This market resolves YES if Claude (by Anthropic) reaches or exceeds ChatGPT's monthly active users at any point before December 31, 2026. Resolution will be based on publicly reported figures from Anthropic and OpenAI, or credible third-party sources such as Reuters, Bloomberg, or The Verge. As of April 2026, ChatGPT has ~900M weekly active users vs Claude's ~18.9M monthly active users.