docker/sbx-kit-opencode-mixin repository overview

⁠opencode-mixin

OpenCode⁠ as a mixin — the same agent as the opencode⁠ workload kit, packaged as an overlay you layer onto a shell base instead of running as the sandbox's own image.

⁠Usage

sbx run --kit ./opencode-mixin/ <shell-workload>

Or from a git URL targeting this repo:

sbx run --kit "git+https://github.com/docker/sbx-kits-contrib.git#dir=opencode-mixin" <shell-workload>

The base workload keeps its own launch command, so nothing starts the agent for you:

opencode
opencode run "explain this repo"

The OpenCode release is pinned by the kit's version arg, which the descriptor hands to the recipe as OPENCODE_VERSION and also expands into provides: ["opencode@<version>"] — so the kit advertises the release it installs. Move it with --build-arg version=1.2.3 (npm semver, no leading v), and keep it equal to ../opencode⁠'s default.

⁠What it carries

• opencode-ai, installed with npm install -g --prefix /opt/opencode on the same base the workload uses, plus that base's node and a launcher shim on PATH. Unlike this repo's other agent mixins the install relocates cleanly, so the overlay does not have to reproduce a tree at the path it was built at — but the build stage stays on the workload's base, because that is where the corepack hazard is real and where the --version gate means something.
• The seven optional proxy-managed provider credentials, the MCP-gateway registration and the GitHub Copilot seed.

⁠What it deliberately leaves to the base workload

• The launch command. A mixin does not set an entrypoint.
• The apt mirrors and the apt-get update hook. Those refresh the base image's own package sources; a workload owns its base, a mixin does not.
• jq and flock, which the Copilot seed hook shells out to. Every sandbox-templates base ships both; the hook exits without seeding rather than failing if it cannot build the seed.
• The context-file profile. filename: is workload-only; this kit contributes a body through contentFile.
• sbx@1. A mixin's image config does not become the composed image's.

⁠Not declared

Neither agent-sessions@1 nor agent-skills@1, matching the workload: the v2 TCK data omitted promptArgs because no provider credential exists on the runner to answer a prompt, and nothing in this kit ever named a skills directory for opencode.