# I built an AI agent that migrates Next.js Pages Router to App Router > Source: > Published: 2026-05-25 14:36:24+00:00 Most Next.js teams have a Pages Router → App Router migration sitting in their backlog. It's mechanical but careful work, and it keeps getting deprioritized. I built [migrate-bot](https://migrate-bot.dev) to automate it end-to-end, and this post is about how it works under the hood. App Router isn't just "move files to a new folder". The semantic changes: `getStaticProps` / `getServerSideProps` → `async` Server Components`getStaticPaths` → `generateStaticParams` `next/router` → `next/navigation` (`useRouter` / `usePathname` / `useSearchParams` )`next/head` → the Metadata API (`export const metadata` )`pages/_app.tsx` + `pages/_document.tsx` → `app/layout.tsx` `pages/api/x.ts` (single handler) → `app/api/x/route.ts` (`export async function GET/POST/...` )`pages/` → `app/` restructure, including `[slug]` dynamic routesThe whole thing runs serverless + ephemeral: ``` queued → analyzing → planning → migrating → verifying → pr_ready ↓ (on failure) aborted_blocker → refunding → refunded ``` Each transition is persisted to D1 so every job is observable, and a mid-pipeline crash transitions to `aborted_blocker` → automatic refund rather than leaving the customer charged for nothing. Early on, every repo with a `pages/_document.tsx` failed. The planner maps both `_app.tsx` and `_document.tsx` to the same target (`app/layout.tsx` ), and my migrate step recorded the second one as a "failed task" when it detected the target was already written. The pipeline treated any failed task as fatal — so the whole migration aborted. The fix was to distinguish *intentional skips* (planned target collisions) from *real failures* (the LLM aborting or erroring). I added a `skippedTaskIds` field separate from `failedTaskIds` , and surfaced the skip in the PR description so the customer knows to manually merge any custom `` attributes from their `_document.tsx` . Since this rewrites real production code, the trust mechanisms matter: `next build` ) can't pass for reasons attributable to the service.It's live at [migrate-bot.dev](https://migrate-bot.dev). Pricing is per-repo by file count ($99 / $249 / $499). I'd genuinely value feedback on the approach — especially the pricing shape and the draft-PR + refund trust model. (Currently not offered to EEA/UK/Switzerland residents due to GDPR territorial scope; revisiting post-launch.)