Project configuration requiring multiple agents at once

Hi,

I'm wondering if there's a better way to support the scenario where the build job requires the use of multiple agents at the same time.

All our work is done on cloud agents and so it's quite costly to keep the agents running when not in use. When a new job starts the test process requires a client to send data to the server, however both the clients and servers will fully saturate the machine.  As such they cannot be run on the same agent.

At the moment we got it to work by having a composite job that does

Start server job A,A finishes as soon as server is done starting up (and agent has a high timeout value)

Start client job B which depends on A so we get the IP of the machine.

Start management job C that depends on both A and B, use the rest call to kill agent A.

I initially wanted to use a detached built for A, but detach builds don't seem to keep A alive till you tell it the job is done.

Is there another approach I could take that's easier?