Make Next.js ESLint rule honor custom pageExtensions

Many Next.js teams—especially those using MDX, content-as-code workflows, or nonstandard file types in monorepos—are still bitten by the core ESLint "pages" rule not honoring custom pageExtensions, which causes pages to be silently ignored by linters and CI and drives false negatives in quality and security checks. This is a practical problem for engineering teams that must enforce shift-left quality, run strict CI gates, and expect linters to mirror framework behavior; with an addressable market of roughly 30M web developers and a $4.5B developer tools spend (≈$150/yr per developer), the downstream pain is measurable when pages go unlinted in production builds. You could build an open-source ESLint plugin and companion CLI that reads Next.js configuration (next.config.js / next.config.mjs / next.config.ts), honors custom pageExtensions, understands MDX and app-dir semantics, and provides deterministic page discovery for ESLint and CI. Ship it with a tight VS Code extension, a robust test matrix for monorepos and TypeScript setups, and an enterprise option (hosted CI lint runners, SLA support, upgrade compatibility guarantees) to monetize—this aligns with the stated revenue potential of the idea (78/100) and leverages low direct competition. The timing is favorable: framework consolidation toward Next.js, rising adoption of MDX/content-as-code, and a broader shift-left quality emphasis increase demand for framework-aware tooling, matching the market score of 92/100. The main challenges are upkeep—Next.js internals change frequently—and edge-case handling across diverse project setups, so the differentiator will be engineering rigor: deterministic correctness, fast compatibility updates, high test coverage, clear UX documentation, and partnerships or endorsements from the Next.js ecosystem rather than marketing alone.