Gaffer

Gaffer is a toolkit for working with KurrentDB projections.

It includes a CLI to scaffold and run projections, a VS Code extension to debug them inline, a Node.js library to drive them from your test suite, and an MCP server so AI assistants can do all of the above.

Get started

Install:

npm install -g @kurrent/gaffer

Then write your first projection.

Sections

• Getting started - install, write your first projection, debug it.
• CLI - command reference and gaffer.toml schema.
• VS Code extension - inline run/debug, state inspection, projection-API autocomplete.
• Other editors - attach Neovim, Helix, or Emacs to gaffer’s DAP server.
• Testing - drive projections from vitest, jest, or mocha with @kurrent/projections-testing.
• MCP - connect Claude Code, Cursor, Continue, Claude Desktop, or any MCP-aware AI assistant.