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
- Open Extensions (
Cmd+Shift+X/Ctrl+Shift+X) - Search Live Cognitive Complexity (or
live-cognitive-complexity) - 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)
- Open this folder in VS Code / Cursor
- Press F5 (Run Extension)
- Open
samples/OrderService.javaorsamples/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/oroperator 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)
| Symbol | Metric |
|---|---|
OrderService (class) |
sum 16, max 14, high 0 |
add |
CC 0 (low) |
validate |
CC 2 (low) |
fulfill |
CC 14 (medium) |
Sample results (samples/order_service.py)
| Symbol | Metric |
|---|---|
OrderService (class) |
sum 16, max 14, high 0 |
add |
CC 0 (low) |
validate |
CC 2 (low) |
fulfill |
CC 14 (medium) |
Configuration
| Setting | Default | Description |
|---|---|---|
liveCognitiveComplexity.enabled |
true |
Master switch |
liveCognitiveComplexity.showCodeLens |
true |
Method CodeLens |
liveCognitiveComplexity.showClassCodeLens |
true |
Class sum / max / high |
liveCognitiveComplexity.showStatusBar |
true |
Cursor method in status bar |
liveCognitiveComplexity.errorThreshold |
15 |
High band + ratio denominator |
liveCognitiveComplexity.warningThreshold |
10 |
Medium absolute lower bound |
liveCognitiveComplexity.mediumRatioPercent |
67 |
Medium ratio lower bound |
liveCognitiveComplexity.excludeAnonymousClassMethods |
true |
Skip anonymous class methods (Java) |
liveCognitiveComplexity.excludeEqualsHashCode |
true |
Skip equals / hashCode (Java) |
liveCognitiveComplexity.excludePatterns |
target, build, __pycache__, .venv, … |
Exclude globs |
Also ensure editor CodeLens is on: "editor.codeLens": true.
Requirements
- VS Code / Cursor
^1.85.0 - Native
tree-sitterbindings (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
- Python
- TypeScript / JavaScript
- Go
- Optional Problems panel diagnostics for high methods
Develop
npm install
npm test
npm run compile
License
MIT