feat: strategy builder

backend/routers/strategy_builder.py

@@ -139,9 +139,10 @@ def chain(
     n_expiries: int = Query(3),
     dte_min: Optional[int] = Query(None),
     dte_max: Optional[int] = Query(None),
+    as_of: Optional[str] = Query(None, description="Reconstruct the chain as it stood at/before this date instead of now — e.g. to build legs against the same chain a past Replay window will walk, rather than today's."),
 ):
     try:
-        return get_chain_slice(symbol, horizon_days, n_expiries, dte_min=dte_min, dte_max=dte_max)
+        return get_chain_slice(symbol, horizon_days, n_expiries, dte_min=dte_min, dte_max=dte_max, as_of=as_of)
     except ValueError as e:
         raise HTTPException(status_code=404, detail=str(e))
 
@@ -152,15 +153,18 @@ def presets(
     horizon_days: int = Query(8),
     dte_min: Optional[int] = Query(None),
     dte_max: Optional[int] = Query(None),
+    as_of: Optional[str] = Query(None),
 ):
     """The full strategy catalog (services.backtest_strategies.STRATEGIES) built from the
-    REAL current chain instead of Backtest's synthetic grid — so a preset click here seeds
-    the leg editor with actually-quoted strikes/expiries, ready to price or replay as-is.
-    n_expiries=5 (vs. Strategy Builder's own default of 3) so calendar/diagonal presets,
-    which need two distinct expiries, reliably have a second one to draw from."""
+    REAL chain instead of Backtest's synthetic grid — so a preset click here seeds the leg
+    editor with actually-quoted strikes/expiries, ready to price or replay as-is.
+    n_expiries=20 (vs. Strategy Builder's own default of 3) so calendar/diagonal presets,
+    which need two distinct expiries, reliably have a second one to draw from, and so a
+    wide dte_min/dte_max window (e.g. hunting for a ~30d expiry) isn't silently narrowed
+    back down to whatever's nearest horizon_days."""
     from services.backtest_strategies import STRATEGIES, build_legs
     try:
-        chain_slice = get_chain_slice(symbol, horizon_days, 5, dte_min=dte_min, dte_max=dte_max)
+        chain_slice = get_chain_slice(symbol, horizon_days, 20, dte_min=dte_min, dte_max=dte_max, as_of=as_of)
     except ValueError as e:
         raise HTTPException(status_code=404, detail=str(e))