Field name changed from ApiVersion to APIVersion in Docker 29.0.0 JSON output

[jannst]

Description

Hello,

I noticed that in the output of the command
docker version --format '{{ json . }}' (Docker version 29.0.0),
the field Server->APIVersion was renamed from Server->ApiVersion (as it appeared in version 28.5.2).

This change caused the Ansible module community.docker.docker_stack to fail with error message Cannot determine Docker Daemon information. Are you maybe using podman instead of docker?, since it expects the API version field to be named ApiVersion instead of APIVersion see here.

Below is the output of docker version --format '{{ json . }}' for both version 29.0.0 and 28.5.2, showing that the naming of the Server->ApiVersion field has changed.

Could it be that this renaming was accidental? I don’t see a clear benefit to the change, and it breaks existing programs that rely on the previous field name.

Version 29.0.0

{
  "Client": {
     ....
  },
  "Server": {
    "Platform": {
      "Name": "Docker Engine - Community"
    },
    "Version": "29.0.0",
    "APIVersion": "1.52",
    "MinAPIVersion": "1.44",
    "Os": "linux",
    "Arch": "amd64",
    "Experimental": false,
    "Components": [
       .....
     ]
  }
}

Version 28.5.2

{
  "Client": {
     ....
  },
  "Server": {
    "Platform": {
      "Name": "Docker Engine - Community"
    },
    "Components": [
      .....
    ],
    "Version": "28.5.2",
    "ApiVersion": "1.51",
    "MinAPIVersion": "1.24",
    "GitCommit": "89c5e8f",
    "GoVersion": "go1.25.3",
    "Os": "linux",
    "Arch": "amd64",
    "KernelVersion": "6.12.41+deb13-cloud-amd64",
    "BuildTime": "2025-11-05T14:43:33.000000000+00:00"
  }
}

Reproduce

docker version --format '{{ json . }}'

Expected behavior

No response

docker version

as shown above

docker info

as shown above

Additional Info

No response

[felixfontein]

The change was vendored in in #6593, and apparently comes from moby/moby#51233.

[felixfontein]

Ref: moby/moby#51476

[robmry]

Thank you for reporting - as it's a daemon issue, not CLI, let's mark this as a duplicate to keep the discussion in one place.