Docker versions

The app talks to Docker two ways: the Engine API through the official Go SDK, and the docker compose CLI as a subprocess for project deploys. Both move, and you run whatever your distro ships — so here is what is actually tested, not what is hoped for.

	Version
Minimum Engine API	1.43 (Docker Engine 24)
Tested Engine majors	24, 25, 26, 27, 28, 29 (nightly; see the workflow runs for the current result)
Tested Engine patches	a handful of exact patch releases of the newest majors are also pinned and tested nightly, independent of the floating major tags (see the workflow runs for the current exact versions)
Compose	the docker compose plugin, v2 or newer (legacy docker-compose v1 is not supported); a handful of recent v2 releases are pinned and tested nightly (see the workflow runs)
Client SDK	pinned in go.mod, negotiated down to the daemon at connect time

The SDK negotiates the API version on its own (it does so by default), so a newer client speaks whatever the daemon understands — you do not need to match versions. Below API 1.43 the app is neither tested nor claimed to work.

These numbers are measured, not remembered: the compatibility workflow runs the app’s whole Docker integration suite against a pinned docker:NN-dind for each major, nightly and on demand, and prints the negotiated API version — plus the Compose version it ran with — for every run. Three axes are pinned: every Engine major is tested against the newest of a small set of recent Compose releases, the newest Engine major is additionally tested against the older ones in that set, and a handful of exact Engine patch releases (docker:X.Y.Z-dind, not just docker:NN-dind) are pinned and tested too — since the plain major tag always floats to whatever patch is newest when it’s pulled, it alone can’t prove a specific patch is good, only that the latest one currently is. So the matrix answers “which daemons work”, “which recent Compose releases work”, and “does this exact Engine patch work”, short of a full Engine × Compose cross product. Reproduce any row locally:

docker run -d --name dc-compat --privileged -e DOCKER_TLS_CERTDIR="" \
  -p 127.0.0.1:12375:2375 docker:24-dind --host=tcp://0.0.0.0:2375 --tls=false
DC_COMPAT_DOCKER=tcp://127.0.0.1:12375 DOCKER_HOST=tcp://127.0.0.1:12375 \
  go test -count=1 -run 'TestIntegration|TestCompat' ./internal/docker/

Both variables matter: DC_COMPAT_DOCKER points the app at the daemon, DOCKER_HOST points the Compose CLI at the same one. Set only the first and the Compose tests deploy to your own daemon and hang waiting for containers that started somewhere else.