# Biome @biomejs/biome@2.5.15 — Release & Upgrade Intelligence
- **Product:** Biome (https://biomejs.dev)
- **Version:** @biomejs/biome@2.5.15
- **Released:** Sep 30, 2026
- **Impact Score:** 5/10
- **Breaking Changes:** Not verified
- **Canonical Analysis:** https://changelogs.us/biome/updates/biomejs-biome-2.5.15/

## Executive Summary (TL;DR)
Biome @biomejs/biome@2.5.15. Source highlight: Added the new nursery rule `noReactObjectTypeAsDefaultProp`, which disallows array, object, and function values as default props in React components.

## New Features
- feat(codegen): lower generic type constraints
- feat(codegen): lower Symbol static members
- feat(codegen): lower Symbol call signatures
- feat(md): suppressions support
- feat(linter): add noReactObjectTypeAsDefaultProp rule
- feat(codegen): lower array type syntax

## Improvements
- perf(analyze): optimize useIndexOf callback traversal
- perf(noBeforeInteractiveScriptOutsideDocument): avoid hitting the filesystem, before easier checks
- perf(type inference): replace promise classification HashSet with Brent cycle detection by @codspeed[bot] in https://github.com/biomejs/biome/pull/12011
- perf(type_inference): index namespace members once per module
- perf: read semantic binding ranges without resolving syntax nodes
- perf(type_inference): memoize callable signature resolution

## Bug Fixes
- Added the new nursery rule `noReactObjectTypeAsDefaultProp`, which disallows array, object, and function values as default props in React components.
- Added the nursery rule `noSvelteExportLet`, which disallows declaring Svelte component props with the legacy `export let` syntax. Use the `$props()` rune instead.
- Added a new nursery rule `useLogicalProperties` that enforces the use of logical properties in CSS, promoting better internationalization and accessibility practices. The rule supports a `direction` option with `"ltr"` as the default and `"rtl"` as the alternative.
- Added the nursery rule `useSvelteKitRuneImports`, which reports imports from the deprecated `$app/stores` module and suggests `$app/state` instead.
- Fixed #11656: `noAstroSetHtmlDirective` now correctly reports `set:html` directives inside Astro template expressions.
- Improved the performance of the HTML formatter up to 4x.

## Upgrade Command
```bash
npm install --save-dev --save-exact @biomejs/biome@2.5.15
```