DiffLOB: Diffusion Models for Counterfactual Generation in Limit Order Books

TL;DR

DiffLOB is a diffusion-based generative model that produces controllable and counterfactual limit order book trajectories conditioned on future market regimes, aiding stress testing and scenario analysis.

Contribution

It introduces DiffLOB, a novel regime-conditioned diffusion model for counterfactual LOB generation, enabling explicit control over future market conditions.

Findings

Achieves realistic and controllable LOB trajectory generation.

Demonstrates consistent counterfactual changes with regime interventions.

Improves downstream market regime prediction using synthetic data.

Abstract

Modern generative models for limit order books (LOBs) can reproduce realistic market dynamics, but remain fundamentally passive: they either model what typically happens without accounting for hypothetical future market conditions, or they require interaction with another agent to explore alternative outcomes. This limits their usefulness for stress testing, scenario analysis, and decision-making. We propose \textbf{DiffLOB}, a regime-conditioned \textbf{Diff}usion model for controllable and counterfactual generation of \textbf{LOB} trajectories. DiffLOB explicitly conditions the generative process on future market regimes--including trend, volatility, liquidity, and order-flow imbalance, which enables the model to answer counterfactual queries of the form: ``If the future market regime were X instead of Y, how would the limit order book evolve?'' Our systematic evaluation framework for counterfactual LOB generation consists of three criteria: (1) \textit{Controllable Realism}, measuring how well generated trajectories can reproduce marginal distributions, temporal dependence structure and regime variables; (2) \textit{Counterfactual validity}, testing whether interventions on future regimes induce consistent changes in the generated LOB dynamics; (3) \textit{Counterfactual usefulness}, assessing whether synthetic counterfactual trajectories improve downstream prediction of future market regimes.