A fresh drop landed in r/PromptEngineering yesterday, and the twist isn’t the app itself. It’s the file format underneath it. Someone shipped a full rewrite of a prompt manager for Mac, and once you see how it stores things, you’ll wonder why more tools don’t do the same.
What’s new: a Redditor known as u/CloudInsideAToaster built PromptNest, a Mac app for saving and reusing prompts. It just went through a complete overhaul, moving from an Electron shell to a native Swift build that’s about 3 MB on disk and opens instantly. For context, most Electron-based utility apps in this category ship somewhere between 80 MB and 200 MB, and they carry a full Chromium runtime along for the ride just to render a settings window. Shrinking that down to 3 MB isn’t a cosmetic win. It changes how the app behaves on a daily basis, because a tool that opens in under a second gets treated like a reflex instead of a chore.
The twist: your prompts aren’t locked inside a database or an account. Every prompt lives as a plain .prompt.md file in a real folder on your drive. That means you get grep, git diffs, and sync through iCloud or Dropbox for free, and you could delete the app tomorrow and keep every prompt you ever wrote. Think about what that actually unlocks. You can open a terminal, run a quick grep across your whole prompt library for a keyword like “SQL” or “onboarding,” and get every match in half a second, no app required. You can diff two versions of a prompt the same way you’d diff two versions of a function, watching exactly which line changed and when. And because it’s just markdown in a folder, tools you already use for something else, like Obsidian, Notion’s local sync, or a plain rsync cron job, all work on it without any extra plumbing. The creator’s reasoning is sharp: if pulling up a saved prompt takes longer than just retyping it, you’ll retype it every time, and your library quietly turns into a graveyard nobody visits. That’s the real failure mode of most prompt managers. They start as a promising archive and end as a folder you forgot existed, because the two seconds of friction to open the app and search compound into “eh, I’ll just write it from scratch again.”
The old Electron version made that problem worse, not better. It launched slowly and sat heavy in memory, which broke the app’s own two-second retrieval rule. Users reported the kind of lag where you’d hit the shortcut, wait, wonder if you fat-fingered it, and hit it again, which is exactly the behavior that kills a retrieval tool’s usefulness. Memory bloat matters here too. An app meant to be summoned dozens of times a day shouldn’t be the thing quietly eating a few hundred megabytes of RAM in the background. The native rewrite fixes exactly that, trading a general-purpose web rendering engine for code written directly against macOS, which is why the size and startup time both dropped so sharply.
How the workflow actually runs:
- 📁 Prompts save as
.prompt.mdfiles, so you own them outright - 🔤
{{variables}}mark what changes in a prompt, separating the reusable frame from the payload you swap each time - 📝 Per-prompt notes track what failed, so you’re not repeating the same dead end
- ⌨️ Global Quick Search (⌘⌥P) pulls up any prompt from inside any app
- 🔌 The whole thing runs offline, no account, no telemetry
Pro tip: if you’re already version-controlling code, treat your prompt folder the same way. Drop it in a git repo, commit after every real edit, and you get a change history for your best prompts instead of a vague memory of “it used to work better before I tweaked it.” Go one step further and write a short commit message each time, the same discipline you’d use for a code change. “tightened tone constraint” or “added few-shot example for edge case” turns your commit log into a searchable record of what actually improved a prompt, which is worth more over time than the prompt itself.
Pro tip #2: use the {{variables}} convention even if you never touch this specific app. Marking what changes forces you to name which part of the prompt is actually doing the reasoning work, and that habit alone tends to sharpen prompts you write anywhere. Try it on your next three prompts, even in a plain text file or a note app. Wrap the customer name, the product category, or the tone instruction in double curly braces, and you’ll notice how much of your “prompt” was actually static scaffolding versus the handful of variables doing the real lifting. That’s a useful diagnostic on its own, separate from whether you ever install this app.
Worth noting: this is the creator’s own app, priced at $19.99 one-time on the Mac App Store, no subscription. The older Electron version was free, and the original poster was upfront about that shift instead of burying it in a changelog nobody reads. Since your files stay as plain markdown either way, nothing locks you in if you decide to pass, which is a rare guarantee in a category full of tools that quietly assume you’ll never leave.
Head over to the original Reddit thread to see the full breakdown and weigh in on the question the creator’s still chewing on: how do you version-control a prompt library at real scale?
Built a prompt manager where your prompts are just files on disk — no database, no cloud, no account
by u/CloudInsideAToaster in PromptEngineering