Srclight

Deep code indexing for AI agents. SQLite FTS5 + tree-sitter + embeddings + MCP.

Srclight builds a rich, searchable index of your codebase that AI coding agents can query instantly — replacing dozens of grep/glob calls with precise, structured lookups. It is the most comprehensive code intelligence MCP server available: 42 tools covering symbol search, relationship graphs, community detection, impact analysis, git change intelligence, semantic search, build system awareness, and document extraction — capabilities no other single MCP server combines. Fully local and private: your code never leaves your machine.

Why?

AI coding agents (Claude Code, Cursor, etc.) spend 40-60% of their tokens on orientation — searching for files, reading code to understand structure, hunting for callers and callees. Srclight eliminates this waste.

Without Srclight	With Srclight
8-12 grep rounds to find callers	get_callers("lookup") — one call
Read 5 files to understand module	codebase_map() — instant overview
"Find code that does X" → 20 greps	semantic_search("dictionary lookup") — one call
Edit a function, break 47 callers	detect_changes() — shows blast radius before you commit
15-25 tool calls per bug fix	5-8 tool calls per bug fix

Features

• Minimal dependencies — single SQLite file per repo, no Docker/Redis/vector DB
• Fully offline — no API calls, works air-gapped (Ollama local embeddings)
• Incremental — only re-indexes changed files (content hash detection)
• 11 languages — Python, C, C++, C#, JavaScript, TypeScript, PHP, Dart, Swift, Kotlin, Java, Go
• 10 document formats — PDF, DOCX, XLSX, HTML, CSV/TSV, email (.eml), images (PNG/JPG/SVG/etc.), plain text, RST, Markdown
• Optional OCR — PaddleOCR for scanned/image-only PDF pages; pytesseract for images
• 4 search modes — symbol names, source code (trigram), documentation (stemmed), semantic (embeddings)
• Hybrid search — RRF fusion of keyword + semantic results for best accuracy
• Multi-repo workspaces — search across all your repos simultaneously via SQLite ATTACH+UNION
• MCP server — works with Claude Code, Cursor, and any MCP client
• CLI — index, search, and inspect from the terminal
• Auto-reindex — git post-commit/post-checkout hooks keep indexes fresh

Requirements

• Python 3.11+
• Git (for change intelligence and auto-reindex hooks)
• Ollama (optional, for semantic search / embeddings) — ollama.com
• NVIDIA GPU + cupy (optional, for GPU-accelerated vector search)
• Poppler (optional, for PaddleOCR scanned-PDF support) — apt install poppler-utils / brew install poppler

Quick Start

# Install from PyPI
pip install srclight

# Install from source
git clone https://github.com/srclight/srclight.git
cd srclight
pip install -e .

# Optional: document format support (PDF, DOCX, XLSX, HTML, images)
pip install 'srclight[docs,pdf]'

# Optional: OCR for scanned PDFs (also needs poppler-utils on your system)
pip install 'srclight[pdf,paddleocr]'

# Optional: OCR for images (needs tesseract on your system)
pip install 'srclight[docs,ocr]'

# Optional: GPU-accelerated vector search (requires CUDA 12.x)
pip install 'srclight[gpu]'

# Everything (docs + pdf + ocr + paddleocr + gpu)
pip install 'srclight[all]'

# Index your project
cd /path/to/your/project
srclight index

# Index with embeddings (requires Ollama running)
srclight index --embed qwen3-embedding

# Search
srclight search "lookup"
srclight search --kind function "parse"
srclight symbols src/main.py

# Start MCP server (for Claude Code / Cursor)
srclight serve

Note: srclight index automatically adds .srclight/ to your .gitignore. Index databases and embedding files can be large and should never be committed.

Semantic Search (Embeddings)

Srclight supports embedding-based semantic search for natural language queries like "find code that handles authentication" or "where is the database connection pool".

Setup

# Install Ollama (https://ollama.com)
# Pull an embedding model
ollama pull qwen3-embedding       # Best quality (8B params, needs ~6GB VRAM)
ollama pull nomic-embed-text      # Lighter alternative (137M params)

# Index with embeddings
srclight index --embed qwen3-embedding

# Or index workspace with embeddings
srclight workspace index -w myworkspace --embed qwen3-embedding

How It Works

1. Each symbol's name + signature + docstring + content is embedded as a float vector
2. Vectors are stored as BLOBs in symbol_embeddings table (SQLite)
3. After indexing, a .npy sidecar snapshot is built and loaded to GPU VRAM (cupy) or CPU RAM (numpy) for fast search
4. semantic_search(query) embeds the query and runs cosine similarity against the GPU-resident matrix (~3ms for 27K vectors on a modern GPU)
5. hybrid_search(query) combines FTS5 keyword results + embedding results via Reciprocal Rank Fusion (RRF)

