Fix portfolio construction NaN handling

pipeline/portfolio/construct.py

@@ -47,18 +47,16 @@ def continuous_targets(
     """
     alpha = np.asarray(alpha, dtype=np.float64)
     price = np.asarray(price, dtype=np.float64)
-    a = np.where(np.isfinite(alpha), alpha, 0.0)
+    tradable = np.isfinite(price) & (price > 0)
+    a = np.where(np.isfinite(alpha) & tradable, alpha, 0.0)
     gross = np.abs(a).sum()
     if gross <= 0:
         zeros = np.zeros_like(a)
         return zeros, zeros.copy(), zeros.copy()
     w = a / gross
     v_target = booksize * w
-    tradable = np.isfinite(price) & (price > 0)
-    q_target = np.where(tradable, v_target / np.where(tradable, price, 1.0), 0.0)
-    # Names without a tradable price get no target exposure.
-    w = np.where(tradable, w, 0.0)
-    v_target = np.where(tradable, v_target, 0.0)
+    q_target = np.zeros_like(v_target)
+    np.divide(v_target, price, out=q_target, where=tradable)
     return w, v_target, q_target
 
 
@@ -86,7 +84,7 @@ def construct_positions(
     vector. Each date: continuous targets → state-dependent lot rounding →
     two-stage exposure repair. Names absent on a date get weight 0 (which closes
     any stale holding). An empty / zero-gross cross-section carries the book
-    unchanged.
+    unchanged in ``position_shares`` while leaving the target fields at 0.
 
     Args:
         weights_df: Long frame with ``symbol_id, date, weight`` (ALPHA/COMBO).
@@ -136,13 +134,20 @@ def construct_positions(
         )
 
         w, v_target, q_target = continuous_targets(alpha, price, booksize)
-        q_round = round_to_valid_lot(q_target, prev_shares, min_open, increment, odd_full)
-        pos = repair_exposure(
-            q_round, q_target, price, increment, min_open, prev_shares, odd_full,
-            booksize=booksize, net_tol=net_tol, gross_tol=gross_tol,
-        )
+        if np.abs(w).sum() <= 0:
+            logger.warning(
+                "Portfolio '%s': zero-gross target on %s; carrying previous positions.",
+                portfolio_name, d,
+            )
+            pos = prev_shares.copy()
+        else:
+            q_round = round_to_valid_lot(q_target, prev_shares, min_open, increment, odd_full)
+            pos = repair_exposure(
+                q_round, q_target, price, increment, min_open, prev_shares, odd_full,
+                booksize=booksize, net_tol=net_tol, gross_tol=gross_tol,
+            )
 
-        safe_price = np.where(np.isfinite(price), price, 0.0)
+        safe_price = np.where(np.isfinite(price) & (price > 0), price, 0.0)
         blocks.append(pd.DataFrame({
             "symbol_id": symbols,
             "date": d,