Code Atlas MCP Server

code-atlas

Multi-language code intelligence MCP server — gives Claude Code (and any MCP client) a structured view of your codebase instead of raw text: symbol search, file outlines, AST pattern queries, cross-file references, call/type hierarchies, import graphs, Mermaid diagrams, precise LSP-backed answers, local-embedding semantic search, and game-engine asset understanding (Godot, Unity, Unreal).

Instead of grepping and reading whole files, the model asks questions like "outline this file", "who calls parseConfig?", "how does the request handler reach the DB layer?" — and gets compact, token-efficient answers backed by a persistent tree-sitter index.

Status: pre-release. All roadmap phases below are complete — 12 languages, LSP-exact answers with a structural floor, and engine adapters. npm publish is next.

How it works

your repo ──scan (gitignore-aware)──> tree-sitter parse ──> SQLite index (symbols, imports,
                                                             occurrences, call/type edges, FTS5)
                                                                   │
Claude Code ◄──────────── MCP tools over stdio ────────────────────┘

• Persistent index at <repo>/.code-atlas/index.db (self-gitignored), incrementally refreshed by content hash.
• Live — a gitignore-aware file watcher reindexes saves within a debounce beat and re-resolves only the affected files (--no-watch or "watch": false to disable).
• Zero config — point it at a repo root and it works. Optional code-atlas.json for include/exclude tweaks.
• Everything local — your code never leaves your machine.

Install & use with Claude Code

claude mcp add code-atlas -- npx -y @lusiem/code-atlas serve

Or from a clone:

git clone https://github.com/lusiem/code-atlas && cd code-atlas
npm install && npm run build
claude mcp add code-atlas -- node /path/to/code-atlas/dist/index.js serve

The server indexes the current working directory; pass --root <path> to override.

CLI

node dist/index.js index [--root <path>]              # one-shot index build (debugging / warm-up)
node dist/index.js serve [--root <path>] [--no-watch] [--no-lsp] [--no-embeddings] [--no-download]
                                                      # MCP server on stdio

Tools

Full reference with example outputs: docs/tools.md.

Cross-file answers are LSP-first with a structural floor: when a language server is available (found on PATH or auto-acquired into a per-user cache), references/definitions/hover/call hierarchies are exact and tagged lsp; everywhere else, heuristic import/name resolution answers with a confidence score per edge. Servers: typescript-language-server + pyright (npm), gopls (go install), rust-analyzer + clangd (pinned, SHA-256-verified release binaries), Eclipse JDT LS for Java (needs a Java 21+ runtime — detected via PATH/JAVA_HOME), kotlin-language-server (needs any JRE), and csharp-ls for C# (needs the .NET SDK; installed as a dotnet tool — deliberately not Microsoft's Roslyn LSP, whose license is VS-only). GDScript attaches to the Godot editor's built-in language server (TCP 127.0.0.1:6005, override with CODE_ATLAS_GODOT_LSP_PORT) whenever the editor has the project open — close the editor and answers fall back to structural, reopen it and the next query reattaches. Missing runtimes degrade that language to structural, reported honestly in index_status. A first-time acquisition (download + boot) never blocks a query: tools wait up to 8 s, then answer structurally while the server finishes starting. Disable with --no-lsp; disable auto-download with --no-download.

Semantic search embeds every function/class (signature + doc + body) with a code-tuned local model — jinaai/jina-embeddings-v2-base-code, quantized ONNX — and fuses cosine similarity with BM25 keyword rank. Everything stays on your machine. The ONNX runtime (~220 MB) and model (~150 MB) are not part of this package: they download to the per-user cache the first time you call semantic_search, never at install, and structural tools never wait on them. Until coverage completes, results are keyword-weighted and say so. Embedding a 60k-symbol repo takes ~15 minutes of background time, once; after that only edited symbols re-embed. "embeddings": {"model": "fast"} swaps in a 4× faster general-purpose model; --no-embeddings turns the layer off.

Languages

Indexing today: TypeScript, TSX, JavaScript, Python, C, C++, Rust, Go, Java, Kotlin, C#, GDScript.

Game engines: engine assets index alongside code — Godot .tscn/.tres scenes (node trees, script attachments, signal connections, autoloads; res:// resolved per project.godot, monorepos of many projects included), Unity .unity/.prefab/.asset + .meta GUID maps (MonoBehaviour → C# class links, serialized references), and Unreal .uproject/.uplugin/Build.cs module graphs plus indexed reflection macros: UCLASS/USTRUCT/UFUNCTION/UPROPERTY specifiers attach to the symbol they annotate (searchable, shown in get_symbol_info), and dllexport macros (class MYGAME_API AMyActor) no longer break C++ class extraction. Binary formats (.uasset, Blueprints, .scn) are out of scope by design.

Roadmap

1. Structural core: scanner, SQLite+FTS5 index, TS/JS/Python extractors, first 6 tools ✅
2. All 11 language extractors, cross-file import resolution, call graph (find_references, call_hierarchy, trace_path) ✅
3. File watcher + incremental reindexing (scoped re-resolution, schema migrations) ✅
4. LSP layer (auto-acquired ts-ls/pyright/gopls; checksum-pinned rust-analyzer/clangd binaries; JDT LS/kotlin-language-server/csharp-ls with JRE/.NET detection; precise references/definitions/hover/call hierarchy with graceful fallback) ✅
5. Local-embedding semantic search (semantic_search, hybrid BM25+vector reciprocal-rank fusion, lazy model download, incremental re-embedding) ✅
6. Game-engine adapters: GDScript grammar (vendored wasm build), Godot scenes/autoloads, Unity prefabs/GUIDs, Unreal module graph + reflection search, Godot editor LSP attach (TCP 6005, nightly-tested against a real editor) ✅
7. Docs, benchmarks in CI (cold index 157k LOC ≈ 5 s, warm queries p95 < 10 ms), cross-platform CI, npm pack smoke ✅ — npm publish + MCP registry submission pending

Performance (vuejs/core, 157k LOC, 525 files): cold index 4.7 s, warm tool calls p95 ≤ 6 ms through a full MCP round-trip. scripts/bench.mjs runs in CI.

Development

npm install        # also copies grammar wasm files into grammars/
npm test           # vitest: extractor golden tests, store, scanner, MCP end-to-end
npm run lint
npm run dev serve  # run from source via tsx

Position convention: lines are 1-based, columns 0-based, paths root-relative with forward slashes. See CONTRIBUTING.md for how to add languages, servers, and grammars.

License

MIT