Docker Sandboxes: Kits (v3 descriptors)

Overview

A kit extends a sandbox with a tool, an agent, credentials, or policy. In v3 a kit is one OCI image: its layers are the content, and a manifest annotation carries the descriptor, which says what the kit offers, what it needs from the host as typed capability requests, and what it needs from other kits. An engine that does not read the annotation runs it as an ordinary image.

The source is a <kit>.yaml whose first line is # syntax=docker/sandbox-kit:3 with schemaVersion: "3", usually beside a <kit>.dockerfile content recipe. The kinds are workload, mixin, and set (a list of other kits). Build and check with docker buildx build, kit-tck validate, sbx kit inspect, and a real sbx run composition.

Scope and guardrails: