# mui/base-ui · RepoSense Release & Migration Intelligence

> Export `CssVariables` and `DataAttributes` types (#5243) b. Drop-in upgrade. Migration: None.

## Metadata
- **Repository URL**: https://github.com/mui/base-ui
- **Primary Package**: `@base-ui-components/react` (NPM)
- **Categories**: `STYLING`, `UI_PRIMITIVES`
- **Latest Version**: `v1.9.0`
- **Semantic Status**: `COMPATIBLE`
- **Bundle Size Impact (unavailable)**: `Size Unavailable`
- **Atom Ingestion Feed**: https://github.com/mui/base-ui/releases.atom

## The Human Context (Plain-English Pitch)
@base-ui-components/react is an open-source library and developer tool in the mui/base-ui ecosystem. It saves developers from writing repetitive low-level boilerplate from scratch by providing a battle-tested, open-source implementation ready for production.

## Stage 1 Executive Summary ([Core Change] + [Required Action] + [Migration Effort])
Export `CssVariables` and `DataAttributes` types (#5243) b. Drop-in upgrade. Migration: None.

## Breaking Changes & Required Actions
- Export `CssVariables` and `DataAttributes` types (#5243) by @superhooman
- Fix stale focused field state (#5345) by @atomiks
- Fix animation waits retaining detached elements (#5719) by @flaviendelangle
- Keep item registration in sync when items change under Strict Mode (#5862) by @atomiks

## Migration Snippet
```ts
npm install @base-ui-components/react@1.9.0
```

## Ecosystem Compatibility Matrix & Graph Warnings
- **TypeScript 5.x** [`COMPATIBLE`]: Ships standard TypeScript declaration files without type regressions.

## Zero-Noise Release Timeline
- **v1.9.0** (2026-10-09) [COMPATIBLE]: Export `CssVariables` and `DataAttributes` types (#5243) b. Drop-in upgrade. Migration: None.

## Upgrade & Migration Q&A (GEO Direct Answers)
### Is mui/base-ui v1.9.0 safe to upgrade in production?
mui/base-ui v1.9.0 is classified as COMPATIBLE (MINOR release). Export `CssVariables` and `DataAttributes` types (#5243) b. Drop-in upgrade. Migration: None.

### What breaking changes or compatibility risks exist in mui/base-ui v1.9.0?
No breaking API changes or peer dependency conflicts are recorded for mui/base-ui v1.9.0 in the RepoSense compatibility graph.

### What is the bundle size impact of @base-ui-components/react v1.9.0?
Measured bundle size telemetry is currently unavailable for @base-ui-components/react v1.9.0; verify build output locally before deploying.

### How do I upgrade @base-ui-components/react to v1.9.0?
Upgrade @base-ui-components/react to v1.9.0 by running "npm install @base-ui-components/react@1.9.0" and applying the migration steps: npm install @base-ui-components/react@1.9.0