What Is Claude Code? The 2026 Guide for Founders and Senior Devs

Friday, 10 p.m. You open your terminal, type claude, paste in the Linear ticket "fix the Stripe double-billing bug," and go make a coffee. When you come back, Claude has found the bug, fixed it across three files, gotten the tests passing, and opened the PR with a clear description. You approve it. This is how Claude Code, Anthropic's coding agent, works in 2026: it lives in your terminal, reads your entire codebase, writes and tests code, then opens PRs for you. Anthropic also ships it as a VS Code and JetBrains extension, a desktop app, and on the web, but its home turf is still the console you already have open. It runs on the current Claude models, including Opus 5.5 and Sonnet 5, and Anthropic includes it in the Pro plan at $17/month billed annually. Below we cover its features, release date, installation, the configuration that matters day to day, pricing plans, and how it compares with Cursor, GitHub Copilot, and Codex.

What exactly is Claude Code?

Claude Code is an agentic coding tool built by Anthropic. Agentic means two specific things. First, it makes decisions without you holding its hand. Second, it takes action: it reads files, runs shell commands, launches tests, edits code, and makes Git commits. It goes well beyond suggestions.

The official docs sum it up as "an agentic coding tool that reads your codebase, edits files, runs commands, and integrates with your development tools." Anthropic offers it across five surfaces connected to the same engine:

• the terminal, with the full CLI;
• VS Code, through an official extension that also works in Cursor;
• JetBrains IDEs (IntelliJ IDEA, PyCharm, WebStorm), through a plugin built on the CLI;
• the desktop app for macOS and Windows, in beta on Ubuntu and Debian, with a paid plan;
• the web at claude.ai/code, also available from the Claude app on iOS and Android.

Your CLAUDE.md files, settings, and MCP servers follow you from one surface to another. In Slack, mentioning @Claude on a bug report gets you back a pull request.

Claude Code release date and versions

Anthropic introduced Claude Code as a limited research preview in the Claude 3.7 Sonnet announcement, then opened it to everyone with the Claude 4 launch. Each new model generation lands in the tool from there: the Claude 5 family (Opus 5.5, Sonnet 5, Fable 5.1) took over from Sonnet 4.6 and Opus 4.7, which Anthropic keeps available as legacy models.

On the software side, the native install updates itself in the background, and claude --version shows the installed version. Homebrew offers two channels: claude-code follows the stable channel, which runs about a week behind and skips releases with major regressions, while claude-code@latest gets every release as soon as it ships. With Homebrew or WinGet, you run updates yourself (brew upgrade claude-code, winget upgrade Anthropic.ClaudeCode).

How it differs from Claude.ai (the web version)

Claude.ai is the chat in your browser. You paste code in, talk it through, and grab pieces of the answer. Everything goes through copy and paste. It's handy for brainstorming, but the context doesn't outlive the session, and the tool never touches your project.

Claude Code works the other way around. You give it a folder. It reads the file tree, understands the dependencies, and opens the files it considers relevant. It keeps your CLAUDE.md, your history, and your conventions in mind. It edits in place. It commits. It's the difference between a consultant you call on the phone and a senior dev you've hired full time.

If you want to place Claude Code within the new generation of tools where you code with AI rather than alongside it, the conceptual framework is vibe coding: you describe the intent, the agent executes.

For non-coding office tasks, like sorting files or producing a spreadsheet, Anthropic offers the same engine without a terminal in Claude Cowork.

To give it a persistent server with files, automations, and hosted services, our Zo Computer review covers that execution layer in detail.

Claude Code's everyday tasks

The most common use cases:

• Reading an unfamiliar repo and explaining its architecture in 30 seconds
• Writing missing tests for an untested module, running them, and fixing failures
• Refactoring a function across ten files in one go
• Reproducing a bug from an error message, identifying the root cause, and proposing a fix
• Creating a clean commit with a descriptive message and opening the PR
• Updating dependencies and resolving merge conflicts
• Translating a set of strings into ten languages through a CI script

You stay in your terminal and approve or reject each step.

Claude Code features

Here are the main features, each covered in detail in the section listed:

Install Claude Code and get started in 3 minutes

Installation takes about as long as a coffee. Anthropic recommends the native install, which creates a standalone binary that updates itself.

