What is the purpose of the .metis/code-index.md file?

It serves as a structured map that helps AI agents understand project layout, symbol locations, and semantic logic without needing to read every source file individually.

Does the code index update automatically?

Yes, it uses PostToolUse hooks to track changes to .metis/.index-dirty and can automatically run incremental updates during PreCompact or Stop events.

What is the difference between Layer 1 and Layer 2 indexing?

Layer 1 is a fast, deterministic structural extraction of symbols (what exists), while Layer 2 uses AI to create semantic summaries (what the code means and how it relates to other parts).

Why does the summarizer need specific Edit permissions?

To run the summarization process in the background without constant manual approval, the user must grant the agent Edit access to the .metis/code-index.md file via the /permissions command.

Codebase Indexer & Navigator

Name: Codebase Indexer & Navigator
Author: colliery-io

bycolliery-io

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Productivity & Workflow

Generates a comprehensive codebase map with structural symbol extraction and semantic AI summaries for improved agent navigation.

The Code Index skill optimizes AI agent performance by maintaining a two-layer map of your project within a .metis/code-index.md file. It combines high-speed, deterministic structural indexing via tree-sitter with deep semantic summaries generated by a specialized AI subagent to explain key abstractions, symbol relationships, and internal logic. This allows Claude and other agents to navigate large or unfamiliar codebases with significantly higher accuracy, reducing the need for expensive manual file exploration.

Key Features

01Co-located summaries and symbols for easy AI-agent context retrieval

02Dual-layer indexing combining fast structural tree-sitter analysis with semantic AI summaries

038 GitHub stars

04Automated background summarization using the specialized code-index-summarizer subagent

05PostToolUse hooks to automatically track source changes and prepare index updates

06Incremental update system that tracks modified files and only refreshes stale sections

Use Cases

01Onboarding an AI agent to a large, complex, or legacy codebase for the first time

02Maintaining an up-to-date architectural map after major refactors or directory restructures

03Improving AI reasoning regarding cross-module dependencies and non-obvious code behaviors

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add colliery-io/metis code-index

For use in Claude.ai and ChatGPT

Download Skill