Test Background and Method
In 2026, terminal AI coding agents have gone mainstream. This piece field-tests three representative tools-Claude Code, Cursor, and Codex CLI-on the same real task, comparing their context understanding, multi-file rewrite capability, and stability.
Test task: In a 12,000-line Next.js repo, migrate legacy Pages Router pages to App Router and fill in strict TypeScript types. Each tool ran independently 3 times; results are averaged.
Core Comparison
| Dimension | Claude Code | Cursor | Codex CLI |
|---|---|---|---|
| Context window | 200K | 128K | 128K |
| Multi-file rewrite | Strong (whole repo) | Strong (Composer) | Medium |
| Terminal-native | Yes | No (GUI) | Yes |
| Pricing | $20/mo or API | $20/mo | Open-source + API |
| Migration success rate | 3/3 | 2/3 | 1/3 |
| Overall score | 4.7 | 4.5 | 4.2 |
Migration success rate = out of 3 independent runs, the count that passed
tsc --noEmitwith no human intervention.
Tested Code Snippet
During migration, Claude Code spontaneously generated a type-guard snippet, while Cursor tended to directly rewrite the component signature:
function isAppRouterProps(props: unknown): props is AppRouterProps {
return typeof props === 'object' && props !== null && 'params' in props
}In strict-typed projects, defensive type guards cut regressions-Claude Code is more solid here.
Selection Advice
- Large-repo refactors / terminal workflows: Pick Claude Code. Whole-repo context + stable tool calls, highest migration success rate.
- Daily editing / low migration cost: Pick Cursor. Smoothest GUI and Tab-completion experience.
- Self-hosted / controllable cost: Pick Codex CLI. Open-source, swappable models, but needs more tuning.
Conclusion
The three aren't substitutes-they're scenario complements. For the core scenario of "structured refactors inside a large existing repo," Claude Code currently has the highest win rate; for "writing new features day-to-day," Cursor feels smoother.