TFS 2015.3 custom build step not sending variables to the script
Apparently I wasn't following closely enough... I missed the warning on this page:
Words of warning
Tasks can be versioned, use this to your advantage. All build definitions use the latest available version of a specific task, you can’t change this behavior from the web interface, so always assume the latest version is being used.
If you don’t change the version number of your task when updating it, the build agents that have previously used your task will not download the newer version because the version number is still the same. This means that if you change the behavior of your task, you should always update the version number!
Once I got that all straightened out, everything worked fine.
Possibly the examples accepting inputs in the param section are out of date. It appears that you now need to use the Vsts-task-lib commands from your PowerShell script to get the input parameters.
[CmdletBinding()]param()$myParam = Get-VstsInput -Name myParam -Require