Merge pull request #9 from alphabench/feat/porfolio-simulation

feat: add Monte Carlo portfolio simulation and bump to 0.3.1
2026-02-17 00:36:45 +05:30 · 2026-02-17 00:35:20 +05:30 · 2026-02-10 05:05:38 +05:30 · 2026-02-10 05:03:39 +05:30 · 2026-02-08 06:06:30 +05:30 · 2026-02-08 06:04:43 +05:30
15 changed files with 878 additions and 48 deletions
@@ -502,7 +502,7 @@ dependencies = [

 [[package]]
 name = "raptorbt"
-version = "0.2.1"
+version = "0.3.1"
 dependencies = [
 "approx",
 "criterion",
@@ -1,12 +1,12 @@
 [package]
 name = "raptorbt"
-version = "0.2.1"
+version = "0.3.1"
 edition = "2021"
 description = "High-performance Rust backtesting engine with Python bindings. Drop-in VectorBT replacement with up insanely faster performance at fractional memory footprint."
 authors = ["Alphabench <contact@alphabench.in>"]
 license = "MIT"
 repository = "https://github.com/alphabench/raptorbt"
-homepage = "https://github.com/alphabench/raptorbt"
+homepage = "https://www.alphabench.in/raptorbt"
 readme = "README.md"
 keywords = ["backtesting", "trading", "quantitative-finance", "rust", "python"]
 categories = ["finance", "simulation"]
@@ -1,9 +1,10 @@
 # RaptorBT

-[![PyPI version](https://img.shields.io/pypi/v/raptorbt.svg)](https://pypi.org/project/raptorbt/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+[![PyPI version](https://img.shields.io/pypi/v/raptorbt.svg)](https://pypi.org/project/raptorbt/)
 [![Python 3.10+](https://img.shields.io/badge/python-3.10+-blue.svg)](https://www.python.org/downloads/)
-[![Rust](https://img.shields.io/badge/rust-1.70+-orange.svg)](https://www.rust-lang.org/)
+[![Rust](https://img.shields.io/badge/rust-1.70+-red.svg)](https://www.rust-lang.org/)
+[![PyPI Downloads](https://static.pepy.tech/personalized-badge/raptorbt?period=total&units=INTERNATIONAL_SYSTEM&left_color=GRAY&right_color=ORANGE&left_text=downloads)](https://pepy.tech/projects/raptorbt)

 **Blazing-fast backtesting for the modern quant.**

@@ -264,6 +265,9 @@ trades = result.trades()  # Returns list of PyTrade objects
 Basic long or short strategy on a single instrument.

 ```python
+# Optional: Instrument-specific configuration
+inst_config = raptorbt.PyInstrumentConfig(lot_size=1.0)
+
 result = raptorbt.run_single_backtest(
    timestamps=timestamps,
    open=open_prices, high=high_prices, low=low_prices,
@@ -273,6 +277,7 @@ result = raptorbt.run_single_backtest(
    weight=1.0,
    symbol="SYMBOL",
    config=config,
+    instrument_config=inst_config,  # Optional: lot_size rounding, capital caps
 )
 ```

@@ -287,10 +292,18 @@ instruments = [
    (timestamps, open3, high3, low3, close3, volume3, entries3, exits3, 1, 0.34, "MSFT"),
 ]

+# Optional: Per-instrument configs for lot_size and capital allocation
+instrument_configs = {
+    "AAPL": raptorbt.PyInstrumentConfig(lot_size=1.0, alloted_capital=33000),
+    "GOOGL": raptorbt.PyInstrumentConfig(lot_size=1.0, alloted_capital=33000),
+    "MSFT": raptorbt.PyInstrumentConfig(lot_size=1.0, alloted_capital=34000),
+}
+
 result = raptorbt.run_basket_backtest(
    instruments=instruments,
    config=config,
    sync_mode="all",  # "all", "any", "majority", "master"
+    instrument_configs=instrument_configs,  # Optional
 )
 ```

@@ -573,18 +586,18 @@ print(f"Max Drawdown: {result.metrics.max_drawdown_pct}%")

 ### Metric Mapping

-| VectorBT Key           | RaptorBT Attribute             |
-| ---------------------- | ------------------------------ |
-| `Total Return [%]`     | `metrics.total_return_pct`     |
-| `Sharpe Ratio`         | `metrics.sharpe_ratio`         |
-| `Sortino Ratio`        | `metrics.sortino_ratio`        |
-| `Max Drawdown [%]`     | `metrics.max_drawdown_pct`     |
-| `Win Rate [%]`         | `metrics.win_rate_pct`         |
-| `Profit Factor`        | `metrics.profit_factor`        |
-| `SQN`                  | `metrics.sqn`                  |
-| `Omega Ratio`          | `metrics.omega_ratio`          |
-| `Total Trades`         | `metrics.total_trades`         |
-| `Expectancy`           | `metrics.expectancy`           |
+| VectorBT Key       | RaptorBT Attribute         |
+| ------------------ | -------------------------- |
+| `Total Return [%]` | `metrics.total_return_pct` |
+| `Sharpe Ratio`     | `metrics.sharpe_ratio`     |
+| `Sortino Ratio`    | `metrics.sortino_ratio`    |
+| `Max Drawdown [%]` | `metrics.max_drawdown_pct` |
+| `Win Rate [%]`     | `metrics.win_rate_pct`     |
+| `Profit Factor`    | `metrics.profit_factor`    |
+| `SQN`              | `metrics.sqn`              |
+| `Omega Ratio`      | `metrics.omega_ratio`      |
+| `Total Trades`     | `metrics.total_trades`     |
+| `Expectancy`       | `metrics.expectancy`       |

 ---

@@ -611,6 +624,29 @@ config.set_atr_target(multiplier: float, period: int)
 config.set_risk_reward_target(ratio: float)
 ```

+### PyInstrumentConfig
+
+Per-instrument configuration for position sizing and risk management.
+
+```python
+inst_config = raptorbt.PyInstrumentConfig(
+    lot_size=1.0,              # Min tradeable quantity (1 for equity, 50 for NIFTY F&O)
+    alloted_capital=50000.0,   # Capital allocated to this instrument (optional)
+    existing_qty=None,         # Existing position quantity (future use)
+    avg_price=None,            # Existing position avg price (future use)
+)
+
+# Optional: per-instrument stop/target overrides
+inst_config.set_fixed_stop(0.02)
+inst_config.set_trailing_stop(0.03)
+inst_config.set_fixed_target(0.05)
+```
+
+**Fields:**
+- `lot_size` - Minimum tradeable quantity. Position sizes are rounded down to nearest lot_size multiple. Use `1.0` for equities, `50.0` for NIFTY F&O, `0.01` for forex.
