diff --git a/Core/Database/Migrations/CoreMigrations.cs b/Core/Database/Migrations/CoreMigrations.cs
index 23cb85b..40698f1 100644
--- a/Core/Database/Migrations/CoreMigrations.cs
+++ b/Core/Database/Migrations/CoreMigrations.cs
@@ -24,6 +24,7 @@ public class CoreMigrations
         await CreateCoreWorkerLogAsync();
         await CreateCoreTradeHistoryAsync();
         await CreateCoreBudgetAsync();
+        await CreateCorePositionAsync();
         _logger.Info("Core", "Core-Migrationen abgeschlossen.");
     }
 
@@ -76,4 +77,15 @@ public class CoreMigrations
             `updated_at`    DATETIME DEFAULT CURRENT_TIMESTAMP
                             ON UPDATE CURRENT_TIMESTAMP
         ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;");
+
+    private Task CreateCorePositionAsync() => _db.ExecuteAsync(@"
+        CREATE TABLE IF NOT EXISTS `core_position` (
+            `module`     VARCHAR(50)   NOT NULL,
+            `symbol`     VARCHAR(20)   NOT NULL,
+            `quantity`   INT           NOT NULL DEFAULT 0,
+            `avg_price`  DECIMAL(18,4) NOT NULL DEFAULT 0,
+            `updated_at` DATETIME DEFAULT CURRENT_TIMESTAMP
+                         ON UPDATE CURRENT_TIMESTAMP,
+            PRIMARY KEY (`module`, `symbol`)
+        ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;");
 }
diff --git a/Core/Settings/AppSettings.cs b/Core/Settings/AppSettings.cs
index d2b9fe3..6912493 100644
--- a/Core/Settings/AppSettings.cs
+++ b/Core/Settings/AppSettings.cs
@@ -1,4 +1,5 @@
 using System.ComponentModel;
+using IBKRTrader.Core.Trading;
 
 namespace IBKRTrader.Core.Settings;
 
@@ -171,6 +172,48 @@ public class WorkerSettings
     public override string ToString() => "Worker-Konfiguration";
 }
 
+// ─── Trading ─────────────────────────────────────────────────────────────────
+
+[TypeConverter(typeof(ExpandableObjectConverter))]
+public class TradingSettings
+{
+    [Category("Trading")]
+    [DisplayName("Modus")]
+    [Description("Handelsmodus: Paper (Test-Account, Port 4002) oder Live (Port 4001)")]
+    public string Mode { get; set; } = "Paper";
+
+    [Category("Trading")]
+    [DisplayName("Trading aktiv")]
+    [Description("Globaler Hauptschalter. Nur wenn aktiv werden Orders ausgeführt.")]
+    public bool TradingEnabled { get; set; } = false;
+
+    [Category("Trading")]
+    [DisplayName("Max. je Trade (%)")]
+    [Description("Maximaler Nominalwert einer einzelnen Position in % des Kontowerts")]
+    public double MaxTradePercent { get; set; } = 5.0;
+
+    [Category("Trading")]
+    [DisplayName("Max. je Modul (%)")]
+    [Description("Maximaler Gesamt-Nominalwert aller Positionen eines Moduls in % des Kontowerts")]
+    public double MaxPositionPercentPerModule { get; set; } = 20.0;
+
+    [Category("Trading")]
+    [DisplayName("Max. Slippage (%)")]
+    [Description("Maximal erlaubte Abweichung zwischen Limit-Preis und aktuellem Kurs")]
+    public double MaxSlippagePercent { get; set; } = 5.0;
+
+    [Category("Trading")]
+    [DisplayName("Gewinnziel (%)")]
+    [Description("Ziel-Gewinn einer Position in Prozent (für spätere Exit-Logik)")]
+    public double ProfitTargetPercent { get; set; } = 50.0;
+
+    /// <summary>Parst den Modus in das Enum (Fallback: Paper).</summary>
+    public TradingMode ParsedMode =>
+        Enum.TryParse<TradingMode>(Mode, true, out var m) ? m : TradingMode.Paper;
+
+    public override string ToString() => $"{Mode} – {(TradingEnabled ? "aktiv" : "inaktiv")}";
+}
+
 // ─── Root ────────────────────────────────────────────────────────────────────
 
 public class AppSettings
@@ -204,4 +247,9 @@ public class AppSettings
     [DisplayName("Worker-Einstellungen")]
     [Description("Zeitpläne der einzelnen Core-Worker")]
     public WorkerSettings    WorkerSettings { get; set; } = new();
+
+    [Category("Trading")]
+    [DisplayName("Trading")]
+    [Description("Handelsmodus und Risiko-Parameter")]
+    public TradingSettings   Trading        { get; set; } = new();
 }
diff --git a/Core/Trading/ExecutionService.cs b/Core/Trading/ExecutionService.cs
new file mode 100644
index 0000000..6d7c7e4
--- /dev/null
+++ b/Core/Trading/ExecutionService.cs
@@ -0,0 +1,96 @@
+using IBKRTrader.Core.Logging;
+using IBKRTrader.Core.Settings;
+
+namespace IBKRTrader.Core.Trading;
+
+/// <summary>
+/// Führt Modul-Signale aus: globaler Schalter → Kurs → Konto → Risiko → Order → Buchung.
+/// Kennt kein Modul – Module rufen nur <see cref="ExecuteAsync"/> mit ihrem Signal auf.
