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Impact analysis example

What breaks when you change React Router (packages/react-router)?

Real arc impact output on React Router (packages/react-router) — same structure as the homepage demo. Know blast radius before you merge.

Project: React Router (packages/react-router) · Score: 72.9/100 (Moderate technical debt) · 69 modules · 289 edges

Engineering decision simulation

Validation procedure 01 · merge vs. hold before output

Before arc impact

You plan a change to a high fan-in module in React Router (packages/react-router). Would you merge without knowing blast radius?

Typical answer: hold — need dependency context.

After arc impact

Structured output below: score, hotspots, corridors, and high-risk modules — same field schema as the homepage proof.

Decision: confirm hold, narrow change, or inspect paths first.

Published as part of the validation record. Run locally: arc impact <file-you-are-changing>

Architectural Risk Map

Where risk accumulates by control surface — drill down Surface → Substrate → Mechanism → Evidence.

See control surfaces →

Dependency evidence

Architecture visualization

Diagrams are generated from ArcSight analysis data. Dependency graph and risk map show key modules; subsystem view shows high-level structure.

Dependency graph
Dependency graph for this codebase
Subsystem architecture
Subsystem architecture for this codebase
Risk map
Risk map for this codebase

Architecture score & metrics

Score: 72.9/100 · Stability: 17/100 · Status: moderate_risk · Confidence: 100%

  • Dependency cycles: 49
  • Layer violations: 2
  • Duplicate authorities: 22

Modules to inspect

One row per module. Fan-in is direct dependents. Blast radius is downstream modules reachable from that file.

Fan-in, direct dependents
  • lib/router/utils35 dependents
  • lib/router/router24 dependents
  • lib/router/history20 dependents
  • lib/dom/ssr/routeModules17 dependents
  • lib/dom/ssr/entry16 dependents
  • lib/dom/ssr/routes11 dependents
  • lib/types/utils7 dependents
Blast radius, downstream modules
  • lib/router/history45 modules
  • lib/router/utils44 modules
  • lib/router/router43 modules
  • lib/dom/ssr/routeModules43 modules
  • lib/dom/ssr/entry43 modules
  • lib/dom/ssr/routes43 modules
ModuleFan-inBlastRisk
lib/router/history2045MEDIUM
lib/router/utils3544HIGH
lib/router/router2443MEDIUM
lib/dom/ssr/routeModules1743MEDIUM
lib/dom/ssr/entry1643CRITICAL
lib/dom/ssr/routes1143CRITICAL
lib/types/utils7MEDIUM

Architectural gravity centers

  • lib/router/history— concentrates too many responsibilities
  • lib/router/history— shared utility hub
  • lib/router/utils— concentrates too many responsibilities
  • lib/router/utils— shared utility hub
  • lib/router/utils— crosses a layer boundary

CLI workflow

Scan → Fix → Finish → Watch. Nothing else required.

  • arc scanFind issues
  • arc fixApply fixes
  • arc finishResolve remaining
  • arc watchKeep clean

More commands (explain, impact, guard…) →

Key takeaways

  • •Structural scan reports dependency cycles — inspect impact paths before refactors that cross module boundaries.
  • •High fan-in modules are change-risk zones; run arc explain <path> before refactoring.
  • •Run the full workflow (analyze, hotspots, explain, impact, snapshot, drift) in your repo for deterministic architecture insights.

Run ArcSight on your repo

Install the CLI and run analyze, then hotspots and explain for the same workflow.

npm install -g arcsight
arc analyze
Install ArcSight →

This case study is generated from ArcSight analysis data. View short analysis. View all analyses