LangSmith Sandboxes (Private Preview): Sub-1-Second Isolated Code Execution for Agents — Credentials Never Touch Runtime, Docker BYO, WebSocket Sessions

LangChain Blog·high signal

LangChain launched LangSmith Sandboxes in private preview, providing managed secure runtimes for agent-generated code with sub-1-second spin-up, long-running WebSocket sessions, and bring-your-own Docker images. External service credentials are brokered through a managed authentication proxy so they never enter the sandbox execution environment; deepagents v0.4 integrates directly so agents get filesystem tools and arbitrary shell execution without host system exposure. This is the first integrated sandbox primitive for LangGraph-based agent workflows.