# macOS, Linux, WSL
curl -fsSL https://claude.ai/install.sh | bash

# Windows PowerShell
irm https://claude.ai/install.ps1 | iex

# Homebrew (macOS)
brew install --cask claude-code

# WinGet (Windows)
winget install Anthropic.ClaudeCode

# npm (legacy but works)
npm install -g @anthropic-ai/claude-code

On native Windows, Anthropic recommends Git for Windows so Claude has Bash available; without it, Claude Code falls back to PowerShell. On Linux, apt, dnf, and apk can also install the tool. With npm, NEVER use sudo: it creates broken permissions that take more than an hour to sort out.

First launch and authentication

cd chemin/vers/votre/projet
claude

Claude asks you to authenticate. You have three options: a Claude Pro or Max account (unified billing with claude.ai, recommended for solo devs), Claude Console via OAuth (pay-as-you-go through the API), or Bedrock / Vertex AI / Microsoft Foundry for teams working in restricted cloud environments.

A free Claude account doesn't include Claude Code. You need at least Pro.

Once it's running, type /help for the list of commands, /resume to pick up your last session, and /permissions to manage authorizations. You're ready to go.

CLAUDE.md: your project's permanent context

Installation tutorials often skip the CLAUDE.md file, even though it has a big impact on day-to-day quality.

It's a markdown file you put at the root of your project. Claude Code reads it at the start of every session. You fill it with everything you'd explain to a new dev joining the team: the stack, the conventions, the gotchas, the commands that work and the ones that break things. There's no required syntax, just plain markdown.

Minimal example for an Astro / TypeScript stack

# CLAUDE.md

## Stack
- Astro 5 + Tailwind 4 + strict TypeScript
- Content in `content/fr/blog/` (markdown with frontmatter)
- Deploy with `npm run build && npm run deploy`

## Conventions
- No `any`: use `unknown` and then narrow
- All components in `.astro` (no React unless it's already there)
- Slug = kebab-case, never accented characters

## Useful commands
- `npm run lint` before every commit
- `npm run check` for Astro TypeScript checks
- Tests with `vitest run`

## Known gotchas
- Never touch `content/_entry_example.md` (template)
- Images live on media.swanbase.co (CDN), not in the repo

Configuration levels

There are two places to put a CLAUDE.md: at the repo root (tracked in Git, shared with the team), and ~/.claude/CLAUDE.md at the user level (your personal preferences, favorite frameworks, and style, applied to all your projects).

Since 2026, the official docs add another layer: auto memory. Claude Code learns as it works, saving the build commands that succeed, the gotchas it hits, and the implicit conventions. It enriches your context on its own, between sessions. If your repo already has an AGENTS.md written for other coding agents, Claude Code reads it, either on its own or alongside CLAUDE.md.

The llms.txt format follows the same logic for AI SEO: you document the terrain so agents can find their way around. We cover it in how to use llms.txt.

Plan Mode: think before you code

Plan Mode is the feature that separates good usage from industrial accidents. You turn it on by pressing Shift+Tab twice (on Windows, sometimes Alt+M depending on the version).

The idea is simple. Claude switches to read-only. It explores your project, understands the request, and presents an implementation plan before making any change. You read the plan and correct it. Only then does it execute.

Why this matters: on a refactor touching fifty files, an agent charging ahead can neatly break your build and cost you a morning of cleanup. With Plan Mode, the agent lays out its strategy before writing the first line. If the approach is shaky, you catch it right there, before the damage.

It's also the mode to keep on for sensitive projects: production, finance, healthcare. It gives you a "look but don't touch" mode until you say "OK, go ahead."

A typical workflow: press Shift+Tab twice, explain the complex task ("add multi-tenant support to every API route"), Claude proposes a structured plan, you critique and amend it, press Shift+Tab to return to normal mode, and Claude executes the approved plan.

Sub-agents, hooks, skills, plugins: the industrialization layer

Out of the box, Claude Code is powerful. Configured, it becomes a different category of tool. The features below take you from solo use to team use.

Sub-agents: delegating to specialists

A sub-agent is a Claude Code inside Claude Code. It runs in its own context window, with its own system prompt, and has access to a subset of tools. The main agent coordinates while the sub-agent handles one specific task.

