A desktop overlay that sees your screen, answers questions about it, and points at the control you need. Ask a question; Handrail sends your screenshot and question to your chosen vision model, then draws arrows at real controls. It watches multi-step checklists as you work. Electron, Apache-2.0; local threads, OS-keychain API key, no account/telemetry; web search off by default. BYO OpenRouter/OpenAI/Anthropic key. Working daily by maker; author-only so far.
Built because software help usually assumes you already know what things are called. It looks at your screen, answers about that screen, and points at the control it means.