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• I've read the contributing guidelines and wholeheartedly agree

I've found a bug and checked that ...

• ... the documentation does not mention anything about my problem
• ... there are no open or closed issues that are related to my problem

Description

In cli output of docker buildx ls an asterisk (*) next to a builder name indicates the selected builder.
In a json output, docker buildx ls --format=json, there is no such field, and there is no way to determine the selected one.

Expected behaviour

Json output has a field indicating if a builder is a selected one (see line 3).

{
  "Name": "default",
  "Selected": true,
  "Driver": "docker",
  "LastActivity": "2025-01-01T00:00:00Z",
  "Dynamic": false,
  "Nodes": [ ... ]
}

Actual behaviour

Json output does not have a "Selected" field in any way.

{
  "Name": "default",
  "Driver": "docker",
  "LastActivity": "2025-01-01T00:00:00Z",
  "Dynamic": false,
  "Nodes": [ ... ]
}

Buildx version

github.com/docker/buildx v0.23.0 28c90ea

Docker info

Builders list

NAME/NODE        DRIVER/ENDPOINT                   STATUS    BUILDKIT   PLATFORMS
multiarch        docker-container
 \_ multiarch0    \_ ssh://user@192.168.1.1        running   v0.20.2    linux/amd64 (+2), linux/386
 \_ multiarch1    \_ unix:///var/run/docker.sock   running   v0.20.2    linux/arm64
default*         docker
 \_ default       \_ default                       running   v0.21.0    linux/arm64

Configuration

FROM scratch

Build logs

Additional info

No response