lumen — Claude Code plugin: local semantic code search via MCP
Indexes your project with Go AST parsing and finds code by meaning instead of reading whole files. Runs locally, no cloud and no API keys.
/plugin install lumen@claude-plugins-official
/plugin marketplace add anthropics/claude-plugins-community
/plugin install ory-lumen@claude-community
/plugin marketplace add anthropics/claude-plugins-officialWhat lumen does
Lumen is an MCP server for semantic code search. It parses files with Go AST, computes embeddings on a local model, and exposes a semantic_search tool to the agent. Claude gets back only the fragments that match the query, not entire files.
You need Ollama running with the embedding model pulled first: ollama pull ordis/jina-embeddings-v2-base-code. No local embedding server means no search, so check that before anything else. The plugin then downloads its binary from GitHub releases, indexes the project in the background, and registers the MCP tool. Indexing uses Merkle tree change detection, so later runs only touch files that changed.
Alongside semantic_search there are health_check and index_status tools, plus two shared skills: doctor for a health check and reindex for forced re-indexing. In Claude they run as /lumen:doctor and /lumen:reindex. Linux, macOS and Windows are supported.
What it helps with
- find a function from a description without opening dozens of files
- cut token spend on reading through a codebase
- re-index a project after a large refactor
- verify that the MCP server and embedding model actually work
- search code without shipping sources to a cloud service
Example prompts for the agent
- use semantic_search to find where request authorization is handled
- run /lumen:doctor and tell me if indexing is healthy
- force a re-index with /lumen:reindex
How to install lumen
Plugin marketplace
/plugin install lumen@claude-plugins-official/plugin marketplace add anthropics/claude-plugins-community/plugin install ory-lumen@claude-community/plugin marketplace add anthropics/claude-plugins-officialStep by step, with commands for each platform: Claude Code plugins: marketplaces, installing, and building your own
Questions about lumen
How do I install lumen in Claude?
Add the marketplace first: /plugin marketplace add anthropics/claude-plugins-official, then install the plugin: /plugin install lumen@claude-plugins-official. Start a new session and run /lumen:doctor to verify.
What does lumen do?
It builds a local semantic index of your project and gives Claude a semantic_search MCP tool. The agent locates relevant code by meaning rather than reading files end to end.
What does lumen need to run?
A running Ollama instance with the ordis/jina-embeddings-v2-base-code model. Embeddings are computed locally, so no external database or API key is involved.
