLButtonElement;
+      const orig = btn.textContent;
+      btn.textContent = '✓';
+      setTimeout(() => { btn.textContent = orig; }, 1000);
+    } catch { /* clipboard blocked — silent */ }
+  });
+  el.querySelector<HTMLButtonElement>('[data-err-toggle]')?.addEventListener('click', (ev) => {
+    ev.stopPropagation();
+    const details = el!.querySelector<HTMLElement>('.wc-err-full');
+    if (details) details.hidden = !details.hidden;
+  });
 }
 
 function wireSwapConfirmInterceptor(): void {