arXiv Machine Learning

Learning from Unreliable Trajectories: Adversarially-Robust Federated Q-Learning

The paper introduces Robust Async-Fed-Q, an epoch‑based federated Q‑learning algorithm that combines variance‑reduced Bellman operator estimation with robust server aggregation. It provides high‑probability finite‑time guarantees showing that honest agents retain sample‑efficiency benefits even when some agents act adversarially, with the adversarial impact diminishing as honest data grows. The authors also present matching lower bounds, extend the framework to single‑trajectory sampling and heterogeneous coverage, and improve communication complexity for asynchronous federated Q‑learning.

arXiv Machine Learning
Sep 18

Robust Federated Q-Learning with Almost No Communication

The paper introduces Robust Fed-Q, a federated Q‑learning algorithm designed for settings where multiple agents interact with a shared Markov Decision Process and communicate through a central server. It combines model‑based and model‑free reinforcement learning techniques with a median‑of‑means strategy from robust statistics to handle a small fraction of adversarial agents. The authors prove that Robust Fed-Q achieves exact convergence to the optimal value function with high probability, attains near‑optimal finite‑time rates that benefit from collaboration, and requires only “~O(1)” communication rounds per guarantee.

By Sreejeet Maity, Aritra Mitra
arXiv AI
Sep 2

Provably Efficient Federated Reinforcement Learning with Linear Function Approximation and Logarithmic Communication Cost

The paper introduces Fed‑LSVI, a federated online reinforcement learning algorithm that uses linear function approximation in episodic Markov decision processes. It achieves a regret bound of ≥O(√{Md^3H^4T}) while only exchanging compressed sufficient statistics, thereby meeting privacy constraints. The method reduces communication cost to logarithmic in the number of episodes, a marked improvement over previous approaches that required linear communication.

By Zihang Liang, Haochen Zhang, Lingzhou Xue
arXiv Machine Learning
Oct 9

When to Intervene? State-Aware Sparse Manipulation in Federated Reinforcement Learning

The paper introduces the Viability‑constrained Behavioral Steering Attack (V‑BSA), a new attack strategy for federated reinforcement learning that targets the timing of interventions rather than just the construction of malicious updates. By selecting sparse intervention states based on local policy uncertainty and applying envelope‑constrained steering, V‑BSA can significantly degrade performance on discrete‑action benchmarks while using far fewer interventions than traditional dense poisoning attacks. The study demonstrates that the specific states at which interventions occur constitute a distinct and critical dimension of robustness in sequential decision‑making settings.

By Shutong Zheng, Sijia Chen
arXiv Machine Learning
Sep 30

Byzantine-Robust Federated Representation Learning

arXiv:2609.36660v1 Announce Type: new Abstract: We study federated learning (FL) with adversarial clients, where the goal is to minimize the average loss of the honest (non-adversarial) clients witho...

By Leonardo F. Toso, James Anderson, Rafael Pinot, Nirupam Gupta
arXiv Machine Learning
Sep 14

Robust Policy Optimization via Adversarial Importance Sampling

The paper introduces Adversarial Importance Sampling (Advis), a technique that leverages importance sampling over standard training trajectories to estimate and optimize worst‑case returns without extra environment interactions or auxiliary networks, thereby capturing long‑term robustness. It also presents advrl, a modular PyTorch library that consolidates existing robustness methods and adversarial attacks into single‑file implementations for easier prototyping and reproducible evaluation. Finally, the authors highlight that optimal adversarial hyperparameters do not transfer across agents, prompting evaluation against a broader set of attackers (6–14× more configurations) and demonstrate the effectiveness of their approach on continuous control tasks.

By Amine Andam, Jamal Bentahar, Mustapha Hedabou