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Agent skill

Arch Index

by coco-research in coco-research/coco

Build and validate .arch/index.json — a committed map from each architectural component of this repository to the real directories and files that implement it, pinned to a git commit, with every…

Custom licenceAuto-check passedDevelopment

Install Arch Index

skills CLI
$ npx skills add coco-research/coco --skill arch-index -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install coco-research/coco arch-index --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/coco-research/coco.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/arch-index .claude/skills/arch-index && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
arch-index
GitHub stars
503
Token cost
~2.8k tokens
SKILL.md length
1,366 words
Files
20 (incl. scripts, references)
Skills in repo
63
Repo updated
First seen
Licence
Custom licence

At a glance

Build and validate .arch/index.json — a committed map from each architectural component of this repository to the real directories and files that implement it, pinned to a git commit, with every…

  • Works in 3 steps: If .planning/codebase/ exists, read… → Otherwise, if gitnexus is available for… → Otherwise crawl. Run…
  • Asked to map a codebase
  • SKILL.md covers What this skill is for, and…, Modes, Artifacts and Scope limits, stated plainly, plus 2 more sections
  • Runs Python and Shell scripts from its folder; calls python3, git and bash

What it does

Arch Index is an agent skill from coco-research/coco. Build and validate .arch/index.json — a committed map from each architectural component of this repository to the real directories and files that implement it, pinned to a git commit, with every path verified to exist. Also detects structural drift between that index and the current code. Use when asked to map a codebase, produce a component or code-ownership index, find which files implement a component, check whether architecture docs are stale, or detect architecture drift after a refactor. Triggers include…

Its SKILL.md is about 2.8k tokens, which your agent loads only when the skill is triggered. The skill folder holds 22 other files, including scripts and reference files (for example `references/analysis-taxonomy.md`, `references/arch-plan.md` and `references/component-rules.md`).

It sits in Development, covering Commit messages. The repository describes itself as: CoCo Super Intelligence is the orchestration layer that turns Claude Code, Cursor, or Codex into an engineering department: a routed advisory board, 226 skills, 386 commands…

When your agent uses it

  • Asked to map a codebase
  • Produce a component
  • Code-ownership index
  • Find which files implement a component

Example prompts

  • “map the codebase”
  • “component index”
  • “which files implement X”
  • “/arch-index”

Requirements

  • Python 3
  • A Bash shell

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

  1. If .planning/codebase/ exists, read ARCHITECTURE.md, STRUCTURE.md,
  2. Otherwise, if gitnexus is available for this repository, call
  3. Otherwise crawl. Run scripts/repo_tree.py --repo-root . for a filtered,

What it can do on your machine

Read from SKILL.md and the folder at commit d79d33a. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships 11 files in scripts/ (Python and Shell, from the files we listed), which the agent can run.

    Shell commands in SKILL.md call:

    • python3
    • git
    • bash

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • github.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Arch Index loads about 2.8k tokens when it runs, and up to ~11k if it reads all its reference files. Until then it costs about 172 tokens; SKILL.md has 1,366 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~172
When it runs · the whole SKILL.md, loaded when a task matches
~2.8k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~11k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

Its licence (Custom licence) doesn't allow us to republish the file, so here is its outline and opening line. It has 1,366 words (~2,801 tokens).

“Produces one artifact: .arch/index.json, a commit-pinned map from each architectural component of a repository to the real directories and files that implement it. Every claimed path is verified to exist by a script with an exit code, not by a…”

— opening of SKILL.md by coco-research, Custom licence
name
arch-index
domain
engineering
version
1.0.0

Read the full SKILL.md on GitHub

Files

SKILL.md and 19 other files (scripts, references) in skills/arch-index of coco-research/coco.

  • SKILL.md
  • references/analysis-taxonomy.md
  • references/arch-plan.md
  • references/component-rules.md
  • references/schema.md
  • references/tool-frugality.md
  • scripts/arch_drift.py
  • scripts/fixtures/bad-invariants.json
  • scripts/fixtures/bad-paths.json
  • scripts/fixtures/good.json
  • scripts/fixtures/plan-bad-shape.json
  • scripts/fixtures/plan-good.json
  • scripts/fixtures/plan-unbuilt.json
  • scripts/repo_tree.py
  • scripts/run_fixtures.sh
  • scripts/validate_index.py
  • scripts/verify_arch_plan.py
  • templates
  • … and 2 more

Open the folder on GitHubat commit d79d33a

Compare with similar skills

Arch Index next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Arch Index compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Arch Index this skillcoco-research/coco503—~2.8kAutomated safety check: PassCustom licence
Contextual Commit Messagesyamadashy/repomix29k1 repos~2.7kAutomated safety check: PassMIT
React Router Release Notes Prepremix-run/react-router57k—~1.1kAutomated safety check: PassMIT
Caveman Commitvishiri/fantasia-archive40913 repos~642Automated safety check: PassGPL-3.0
PR Finalize Reviewmicrosoft/garnet12k—~3.1kAutomated safety check: PassMIT
ToolJet Multi-Repo CommitToolJet/ToolJet41k—~1.3kAutomated safety check: PassAGPL-3.0

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Categories

Questions about Arch Index

What does Arch Index do?

Build and validate .arch/index.json — a committed map from each architectural component of this repository to the real directories and files that implement it, pinned to a git commit, with every…. Arch Index is an agent skill from coco-research/coco.json — a committed map from each architectural component of this repository to the real directories and files that implement it, pinned to a git commit, with every path verified to exist.

When should I use Arch Index?

Arch Index fits situations like: asked to map a codebase; produce a component; code-ownership index; find which files implement a component.

How do I install Arch Index in Claude Code?

Run `npx skills add coco-research/coco --skill arch-index -a claude-code`. Or copy the skill folder (skills/arch-index in coco-research/coco) into .claude/skills/arch-index in your project. Claude Code loads it when a task matches its description.

How do I install Arch Index in Codex?

Run `npx skills add coco-research/coco --skill arch-index -a codex`. Or copy the skill folder (skills/arch-index in coco-research/coco) into .agents/skills/arch-index in your project. Codex loads it when a task matches its description.

Can I use Arch Index in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add coco-research/coco --skill arch-index -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/arch-index, .gemini/skills/arch-index, .github/skills/arch-index and .opencode/skills/arch-index in your project.

What does Arch Index need to run?

Going by SKILL.md and its folder, Arch Index needs Python and a shell for the scripts in its folder and the command-line tools its instructions call (python3, git and bash). Our summary lists: Python 3; A Bash shell.

Does Arch Index access the network?

SKILL.md names 1 domain. As links in the text: github.com. This is read from the text; nothing was executed.

Is Arch Index safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Arch Index use?

Arch Index has a licence file (the repository's licence) that doesn't match a standard licence. Read it on GitHub before reusing the skill.

How many tokens does Arch Index use?

About 2.8k tokens (SKILL.md is roughly 11k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 8.5k tokens, read only when the agent opens those files.

What are the alternatives to Arch Index?

Skills that share tags, products or a category with Arch Index: Contextual Commit Messages (yamadashy/repomix, 29k stars), React Router Release Notes Prep (remix-run/react-router, 57k stars), Caveman Commit (vishiri/fantasia-archive, 409 stars) and PR Finalize Review (microsoft/garnet, 12k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Arch Index?

coco-research (a GitHub user) maintains it in coco-research/coco, which has 503 GitHub stars. The repository holds 63 skills in this directory. The repository was last updated on October 9, 2026.

Source: coco-research/coco on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.