Epicenter is an ecosystem of open-source, local-first applications built on a shared memory layer, described as ChatGPT's memory feature in an open, portable format. It stores notes, transcripts, and chat histories in plain text and SQLite files that users own and control. The tools are accessible via text editors, Obsidian, or self-hosted instances. Epicenter was part of Y Combinator's Summer 2025 batch and is based in San Francisco.