export-image (cli) works, while exportImage (golang) fails | Dagger | Page 1

I have a container:

func (m *Headway) TileserverInitImage(ctx context.Context,
    // +defaultPath="./services/tileserver"
    serviceDir *dagger.Directory,
) *dagger.Container {
    return downloadContainer().
        WithFile("/app/init.sh", serviceDir.File("init.sh")).
        WithDefaultArgs([]string{"/app/init.sh"})
}

Which I can successfully build and export from the cli:
🎉 Success:

▶ tileserver-init-image | export-image tileserver-init 0.5s

I want to export several similar containers, and so I thought to orchestrate this I'd need to call exportImage from golang, like so:

func (m *Headway) ExportTileserverInitImage(ctx context.Context,
    // +defaultPath="./services/tileserver"
    serviceDir *dagger.Directory,
) error {
    container := m.TileserverInitImage(ctx, serviceDir)
    return container.ExportImage(ctx, "tileserver-init")
}

But when I invoke export-tileserver-init-image I get this error:

▼ export-tileserver-init-image 1.1s ERROR r jump ↴
╰─▼ Headway.exportTileserverInitImage(
  │ ┆ serviceDir: Host.directory(path: "/Users/mkirk/src/headwaymaps/headway/services/tileserver", exclude: [], noCach
  │ ): Void 1.0s ERROR
  ! client has no supported api for loading image
  ├─● Directory.file(path: "init.sh"): File! 0.0s
  │ 
  ├─● container: Container! 0.0s
  ├─$ .from(address: "debian:bookworm-slim"): Container! 0.7s CACHED
  ├─● .withWorkdir(path: "/data"): Container! 0.0s
  ├─$ .withExec(
  │   ┆ args: ["sh", "-c", "apt-get update && apt-get install -y --no-install-recommends wget ca-certificates zstd && 
  │   ): Container! 0.0s CACHED
  ├─$ .withFile(
  │   ┆ path: "/app/init.sh"
  │   ┆ source: Directory.file(path: "init.sh"): File!
  │   ): Container! 0.0s CACHED
  ├─● .withDefaultArgs(args: ["/app/init.sh"]): Container! 0.0s
  ╰─✘ .exportImage(name: "tileserver-init"): Void! 0.0s ERROR
    ! client has no supported api for loading image

Am I holding it wrong?

#export-image (cli) works, while exportImage (golang) fails