TWITTER_POST

Simile is presented as a startup building LLM-based population simulators rather…

2026-02-12 · 19:00 UTC ·karpathy ·1 min read

Brief

Simile is presented as a startup building LLM-based population simulators rather than single-character chatbots. Karpathy calls that direction promising and under-explored, emphasizing technical challenges around controlling diversity, measuring faithfulness, and understanding emergent dynamics. The launch post adds that the company has already raised $100 million from major firms and prominent AI and tech angels.

Source evidence

title: @karpathy: Congrats on the launch @simile_ai ! (and I am e...
author: karpathy
contenttype: twitterpost
published: 2026-02-12T19:00:48+00:00
source_url: https://x.com/karpathy/status/2022041235188580788

word_count: 174

Tweet by @karpathy

Congrats on the launch @simile_ai ! (and I am excited to be involved as a small angel.) Simile is working on a really interesting, imo under-explored dimension of LLMs. Usually, the LLMs you talk to have a single, specific, crafted personality. But in principle, the native, primordial form of a pretrained LLM is that it is a simulation engine trained over the text of a highly diverse population of people on the internet. Why not lean into that statistical power: Why simulate one "person" when you could try to simulate a population? How do you build such a simulator? How do you manage its entropy? How faithful is it? How can it be useful? What emergent properties might arise of similes in loops? Imo these are very interesting, promising and under-explored topics and the team here is great. All the best!

Posted: 2026-02-12T19:00:48.000Z
Engagement: 8259 likes, 637 retweets, 389 replies

Quoting @joonspk

Introducing Simile.

Simulating human behavior is one of the most consequential and technically difficult problems of our time.

We raised $100M from Index, Hanabi, A* BCV, @karpathy @drfeifei @adamdangelo @rauchg @scottbelsky among others.