+- `alloted_capital` - Per-instrument capital cap (capped at available cash).
+- `existing_qty` / `avg_price` - Reserved for future live-to-backtest transitions.
+
 ### PyBacktestResult

 ```python
@@ -797,6 +833,32 @@ MIT License - see [LICENSE](LICENSE) for details.

 ## Changelog

+### v0.3.0
+
+- Per-instrument configuration via `PyInstrumentConfig` (lot_size, alloted_capital, stop/target overrides)
+- Position sizes now correctly rounded to lot_size multiples
+- Support for per-instrument capital allocation in basket backtests
+- Future-ready fields: existing_qty, avg_price for live-to-backtest transitions
+
+### v0.2.2
+
+- Export `run_spread_backtest` Python binding for multi-leg options spread strategies
+- Export `rolling_min` and `rolling_max` indicator functions to Python
+
+### v0.2.1
+
+- Add `rolling_min` and `rolling_max` indicators for LLV (Lowest Low Value) and HHV (Highest High Value) support
+- NaN handling for warmup period
+
+### v0.2.0
+
+- Add multi-leg spread backtesting (`run_spread_backtest`) supporting straddles, strangles, vertical spreads, iron condors, iron butterflies, butterfly spreads, calendar spreads, and diagonal spreads
+- Coordinated entry/exit across all legs with net premium P&L calculation
+- Max loss and target profit exit thresholds for spreads
+- Add `SessionTracker` for intraday session management: market hours detection, squareoff time enforcement, session high/low/open tracking
+- Pre-built session configs for NSE equity (9:15-15:30), MCX commodity (9:00-23:30), and CDS currency (9:00-17:00)
+- Extend `StreamingMetrics` with equity/drawdown tracking, trade recording, and `finalize()` method
+
 ### v0.1.0

 - Initial release
@@ -4,7 +4,7 @@ build-backend = "maturin"

 [project]
 name = "raptorbt"
-version = "0.2.1"
+version = "0.3.1"
 description = "High-performance Rust backtesting engine with Python bindings. Drop-in VectorBT replacement with up insanely faster performance at fractional memory footprint."
 readme = "README.md"
 requires-python = ">=3.10"
@@ -39,9 +39,9 @@ classifiers = [
 ]

 [project.urls]
-Homepage = "https://github.com/alphabench/raptorbt"
+Homepage = "https://www.alphabench.in/raptorbt"
 Repository = "https://github.com/alphabench/raptorbt"
-Documentation = "https://github.com/alphabench/raptorbt#readme"
+Documentation = "https://www.alphabench.in/raptorbt"
 "Bug Tracker" = "https://github.com/alphabench/raptorbt/issues"

 [tool.maturin]
@@ -12,6 +12,7 @@ offering significant performance improvements over vectorbt:
 from raptorbt._raptorbt import (
    # Config classes
    PyBacktestConfig,
+    PyInstrumentConfig,
    PyStopConfig,
    PyTargetConfig,
    # Result classes
@@ -24,6 +25,9 @@ from raptorbt._raptorbt import (
    run_options_backtest,
    run_pairs_backtest,
    run_multi_backtest,
+    run_spread_backtest,
+    # Monte Carlo simulation
+    simulate_portfolio_mc,
    # Indicator functions
    sma,
    ema,
@@ -35,13 +39,16 @@ from raptorbt._raptorbt import (
    adx,
    vwap,
    supertrend,
+    rolling_min,
+    rolling_max,
 )

-__version__ = "0.2.1"
+__version__ = "0.3.1"

 __all__ = [
    # Config classes
    "PyBacktestConfig",
+    "PyInstrumentConfig",
    "PyStopConfig",
    "PyTargetConfig",
    # Result classes
@@ -54,6 +61,9 @@ __all__ = [
    "run_options_backtest",
    "run_pairs_backtest",
    "run_multi_backtest",
+    "run_spread_backtest",
+    # Monte Carlo simulation
+    "simulate_portfolio_mc",
    # Indicator functions
    "sma",
    "ema",
@@ -65,4 +75,6 @@ __all__ = [
    "adx",
    "vwap",
    "supertrend",
+    "rolling_min",
+    "rolling_max",
 ]
@@ -244,6 +244,47 @@ impl Default for BacktestConfig {
    }
 }

+/// Per-instrument configuration for position sizing and risk management.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct InstrumentConfig {
+    /// Minimum tradeable quantity (1.0 for NSE EQ, 50.0 for NIFTY F&O, 0.01 for forex).
+    pub lot_size: Option<f64>,
+    /// Per-instrument capital cap.
+    pub alloted_capital: Option<f64>,
+    /// Per-instrument stop override.
+    pub stop: Option<StopConfig>,
+    /// Per-instrument target override.
+    pub target: Option<TargetConfig>,
+    /// Existing position quantity (future use).
+    pub existing_qty: Option<f64>,
+    /// Existing position average price (future use).
+    pub avg_price: Option<f64>,
+}
+
+impl InstrumentConfig {
+    /// Round a raw position size down to the nearest lot_size multiple.
+    /// Returns raw_size unchanged if lot_size is None or <= 0.
+    pub fn round_to_lot(&self, raw_size: f64) -> f64 {
+        match self.lot_size {
+            Some(lot) if lot > 0.0 => (raw_size / lot).floor() * lot,
+            _ => raw_size,
+        }
+    }
+}
+
+impl Default for InstrumentConfig {
+    fn default() -> Self {
+        Self {
+            lot_size: None,
+            alloted_capital: None,
+            stop: None,
+            target: None,
+            existing_qty: None,
+            avg_price: None,
+        }
+    }
+}
+
 /// Stop-loss configuration.
