A build configuration can be made dependent on the artifacts or sources of builds of some other build configurations.
For snapshot dependencies, TeamCity will run all dependent builds on the sources taken at the moment the build they depend on starts.
For artifact dependencies, before a build is started, all artifacts this build depends on will be downloaded and placed in their configured target locations and then will be used by the build.
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The dependencies of the build can later be viewed on the build results page — the Dependencies tab. This tab also displays indirect dependencies: for example, if build A depends on build B which depends on builds C and D, then these builds C and D are indirect dependencies for build A.