What is branchnew?

This is a small command-line tool for Mac users who work with Claude Code, the AI coding assistant. Its single job is to split your terminal window to the right and start a forked copy of your current Claude Code session in that new pane. The new copy picks up the same conversation context, then the two run independently from that point forward. Your original session is not affected in any way. The tool is called with one word: typing branchnew in the terminal does the split and the fork automatically. If you want to give the new session a name, you pass the name after the command, such as branchnew login-fix. Without a name, it auto-assigns names like newBranch1, newBranch2, and so on using a counter that keeps incrementing across all your sessions. You can also type /branchnew directly inside a Claude Code chat window to trigger the same behavior as a slash command. The tool detects what kind of terminal you are using and adjusts its approach. Inside tmux it creates a real split pane to the right. In iTerm2 it uses the native split. In Apple Terminal, which does not support split panes, it opens a new window instead. Terminals it cannot control fall back to opening a new Apple Terminal window. For iTerm2 users there is an optional hotkey mode. After a one-time setup, pressing a keyboard shortcut forks the exact Claude session running in the current pane, even if that session is itself already a fork. This uses an iTerm2 background process combined with Claude hooks that track which terminal pane corresponds to which session. Installation is a single curl command that downloads and sets up the tool without requiring you to clone the repository. The project is licensed under MIT, meaning free use with attribution.