 #[derive(Debug, Clone, Copy, Serialize, Deserialize)]
 pub enum StopConfig {
@@ -460,3 +501,49 @@ impl Default for Position {
        Self::new()
    }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_round_to_lot_whole_shares() {
+        let config = InstrumentConfig { lot_size: Some(1.0), ..Default::default() };
+        assert_eq!(config.round_to_lot(242.47), 242.0);
+        assert_eq!(config.round_to_lot(1.0), 1.0);
+        assert_eq!(config.round_to_lot(0.5), 0.0);
+    }
+
+    #[test]
+    fn test_round_to_lot_nifty_fo() {
+        let config = InstrumentConfig { lot_size: Some(50.0), ..Default::default() };
+        assert_eq!(config.round_to_lot(242.0), 200.0);
+        assert_eq!(config.round_to_lot(50.0), 50.0);
+        assert_eq!(config.round_to_lot(49.0), 0.0);
+        assert_eq!(config.round_to_lot(150.0), 150.0);
+    }
+
+    #[test]
+    fn test_round_to_lot_fractional() {
+        let config = InstrumentConfig { lot_size: Some(0.01), ..Default::default() };
+        assert!((config.round_to_lot(1.234) - 1.23).abs() < 1e-10);
+    }
+
+    #[test]
+    fn test_round_to_lot_none() {
+        let config = InstrumentConfig::default();
+        assert_eq!(config.round_to_lot(242.47), 242.47);
+    }
+
+    #[test]
+    fn test_round_to_lot_zero() {
+        let config = InstrumentConfig { lot_size: Some(0.0), ..Default::default() };
+        assert_eq!(config.round_to_lot(242.47), 242.47);
+    }
+
+    #[test]
+    fn test_round_to_lot_negative() {
+        let config = InstrumentConfig { lot_size: Some(-1.0), ..Default::default() };
+        assert_eq!(config.round_to_lot(242.47), 242.47);
+    }
+}
@@ -27,6 +27,7 @@ pub mod strategies;
 fn _raptorbt(_py: Python<'_>, m: &PyModule) -> PyResult<()> {
    // Register config classes
    m.add_class::<python::bindings::PyBacktestConfig>()?;
+    m.add_class::<python::bindings::PyInstrumentConfig>()?;
    m.add_class::<python::bindings::PyStopConfig>()?;
    m.add_class::<python::bindings::PyTargetConfig>()?;

@@ -43,6 +44,9 @@ fn _raptorbt(_py: Python<'_>, m: &PyModule) -> PyResult<()> {
    m.add_function(wrap_pyfunction!(python::bindings::run_multi_backtest, m)?)?;
    m.add_function(wrap_pyfunction!(python::bindings::run_spread_backtest, m)?)?;

+    // Register Monte Carlo simulation
+    m.add_function(wrap_pyfunction!(python::bindings::simulate_portfolio_mc, m)?)?;
+
    // Register indicator functions
    m.add_function(wrap_pyfunction!(python::bindings::sma, m)?)?;
    m.add_function(wrap_pyfunction!(python::bindings::ema, m)?)?;
@@ -2,7 +2,7 @@

 use crate::core::types::{
    BacktestConfig, BacktestMetrics, BacktestResult, CompiledSignals, Direction, ExitReason,
-    OhlcvData, Price, StopConfig, TargetConfig, Trade,
+    InstrumentConfig, OhlcvData, Price, StopConfig, TargetConfig, Trade,
 };
 use crate::execution::{FeeModel, FillPrice, SlippageModel};
 use crate::indicators::volatility::atr;
@@ -69,6 +69,24 @@ impl PortfolioEngine {
    /// # Returns
    /// Backtest result
    pub fn run_single(&self, ohlcv: &OhlcvData, signals: &CompiledSignals) -> BacktestResult {
+        self.run_single_with_instrument_config(ohlcv, signals, None)
+    }
+
+    /// Run backtest on single instrument with optional per-instrument configuration.
+    ///
+    /// # Arguments
+    /// * `ohlcv` - OHLCV data
+    /// * `signals` - Compiled trading signals
+    /// * `inst_config` - Optional per-instrument config (lot_size, capital cap, stop/target overrides)
+    ///
+    /// # Returns
+    /// Backtest result
+    pub fn run_single_with_instrument_config(
+        &self,
+        ohlcv: &OhlcvData,
+        signals: &CompiledSignals,
+        inst_config: Option<&InstrumentConfig>,
+    ) -> BacktestResult {
        let n = ohlcv.len();
        assert_eq!(n, signals.len(), "OHLCV and signals must have same length");

@@ -86,14 +104,20 @@ impl PortfolioEngine {
        let mut streaming = StreamingMetrics::new();
        let mut peak_equity = cash;

+        // Determine effective stop/target configs (per-instrument overrides take precedence)
+        let effective_stop =
+            inst_config.and_then(|ic| ic.stop.as_ref()).unwrap_or(&self.config.stop);
+        let effective_target =
+            inst_config.and_then(|ic| ic.target.as_ref()).unwrap_or(&self.config.target);
+
        // Pre-calculate ATR for ATR-based stops
-        let atr_values = if matches!(self.config.stop, StopConfig::Atr { .. })
-            || matches!(self.config.target, TargetConfig::Atr { .. })
+        let atr_values = if matches!(effective_stop, StopConfig::Atr { .. })
+            || matches!(effective_target, TargetConfig::Atr { .. })
        {
-            let period = match self.config.stop {
-                StopConfig::Atr { period, .. } => period,
-                _ => match self.config.target {
-                    TargetConfig::Atr { period, .. } => period,
+            let period = match effective_stop {
+                StopConfig::Atr { period, .. } => *period,
+                _ => match effective_target {
+                    TargetConfig::Atr { period, .. } => *period,
                    _ => 14,
                },
            };
@@ -188,8 +212,8 @@ impl PortfolioEngine {

                // Update trailing stop if position still open
                if position.is_in_position() {
-                    if let StopConfig::Trailing { percent } = self.config.stop {
-                        position.update_trailing_stop(percent);
+                    if let StopConfig::Trailing { percent } = effective_stop {
+                        position.update_trailing_stop(*percent);
                    }
                }
            }
@@ -207,26 +231,37 @@ impl PortfolioEngine {
                );

                // Calculate position size
+                // Use per-instrument capital if set, capped at available cash
+                let available = inst_config
+                    .and_then(|ic| ic.alloted_capital)
+                    .map(|cap| cap.min(cash))
+                    .unwrap_or(cash);
+
                // VectorBT formula: size = cash / (price * (1 + fees))
                // This ensures the position value plus entry fee equals available cash
                let fee_rate = self.config.fees;
-                let size = if let Some(ref sizes) = signals.position_sizes {
-                    sizes[i] * cash / (adjusted_price * (1.0 + fee_rate))
+                let raw_size = if let Some(ref sizes) = signals.position_sizes {
+                    sizes[i] * available / (adjusted_price * (1.0 + fee_rate))
                } else {
-                    cash / (adjusted_price * (1.0 + fee_rate))
+                    available / (adjusted_price * (1.0 + fee_rate))
                };

+                // Round to lot_size
+                let size = inst_config.map(|ic| ic.round_to_lot(raw_size)).unwrap_or(raw_size);
+
                if size > 0.0 {
                    // Calculate entry fees
                    let entry_fees =
                        self.fee_model.calculate(adjusted_price, size, signals.direction);

                    // Calculate stop and target prices
-                    let (stop_price, target_price) = self.calculate_stop_target(
+                    let (stop_price, target_price) = self.calculate_stop_target_with_config(
                        adjusted_price,
                        signals.direction,
                        &atr_values,
                        i,
+                        effective_stop,
+                        effective_target,
                    );

                    // Open position (passing entry_fees for trade PnL tracking)
@@ -310,18 +345,39 @@ impl PortfolioEngine {
        )
    }

-    /// Calculate stop and target prices.
