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Jakob Nicolaus Foerster

66 accepted papers

2026

High Accuracy, Less Talk (HALT): Reliable LLMs through Capability-Aligned Finetuning

ICLR 2026poster

Large Language Models (LLMs) currently respond to every prompt. However, they can produce incorrect answers when they lack knowledge or capability -- a problem known as hallucination. We instead propose post-training an LLM to generate content only when confident in its correctness and to otherwise…

Cited by 0SourceScholar
2026

Programming by Backprop: Learning Behaviour from Symbolic Descriptions

ICLR 2026poster

Large language models (LLMs) are typically trained to acquire behaviours from demonstrations or experience, yet much of their training data consists of symbolic descriptions: instructions, rules, and strategies that specify procedures without examples. We investigate whether LLMs can learn to execut…

Cited by 0SourcecodeScholar
2026

StochasTok: Improving Fine-Grained Subword Understanding in LLMs

ICLR 2026poster

Subword-level understanding is integral to numerous tasks, including understanding multi-digit numbers, spelling mistakes, abbreviations, rhyming, and wordplay. Despite this, current large language models (LLMs) still struggle disproportionally with seemingly simple subword-level tasks, like countin…

Cited by 0SourcecodeScholar
2025

A Clean Slate for Offline Reinforcement Learning

NeurIPS 2025oral

Progress in offline reinforcement learning (RL) has been impeded by ambiguous problem definitions and entangled algorithmic designs, resulting in inconsistent implementations, insufficient ablations, and unfair evaluations. Although offline RL explicitly avoids environment interaction, prior methods…

Cited by 0SourcecodeScholar
2025

ADIOS: Antibody Development via Opponent Shaping

ICML 2025poster

Anti-viral therapies are typically designed to target only the current strains of a virus, a *myopic* response. However, therapy-induced selective pressures drive the emergence of new viral strains, against which the original myopic therapies are no longer effective. This evolutionary response prese…

2025

AI Research Agents for Machine Learning: Search, Exploration, and Generalization in MLE-bench

NeurIPS 2025spotlight

AI research agents are demonstrating great potential to accelerate scientific progress by automating the design, implementation, and training of machine learning models. We focus on methods for improving agents' performance on MLE-bench, a challenging benchmark where agents compete in Kaggle competi…

Cited by 0SourcecodeScholar
2025

Ad-Hoc Human-AI Coordination Challenge

ICML 2025spotlight

Achieving seamless coordination between AI agents and humans is crucial for real-world applications, yet it remains a significant open challenge. Hanabi is a cooperative card game featuring imperfect information, constrained communication, theory of mind requirements, and coordinated action -- makin…

2025

AgentBreeder: Mitigating the AI Safety Risks of Multi-Agent Scaffolds via Self-Improvement

NeurIPS 2025spotlight

Scaffolding Large Language Models (LLMs) into multi-agent systems often improves performance on complex tasks, but the safety impact of such scaffolds has not been thoroughly explored. We introduce AgentBreeder, a framework for multi-objective self-improving evolutionary search over scaffolds. We ev…

Cited by 0SourcecodeScholar
2025

BALROG: Benchmarking Agentic LLM and VLM Reasoning On Games

ICLR 2025poster

Large Language Models (LLMs) and Vision Language Models (VLMs) possess extensive knowledge and exhibit promising reasoning abilities, however, they still struggle to perform well in complex, dynamic environments. Real-world tasks require handling intricate interactions, advanced spatial reasoning, l…

Cited by 9SourcePDFScholar
2025

BTS: Harmonizing Specialized Experts into a Generalist LLM

EMNLP 2025

We present Branch-Train-Stitch (BTS), an efficient and flexible training algorithm for combining independently trained large language model (LLM) experts into a single, capable generalist model. Following Li et al., we start with a single seed language model which is branched into domain-specific (e

Cited by 0SourcePDFScholar
2025

Imagined Autocurricula

NeurIPS 2025poster

Training agents to act in embodied environments typically requires vast training data or access to accurate simulation, neither of which exists for many cases in the real world. Instead, world models are emerging as an alternative–leveraging offline, passively collected data, they make it possible t…

Cited by 0SourceScholar
2025

Improving Regret Approximation for Unsupervised Dynamic Environment Generation

NeurIPS 2025poster

Unsupervised Environment Design (UED) seeks to automatically generate training curricula for reinforcement learning (RL) agents, with the goal of improving generalisation and zero-shot performance. However, designing effective curricula remains a difficult problem, particularly in settings where sma…