A typical use case: a code-reviewer agent that can only read and comment on code (never edit it), a test-writer that only writes tests, a migrator that only touches database migration scripts. You separate responsibilities and limit what can go wrong.

You create a sub-agent with /agents and then "Create new agent." Storage: .claude/agents/ at the project level, ~/.claude/agents/ at the user level. Format: markdown with YAML frontmatter. You version them in Git, and your teammates get them automatically.

Hooks: event-driven automation

A hook is a shell command that fires automatically at specific points in the Claude Code lifecycle. You don't ask for anything; it just runs.

The key events:

• PreToolUse: before a tool call (useful for blocking anything that touches .env or secrets/)
• PostToolUse: after one (perfect for prettier --write after every edit)
• Notification: when Claude is waiting for a response (to ping Slack or play a sound)

A concrete example: a PostToolUse hook that runs eslint --fix on every modified .ts file. You'll never ship a badly formatted PR again. Configure it with /hooks.

Skills: packaging repeatable workflows

Skills (formerly custom commands) are recipes you write once and share with the whole team: /review-pr, /deploy-staging, /migrate-db. Each one is a mini-prompt with its own tools, rules, and steps.

This is where you turn your Notion runbook.md into living automation. A new dev joins, types /onboard, and Claude sets up their environment, configures their keys, and shows them the useful commands.

Plugins: the external catalog

Plugins extend Claude Code with preconfigured skills, sub-agents, hooks, and MCP servers. You install them from a marketplace or by referencing them directly in your config.

MCP and Channels: connecting Claude to the rest of your stack

The Model Context Protocol (MCP) is an open standard for connecting AI tools to external data sources. Anthropic published it, and GitHub and OpenAI have adopted it.

An MCP server exposes tools that Claude Code can call: "read Linear ticket #234," "create a GitHub issue," "list the Slack messages that mention me." You install the MCP server, authorize it, and Claude drives the tool.

The ones that transform a team's workflow: Linear (Claude reads and updates tickets), GitHub (search across PRs, issues, and comments), Slack (reading the bug thread, posting updates), Google Drive (reading PRDs before building a feature), Notion (syncing internal docs), and your internal APIs through a fifty-line custom MCP.

Channels: Telegram, Discord, webhooks

Channels are a layer built on MCP that pushes external events into a running Claude Code session. A bug report comes in on Telegram, you forward it to your channel, and the session open on your machine picks up the context without any copy and paste. The support Discord, the founder's Telegram, the Stripe webhook for failed payments: everything converges on the dev session.

When we position Claude Code within a 2026 startup stack, we evaluate it on this integration dimension: an isolated tool looks nice, while a tool connected to your whole stack has a multiplier effect. It's the same lens we apply in our review of AI tools for startups in 2026.

Linear walkthrough: from ticket to merged PR

The typical scenario: a Linear ticket reading "The Stripe webhook stopped processing refunds after the move to API v2."

1. Fetch the ticket through MCP: /mcp linear get-issue ENG-432. Claude reads the summary, comments, and assignee, with no back and forth between Linear and the terminal.

2. Switch to Plan Mode (Shift+Tab twice). Give it the context: "Read src/webhooks/stripe.ts, identify what changed in v2, and propose a fix plan with tests." Claude spots that the v2 payload uses a new refund_reason field while the handler expects reason. It proposes adding the mapping, writing a test for both the old and new formats, and logging unknown payloads.

3. You approve. Shift+Tab to exit Plan Mode. Claude writes the code and runs the tests: two pass, covering both scenarios.

4. "Commit and open the PR." Claude writes a descriptive message, pushes, opens the PR on GitHub, and the Linear ticket automatically moves to "In Review" through MCP.

The ticket goes to review without you ever leaving the terminal. By hand, the same fix means bouncing between Linear, your IDE, GitHub, and Slack.

Claude Code vs Cursor, Copilot, Codex in 2026

The question comes up at every demo. All four tools are good, and each covers a different need.

Cursor, Copilot, and Codex pricing changes often, so check their official pages before deciding. For features specific to Claude Code (hooks, Channels, cloud routines), see the dedicated sections above.

Here's the short version.

Cursor remains the best choice if you live in your editor and want "VS Code with a copilot everywhere." If your day consists of clicking around an IDE, Cursor will suit you.

