Test Your Launch on a Fake Society of AI Customers: Set Up the Free MiroFish Simulator
Instead of asking one AI for one opinion, MiroFish builds a crowd of AI people with their own personalities and memories, drops your launch onto two fake social feeds and lets them argue about it. It is free and open source with 81,000 GitHub stars. How to install it by pasting one link into Claude, the plain setup, how to test a launch and the catch
Ask one AI whether your launch will work and you get one polite opinion. MiroFish gives you a whole crowd instead: simulated people who see your launch, post about it, argue with each other and change their minds, before a single real customer sees it.
How it works
- You give it material about your launch: your product page, your price, your ad, and a page on who it's for.
- It reads that and maps who and what is in it: your product, your market, the kinds of people who would buy and the ones who wouldn't.
- It turns those into AI people, each with a profile of their own (an age, a job, a personality, a backstory) and a memory that carries from one round to the next.
- It lets them loose on a Twitter-style feed and a Reddit-style feed at the same time. They post, reply, like, repost and follow, and what one says changes what the next one thinks.
- A report agent reads everything that happened and answers your question: who's in, who's out and why. Then you can chat with any single person in the simulation.
The project says it can run thousands of agents. How many you actually get depends on what you feed it: a page alone gives a small crowd, a page plus your audience, competitor reviews and a few forum threads gives a big one.
Get it
It is free and open source on GitHub. The easiest way to set it up is to send the link to Claude: open Claude Code in an empty folder and paste this:
https://github.com/666ghj/MiroFish Clone this repo, install everything it needs on my machine, create the .env file from .env.example, and tell me exactly which keys I have to paste in. Then start it and give me the address to open.
Claude checks what you already have (Node, Python, uv or Docker), installs the rest, and stops when it needs your keys. You paste those in yourself.
What you need
- Node.js 18 or newer, Python 3.11 or 3.12, and uv (a Python installer). Or just Docker, which skips all three.
- An API key for a language model. MiroFish works with any model that speaks the OpenAI format: its own example uses Alibaba's Qwen, and Claude works too through its OpenAI-compatible endpoint. This is paid per use.
- A free Zep Cloud key from app.getzep.com. That's where each AI person keeps their memory, and the free monthly quota covers simple use.
Free, for your email
Get the full setup steps + the copy-paste setup prompt
The rest of this guide (3 more sections, 7 copy-paste prompts) opens right here. The setup prompt, one paste into Claude that sets it all up, comes by email only. Use your real address.
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