Cited by 0SourcecodeScholar
2025

Kinetix: Investigating the Training of General Agents through Open-Ended Physics-Based Control Tasks

ICLR 2025oral

While large models trained with self-supervised learning on offline datasets have shown remarkable capabilities in text and image domains, achieving the same generalisation for agents that act in sequential decision problems remains an open challenge. In this work, we take a step towards this goal b…

2025

LILO: Learning to Reason at the Frontier of Learnability

NeurIPS 2025poster

Reinforcement learning is widely adopted in post-training large language models, especially for reasoning-style tasks such as maths questions. However, as we show, most existing methods will provably fail to learn from questions that are too hard, where the model always fails, or too easy, where the…

Cited by 0SourceScholar
2025

LOB-Bench: Benchmarking Generative AI for Finance - an Application to Limit Order Book Data

ICML 2025poster

While financial data presents one of the most challenging and interesting sequence modelling tasks due to high noise, heavy tails, and strategic interactions, progress in this area has been hindered by the lack of consensus on quantitative evaluation paradigms. To address this, we present **LOB-Ben…

2025

Measuring what Matters: Construct Validity in Large Language Model Benchmarks

NeurIPS 2025poster

Evaluating large language models (LLMs) is crucial for both assessing their capabilities and identifying safety or robustness issues prior to deployment. Reliably measuring abstract and complex phenomena such as `safety' and `robustness' requires strong construct validity, that is, having measures t…

Cited by 0SourceScholar
2025

Meta-Learning Objectives for Preference Optimization

NeurIPS 2025poster

Evaluating preference optimization (PO) algorithms on LLM alignment is a challenging task that presents prohibitive costs, noise, and several variables like model size and hyper-parameters. In this work, we show that it is possible to gain insights on the efficacy of PO algorithm on much simpler ben…

Cited by 0SourceScholar
2025

OvercookedV2: Rethinking Overcooked for Zero-Shot Coordination

ICLR 2025poster

AI agents hold the potential to transform everyday life by helping humans achieve their goals. To do this successfully, agents need to be able to coordinate with novel partners without prior interaction, a setting known as zero-shot coordination (ZSC). Overcooked has become one of the most popular b…

2025

Simplifying Deep Temporal Difference Learning

ICLR 2025spotlight

$Q$-learning played a foundational role in the field reinforcement learning (RL). However, TD algorithms with off-policy data, such as $Q$-learning, or nonlinear function approximation like deep neural networks require several additional tricks to stabilise training, primarily a large replay buffer…

2025

The Automated LLM Speedrunning Benchmark: Reproducing NanoGPT Improvements

NeurIPS 2025poster

Rapidly improving large language models (LLMs) have the potential to assist in scientific progress. One critical skill in this endeavor is the ability to faithfully reproduce existing work. To evaluate the capability of AI agents to reproduce complex code in an active research area, we introduce the…

Cited by 0SourcecodeScholar
2024

Adam on Local Time: Addressing Nonstationarity in RL with Relative Adam Timesteps

NeurIPS 2024poster

In reinforcement learning (RL), it is common to apply techniques used broadly in machine learning such as neural network function approximators and momentum-based optimizers. However, such tools were largely developed for supervised learning rather than nonstationary RL, leading practitioners to ad…

Cited by 0SourcePDFScholar
2024

Artificial Generational Intelligence: Cultural Accumulation in Reinforcement Learning

NeurIPS 2024poster

Cultural accumulation drives the open-ended and diverse progress in capabilities spanning human history. It builds an expanding body of knowledge and skills by combining individual exploration with inter-generational information transmission. Despite its widespread success among humans, the capacity…

2024

BAM! Just Like That: Simple and Efficient Parameter Upcycling for Mixture of Experts

NeurIPS 2024poster

Mixture of Experts (MoE) framework has become a popular architecture for large language models due to its superior performance compared to dense models. However, training MoEs from scratch in a large-scale regime is prohibitively expensive. Previous work addresses this challenge by independently tra…

Cited by 5SourcePDFScholar
2024

Behaviour Distillation

ICLR 2024poster

Dataset distillation aims to condense large datasets into a small number of synthetic examples that can be used as drop-in replacements when training new models. It has applications to interpretability, neural architecture search, privacy, and continual learning. Despite strong successes in supervis…

2024

Can Learned Optimization Make Reinforcement Learning Less Difficult?

