Exit prices on the tick grid, and a refused take-profit flattens

4217.6 − 87 × 0.1 is 4208.900000000001 in floating point. TopstepX refused
that take-profit ("Invalid price. Price is outside allowed range") on two
GC shorts on 2026-10-02, and with no stop on the leg nothing else was
working: both rode far past their target with no exit. ES and NQ never hit
it because 0.25 is exact in binary; GC and CL ticks aren't.

- onTick puts the measured-fee take-profit and every stop on the grid —
  the take-profit away from the entry, the stop toward it — so an averaged
  multi-contract fill between ticks is handled the same way.
- A leg's lone take-profit (no stop, or the fallback after a refused
  bracket) that the broker refuses now flattens the position and benches
  the account for the day, like a refused bracket. An unknown outcome still
  places nothing more.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/trading-logic.ts

@@ -1085,11 +1085,28 @@ export function percentFee(pct: number, price: number, pointValue: number, contr
     return Math.ceil(raw * 100 - 1e-9) / 100;
 }
 
+/**
+ * A price on the tick grid, free of float fuzz. 4217.6 − 87 × 0.1 is
+ * 4208.900000000001 in floating point, and TopstepX refuses a price off the
+ * grid ("Invalid price. Price is outside allowed range") — a GC short rode
+ * with no take-profit on 2026-10-02. An averaged multi-contract fill can sit
+ * between ticks too (by 1/contracts of a tick or more), so an off-grid price
+ * goes `mode`'s way; fuzz within a millionth of a tick is never pushed a
+ * whole tick.
+ */
+export function onTick(price: number, tickSize: number, mode: 'up' | 'down'): number {
+    if (!(tickSize > 0)) return price;
+    const n = price / tickSize;
+    const k = mode === 'up' ? Math.ceil(n - 1e-6) : Math.floor(n + 1e-6);
+    return Math.round(k * tickSize * 1e10) / 1e10;
+}
+
 /**
  * Where to put the take-profit so the leg nets at least `leg` after fees.
  *
  * Measured-fee firms (commissionPct 0): the exit fee is taken to equal the
- * entry fee — the same formula the fire path always used, reproduced exactly.
+ * entry fee — the same formula the fire path always used, reproduced exactly,
+ * then put on the tick grid away from the entry (onTick).
  *
  * Percent-fee firms: the exit fee depends on the exit price itself, so solve
  * for it. With r = pct/100 and k = pointValue × contracts, a long nets
@@ -1116,7 +1133,7 @@ export function takeProfitPlan(o: {
         const grossTarget = o.leg + totalCommission;
         const ticks = Math.ceil(grossTarget / k / o.tickSize);
         return {
-            exitPrice: o.entry + dir * ticks * o.tickSize,
+            exitPrice: onTick(o.entry + dir * ticks * o.tickSize, o.tickSize, o.side === 'Buy' ? 'up' : 'down'),
             ticks,
             entryFee: o.entryCommission,
             exitFee: o.entryCommission,