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, change-impact analysis with affected-test detection, web-framework route maps (Express/NestJS/Fastify/FastAPI/Flask/Django), Mermaid diagrams, precise LSP-backed answers, local-embedding semantic search, and game-engine asset understanding (Godot, Unity, Unreal). 25 languages indexed.

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: released (npm @lusiem/code-atlas, MCP registry io.github.lusiem/code-atlas). 25 languages, 29 tools, LSP-exact answers with a structural floor, engine adapters, and an agent-workflow layer (context_pack, verify_changes) built for token economy.

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.

Tool	What it answers
project_overview	What is this project? Languages, sizes, index freshness. Call first.
search_symbols	Where is X defined? FTS + fuzzy over names and doc comments, filterable by kind/language/path.
semantic_search	"Where is retry backoff implemented?" — natural-language search, hybrid keyword+embedding ranking, fully local.
get_file_outline	What's in this file? Hierarchical signatures without reading source.
get_symbol_info	Everything about one symbol (by id, position, or name) incl. docs and source.
context_pack	One-call, token-budgeted briefing on a symbol: source, outline, callers/callees, types, route, related tests — instead of six lookups. Sections that don't fit the budget are named.
batch_symbols	Up to 50 #ids resolved to compact one-liners in a single call.
ast_query	Raw tree-sitter S-expression queries — structural search regex can't do.
find_references	Who uses this symbol? Exact (LSP) when available, else resolved usages first, name-matches as candidates.
go_to_definition	Definition of the identifier at a position. LSP-exact with index fallback.
call_hierarchy	Who calls this / what does it call, as a tree. [lsp 1.00] edges when a language server is running.
type_hierarchy	Supertypes and subtypes over extends/implements edges.
get_dependencies	File import graph, both directions (imports / imported-by).
trace_path	Shortest call chain between two symbols.
change_impact	Blast radius of a change: transitive callers + import reachability, affected test files first. Target a symbol, a file list, or nothing — no args analyzes the uncommitted git diff (hunk-level: only symbols you actually touched seed the traversal). Affected route handlers are tagged [ROUTE GET /users/:id].
verify_changes	Post-edit structural check against git HEAD: imports that stopped resolving, removed exports other files still reference, signature changes with live callers. change_impact predicts; this confirms.
tests_for_symbol	Which tests exercise this symbol? Reverse graph walk to test files, naming the test case; import-chain-only hits reported as a weaker signal.
find_similar_code	"Does a helper for this already exist?" — near-duplicate search over the local embedding vectors, with a text-similarity fallback while coverage builds.
find_dead_code	Zero-reference symbols after entry-point/route/lifecycle exclusions, confidence-hedged (possibly dead when a same-name usage exists anywhere); unused exports listed separately.
hotspots	Churn × size risk ranking from one git log --numstat pass.
list_routes	Web-framework routes across the workspace — Express, Fastify, NestJS, FastAPI, Flask, Django, plus file-based routing for Next.js, SvelteKit, Nuxt, and Remix — each linked to its handler symbol.
find_route	"Which code serves GET /api/users/7?" — matches a concrete URL against indexed route patterns (:id, {id}, <int:pk> are wildcards) and returns the handler.
generate_diagram	Mermaid diagrams of the above graphs: import graph (file or directory level), call graph around a symbol, type hierarchy, call path — paste straight into GitHub markdown or docs.
get_scene_structure	Godot scene node tree with attached scripts, instanced sub-scenes, and signal connections (handlers resolved to symbols).
find_asset_references	Which scenes/prefabs use this script? Reverse lookup across Godot res:// paths, Unity GUIDs (via .meta), and Unreal modules.
search_reflection	All UPROPERTY(Replicated), [SerializeField], @export vars, signals — engine reflection markers across the workspace.
index_status / reindex	Index health and manual refresh.

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 (25): TypeScript, TSX, JavaScript, Python, C, C++, Rust, Go, Java, Kotlin, C#, GDScript, PHP, Ruby, Lua, Solidity, Zig, Nix, Swift, Scala, Dart, Terraform/HCL, Pascal/Delphi, Vue, Svelte.

Vue and Svelte single-file components index the <script> blocks (all of them, <script setup> included) at their true file line numbers; component imports resolve, so .vue/.svelte dependency graphs work in get_dependencies and change_impact. Terraform maps blocks to symbols (resource "aws_s3_bucket" "logs" is searchable by either label) and resolves local module sources as imports. Languages beyond the LSP-covered core answer structurally with confidence-scored edges — same contract as everywhere else.

Test-file awareness: every indexed file is classified by per-language path conventions (*.test.ts, test_*.py, *_test.go, src/test/, *_spec.rb, foundry .t.sol, …) — this powers change_impact's affected-test reporting. Inline test blocks (Rust #[cfg(test)], Zig test) are not path-classifiable and stay invisible by design.

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
8. Competitive push: change_impact (blast radius + affected tests, git-diff mode), web-framework route indexing (list_routes/find_route), 13 more languages incl. Vue/Svelte SFCs ✅
9. Agent-workflow release (0.4.0): context_pack (token-budgeted one-call briefings), verify_changes (post-edit check vs git HEAD), tests_for_symbol, find_similar_code, find_dead_code + hotspots, batch_symbols, max_tokens on every list-shaped tool, file-based routing (Next.js/SvelteKit/Nuxt/Remix), PHP PSR-4 / C# namespace / Swift SPM import resolution, opt-in LSP edge promotion, sqlite-vec vec0 KNN ✅

Performance (vuejs/core, 157k LOC, 536 files incl. .vue SFCs): cold index 3.8 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