PSA for anyone using Claude projects to compartmentalize their work: check your project settings right now.

Anthropic has quietly introduced a "Use account memory" toggle within Claude projects, which was found enabled by default on existing projects. This feature links project-specific memory with account-level memory, impacting all regular conversations. The change, seemingly part of the September 16-17 platform unification when Cowork merged into Chat and Projects were redesigned, occurred without any official announcement, migration notice, or documentation update. Users are advised to check their project settings immediately.

This report is the first to detail Anthropic's unannounced "Use account memory" toggle, which silently bridges project-specific memory with account-level memory, unlike previous compartmentalized project settings.