Mainbrella Introduces Open-Source Sandboxes for AI Coding Agents

Summary

Mainbrella is an open-source sandbox infrastructure project from Andrew, its founder, aimed at AI coding and agent machines. The project was inspired by Cloudflare’s recent container sandbox service and is positioned as an alternative to systems such as e2b.dev and Daytona. It provides similar sandbox services while releasing the code under the GPL-3.0 license. Users can run the software in their own Cloudflare account, but the hosted service does not include a free plan; its base Builder plan costs $5 per month. In an initial startup test, a fresh sandbox reached a usable shell in 381 milliseconds, with all 30 of 30 attempts succeeding at the same reported speed. A separate test started 100 sandboxes simultaneously, averaging 680 milliseconds, with all 100 attempts succeeding and each running on a distinct machine. The founder is seeking feedback, feature requests, and initial paying customers. The post does not provide independent validation, broader comparisons, or details about the workload used in the benchmarks.