ChatGPT maintains overwhelming market-implied odds as the #2 free app in the US App Store on September 18 due to its established position as OpenAI’s flagship large language model application, which has held top productivity rankings for years through consistent updates, broad capabilities like image generation and voice mode, and a massive installed base. Meta’s recently launched Muse personal AI agent surged to #1 this week by offering task execution such as booking reservations, filling forms, and integrating with services like email and calendars, displacing ChatGPT from the top spot just days after release. This dynamic leaves ChatGPT in a clear second-place position amid the shift toward agentic AI tools. A sudden reversal in daily download momentum or another app’s unexpected viral spike could still alter the final ranking before resolution.