diff --git a/app/static/js/portfolio_edit.js b/app/static/js/portfolio_edit.js
index c165cc5..627f9d2 100644
--- a/app/static/js/portfolio_edit.js
+++ b/app/static/js/portfolio_edit.js
@@ -40,4 +40,88 @@
 
   editBtn.addEventListener('click', enterEditMode);
   doneBtn.addEventListener('click', exitEditMode);
+
+  // ---- Ticker validation on blur -------------------------------------
+
+  const tickerInput    = document.getElementById('pf-add-ticker');
+  const tickerStatus   = document.getElementById('pf-add-ticker-status');
+  const costCurrencyEl = document.getElementById('pf-add-cost-currency');
+  const submitBtn      = document.getElementById('pf-add-submit');
+  const warningEl      = document.getElementById('pf-add-warning');
+
+  let validated = null; // {symbol, price, currency, as_of} or null
+
+  function setStatus(el, text, kind) {
+    el.textContent = text;
+    el.className = 'pf-add-status' + (kind ? ' pf-add-status--' + kind : '');
+  }
+
+  function updateSubmitState() {
+    const qty  = parseFloat(document.getElementById('pf-add-qty').value);
+    const cost = parseFloat(document.getElementById('pf-add-cost').value);
+    submitBtn.disabled = !(
+      validated && qty > 0 && cost > 0 && isFinite(qty) && isFinite(cost)
+    );
+  }
+
+  function clearDuplicateWarning() {
+    warningEl.hidden = true;
+    warningEl.textContent = '';
+  }
+
+  function showDuplicateWarning(existing) {
+    warningEl.hidden = false;
+    warningEl.textContent =
+      `Already in your portfolio (${existing.qty} shares @ ` +
+      `${existing.avg_cost.toFixed(2)}). Adding will create a duplicate row.`;
+  }
+
+  async function validateTicker() {
+    const raw = tickerInput.value.trim().toUpperCase();
+    if (!raw) {
+      validated = null;
+      setStatus(tickerStatus, '', '');
+      costCurrencyEl.textContent = '';
+      clearDuplicateWarning();
+      updateSubmitState();
+      return;
+    }
+    setStatus(tickerStatus, 'checking…', 'pending');
+    try {
+      const r = await fetch('/api/ticker/validate?symbol=' + encodeURIComponent(raw));
+      if (!r.ok) throw new Error('HTTP ' + r.status);
+      const j = await r.json();
+      if (j.ok) {
+        validated = j;
+        setStatus(
+          tickerStatus,
+          '✓ ' + j.price.toFixed(2) + ' ' + (j.currency || ''),
+          'ok',
+        );
+        costCurrencyEl.textContent = j.currency || '';
+        // Duplicate detection.
+        const pie = window.CassandraPortfolio.loadPie();
+        const existing = pie && (pie.positions || []).find(
+          p => (p.yahoo_ticker || '').toUpperCase() === j.symbol
+        );
+        if (existing) showDuplicateWarning(existing);
+        else clearDuplicateWarning();
+      } else {
+        validated = null;
+        setStatus(tickerStatus, '✗ ' + (j.error || 'not recognised'), 'err');
+        costCurrencyEl.textContent = '';
+        clearDuplicateWarning();
+      }
+    } catch (e) {
+      validated = null;
+      setStatus(tickerStatus, '✗ couldn't validate — try again', 'err');
+      costCurrencyEl.textContent = '';
+      clearDuplicateWarning();
+    }
+    updateSubmitState();
+  }
+
+  tickerInput.addEventListener('blur', validateTicker);
+  document.getElementById('pf-add-qty').addEventListener('input', updateSubmitState);
+  document.getElementById('pf-add-cost').addEventListener('input', updateSubmitState);
 })();