Claude Architect · Lesson

What Is Claude Code

An agentic coding tool that lives in your terminal and IDE.

Claude Code in One Sentence

Claude Code is an agentic coding tool that lives in your terminal and IDE. Instead of copy-pasting snippets into a chat window, you let Claude read your real files, run commands, and edit code directly in your project.

It is not just an autocomplete. It runs an agentic loop: it inspects the task, calls tools, reads the results, and keeps going until the work is genuinely done.

On the Claude Certified Architect exam, this lives in Domain 3 (Claude Code Config & Workflows, 20% of the exam). Understanding what Claude Code is — and how it differs from a plain chatbot — is the foundation for everything else in this track.

Why "Agentic" Matters

A plain LLM chat call is one round trip: you send a message, you get text back. Claude Code is different — it is built on the agentic loop:

Send a request to the model.
Inspect the stop_reason on the response.
If it is tool_use, run the requested tool and append the result to the conversation history.
Repeat until the model returns end_turn.

The critical rule: you terminate on the stop reason, never by scanning the model's text for words like "done" or "finished". Parsing text for completion signals is a classic anti-pattern the exam loves to test.

stop_reason = response.stop_reason
if stop_reason == "tool_use":
    # run the tool, append its result, loop again
    pass
elif stop_reason == "end_turn":
    # the model is genuinely finished
    pass

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