+/// </summary>
+public sealed class ExecutionService : IExecutionService
+{
+    private readonly IBrokerClient    _broker;
+    private readonly IRiskService     _risk;
+    private readonly IPortfolioService _portfolio;
+    private readonly SettingsService  _settings;
+    private readonly LoggingService   _logger;
+
+    public ExecutionService(
+        IBrokerClient     broker,
+        IRiskService      risk,
+        IPortfolioService portfolio,
+        SettingsService   settings,
+        LoggingService    logger)
+    {
+        _broker    = broker;
+        _risk      = risk;
+        _portfolio = portfolio;
+        _settings  = settings;
+        _logger    = logger;
+    }
+
+    public async Task<ExecutionResult> ExecuteAsync(TradeSignal signal, CancellationToken ct = default)
+    {
+        var trading = _settings.Settings.Trading;
+        var module  = signal.SourceModule;
+
+        // 1. Globaler Hauptschalter
+        if (!trading.TradingEnabled)
+            return Log(module, ExecutionResult.Skip("Trading global deaktiviert."));
+
+        // 2. Kurs
+        var quote = await _broker.GetQuoteAsync(signal.Symbol, ct);
+        if (quote is null || quote.Last <= 0)
+            return Log(module, ExecutionResult.Skip($"Kein Kurs für {signal.Symbol} verfügbar."));
+
+        // 3. Konto + 4. bestehende Exposure/Position
+        var account     = await _broker.GetAccountStateAsync(ct);
+        var exposure    = await _portfolio.GetModuleExposureAsync(module, ct);
+        var existingQty = await _portfolio.GetPositionQuantityAsync(module, signal.Symbol, ct);
+
+        // 5. Risikoprüfung
+        var context = new RiskContext
+        {
+            Price            = quote.Last,
+            NetLiquidation   = account.NetLiquidation,
+            ModuleExposure   = exposure,
+            ExistingQuantity = existingQty
+        };
+        var riskParams = new RiskParameters(
+            (decimal)trading.MaxTradePercent,
+            (decimal)trading.MaxPositionPercentPerModule,
+            (decimal)trading.MaxSlippagePercent);
+        var decision = _risk.Evaluate(signal, context, riskParams);
+        if (!decision.Approved)
+            return Log(module, ExecutionResult.Skip(decision.Reason));
+
+        // 6. Order platzieren
+        var order = new OrderRequest
+        {
+            Symbol     = signal.Symbol,
+            Side       = signal.Side,
+            Quantity   = decision.Quantity,
+            Type       = signal.LimitPrice.HasValue ? OrderType.Limit : OrderType.Market,
+            LimitPrice = signal.LimitPrice
+        };
+
+        var result = await _broker.PlaceOrderAsync(order, ct);
+        if (!result.Success)
+            return Log(module, ExecutionResult.Error(result.Error ?? "Order fehlgeschlagen.", result));
+
+        // 7. Buchung
+        await _portfolio.RecordFillAsync(
+            module, signal.Symbol, signal.Side,
+            result.FilledQuantity, result.AvgFillPrice, result.OrderId, ct);
+
+        return Log(module, ExecutionResult.Execute(result));
+    }
+
+    private ExecutionResult Log(string module, ExecutionResult result)
+    {
+        var text = $"[{result.Action}] {result.Reason}";
+        if (result.Action == "ERROR") _logger.Error(module, text);
+        else                          _logger.Info(module, text);
+        return result;
+    }
+}
diff --git a/Core/Trading/IBrokerClient.cs b/Core/Trading/IBrokerClient.cs
new file mode 100644
index 0000000..982a5c6
--- /dev/null
+++ b/Core/Trading/IBrokerClient.cs
@@ -0,0 +1,17 @@
+namespace IBKRTrader.Core.Trading;
+
+/// <summary>
+/// Broker-Abstraktion (Kurse, Konto, Order-Ausführung).
+/// Externer Seam: in Tests gemockt, produktiv von einem IBKR-Adapter implementiert.
+/// </summary>
+public interface IBrokerClient
+{
+    /// <summary>Aktuelle Kurs-Momentaufnahme oder null, wenn nicht verfügbar.</summary>
+    Task<Quote?> GetQuoteAsync(string symbol, CancellationToken ct = default);
+
+    /// <summary>Kontostand-Momentaufnahme.</summary>
+    Task<AccountState> GetAccountStateAsync(CancellationToken ct = default);
+
+    /// <summary>Platziert eine Order und gibt das Ergebnis zurück.</summary>
+    Task<OrderResult> PlaceOrderAsync(OrderRequest request, CancellationToken ct = default);
+}
diff --git a/Core/Trading/IExecutionService.cs b/Core/Trading/IExecutionService.cs
new file mode 100644
index 0000000..8fd1a1b
--- /dev/null
+++ b/Core/Trading/IExecutionService.cs
@@ -0,0 +1,10 @@
+namespace IBKRTrader.Core.Trading;
+
+/// <summary>
+/// Zentrale Ausführungs-Pipeline. Module übergeben ihre <see cref="TradeSignal"/>e hier;
+/// der Core prüft Risiko, führt aus und verbucht.
+/// </summary>
+public interface IExecutionService
+{
+    Task<ExecutionResult> ExecuteAsync(TradeSignal signal, CancellationToken ct = default);
+}
diff --git a/Core/Trading/IPortfolioService.cs b/Core/Trading/IPortfolioService.cs
new file mode 100644
index 0000000..f1544c4
--- /dev/null
+++ b/Core/Trading/IPortfolioService.cs
@@ -0,0 +1,22 @@
+namespace IBKRTrader.Core.Trading;
+
+/// <summary>
+/// Buchführung über offene Positionen und Ausführungen (core_position, core_trade_history).
