Add random 1-20 min daily jitter to trading session open

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/auto-trade.ts

@@ -122,11 +122,30 @@ function evaluateAccountForTrade(client: any, acc: { id: number; name: string; a
 
 // ── helpers ───────────────────────────────────────────────────────────────────
 
+// Random 1–20 minute delay added to the session open, picked once per Central
+// calendar day. Re-rolling on every check would move the open boundary between
+// polls, letting a trade slip through a moment the next check would reject.
+const sessionOpenJitter = new Map<string, number>();
+
+function openJitterMinutes(centralDay: string): number {
+    let jitter = sessionOpenJitter.get(centralDay);
+    if (jitter === undefined) {
+        jitter = 1 + Math.floor(Math.random() * 20); // 1–20 inclusive
+        sessionOpenJitter.clear(); // only today's entry is ever needed
+        sessionOpenJitter.set(centralDay, jitter);
+        console.log(`[trading-hours] session open delayed ${jitter} min today`);
+    }
+    return jitter;
+}
+
 /**
  * Returns true when trading is not allowed based on the trading_hours setting.
  *
  * "full_cme"     — Sun 5:05 PM – Fri 2:55 PM Central (5 min buffer on each side)
  * "equity_hours" — 8:35 AM – 2:55 PM Central, Mon–Fri (5 min buffer on each side)
+ *
+ * The open side of each window is pushed back by a random 1–20 minutes per day
+ * (see openJitterMinutes) so sessions never start at the exact same time.
  */
 function isInNoTradeWindow(): boolean {
     const now = new Date();
@@ -143,6 +162,10 @@ function isInNoTradeWindow(): boolean {
         timeZone: 'America/Chicago',
     }).format(now); // "Sun", "Mon", ... "Sat"
     const timeMinutes = hour * 60 + minute; // minutes since midnight
+    const centralDay = new Intl.DateTimeFormat('en-CA', {
+        timeZone: 'America/Chicago',
+    }).format(now); // "2026-09-06"
+    const jitter = openJitterMinutes(centralDay);
 
     const mode = getSetting('trading_hours') ?? 'full_cme';
 
@@ -150,7 +173,7 @@ function isInNoTradeWindow(): boolean {
         // Equity hours: 8:30 AM – 3:00 PM Central with 5 min buffer = 8:35 AM – 2:55 PM
         // Weekdays only
         if (day === 'Sat' || day === 'Sun') return true;
-        const open = 8 * 60 + 35;   // 8:35 AM
+        const open = 8 * 60 + 35 + jitter;   // 8:35 AM + daily jitter
         const close = 14 * 60 + 55;  // 2:55 PM
         return timeMinutes < open || timeMinutes >= close;
     }
@@ -161,8 +184,8 @@ function isInNoTradeWindow(): boolean {
     // Saturday — market closed all day
     if (day === 'Sat') return true;
 
-    // Sunday — market opens at 5:05 PM Central
+    // Sunday — market opens at 5:05 PM Central (+ daily jitter)
-    const cmeOpen = 17 * 60 + 5;  // 5:05 PM
+    const cmeOpen = 17 * 60 + 5 + jitter;  // 5:05 PM + daily jitter
     if (day === 'Sun') return timeMinutes < cmeOpen;
 
     // Friday — stop trading at 2:55 PM Central