Claude Code is Anthropic’s terminal-based coding agent, and it’s the tool that convinced a lot of skeptics that “agentic coding” is real. Instead of completing lines or answering questions, it takes goals: “migrate this package from Jest to Vitest,” then explores, edits, runs, and iterates until done.
How It Works
Claude Code runs in your terminal with access to a set of tools - file reading and editing, bash execution, search, web fetch, and MCP servers you configure. Given a task, it forms a plan, gathers context by reading your repo, and works through the plan, checking its own work by running your tests and linters.
npm install -g @anthropic-ai/claude-code
claudeThe loop matters more than any single feature: edit → run → observe → fix, repeated autonomously, is what separates an agent from a chatbot.
Getting Good Results
The difference between a magical session and a frustrating one is mostly setup:
Write a CLAUDE.md
A CLAUDE.md file at your repo root is Claude Code’s memory. Put in it:
- Build, test, and lint commands
- Code style rules the project actually follows
- Architectural boundaries (“never edit files in
generated/”) - Anything a new hire would need on day one
Projects with a thoughtful CLAUDE.md get dramatically better output.
Scope tasks tightly
“Add rate limiting to the /api/search endpoint using the existing Redis client” works. “Make the API better” doesn’t. Claude Code is at its best on tasks with a verifiable done-state.
Use plan mode for big work
Shift+Tab into plan mode and Claude Code will research and propose a plan before touching code. For refactors, this review step catches wrong assumptions cheaply.
Advanced Features Worth Knowing
- Subagents: specialized agents (e.g., a code reviewer, a test writer) with their own context windows, defined in
.claude/agents/. - Hooks: shell commands triggered on lifecycle events - format on save, run tests after edits, block writes to protected paths.
- Headless mode:
claude -p "..."runs non-interactively, which makes it scriptable in CI - e.g., auto-fix lint failures on PRs. - MCP servers: connect databases, issue trackers, docs, or internal tools so the agent can pull real context.
Where It Shines
- Multi-file refactors with tests to verify against
- Migrations (framework upgrades, dependency swaps)
- Exploring unfamiliar codebases - “how does billing work in this repo?” returns a traced answer with file references
- Grunt work with clear acceptance criteria - writing tests for an untested module, fixing a batch of type errors
Where It Struggles
- Ambiguous product decisions. It will happily build the wrong thing confidently.
- Cost on big sessions. Long autonomous runs consume real tokens; keep an eye on usage.
- Very long horizons. For tasks spanning hours, it can lose the thread - break work into stages.
Verdict
Claude Code is the strongest terminal agent available right now and the one to beat. It rewards teams that invest in setup - a good CLAUDE.md, scoped tasks, hooks - and it’s a genuine force multiplier for senior developers who know what “done” looks like. Compare it with the other options in our AI coding CLIs roundup, or find alternatives on its tool page.