sandboxes
(3)
Blaxel
Blaxel is a San Francisco cloud infrastructure startup building what its founders call the 'AWS for AI agents.' Its platform runs autonomous agents on isolated microVMs that resume in roughly 25 milliseconds, alongside a distributed agent filesystem, programmable networking, and an AI gateway for model routing and failover. Founded in 2024 by a six-person team of repeat cloud builders who previously sold a data platform to OVHcloud, Blaxel went through Y Combinator's Spring 2025 (X25) batch and raised a $7.3M seed round led by First Round Capital. It already processes millions of agent requests daily across 16 regions.
Modal
Modal is a serverless cloud platform that lets developers run compute-intensive AI and data workloads - inference, training, fine-tuning, batch jobs, and sandboxed code - without managing infrastructure. Built from scratch in Rust with a custom container runtime, file system, and GPU memory snapshotting, it delivers sub-second cold starts and elastic autoscaling from zero to thousands of GPUs, billed by the second. Founded in 2021 by Erik Bernhardsson and Akshat Bubna, the New York-based company reached roughly $300M in annualized revenue and raised a $355M Series C in 2026 at a $4.65B valuation.
Halluminate
Halluminate is a San Francisco startup (Y Combinator S25) building realistic, resettable sandboxes and high-quality datasets to train and evaluate computer- and browser-use AI agents. Its flagship project, Westworld, is a fully simulated internet of synthetic consumer and enterprise apps where agents practice economically valuable tasks - booking flights, financial modeling, reorganizing data - against programmatic verifiers that produce reinforcement-learning reward signals. Customers include foundation-model labs and browser-agent companies.