Embedding Providers

Provider	Model	Quality	Local?	Notes
Ollama (default)	qwen3-embedding	Best local	Yes	Needs ~6GB VRAM
Ollama	nomic-embed-text	Good	Yes	Lighter, works on 8GB VRAM
Voyage AI (API)	voyage-code-3	Best overall	No	Requires VOYAGE_API_KEY

# Use Voyage Code 3 (API, highest quality)
VOYAGE_API_KEY=your-key srclight index --embed voyage-code-3

Storage

Embeddings are stored in symbol_embeddings table in .srclight/index.db. After indexing, a .npy sidecar snapshot is built for fast GPU loading:

File	Purpose
index.db	Write path — per-symbol CRUD during indexing
embeddings.npy	Read path — contiguous float32 matrix for GPU/CPU search
embeddings_norms.npy	Pre-computed row norms (avoids recomputation per query)
embeddings_meta.json	Symbol ID mapping, model info, version for cache invalidation

For ~27K symbols at 4096 dims (qwen3-embedding), that's ~428 MB on disk, ~450 MB in VRAM. Incremental: only re-embeds symbols whose content changed; sidecar rebuilt after each indexing run.

Multi-Repo Workspaces

Search across multiple repos simultaneously. Each repo keeps its own .srclight/index.db; at query time, srclight ATTACHes them all and UNIONs across schemas.

# Create a workspace
srclight workspace init myworkspace

# Add repos
srclight workspace add /path/to/repo1 -w myworkspace
srclight workspace add /path/to/repo2 -w myworkspace -n custom-name

# Index all repos (with optional embeddings)
srclight workspace index -w myworkspace
srclight workspace index -w myworkspace --embed qwen3-embedding

# Search across all repos
srclight workspace search "Dictionary" -w myworkspace
srclight workspace search "Dictionary" -w myworkspace --project repo1

# Status
srclight workspace status -w myworkspace
srclight workspace list

# Start MCP server in workspace mode
srclight serve --workspace myworkspace

Git submodules are not indexed automatically — git ls-files does not recurse into them. To index a submodule, clone it separately and add it as its own workspace project. See docs/usage-guide.md for details.

MCP Integration

Srclight supports two transport modes: stdio (one server per session) and SSE (persistent server, multiple sessions). SSE is recommended for workspaces.

Claude Code

Stdio (simplest — one server per session):

# Single repo
claude mcp add srclight -- srclight serve

# Workspace mode
claude mcp add srclight -- srclight serve --workspace myworkspace

# Make it available in all projects (user scope)
claude mcp add --scope user srclight -- srclight serve --workspace myworkspace

SSE (persistent server — recommended for workspaces):

Run srclight as a long-lived server, then point Claude Code at it:

# Start the server (default: http://127.0.0.1:8742/sse)
srclight serve --workspace myworkspace &

# Or install as a systemd user service (Linux/WSL)
# See docs/usage-guide.md for the service file

# Connect Claude Code to the running server
claude mcp add --transport sse srclight http://127.0.0.1:8742/sse

SSE mode supports multiple concurrent sessions and survives Claude Code restarts.

Cursor

SSE (recommended): Run srclight once, then connect Cursor to it. Best for responsiveness and no cold-start per session.

Start the server: srclight serve --workspace myworkspace (default SSE on port 8742).

• UI: Settings → Tools & MCP → Add new MCP server → Type: streamableHttp, URL: http://127.0.0.1:8742/sse.
• JSON (project .cursor/mcp.json or global ~/.cursor/mcp.json):

"srclight": {
  "url": "http://127.0.0.1:8742/sse"
}

Stdio (alternative): One server process per Cursor session.

• UI: Type: command, Command: srclight, Args: serve --workspace myworkspace (or serve for single-repo).
• JSON:

"srclight": {
  "command": "srclight",
  "args": ["serve", "--workspace", "myworkspace"]
}

For single-repo: "args": ["serve"]. Restart Cursor completely after adding the server.

Verify: In Cursor chat, ask "What projects are in the srclight workspace?" or "List srclight tools" — the agent should call list_projects() or show srclight tools.

OpenClaw

OpenClaw connects to srclight via mcporter, its built-in MCP tool server CLI.

