Hammerspoon script to disable bluetooth when the computer is put to sleep. Requires `blueutil` to be installed (`brew install blueutil`).

bluetooth_sleep.lua

require "string"

function checkBluetoothResult(rc, stderr, stderr)
    if rc ~= 0 then
        print(string.format("Unexpected result executing `blueutil`: rc=%d stderr=%s stdout=%s", rc, stderr, stdout))
    end
end

function bluetooth(power)
    print("Setting bluetooth to " .. power)
    local t = hs.task.new("/usr/local/bin/blueutil", checkBluetoothResult, {"--power", power})
    t:start()
end

function f(event)
    if event == hs.caffeinate.watcher.systemWillSleep then
        bluetooth("off")
    elseif event == hs.caffeinate.watcher.screensDidWake then
        bluetooth("on")
    end
end

watcher = hs.caffeinate.watcher.new(f)
watcher:start()

could i extend this to discover and connect to a device when the macbook reopens?

Yup, see blueutil which this uses: https://github.com/toy/blueutil

Great stuff, thanks for the inspiration!

Brew installs it in /opt/homebrew/bin/blueutil for me :)

Brew installs it in /opt/homebrew/bin/blueutil for me :)

Correct, /usr/local/bin for Intel Macs, and /opt/homebrew/bin for M1 Macs