Amazon's Sandman served agentic RL sandboxes on shared Kubernetes, holding 11,858 concurrent environments and creating 3.1 million sandboxes for four SWE-bench Verified campaigns in October
AspireAI community · arXiv (Amazon)
Agentic reinforcement learning needs repeated tool calls inside task-specific environments, and a single training job can create thousands of them in bursts while sharing a cluster with other jobs. Sandman is the sandbox service Amazon built and operates for exactly that: each sandbox is a Kubernetes pod with a small daemon mounted into an unmodified task image, files and processes persist across calls, and the service handles creation, readiness and cleanup. In a scale test it held 11,858 concurrent tiny sandboxes, and four production SWE-bench Verified training campaigns created 3.1 million sandboxes during October 2026. The paper is a systems case study with the trade-offs and operational lessons rather than a quality benchmark, and the daemon, provider and pool are stated to be on the way to open source.
Read the story and explore more from the AspireAI community.
Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.