Agent master data synchronization

How exactly is data shared between agent and master? I can see right away that build log is synced every couple of seconds in batches(it is not line by line, but in some number of lines at once) but what about status and problems?

The problem i'm struggling with:

I have a step that is running always. When some previous steps fail, the last block is supposed to catch that happened. I want to first do an API request to get the status, so i can get either SUCCESS or FAILURE. Does teamcity assure, that in the moment i start last step and some previous failed I will always get FAILURE in response?