# 1. Add srclight to mcporter's home config
mcporter config add srclight http://127.0.0.1:8742/sse \
  --transport sse --scope home \
  --description "Srclight deep code indexing"

# 2. Verify the connection
mcporter call srclight.list_projects

# 3. Restart the OpenClaw gateway to pick up the new server
systemctl --user restart openclaw-gateway  # if using systemd
# or: openclaw daemon restart

The OpenClaw agent can then use srclight tools via the mcporter skill:

mcporter call srclight.search_symbols query="my_function"
mcporter call srclight.get_callers symbol_name="MyClass" project="my-repo"
mcporter call srclight.hybrid_search query="authentication logic"

Prerequisite: Srclight must be running as an SSE server (see above). OpenClaw's mcporter connects over HTTP — stdio mode is not supported.

Claude Desktop (claude_desktop_config.json)

{
  "mcpServers": {
    "srclight": {
      "command": "srclight",
      "args": ["serve", "--workspace", "myworkspace"]
    }
  }
}

Any MCP Client (SSE)

Any MCP-compatible client can connect to the SSE endpoint:

http://127.0.0.1:8742/sse

MCP Tools (42)

Srclight exposes 42 MCP tools organized in seven tiers. The MCP server includes built-in instructions that guide AI agents on which tool to use and when — agents receive a session protocol, tool selection guide, and project parameter documentation automatically on connection.

Tier 1: Instant Orientation

Tool	What it does
codebase_map()	Full project overview — call first every session
search_symbols(query)	Search across symbol names, code, and docs
get_symbol(name)	Full source code + metadata for a symbol
get_signature(name)	Just the signature (lightweight)
symbols_in_file(path)	Table of contents for a file
list_projects()	All projects in workspace with stats

Tier 2: Relationship Graph

Tool	What it does
get_callers(name)	Who calls this symbol?
get_callees(name)	What does this symbol call?
get_dependents(name, transitive)	Blast radius — what breaks if I change this?
get_implementors(interface)	All classes implementing an interface
get_tests_for(name)	Test functions covering a symbol
get_type_hierarchy(name)	Inheritance tree (base classes + subclasses)

Tier 2b: Community & Impact Analysis

Tool	What it does
get_communities(project)	Auto-detected functional module clusters (Louvain algorithm)
get_community(name, project)	Which community a symbol belongs to, with all co-members
get_execution_flows(project)	Traced execution paths from entry points through the call graph
get_impact(name, project)	Blast radius + risk level (LOW / MEDIUM / HIGH / CRITICAL)
detect_changes(project, ref?)	Map git diff to affected symbols — aggregate blast radius of your edits

Tier 3: Git Change Intelligence

Tool	What it does
blame_symbol(name)	Who changed this, when, and why
recent_changes(n)	Commit feed (cross-project in workspace)
git_hotspots(n, since)	Most frequently changed files (bug magnets)
whats_changed()	Uncommitted work in progress
changes_to(name)	Commit history for a symbol's file

Tier 4: Build & Config

Tool	What it does
get_build_targets()	CMake/.csproj/npm targets with dependencies
get_platform_variants(name)	#ifdef platform guards around a symbol
platform_conditionals()	All platform-conditional code blocks

Tier 5: Semantic Search (Embeddings)

Tool	What it does
semantic_search(query)	Find code by meaning (natural language)
hybrid_search(query)	Best of both: keyword + semantic with RRF fusion
embedding_status()	Embedding coverage and model info

Tier 6: Meta & Server

Tool	What it does
index_status()	Index freshness and stats
reindex()	Trigger incremental re-index
embedding_health()	Check if the embedding provider (Ollama, etc.) is reachable
setup_guide()	Structured setup instructions for agents and users
server_stats()	Server uptime and process info
restart_server()	Request server restart (SSE only)

In workspace mode, search_symbols, get_symbol, codebase_map, and hybrid_search accept an optional project filter. Graph/git/build/community tools require project in workspace mode.

Deployment Guide

See docs/usage-guide.md for the full deployment and usage guide, including:

• Setting up srclight as a global MCP server for Claude Code
• Adding/removing repos from workspaces
• What happens on commits and branch switches
• Re-embedding workflows
• Troubleshooting

Auto-Reindex (Git Hook)

Keep indexes fresh automatically:

# Install post-commit + post-checkout hooks in current repo
srclight hook install

# Install across all repos in a workspace
srclight hook install --workspace myworkspace

# Remove hooks
srclight hook uninstall

The hooks run srclight index in the background after each commit and branch switch.