+    /// Calculate stop and target prices using the global config.
+    #[allow(dead_code)]
    fn calculate_stop_target(
        &self,
        entry_price: Price,
        direction: Direction,
        atr_values: &[f64],
        idx: usize,
+    ) -> (Option<Price>, Option<Price>) {
+        self.calculate_stop_target_with_config(
+            entry_price,
+            direction,
+            atr_values,
+            idx,
+            &self.config.stop,
+            &self.config.target,
+        )
+    }
+
+    /// Calculate stop and target prices with explicit stop/target configs.
+    fn calculate_stop_target_with_config(
+        &self,
+        entry_price: Price,
+        direction: Direction,
+        atr_values: &[f64],
+        idx: usize,
+        stop_config: &StopConfig,
+        target_config: &TargetConfig,
    ) -> (Option<Price>, Option<Price>) {
        let multiplier = direction.multiplier();

        // Calculate stop price
-        let stop_price = match self.config.stop {
+        let stop_price = match stop_config {
            StopConfig::None => None,
            StopConfig::Fixed { percent } => Some(entry_price * (1.0 - multiplier * percent)),
            StopConfig::Atr { multiplier: m, .. } => {
@@ -336,7 +392,7 @@ impl PortfolioEngine {
        };

        // Calculate target price
-        let target_price = match self.config.target {
+        let target_price = match target_config {
            TargetConfig::None => None,
            TargetConfig::Fixed { percent } => Some(entry_price * (1.0 + multiplier * percent)),
            TargetConfig::Atr { multiplier: m, .. } => {
@@ -2,8 +2,10 @@

 pub mod allocation;
 pub mod engine;
+pub mod monte_carlo;
 pub mod position;

 pub use allocation::{AllocationStrategy, CapitalAllocator};
 pub use engine::PortfolioEngine;
+pub use monte_carlo::{simulate_portfolio_forward, MonteCarloConfig, MonteCarloResult};
 pub use position::PositionManager;
@@ -0,0 +1,361 @@
+//! Monte Carlo forward simulation for portfolio projection.
+//!
+//! Uses Geometric Brownian Motion (GBM) with Cholesky decomposition
+//! for correlated multi-asset simulation. Parallelized via Rayon.
+
+use rayon::prelude::*;
+
+/// Configuration for Monte Carlo simulation.
+#[derive(Debug, Clone)]
+pub struct MonteCarloConfig {
+    pub n_simulations: usize,
+    pub horizon_days: usize,
+    pub seed: u64,
+}
+
+impl Default for MonteCarloConfig {
+    fn default() -> Self {
+        Self { n_simulations: 10_000, horizon_days: 252, seed: 42 }
+    }
+}
+
+/// Result of a Monte Carlo simulation.
+#[derive(Debug, Clone)]
+pub struct MonteCarloResult {
+    /// Percentile paths: Vec of (percentile, path_values)
+    pub percentile_paths: Vec<(f64, Vec<f64>)>,
+    /// Terminal value for each simulation
+    pub final_values: Vec<f64>,
+    /// Expected annualized return
+    pub expected_return: f64,
+    /// Probability of loss (final value < initial value)
+    pub probability_of_loss: f64,
+    /// Value at Risk at 95% confidence
+    pub var_95: f64,
+    /// Conditional Value at Risk at 95% confidence
+    pub cvar_95: f64,
+}
+
+/// Cholesky decomposition of a symmetric positive-definite matrix.
+/// Returns lower-triangular matrix L such that A = L * L^T.
+fn cholesky(matrix: &[Vec<f64>]) -> Result<Vec<Vec<f64>>, &'static str> {
+    let n = matrix.len();
+    let mut l = vec![vec![0.0; n]; n];
+
+    for i in 0..n {
+        for j in 0..=i {
+            let mut sum = 0.0;
+            for k in 0..j {
+                sum += l[i][k] * l[j][k];
+            }
+
+            if i == j {
+                let diag = matrix[i][i] - sum;
+                if diag <= 0.0 {
+                    // Matrix is not positive definite; use a small epsilon
+                    l[i][j] = (diag.abs().max(1e-10)).sqrt();
+                } else {
+                    l[i][j] = diag.sqrt();
+                }
+            } else {
+                if l[j][j].abs() < 1e-15 {
+                    l[i][j] = 0.0;
+                } else {
+                    l[i][j] = (matrix[i][j] - sum) / l[j][j];
+                }
+            }
+        }
+    }
+
+    Ok(l)
+}
+
+/// Simple xoshiro256** PRNG for deterministic parallel simulation.
+#[derive(Clone)]
+struct Xoshiro256 {
+    s: [u64; 4],
+}
+
+impl Xoshiro256 {
+    fn new(seed: u64) -> Self {
+        // SplitMix64 to seed all 4 state words
+        let mut z = seed;
+        let mut s = [0u64; 4];
+        for item in &mut s {
+            z = z.wrapping_add(0x9e3779b97f4a7c15);
+            z = (z ^ (z >> 30)).wrapping_mul(0xbf58476d1ce4e5b9);
+            z = (z ^ (z >> 27)).wrapping_mul(0x94d049bb133111eb);
+            *item = z ^ (z >> 31);
+        }
+        Self { s }
+    }
+
+    fn jump(&mut self) {
+        // Jump function: advances state by 2^128 calls
+        const JUMP: [u64; 4] =
+            [0x180ec6d33cfd0aba, 0xd5a61266f0c9392c, 0xa9582618e03fc9aa, 0x39abdc4529b1661c];
+        let mut s0: u64 = 0;
+        let mut s1: u64 = 0;
+        let mut s2: u64 = 0;
+        let mut s3: u64 = 0;
+        for j in &JUMP {
+            for b in 0..64 {
+                if j & (1u64 << b) != 0 {
+                    s0 ^= self.s[0];
+                    s1 ^= self.s[1];
+                    s2 ^= self.s[2];
+                    s3 ^= self.s[3];
+                }
+                self.next_u64();
+            }
+        }
+        self.s[0] = s0;
+        self.s[1] = s1;
+        self.s[2] = s2;
+        self.s[3] = s3;
+    }
+
+    fn next_u64(&mut self) -> u64 {
+        let result = (self.s[1].wrapping_mul(5)).rotate_left(7).wrapping_mul(9);
+        let t = self.s[1] << 17;
+        self.s[2] ^= self.s[0];
+        self.s[3] ^= self.s[1];
+        self.s[1] ^= self.s[2];
+        self.s[0] ^= self.s[3];
+        self.s[2] ^= t;
+        self.s[3] = self.s[3].rotate_left(45);
+        result
+    }
+
+    /// Generate uniform f64 in [0, 1).