GitHub Copilot remains the standard for in-editor autocomplete, with an agent mode that builds on the GitHub ecosystem.

Codex CLI is OpenAI's terminal option, tied to the ChatGPT ecosystem.

Claude Code stands out for agentic work, multi-surface support (terminal, IDE, desktop, web, Slack, mobile), sub-agents, and Plan Mode. It fits teams that want to industrialize the way they write code.

For a detailed head-to-head covering RAM, speed, and pricing under real usage, we have a dedicated comparison: Claude Code vs Cursor.

Pricing and plans in 2026

Anthropic lists its prices in dollars. Here's where things stand as of September 26, 2026, taken from the official pricing page.

Claude subscription or Claude Console: which access to choose

There are two ways into Claude Code. A Claude subscription (Pro, Max, Team, Enterprise) covers claude.ai, the desktop app, and Claude Code on a single bill: the first time you run claude, you sign in with your Claude account.

The Claude Console is for developers who'd rather pay as they go through the API. You create a key there, set it in the ANTHROPIC_API_KEY variable or sign in with your Console account, and Anthropic bills each token at API rates. In the terminal, VS Code, and JetBrains, you can also go through Amazon Bedrock, Google Vertex AI, or Microsoft Foundry. The desktop app requires a paid subscription.

API pricing per million tokens, taken from the models documentation:

With prompt caching, a cache read costs 10% of the base input price (5% on Opus 5.5, 2.5% on Fable 5.1). The difference adds up as soon as your CLAUDE.md grows.

A good rule of thumb: Pro for 2 to 3 hours of coding a day, Max once you're coding full time, Team for a team with centralized administration, Enterprise for regulated industries, and the Console if you want to pay per token or plug Claude Code into a CI pipeline. The free plan doesn't include Claude Code, so there's no point looking for a way to enable it.

FAQ

Is Claude Code free?

No. Anthropic includes Claude Code in the Pro plan at $17 per month billed annually or $20 billed monthly, as well as in Max, Team, and Enterprise. The free Claude plan (claude.ai) doesn't include Claude Code. You can also pay as you go through the API with a Claude Console account.

Which models does Claude Code use in 2026?

Claude Code uses the current Claude family: Opus 5.5, which Anthropic recommends as the starting point and for agentic coding over long sessions, Sonnet 5 for the balance of speed and intelligence, Fable 5.1 for the most demanding reasoning, and Haiku 4.5 for fast operations. You can switch models mid-session.

When was Claude Code released?

Anthropic introduced Claude Code as a limited research preview alongside Claude 3.7 Sonnet, then opened it to everyone with the Claude 4 launch. The native install updates itself, and the claude --version command shows the installed version.

Can Claude Code modify my files without permission?

No. By default, Claude Code asks for permission before any file edit or shell command. Read-only operations go through automatically, while writes and Bash commands require approval, which you can make permanent for the session. The acceptEdits mode automatically accepts writes, and the plan mode blocks all changes until you explicitly approve.

What's the difference between Claude Code and Claude.ai (web)?

Claude.ai is the chat interface in your browser: you paste code in and have a question-and-answer conversation. Claude Code is an agent that lives in your terminal, IDE, or desktop: it reads your entire project, edits files, runs commands, and makes Git commits. Claude.ai is an occasional consultant, while Claude Code is a developer embedded in your environment.

Can you use Claude Code in VS Code?

Yes. Anthropic publishes an official extension on the VS Code Marketplace, with inline diffs, @-mentions, plan review, and conversation history right in the editor. The same extension works in Cursor. JetBrains IDEs (IntelliJ, PyCharm, WebStorm) have their own plugin on the JetBrains Marketplace.

Is Claude Code secure for proprietary code?

Pro and Max plans aren't used to train models by default. Team and Enterprise add SSO, access controls, audit logging, and advanced compliance. For regulated environments, you can route Claude Code through Amazon Bedrock, Google Vertex AI, or Microsoft Foundry. With hooks, you can also programmatically block access to sensitive files.

Does Claude Code replace a developer?

No, and the question itself is framed wrong. With Claude Code, the developer moves from executor to supervising architect. The dev defines the intent, validates the approaches, and reads the diffs. The agent handles the mechanical writing, tests, commits, and research. The effect is a multiplier.

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