Borrowing it
Nothing to install: this file belongs to isaacriehm/cairn. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/isaacriehm/cairn/main/AGENTS.mdgit clone --depth 1 https://github.com/isaacriehm/cairnWrote 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.
[](https://agentmods.dev/instructions/isaacriehm/cairn/agents-md)<a href="https://agentmods.dev/instructions/isaacriehm/cairn/agents-md"><img src="https://agentmods.dev/badge/instructions/isaacriehm/cairn/agents-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.
<a href="https://agentmods.dev/instructions/isaacriehm/cairn/agents-md"><img src="https://agentmods.dev/badge/instructions/isaacriehm/cairn/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.02258 | $0.02258 |
| Opus 5.5 | $0.00903 | $0.00903 |
| Sonnet 5.5 | $0.00452 | $0.00452 |
| Haiku 4.5 | $0.00226 | $0.00226 |
Grade A, and why
cairn AGENTS.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 14d 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.
How it starts
The opening of the file, as written. The whole thing — 169 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Cairn — Agent Orientation
This is the portable instruction entrypoint for Claude Code, Cursor, and
Codex. It is the table of contents for agents working on this repo. Real
content lives in docs/.
What this project is
Cairn = state + context-loading layer for AI coding agents. It curates
.cairn/ground/ (decisions, §V invariants, canonical-map, brand,
quality-grades), exposes that state via an MCP server, and ships a shared
agent plugin that wires adoption + the daily flow inline.
Claude Code, Cursor, and Codex are supported from one plugin package and
runtime. The CLI (cairn ...) is the bootstrap and debug entrypoint. There
is no separate orchestration runtime; agents use their native dispatch tools.
Document index
| What | Where |
|---|---|
| Quick start + concepts | README.md |
| Layered architecture (locked) | docs/ARCHITECTURE.md |
| Plugin spec — adoption phases, hooks, multi-dev enforcement (locked) | docs/PLUGIN_ARCHITECTURE.md |
| MCP tool surface — tool-by-tool reference | docs/MCP_SURFACE.md |
.cairn/ directory contract |
docs/FILESYSTEM_LAYOUT.md |
| License | LICENSE |
Operator profile (apply when communicating with the operator)
| Trait | Behavior |
|---|---|
| Communication | Terse-direct. Lead with answer or action. No filler. |
| Decisions | Fast-intuitive. Don't present options unless explicitly asked. When the operator states a decision, treat it as final. |
| Explanations | Concise. Root cause in 1-2 sentences then the fix. |
| UX philosophy | Design-conscious. UX is equal in importance to functional correctness. |
| Vendor choices | Opinionated. Do not suggest alternative libraries / frameworks unless they avoid a real risk. |
| Configuration | Hardcode values and paths in code. Do not add environment variables for configuration. Model selection follows the hard rule below. |
| Tests | Verification means sensors and end-to-end smokes against real state. No unit-test framework and no unit-test framing. |
| Backward compat | No backward-compatibility shims. Hard cutovers only. |
| Mobile mode | When the operator is on mobile, AskUserQuestion options get truncated; switch to chat-mode A/B/C with concise option labels. |
| Chat style | Chat replies may use compressed shorthand. Documents stay in full English. |
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.
- 14d ago Changed · +1 lines · +77 tokens per session 76214b0869d4
- 1mo ago First seen · 168 lines · 2,181 tokens per session scan A fbe3ce081ae9
cairn AGENTS.md is an instructions file published in the GitHub repository isaacriehm/cairn (6 stars, last pushed 14d ago), licensed MIT. It adds 2,258 tokens to every session, about $0.0090 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.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
deno copilot-instructions.md
Copilot instructions for denoland/deno, covering deno development guide for github copilot, network access, high level overview, key directories and key files to understand first.