+/// Externer Seam gegenüber der Datenbank: in Tests gemockt.
+/// </summary>
+public interface IPortfolioService
+{
+    /// <summary>Summe des offenen Nominalwerts eines Moduls.</summary>
+    Task<decimal> GetModuleExposureAsync(string module, CancellationToken ct = default);
+
+    /// <summary>Gehaltene Stückzahl eines Moduls für ein Symbol (0, wenn keine Position).</summary>
+    Task<int> GetPositionQuantityAsync(string module, string symbol, CancellationToken ct = default);
+
+    /// <summary>Verbucht einen Fill: aktualisiert Position, Budget und Trade-Historie.</summary>
+    Task RecordFillAsync(
+        string module, string symbol, TradeSide side,
+        int quantity, decimal price, string? orderId, CancellationToken ct = default);
+
+    /// <summary>Alle offenen Positionen eines Moduls.</summary>
+    Task<IReadOnlyList<Position>> GetPositionsAsync(string module, CancellationToken ct = default);
+}
diff --git a/Core/Trading/IRiskService.cs b/Core/Trading/IRiskService.cs
new file mode 100644
index 0000000..458cb12
--- /dev/null
+++ b/Core/Trading/IRiskService.cs
@@ -0,0 +1,7 @@
+namespace IBKRTrader.Core.Trading;
+
+/// <summary>Bewertet ein Signal gegen die Risiko-Parameter und liefert die Stückzahl.</summary>
+public interface IRiskService
+{
+    RiskDecision Evaluate(TradeSignal signal, RiskContext context, RiskParameters risk);
+}
diff --git a/Core/Trading/NullBrokerClient.cs b/Core/Trading/NullBrokerClient.cs
new file mode 100644
index 0000000..f9ff32c
--- /dev/null
+++ b/Core/Trading/NullBrokerClient.cs
@@ -0,0 +1,29 @@
+using IBKRTrader.Core.Logging;
+
+namespace IBKRTrader.Core.Trading;
+
+/// <summary>
+/// Sicherer Standard-Broker: handelt NIEMALS.
+/// Wird registriert, bis der echte IBKR-Adapter angebunden und gegen den
+/// Paper-Gateway verifiziert ist. So kann keine Order versehentlich rausgehen.
+/// </summary>
+public sealed class NullBrokerClient : IBrokerClient
+{
+    private readonly LoggingService _logger;
+
+    public NullBrokerClient(LoggingService logger) => _logger = logger;
+
+    public Task<Quote?> GetQuoteAsync(string symbol, CancellationToken ct = default)
+        => Task.FromResult<Quote?>(null);
+
+    public Task<AccountState> GetAccountStateAsync(CancellationToken ct = default)
+        => Task.FromResult(new AccountState(0m, 0m));
+
+    public Task<OrderResult> PlaceOrderAsync(OrderRequest request, CancellationToken ct = default)
+    {
+        _logger.Warn("Core",
+            $"NullBrokerClient: Order NICHT ausgeführt ({request.Side} {request.Quantity}x {request.Symbol}) " +
+            "– echter IBKR-Broker noch nicht angebunden.");
+        return Task.FromResult(OrderResult.Fail("Broker nicht angebunden (NullBrokerClient)."));
+    }
+}
diff --git a/Core/Trading/PortfolioService.cs b/Core/Trading/PortfolioService.cs
new file mode 100644
index 0000000..12f610c
--- /dev/null
+++ b/Core/Trading/PortfolioService.cs
@@ -0,0 +1,110 @@
+using IBKRTrader.Core.Budget;
+using IBKRTrader.Core.Database;
+using IBKRTrader.Core.Logging;
+
+namespace IBKRTrader.Core.Trading;
+
+/// <summary>
+/// DB-gestützte Buchführung über offene Positionen (core_position),
+/// Trade-Historie (core_trade_history) und Budget (core_budget).
