azure-pipelines-agent/docs/layers.md

Architectural Layers of the Agent Code

Agent.Listener, Agent.Worker, Agent.PluginHost, and Agent.Plugins are at the top. They do not depend on each other.

Agent.Listener and Agent.Worker both depend on Microsoft.VisualStudio.Services.Agent. (This could likely be renamed Agent.Core or Agent.Common for more clarity.)

All of the assemblies mentioned so far depend on Agent.Sdk, and many of them depend on the various Microsoft.VisualStudio.Services.* web APIs. Additionally, Agent.SDK depends on some Microsoft.TeamFoundation.* assemblies.

Diagram

In rough terms, dependencies look like this:

graph TB
  subgraph App
  Agent.Listener
  Agent.Worker
  Agent.PluginHost
  Agent.Plugins
  end
  subgraph Platform
  agentcore[MS.VS.Services.Agent]
  agentsdk[Agent.SDK]
  end
  subgraph Infrastructure
  webapi[MS.VS.Services.*.WebAPI]
  tf[Microsoft.TeamFoundation.*]
  end
  Agent.Listener --> agentcore
  Agent.Worker --> agentcore
  Agent.PluginHost --> agentsdk
  Agent.Plugins --> agentsdk
  agentcore --> agentsdk
  agentcore --> webapi
  agentsdk --> tf