Glossary

Terms used across the Sandcastle course. Course-specific vocabulary lives here so lessons can link to a single definition instead of redefining terms. For Pico-side vocabulary (Rule, Parser, Composer, Pico) see the Pico course glossary; for Crossplane vocabulary (XRD, XR, Composition, Managed Resource) see the Crossplane course glossary.

Artifact boundary

The line between what a Sandcastle produces (durable, versioned Git artifacts such as Pico definitions and rulesets) and what happens elsewhere (runtime execution, control-plane reconciliation). The artifact boundary is what makes a Sandcastle disposable while its outputs remain durable.

Engineering agent

The actor that performs work inside a Sandcastle — typically an AI coding agent, but the same abstraction covers a human developer constrained to the same isolated workspace. The agent operates on the Sandcastle’s repo/branch with the Sandcastle’s tools and permissions.

Isolated workspace

The Sandcastle’s core primitive: a self-contained working directory in which an engineering agent can read, write, run commands, and iterate without any effect on the outside world. When the workspace is torn down, only the committed artifacts survive.

Repo/branch flow

The Git shape a Sandcastle uses to move work in and out: clone a target repository into the isolated workspace, work on a dedicated branch, commit iteratively, and hand back the branch (or a pull request) as the durable output. The repo/branch flow is how the Sandcastle preserves engineering intent across its disposable lifecycle.

Sandbox provider

A pluggable back-end that supplies the isolated workspace — for example a local Docker container, a Podman container, a Vercel sandbox, or a custom provider. The choice of sandbox provider affects performance and cost but does not change what a Sandcastle is.

Sandcastle

A bounded, disposable engineering environment that safely runs an engineering agent against an isolated workspace, controls what tools and permissions the agent has, and captures the resulting engineering work as durable Git artifacts. The name is intentional: the castle is temporary; the sand-shaping performed inside it is preserved as committed artifacts.

Tools and permissions

The constrained set of executables, network access, secrets, and file system reach the engineering agent is allowed to use inside the Sandcastle. Constraining tools and permissions is what makes it safe to run an agent on production-adjacent work.