diff --git a/invest/services.py b/invest/services.py
index b0d8479..34a0ad5 100644
--- a/invest/services.py
+++ b/invest/services.py
@@ -341,23 +341,85 @@ def _build_performance_chart_data() -> Optional[str]:
             if wk not in week_label_date or d > week_label_date[wk]:
                 week_label_date[wk] = d
 
-    # Per-portfolio cumulative % series — each portfolio bases off its own first week
+    # Date range for price lookups (portfolio series + benchmarks share these)
+    earliest_date = week_label_date[all_week_keys[0]]
+    latest_date = week_label_date[all_week_keys[-1]]
+    start_str = (earliest_date - timedelta(days=7)).isoformat()
+    end_str = (latest_date + timedelta(days=5)).isoformat()
+
+    # Pre-fetch the full closing-price history for every currently-held stock in one
+    # yfinance call per ticker (not per week).  This avoids O(stocks × weeks) fetches
+    # and is the same price series used by the dashboard cards.
+    def _fetch_closes(stock_code: str) -> list:
+        """Return [(date, close), …] sorted ascending for stock_code over the chart period."""
+        try:
+            import yfinance as yf
+            hist = yf.Ticker(stock_code).history(start=start_str, end=end_str, auto_adjust=True)
+            if hist.empty:
+                return []
+            closes = []
+            for d, price in hist['Close'].items():
+                date_val = d.date() if hasattr(d, 'date') else d
+                closes.append((date_val, float(price)))
+            return sorted(closes)
+        except Exception as exc:
+            logger.warning("invest: price history failed for %s: %s", stock_code, exc)
+            return []
+
+    def _closest_close(closes: list, target_date) -> Optional[float]:
+        """Most recent closing price on or before target_date."""
+        result = None
+        for d, price in closes:
+            if d <= target_date:
+                result = price
+            else:
+                break
+        return result
+
+    stock_histories: dict = {}
+    for _p in Portfolio.objects.prefetch_related('stocks').all():
+        for _s in _p.stocks.filter(quantity__gt=0):
+            if _s.stock_code not in stock_histories:
+                stock_histories[_s.stock_code] = _fetch_closes(_s.stock_code)
+
+    # Per-portfolio cumulative % series — current holdings × historical prices.
+    #
+    # Using current share counts valued at each historical week's price removes the
+    # distortion caused by transactions (capital injections / withdrawals): a BUY that
+    # injects cash no longer inflates subsequent snapshot totals, and a SELL no longer
+    # deflates them.  The resulting series reflects pure market price performance of the
+    # positions actually held today — identical in methodology to the week-change figures
+    # shown on each portfolio card on the dashboard.
     portfolio_colors = ['#2563EB', '#7C3AED', '#0D9488', '#DB2777', '#EA580C']
     datasets = []
 
-    for idx, portfolio in enumerate(Portfolio.objects.all()):
-        pw = portfolio_weekly.get(portfolio.id, {})
-        if not pw:
+    for idx, portfolio in enumerate(Portfolio.objects.prefetch_related('stocks').all()):
+        current_stocks = list(portfolio.stocks.filter(quantity__gt=0))
+        if not current_stocks:
             continue
-        # base = value in the earliest week available for this portfolio
-        first_week = min(pw.keys())
-        base_val = pw[first_week][1]
+
+        week_totals = []
+        for wk in all_week_keys:
+            label_date = week_label_date[wk]
+            total = 0.0
+            all_priced = True
+            for stock in current_stocks:
+                closes = stock_histories.get(stock.stock_code, [])
+                price = _closest_close(closes, label_date)
+                if price is None:
+                    all_priced = False
+                    break
+                total += price * float(stock.quantity)
+            week_totals.append(total if all_priced else None)
+
+        # Base = first week where every position has a price
+        base_val = next((v for v in week_totals if v), None)
         if not base_val:
             continue
 
         data_pts = [
-            round((pw[wk][1] - base_val) / base_val * 100, 2) if wk in pw else None
-            for wk in all_week_keys
+            round((v - base_val) / base_val * 100, 2) if v is not None else None
+            for v in week_totals
         ]
         color = portfolio_colors[idx % len(portfolio_colors)]
         datasets.append({
@@ -373,11 +435,7 @@ def _build_performance_chart_data() -> Optional[str]:
             'fill': False,
         })
 
-    # Benchmark series — start 7 days before the earliest label date
-    earliest_date = week_label_date[all_week_keys[0]]
-    latest_date = week_label_date[all_week_keys[-1]]
-    start_str = (earliest_date - timedelta(days=7)).isoformat()
-    end_str = (latest_date + timedelta(days=5)).isoformat()
+    # Benchmark series — start_str / end_str already computed above
 
     def _benchmark(ticker: str, label: str, color: str) -> Optional[dict]:
         from .models import BenchmarkPrice