Who Owns the Loop
Manual loop vs the SDK Tool Runner vs Managed Agents vs the Claude Agent SDK — separated by who supplies the agent harness and who supplies the deployment.
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After this section you can
- Place the manual loop, Tool Runner, Claude Agent SDK and Managed Agents on the harness and deployment axes
- Tell the Tool Runner apart from the Claude Agent SDK and pick the right one for a task
- Choose an option from a scenario, and explain why approval gates do not require a hand-written loop
Who Owns the Loop: Harness vs Deployment
There are four ways to build an agent on Claude. Two questions tell them apart, and the word “SDK” hides both of them.
Ask two things: who runs the loop (the harness), and whose machine it runs on (the deployment). The Tool Runner and the Claude Agent SDK both give you a harness and leave hosting to you. Only Managed Agents takes both.