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Sandcastle is an open source TypeScript library for orchestrating coding agents in isolated sandboxes. Matt Pocock introduces it as a way to run unattended development workflows without repeated permission requests. He describes problems he encountered with Docker sandboxes, then demonstrates Sandcastle using Docker as its sandbox provider.
The setup selects Claude Code, GitHub issues as the backlog manager, and a parallel planner template with a review step. A Sandcastle label determines which issues agents can pick up. The generated Dockerfile installs system dependencies, the GitHub CLI and Claude Code. The demonstrated configuration requires an Anthropic API key and a GitHub token; Pocock points subscription users to a separate issue for advice.
An example ticket requests a TypeScript CLI with Commander, Vitest, type checking and CI. The planner selects unblocked issues, implementers work in separate sandboxes and branches, and a reviewer checks their changes. A merger agent handles the branches and potential conflicts. In the demonstrated run, it performs type checks, merges the branch and closes the issue.
Prompts and orchestration remain editable TypeScript and Markdown. Pocock also explains how Codex can replace Claude Code for individual steps and how workflows can produce pull requests. This is an AI agent orchestration tutorial; it does not demonstrate local model inference or offline operation.