+/// </summary>
+public sealed class PortfolioService : IPortfolioService
+{
+    private readonly DatabaseService     _db;
+    private readonly TradeHistoryService _history;
+    private readonly BudgetService       _budget;
+    private readonly LoggingService      _logger;
+
+    public PortfolioService(
+        DatabaseService db,
+        TradeHistoryService history,
+        BudgetService budget,
+        LoggingService logger)
+    {
+        _db      = db;
+        _history = history;
+        _budget  = budget;
+        _logger  = logger;
+    }
+
+    private sealed class PosDto
+    {
+        public int     Quantity { get; set; }
+        public decimal AvgPrice { get; set; }
+    }
+
+    public async Task<decimal> GetModuleExposureAsync(string module, CancellationToken ct = default)
+    {
+        var sum = await _db.ExecuteScalarAsync<decimal?>(
+            "SELECT SUM(quantity * avg_price) FROM `core_position` WHERE module = @module",
+            new { module });
+        return sum ?? 0m;
+    }
+
+    public async Task<int> GetPositionQuantityAsync(string module, string symbol, CancellationToken ct = default)
+    {
+        var row = await _db.QueryFirstOrDefaultAsync<PosDto>(
+            "SELECT quantity AS Quantity, avg_price AS AvgPrice FROM `core_position` " +
+            "WHERE module = @module AND symbol = @symbol",
+            new { module, symbol });
+        return row?.Quantity ?? 0;
+    }
+
+    public async Task<IReadOnlyList<Position>> GetPositionsAsync(string module, CancellationToken ct = default)
+    {
+        var rows = await _db.QueryAsync<Position>(
+            "SELECT module AS Module, symbol AS Symbol, quantity AS Quantity, avg_price AS AvgPrice " +
+            "FROM `core_position` WHERE module = @module AND quantity > 0",
+            new { module });
+        return rows.ToList();
+    }
+
+    public async Task RecordFillAsync(
+        string module, string symbol, TradeSide side,
+        int quantity, decimal price, string? orderId, CancellationToken ct = default)
+    {
+        if (quantity <= 0) return;
+
+        var action = side == TradeSide.Buy ? "BUY" : "SELL";
+        await _history.RecordTradeAsync(module, symbol, action, quantity, price, orderId);
+
+        var current = await _db.QueryFirstOrDefaultAsync<PosDto>(
+            "SELECT quantity AS Quantity, avg_price AS AvgPrice FROM `core_position` " +
+            "WHERE module = @module AND symbol = @symbol",
+            new { module, symbol });
+
+        var oldQty = current?.Quantity ?? 0;
+        var oldAvg = current?.AvgPrice ?? 0m;
+
+        if (side == TradeSide.Buy)
+        {
+            var newQty = oldQty + quantity;
+            var newAvg = oldQty > 0 ? (oldQty * oldAvg + quantity * price) / newQty : price;
+            await UpsertPositionAsync(module, symbol, newQty, newAvg);
+            await _budget.ReserveBudgetAsync(module, quantity * price);
+        }
+        else
+        {
+            var newQty = oldQty - quantity;
+            if (newQty <= 0)
+                await DeletePositionAsync(module, symbol);
+            else
+                await UpsertPositionAsync(module, symbol, newQty, oldAvg);
+            await _budget.ReleaseBudgetAsync(module, quantity * price);
+        }
+
+        _logger.Info(module, $"Position gebucht: {action} {quantity}x {symbol} @ {price:F2}");
+    }
+
+    private Task UpsertPositionAsync(string module, string symbol, int quantity, decimal avgPrice) =>
+        _db.ExecuteAsync(@"
+            INSERT INTO `core_position` (module, symbol, quantity, avg_price)
+            VALUES (@module, @symbol, @quantity, @avgPrice)
+            ON DUPLICATE KEY UPDATE quantity = @quantity, avg_price = @avgPrice",
+            new { module, symbol, quantity, avgPrice });
+
+    private Task DeletePositionAsync(string module, string symbol) =>
+        _db.ExecuteAsync(
+            "DELETE FROM `core_position` WHERE module = @module AND symbol = @symbol",
+            new { module, symbol });
+}
diff --git a/Core/Trading/RiskService.cs b/Core/Trading/RiskService.cs
new file mode 100644
index 0000000..cc42b3e
--- /dev/null
+++ b/Core/Trading/RiskService.cs
@@ -0,0 +1,74 @@
+namespace IBKRTrader.Core.Trading;
+
+/// <summary>
+/// Reine Risiko-/Sizing-Logik – keine externen Abhängigkeiten, vollständig unit-testbar.
+///
+/// Regeln:
+///  - Kauf: Nominalwert = min(Wunsch, Kontowert × MaxTradePercent); Stückzahl = floor(Nominal / Kurs).
+///          Ablehnung bei ungültigem Kurs, Stückzahl &lt; 1, Überschreitung des Modul-Limits
+///          oder zu hoher Slippage (bei Limit-Order).
+///  - Verkauf: schließt die vorhandene Position (Stückzahl = gehaltene Menge);
+///             Ablehnung, wenn keine Position vorhanden ist.
+/// </summary>
+public sealed class RiskService : IRiskService
+{
+    public RiskDecision Evaluate(TradeSignal signal, RiskContext context, RiskParameters risk)
+    {
+        if (context.Price <= 0)
+            return RiskDecision.Reject("Ungültiger Kurs (<= 0).");
+
+        if (SlippageTooHigh(signal, context, risk, out var slipReason))
+            return RiskDecision.Reject(slipReason);
+
+        return signal.Side == TradeSide.Sell
+            ? EvaluateSell(context)
+            : EvaluateBuy(context, signal, risk);
+    }
+
+    private static RiskDecision EvaluateSell(RiskContext context)
+    {
+        if (context.ExistingQuantity <= 0)
+            return RiskDecision.Reject("Keine Position zum Verkauf vorhanden.");
+
+        return RiskDecision.Approve(context.ExistingQuantity, "Verkauf schließt Position.");
+    }
+
+    private static RiskDecision EvaluateBuy(RiskContext context, TradeSignal signal, RiskParameters risk)
+    {
+        if (context.NetLiquidation <= 0)
+            return RiskDecision.Reject("Kontowert unbekannt oder 0.");
+
+        var maxNotional = context.NetLiquidation * (risk.MaxTradePercent / 100m);
+        var notional    = signal.SuggestedNotional is { } wish && wish > 0
+            ? Math.Min(wish, maxNotional)
+            : maxNotional;
+
+        var quantity = (int)Math.Floor(notional / context.Price);
+        if (quantity < 1)
+            return RiskDecision.Reject("Positionsgröße < 1 Stück bei aktuellem Kurs/Budget.");
+
+        var projectedExposure = context.ModuleExposure + quantity * context.Price;
+        var moduleLimit       = context.NetLiquidation * (risk.MaxPositionPercentPerModule / 100m);
+        if (projectedExposure > moduleLimit)
+            return RiskDecision.Reject(
+                $"Modul-Limit überschritten ({projectedExposure:F0} > {moduleLimit:F0}).");
+
+        return RiskDecision.Approve(quantity, $"{quantity} Stück freigegeben.");
+    }
+
+    private static bool SlippageTooHigh(
+        TradeSignal signal, RiskContext context, RiskParameters risk, out string reason)
+    {
+        reason = "";
+        if (signal.LimitPrice is not { } limit || limit <= 0)
+            return false;
+
+        var deviationPct = Math.Abs(context.Price - limit) / limit * 100m;
+        if (deviationPct > risk.MaxSlippagePercent)
+        {
+            reason = $"Slippage zu hoch ({deviationPct:F1}% > {risk.MaxSlippagePercent:F1}%).";
+            return true;
+        }
+        return false;
+    }
+}
diff --git a/Core/Trading/TradingModels.cs b/Core/Trading/TradingModels.cs
new file mode 100644
index 0000000..044fb86
--- /dev/null
+++ b/Core/Trading/TradingModels.cs
@@ -0,0 +1,124 @@
+namespace IBKRTrader.Core.Trading;
+
+/// <summary>Kauf oder Verkauf.</summary>
+public enum TradeSide { Buy, Sell }
+
+/// <summary>Order-Typ.</summary>
+public enum OrderType { Market, Limit }
+
+/// <summary>Handelsmodus – Paper-Account (Test) oder Live.</summary>
+public enum TradingMode { Paper, Live }
+
+/// <summary>
+/// Signal, das ein Modul an den <see cref="IExecutionService"/> übergibt.
