LangSmith Sandboxes alternatives for secure AI code execution

LangSmith Sandboxes, launched in private preview in March 2026, provide isolated execution environments for running agent-generated code securely, leveraging hardware-virtualized microVMs to ensure robust isolation. They integrate seamlessly with the LangSmith platform, supporting features like sandbox templates, pre-provisioned warm pools, and persistent state across sessions, with native integration with LangChain's Deep Agents framework. Key considerations for choosing sandbox alternatives include isolation model, deployment flexibility, GPU availability, session limits, and pricing. Among the alternatives, Northflank offers a comprehensive platform with support for ephemeral and persistent environments, self-serve BYOC deployment into major cloud providers, and on-demand GPU allocation. E2B focuses on AI agent code execution with Firecracker microVMs but requires contacting sales for BYOC access and doesn't support GPUs. Modal provides serverless compute with configurable sandbox timeouts and GPU support, while Fly.io Sprites offer hardware-isolated environments without BYOC or GPU options. CodeSandbox offers browser and VM sandbox solutions with unlimited session limits and BYOC available only on Enterprise plans. Each platform presents unique capabilities suited for different requirements, emphasizing the importance of evaluating factors like isolation approach and cost implications before selecting a sandbox solution.