NeurIPS 2024spotlight

While reinforcement learning (RL) holds great potential for decision making in the real world, it suffers from a number of unique difficulties which often need specific consideration. In particular: it is highly non-stationary; suffers from high degrees of plasticity loss; and requires exploration t…

2024

Craftax: A Lightning-Fast Benchmark for Open-Ended Reinforcement Learning

ICML 2024spotlight

Benchmarks play a crucial role in the development and analysis of reinforcement learning (RL) algorithms. We identify that existing benchmarks used for research into open-ended learning fall into one of two categories. Either they are too slow for meaningful research to be performed without enormous…

2024

Discovering Preference Optimization Algorithms with and for Large Language Models

NeurIPS 2024poster

Offline preference optimization is a key method for enhancing and controlling the quality of Large Language Model (LLM) outputs. Typically, preference optimization is approached as an offline supervised learning task using manually crafted convex loss functions. While these methods are based on theo…

Cited by 16SourcePDFScholar
2024

Discovering Temporally-Aware Reinforcement Learning Algorithms

ICLR 2024poster

Recent advancements in meta-learning have enabled the automatic discovery of novel reinforcement learning algorithms parameterized by surrogate objective functions. To improve upon manually designed algorithms, the parameterization of this learned objective function must be expressive enough to repr…

2024

EvIL: Evolution Strategies for Generalisable Imitation Learning

ICML 2024poster

Often times in imitation learning (IL), the environment we collect expert demonstrations in and the environment we want to deploy our learned policy in aren't exactly the same (e.g. demonstrations collected in simulation but deployment in the real world). Compared to policy-centric approaches to IL…

2024

Illusory Attacks: Information-theoretic detectability matters in adversarial attacks

ICLR 2024spotlight

Autonomous agents deployed in the real world need to be robust against adversarial attacks on sensory inputs. Robustifying agent policies requires anticipating the strongest attacks possible. We demonstrate that existing observation-space attacks on reinforcement learning agents have a common weakn…

Cited by 5SourcePDFScholar
2024

JaxMARL: Multi-Agent RL Environments and Algorithms in JAX

NeurIPS 2024poster

Benchmarks are crucial in the development of machine learning algorithms, significantly influencing reinforcement learning (RL) research through the available environments. Traditionally, RL environments run on the CPU, which limits their scalability with the computational resources typically availa…

2024

Learning Multi-Agent Communication with Contrastive Learning

ICLR 2024poster

Communication is a powerful tool for coordination in multi-agent RL. But inducing an effective, common language is a difficult challenge, particularly in the decentralized setting. In this work, we introduce an alternative perspective where communicative messages sent between agents are considered a…

Cited by 10SourcePDFScholar
2024

Melting Pot Contest: Charting the Future of Generalized Cooperative Intelligence

NeurIPS 2024poster

Multi-agent AI research promises a path to develop human-like and human-compatible intelligent technologies that complement the solipsistic view of other approaches, which mostly do not consider interactions between agents. Aiming to make progress in this direction, the Melting Pot contest 2023 focu…

Cited by 0SourcePDFScholar
2024

Mixtures of Experts Unlock Parameter Scaling for Deep RL

ICML 2024spotlight

The recent rapid progress in (self) supervised learning models is in large part predicted by empirical scaling laws: a model's performance scales proportionally to its size. Analogous scaling laws remain elusive for reinforcement learning domains, however, where increasing the parameter count of a m…

2024

No Regrets: Investigating and Improving Regret Approximations for Curriculum Discovery

NeurIPS 2024poster

What data or environments to use for training to improve downstream performance is a longstanding and very topical question in reinforcement learning. In particular, Unsupervised Environment Design (UED) methods have gained recent attention as their adaptive curricula promise to enable agents to be…

2024

PARDEN, Can You Repeat That? Defending against Jailbreaks via Repetition

ICML 2024poster

Large language models (LLMs) have shown success in many natural language processing tasks. Despite rigorous safety alignment processes, supposedly safety-aligned LLMs like Llama 2 and Claude 2 are still susceptible to jailbreaks, leading to security risks and abuse of the models. One option to mitig…

2024

Position: Near to Mid-term Risks and Opportunities of Open-Source Generative AI

ICML 2024oral

In the next few years, applications of Generative AI are expected to revolutionize a number of different areas, ranging from science & medicine to education. The potential for these seismic changes has triggered a lively debate about potential risks and resulted in calls for tighter regulation, in p…

Cited by 9SourcePDFScholar
2024

Rainbow Teaming: Open-Ended Generation of Diverse Adversarial Prompts

NeurIPS 2024poster

As large language models (LLMs) become increasingly prevalent across many real-world applications, understanding and enhancing their robustness to adversarial attacks is of paramount importance. Existing methods for identifying adversarial prompts tend to focus on specific domains, lack diversity, o…