+/// Das Modul liefert nur die Absicht – Sizing, Risiko und Ausführung macht der Core.
+/// </summary>
+public sealed record TradeSignal
+{
+    /// <summary>Ticker-Symbol (z. B. "AAPL").</summary>
+    public required string Symbol { get; init; }
+
+    /// <summary>Kauf oder Verkauf.</summary>
+    public required TradeSide Side { get; init; }
+
+    /// <summary>Kürzel des auslösenden Moduls (z. B. "CT").</summary>
+    public required string SourceModule { get; init; }
+
+    /// <summary>Begründung des Signals (für Logging/Buchführung).</summary>
+    public string Reason { get; init; } = "";
+
+    /// <summary>Optionaler Limit-Preis. null = Market-Order.</summary>
+    public decimal? LimitPrice { get; init; }
+
+    /// <summary>Optionaler Nominalwert-Wunsch; sonst greift das Risiko-Sizing.</summary>
+    public decimal? SuggestedNotional { get; init; }
+}
+
+/// <summary>Konkrete Order-Anforderung an den Broker.</summary>
+public sealed record OrderRequest
+{
+    public required string    Symbol     { get; init; }
+    public required TradeSide Side       { get; init; }
+    public required int       Quantity   { get; init; }
+    public required OrderType Type       { get; init; }
+    public decimal?           LimitPrice { get; init; }
+}
+
+/// <summary>Ergebnis einer Order-Platzierung.</summary>
+public sealed record OrderResult
+{
+    public bool     Success        { get; init; }
+    public string?  OrderId        { get; init; }
+    public int      FilledQuantity { get; init; }
+    public decimal  AvgFillPrice   { get; init; }
+    public string?  Error          { get; init; }
+
+    public static OrderResult Filled(string orderId, int qty, decimal price) =>
+        new() { Success = true, OrderId = orderId, FilledQuantity = qty, AvgFillPrice = price };
+
+    public static OrderResult Fail(string error) =>
+        new() { Success = false, Error = error };
+}
+
+/// <summary>Momentaufnahme eines Kurses.</summary>
+public sealed record Quote(string Symbol, decimal Last, decimal Bid, decimal Ask);
+
+/// <summary>Kontostand-Momentaufnahme des Brokers.</summary>
+public sealed record AccountState(decimal NetLiquidation, decimal AvailableFunds);
+
+/// <summary>Offene Position eines Moduls.</summary>
+public sealed record Position(string Module, string Symbol, int Quantity, decimal AvgPrice)
+{
+    public decimal Notional => Quantity * AvgPrice;
+}
+
+/// <summary>Kontext für die Risikobewertung eines Signals.</summary>
+public sealed record RiskContext
+{
+    /// <summary>Aktueller Kurs des Symbols.</summary>
+    public required decimal Price { get; init; }
+
+    /// <summary>Netto-Liquidationswert des Kontos.</summary>
+    public required decimal NetLiquidation { get; init; }
+
+    /// <summary>Aktuell vom Modul gehaltener Nominalwert (Summe offener Positionen).</summary>
+    public decimal ModuleExposure { get; init; }
+
+    /// <summary>Bereits gehaltene Stückzahl für das Signal-Symbol.</summary>
+    public int ExistingQuantity { get; init; }
+}
+
+/// <summary>Aus den Settings abgeleitete Risiko-Parameter.</summary>
+public sealed record RiskParameters(
+    decimal MaxTradePercent,
+    decimal MaxPositionPercentPerModule,
+    decimal MaxSlippagePercent);
+
+/// <summary>Entscheidung der Risikoprüfung.</summary>
+public sealed record RiskDecision
+{
+    public bool    Approved { get; init; }
+    public int     Quantity { get; init; }
+    public string  Reason   { get; init; } = "";
+
+    public static RiskDecision Reject(string reason) =>
+        new() { Approved = false, Quantity = 0, Reason = reason };
+
+    public static RiskDecision Approve(int quantity, string reason = "OK") =>
+        new() { Approved = true, Quantity = quantity, Reason = reason };
+}
+
+/// <summary>Ergebnis einer Signal-Ausführung durch den <see cref="IExecutionService"/>.</summary>
+public sealed record ExecutionResult
+{
+    /// <summary>"EXECUTE", "SKIP" oder "ERROR".</summary>
+    public required string Action { get; init; }
+    public string       Reason { get; init; } = "";
+    public OrderResult? Order  { get; init; }
+
+    public bool Executed => Action == "EXECUTE";
+
+    public static ExecutionResult Skip(string reason)  => new() { Action = "SKIP",    Reason = reason };
