Summary · Inside a Sandcastle

Key takeaways

  • A Sandcastle is an isolated, disposable engineering workspace that runs an engineering agent under constrained tools and permissions, uses a branch on a target repository as its input and output surface, and preserves the resulting engineering work as durable Git artifacts.
  • Sandcastle sits between Crossplane and Pico in the academy story: Crossplane composes, Sandcastle constructs, Picos behave.
  • The Sandcastle construction layer is defined by five concerns: isolated workspaces, repo/branch flow, tools and permissions, agent iteration, and artifact boundaries. All Sandcastle-shaped tooling should address these five concerns regardless of the specific sandbox provider it uses.
  • The Sandcastle is safe to be disposable because the workspace, tools, and agent scratch state are all disposable, while the only thing that crosses the artifact boundary is the committed Git branch.
  • The Sandcastle owns the inner iteration loop (inspect → generate → validate → commit) but does not own the surrounding delivery loop (branch → PR → merge → GitOps → Crossplane reconciliation).
  • This wave of the course delivers substantive instruction, a paper Exercise blueprint, and a runnable Sandcastle Lab that links to the reusable Hello World Pico Sandcastle lab under labs/.

What comes next

  • Part 2 — Composing Sandcastles with Crossplane develops how a Crossplane Composition requests engineering work from a Sandcastle. Its first lesson, 01 Composing a Sandcastle request, is runnable end-to-end via the reusable Compose a Sandcastle request lab.
  • Part 3 — Delivering artifacts from a Sandcastle will develop the outer delivery loop and the guardrails that live outside the Sandcastle’s boundary. See Part 3.
  • The reusable Hello Pico artifact you would ultimately have a Sandcastle build is already documented at labs/hello-pico/, and the downstream Kubernetes composition of the same artifact is at labs/hello-pico-on-kubernetes/. Together they define the endpoints a future runnable Sandcastle lab will connect.

Next

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