Installation¶

Install the package¶

macOS / LinuxWindows

Install Zwischen with pipx, which installs CLI tools in isolated environments and makes the zwischen command available on your PATH.

pipx install zwischen

If you don't have pipx yet:

macOSLinux

brew install pipx
pipx ensurepath

sudo apt install pipx   # Debian/Ubuntu
pipx ensurepath

Other distributions: see the pipx installation guide.

After installing pipx, restart your terminal before continuing.

Previously installed with pip?

If you have an existing pip install of Zwischen, remove it first to avoid shadowed executables:

pip uninstall zwischen
pipx install zwischen

pip install zwischen

If pip is not recognized:

py -m pip install zwischen

Run the setup wizard¶

zwischen install

The wizard walks you through:

API key - Enter your Zwischen API key (from zwischen.ai). The key is persisted as an OS environment variable - it is not stored in the settings file.
Model selection - Choose which AI model the reviewer should use. See supported models.
Provider API key - Enter the API key for the model's provider (OpenAI, Anthropic, Google, or DeepSeek). Stored the same way - as an OS environment variable, not in the settings file.
Claude Code wiring - The wizard installs hooks into your Claude Code settings, registers the MCP server, and installs the /z slash command skill.

When the wizard finishes, Zwischen is ready. Start (or restart) Claude Code and the reviewer will attach automatically.

Install options¶

Command	What it does
`zwischen install`	Full interactive wizard
`zwischen install --dry-run`	Preview all changes without writing anything
`zwischen install --print`	Print the hook and MCP config for manual application
`zwischen install --update`	Re-wire hooks, MCP, and skills without running the wizard (use after updating)

What gets installed¶

The installer modifies two Claude Code config locations:

~/.claude/settings.json - Adds hook entries for all eight Claude Code hook events (SessionStart, SubagentStart, SubagentStop, PreToolUse, PostToolUse, PostToolUseFailure, UserPromptSubmit, Stop) and registers the Zwischen MCP server.

~/.claude/skills/z/ - Installs the /z slash command skill that provides in-session interaction with the reviewer.

~/.zwischen/settings.yaml - Created if it doesn't exist. Stores your model selection and all reviewer configuration. API keys are not stored here - they live as OS environment variables managed by zwischen auth. You can edit this file directly at any time - settings are re-read on every session start.

No background processes

The install wizard does not start any background services. The Zwischen daemon starts automatically when you launch a Claude Code session and stops when the session ends.

Verifying the installation¶

After installing, start Claude Code. You should see a message at the beginning of your session indicating that Frank (the reviewer) has attached. You can also run:

/z session-id

If this returns a session ID, Zwischen is active. See First Session for a walkthrough.