+    fn next_f64(&mut self) -> f64 {
+        (self.next_u64() >> 11) as f64 * (1.0 / (1u64 << 53) as f64)
+    }
+
+    /// Box-Muller transform for standard normal.
+    fn next_normal(&mut self) -> f64 {
+        let u1 = self.next_f64().max(1e-15);
+        let u2 = self.next_f64();
+        (-2.0 * u1.ln()).sqrt() * (2.0 * std::f64::consts::PI * u2).cos()
+    }
+}
+
+/// Core Monte Carlo simulation function.
+///
+/// # Arguments
+/// * `returns` - Per-strategy daily returns (N strategies x T days each)
+/// * `weights` - Portfolio weights (length N, must sum to 1)
+/// * `correlation_matrix` - N x N correlation matrix
+/// * `initial_value` - Starting portfolio value
+/// * `config` - Simulation configuration
+pub fn simulate_portfolio_forward(
+    returns: &[Vec<f64>],
+    weights: &[f64],
+    correlation_matrix: &[Vec<f64>],
+    initial_value: f64,
+    config: &MonteCarloConfig,
+) -> MonteCarloResult {
+    let n_assets = returns.len();
+    let dt = 1.0; // daily time step
+
+    // Compute per-asset mean and std of historical returns
+    let mut mus = vec![0.0; n_assets];
+    let mut sigmas = vec![0.0; n_assets];
+    for (i, ret) in returns.iter().enumerate() {
+        if ret.is_empty() {
+            continue;
+        }
+        let mean = ret.iter().sum::<f64>() / ret.len() as f64;
+        let var = ret.iter().map(|r| (r - mean).powi(2)).sum::<f64>() / ret.len() as f64;
+        mus[i] = mean;
+        sigmas[i] = var.sqrt().max(1e-10);
+    }
+
+    // Cholesky decomposition of correlation matrix
+    let chol = cholesky(correlation_matrix).unwrap_or_else(|_| {
+        // Fallback: identity matrix (independent assets)
+        let mut identity = vec![vec![0.0; n_assets]; n_assets];
+        for i in 0..n_assets {
+            identity[i][i] = 1.0;
+        }
+        identity
+    });
+
+    // Prepare a base RNG and create per-chunk seeds via jumping
+    let mut base_rng = Xoshiro256::new(config.seed);
+    let n_chunks = rayon::current_num_threads().max(1);
+    let chunk_size = (config.n_simulations + n_chunks - 1) / n_chunks;
+
+    let chunk_rngs: Vec<Xoshiro256> = (0..n_chunks)
+        .map(|_| {
+            let rng = base_rng.clone();
+            base_rng.jump();
+            rng
+        })
+        .collect();
+
+    // Run simulations in parallel chunks
+    let all_paths: Vec<Vec<f64>> = chunk_rngs
+        .into_par_iter()
+        .enumerate()
+        .flat_map(|(chunk_idx, mut rng)| {
+            let start = chunk_idx * chunk_size;
+            let end = (start + chunk_size).min(config.n_simulations);
+            let mut chunk_paths = Vec::with_capacity(end - start);
+
+            for _ in start..end {
+                let mut portfolio_value = initial_value;
+                let mut path = Vec::with_capacity(config.horizon_days + 1);
+                path.push(portfolio_value);
+
+                for _ in 0..config.horizon_days {
+                    // Generate N independent standard normals
+                    let z_indep: Vec<f64> = (0..n_assets).map(|_| rng.next_normal()).collect();
+
+                    // Correlate via Cholesky: z_corr = L * z_indep
+                    let mut z_corr = vec![0.0; n_assets];
+                    for i in 0..n_assets {
+                        for j in 0..=i {
+                            z_corr[i] += chol[i][j] * z_indep[j];
+                        }
+                    }
+
+                    // GBM per asset, then weighted portfolio return
+                    let mut portfolio_return = 0.0;
+                    for i in 0..n_assets {
+                        let drift = (mus[i] - 0.5 * sigmas[i].powi(2)) * dt;
+                        let diffusion = sigmas[i] * dt.sqrt() * z_corr[i];
+                        let asset_return = (drift + diffusion).exp() - 1.0;
+                        portfolio_return += weights[i] * asset_return;
+                    }
+
+                    portfolio_value *= 1.0 + portfolio_return;
+                    path.push(portfolio_value);
+                }
+
+                chunk_paths.push(path);
+            }
+
+            chunk_paths
+        })
+        .collect();
+
+    // Extract final values
+    let mut final_values: Vec<f64> = all_paths.iter().map(|p| *p.last().unwrap()).collect();
+    final_values.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
+
+    let n = final_values.len();
+
+    // Percentile paths: find simulations closest to each percentile's final value
+    let percentiles = [5.0, 25.0, 50.0, 75.0, 95.0];
+    let percentile_paths: Vec<(f64, Vec<f64>)> = percentiles
+        .iter()
+        .map(|&pct| {
+            let idx = ((pct / 100.0) * (n as f64 - 1.0)).round() as usize;
+            let target_final = final_values[idx.min(n - 1)];
+
+            // Find the simulation path whose final value is closest to target
+            let best_idx = all_paths
+                .iter()
+                .enumerate()
+                .min_by(|(_, a), (_, b)| {
+                    let da = (a.last().unwrap() - target_final).abs();
+                    let db = (b.last().unwrap() - target_final).abs();
+                    da.partial_cmp(&db).unwrap_or(std::cmp::Ordering::Equal)
+                })
+                .map(|(i, _)| i)
+                .unwrap_or(0);
+
+            (pct, all_paths[best_idx].clone())
+        })
+        .collect();
+
+    // Expected return (annualized from mean of final values)
+    let mean_final = final_values.iter().sum::<f64>() / n as f64;
+    let expected_return = (mean_final / initial_value - 1.0) * 100.0;
+
+    // Probability of loss
+    let n_loss = final_values.iter().filter(|&&v| v < initial_value).count();
+    let probability_of_loss = n_loss as f64 / n as f64;
+
+    // VaR 95%: 5th percentile loss
+    let p5_idx = ((0.05 * (n as f64 - 1.0)).round() as usize).min(n - 1);
+    let var_95 = ((initial_value - final_values[p5_idx]) / initial_value * 100.0).max(0.0);
+
+    // CVaR 95%: average of losses below VaR
+    let cvar_values = &final_values[..=p5_idx];
+    let cvar_95 = if cvar_values.is_empty() {
