Live Cognitive Complexity

Real-time Sonar-style cognitive complexity in VS Code and Cursor.

See complexity as you type, above every method and class — with color-coded low / medium / high bands, ratio %, and absolute scores.

Language support today: Java, Python, TypeScript, JavaScript (Node.js & NestJS)
Planned: Go, C#, C++, and more

Install from VS Code Marketplace · GitHub

Features

• Method CodeLens — e.g. $(warning) medium complexity (93%) · CC: 14 $(chevron-right)
• Class CodeLens — e.g. $(check) class complexity · sum 16 · max 14 · high 0
• Click to expand — clicking a method CodeLens shows a lens above every contributing line, e.g. +2 for loop (nesting 2); click again to collapse
• Status bar — complexity for the method under your cursor
• Codicon markers on the CodeLens (absolute + ratio of Sonar threshold; worst wins)
  • $(check) — low
  • $(warning) — medium
  • $(error) — high
• Tooltip breakdown — every increment with line, nesting, and reason
• Works on large files (hundreds of KB)

Install

VS Code / Cursor Marketplace

1. Open Extensions (Cmd+Shift+X / Ctrl+Shift+X)
2. Search Live Cognitive Complexity (or live-cognitive-complexity)
3. Click Install

Or open: marketplace.visualstudio.com/items?itemName=yousuf360.live-cognitive-complexity

From a VSIX

git clone https://github.com/yousuf360/live-cognitive-complexity.git
cd live-cognitive-complexity
npm install
npm run compile
npx @vscode/vsce package

Then in VS Code / Cursor:

Cmd+Shift+P → Extensions: Install from VSIX... → pick live-cognitive-complexity-*.vsix

Cursor tip: Do not use the Agent CLI cursor --install-extension — that binary is not the IDE. Use Install from VSIX in the Command Palette.

Development host (F5)

1. Open this folder in VS Code / Cursor
2. Press F5 (Run Extension)
3. Open samples/OrderService.java or samples/order_service.py

What it measures

Cognitive Complexity (Sonar) estimates how hard control flow is to understand:

• if / else / elif / else if, loops, switch / match, catch / except, ternary
• Nesting penalties
• && / || / and / or operator sequences
• Lambdas / nested functions increase nesting for nested code
• List/dict/set comprehensions and generator expressions are ignored (readable shorthand)

Unlike cyclomatic complexity, it ignores “readable shorthand” and focuses on mental load.

Defaults match Sonar rule S3776 (errorThreshold = 15).

Sample results (samples/OrderService.java)

Sample results (samples/order_service.py)

Configuration

Also ensure editor CodeLens is on: "editor.codeLens": true.

Requirements

• VS Code / Cursor ^1.85.0
• Native tree-sitter bindings (bundled in the VSIX). If load fails after a platform change: npm rebuild tree-sitter tree-sitter-java tree-sitter-python

Privacy

Analysis runs entirely on your machine. Source is not uploaded. No telemetry.

Roadmap

• [x] Python
• [ ] TypeScript / JavaScript
• [ ] Go
• [ ] Optional Problems panel diagnostics for high methods

Develop

npm install
npm test
npm run compile

License

MIT