Claude reads entire files to find what it needs. Lumen gives it a map.

Lumen is a 100% local semantic code search engine for AI coding agents. No API keys, no cloud, no external database, just open-source embedding models (Ollama or LM Studio), SQLite, and your CPU. A single static binary and your own local embedding server.

The payoff is measurable and reproducible: across 8 benchmark runs on 8 languages and real GitHub bug-fix tasks, Lumen cuts cost in every single language — up to 39%. Output tokens drop by up to 66%, sessions complete up to 53% faster, and patch quality is maintained in every task. All verified with a transparent, open-source benchmark framework that you can run yourself.

• Demo
• Quick start
• What you get
• How it works
• Benchmarks
• Supported languages
• Configuration
  • Supported embedding models
• Controlling what gets indexed
• Database location
• CLI Reference
• Troubleshooting
• Development

Claude Code asking about the Prometheus codebase. Lumen's semantic_search finds the relevant code without reading entire files.

Prerequisites:

Platform support: Linux, macOS, and Windows. File locking for background indexing coordination uses flock(2) on Unix and LockFileEx on Windows (via gofrs/flock).

1. Ollama installed and running, then pull the default embedding model:

   ollama pull ordis/jina-embeddings-v2-base-code

2. One of: Claude Code, Cursor, Codex, or OpenCode

Note: Installation differs by platform. Claude Code is installed from a plugin marketplace. Codex uses a local MCP server plus native skill discovery. OpenCode installs from npm. Cursor packaging is shipped in this repository and is ready for Cursor's plugin distribution workflow.

Install:

Claude Code

/plugin marketplace add ory/claude-plugins
/plugin install lumen@ory

Verify by starting a new Claude session and running /lumen:doctor.

Cursor

Lumen ships a native Cursor plugin bundle in this repository:

• .cursor-plugin/plugin.json - plugin manifest
• mcp.json - local lumen MCP server wiring
• hooks/hooks-cursor.json - SessionStart hook
• skills/ - shared doctor and reindex skills

Use Cursor's plugin installation or distribution workflow with this bundle. Detailed packaging notes: .cursor-plugin/INSTALL.md

Verify by opening a new Cursor agent session and asking it to use the doctor skill or the Lumen semantic_search tool.

Codex

Quick install:

Fetch and follow instructions from https://raw.githubusercontent.com/ory/lumen/refs/heads/main/.codex/INSTALL.md

Manual install:

CODEX_HOME="${CODEX_HOME:-$HOME/.codex}"
git clone https://github.com/ory/lumen.git "$CODEX_HOME/lumen"
mkdir -p "$HOME/.agents/skills"
ln -s "$CODEX_HOME/lumen/skills" "$HOME/.agents/skills/lumen"
codex mcp add lumen -- "$CODEX_HOME/lumen/scripts/run.sh" stdio

Detailed docs: .codex/INSTALL.md

Verify with:

codex mcp get lumen
ls -la "$HOME/.agents/skills/lumen"

OpenCode

Add @ory/lumen-opencode to the plugin array in your opencode.json:

{
  "plugin": ["@ory/lumen-opencode"]
}

Detailed docs: .opencode/INSTALL.md

Verify with:

opencode mcp list

Updating

• Claude Code - update through Claude's plugin marketplace
• Cursor - refresh or reinstall the bundled plugin through Cursor after updating this repository or the published package
• Codex - cd "${CODEX_HOME:-$HOME/.codex}/lumen" && git pull
• OpenCode - update the version pin in opencode.json (e.g. @ory/[email protected]) and restart OpenCode

On first Claude Code or Cursor session start, Lumen:

1. Downloads the binary automatically from the latest GitHub release
2. Indexes your project in the background using Merkle tree change detection
3. Registers a semantic_search MCP tool that the host can use automatically

In Codex and OpenCode, the same binary download and index seeding happen on the first semantic_search call.

Two shared skills are also available: doctor (health check) and reindex (forced re-indexing). Claude exposes them as /lumen:doctor and /lumen:reindex; the other hosts discover the same shared skill content through their native skill systems.

The same semantic_search, health_check, and index_status MCP tools plus the shared doctor and reindex skills are exposed through the Codex, Cursor, and OpenCode surfaces as well. The first semantic_search call seeds or refreshes the index automatically.

• Semantic vector search — Claude finds relevant functions, types, and modules by meaning, not keyword matching
• Auto-indexing — indexes on session start, only re-processes changed files via Merkle tree diffing
• Incremental updates — re-indexes only what changed; large codebases re-index in seconds after the first run
• 11 language families — Go, Python, TypeScript, JavaScript, Rust, Ruby, Java, PHP, C/C++, C#
• Git worktree support — worktrees share index data automatically; a new worktree seeds from a sibling's index and only re-indexes changed files, turning minutes of embedding into seconds
• Zero cloud — embeddings stay on your machine; no data leaves your network
• Ollama and LM Studio — works with either local embedding backend

Lumen sits between your codebase and Claude as an MCP server. When a session starts, it walks your project and builds a Merkle tree over file hashes: only changed files get re-chunked and re-embedded. Each file is split into semantic chunks (functions, types, methods) using Go's native AST or tree-sitter grammars for other languages. Chunks are embedded and stored in SQLite + sqlite-vec using cosine-distance KNN for retrieval.

