by Substrate Systems
An epistemic knowledge base, built around youAn epistemic knowledge base

Grows with you.
Stays true.

Exomem is the knowledge base all your assistants share. Claude, ChatGPT, Claude Code, Codex and every session you connect read from it and add to it. When something changes, it keeps what was true, why it changed and what replaced it, as plain Markdown you own.The knowledge base all your assistants share, in every session. When something changes, Exomem keeps what was true, why it changed and what replaced it, as plain Markdown you own.

Open Exomem →Run it yourself, free →
ClaudeChatGPTClaude CodeCodex+ any MCP app
Claude › where are we staying in Reykjavík?130 ms
→ trip/hotel-borg.mdhotel-borg.mdbooked 2 May · current
→ trip/airbnb-laugavegur.mdairbnb-laugavegur.mdsuperseded · kept for historysuperseded, kept
supportsrefinescontradictssupersedes
≈ 0.1 sto recall from a real vault
50,000notes, still under a second
1knowledge base for every assistant and session you connectknowledge base for every assistant and session
.mdplain Markdown you own
01 · How it stays true

Built to change without forgetting.

01

Remember

Every assistant you connect reads from it and adds to it. Ask in your own words; decisions, sources and what you learned are kept, not lost when the chat ends.Every assistant you connect reads from it and adds to it. What you decided and learned is kept, not lost when the chat ends.

02

Connect

Notes link by what they mean: this supports that, this contradicts that. Contradictions come up for review instead of one answer quietly winning.Notes link by what they mean: this supports that, this contradicts that. Contradictions come up for review.

03

Evolve

Nothing is thrown away. When you change your mind, the old note is superseded and kept, so you can still ask what you knew in March, and why.Nothing is thrown away. The old note is superseded and kept, so you can still ask what you knew in March, and why.

02 · See it

Your knowledge, as a living map.

In your Exomem account: click any note to see what supports it, what it replaced and where it came from. Scrub back in time. Watch your assistants recall, live.Click any note to see what supports it and what it replaced. Scrub back in time. Watch your assistants recall, live.

03 · Two ways in

Use it in your assistant, or run it yourself.

In your assistant

hostedCloud
  1. 1Start with your email; no passwordStart with your email
  2. 2Subscribe; your vault is ready in a minuteSubscribe; ready in a minute
  3. 3Add Exomem in Claude’s connectors or ChatGPT’s pluginsAdd it to Claude or ChatGPT
ClaudeChatGPTClaude CodeCodex+ any MCP app
Open Exomem →
Monthly · cancel any time · export whenever you likeMonthly · cancel any time · export any time

Run it yourself

open source
Agents get memory. You keep the files.Agents get memory.
You keep the files.
Open source. Runs on your machine with any MCP client, Cursor included.
GitHub · PyPI · README
04 · Yours to keep

We run it. You own it.

The same open-source engine, hosted for you. Your vault is plain Markdown, and you can export it any time, even after you stop paying.

Open Exomem →
  1. 01Storage and transport encrypted; each account’s vault runs in its own cellEncrypted, in its own cell
  2. 02If a payment fails, memory turns read-only while Paddle retries. Nothing is lost.Payment fails? Read-only while Paddle retries. Nothing lost.
  3. 03If you cancel, we keep everything for 30 days, read-only, then delete it.Cancel, and we keep it 30 days, read-only.
  4. 04Export a verified copy of your vault any time, in any state.Export a verified copy any time.
For developersHow it works inside, the full benchmarks and methodology, and how it compares.Internals, benchmarks, comparisonRead the details →→