Concurrency as a share of your CPUs
--concurrency 50% means half your cores, on any machine.
By default vx runs as many tasks at once as you have cores, capped by a container’s CPU quota. --concurrency takes a count or a percentage, so one CI config fits runners of any size.
Cache restores are disk work, not CPU work. They run on their own lane, up to twice the limit, so a warm run is not held back by the cap you set for builds.