+        var_95
+    } else {
+        let avg_tail = cvar_values.iter().sum::<f64>() / cvar_values.len() as f64;
+        ((initial_value - avg_tail) / initial_value * 100.0).max(0.0)
+    };
+
+    MonteCarloResult {
+        percentile_paths,
+        final_values,
+        expected_return,
+        probability_of_loss,
+        var_95,
+        cvar_95,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_cholesky_identity() {
+        let matrix = vec![vec![1.0, 0.0], vec![0.0, 1.0]];
+        let l = cholesky(&matrix).unwrap();
+        assert!((l[0][0] - 1.0).abs() < 1e-10);
+        assert!((l[1][1] - 1.0).abs() < 1e-10);
+        assert!(l[0][1].abs() < 1e-10);
+        assert!(l[1][0].abs() < 1e-10);
+    }
+
+    #[test]
+    fn test_cholesky_correlated() {
+        let matrix = vec![vec![1.0, 0.5], vec![0.5, 1.0]];
+        let l = cholesky(&matrix).unwrap();
+        // Verify L * L^T = matrix
+        let reconstructed_00 = l[0][0] * l[0][0];
+        let reconstructed_01 = l[1][0] * l[0][0];
+        let reconstructed_11 = l[1][0] * l[1][0] + l[1][1] * l[1][1];
+        assert!((reconstructed_00 - 1.0).abs() < 1e-10);
+        assert!((reconstructed_01 - 0.5).abs() < 1e-10);
+        assert!((reconstructed_11 - 1.0).abs() < 1e-10);
+    }
+
+    #[test]
+    fn test_simulate_basic() {
+        // Two assets with identical positive returns
+        let returns = vec![vec![0.001; 252], vec![0.001; 252]];
+        let weights = vec![0.5, 0.5];
+        let corr = vec![vec![1.0, 0.0], vec![0.0, 1.0]];
+        let config = MonteCarloConfig { n_simulations: 100, horizon_days: 10, seed: 42 };
+
+        let result = simulate_portfolio_forward(&returns, &weights, &corr, 100000.0, &config);
+
+        assert_eq!(result.final_values.len(), 100);
+        assert_eq!(result.percentile_paths.len(), 5);
+        // Expected return should be positive given positive drift
+        assert!(result.expected_return > -50.0); // Sanity check
+    }
+
+    #[test]
+    fn test_deterministic() {
+        let returns = vec![vec![0.001; 100], vec![-0.0005; 100]];
+        let weights = vec![0.6, 0.4];
+        let corr = vec![vec![1.0, -0.3], vec![-0.3, 1.0]];
+        let config = MonteCarloConfig { n_simulations: 50, horizon_days: 20, seed: 123 };
+
+        let r1 = simulate_portfolio_forward(&returns, &weights, &corr, 100000.0, &config);
+        let r2 = simulate_portfolio_forward(&returns, &weights, &corr, 100000.0, &config);
+
+        // Same seed should produce same final values (single-threaded determinism)
+        // Note: with rayon, parallelism may affect order but not values
+        assert!((r1.expected_return - r2.expected_return).abs() < 1e-6);
+    }
+}
@@ -3,8 +3,11 @@
 use numpy::{PyArray1, PyReadonlyArray1};
 use pyo3::prelude::*;

+use std::collections::HashMap;
+
 use crate::core::types::{
-    BacktestConfig, CompiledSignals, Direction, OhlcvData, StopConfig, TargetConfig,
+    BacktestConfig, CompiledSignals, Direction, InstrumentConfig, OhlcvData, StopConfig,
+    TargetConfig,
 };
 use crate::indicators;
 use crate::signals::synchronizer::SyncMode;
@@ -100,6 +103,93 @@ impl From<&PyBacktestConfig> for BacktestConfig {
    }
 }

+/// Python-exposed per-instrument configuration.
+#[pyclass]
+#[derive(Debug, Clone)]
+pub struct PyInstrumentConfig {
+    #[pyo3(get, set)]
+    pub lot_size: Option<f64>,
+    #[pyo3(get, set)]
+    pub alloted_capital: Option<f64>,
+    #[pyo3(get, set)]
+    pub existing_qty: Option<f64>,
+    #[pyo3(get, set)]
+    pub avg_price: Option<f64>,
+    stop_config: Option<StopConfig>,
+    target_config: Option<TargetConfig>,
+}
+
+#[pymethods]
+impl PyInstrumentConfig {
+    #[new]
+    #[pyo3(signature = (lot_size=None, alloted_capital=None, existing_qty=None, avg_price=None))]
+    fn new(
+        lot_size: Option<f64>,
+        alloted_capital: Option<f64>,
+        existing_qty: Option<f64>,
+        avg_price: Option<f64>,
+    ) -> Self {
+        Self {
+            lot_size,
+            alloted_capital,
+            existing_qty,
+            avg_price,
+            stop_config: None,
+            target_config: None,
+        }
+    }
+
+    /// Set fixed percentage stop-loss override.
+    fn set_fixed_stop(&mut self, percent: f64) {
+        self.stop_config = Some(StopConfig::Fixed { percent });
+    }
+
+    /// Set ATR-based stop-loss override.
+    fn set_atr_stop(&mut self, multiplier: f64, period: usize) {
+        self.stop_config = Some(StopConfig::Atr { multiplier, period });
+    }
+
+    /// Set trailing stop-loss override.
+    fn set_trailing_stop(&mut self, percent: f64) {
+        self.stop_config = Some(StopConfig::Trailing { percent });
+    }
+
+    /// Set fixed percentage take-profit override.
+    fn set_fixed_target(&mut self, percent: f64) {
+        self.target_config = Some(TargetConfig::Fixed { percent });
+    }
+
+    /// Set ATR-based take-profit override.
+    fn set_atr_target(&mut self, multiplier: f64, period: usize) {
+        self.target_config = Some(TargetConfig::Atr { multiplier, period });
+    }
+
+    /// Set risk-reward based take-profit override.
+    fn set_risk_reward_target(&mut self, ratio: f64) {
+        self.target_config = Some(TargetConfig::RiskReward { ratio });
+    }
+
+    fn __repr__(&self) -> String {
+        format!(
+            "InstrumentConfig(lot_size={:?}, alloted_capital={:?})",
+            self.lot_size, self.alloted_capital
+        )
+    }
+}
+
+impl From<&PyInstrumentConfig> for InstrumentConfig {
+    fn from(py_config: &PyInstrumentConfig) -> Self {
+        InstrumentConfig {
+            lot_size: py_config.lot_size,
+            alloted_capital: py_config.alloted_capital,
+            stop: py_config.stop_config,
+            target: py_config.target_config,
+            existing_qty: py_config.existing_qty,
+            avg_price: py_config.avg_price,
+        }
+    }
+}
+
 /// Python-exposed stop configuration.
 #[pyclass]
 #[derive(Debug, Clone)]
@@ -419,7 +509,7 @@ impl PyBacktestResult {

 /// Run single instrument backtest.
