BackLens

BackLens helps you explore codebases as a semantic call graph inside VS Code and on the web.

Install the extension: BackLens on VS Code Marketplace

What is BackLens?

BackLens is a static code intelligence platform for backend-oriented codebases.

It analyzes source code, builds a call graph, stores it in SQLite, and lets you explore architecture through:

• a standalone web app
• a VS Code extension webview

Why should you care?

BackLens helps you:

• understand unfamiliar backend code faster
• trace call chains between functions, methods, and classes
• inspect architectural hotspots
• jump from graph nodes directly to source

Why use it?

BackLens helps you quickly answer practical architecture questions:

• What calls this function or method?
• What does this class depend on?
• Which nodes are hotspots?
• How do I jump from graph node to source?

It is designed for understanding unfamiliar repositories and reducing time spent tracing call flows manually.

Features

• JS/TS parser with object-aware extraction (functions, classes, methods, calls)
• Graph-store query engine with transitive traversals, hotspots, and path queries
• Core REST API for graph operations
• Interactive 3-panel web UI (search, hotspots, inspector, expansion)
• VS Code extension with project registry, analysis pipeline, graph view, and source navigation

Demo / Screenshots

Current UI snapshots:

Hotspots and Method Expansion	Class Hierarchy and Inspector
Framework Call Graph View	Go-to-Source Navigation (GIF)

Supported Languages / Scope

Current strongest support:

• TypeScript
• JavaScript
• TSX / JSX parsing support

Current focus:

• backend-oriented JS/TS repositories

BackLens does not currently claim first-class analysis support for Python, Go, or Rust.

See docs/limitations.md for details and caveats.

How to use (VS Code extension)

1. Open your project folder in VS Code.
2. Run BackLens: Analyze Folder.
3. Open BackLens: Show Graph.
4. Search nodes, expand callers/callees, and inspect node details.
5. Use go-to-source actions to jump from graph nodes to code.

Commands

• BackLens: Analyze Folder (backlens.analyzeFolder)
• BackLens: Re-analyze Folder (backlens.reanalyzeFolder)
• BackLens: Show Graph (backlens.showGraph)
• BackLens: Refresh (backlens.refreshExplorer)
• BackLens: Close Project (backlens.closeProject)
• BackLens: Go to Source (backlens.goToNode)

Quick Start

Fastest path to first result:

1. Install dependencies:
   • pnpm install
2. Run API:
   • pnpm --filter @backlens/core-api dev
3. Run web UI:
   • pnpm --filter @backlens/web dev
4. Open browser:
   • http://localhost:5173

Or use VS Code extension mode:

1. Build extension assets:
   • pnpm --filter backlens compile
2. Launch Extension Host from VS Code
3. Run BackLens: Analyze Folder
4. Open BackLens: Show Graph

How It Works

High-level flow:

1. Parser builds IR from source files
2. Graph-store transforms IR into nodes and edges
3. Graph is saved to SQLite (native or WASM adapter)
4. Data is queried by core-api or extension message bus
5. UI renders and explores graph interactively

Detailed architecture:

• docs/architecture-overview.md

Monorepo Structure

Top-level packages:

• packages/parser
• packages/graph-store
• packages/core-api
• web
• vscode-extension

Detailed structure and entry points:

• docs/project-structure.md

Current Status

BackLens is usable today for JS/TS call graph exploration with both standalone and extension workflows.

Production hardening is still in progress in areas like tests, docs depth, and broader language coverage.

Known Limitations

BackLens performs static analysis and has expected limits.

Current limitations include:

• JS/TS ecosystems are best supported in the current version.
• Dynamic runtime patterns may not fully resolve.
• Framework magic may appear as external or unresolved in some repositories.

See:

• docs/limitations.md
• docs/troubleshooting.md

Roadmap

Near-term priorities:

• deeper automated tests across parser, graph-store, API, and UI
• reliability and performance improvements on larger repositories
• contract consistency checks between UI, API, RPC, and graph-store

See also:

• docs/contracts/graph-query-contract.md

Contributing

Contributions are welcome.

Start here:

• CONTRIBUTING.md
• docs/getting-started.md
• docs/installation.md
• docs/usage-guide.md
• docs/project-structure.md

License

BackLens is open source under the GNU Affero General Public License v3.0 only (AGPL-3.0-only).

• Full license text: LICENSE
• Project notices: NOTICE
• Trademark and branding policy: TRADEMARK.md

Note: The BackLens name, logo, and branding are not freely reusable for confusing commercial clones or implied-endorsement uses.