Settings

Engine selection and lifecycle, CLI integration, and appearance.

Engine

What the engine that is answering has to say for itself, and — when it is one Hopper manages — buttons to start and stop it. An engine that is not installed yet has nothing to start, so those buttons stay off and the install is offered below instead.

Which engine

Automatic is the default: Apple Containers on a supported Apple silicon Mac, Docker or Podman on Linux or Windows, and whatever is already running as the fallback. When nothing is running, automatic lands on the engine Hopper can supply rather than reporting a missing Docker — Docker is not a requirement on macOS.

Pin one instead and Hopper stays on it. That includes an engine that is not installed yet: pinning the one you are moving to is the point, and its status then says what is left to do about it. A Mac without Apple's container is also offered the install here — reachable while Docker is still connected and working, which is the only moment someone happy on Docker Desktop would think to look.

HOPPER_ENGINE in the environment overrides the saved setting, which is handy for testing without changing what is saved.

Docker CLI

On an Engine API engine, the DOCKER_HOST line that points docker and docker compose at whatever Hopper is showing.

On Apple Containers there is no such line. That runtime publishes no Docker socket, so docker cannot be pointed at it at all — Apple's own container command drives the same runtime Hopper is showing.

Appearance

Dark and light, following the system by default.

What is not here any more

Hopper used to offer a Resources section — CPUs, memory, disk — and a File sharing list. Both belonged to the Linux VM it used to run.

Apple sizes each container's VM when it runs it, and bind-mounts host paths directly, so a global budget has nothing to apply to and there is no share list to keep. Numbers that change nothing are worse than no numbers: they invite you to tune them and then wonder why nothing happened. Both sections are gone.

Where settings live

JSON under ~/.hopper/, written atomically, with a corrupt file backed up rather than silently replaced. Credentials go to the OS keychain instead, one single-line JSON blob per key — the macOS keychain corrupts values containing a newline.

HOPPER_DIR overrides the root, which is what the test suite uses.