Lightning Code Index (lci)

Sub-millisecond semantic code search over large corpora. ~80% context reduction versus Grep. Tree-sitter parsing across 13 languages. An MCP server for AI assistants, plus CLI, HTTP, and Unix-socket interfaces.

Version 0.6.0.

Quick start

Platform availability: prebuilt releases ship for Linux x86_64 (.tar.gz, .deb, .rpm), Windows x86_64 (.tar.gz), and macOS arm64 / Apple Silicon (.tar.gz). Intel (x86_64) macs are not yet served by a prebuilt binary — build from source on those. The installers fail fast with a clear message on any unsupported platform/arch.

One-line install (recommended)

# Linux / macOS
curl -fsSL https://raw.githubusercontent.com/standardbeagle/lci-cpp/main/install.sh | sh

# Windows (PowerShell)
irm https://raw.githubusercontent.com/standardbeagle/lci-cpp/main/install.ps1 | iex

Both detect your OS/arch, download the matching release binary, and install it (/usr/local/bin or ~/.local/bin on Unix; %LOCALAPPDATA%\Programs\lci on Windows). Override with LCI_PREFIX; pin a version with LCI_VERSION=0.6.0.

Via npm

npm install -g @standardbeagle/lci
lci --version

Via uv / pip

uv tool install lci-cli      # or: pipx install lci-cli
lci --version

The npm and uv packages download the prebuilt binary for your platform — no compiler required.

Updating

lci update            # self-update to the latest release
lci update --check    # report current vs latest without installing
lci update --version 0.6.0   # install a specific release

lci update works regardless of how lci was installed. Package-manager users can also run npm update -g @standardbeagle/lci or uv tool upgrade lci-cli.

From a release artifact

# Linux: tarball or Debian package
curl -fLO https://github.com/standardbeagle/lci-cpp/releases/download/v0.6.0/lci-0.6.0-Linux.tar.gz
tar -xzf lci-0.6.0-Linux.tar.gz
sudo install lci-0.6.0-Linux/bin/lci /usr/local/bin/

# or
sudo dpkg -i lci-0.6.0-Linux.deb

lci --version   # 0.6.0
lci search "myFunction"

From source

# Toolchain: GCC 13+ or Clang 17+, CMake 3.25+, vcpkg, Ninja
cmake --preset release \
  -DCMAKE_TOOLCHAIN_FILE=$VCPKG_ROOT/scripts/buildsystems/vcpkg.cmake
cmake --build build/release --parallel
./build/release/src/lci --version

# Install + package
cd build/release
sudo cmake --install .
cpack -G TGZ    # produces lci-0.6.0-Linux.tar.gz
cpack -G DEB    # produces lci-0.6.0-Linux.deb

The CPack output contains only bin/lci (~28 MB stripped). Tree-sitter grammars are statically linked; runtime dependencies are libc + libstdc++

• libssl + brotli (all standard on modern Linux).

What it does

Surface	Use
lci search PATTERN	substring + symbol-aware ranked search across the corpus
lci grep PATTERN	literal text search over the corpus, grep-style output
lci tree SYMBOL	function call hierarchy with annotations
lci def SYMBOL / lci refs SYMBOL	definition + reference lookup
lci git-analyze	analyze working-set changes for duplicates, naming, complexity
lci mcp	MCP (Model Context Protocol) server over stdio for AI assistants
lci server	long-running HTTP server over a Unix socket; per-corpus daemon
lci status, lci stats	index health + runtime metrics

Full CLI reference: lci --help or lci <command> --help.

MCP tools

lci mcp exposes 14 tools to AI assistants: search, find_files, get_context, context, list_symbols, inspect_symbol, browse_file, semantic_annotations, side_effects, code_insight, git_analysis, index_stats, debug_info, and info. Output is emitted in LCF (LCI Compact Format) — a token-dense, agent-oriented layout.

code_insight is the session-startup workhorse: repository map, health dashboard, entry points, complexity/coupling/cohesion statistics, module and feature breakdowns, naming vocabulary, and git change/hotspot analysis.

Full per-tool reference — parameters, modes, output shapes, errors — is in docs/TOOLS.md.

Architecture

• Indexer pipeline: scanner → parser pool (tree-sitter) → trigram bucketer (256-way sharded) → merger → search engine.
• Storage: in-memory trigram index, symbol store, reference tracker, postings list. No disk persistence today — re-indexes on server start.
• Hot path: lock-free RCU-style atomic snapshot for reads; mutex only on the write/indexing path. See .claude/rules/karpathy-principles.md for the performance discipline.
• Parser concurrency: per-language parser pools, one tree-sitter parser per worker. No global lock.

Languages

13 languages via vendored tree-sitter grammars: Go, Python, JavaScript, TypeScript (incl. TSX), Rust, C, C++, Java, C#, PHP, Kotlin, Zig, and Ruby. Cross-file import resolution is supported for Go, JavaScript, Python, Rust, C#, and C/C++.

Testing

cmake --build build/release --parallel
ctest --test-dir build/release --output-on-failure -j$(nproc)

The suite covers unit tests, integration tests (bundled per-binary for in-process cache amortization), real-project tests (chi, fastapi, trpc, pocketbase), regression snapshot tests, and google-benchmark performance gates.

Real-project tests fetch corpora via tests/parity/corpora/prep_real.sh and skip cleanly when corpora are absent.

Layout

src/                  binary + library
include/lci/          public-ish headers
tests/
  integration/        bundled per-process integration suite
  benchmarks/         google-benchmark perf gates
cmake/                custom CMake modules
.github/workflows/    CI + release

Status

Surface	State
C++ binary install	TGZ / DEB / RPM via CPack
MCP server	14 tools, all engine-backed
Performance	meets/beats every benchmark gate

License

MIT. See LICENSE.