Krater

Krater is a VS Code extension that brings inline change-impact signals into TypeScript and React code.

As you edit, Krater marks symbols whose changes appear to escape the current file, shows a gutter marker when the active edited line contains a high-impact symbol, and adds CodeLens / hover summaries with cached reference and file counts.

For deeper investigation, you can run full impact analysis from the editor context menu and inspect the affected files in Krater's Impact Tree/List.

Why Krater Exists

Large TypeScript and React codebases make it hard to answer a practical question:

If I change this value, what could break?

Traditional reference search is useful, but noisy. Krater adds a bounded semantic layer on top so the editor can point out likely blast radius while you work.

The goal is not exhaustive correctness.

The goal is fast, explainable development signals.

Editor Signals

Krater is designed to stay close to your normal coding flow.

For many edits, you do not need to run a full analysis immediately. The editor signals are meant to help you decide whether a symbol looks safe, suspicious, or worth deeper inspection.

Gutter Marker

A gutter marker appears when the active edited line contains a high-impact symbol.

This is the primary "pay attention here" signal.

CodeLens

CodeLens gives a quick cached impact summary directly above the current line.

Example:

Impact: 4+ refs, 4 files

Hover Details

Hover gives more detail without leaving the editor.

It shows cached reference and file counts, and includes a command link to run full Krater analysis.

Underlines

Krater underlines symbols whose impact appears to escape the current file.

• Dotted underline: symbol appears to affect more than the current file.
• Wavy underline: symbol crosses Krater's current high-impact threshold.

Counts may include a + when Krater stopped because a configured limit was reached.

Full Impact Analysis

When you need a deeper answer, run Krater: Estimate Impact from the command palette or editor right-click menu.

The full analysis shows affected files and reference locations in the Krater activity view.

Quick Start

1. Open a .ts or .tsx file.
2. Edit normally and watch for editor signals:
   • gutter markers
   • underlines
   • CodeLens
   • hover summaries
3. Place the cursor on a symbol when you want a focused impact hint.
4. Run Krater: Estimate Impact when deeper investigation is needed.
5. Review impacted files in the Krater side panel.

What It Does

• Scans the active TypeScript/TSX file in the background.
• Underlines symbols whose impact appears to escape the current file.
• Marks higher-impact symbols with a stronger decoration.
• Shows a gutter marker when the active edited line contains a high-impact symbol.
• Shows hover details with reference and file counts.
• Shows cache-backed CodeLens impact hints for the current cursor line.
• Runs explicit impact analysis from the editor context menu or command palette.
• Shows impacted files in the Krater activity view:
  • Impact Tree
  • Impact List
• Reuses cached impact results across scans, decorations, hover, and CodeLens where possible.

Current Semantic Model

Krater is intentionally bounded. It prefers a small, explainable result over an exhaustive graph.

Current analysis is centered on:

• TypeScript and TSX files
• VS Code definition and reference providers
• Assignment-style propagation
• TSX guards that avoid noisy JSX attribute expansion
• Per-run limits for depth, references, files, and time

Krater does not currently perform full static data-flow analysis. Return-flow propagation and richer graph explanation are still on the roadmap.

Settings

• krater.maxDepth

  • maximum propagation depth for a full impact search

• krater.maxHits

  • maximum total reference hits to collect

• krater.maxFiles

  • maximum number of files to touch

• krater.maxSeconds

  • time limit for a full user-triggered search

• krater.ignoreFolders

  • folder names to exclude when computing impact

Current Status

Krater 0.0.5 is a developer-preview release.

It includes:

• explicit impact analysis
• active-file scanning
• gutter markers
• hover summaries
• CodeLens hints
• shared impact caching
• background editor signals

Still planned:

• stronger cache identity using TypeScript symbols
• lower reference-provider pressure
• return-flow propagation
• richer propagation graph visualization
• structured output for future AI/tool integrations

Non-Goals

Krater does not:

• execute code
• understand runtime values
• replace the TypeScript compiler
• guarantee complete dependency analysis
• support non-TypeScript languages

It is a developer-experience tool for estimating change impact, not a verifier.