What ArcSight found in Next.js

Real arc impact on Next.js (packages/next) — blast radius, break paths, and evidence. Same question as the homepage: what breaks if I change this?

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Project: Next.js (packages/next)Score: 89/100 (A)1,942 modules4,489 edges

arc impact src/shared/lib/app-router-types

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Proof summary

Four questions every public repository page must answer — see validation record · Change Impact problem · High Fan-In problem · Blast Radius problem.

What ArcSight found

High-risk module src/shared/lib/app-router-types (fan-in 45) — CRITICAL. src/types: fan-in 21, blast radius 423 modules. src/types — shared utility hub. 1,942 modules and 4,489 dependency edges traced.

Why it matters

In Next.js (packages/next), Change-risk signal at src/shared/lib/app-router-types (fan-in 45) — merge impact can travel beyond the diff you see. Blast radius on src/types reaches 423 downstream modules. ArcSight answers “what breaks if I change this?” before you ship; high fan-in is a change-risk signal, not a verdict on design quality.

What we'd inspect first

src/shared/lib/app-router-types
src/server/lib/lru-cache
src/shared/lib/segment

What evidence supports it

Local CLI analysis — repository source stays on your machine
Structural coverage: 1,942 modules, 4,489 edges in this snapshot
Reproducible fields match homepage live demo and frozen proof output

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 for this codebase — Dependency graph

Subsystem architecture for this codebase — Subsystem architecture

Architecture score & metrics

Score: 89/100

Critical findings

src/shared/lib/app-router-typesCRITICALfan-in: 45
src/server/lib/lru-cacheHIGHfan-in: 12
src/shared/lib/segmentHIGHfan-in: 23

Hotspots

src/typesCRITICALfan-in: 21blast: 423
src/server/config-sharedCRITICALfan-in: 46blast: 423

Dependency corridors

Repeated paths where changes propagate through the same modules.

src/server/config-shared → src/server/request-meta → src/server/request/params
src/types → src/shared/lib/utils → src/server/app-render

Subsystem overview

next-next-devtools(120 modules)
client-app-call-server(85 modules)

Architectural gravity centers

src/types— shared utility hub
src/server/config-shared— central orchestrator

CLI workflow

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

arc scanFind issues
arc fixApply fixes
arc finishResolve remaining
arc watchKeep clean (Pro)

More commands (explain, impact, guard…) →

Key takeaways

•Architecture score 89/100 indicates a healthy structure with room to reduce cycles and violations.
•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 locally, then run arc impact on the file you plan to change — before merge.

npm install -g arcsight

arc impact <path>

Install →

Embed this report

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Explore

Change Impact problemHigh Fan-In problemBlast Radius problem

Evidence-backed analysis snapshot. Validation record · Install · Homepage demo