Cited by 71SourcePDFScholar
2024

ReLU to the Rescue: Improve Your On-Policy Actor-Critic with Positive Advantages

ICML 2024poster

This paper proposes a step toward approximate Bayesian inference in on-policy actor-critic deep reinforcement learning. It is implemented through three changes to the Asynchronous Advantage Actor-Critic (A3C) algorithm: (1) applying a ReLU function to advantage estimates, (2) spectral normalization…

2024

Recurrent Reinforcement Learning with Memoroids

NeurIPS 2024poster

Memory models such as Recurrent Neural Networks (RNNs) and Transformers address Partially Observable Markov Decision Processes (POMDPs) by mapping trajectories to latent Markov states. Neither model scales particularly well to long sequences, especially compared to an emerging class of memory models…

2024

Refining Minimax Regret for Unsupervised Environment Design

ICML 2024poster

In unsupervised environment design, reinforcement learning agents are trained on environment configurations (levels) generated by an adversary that maximises some objective. Regret is a commonly used objective that theoretically results in a minimax regret (MMR) policy with desirable robustness guar…

2024

Select to Perfect: Imitating desired behavior from large multi-agent data

ICLR 2024poster

AI agents are commonly trained with large datasets of demonstrations of human behavior. However, not all behaviors are equally safe or desirable. Desired characteristics for an AI agent can be expressed by assigning desirability scores, which we assume are not assigned to individual behaviors but to…

Cited by 3SourcePDFScholar
2024

The Edge-of-Reach Problem in Offline Model-Based Reinforcement Learning

NeurIPS 2024poster

Offline reinforcement learning (RL) aims to train agents from pre-collected datasets. However, this comes with the added challenge of estimating the value of behaviors not covered in the dataset. Model-based methods offer a potential solution by training an approximate dynamics model, which then all…

Cited by 1SourcePDFScholar
2023

Adversarial Diversity in Hanabi

ICLR 2023top-25%

Many Dec-POMDPs admit a qualitatively diverse set of ''reasonable'' joint policies, where reasonableness is indicated by symmetry equivariance, non-sabotaging behaviour and the graceful degradation of performance when paired with ad-hoc partners. Some of the work in diversity literature is concerned…

Cited by 19SourcePDFScholar
2023

Cheap Talk Discovery and Utilization in Multi-Agent Reinforcement Learning

ICLR 2023poster

By enabling agents to communicate, recent cooperative multi-agent reinforcement learning (MARL) methods have demonstrated better task performance and more coordinated behavior. Most existing approaches facilitate inter-agent communication by allowing agents to send messages to each other through fre…

Cited by 7SourcePDFScholar
2023

Discovering General Reinforcement Learning Algorithms with Adversarial Environment Design

NeurIPS 2023poster

The past decade has seen vast progress in deep reinforcement learning (RL) on the back of algorithms manually designed by human researchers. Recently, it has been shown that it is possible to meta-learn update rules, with the hope of discovering algorithms that can perform well on a wide range of RL…

2023

Learning Intuitive Policies Using Action Features

ICML 2023poster

An unaddressed challenge in multi-agent coordination is to enable AI agents to exploit the semantic relationships between the features of actions and the features of observations. Humans take advantage of these relationships in highly intuitive ways. For instance, in the absence of a shared language…

Cited by 1SourcePDFScholar
2023

MAESTRO: Open-Ended Environment Design for Multi-Agent Reinforcement Learning

ICLR 2023poster

Open-ended learning methods that automatically generate a curriculum of increasingly challenging tasks serve as a promising avenue toward generally capable reinforcement learning agents. Existing methods adapt curricula independently over either environment parameters (in single-agent settings) or c…

Cited by 41SourcePDFScholar
2023

Perfectly Secure Steganography Using Minimum Entropy Coupling

ICLR 2023poster

Steganography is the practice of encoding secret information into innocuous content in such a manner that an adversarial third party would not realize that there is hidden meaning. While this problem has classically been studied in security literature, recent advances in generative models have led t…

2023

SMACv2: An Improved Benchmark for Cooperative Multi-Agent Reinforcement Learning

NeurIPS 2023poster

The availability of challenging benchmarks has played a key role in the recent progress of machine learning. In cooperative multi-agent reinforcement learning, the StarCraft Multi-Agent Challenge (SMAC) has become a popular testbed for centralised training with decentralised execution. However, aft…

