Risk Rules Overview

The framework lets you express risk and execution behaviour as declarative rule lists on a TradingStrategy rather than as ad-hoc code paths. The vector backtest engine, the event-driven backtest engine and the live trading runtime all read the same rule objects, so a strategy behaves identically across all three modes.

from investing_algorithm_framework import (
    TradingStrategy,
    PositionSize,
    StopLossRule,
    TakeProfitRule,
    ScalingRule,
    ExposureRule,
    CooldownRule,
    TradingCost,
)


class MyStrategy(TradingStrategy):
    symbols = ["BTC", "ETH"]

    position_sizes = [
        PositionSize(symbol="BTC", percentage_of_portfolio=20),
        PositionSize(symbol="ETH", percentage_of_portfolio=20),
    ]
    stop_losses = [
        StopLossRule(
            symbol="BTC", percentage_threshold=5,
            sell_percentage=100, trailing=True,
        ),
    ]
    take_profits = [
        TakeProfitRule(
            symbol="BTC", percentage_threshold=10,
            sell_percentage=50, trailing=False,
        ),
    ]
    scaling_rules = [
        ScalingRule(
            symbol="BTC", max_entries=3,
            scale_in_percentage=[50, 25],
        ),
    ]
    # Portfolio-wide, unlike the per-symbol lists above: caps total
    # invested value across every symbol combined.
    exposure_rule = ExposureRule(max_portfolio_percentage=80)
    cooldowns = [
        CooldownRule(
            symbol="BTC", trigger="sell", blocks="buy", bars=12,
        ),
        CooldownRule(trigger="any", blocks="any", bars=2),
    ]
    trading_costs = [
        TradingCost(
            symbol="BTC", fee_percentage=0.1,
            slippage_percentage=0.05,
        ),
    ]

The Rule Catalogue

Attribute	Class	Scope	Purpose
position_sizes	PositionSize	Per-symbol	How much capital to allocate per symbol — fixed amount or percentage of portfolio.
stop_losses	StopLossRule	Per-symbol	Bar-end exit when price drops a fixed or trailing percentage from entry / peak.
take_profits	TakeProfitRule	Per-symbol	Bar-end exit when price rises a fixed or trailing percentage from entry / peak.
scaling_rules	ScalingRule	Per-symbol	Pyramid into winners and partially close — max_entries, scale_in_percentage, scale_out_percentage, optional max_position_percentage cap (caps that symbol's position size).
exposure_rule	ExposureRule	Portfolio-wide	Caps total invested value across every symbol combined — e.g. "never more than 80% invested." Singular, not a list.
cooldowns	CooldownRule	Per-symbol or portfolio-wide	Side-aware signal throttling after fills.
trading_costs	TradingCost	Per-symbol	Fees and slippage applied during fill simulation. Supports pluggable slippage models (volume-based, fixed spread, basis points).

Position sizing vs. exposure: which one do I need?

• "How much do I buy on each entry?" → PositionSize.
• "How big can this one symbol's position grow via pyramiding?" → ScalingRule.max_position_percentage.
• "How much of my whole portfolio can be invested at once, across everything?" → ExposureRule.

All three can be combined: PositionSize sizes an entry, ScalingRule caps how far one symbol can grow, and ExposureRule is the final portfolio-wide backstop that scales every cash-consuming order down (or drops it) if the combined request would breach the cap.

Where Rules Are Enforced

Rule	Vector backtest	Event-driven backtest	Live trading
PositionSize	✅	✅	✅
StopLossRule	✅	✅	✅
TakeProfitRule	✅	✅	✅
ScalingRule	✅	✅	✅
ExposureRule	✅	✅	✅
CooldownRule	✅	✅	✅
TradingCost (fees + slippage)	✅	✅	n/a — broker reports actual cost

Resolution Order

When more than one rule could fire at the same bar, the engine evaluates them in a deterministic order:

1. Stop loss (highest priority — defensive exit).
2. Take profit.
3. CLOSE_LONG signal from generate_signals().
4. SCALE_OUT signal (only if no full close fired).
5. OPEN_LONG signal from generate_signals() — gated by CooldownRule and ScalingRule.cooldown_in_bars.
6. SCALE_IN signal — gated by ScalingRule.max_entries and max_position_percentage.

Within each step, TradingCost is applied to the fill price, and PositionSize (or the relevant scale_in_percentage) determines the order amount. Finally, ExposureRule (if set) scales down or drops any remaining cash-consuming orders so total invested value never exceeds its cap — this runs after sizing, as a portfolio-wide backstop over every symbol's orders for the tick.

See Also

• PositionSize
• StopLossRule
• TakeProfitRule
• ScalingRule
• ExposureRule
• CooldownRule
• TradingCost