16x Prompt

16x Prompt is a Windows/macOS desktop app that sits between your codebase and the major LLMs, helping you assemble high-quality coding prompts from selected source files, task instructions, and reusable formatting rules. It tracks token counts against each model's window, applies AI-generated edits back to disk with visual diffs and automatic backups, and lets you compare outputs from GPT-4o, Claude, Gemini, DeepSeek and compatible providers side-by-side.

It's aimed at developers who don't want to live inside Cursor or Copilot but still want a disciplined way to feed multi-file context to a chat model. You bring your own API keys (or paste into the web UI), everything runs locally with no cloud storage of your code, and the free tier gives 10 prompts a day before you hit a paid license. Individual licenses activate on up to 3 devices; team licenses cover 10. There are no refunds, which is worth knowing before you buy.

Useful if your workflow is "hand-pick the right 8 files, write a careful instruction, then judge which model did it best." Less useful if you want autonomous agent loops or in-editor inline completion — 16x Prompt is deliberately a human-in-the-loop tool.