Show HN: Synapse – local codebase indexer and MCP server for Claude Code

Synapse, a local codebase indexer and MCP server for Claude Code, launched on Hacker News. The tool indexes project files locally and provides instant code context to Claude without sending data to the cloud, supporting multiple MCP-compatible clients. It aims to eliminate the need for developers to manually paste code snippets when asking Claude about their codebase.

Synapse Give Claude instant knowledge of your codebase — local, private, no cloud. You open Claude Code and ask: "Add retry logic to my API client." Without Synapse: Claude asks what your stack is. You paste 200 lines of code. You explain your conventions. You do this again tomorrow. With Synapse: Claude says: "Your API client in src/api/client.ts uses Axios with your custom RetryConfig interface — matching the pattern you used in payment.ts. Here's the implementation:" Synapse watches your project folders, indexes them locally, and connects to Claude via MCP. Claude knows your codebase without you saying a word. Install in 2 minutes pip install synapse-mcp synapse init C:/Projects/myapp Then paste one line into your Claude Desktop config. Done. What it does Watches your project folders — indexes code, markdown, and config files automatically Stores everything locally — no API key required, nothing leaves your machine Connects to Claude via MCP — works with Claude Desktop, Cursor, and any MCP client Updates in real time — re-indexes files as you save them Supported tools Tool Status Claude Code ✅ Supported primary target Cursor ✅ Supported via MCP Continue ✅ Supported via MCP Claude Desktop chat 🔜 Coming in v0.2 Any MCP client ✅ Standard MCP protocol Supported file types .py .ts .tsx .js .jsx .go .rs .java .kt .rb .php .cs .swift .cpp .c .h .sh .ps1 .sql .tf .md .json .yaml .toml .env .graphql .proto · Dockerfile · Makefile · and more Connect to Claude Code After running synapse init , register Synapse as an MCP server: claude mcp add synapse synapse-mcp That's it. Restart claude and run /mcp to confirm synapse shows connected · 2 tools. Claude Desktop chat support is planned for v0.2 via SSE transport. Track progress in 12. CLI reference synapse init Index a folder run this first synapse status Show what's indexed synapse search Search from the terminal synapse wipe Delete the local index Configuration Synapse works out of the box with no config file required. To customize, create ~/.synapse/config.toml: synapse watch paths = "C:/Projects/myapp", "C:/Projects/clientwork" ignore patterns = "node modules", ".git", "dist", " .pyc" embedding provider = "local" "local" default, free, private or "openai" chunk size = 512 chunk overlap = 64 Local embeddings default : Uses nomic-embed-text-v1.5 via sentence-transformers. Downloads ~400MB on first run. Free. Nothing leaves your machine. OpenAI embeddings optional : Set provider = "openai" and OPENAI API KEY env var. Slightly better quality for natural language queries. Costs ~$0.00 for personal use. How it works Your files → Synapse watches → Chunks text → Embeds locally → Stores in LanceDB ↓ Claude Desktop ←── MCP query ←── Synapse MCP server ←── Semantic search synapse init walks your project and indexes every supported file The file watcher triggers incremental re-indexing on every save When you open Claude Desktop, the synapse-mcp server is available as a connected tool Claude calls recall "your question" automatically before answering Relevant code snippets are injected into Claude's context window No round trips to external servers. No accounts. No rate limits. FAQ Does my code leave my machine? No. With the default local embedding provider, every computation happens on your machine. The only network call is the initial model download ~400MB, cached permanently after that . What if I use the openai provider? Your code text is sent to OpenAI's API for embedding. If you work on sensitive or proprietary code, use the default local provider. How is this different from Cursor's built-in indexing? Cursor's index lives inside Cursor only. Synapse works with Claude Desktop, Cursor, Continue, and any other MCP-compatible client — all from one index. How is this different from ChatGPT Memory? ChatGPT Memory is locked to ChatGPT and stored on OpenAI's servers. Synapse works with any AI tool and stores everything locally. Will it index my .env files or secrets? Yes — it indexes .env files if they're in your watch path. If you don't want this, add .env to the ignore patterns list in your config. Can I inspect what's in the index? Yes: synapse status shows counts, and synapse search lets you query it directly. How do I remove a project from the index? Run synapse wipe to clear everything. Then run synapse init again with only the paths you want. Requirements Python 3.10+ 1 GB free disk space for the embedding model cache Claude Desktop or any MCP client Contributing Synapse is MIT-licensed and welcomes contributions. Good first issues: Add support for a new file type in synapse/ingestion/reader.py Improve chunking for a specific language Write integration tests To contribute: git clone https://github.com/nrkoka786/synapse https://github.com/nrkoka786/synapse cd synapse pip install -e ". dev " pytest tests/ See CONTRIBUTING.md for guidelines. Roadmap Core filesystem indexing Claude Code MCP integration Local embeddings no API key File watcher incremental re-indexing Claude Desktop chat support SSE transport — v0.2 Git log ingestion commit messages + PR descriptions Markdown + PDF document indexing synapse search TUI with rich output Windows installer .exe macOS App Synapse Cloud encrypted cross-device sync — planned Team Synapse shared org context — planned License MIT © 2026 NR · github.com/nrkoka786/synapse