Poly Duo is a free, open-source tool that makes two AI assistants check each other. It was created by Ukrainian independent AI researcher Vadym Chernets. On an iPhone it uses the Shortcuts app and the official Ask ChatGPT and Ask Claude actions: one assistant writes an answer, the other reviews it for mistakes, and you receive a short summary of points of agreement, disagreements and questions to verify yourself.

It automates the common habit of asking one assistant, pasting the answer into another and asking whether it is right. The author says it offers 12 modes, including finding a compromise between the answers, a map of discrepancies, a synthesis and a side-by-side view. A directory says it runs through on-device Shortcuts and official apps rather than an outside server. Android support is described through a free app called Poly A1, and a variant called Poly Trio adds a third model.

The source is released under the Apache-2.0 licence, according to AlternativeTo, which also shows a small GitHub repository with few stars. The tool is free, but you need access to the assistants it connects to, and any subscriptions to those are your own cost. Agreement between two models does not prove an answer is correct, so verify important facts yourself. This page is a summary based on public listings and the vendor’s own description, dated 2026-11-13. It was not tested hands-on, and details may have changed.