How It Works

1. tree-sitter parses every source file into an AST
2. Document extractors handle non-code files (PDF, DOCX, XLSX, HTML, CSV, images, email, text) — extracting headings, tables, pages, and metadata as searchable symbols. Scanned PDF pages are optionally OCR'd via PaddleOCR.
3. Symbols (functions, classes, methods, structs, etc.) are extracted with full metadata
4. Three SQLite FTS5 indexes are built with different tokenization strategies:
   • Names: code-aware tokenization (splits camelCase, handles ::, ->)
   • Content: trigram index for substring matching
   • Docs: Porter stemming for natural language in docstrings
5. Community detection clusters symbols into functional modules via Louvain algorithm on call-graph edges, with TF-IDF auto-labeling
6. Execution flows are traced via BFS from entry points, and impact analysis scores each symbol's blast radius (LOW/MEDIUM/HIGH/CRITICAL)
7. Optional: embedding vectors are generated via Ollama or Voyage API and stored as BLOBs
8. A .npy sidecar snapshot is built and loaded to GPU VRAM (cupy) or CPU RAM (numpy) for fast search
9. The MCP server exposes structured query tools that AI agents call instead of grep
10. Hybrid search merges keyword (FTS5) and semantic (embedding) results via RRF

Architecture (Workspace Mode)

repo1/.srclight/index.db  ──┐
repo2/.srclight/index.db  ──┼── ATTACH ──→ :memory: ──→ UNION ALL queries
repo3/.srclight/index.db  ──┘

Each repo is indexed independently. At query time, SQLite's ATTACH mechanism joins them into a single searchable namespace. Handles >10 repos via automatic batching (SQLite's ATTACH limit).

How Srclight Compares

A survey of 50+ MCP code intelligence servers across all major registries (Official MCP Registry, Smithery, Glama, mcp.so, awesome-mcp-servers) found that no other single server combines srclight's full capabilities:

Capability	srclight	grep/glob (default)	CodeMCP (SCIP)	Claude Context (Zilliz)
Symbol search (FTS5)	3 indexes (name, content, docs)	None	SCIP-based	BM25
Semantic search (embeddings)	GPU-accelerated, ~3ms	None	None	OpenAI API + Milvus
Hybrid search (keyword + semantic)	RRF fusion	None	None	BM25 + vector
Relationship graph (callers, callees)	tree-sitter edges	None	SCIP edges	None
Community detection (module clusters)	Louvain on call graph	None	None	None
Impact analysis (blast radius + risk)	Per-symbol + diff-level	None	None	None
Git change intelligence	blame, hotspots, WIP, detect_changes	None	None	None
Build system awareness	CMake, .csproj, #ifdef	None	None	None
Multi-repo workspace	ATTACH+UNION	None	None	None
Infrastructure required	pip install, SQLite	None	SCIP indexer	Docker, Milvus, OpenAI API
Fully local / private	Yes, zero API calls	Yes	Yes	No (needs OpenAI)
Languages	11	Any (regex)	5 (SCIP)	Any (chunking)
MCP tools	42	2 (grep, glob)	80+	~10

Unlike grep-based tools, srclight builds a persistent index with structured lookups. Unlike cloud-based solutions, everything runs locally — your code never leaves your machine. Unlike IDE plugins, srclight works with any MCP client.

Roadmap

Done

• Symbol intelligence + 3x FTS5 search
• Relationship graph: callers, callees, hierarchy
• Blast radius, test discovery, implementors
• Git change intelligence: blame, hotspots, recent changes
• Build system awareness: CMake, .csproj, platform conditionals
• Semantic search: embeddings via Ollama/Voyage, hybrid RRF
• GPU-accelerated vector search: .npy sidecar, cupy/numpy vectorized math
• Multi-repo workspaces (ATTACH+UNION)
• Auto-reindex git hooks (post-commit + post-checkout)
• Document extraction: PDF, DOCX, XLSX, HTML, CSV, email, images, text (heading detection, tables, metadata)
• Optional OCR: PaddleOCR for scanned PDFs, pytesseract for images
• MCP agent guidance: comprehensive instructions, tool selection guide, session protocol
• Workspace config hot-reload (no server restart needed to add repos)
• VectorCache sidecar re-discovery (no restart needed after embedding)
• Project name suggestions in error messages
• Community detection: Louvain clustering on call-graph edges with TF-IDF auto-labeling
• Execution flow tracing: BFS from entry points across community boundaries
• Impact analysis: per-symbol blast radius with risk scoring (LOW/MEDIUM/HIGH/CRITICAL)
• detect_changes: map git diff to affected symbols and aggregate blast radius

Next

• Cross-language concept mapping (explicit edges between equivalent symbols across languages)
• Pattern intelligence (convention detection, coding pattern extraction)
• AI pre-computation (symbol summaries via cheap LLM)

License

MIT — Gig8 LLC