Installing Claude Code
Claude Code is an agentic coding tool that runs in your terminal and integrates with your IDE. It reads your entire codebase, plans changes across multiple files, edits code, runs shell commands, executes tests, and iterates on failures — all with your approval at each step. Unlike a simple autocomplete tool, it operates at the project level, understanding context across files and directories before making any changes.
By default, Claude Code operates cautiously: it asks before modifying files or running commands, shows you a diff of proposed changes, and waits for your confirmation. This makes it practical for both exploratory work (understanding an unfamiliar codebase) and large-scale autonomous tasks (multi-file refactoring, feature development, CI pipeline integration).
Claude Code requires an active paid Claude subscription (Pro, Max, Team, or Enterprise) or an Anthropic Console account with API credits. It also supports third-party cloud providers including Amazon Bedrock, Google Vertex AI, and Microsoft Foundry. The free Claude.ai plan does not include access.
When you’d use it
- ◆Codebase Exploration for New Team Members — A developer joins a project with hundreds of files and no documentation. They ask Claude Code to summarize the codebase structure, identify the entry point, and explain where authentication is handled — without having to manually grep through directories.
- ◆Automated Bug Fixing and Test Repair — A CI run returns a failing test. The developer pastes the error message into Claude Code and asks it to trace the root cause, fix the code, and re-run the suite until everything passes — Claude Code handles the read-fix-run-retry loop autonomously.
- ◆Large-Scale Multi-File Refactoring — A team needs to migrate a 20,000-line codebase from synchronous to async/await patterns. Claude Code identifies all blocking I/O calls across dozens of files, plans the migration, applies changes incrementally with user approval, updates tests, and opens a pull request with a summary.
- ◆Writing Tests for Untested Code — An existing module has no test coverage before a production release. Claude Code reads the module, infers expected behavior, writes comprehensive unit tests covering edge cases, runs them, and fixes any failures it introduced.
- ◆CI/CD Pipeline Integration for Code Review — A DevOps team configures Claude Code in a headless CI environment. It monitors pull requests, runs automated code review checks, flags issues, and can commit fixes directly when failing CI telemetry matches known patterns — without human intervention.
What changed recently
- ◆2026-05 — NPM global installation method (npm install -g @anthropic-ai/claude-code) officially deprecated. Claude Code migrated to natively compiled binaries delivered via curl/PowerShell install scripts. The native binaries auto-update in the background, eliminate Node.js runtime dependencies, and improve security sandboxing. Existing npm installs receive a one-time terminal warning directing users to /doctor for migration.
- ◆2026-05 — Five-hour rate limits for Claude Code doubled across Pro, Max, Team, and seat-based Enterprise plans. The peak-hours usage reduction previously applied to Pro and Max accounts was removed entirely.
- ◆2026-01 — Native VS Code extension released in beta, bringing Claude Code directly into the IDE with a dedicated sidebar panel and inline diffs. Terminal 2.0 interface released alongside it.
- ◆2026-01 — Checkpoint system introduced: Claude Code automatically saves code state before each change. Users can revert to any prior state using Esc+Esc or the /rewind command, enabling safer delegation of large autonomous tasks.
This is the short version
The full chapter has three worked examples, the common pitfalls, and the workflow that makes it pay — plus the other 84 features, kept current.
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