+    public static ExecutionResult Error(string reason, OrderResult? order = null) => new() { Action = "ERROR", Reason = reason, Order = order };
+    public static ExecutionResult Execute(OrderResult order) => new() { Action = "EXECUTE", Reason = "OK", Order = order };
+}
diff --git a/IBKRTrader.Tests/Trading/ExecutionServiceTests.cs b/IBKRTrader.Tests/Trading/ExecutionServiceTests.cs
new file mode 100644
index 0000000..657361c
--- /dev/null
+++ b/IBKRTrader.Tests/Trading/ExecutionServiceTests.cs
@@ -0,0 +1,125 @@
+using FluentAssertions;
+using IBKRTrader.Core.Logging;
+using IBKRTrader.Core.Settings;
+using IBKRTrader.Core.Trading;
+using NSubstitute;
+
+namespace IBKRTrader.Tests.Trading;
+
+[Trait("cat", "unit")]
+public class ExecutionServiceTests
+{
+    private readonly IBrokerClient     _broker    = Substitute.For<IBrokerClient>();
+    private readonly IRiskService      _risk      = Substitute.For<IRiskService>();
+    private readonly IPortfolioService _portfolio = Substitute.For<IPortfolioService>();
+    private readonly SettingsService   _settings  = new();
+
+    private ExecutionService CreateSut() =>
+        new(_broker, _risk, _portfolio, _settings, new LoggingService());
+
+    private static readonly TradeSignal BuySignal = new()
+    {
+        Symbol = "AAPL", Side = TradeSide.Buy, SourceModule = "CT"
+    };
+
+    private void EnableTrading() => _settings.Settings.Trading.TradingEnabled = true;
+
+    private void ArrangeHappyPath()
+    {
+        EnableTrading();
+        _broker.GetQuoteAsync(Arg.Any<string>(), Arg.Any<CancellationToken>())
+               .Returns(Task.FromResult<Quote?>(new Quote("AAPL", 100m, 99m, 101m)));
+        _broker.GetAccountStateAsync(Arg.Any<CancellationToken>())
+               .Returns(Task.FromResult(new AccountState(10_000m, 10_000m)));
+        _portfolio.GetModuleExposureAsync(Arg.Any<string>(), Arg.Any<CancellationToken>())
+                  .Returns(Task.FromResult(0m));
+        _portfolio.GetPositionQuantityAsync(Arg.Any<string>(), Arg.Any<string>(), Arg.Any<CancellationToken>())
+                  .Returns(Task.FromResult(0));
+        _risk.Evaluate(Arg.Any<TradeSignal>(), Arg.Any<RiskContext>(), Arg.Any<RiskParameters>())
+             .Returns(RiskDecision.Approve(5));
+        _broker.PlaceOrderAsync(Arg.Any<OrderRequest>(), Arg.Any<CancellationToken>())
+               .Returns(Task.FromResult(OrderResult.Filled("O1", 5, 100m)));
+    }
+
+    [Fact]
+    public async Task TradingDisabled_Skips_WithoutTouchingBroker()
+    {
+        // TradingEnabled ist standardmäßig false
+        var result = await CreateSut().ExecuteAsync(BuySignal);
+
+        result.Action.Should().Be("SKIP");
+        await _broker.DidNotReceive().PlaceOrderAsync(Arg.Any<OrderRequest>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task NoQuote_Skips()
+    {
+        EnableTrading();
+        _broker.GetQuoteAsync(Arg.Any<string>(), Arg.Any<CancellationToken>())
+               .Returns(Task.FromResult<Quote?>(null));
+
+        var result = await CreateSut().ExecuteAsync(BuySignal);
+
+        result.Action.Should().Be("SKIP");
+        await _broker.DidNotReceive().PlaceOrderAsync(Arg.Any<OrderRequest>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task RiskRejects_Skips_WithReason()
+    {
+        EnableTrading();
+        _broker.GetQuoteAsync(Arg.Any<string>(), Arg.Any<CancellationToken>())
+               .Returns(Task.FromResult<Quote?>(new Quote("AAPL", 100m, 99m, 101m)));
+        _broker.GetAccountStateAsync(Arg.Any<CancellationToken>())
+               .Returns(Task.FromResult(new AccountState(10_000m, 10_000m)));
+        _risk.Evaluate(Arg.Any<TradeSignal>(), Arg.Any<RiskContext>(), Arg.Any<RiskParameters>())
+             .Returns(RiskDecision.Reject("Modul-Limit überschritten."));
+
+        var result = await CreateSut().ExecuteAsync(BuySignal);
+
+        result.Action.Should().Be("SKIP");
+        result.Reason.Should().Contain("Modul-Limit");
+        await _broker.DidNotReceive().PlaceOrderAsync(Arg.Any<OrderRequest>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task HappyPath_PlacesOrder_AndBooksFill()
+    {
+        ArrangeHappyPath();
+
+        var result = await CreateSut().ExecuteAsync(BuySignal);
+
+        result.Executed.Should().BeTrue();
+        result.Order!.OrderId.Should().Be("O1");
