A vx task is one shell command. Not a JavaScript function, not an executor with an options object, not a list of steps. The constraint is what makes remote execution, sandboxing, replay and migration all fall out for free.
The hard part of 'start the tests once the server is up' is knowing when it is up. vx watches a persistent task's output for a pattern, holds its dependents until the line appears, and tears the server down when the run ends.
A task runner spawns processes, and the one thing every process spawner owes you is that they die when it does. Here is the teardown vx runs on a signal, an abort, a timeout or a crashed sibling, and the tests that pin it.
vx watch does not filter filesystem events against your input globs. It re-runs the graph and lets the cache key decide, which is tens of milliseconds for an irrelevant edit and exactly right for a relevant one.
