LCI - Lightning Code Index

Lightning-fast code indexing and search for AI assistants.


Features

- Sub-millisecond search: Trigram-based indexing with <5ms search guarantee
- Multi-language support: Go, TypeScript, JavaScript, Python, Rust, C#, PHP, and more
- MCP integration: Model Context Protocol server for AI assistant integration
- Semantic search: Natural language queries with intelligent matching
- Call graph analysis: Track function calls, references, and dependencies
- Semantic annotations: @lci: vocabulary for marking up code with metadata

Installation

$3

``bash
npm install -g @standardbeagle/lci
`

$3

`bash
pip install lightning-code-index
`

$3

`bash
brew install standardbeagle/tap/lci
`

$3

Requires Go 1.24 or later (for go-fast JavaScript parser support).

`bash
go install github.com/standardbeagle/lci/cmd/lci@latest
`

$3

Download pre-built binaries from GitHub Releases.

Quick Start

$3

`bash


Index and search in current directory

lci search "handleRequest"

Find symbol definitions

lci def UserService

Find all references to a symbol

lci refs CreateUser

Display function call hierarchy

lci tree main

Fast grep-style search

lci grep "TODO|FIXME"

List files that would be indexed

lci list
`

$3

Start the MCP server for AI assistant integration:

`bash
lci mcp
`

#### Claude Code Integration

Add to your .mcp.json:

`json
{
"lci": {
"command": "lci",
"args": ["mcp"],
"env": {}
}
}
`

Configuration

Create .lci.kdl in your project root:

`kdl
project {
name "my-project"
root "."
}

index {
include "/.go" "/.ts" "*/.py"
exclude "/node_modules/" "/vendor/"
}

search {
max-results 100
context-lines 3
}
`

MCP Tools

When running as an MCP server, LCI exposes these tools:

| Tool | Description |
|------|-------------|
| search | Semantic code search with fuzzy matching |
| get_context | Get detailed context for a code symbol |
| find_files | Fast file path search with glob patterns |
| code_insight | Codebase intelligence and analysis |
| context | Save/load code context manifests |
| semantic_annotations | Query @lci: semantic labels |
| side_effects | Analyze function purity and side effects |

Semantic Annotations

Mark up your code with @lci: annotations for enhanced AI understanding:

`go
// @lci:risk[high] @lci:public-api
// @lci:requires[env:DATABASE_URL]
func HandleUserLogin(w http.ResponseWriter, r *http.Request) {
// ...
}

// @lci:purpose[Validate user credentials against database]
// @lci:must[Return error for invalid credentials]
func ValidateCredentials(username, password string) error {
// ...
}
`

$3

- Risk & Safety: @lci:risk[low|medium|high|critical], @lci:safe-zone, @lci:stability
- Dependencies: @lci:requires[env:VAR], @lci:requires[db:table], @lci:requires[service:name]
- Conventions: @lci:convention[pattern], @lci:idiom[name], @lci:template[name]
- Contracts: @lci:must[behavior], @lci:must-not[behavior], @lci:invariant[condition]
- Purpose: @lci:purpose[description], @lci:domain[area], @lci:owner[team]

Architecture

`
lci/
├── cmd/lci/ # CLI entry point
├── internal/
│ ├── core/ # Trigram index, symbol store, reference tracker
│ ├── parser/ # Tree-sitter based multi-language parsing
│ ├── search/ # Search engine and scoring
│ ├── indexing/ # Master index and pipeline
│ ├── mcp/ # MCP server and tools
│ └── analysis/ # Code analysis and metrics
└── pkg/ # Public API
`

Performance

LCI is designed for speed:

- Indexing: <5s for typical projects (<10k files)
- Search: <5ms for most queries
- Memory: <100MB for typical web projects
- Startup: Near-instant with persistent index

Development

`bash


Run tests

go test ./...

Build

go build ./cmd/lci

Run with race detector

go test -race ./...
``

License

MIT License - see LICENSE for details.

Contributing

Contributions are welcome! Please read the contributing guidelines before submitting PRs.