+        await _portfolio.Received(1).RecordFillAsync(
+            "CT", "AAPL", TradeSide.Buy, 5, 100m, "O1", Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task HappyPath_MarketOrder_WhenNoLimitPrice()
+    {
+        ArrangeHappyPath();
+
+        await CreateSut().ExecuteAsync(BuySignal);
+
+        await _broker.Received(1).PlaceOrderAsync(
+            Arg.Is<OrderRequest>(o => o.Type == OrderType.Market && o.Quantity == 5),
+            Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task OrderFails_ReturnsError_AndDoesNotBook()
+    {
+        ArrangeHappyPath();
+        _broker.PlaceOrderAsync(Arg.Any<OrderRequest>(), Arg.Any<CancellationToken>())
+               .Returns(Task.FromResult(OrderResult.Fail("Broker abgelehnt")));
+
+        var result = await CreateSut().ExecuteAsync(BuySignal);
+
+        result.Action.Should().Be("ERROR");
+        result.Reason.Should().Contain("Broker abgelehnt");
+        await _portfolio.DidNotReceive().RecordFillAsync(
+            Arg.Any<string>(), Arg.Any<string>(), Arg.Any<TradeSide>(),
+            Arg.Any<int>(), Arg.Any<decimal>(), Arg.Any<string>(), Arg.Any<CancellationToken>());
+    }
+}
diff --git a/IBKRTrader.Tests/Trading/RiskServiceTests.cs b/IBKRTrader.Tests/Trading/RiskServiceTests.cs
new file mode 100644
index 0000000..9d82e2f
--- /dev/null
+++ b/IBKRTrader.Tests/Trading/RiskServiceTests.cs
@@ -0,0 +1,142 @@
+using FluentAssertions;
+using IBKRTrader.Core.Trading;
+
+namespace IBKRTrader.Tests.Trading;
+
+[Trait("cat", "unit")]
+public class RiskServiceTests
+{
+    private readonly RiskService _risk = new();
+
+    // MaxTrade 5 %, MaxModul 20 %, MaxSlippage 5 %
+    private static readonly RiskParameters DefaultParams = new(5m, 20m, 5m);
+
+    private static TradeSignal Buy(decimal? limit = null, decimal? notional = null) => new()
+    {
+        Symbol = "AAPL", Side = TradeSide.Buy, SourceModule = "CT",
+        LimitPrice = limit, SuggestedNotional = notional
+    };
+
+    private static TradeSignal Sell() => new()
+    {
+        Symbol = "AAPL", Side = TradeSide.Sell, SourceModule = "CT"
+    };
+
+    [Fact]
+    public void Buy_SizesByMaxTradePercent()
+    {
+        // NetLiq 10.000 × 5 % = 500 max Nominal; Kurs 100 → 5 Stück
+        var ctx = new RiskContext { Price = 100m, NetLiquidation = 10_000m };
+
+        var d = _risk.Evaluate(Buy(), ctx, DefaultParams);
+
+        d.Approved.Should().BeTrue();
+        d.Quantity.Should().Be(5);
+    }
+
+    [Fact]
+    public void Buy_UsesSuggestedNotional_WhenSmallerThanMax()
+    {
+        // Wunsch 200 < Max 500; Kurs 100 → 2 Stück
+        var ctx = new RiskContext { Price = 100m, NetLiquidation = 10_000m };
+
+        var d = _risk.Evaluate(Buy(notional: 200m), ctx, DefaultParams);
+
+        d.Quantity.Should().Be(2);
+    }
+
+    [Fact]
+    public void Buy_InvalidPrice_Rejected()
+    {
+        var ctx = new RiskContext { Price = 0m, NetLiquidation = 10_000m };
+
+        _risk.Evaluate(Buy(), ctx, DefaultParams).Approved.Should().BeFalse();
+    }
+
+    [Fact]
+    public void Buy_ZeroAccount_Rejected()
+    {
+        var ctx = new RiskContext { Price = 100m, NetLiquidation = 0m };
+
+        _risk.Evaluate(Buy(), ctx, DefaultParams).Approved.Should().BeFalse();
+    }
+
+    [Fact]
+    public void Buy_QuantityBelowOne_Rejected()
+    {
+        // NetLiq 100 × 5 % = 5 max Nominal; Kurs 100 → 0 Stück
+        var ctx = new RiskContext { Price = 100m, NetLiquidation = 100m };
+
+        var d = _risk.Evaluate(Buy(), ctx, DefaultParams);
+
+        d.Approved.Should().BeFalse();
+        d.Reason.Should().Contain("< 1");
+    }
+
+    [Fact]
+    public void Buy_ExceedsModuleLimit_Rejected()
+    {
+        // MaxTrade 50 % → 5.000 Nominal, Kurs 100 → 50 Stück = 5.000
+        // Modul-Limit 20 % × 10.000 = 2.000 → abgelehnt
+        var ctx = new RiskContext { Price = 100m, NetLiquidation = 10_000m };
+        var pars = new RiskParameters(50m, 20m, 5m);
+
+        var d = _risk.Evaluate(Buy(), ctx, pars);
+
+        d.Approved.Should().BeFalse();
+        d.Reason.Should().Contain("Modul-Limit");
+    }
+
+    [Fact]
+    public void Buy_ExistingExposureCountsTowardModuleLimit()
+    {
+        // Kurs 100, Max 5 % → 5 Stück (500). Bereits 1.700 Exposure.
+        // Projektiert 2.200 > Limit 2.000 → abgelehnt.