Files → semantic chunks → vector embeddings → SQLite/sqlite-vec → KNN search

When Claude needs to understand code, it calls semantic_search instead of reading entire files. The index is stored outside your repo (~/.local/share/lumen/<hash>/index.db), keyed by project path and model name — different models never share an index.

Lumen is evaluated using bench-swe: a SWE-bench-style harness that runs Claude on real GitHub bug-fix tasks and measures cost, time, output tokens, and patch quality — with and without Lumen. All results are reproducible: raw JSONL streams, patch diffs, and judge ratings are committed to this repository.

Key results — 8 runs across 8 languages, hard difficulty, real GitHub issues (ordis/jina-embeddings-v2-base-code, Ollama):

Cost was reduced in every language tested. Quality was maintained in every task — zero regressions. JavaScript and TypeScript show the most dramatic efficiency gains: same quality fixes in half the time with two-thirds fewer tokens. Even on tasks too hard for either approach (Rust), Lumen cuts the cost of failure by 39%.

See docs/BENCHMARKS.md for all 8 per-language deep dives, judge rationales, and reproduce instructions.

Supports 12 language families with semantic chunking (9 benchmarked):

Go uses the native Go AST parser for the most precise chunks. All other languages use tree-sitter grammars. See docs/BENCHMARKS.md for all 9 per-language benchmark deep dives.

All configuration is via environment variables:

¹ ordis/jina-embeddings-v2-base-code (Ollama), nomic-ai/nomic-embed-code-GGUF (LM Studio)

Dimensions and context length are configured automatically per model:

Switching models creates a separate index automatically. The model name is part of the database path hash, so different models never collide.

If your model is not in the registry above, set LUMEN_EMBED_DIMS to bypass the registry check. LUMEN_EMBED_CTX is optional and defaults to 8192.

Both variables can also override values for known models — useful when running a model variant with a longer context window or different output dimensions.

LUMEN_BACKEND=lmstudio
LM_STUDIO_HOST=http://localhost:8801
LUMEN_EMBED_MODEL=mlx-community/Qwen3-Embedding-8B-4bit-DWQ
LUMEN_EMBED_DIMS=4096
LUMEN_EMBED_CTX=40960   # optional, defaults to 8192

Lumen filters files through six layers: built-in directory and lock file skips → .gitignore → .lumenignore → .gitattributes (linguist-generated) → supported file extension. Only files that pass all layers are indexed.

.lumenignore uses .gitignore syntax. Place it in your project root (or any subdirectory) to exclude files that aren't in .gitignore but are noise for code search — generated protobuf files, test snapshots, vendored data, etc.

Index databases are stored outside your project:

~/.local/share/lumen/<hash>/index.db

Where <hash> is derived from the absolute project path, embedding model name, and binary version. Different models or Lumen versions automatically get separate indexes. No files are added to your repo, no .gitignore modifications needed.

You can safely delete the entire lumen directory to clear all indexes, or use lumen purge to do it automatically.

Git worktrees are detected automatically. When you create a new worktree (git worktree add or claude --worktree), Lumen finds a sibling worktree's existing index and copies it as a seed. The Merkle tree diff then re-indexes only the files that actually differ — typically a handful of files instead of the entire codebase. No configuration needed; it just works.

Download the binary from the GitHub releases page or let the plugin install it automatically.

lumen help

Ollama not running / "connection refused"

Start Ollama and verify the model is pulled:

ollama serve
ollama pull ordis/jina-embeddings-v2-base-code

Run /lumen:doctor inside Claude Code to confirm connectivity.

In Cursor, Codex, or OpenCode, use the shared doctor skill or call health_check and index_status directly.

Stale index after large refactor

Run /lumen:reindex inside Claude Code to force a full re-index, or:

lumen purge && lumen index .

In Codex, use the bundled reindex skill to refresh the index through the MCP server, or run the same CLI commands for a clean rebuild. The same shared reindex skill is available in Cursor and OpenCode as well.

LM Studio: embedding model appears under LLMs instead of Embeddings

LM Studio classifies embedding models by matching the GGUF arch field against a hardcoded allowlist (bert, nomic-bert). Models built on other architectures — including Qwen2-based models like nomic-embed-code — are misclassified as LLMs. This affects lms ls output and the /v1/embeddings REST endpoint.

Fix (GGUF, v0.3.16+): Open LM Studio → My Models, click the gear icon next to the model, set Override Domain Type → Text Embedding.

macOS / Apple Silicon: MLX format models are significantly faster on Apple Silicon. However, LM Studio removed the domain type override for MLX in v0.3.30+, so MLX embedding models cannot be reclassified. Use the GGUF variant to retain the override option, or switch to Ollama (ordis/jina-embeddings-v2-base-code or qwen3-embedding:8b).

Switching embedding models

Set LUMEN_EMBED_MODEL to a model from the supported table above. Each model gets its own database; the old index is not deleted automatically.

Slow first indexing

The first run embeds every file. Subsequent runs only process changed files (typically a few seconds). For large projects (100k+ lines), first indexing can take several minutes — this is a one-time cost.

git clone https://github.com/ory/lumen.git
cd lumen

# Build locally (CGO required for sqlite-vec)
make build-local

# Run tests
make test

# Run linter
make lint

# Load as a Claude Code plugin from source
make plugin-dev

See CLAUDE.md for architecture details, design decisions, and contribution guidelines, and AGENTS.md for repo-specific agent instructions.