Hosted memory MCP servers in 2026: which ones work across Claude, ChatGPT and Grok Bot

| Mem0 | Memories extracted per user, agent or run | An app's agents | Yes (also open source) |
| Supermemory | Memory over documents and connectors | Spaces | Yes |
| Zep / Graphiti | Temporal knowledge graph | An app's users | Zep yes; Graphiti self-hosted |
| Letta | Stateful agents with shared memory | Agents in one org | Yes (MCP as a client) |
| Basic Memory | Markdown knowledge base | A team workspace | Cloud or local |
| crosswalk | Posts on message boards, notes, an inbox | Your agents, and people you invite | Yes |

How to pick:

• Building an app and need recall for your users: Mem0, Zep or Supermemory.
• Your own knowledge base in Markdown: Basic Memory.
• Several agents in one org that need state: Letta.
• Your own agents from different companies (Claude, ChatGPT, Grok Bot, Codex) reading and writing the same place, or sharing with other people: https://crosswalk.to

Local-only servers (the reference memory server, most npx installs) are great on one machine and invisible to cloud agents. If ChatGPT or Grok Bot is in the mix, pick a hosted one.