it might be better

src/strategy.rs

@@ -33,9 +33,9 @@ impl Strategy {
         portfolio_value: f64,
         available_cash: f64,
         signal: &TradeSignal,
-    ) -> u64 {
+    ) -> f64 {
         if available_cash <= 0.0 {
-            return 0;
+            return 0.0;
         }
 
         let position_value = if signal.atr_pct > MIN_ATR_PCT {
@@ -51,7 +51,9 @@ impl Strategy {
         };
 
         let position_value = position_value.min(available_cash);
-        (position_value / price).floor() as u64
+        // Use fractional shares — Alpaca supports them for paper trading.
+        // Truncate to 4 decimal places to avoid floating point dust.
+        ((position_value / price) * 10000.0).floor() / 10000.0
     }
 
     /// Check if stop-loss, trailing stop, or time exit should trigger.