In about ten minutes, AI stops being a tab you paste into and becomes a helper on your own laptop that can read a folder you choose.

Mac: press Cmd + Space, type Terminal, press Enter. A window with a blinking cursor appears. You type commands here and press Enter; you cannot click on things.

Windows: hold the Windows key and press X, then choose Windows PowerShell (or Terminal). The line must start with PS. If there is no PS, you opened Command Prompt; close it and try again.

Copy one line, paste it into the window, press Enter, and wait for "Claude Code successfully installed!"

Mac:

curl -fsSL https://claude.ai/install.sh | bash

Windows (PowerShell):

irm https://claude.ai/install.ps1 | iex

Then check it and sign in. Type claude --version and press Enter; you should see a version number and "(Claude Code)". Then type claude and press Enter. A browser window opens; sign in with the account you use for Claude, then come back to the window. If it asks whether you trust this folder, say yes. Type exit to leave.

Same shape, one line, then sign in with ChatGPT.

Mac:

curl -fsSL https://chatgpt.com/codex/install.sh | sh

Windows (PowerShell):

powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"

Type codex --version to check, then codex, choose Sign in with ChatGPT, and finish in the browser. Type exit to leave. To update Codex later, run the same install line again.

Make a folder on your Desktop called Staging Business and put your business-context file in it. In the window, type cd (with a space after it), drag the folder from Finder or File Explorer into the window, and press Enter. Now type claude, press Enter, and give it this. Replace the bracketed parts with your own situation and leave out anything private.

Read business-context.txt and draft a follow-up email to [FIRST NAME], the [listing agent / homeowner] from [WHEN]'s [PROPERTY DESCRIPTION] consult. [WHAT THEY ASKED FOR] by [DAY], under 120 words. Don't invent details; if you need something, ask.

You did not paste the file. It is in the folder, so Claude reads it. Look for your own sign-off and your package name in the draft. Claude drafts; you send.

Verified against the official Claude Code troubleshooting page on 2026-09-17.

• "command not found: claude" or "'claude' is not recognized" — close the window, open a new one, try again. If it still fails on Mac, paste echo 'export PATH="$HOME/.local/bin:$PATH"' >> ~/.zshrc && source ~/.zshrc then open a new window. On Windows, paste these two lines, then open a new window: $currentPath = [Environment]::GetEnvironmentVariable('PATH', 'User') and [Environment]::SetEnvironmentVariable('PATH', "$currentPath;$env:USERPROFILE\.local\bin", 'User').
• The install line prints an error like "syntax error near unexpected token '<'", a 403, or a page of code — the download handed back a web page. Wait a few minutes and run the same line again. Mac backup route, only if you already have Homebrew: brew update then brew install --cask claude-code. Windows backup route: winget install Anthropic.ClaudeCode.
• Mac: "dyld" error or "built for Mac OS X 13.0" — your macOS is too old. Apple menu, About This Mac, then Software Update.
• Windows: "irm is not recognized" — you are in Command Prompt. Open Windows PowerShell instead. "The token '&&' is not a valid statement separator" — you are in PowerShell but pasted a Command Prompt line; use the PowerShell line above.
• Windows: "Claude Code does not support 32-bit Windows" — you opened Windows PowerShell (x86). Open the one without x86 in the name.
• Windows: SSL or TLS error on older Windows 10 — paste [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12 first, then run the install line again.
• Windows: typing claude opens the Claude Desktop app — update Claude Desktop, then try again.
• The browser did not open at sign-in — press c to copy the link and paste it into your browser. "403 Forbidden" after signing in — your plan does not include Claude Code; check your subscription at claude.ai settings.
• Someone told you to install Node, npm, or Homebrew first — not needed. The one-line installers above need none of them. Git for Windows is also optional.