+        var ctx = new RiskContext { Price = 100m, NetLiquidation = 10_000m, ModuleExposure = 1_700m };
+
+        _risk.Evaluate(Buy(), ctx, DefaultParams).Approved.Should().BeFalse();
+    }
+
+    [Fact]
+    public void Buy_LimitOrder_SlippageTooHigh_Rejected()
+    {
+        // Limit 100, Kurs 110 → 10 % > 5 %
+        var ctx = new RiskContext { Price = 110m, NetLiquidation = 10_000m };
+
+        var d = _risk.Evaluate(Buy(limit: 100m), ctx, DefaultParams);
+
+        d.Approved.Should().BeFalse();
+        d.Reason.Should().Contain("Slippage");
+    }
+
+    [Fact]
+    public void Buy_LimitOrder_SlippageWithinTolerance_Approved()
+    {
+        // Limit 100, Kurs 104 → 4 % < 5 %
+        var ctx = new RiskContext { Price = 104m, NetLiquidation = 10_000m };
+
+        _risk.Evaluate(Buy(limit: 100m), ctx, DefaultParams).Approved.Should().BeTrue();
+    }
+
+    [Fact]
+    public void Sell_WithPosition_ClosesQuantity()
+    {
+        var ctx = new RiskContext { Price = 100m, NetLiquidation = 10_000m, ExistingQuantity = 12 };
+
+        var d = _risk.Evaluate(Sell(), ctx, DefaultParams);
+
+        d.Approved.Should().BeTrue();
+        d.Quantity.Should().Be(12);
+    }
+
+    [Fact]
+    public void Sell_WithoutPosition_Rejected()
+    {
+        var ctx = new RiskContext { Price = 100m, NetLiquidation = 10_000m, ExistingQuantity = 0 };
+
+        var d = _risk.Evaluate(Sell(), ctx, DefaultParams);
+
+        d.Approved.Should().BeFalse();
+        d.Reason.Should().Contain("Keine Position");
+    }
+}
diff --git a/Program.cs b/Program.cs
index 30dd263..b0047dd 100644
--- a/Program.cs
+++ b/Program.cs
@@ -47,6 +47,14 @@ internal static class Program
         services.AddSingleton<TradeHistoryService>();
         services.AddSingleton<AIModelService>();
 
+        // Core: Trading-Kern
+        services.AddSingleton<IRiskService, RiskService>();
+        services.AddSingleton<IPortfolioService, PortfolioService>();
+        services.AddSingleton<IExecutionService, ExecutionService>();
+        // Sicherer Standard-Broker: handelt nicht, bis der echte IBKR-Adapter
+        // angebunden und gegen den Paper-Gateway verifiziert ist.
+        services.AddSingleton<IBrokerClient, NullBrokerClient>();
+
         // Core: Built-In Worker
         services.AddSingleton<BackupWorker>();
         services.AddSingleton<WebserverService>();
diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index 7c52fb8..392fb1f 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -117,14 +117,15 @@ WinForms selbst wird **nicht** unit-getestet – Logik in Services/Manager halte
 - [x] `WindowManager` in DI; Launcher schließt Modul-Fenster beim Beenden
 - [x] Tests: `WindowManager` (6) → **21/21 grün**; Launcher-Start verifiziert
 
-### Phase 3 – Trading-Kern (Core)
-- [ ] `Core/Trading/IIbkrClient.cs` (+ Adapter auf `IBKRGatewayService`)
-- [ ] `Core/Trading/IOrderService.cs` + Implementierung (Market/Limit, Paper+Live)
-- [ ] `Core/Trading/PortfolioService.cs` + Migrationen `core_position`, `core_trade`, `core_account_snapshot`
-- [ ] `Core/Trading/RiskService.cs` (Sizing, Limits, Slippage, Profit-Target, globaler Pause-Schalter)
-- [ ] `Core/Trading/ExecutionService.cs` (`TradeSignal` → Risiko → Order → Buchung)
-- [ ] `TradingSettings` in `AppSettings` (Mode Paper/Live, Risikoparameter)
-- [ ] Tests: `RiskService`, `ExecutionService` (voll gemockt)
+### Phase 3 – Trading-Kern (Core) ✅
+- [x] `Core/Trading/TradingModels.cs` (Signal, Order, RiskContext/Decision, Account, Position, Quote)
+- [x] `Core/Trading/IBrokerClient.cs` + **`NullBrokerClient`** (sicherer Default: handelt nie)
+- [x] `Core/Trading/PortfolioService.cs` (+ `IPortfolioService`) + Migration `core_position` (nutzt vorhandene `core_trade_history`/`core_budget`)
+- [x] `Core/Trading/RiskService.cs` (+ `IRiskService`): Sizing, Modul-Limit, Slippage
+- [x] `Core/Trading/ExecutionService.cs` (+ `IExecutionService`): Signal → Kurs → Konto → Risiko → Order → Buchung
+- [x] `TradingSettings` in `AppSettings` (Mode Paper/Live, TradingEnabled, Risikoparameter)
+- [x] Tests: `RiskService` (11), `ExecutionService` (6, voll gemockt) → **38/38 grün**
+- [ ] **Offen (bewusst):** echter `IbkrBrokerClient` (Quote/Konto/Order gegen Client-Portal-Gateway) — manuelle Verifikation gegen Paper-Account
 
 ### Phase 4 – CongressTrading als vollständige Strategie
 - [ ] `CongressTradingStrategy`: neue Scrape-Trades → `TradeSignal` an `ExecutionService`