Compare/Overview
AI Agent Memory Tools Compared (2026): ContxOS, Claude, ChatGPT, Mem0 and Zep
A side-by-side look at how the major AI memory options store, retrieve and maintain knowledge — assistant memory, memory APIs, and project knowledge bases — with sources.
Jose R. Gonzalez, CPA · Founder of ContxOS
Updated · 3 min read
In short
AI memory now comes in three kinds. Assistant memory (Claude, ChatGPT) remembers you inside one vendor’s apps. Memory APIs (Mem0, Zep) let developers give their own apps’ users memory, and both now also offer MCP servers. Project knowledge bases (ContxOS) hold what a team and its agents have decided, learned and are in the middle of, as typed records any MCP agent can search. Pick by what you need remembered: a person, an app’s users, or a body of work.
Side by side
| Capability | ContxOS | Claude memory | ChatGPT memory | Mem0 | Zep |
|---|---|---|---|---|---|
| What it remembers | A body of work: decisions, results, plans, bugs, procedures. | You: topic entries built as you chat. | You: saved memories plus a summary from chat history. | Facts distilled from messages, scoped per user, agent or app. | Facts and entities in a temporal knowledge graph. |
| Who it’s built for | People and teams whose agents work on projects. | Claude app users. | ChatGPT users. | Developers adding memory to apps; MCP for individuals. | Developers and enterprises; MCP for teams. |
| Works across AI clients | Yes. Remote MCP server. | No. Claude chat and Cowork only. | No. ChatGPT only (Codex keeps separate local memory). | Yes. Hosted MCP server and Claude connector. | Yes. Memory MCP server (GA Aug 2026). |
| How memory is written | Deliberately, by the agent at defined moments. | Automatically during chats; editable. | Automatically; background rewrite ("Dreaming"). | Automatically extracted from messages. | Automatically extracted into the graph. |
| Replaced or outdated knowledge | Explicit supersession links; superseded, expired and conflicting results flagged in search. | Topics edited in place. | Background process revises time-sensitive memories. | Dream supersedes with pointers to the newer memory (Pro+). | Facts carry validity windows; old facts invalidated, not deleted. |
| Session handoffs | Yes, structured. | Not documented. | Not documented. | Not documented. | Not documented. |
| Reusable procedures | Workflows with tracked runs and subagent steps. | Via Skills (separate feature). | Not in memory. | Not documented. | Agent Skills (Sep 2026). |
| Free tier | Yes, one project. | Yes. | Yes. | Yes (Hobby). | Yes. |
Competitor details come from their own documentation as of September 29, 2026 (see Sources). Products change quickly; tell us if something here is out of date.
Three kinds of memory
Most confusion about "AI memory" comes from treating different products as the same. They answer different questions:
- Assistant memory answers "who is this person?" It personalizes one vendor’s chat app. Claude and ChatGPT both keep editable memories, and both now rewrite them in the background.
- Memory APIs answer "what do we know about this app’s user?" Mem0 and Zep extract facts from conversations for developers to store and retrieve, per user, at scale.
- Project knowledge bases answer "what have we decided, learned and started?" ContxOS keeps a typed record of a body of work, so any agent on the project can pick it up.
Where they converged in 2026
The field moved quickly. Memory became portable over MCP: Mem0 and Zep both run hosted MCP servers, and Mem0 is listed as an official Claude connector. Background consolidation became standard, whether it is called "Dreaming" (Anthropic, OpenAI) or "Dream" (Mem0, ContxOS). Supersession, meaning replacing a fact while keeping a pointer to what it replaced, showed up in Mem0 and Zep as well as ContxOS.
So the question is no longer whether a tool has memory. It is what shape that memory takes and what the agent can do with it.
Where ContxOS is different
ContxOS treats memory as a work record, not a fact store. A decision has a rationale, an author session, an authority level and links to what it replaced. A session ends in a handoff that another agent can resume. A procedure is a workflow with runs whose position lives outside the chat. Those are the pieces a long project needs and a personal profile does not.
Which one fits
ContxOS fits when
- Your agents work on projects that span weeks, many sessions or several people.
- You need to know which decision is current and what it replaced.
- You want repeatable procedures your agent follows the same way every time.
- You use Claude Code and want memory beyond CLAUDE.md.
Claude or ChatGPT memory fits when
- You want the assistant to remember your preferences in everyday chat, with nothing to set up.
Mem0 or Zep fits when
- You are building an app and need memory for thousands of end users through an SDK.
- You need self-hosting (Mem0 open source, Zep’s Graphiti) or enterprise controls such as BYOC.
Sources
- Claude’s memory works everywhere, and you decide what’s in it — Anthropic, August 25, 2026
- Memory FAQ — OpenAI Help Center
- ChatGPT memory: Dreaming — OpenAI, June 4, 2026
- Codex memories — OpenAI
- Mem0 MCP server — Mem0
- Dream: background memory consolidation for AI agents — Mem0, August 4, 2026
- Agent memory over MCP — Zep, August 19, 2026
- Zep changelog — Zep
Frequently asked questions
Can I use ContxOS together with Claude’s built-in memory?
Yes. They do different jobs. Claude’s memory personalizes your chats, and ContxOS holds the project record. Many people keep both on.
Which one is best for a coding agent?
For Claude Code, use CLAUDE.md for always-on rules and a project knowledge base for history, decisions and procedures. See our CLAUDE.md comparison for the detail.
Give your agent a memory that lasts
Connect ContxOS to Claude in about a minute. The free plan includes one project.
Product names belong to their owners. ContxOS is not affiliated with the companies named here.