 #[pyfunction]
-#[pyo3(signature = (timestamps, open, high, low, close, volume, entries, exits, direction=1, weight=1.0, symbol="UNKNOWN", config=None, position_sizes=None))]
+#[pyo3(signature = (timestamps, open, high, low, close, volume, entries, exits, direction=1, weight=1.0, symbol="UNKNOWN", config=None, position_sizes=None, instrument_config=None))]
 pub fn run_single_backtest<'py>(
    _py: Python<'py>,
    timestamps: PyReadonlyArray1<i64>,
@@ -435,6 +525,7 @@ pub fn run_single_backtest<'py>(
    symbol: &str,
    config: Option<&PyBacktestConfig>,
    position_sizes: Option<PyReadonlyArray1<f64>>,
+    instrument_config: Option<&PyInstrumentConfig>,
 ) -> PyResult<PyBacktestResult> {
    let ohlcv = OhlcvData {
        timestamps: numpy_to_vec_i64(timestamps),
@@ -457,16 +548,17 @@ pub fn run_single_backtest<'py>(
    };

    let rust_config = config.map(|c| BacktestConfig::from(c)).unwrap_or_default();
+    let inst_config = instrument_config.map(InstrumentConfig::from);

    let backtest = SingleBacktest::new(rust_config);
-    let result = backtest.run(&ohlcv, &signals);
+    let result = backtest.run_with_instrument_config(&ohlcv, &signals, inst_config.as_ref());

    Ok(convert_result(result))
 }

 /// Run basket/collective backtest.
 #[pyfunction]
-#[pyo3(signature = (instruments, config=None, sync_mode="all"))]
+#[pyo3(signature = (instruments, config=None, sync_mode="all", instrument_configs=None))]
 pub fn run_basket_backtest<'py>(
    _py: Python<'py>,
    instruments: Vec<(
@@ -484,6 +576,7 @@ pub fn run_basket_backtest<'py>(
    )>,
    config: Option<&PyBacktestConfig>,
    sync_mode: &str,
+    instrument_configs: Option<HashMap<String, PyInstrumentConfig>>,
 ) -> PyResult<PyBacktestResult> {
    let rust_instruments: Vec<(OhlcvData, CompiledSignals)> = instruments
        .into_iter()
@@ -521,8 +614,15 @@ pub fn run_basket_backtest<'py>(
        ..Default::default()
    };

+    // Convert PyInstrumentConfig map to InstrumentConfig map
+    let rust_inst_configs: Option<HashMap<String, InstrumentConfig>> =
+        instrument_configs.map(|configs| {
+            configs.iter().map(|(k, v)| (k.clone(), InstrumentConfig::from(v))).collect()
+        });
+
    let backtest = BasketBacktest::new(basket_config);
-    let result = backtest.run(&rust_instruments);
+    let result =
+        backtest.run_with_instrument_configs(&rust_instruments, rust_inst_configs.as_ref());

    Ok(convert_result(result))
 }
@@ -998,6 +1098,77 @@ pub fn rolling_max<'py>(
 // Helper Functions
 // ============================================================================

+// ============================================================================
+// Monte Carlo Forward Simulation
+// ============================================================================
+
+/// Run Monte Carlo forward simulation for a portfolio.
+///
+/// Uses Geometric Brownian Motion with Cholesky-decomposed correlated random
+/// draws, parallelized via Rayon.
+///
+/// # Arguments
+/// * `returns` - List of per-strategy return arrays (N strategies)
+/// * `weights` - Portfolio weight vector (length N, sums to 1)
+/// * `correlation_matrix` - N x N correlation matrix (flattened row-major as 2D list)
+/// * `initial_value` - Starting portfolio value
+/// * `n_simulations` - Number of simulation paths (default: 10000)
+/// * `horizon_days` - Forward simulation horizon in trading days (default: 252)
+/// * `seed` - Random seed for reproducibility (default: 42)
+#[pyfunction]
+#[pyo3(signature = (returns, weights, correlation_matrix, initial_value, n_simulations=10000, horizon_days=252, seed=42))]
+pub fn simulate_portfolio_mc(
+    py: Python<'_>,
+    returns: Vec<PyReadonlyArray1<'_, f64>>,
+    weights: PyReadonlyArray1<'_, f64>,
+    correlation_matrix: Vec<PyReadonlyArray1<'_, f64>>,
+    initial_value: f64,
+    n_simulations: usize,
+    horizon_days: usize,
+    seed: u64,
+) -> PyResult<PyObject> {
+    use crate::portfolio::monte_carlo::{simulate_portfolio_forward, MonteCarloConfig};
+
+    // Convert numpy arrays to Rust vecs
+    let rust_returns: Vec<Vec<f64>> =
+        returns.iter().map(|arr| arr.as_slice().unwrap().to_vec()).collect();
+
+    let rust_weights: Vec<f64> = weights.as_slice().unwrap().to_vec();
+
+    let rust_corr: Vec<Vec<f64>> =
+        correlation_matrix.iter().map(|arr| arr.as_slice().unwrap().to_vec()).collect();
+
+    let config = MonteCarloConfig { n_simulations, horizon_days, seed };
+
+    // Run simulation (releases GIL for Rayon parallelism)
+    let result = py.allow_threads(|| {
+        simulate_portfolio_forward(&rust_returns, &rust_weights, &rust_corr, initial_value, &config)
+    });
+
+    // Build Python dict result
+    let dict = pyo3::types::PyDict::new(py);
+
+    // percentile_paths: list of (percentile, list[float])
+    let paths_list = pyo3::types::PyList::empty(py);
+    for (pct, path) in &result.percentile_paths {
+        let path_list = pyo3::types::PyList::new(py, path);
+        let tuple = pyo3::types::PyTuple::new(py, &[pct.to_object(py), path_list.to_object(py)]);
+        paths_list.append(tuple)?;
+    }
+    dict.set_item("percentile_paths", paths_list)?;
+
+    // final_values as numpy array for efficiency
+    let final_arr = PyArray1::from_vec(py, result.final_values);
+    dict.set_item("final_values", final_arr)?;
+
+    dict.set_item("expected_return", result.expected_return)?;
+    dict.set_item("probability_of_loss", result.probability_of_loss)?;
+    dict.set_item("var_95", result.var_95)?;
+    dict.set_item("cvar_95", result.cvar_95)?;
+
+    Ok(dict.into())
+}
+
 /// Convert Rust BacktestResult to Python PyBacktestResult.
 fn convert_result(result: crate::core::types::BacktestResult) -> PyBacktestResult {
    let metrics = PyBacktestMetrics {
@@ -2,8 +2,11 @@
 //!
 //! Supports multiple instruments with synchronized signals.

