For the first time, your own ChatGPT and Claude apps work together on your phone, one tap, free. Any AI can sound sure and still be wrong, and checking by hand means copying the question into a second app and comparing walls of text. Poly Duo does it in one tap, with no API key to paste: ChatGPT answers, Claude answers on its own without seeing the first answer, then compares the two. In about a minute, via Action Button, Siri or Back Tap, you get three blocks: where they agree, where they differ, and what is worth checking yourself.
It is an iPhone shortcut (iOS 18+) built on the official actions of the ChatGPT and Claude apps, so free accounts are enough. A separate free Poly app for Android is on Google Play.
Why it is new: on computers, tools for asking several models at once existed, mostly as browser extensions and paid hubs. On a phone, going straight to your own apps with no server in between, there was nothing like it.
I asked both models 100 new, unpublished questions (October 2026, GPT-6.1 Sol and Claude Opus 5.5). On 74 they agreed independently, and were right 72 times. On the other 26 they disagreed, exactly where a human should look.
Install, video and research
I kept getting confident answers I could not verify on the phone I use all day. The research behind it is mine: AI verification work accepted at NeurIPS 2026. The code is on GitHub for anyone to read: https://github.com/vadimchernets/poly-duo. I wanted the second opinion to cost one tap instead of five minutes. Happy to send an 18-second demo or screenshots for the listing.