TeamCity allows me to report back from my MsBuild script using the ##teamcity interaction. I can use this to tell TeamCity that the build has FAILED, or ind
Since Teamcity 8.1 (Source) it is possible to Cancel the Build via REST API.
Taken from the 9.x Documentation, cancelling a currently running build
curl -v -u user:password --request POST "http://teamcity:8111/app/rest/builds/" --data "" --header "Content-Type: application/xml"