Vanilla JS to React Migration

My current front-end is a sizeable vanilla-JavaScript codebase—roughly 1.5 million characters spread across more than 3 million total characters of markup, style sheets, and helper scripts. I need the whole thing transitioned to a clean, component-based React 18 structure with zero functional regressions.

Scope
• Every existing screen, widget, and interaction must be reproduced exactly in React.
• Any third-party scripts or in-house utilities that overlap with React’s ecosystem should be replaced with React-friendly equivalents; nothing legacy should linger unless it has no React counterpart.
• No new features are required at this stage: a faithful migration only.
• I’m flexible on how you handle state—built-in hooks, Context, Redux, or another proven approach—as long as the final result is predictable, testable, and easy to extend.

Acceptance criteria
1. Side-by-side comparison shows identical behaviour, styling, and performance in modern browsers.
2. All existing unit or integration tests keep passing; new tests cover any fresh React logic.
3. Build scripts, linting, and CI pipelines are updated so the React project installs and runs with a single command.
4. Final delivery includes well-organised source code, documentation of key architectural decisions, and a migration summary highlighting any unavoidable deviations.

If you have tackled large-scale vanilla-to-React migrations before and can guarantee a bug-free cut-over, this job is ready for you.