CAIRN — the walk protocol

A cairn is a stack of stones piled by walkers along a path. Each pilgrim adds one. The pile guides the next walker. The substrate's CAIRN protocol elevates each step you walk into a stone — and your walk into a growing cairn.

CAIRN — Chain-Attested Iterative Replayable Navigation.

Each word is load-bearing. Chain-Attested: every stone in the cairn lives in the substrate's BitNet chain; provenance proves each step. Iterative: built one step at a time, in walking order, never out of sequence. Replayable: any cairn can be re-walked by another node; the substrate verifies each stone. Navigation: a way of moving through the substrate, not a static record.

Walk a cairn. Build one. Share it. Merge two.

What you do when you walk MerkleTrust

Every sim on this site is a walk through a substrate-attested workflow. As you move from step to step, you can press + .md on any step you find load-bearing — a clinic owner's audit packet, an attorney's evidence motion, a clerk's pre-acceptance flag. Each press attests that step into your cairn. The button records a BitNet ternary state change:

ATTESTED — you attested this step into your cairn. The button shows ✓ in journey persistently for that step. The bundle counter in the page footer ticks up by one. The substrate remembers.

NOT_YET — you've walked the step but haven't pressed + .md on it. The button shows + .md awaiting your decision. No state change recorded yet.

−1

REJECTED — defensive state. The substrate refused to add the step (bundle full, malformed input, validation failed). The button shows the rejection reason briefly.

Your cairn lives in your browser's local storage as you walk. At the close-step of any sim, the Walk outbox lets you download your cairn as merkletrust_journey.md — a per-step attested record of everywhere you walked and what you marked load-bearing.

The four things cairns enable

The CAIRN protocol is more than a per-visitor bookmark. It opens a programmable walk language — the substrate's parallel to what GitHub did for code. Walks become diff-able, mergeable, branched, replayable.

1. GitHub-for-walks

Push your cairn to a registry. Others clone it, follow the path, verify each stone composes against the substrate's live sidecars. Here's the path I walked to defend an audit. Walk it yourself; verify the chain holds.

2. Trained on attestations

Aggregate cairns become a corpus. Each step has a per-corpus attestation rate. A model trained on this teaches the substrate what new visitors should walk based on what already-attested visitors did. The signal is the attestation, not the click — cryptographic commitment beats noise.

3. Sim replay

Given a cairn, the runtime replays it: step through the attestation order, fire the chain operations declared in each step's sidecar, verify the close-step cert composes. Every captured cairn becomes a regression-test fixture for substrate logic.

4. Substrate-attested experiments

Two cairns = an A/B test. Recruit operators to walk treatment or control; compare downstream outcomes. The experiment itself leaves a cairn — the experimental design is auditable substrate-content. Research with chain-of-custody.

Vocabulary

a cairn	one walker's attested walk through the substrate — the sequence of stones piled in walking order
build a cairn	walk the substrate and attest your steps; each `+ .md` press places a stone
share a cairn	publish your cairn for others to clone or replay
clone a cairn	pull someone else's walk into your substrate to follow it
walk a cairn	replay an existing cairn — step through its stones in order
merge cairns	compose two walks (treatment + control, or two operators' learning) into a combined cairn
a cairnfield	a registry of cairns — the substrate's GitHub for walks
stones	individual BitNet attestation entries within a cairn

Why this name

The metaphor maps almost completely to the data model. A cairn is built one stone at a time, visible to the next walker, durable across seasons. Mountain passes were navigated this way for centuries before maps. The substrate's design philosophy — attesting state changes, one step at a time, sovereign-paced, clone-portable — is exactly what cairns have always done.

The naming also fits the substrate's vocabulary. Pale March, Hazel Dell, Garrison Node, the council, the silos, the sovereign — these are old-world words doing modern work. CAIRN sits with them naturally. It does not advertise.

What's already operating

As of S152 (the launch sprint), the per-step BitNet attestation lives in walkthrough_v3.js. Your bundle counter in the page footer reflects how many stones you've placed. Your merkletrust_journey.md downloads with per-step entries grouped by card. The defensive layer — shape validation, bundle-size cap, prose sanitization — protects the cairn from local manipulation.

The remaining capabilities sketched above (push/pull cairns, ML training, sim replay, experiments) are the protocol's near future. They compose with the substrate already running. The first cairn ever built on this substrate is being built right now, by someone walking 40a or 40e or 40v on this very deploy. Each of their + .md presses is a stone in the substrate's first cairnfield.

Status: CAIRN sketch filed S152 launch night, 2026-04-29. Provisional ADR-044 forthcoming. The protocol's name and metaphor are stable; the registry, signing format, and push/pull semantics are open for development.