diff --git a/src/server/engine/portfolio.test.ts b/src/server/engine/portfolio.test.ts
new file mode 100644
index 0000000..0db11b1
--- /dev/null
+++ b/src/server/engine/portfolio.test.ts
@@ -0,0 +1,29 @@
+import { expect, test } from 'bun:test';
+import { Portfolio, DEFAULT_EXEC } from './portfolio';
+
+test('Entry: Slippage verteuert Fill, Fee reduziert Cash', () => {
+  const p = new Portfolio(1000, DEFAULT_EXEC);
+  p.open('BTC_USDT', 0, 100, 94, 1, 10); // pair, ts, signalPrice, initialStop, qty, riskAmount
+  const pos = p.positions.get('BTC_USDT')!;
+  expect(pos.entryPrice).toBeCloseTo(100.05); // 100 * (1 + 0.0005)
+  // Cash: 1000 − 100.05 − 0.10005 (Fee 0.1%)
+  expect(p.cash).toBeCloseTo(1000 - 100.05 - 0.10005);
+});
+
+test('Exit: PnL netto inkl. beider Fees und Slippage, R-Multiple korrekt', () => {
+  const p = new Portfolio(1000, DEFAULT_EXEC);
+  p.open('BTC_USDT', 0, 100, 94, 1, 10);
+  const trade = p.close('BTC_USDT', 1, 110, 'trailing_stop');
+  // Exit-Fill: 110 * (1−0.0005) = 109.945; Proceeds−Fee = 109.945 * 0.999
+  const cost = 100.05 + 0.10005;
+  const net = 109.945 * 0.999 - cost;
+  expect(trade.pnl).toBeCloseTo(net);
+  expect(trade.r).toBeCloseTo(net / 10);
+  expect(p.positions.size).toBe(0);
+});
+
+test('Equity = Cash + Marktwert offener Positionen', () => {
+  const p = new Portfolio(1000, DEFAULT_EXEC);
+  p.open('BTC_USDT', 0, 100, 94, 2, 10);
+  expect(p.equity(new Map([['BTC_USDT', 105]]))).toBeCloseTo(p.cash + 2 * 105);
+});
diff --git a/src/server/engine/portfolio.ts b/src/server/engine/portfolio.ts
new file mode 100644
index 0000000..2b94fd2
--- /dev/null
+++ b/src/server/engine/portfolio.ts
@@ -0,0 +1,78 @@
+import type { Pair } from '../types';
+
+export interface ExecConfig {
+  feeRate: number;   // 0.001 pro Seite
+  slippage: number;  // 0.0005 pro Seite
+}
+
+export const DEFAULT_EXEC: ExecConfig = { feeRate: 0.001, slippage: 0.0005 };
+
+export interface Position {
+  pair: Pair;
+  qty: number;
+  entryTs: number;
+  entryPrice: number;   // Fill inkl. Slippage
+  entryCost: number;    // qty*fill + Entry-Fee
+  initialStop: number;
+  stop: number;
+  highestHigh: number;
+  riskAmount: number;
+}
+
+export interface ClosedTrade {
+  pair: Pair;
+  entryTs: number;
+  entryPrice: number;
+  exitTs: number;
+  exitPrice: number;
+  qty: number;
+  pnl: number;
+  r: number;
+  exitReason: 'trailing_stop' | 'end_of_data';
+}
+
+export class Portfolio {
+  cash: number;
+  positions = new Map<Pair, Position>();
+  trades: ClosedTrade[] = [];
+
+  constructor(startCapital: number, private exec: ExecConfig) {
+    this.cash = startCapital;
+  }
+
+  open(pair: Pair, ts: number, signalPrice: number, initialStop: number, qty: number, riskAmount: number): void {
+    const fill = signalPrice * (1 + this.exec.slippage);
+    const cost = qty * fill;
+    const fee = cost * this.exec.feeRate;
+    this.cash -= cost + fee;
+    this.positions.set(pair, {
+      pair, qty, entryTs: ts, entryPrice: fill, entryCost: cost + fee,
+      initialStop, stop: initialStop, highestHigh: signalPrice, riskAmount,
+    });
+  }
+
+  close(pair: Pair, ts: number, exitPrice: number, exitReason: ClosedTrade['exitReason']): ClosedTrade {
+    const pos = this.positions.get(pair);
+    if (!pos) throw new Error(`close ohne Position: ${pair}`);
+    const fill = exitPrice * (1 - this.exec.slippage);
+    const proceeds = pos.qty * fill;
+    const fee = proceeds * this.exec.feeRate;
+    this.cash += proceeds - fee;
+    const pnl = proceeds - fee - pos.entryCost;
+    const trade: ClosedTrade = {
+      pair, entryTs: pos.entryTs, entryPrice: pos.entryPrice, exitTs: ts,
+      exitPrice: fill, qty: pos.qty, pnl, r: pnl / pos.riskAmount, exitReason,
+    };
+    this.trades.push(trade);
+    this.positions.delete(pair);
+    return trade;
+  }
+
+  equity(lastClose: Map<Pair, number>): number {
+    let eq = this.cash;
+    for (const pos of this.positions.values()) {
+      eq += pos.qty * (lastClose.get(pos.pair) ?? pos.entryPrice);
+    }
+    return eq;
+  }
+}