A one-time skill for examining a new project and setting up Cairn's stored project information. Cairn is the system used here to track project decisions, invariants, and related context.

Use it when bringing a project into Cairn, guiding the adoption phases, and choosing how the project should be examined and recorded.

It creates an initial shared understanding of the project so later Cairn workflows can operate on the codebase's actual structure and rules.

cairn-adopt — Skill for Claude Code by isaacriehm

Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code

/plugin marketplace add isaacriehm/cairn

Claude Code

/plugin install cairn

Made for: Claude Code.

Or install cairn, the plugin that ships this one along with the rest of its 5 skills, 4 commands, 5 agents, 5 hooks, 1 MCP server.

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/skills/isaacriehm/cairn/cairn-adopt/github.svg)](https://agentmods.dev/skills/isaacriehm/cairn/cairn-adopt)

Your own site

<a href="https://agentmods.dev/skills/isaacriehm/cairn/cairn-adopt"><img src="https://agentmods.dev/badge/skills/isaacriehm/cairn/cairn-adopt/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/skills/isaacriehm/cairn/cairn-adopt"><img src="https://agentmods.dev/badge/skills/isaacriehm/cairn/cairn-adopt.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 17 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 10,443 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 2 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	$0.00017	$0.10443
Opus 5	$0.00009	$0.05221
Sonnet 5	$0.00003	$0.02089
Haiku 4.5	$0.00002	$0.01044

Measured 9d ago against content hash ea16d54a8047, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade B, and why

cairn-adopt scanned grade B with 2 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 9d 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.

Reads agent configuration directoriesmediumAgent snooping

.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.

const p=os.homedir()+"/.claude/settings.json";

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

const cp=require("node:child_process");

packages/cairn-plugin/skills/cairn-adopt/SKILL.md · 796 lines

How it starts

The opening of the file, as written. The whole thing — 796 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill: cairn-adopt

Host portability

This skill is shared by Claude Code, Cursor, and Codex. Tool names in this file describe capabilities, not a required vendor API:

Resolve Cairn MCP tools with the host's native tool-discovery mechanism. ToolSearch(...) is the Claude Code spelling; Codex and Cursor use their equivalent discovery surface.
AskUserQuestion means the host's structured question UI. If unavailable, ask the same concise A/B/C question in chat and pause for the answer.
Named subagents live under ../../agents/. Claude Code may dispatch them by name; other hosts read the matching brief and pass it to their native subagent tool. If the host has no subagent tool, execute the brief inline.

You are guiding the operator through one-time Cairn adoption for the current project. Adoption is visual, comprehensive, and one-time — once finished, Cairn runs invisibly forever. Refer to docs/PLUGIN_ARCHITECTURE.md §6 for the canonical phase sequence.

Step 0 — preload tools

Open the skill with one ToolSearch call that batch-loads every deferred tool the loop needs. This avoids one round-trip per phase. Use the fully-qualified MCP tool names (the bare cairn_… form silently no-ops in select:). AskUserQuestion is built-in and stays unprefixed.

ToolSearch(select:mcp__plugin_cairn_cairn__cairn_init_resume,mcp__plugin_cairn_cairn__cairn_init_run,mcp__plugin_cairn_cairn__cairn_decision_get,mcp__plugin_cairn_cairn__cairn_resolve_attention,mcp__plugin_cairn_cairn__cairn_attention_dedup,AskUserQuestion)

After this single call all phase tools + the question tool + the attention resolver are loaded for the rest of the skill.

Trigger gate

Before doing anything else, classify the project's adoption state. There are three buckets, NOT two — fresh, mid-adoption, and fully adopted — because Phase 4-seed writes .cairn/config.yaml very early. A simple ls .cairn check can't distinguish "operator quit during Phase 7" from "adoption finished cleanly N sessions ago."

Read the full file on GitHub · 796 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.

9d ago First seen · 796 lines · 17 tokens per session scan B ea16d54a8047

Subscribe to this mod's changes

cairn-adopt is a skill published in the GitHub repository isaacriehm/cairn (6 stars, last pushed 1mo ago), licensed MIT. It adds 17 tokens to every session and 10,443 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it B with 2 findings (reads agent configuration directories, runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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