Poly Duo
Have Claude check ChatGPT's answer on your phone and see where the two disagree
Forpeople who act on chatbot answers and want a cross-check iPhone, Android
Wrong birth years come out of a chatbot as calmly as right ones, while nothing on the screen says which answer needs a double-check. For a second opinion, Poly Duo asks an AI from another company. On an iPhone, ChatGPT goes first, and Claude then answers the same question without seeing that reply and compares the two.
The result comes back in three short blocks, and the middle one lists every point where the answers part ways. Behind it is a Shortcut that drives the ChatGPT and Claude apps on your own accounts, through their Shortcuts actions. It needs iOS 18 or later with both apps signed in. After about five permission prompts on the first run, the Action Button or "Hey Siri, Duo" starts a round, which takes about a minute.
On Android, Duo comes inside the Poly A1 app from Google Play and runs on API keys, the personal access codes AI companies hand out to developers. One model writes the answer, and a model from another company checks it. In the maker's own test on 100 unpublished questions, GPT-6.1 Sol and Claude Opus 5.5 agreed on 74 answers, and the site reports 72 of those as right.
Good fit if you…
- want a second opinion on a contract clause, a money question or code before acting on it
- already use the ChatGPT and Claude apps and want them to check each other
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