Diagnose and fix slow Next.js App Router navigations with guided instant-tests

Frontend teams running modern React apps with the Next.js App Router routinely encounter slow in-app navigations that degrade user experience and are time-consuming to diagnose. This pain is concentrated among product and frontend engineers, performance teams, and platform squads within an addressable pool of roughly 200,000 frontend engineering teams standardizing on React/Next.js. You could build a developer tool that runs guided instant-tests to reproduce slow navigations locally and in CI, automatically pinpointing root causes—excessive client bundle size, expensive server components, serialization latency, or hydration stalls—and proposing actionable fixes or code diffs. Deep integrations with Playwright, App Router internals, and existing observability (RUM/APM) plus a web UI for drill-downs would let teams triage regressions in minutes instead of days. This market is attractive now because framework consolidation and a shift-left testing trend make framework-specific tooling high-leverage, and navigation snappiness is increasingly treated as a product metric tied to retention. With an estimated $1.2B market (200,000 teams × $6,000 ACV), a market score of 90/100 and revenue potential at 84/100, there is clear willingness to pay for tools that cut time-to-diagnosis and improve user experience. To stand out you must combine deep Next.js App Router expertise with pragmatic, actionable diagnostics—guided instant-tests that are reproducible, CI-friendly, and deliver human-readable remediation. The challenges are tangible: competition is medium, Next.js APIs evolve, and maintaining accurate heuristics across diverse deployments is work-intensive, so early focus on the highest-impact failure modes, strong integrations, and thoughtful developer ergonomics will be essential to demonstrate ROI.