+use std::collections::HashMap;
+
 use crate::core::types::{
-    BacktestConfig, BacktestMetrics, BacktestResult, CompiledSignals, ExitReason, OhlcvData, Trade,
+    BacktestConfig, BacktestMetrics, BacktestResult, CompiledSignals, ExitReason, InstrumentConfig,
+    OhlcvData, Trade,
 };
 use crate::execution::FeeModel;
 use crate::metrics::streaming::StreamingMetrics;
@@ -74,6 +77,22 @@ impl BasketBacktest {
    /// # Returns
    /// Combined backtest result
    pub fn run(&self, instruments: &[(OhlcvData, CompiledSignals)]) -> BacktestResult {
+        self.run_with_instrument_configs(instruments, None)
+    }
+
+    /// Run basket backtest with optional per-instrument configurations.
+    ///
+    /// # Arguments
+    /// * `instruments` - Vector of (OhlcvData, CompiledSignals) pairs for each instrument
+    /// * `instrument_configs` - Optional map of symbol -> InstrumentConfig
+    ///
+    /// # Returns
+    /// Combined backtest result
+    pub fn run_with_instrument_configs(
+        &self,
+        instruments: &[(OhlcvData, CompiledSignals)],
+        instrument_configs: Option<&HashMap<String, InstrumentConfig>>,
+    ) -> BacktestResult {
        if instruments.is_empty() {
            return self.empty_result();
        }
@@ -168,7 +187,15 @@ impl BasketBacktest {
                // Calculate position sizes
                let prices: Vec<f64> = instruments.iter().map(|(o, _)| o.close[i]).collect();
                let weights: Vec<f64> = instruments.iter().map(|(_, s)| s.weight).collect();
-                let sizes = self.calculate_sizes(&prices, &weights, cash);
+                let symbols: Vec<&str> =
+                    instruments.iter().map(|(_, s)| s.symbol.as_str()).collect();
+                let sizes = self.calculate_sizes_with_configs(
+                    &prices,
+                    &weights,
+                    cash,
+                    &symbols,
+                    instrument_configs,
+                );

                // Enter positions
                for (inst_idx, (ohlcv, signals)) in instruments.iter().enumerate() {
@@ -249,7 +276,21 @@ impl BasketBacktest {
    }

    /// Calculate position sizes for each instrument.
+    #[allow(dead_code)]
    fn calculate_sizes(&self, prices: &[f64], weights: &[f64], available_capital: f64) -> Vec<f64> {
+        let symbols: Vec<&str> = vec![""; prices.len()];
+        self.calculate_sizes_with_configs(prices, weights, available_capital, &symbols, None)
+    }
+
+    /// Calculate position sizes with optional per-instrument config (lot_size rounding, capital caps).
+    fn calculate_sizes_with_configs(
+        &self,
+        prices: &[f64],
+        weights: &[f64],
+        available_capital: f64,
+        symbols: &[&str],
+        instrument_configs: Option<&HashMap<String, InstrumentConfig>>,
+    ) -> Vec<f64> {
        let n = prices.len();
        let total_weight: f64 = weights.iter().sum();

@@ -260,12 +301,26 @@ impl BasketBacktest {
        prices
            .iter()
            .zip(weights.iter())
-            .map(|(&price, &weight)| {
+            .enumerate()
+            .map(|(idx, (&price, &weight))| {
                if price <= 0.0 {
                    return 0.0;
                }
-                let allocation = available_capital * (weight / total_weight);
-                allocation / price
+                let default_allocation = available_capital * (weight / total_weight);
+
+                // Use per-instrument alloted_capital if set, capped at default allocation
+                let inst_config = instrument_configs
+                    .and_then(|configs| symbols.get(idx).and_then(|sym| configs.get(*sym)));
+
+                let allocation = inst_config
+                    .and_then(|ic| ic.alloted_capital)
+                    .map(|cap| cap.min(default_allocation))
+                    .unwrap_or(default_allocation);
+
+                let raw_size = allocation / price;
+
+                // Round to lot_size
+                inst_config.map(|ic| ic.round_to_lot(raw_size)).unwrap_or(raw_size)
            })
            .collect()
    }
@@ -1,6 +1,8 @@
 //! Single instrument backtest implementation.

-use crate::core::types::{BacktestConfig, BacktestResult, CompiledSignals, OhlcvData};
+use crate::core::types::{
+    BacktestConfig, BacktestResult, CompiledSignals, InstrumentConfig, OhlcvData,
+};
 use crate::portfolio::engine::PortfolioEngine;

 /// Single instrument backtest runner.
@@ -28,6 +30,24 @@ impl SingleBacktest {
        self.engine.run_single(ohlcv, signals)
    }

+    /// Run the backtest with per-instrument configuration.
+    ///
+    /// # Arguments
+    /// * `ohlcv` - OHLCV price data
+    /// * `signals` - Compiled trading signals
+    /// * `inst_config` - Optional per-instrument config (lot_size, capital cap, stop/target overrides)
+    ///
+    /// # Returns
+    /// Backtest result with metrics, trades, and equity curve
+    pub fn run_with_instrument_config(
+        &self,
+        ohlcv: &OhlcvData,
+        signals: &CompiledSignals,
+        inst_config: Option<&InstrumentConfig>,
+    ) -> BacktestResult {
+        self.engine.run_single_with_instrument_config(ohlcv, signals, inst_config)
+    }
+
    /// Run backtest from raw arrays.
    ///
    /// # Arguments
Author	SHA1	Message	Date
vatsal	ab568cc9fb	Merge pull request #9 from alphabench/feat/porfolio-simulation feat: add Monte Carlo portfolio simulation and bump to 0.3.1	2026-02-17 00:36:45 +05:30
porcelaincode	4d4ea2e5e9	feat: add Monte Carlo portfolio simulation and bump to 0.3.1 - Add Monte Carlo forward simulation using Geometric Brownian Motion - Support correlated multi-asset simulation with Cholesky decomposition - Implement parallel execution via Rayon for performance - Expose simulate_portfolio_mc function in Python bindings - Update version from 0.3.0 to 0.3.1 across all project files	2026-02-17 00:35:20 +05:30
vatsal	a82ddc598a	Merge pull request #8 from alphabench/feat/instrument-level-config feat: add instrument level config and bump to 0.3.0	2026-02-10 05:05:38 +05:30
porcelaincode	bb6ce05c57	feat: add instrument level config and bump to 0.3.0	2026-02-10 05:03:39 +05:30
vatsal	aad09da117	Merge pull request #7 from alphabench/fix/spread-backtest feat: add new backtest functions	2026-02-08 06:06:30 +05:30
porcelaincode	c711e9ce8e	feat: add new backtest functions	2026-02-08 06:04:43 +05:30