Chapter 10ab: The Architecture Contract — What the System Is Not Allowed to Forget

Architecture is the part that survives the model

Models change. Hosts move. Connectors are replaced. A company operating system still needs a small set of decisions that remain true through those changes.

We call that set the Architecture Contract: the load-bearing decisions, invariants and re-verification commands an operator reads before touching the brain, MCP, sync, auth or agent runtime.

It is not a diagram and it is not a roadmap. It is the answer to: what would silently break the company if an agent "cleaned it up" without understanding why it exists?

The reference contract

The reference deployment currently protects these invariants:

1. One shared tool plane. Agents and human AI clients reach company systems through one authenticated MCP surface. This keeps policy, attribution and connector behavior in one place.
2. Company memory is portable. Durable memory lives in readable files with Git history. Search is an index over that memory, not the source of truth.
3. Every material write is attributable. Caller identity, tool, target, risk class, result and rollback hint enter an append-only ledger.
4. Backups and rollback are part of runtime. Frequent Git snapshots, daily encrypted backup and integrity checks are operating requirements, not disaster-recovery decoration.
5. Authentication is enforced. Every human and machine uses an identity. Anonymous access is rejected; sensitive scopes become narrower as identity improves.
6. Credentials belong to runtimes, not shared files. OAuth and refresh tokens are created independently per runtime and remain in approved secret stores.
7. Search can lag. A document may be true on disk before the index catches up. Absence from search does not prove absence from the brain.
8. Heavy artifacts live outside compute. The brain stores context, metadata and links; reusable media, PDFs, decks and delivery packs live in the company's file archive.
9. Agents do not receive the whole brain by default. Retrieval scope follows role, sensitivity and workflow need.
10. Autonomy is capability-specific. A system can be highly autonomous for one low-risk workflow and human-gated for payments, people, legal or customer-facing actions.

Contracts need executable checks

An invariant without a check becomes folklore. Each contract row should include:

invariant: "Every material write is attributable"
verify: "query the action ledger for actor, tool, target and result"
failure_state: "blocked_missing_attribution"
owner: platform
change_gate: "human approval"
rollback: "restore the last known-good service/config snapshot"

The check does not need to be sophisticated. It needs to be repeatable by someone who did not build the system.

Cloud workspaces without credential sharing

One practical consequence is a server-first workspace model. Long-running engineering and agent work happens in a dedicated cloud workspace with its own Unix identity, HOME, source control and OAuth session. Laptops and phones reconnect to that workspace; they do not copy refresh-token files between machines.

This gives the company:

• session continuity across devices;
• one auditable working tree;
• independent identity per runtime;
• fewer "works on my laptop" failures;
• clean rollback through source control;
• no need to keep a founder laptop awake for production work.

The asset boundary

Compute is not an archive. Large reusable artifacts belong in a durable company file system. The runtime may download, transform and render them, but completion means:

1. upload the final reusable artifact;
2. verify name and size, and checksum when available;
3. record the canonical link in the brain/task output;
4. remove temporary originals, extraction trees and superseded packages;
5. confirm storage headroom remains healthy.

This boundary matters because a full disk does not merely slow the system. It can stop snapshots, indexes and event writes at the same time.

Change control

Different changes deserve different gates:

Change	Minimum gate
Knowledge document	source + owner + write receipt
Canonical skill	authoring standard + separate evaluation
Agent prompt/governance	human approval + fleet propagation check
MCP/auth/runtime	backup + human approval + health smoke
Public release	anonymity + parity + link + package verification
Deletion	explicit scope + rollback + verification on every synced copy

Porting checklist

• [ ] Write ten or fewer load-bearing decisions in one canonical contract.
• [ ] Give every invariant a live verification method.
• [ ] State which changes require human approval.
• [ ] Keep search/index behavior separate from source truth.
• [ ] Create independent runtime identities; never copy OAuth state between machines.
• [ ] Version brain changes and keep an append-only action ledger.
• [ ] Put heavy reusable artifacts in the company archive, not the compute root.
• [ ] Re-read the contract before changing auth, sync, MCP or agent topology.

For Compai readers

The model is rented. The architecture contract is owned. It is the small document that stops a future model, employee or maintainer from optimizing away the exact thing that made the system dependable.