Onger and Foscari analyze competitive market making as a two-sided pricing game where strategic liquidity providers face a non-strategic informed trader with inelastic demand. Because bid and ask quotes jointly set the market mid-price that determines trade direction, standard equilibrium existence theorems fail and payoffs are non-convex and discontinuous. The authors prove that pure-strategy Nash equilibria exist via a novel fixed-point argument on a midpoint operator, derive a structural linear scaling of spreads with asset volatility, and show that no-internal-regret learning on fine price grids recovers the competitive benchmark as tick size vanishes.

FinRL-X tackles the engineering gap between quantitative trading research and live deployment by introducing a weight-centric modular architecture that unifies data ingestion, strategy composition (selection–allocation–timing–risk), backtesting, and broker execution within a single protocol. The core insight is treating portfolio weights $w_t \in \mathbb{R}^n$ as the sole interface contract, enabling composable strategies without recoding execution logic.