2023

Similarity-based cooperative equilibrium

NeurIPS 2023poster

As machine learning agents act more autonomously in the world, they will increasingly interact with each other. Unfortunately, in many social dilemmas like the one-shot Prisoner’s Dilemma, standard game theory predicts that ML agents will fail to cooperate with each other. Prior work has shown that…

Cited by 7SourcePDFScholar
2023

Structured State Space Models for In-Context Reinforcement Learning

NeurIPS 2023poster

Structured state space sequence (S4) models have recently achieved state-of-the-art performance on long-range sequence modeling tasks. These models also have fast inference speeds and parallelisable training, making them potentially useful in many reinforcement learning settings. We propose a modif…

2022

A Fine-Tuning Approach to Belief State Modeling

ICLR 2022poster

We investigate the challenge of modeling the belief state of a partially observable Markov system, given sample-access to its dynamics model. This problem setting is often approached using parametric sequential generative modeling methods. However, these methods do not leverage any additional comput…

Cited by 13SourcePDFScholar
2022

Discovered Policy Optimisation

NeurIPS 2022accept

Tremendous progress has been made in reinforcement learning (RL) over the past decade. Most of these advancements came through the continual development of new algorithms, which were designed using a combination of mathematical derivations, intuitions, and experimentation. Such an approach of creati…

Cited by 93SourcePDFScholar
2022

Equivariant Networks for Zero-Shot Coordination

NeurIPS 2022accept

Successful coordination in Dec-POMDPs requires agents to adopt robust strategies and interpretable styles of play for their partner. A common failure mode is symmetry breaking, when agents arbitrarily converge on one out of many equivalent but mutually incompatible policies. Commonly these examples…

2022

Grounding Aleatoric Uncertainty for Unsupervised Environment Design

NeurIPS 2022accept

Adaptive curricula in reinforcement learning (RL) have proven effective for producing policies robust to discrepancies between the train and test environment. Recently, the Unsupervised Environment Design (UED) framework generalized RL curricula to generating sequences of entire environments, leadin…

Cited by 19SourcePDFScholar
2022

Influencing Long-Term Behavior in Multiagent Reinforcement Learning

NeurIPS 2022accept

The main challenge of multiagent reinforcement learning is the difficulty of learning useful policies in the presence of other simultaneously learning agents whose changing behaviors jointly affect the environment's transition and reward dynamics. An effective approach that has recently emerged for…

2022

Nocturne: a scalable driving benchmark for bringing multi-agent learning one step closer to the real world

NeurIPS 2022accept

We introduce \textit{Nocturne}, a new 2D driving simulator for investigating multi-agent coordination under partial observability. The focus of Nocturne is to enable research into inference and theory of mind in real-world multi-agent settings without the computational overhead of computer vision an…

2022

Proximal Learning With Opponent-Learning Awareness

NeurIPS 2022accept

Learning With Opponent-Learning Awareness (LOLA) (Foerster et al. [2018a]) is a multi-agent reinforcement learning algorithm that typically learns reciprocity-based cooperation in partially competitive environments. However, LOLA often fails to learn such behaviour on more complex policy spaces para…

2022

Self-Explaining Deviations for Coordination

NeurIPS 2022accept

Fully cooperative, partially observable multi-agent problems are ubiquitous in the real world. In this paper, we focus on a specific subclass of coordination problems in which humans are able to discover self-explaining deviations (SEDs). SEDs are actions that deviate from the common understanding o…

Cited by 1SourcePDFScholar
2021

K-level Reasoning for Zero-Shot Coordination in Hanabi

NeurIPS 2021poster

The standard problem setting in cooperative multi-agent settings is \emph{self-play} (SP), where the goal is to train a \emph{team} of agents that works well together. However, optimal SP policies commonly contain arbitrary conventions (``handshakes'') and are not compatible with other, indepe…

Cited by 41SourcePDFScholar
2021

Neural Pseudo-Label Optimism for the Bank Loan Problem

NeurIPS 2021poster

We study a class of classification problems best exemplified by the \emph{bank loan} problem, where a lender decides whether or not to issue a loan. The lender only observes whether a customer will repay a loan if the loan is issued to begin with, and thus modeled decisions affect what data is avail…

Cited by 8SourcePDFScholar
2021

Replay-Guided Adversarial Environment Design

NeurIPS 2021poster

Deep reinforcement learning (RL) agents may successfully generalize to new settings if trained on an appropriately diverse set of environment and task configurations. Unsupervised Environment Design (UED) is a promising self-supervised RL paradigm, wherein the free parameters of an underspecified en…

Cited by 119SourcePDFScholar