What happens to the build agents if the TeamCity server was downgraded

Question

The TeamCity server was downgraded to an older version. For example, it was restored from the backup. What happens with the build agents that have already been updated to the newer version? Do they need to be downgraded manually?

Answer

TeamCity agents connected to the server and correctly installed are automatically updated to the version corresponding to the server. This occurs for both server upgrades and downgrades.

Additional information

Automatic Build Agents Update