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# Radix UI -> Base UI migration

You migrate shadcn wrappers, hand-rolled radix compositions, and their consumers to `@base-ui/react`, keeping the project buildable at every step. Be precise; never guess a mapping. When a prop or part is not in these reference files, check `node_modules/@base-ui/react/**/*.d.ts` before transforming, and record gaps in the report.

Preflight (always)

1. `npx shadcn@latest info --json` (or the project's runner): gives the current base, STYLE (e.g. `radix-lyra`), tailwind version, aliases, installed components, and package manager. Trust it over inference. 2. Detect the package manager (packageManager field / lockfile: pnpm-lock.yaml, bun.lock, yarn.lock, package-lock.json) and use IT for every install. Never leave a stale lockfile. 3. Require a clean git tree; work on a branch; one commit per component. 4. Baseline check BEFORE touching dependencies: run the project's typecheck/build so pre-existing failures are never attributed to you. 5. Install `@base-ui/react` alongside radix. Radix packages are removed only after the LAST component is migrated (both coexist fine).

Strategy: golden pair first, transformation engine second

- **Golden pair via the CLI (preferred).** If the project is shadcn with a known style (`radix-<style>`), the shadcn CLI itself is the golden-pair executor: 1. Classify each ui wrapper FIRST: diff the user's file against its stock origin, using the components.json style VERBATIM in the URL (`https://ui.shadcn.com/r/styles/<style>/<component>.json`, files[0].content). This works for prefixed styles (radix-nova) AND legacy unprefixed ones (new-york, new-york-v4, default), which are all still served. 2. WHOLE-PROJECT mode: flip `components.json` style `radix-<style>` -> `base-<style>` now. PROGRESSIVE mode: do NOT flip yet (the project is still mostly radix; the flip happens once, after the last component); fetch base variants directly by URL instead (`https://ui.shadcn.com/r/styles/base-<style>/<component>.json`). 3. PRISTINE wrappers, whole-project mode: `shadcn add <component> --overwrite` delivers the base variant with the project's exact icon/font/preset resolution. Never bulk `--all --overwrite`; go component by component, or you drown in unrelated registry version drift. PROGRESSIVE mode: never use `--overwrite` (it destroys the original that consumers still import); write the fetched base variant content to `<component>-base.tsx` instead. 4. CUSTOMIZED wrappers: fetch the base variant and replay the user's diff onto it (their customizations must SURVIVE; `--overwrite` would destroy them). Mechanical implementation that works at scale: `git merge-file user.tsx radix-golden.tsx base-golden.tsx` (three-way merge, radix golden as ancestor) auto-resolves most files; hand-resolve conflicts with the reference tables. 5. MANDATORY leftover sweep on EVERY golden-pair file, including ones that merged "clean": `grep -n "radix-ui\|@radix-ui\|IconPlaceholder"` per file. The registry sometimes reorders functions between variants, which makes three-way merges report zero conflicts while leaving stale radix hunks in place. A clean merge is NOT proof of a clean file. This is more reliable than reconstructing transforms; use it whenever the pair exists. Consumer/app code has no CLI mechanism: always hand-migrate it against `consumer-props.md`. - **Legacy styles (new-york, new-york-v4, default): classification only, no replay.** These have no base counterpart (there is no base-new-york), and retargeting onto a base-<style> variant would restyle the user's app. Use the radix golden ONLY to detect customizations, then run the transformation engine on the user's OWN file: rewire primitives, keep their exact classes, apply class-mapping renames. Their look stays theirs. At the end of a legacy whole-project migration, FLAG (do not fix): the style name still reads as radix to the CLI, so future `shadcn add` will deliver radix variants; the user decides whether to switch style or add manually. - **Transformation engine (fallback).** Hand-rolled radix code, non-shadcn projects, unknown styles: transform using `universal-patterns.md` (imports in BOTH forms: `radix-ui` and `@radix-ui/react-*`; asChild->render with the worked example; Portal>Positioner>Popup; the positioner FORWARD rule; part renames), the per-family props tables (`overlays.md`, `menus.md`, `form-controls.md`, `disclosure.md`, `display-misc.md`), `class-mapping.md` for data-attribute/CSS-var rewrites, and `wrapper-shapes.md` for exact target shapes (tooltip arrow, SubContent defaults, select anatomy).

Modes

**Progressive (default).** "Migrate accordion" = one component, strangler-fig: 1. Detect in-progress state first: an existing `<component>-base.tsx`, consumers split between old/new imports. The files ARE the state; resume, never restart. 2. If the component imports other ui wrappers still on radix (select -> button), STOP and recommend migrating those first, bottom-up. 3. Write the migrated version to `<component>-base.tsx` (original untouched; golden-pair content fetched by URL, or transformed by hand, per the strategy above); typecheck. Repoint consumers ONE AT A TIME (imports + the call-site props in `consumer-props.md`); typecheck each. When no consumer imports the original: delete it, rename `-base` -> original, flip imports back, final check, commit. When the LAST radix wrapper in the project is finalized, flip `components.json` to `base-<style>` and remove radix deps.

**Whole project** (only when explicitly asked): same per-component work in dependency order (leaf/shared wrappers like button and label first). After wrappers, sweep ALL app code against `consumer-props.md` — the call-site break surface is much larger than asChild. Then remove radix deps, install, full build.

Hard rules

- NEVER touch non-radix libraries or their wrappers: cmdk (command), vaul (drawer), sonner, input-otp, react-day-picker (calendar), recharts (chart). Report them as intentionally untouched. - No Base UI counterpart: AspectRatio -> CSS aspect-ratio div; Label -> native `<label>`; VisuallyHidden -> `sr-only`; Direction -> Direction Provider (`direction` prop, not `dir`). Popover Anchor and NavigationMenu Indicator have no equivalent: inert passthrough + flag. - `button.tsx` migrates to the REAL `@base-ui/react/button` primitive, never a hand-rolled useRender wrapper. - Behavior deltas are FLAGGED, never silently patched (tabs manual activation, menu items not closing on click, nav-menu 50ms delay). The target is idiomatic Base UI matching the shadcn base registry. - Honest reporting: skipped/reverted files are listed as flagged, never as migrated. Pre-existing failures are named as pre-existing.

Verify and report

Typecheck per file, build per batch, full build at the end vs the baseline.

Reports live in a `.migration/` directory at the project root, ONE FILE PER COMPONENT: `.migration/<component>.md` (e.g. `.migration/accordion.md`). Rules: - Each run writes (or fully overwrites) the file for each component it migrated. Re-running a component replaces its report; never touch other components' files. - A multi-component run ("migrate alert-dialog and dropdown-menu") writes one file per component, each self-contained; shared consumer-sweep notes are repeated in every affected file. - Whole-project mode writes the per-component files plus `.migration/project.md` (dependency swap, app-code sweep summary, final build result). - There is NO index file. Migration status is derived from disk, not maintained: scan the project's ui directory (the `ui` alias from shadcn info, e.g. components/ui or src/components/ui) for remaining radix imports when asked "what's left". End every run's summary with that derived count ("N wrappers remain on Radix").

Each `.migration/<component>.md` uses EXACTLY this structure (it is documented publicly; reports must match it):

```md # <component>

<date, strategy used (golden pair via CLI / merge / engine), one-line verdict>

Changed

Left alone

Behavior changes

Verify by hand

<short manual QA checklist for this primitive family: focus return on dialogs, keyboard nav + typeahead on menus/select, tooltip delay feel, slider commit events. Concrete steps, one minute of clicking> ```

Migrate Radix UI to Base UI