# StratFormer: Adaptive Opponent Modeling and Exploitation in Imperfect-Information Games

Source: [StratFormer: Adaptive Opponent Modeling and Exploitation in Imperfect-Information Games](<https://www.sota2.com/research/paper/69f190c655a3c32af89fbcd7>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2026-04-30T05:00:12.461Z

Authors: Andy Caen, Mark H.M. Winands, Dennis J.N.J. Soemers

Published: 2026-04-28T16:03:14.000Z

## Abstract

We present StratFormer, a transformer-based meta-agent that learns to simultaneously model and exploit opponents in imperfect-information games through a two-phase curriculum. The first phase trains an opponent modeling head to identify behavioral patterns from action histories while the agent plays a game-theoretic optimal (GTO) policy. The second phase progressively shifts the policy toward best-response (BR) exploitation, guided by a per-opponent regularization schedule tied to exploitability. Our architecture introduces dual-turn tokens -- feature vectors constructed at both agent and opponent decision points -- coupled with bucket-rate features that encode opponent tendencies across five strategic contexts. On Leduc Hold'em, a small poker variant with six cards and two betting rounds, we test against six opponent archetypes at two strength levels each, with exploitability ranging from 0.15 to 1.26 Big Blinds (BB) per hand. StratFormer achieves an average exploitation gain of +0.106 BB per hand over GTO, with peak gains of +0.821 against highly exploitable opponents, while maintaining near-equilibrium safety.

## Recorded benchmark results

A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage.

- [Opponent Exploitation on Leduc Hold'em (3k hands, paired seeds, held-out)](<https://www.sota2.com/research/sota/opponent-exploitation-on-leduc-hold-em-3k-hands-paired-seeds-held-out.md>): Opponent Exploitation; Leduc Hold'em 3,000 hands × 3 trials, paired seeds (Held-out); Gain: 0.821.

## Original sources and implementation

[Original paper](<https://arxiv.org/abs/2604.25796>)

[PDF](<https://arxiv.org/pdf/2604.25796.pdf>)