Anthropic now ships at least three different memory models inside the Claude product family, and they don't behave the same way. Claude.ai has a chat memory feature for Pro, Max, Team, and Enterprise users that summarizes prior conversations and injects that summary into new chats. Claude Code has CLAUDE.md files plus a separate "auto memory" directory the model writes to itself, both loaded at session start. The API ships a memory_20250818 tool that hands a /memories directory to your application code so you can persist anything you want between turns. Three surfaces, three rule sets, three retention postures. I argued last week on this blog that the model isn't the variable that matters — the wrapper around it is. This is the next claim down the chain: if memory is a feature of that wrapper rather than the model, then vendor fragmentation is a memory problem you cannot solve by picking a surface. Stop trying.…