Biome 2.5.5

I've been running Biome 2.5.5 through its paces since it dropped today, and honestly — this is the kind of patch release that makes you appreciate a well-maintained tool. No breaking changes, no new major features to learn, just a solid stack of fixes that address real-world pain points.

Verdict at the top: update now. It's a drop-in replacement for 2.5.4, and the fix volume alone justifies the five seconds it takes to bump your dependency.

What Got Fixed

The changelog clocks in at around 20 items, which is substantial for a patch release. Here are the fixes that actually bit me (or would have, given time):

• useExhaustiveSwitchCases and bigint literals — The rule now correctly handles binary, octal, and hex bigint literals. If you write switch (val) { case 1n: ... }, it now flags the missing 2n case. This was a genuine gap.
• CSS formatter fixes — Multiple patches landed for CSS formatting: comments between values and !important are now placed correctly, selector combinator comments are preserved on the right side, and syntax-owned names get lowercased while author-defined names are kept as-is. The diff samples in the changelog show exact before/after — they're subtle but correct.
• HTML/Vue parser panic fixed — The argument-less v-bind shorthand (:=\"props\") no longer crashes the parser. Vue users, you can breathe again.
• check --write now reports code frames — If you use Biome's formatter via CLI, the check --write command finally shows the formatted code frame when the formatter is enabled. This was a confusing UX gap that's now closed.
• LSP daemon fix — Closing one editor no longer kills the shared Biome daemon used by other editors. If you run multiple editor windows with Biome, this was a silent headache that's now gone.

New Rule: noNegationInEqualityCheck

There's one new lint rule: noNegationInEqualityCheck. It flags expressions like !foo === bar — which due to operator precedence evaluates as (!foo) === bar, almost certainly a mistake for foo !== bar. It includes an unsafe fix that flips the operator. Small addition, but it catches a real class of bugs.

Performance Win

The noThenProperty rule got a ~50% performance improvement. If you have this rule enabled in a large codebase, you'll notice the difference in lint times.

Should You Upgrade?

Yes. This is a low-risk patch with a high density of real fixes. No config changes needed, no breaking changes, no new dependencies. Run npm update @biomejs/biome and move on with your day.