feat: strategy builder

backend/services/strategy_engine.py

@@ -224,6 +224,7 @@ def price_combo(
         "max_gain": bounded["max_gain"],
         "max_loss": bounded["max_loss"],
         "bounded_risk": bounded["bounded"],
+        "risk_debug": bounded.get("risk_debug"),
         "greeks_now": greeks_at(legs, spot_now, 0, surface_now, r),
         "greeks_scenario": greeks_at(legs, spot_scenario, horizon_days, surface_scenario, r),
         "net_delta_now": delta_now,
@@ -281,6 +282,16 @@ def check_bounded_risk(
     loss_bounded = (lo_edge >= lo_in - tol) and (hi_edge >= hi_in - tol)
     gain_bounded = (lo_edge <= lo_in + tol) and (hi_edge <= hi_in + tol)
 
+    # Diagnostic snapshot of exactly why loss/gain were classified (un)bounded — surfaced
+    # up through price_combo/payoff_curves so the /price router can log it (system_logs)
+    # instead of this being a black box every time "-∞" shows up in the UI.
+    risk_debug = {
+        "eval_days": eval_days, "spot": spot, "entry_ref": round(entry_ref, 2), "tol": round(tol, 4),
+        "lo_tail_price": round(float(tail_grid[0]), 6), "lo_edge_pnl": round(lo_edge, 2), "lo_inner_pnl": round(lo_in, 2),
+        "hi_tail_price": round(float(tail_grid[-1]), 6), "hi_edge_pnl": round(hi_edge, 2), "hi_inner_pnl": round(hi_in, 2),
+        "loss_bounded": loss_bounded, "gain_bounded": gain_bounded,
+    }
+
     # Dense linear sweep across the legs' own strikes — needed even in the fast path (see
     # docstring above), only the final 1-D refinement is reserved for precise=True.
     strikes = [l["strike"] for l in legs]
@@ -294,6 +305,7 @@ def check_bounded_risk(
             "bounded": loss_bounded,
             "max_loss": round(min(combined_values), 2) if loss_bounded else None,
             "max_gain": round(max(combined_values), 2) if gain_bounded else None,
+            "risk_debug": risk_debug,
         }
 
     # Any FIXED grid — however dense — is a different finite sampling of the same
@@ -330,6 +342,7 @@ def check_bounded_risk(
         "bounded": loss_bounded,
         "max_loss": round(refine(False), 2) if loss_bounded else None,
         "max_gain": round(refine(True), 2) if gain_bounded else None,
+        "risk_debug": risk_debug,
     }