What is cairnos CLAUDE.md?

A set of project instructions for CairnOS, a local-first AI productivity desktop app. They explain its pnpm-workspace monorepo structure, where the Node engine, React and Tauri interface, SQLite database, and MCP server fit together.

Use them when working on CairnOS features, debugging its local engine or desktop interface, changing shared business logic, or following its naming and CSS conventions.

They give a coding agent the project’s architecture and conventions before it changes code. This reduces the risk of putting logic in the wrong layer or bypassing the intended data flow.

How akramlam/cairnos configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to akramlam/cairnos. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/akramlam/cairnos/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/akramlam/cairnos

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/akramlam/cairnos/claude-md/github.svg)](https://agentmods.dev/instructions/akramlam/cairnos/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/akramlam/cairnos/claude-md"><img src="https://agentmods.dev/badge/instructions/akramlam/cairnos/claude-md/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/akramlam/cairnos/claude-md"><img src="https://agentmods.dev/badge/instructions/akramlam/cairnos/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 1,804 This file is loaded in full into every session.

When invoked 1,804 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.01804	$0.01804
Opus 5.5	$0.00722	$0.00722
Sonnet 5.5	$0.00361	$0.00361
Haiku 4.5	$0.00180	$0.00180

Measured 2mo ago against content hash 272a71e22fdb, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

cairnos CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CLAUDE.md · 87 lines

How it starts

The opening of the file, as written. The whole thing — 87 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CairnOS - working notes for Claude

CairnOS is a local-first AI productivity desktop app ("Turn chaos into action."). It is a pnpm-workspace monorepo where a small Node "local engine" (Hono) owns a SQLite database and exposes a REST-ish HTTP API plus SSE. A React + Vite + Tauri desktop UI talks to that engine over HTTP, and a separate local MCP stdio server shares the same database through the shared core package. Everything runs on the user's machine - no cloud dependency.

Architecture

The local engine owns the SQLite file. A Tauri webview can't open a native SQLite file directly, so the Node engine (apps/server) holds the connection via better-sqlite3 + Drizzle. The UI reads/writes only through the engine's HTTP API.
@cairn/core is the shared brain. Services and the rule-based classifier live in core and are consumed by both the engine (HTTP handlers) and the MCP server (tool implementations) - one set of business logic, two front doors.
The UI is a thin client. The React app is mostly a TanStack Query client over the engine's API; server state lives in the engine, UI-only state lives in Zustand.
Timestamps and IDs are plain TEXT. Timestamps are ISO-8601 strings and IDs are UUID v4 strings, stored as TEXT in the DB, sent as-is over the API, and rendered as-is in the UI - zero serialization mapping anywhere.
WAL mode enables multi-process access. The engine and the MCP server are separate OS processes hitting the same cairn.db; SQLite WAL mode lets them read/write concurrently.

                  ┌──────────────┐        HTTP / SSE        ┌─────────────────┐
                  │  Desktop UI  │ ───────────────────────▶ │  Local engine   │
                  │ (TanStack Q) │   localhost:4319/api     │ (Hono, apps/    │
                  └──────────────┘                          │  server)        │
                                                            │  owns cairn.db  │
  ┌──────────────┐   @cairn/core (services + classifier)    │  better-sqlite3 │
  │  MCP server  │ ───────────────────────────────────────▶ │  + Drizzle (WAL)│
  │ (stdio, 13   │            same SQLite file               └─────────────────┘
  │  tools)      │
  └──────────────┘

Read the full file on GitHub · 87 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 87 lines · 1,804 tokens per session scan A 272a71e22fdb

Subscribe to this mod's changes

cairnos CLAUDE.md is an instructions file published in the GitHub repository akramlam/cairnos (0 stars, last pushed 4mo ago), licensed MIT. It adds 1,804 tokens to every session, about $0.0072 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

ai claude desktop local-first mcp model-context-protocol

cairnos CLAUDE.md next to 6 instructions from other repositories
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cairnos: Instructions file for Claude Code