Underdog: a private AI assistant that runs entirely on the user's own device
Silicon Valley young developer Sigil Wen has launched an invite-only beta of Underdog, an AI assistant that runs fully on the user's computer. The company plans to earn a small payment fee rather than charge subscriptions or show ads.
Sigil Wen, a self-taught programmer and Thiel Fellow, opened an invite-only beta of Underdog on Monday. It is an AI assistant that keeps all data and processing on the user's own hardware. Versions are currently available for Mac and Windows computers, with Linux, iPhone and Android support promised soon.
How it works
Wen also built Husky, the software that runs the AI models. He says it is fast because it moves less data between a computer's main processor and its graphics chip. Underdog also encrypts the keys users grant for access to email and other accounts.
The assistant relies on a 27-billion-parameter reasoning model fine-tuned from Qwen3.8 27B. That is far smaller than the leading models hosted in data centers. Wen argues it compares favorably with Claude Opus 4.6 on some benchmarks, which was considered top performance six months ago, and says that is enough for everyday tasks such as shopping research or help with math homework.
Business model
The app will be free at first and never supported by ads. Because the AI runs on users' machines, the company does not pay a provider for inference. Instead, Underdog will take a tiny percentage of payments the assistant makes through Stripe's payment rails, similar to an interchange fee. Wen says this means the assistant has no incentive to mine users' data.
The startup behind Underdog, Conway Research, is backed by Andreessen Horowitz, Khosla Ventures, Hummingbird, SV Angel and the Anthology Fund, along with angel investors including Stripe co-founder Patrick Collison, Vercel founder Guillermo Rauch, Noam Brown and Deedy Das.
