Biome shipped two coordinated releases on June 12, 2026: Biome CLI v2.5.0 and @biomejs/js-api v6.0.0. The headline is the JavaScript API's first major version bump since the project split the WASM packages from the CLI. The CLI bump is mostly a WASM sync, with a long list of small features on top.
The js-api v6.0.0 headline
The major bump is centered on a single new export: spanInBytesToSpanInCodeUnits(diagnostic.location.span, content). Biome's diagnostics carry UTF-8 byte offsets because that is how the analyzer indexes source internally. JavaScript strings are UTF-16, so any code that took a Biome diagnostic and called content.slice(spanStart, spanEnd) on the original string would get the wrong text on any non-ASCII content: emoji, accented characters, CJK. The slice boundary would land in the middle of a code unit, return undefined for the trailing surrogate, and silently corrupt the extracted snippet.
The new helper converts byte-based spans to UTF-16 code unit spans, including the surrogate pair and unpaired surrogate edge cases. It is the kind of fix that warrants a major version bump on its own, and Biome used the opportunity to version-bump the WASM packages: @biomejs/wasm-web, @biomejs/wasm-bundler, and @biomejs/wasm-nodejs all pin to 2.5.0 to match the CLI.
SCSS, JSON, linter, and CLI
The 2.5.0 release covers a long list of incremental features. On the parser side, SCSS support is meaningfully expanded: qualified names in values and function calls, unary expression parsing, nested declarations in declaration lists, declarations in @page blocks, and delimiters in bracketed value lists. JSON gets a new useSortedPackageJson rule. The linter picks up two new cross-language rules, a new includes option for plugin file scoping, an ignore option for no-unused-variables, and a noUndeclaredClasses change that now collects both local and global styles. organizeImports adds a sortBareImports option.
The CLI gets an ANSI art Biome logo on startup and a new concise reporter. biome_service gains support for applying GritQL plugin rewrites through the standard --write flag, which is the missing piece for shipping a custom refactor rule that runs through the same pipeline as the linter and formatter.
The HTML analyzer continues to grow. As of 2.5, it includes noRedundantRoles, useKeyWithMouseEvents, and useAriaActivedescendantWithTabindex (the noRedundantRoles port was reverted and re-landed after a follow-up fix, which is why the changelog shows it twice).
Why the major bump matters
For users consuming Biome as a CLI or through editor integrations, 2.5.0 is a routine upgrade. The interesting story is for projects that embed @biomejs/js-api directly: the helper is the first piece of a wider effort to make the API safe to use on non-ASCII source code, and the major version bump signals that the project is treating the public surface as a stable contract.
That positioning puts Biome closer to where Oxc sits with the Rust toolchain: a Rust-backed JavaScript toolchain with a programmatic API for embedding. The two projects take different positions on the spectrum (Biome bundles a linter, formatter, and import organizer in one binary, while Oxc splits those into separate crates), but both are now mature enough that programmatic embedding is a first-class use case. For teams that ran the previous API through a UTF-8-to-UTF-16 conversion workaround, 6.0.0 is the upgrade that makes the workaround unnecessary.
