Xerum

Same-origin bought us a lot, and charged us one path space

Mon, 31 Aug 2026 14:00:00 +0000

The web app is split by plane: account pages served by the control plane on its own origin, your instance’s pages served by your instance on its. Each app is same-origin with the data it reads.

That buys a lot. No CORS on any data call. The browser is an ordinary OAuth client rather than a privileged one — it ends up holding exactly what an agent holds, which means we did not invent a second auth mechanism for the UI. And opening the app does not wake a sleeping container, because the shell is served from the edge.

The deploy artefact that had never once built

Mon, 31 Aug 2026 09:00:00 +0000

task backend:build:linux had never worked. Not once, since the day it was written.

Nothing noticed, because nobody had run it. Every developer build is a darwin build, and a darwin build takes a different path that succeeds. The task that produces the thing we would actually deploy had been quietly broken for as long as it had existed.

The failure

Building the tenant with GOOS=linux CGO_ENABLED=0 failed on undefined symbols.

We reversed our biggest design decision, and it cost almost nothing

Thu, 27 Aug 2026 10:00:00 +0000

The design said git was the system of record. A change was a commit, a revision a commit id, a proposal a ref kept alive. It was written down, argued for, and — for a while — right.

We reversed it. Sqlite is the system of record now: an append-only changes log plus a content-addressed blobs table, with everything else a derived index. This is the note about why, and about the thing that made the reversal affordable.

About Xerum

Mon, 01 Jan 0001 00:00:00 +0000

Every team now runs AI agents, and every one of them is an amnesiac.

The knowledge that makes a team a team — why decisions were made, what broke last quarter, what got agreed in a review thread nobody will ever open again — is scattered across GitHub, Jira and Slack, and none of it reaches the model. So agents guess. And when agents guess, people stop trusting them, which is a worse outcome than not having them.

How it is built

Mon, 01 Jan 0001 00:00:00 +0000

This page is for the person who will be asked whether this is sound. It says what the system is, and — where a decision was close — what the alternative was and why it lost.

One instance per team

Every customer runs their own container. Its own database file, its own index directory, replicated to its own storage prefix.

There is no shared index with a customer column in it, and the API has no customer id parameter to pass. A request reaches one instance because of the hostname it arrived on and the token it carried, and that instance has only ever held one team’s data. This is what “isolation is architecture, not a WHERE clause” means concretely: there is no filter to get wrong, because there is nothing to filter.

Shared context for customer support organisations

Mon, 01 Jan 0001 00:00:00 +0000

Shared context for financial services and investment teams

Mon, 01 Jan 0001 00:00:00 +0000

Get an instance

Mon, 01 Jan 0001 00:00:00 +0000

There is no self-serve sign-up button yet, and this page exists to say that plainly rather than to send you to one that does not work.

Where we are

Xerum is provisioning instances for design partners — teams who will use this daily, on real work, and tell us where it is wrong. Each one gets their own container, database and storage prefix, the same as every customer will.

What runs today: the versioned store, full history and time travel, the GitHub connector, hybrid search with provenance, the proposal loop, MCP and REST doors, and the web app for browsing, comparing, searching and reviewing proposals.

The eight words

Mon, 01 Jan 0001 00:00:00 +0000

Most products have three vocabularies: one in the code, one in the product spec, and one in the marketing. Ours has one. The words below are the type names in the domain package, the nouns in the API contract, and the nouns on this website — and where a page here says “resource” it is because the code says Resource, not because a writer liked the sound of it.

That is not tidiness for its own sake. It means an engineer, a support lead and somebody in a sales call can describe the same behaviour without anybody translating, and it means a question like “what happens when a Jira ticket already in our context gets edited?” has one answer rather than three.

Shared context for government and defence suppliers

Mon, 01 Jan 0001 00:00:00 +0000

Shared context for legal teams

Mon, 01 Jan 0001 00:00:00 +0000

Connect your agent

Mon, 01 Jan 0001 00:00:00 +0000

MCP is the reason a context layer is buildable at all this year. Before it, serving context to agents meant an integration per agent; now it is one server that every serious client already knows how to talk to.

Your instance is one of those servers.

What connecting gives an agent

Search the shared context, permission-filtered before ranking, with hybrid full-text and vector retrieval behind it.
Read any resource, at head or at an older revision.
Compare two revisions to see what changed between them.
Follow what has changed since it last looked, through a subscription.
Propose a change — which an owner then approves or rejects. An agent never writes to the record directly.

Every result carries its provenance: the revision it was read at, the resource it came from, and the origin URL at the source.

Shared context for media and research organisations

Mon, 01 Jan 0001 00:00:00 +0000

Shared context for pharma and regulated R&D

Mon, 01 Jan 0001 00:00:00 +0000

Privacy

Mon, 01 Jan 0001 00:00:00 +0000

Last updated: 31 August 2026.

This page describes what Xerum holds, where it holds it, and what we do and do not do with it. It is written plainly on purpose.

Shared context for professional services and consulting

Mon, 01 Jan 0001 00:00:00 +0000

Security and isolation

Mon, 01 Jan 0001 00:00:00 +0000

Two questions decide whether a context layer can be bought: can it leak between customers, and can it show somebody something they should not see. This page answers both, and then says what is not yet done — because a security page that only lists strengths is not one.

Isolation between customers is physical

Every customer runs their own container, with its own database file, its own index directory and its own storage prefix.

Shared context for software teams

Mon, 01 Jan 0001 00:00:00 +0000

Terms

Mon, 01 Jan 0001 00:00:00 +0000

Last updated: 31 August 2026.

Xerum is currently provided to design partners under an individually agreed arrangement. This page sets out the terms that apply generally; where your agreement says something different, your agreement wins.

The service

Xerum provides a hosted, per-customer instance that records resources from sources you connect, keeps a versioned history of them, and serves them to agents and applications you authorise over MCP and REST.

You get your own container, database and storage prefix. We operate it; you decide what goes into it.

Xerum compared with an agent memory layer

Mon, 01 Jan 0001 00:00:00 +0000

Xerum compared with building RAG yourself

Mon, 01 Jan 0001 00:00:00 +0000

Xerum compared with enterprise search

Mon, 01 Jan 0001 00:00:00 +0000

Xerum compared with platform-native memory

Mon, 01 Jan 0001 00:00:00 +0000