Underdog: a private AI that runs on your own Mac

Founder Sigil Wen got GPT-2 running on an Apple Watch in 2023. Underdog's backers include Andreessen Horowitz, Khosla Ventures, the Anthology fund (Anthropic and Menlo), Patrick Collison, Naval Ravikant and Guillermo Rauch.

How it works

1. 1What we measured. On a MacBook Pro (M3 Max, 48 GB) with the network blocked (underdog.ai couldn't even resolve), Underdog 27B wrote a 3-sentence email at 21.9 tokens/sec with plain MLX. The small Woof 4B ran at about 111 tokens/sec.
2. 2The Opus claim. The founder says Underdog 27B beats Claude Opus 4.6, the top model six months ago. The published comparison is the base model (Qwen 3.8 27B) on the Artificial Analysis index: 33.7 vs an estimated 31.9. Opus still leads on some benchmarks.
3. 3Husky. Underdog's own inference engine. In their tests it runs the small Woof 4B model up to 4.5x faster than Apple's MLX (range 1.3-4.5x).
4. 4Privacy. Underdog says there are no Underdog servers for personal data; context is stored on device, encrypted. Email sync and bookings still talk to your providers and websites.

Run the 27B model yourself · Apple silicon, ~16 GB

Good to know

• The Underdog app is invite-only for now.
• An independent guide by @copilot_shogo. Not affiliated with Underdog.