ESLint 10.9.0
ESLint 10.9.0 rolled out on August 21, 2026, and the linting crowd is once again split between "finally, that's fixed" and "wait, is the autofix actually safe now?" As per usual with point releases, you get a handful of genuine improvements wrapped in a few dozen documentation bumps. Let's not get carried away.
What Actually Changed Here
The headline additions are two new rule behaviors. First, no-loss-of-precision now handles underflow cases it used to skip, meaning numbers that quietly spilled into subnormals will finally get flagged. Second, no-unmodified-loop-condition picks up a checkConditionalExpressions option so conditional expressions that can never change the loop outcome are no longer let off the hook.
The Autofix Question
The fixes are the part to be cautious about. There's a guard preventing an unsafe no-var autofix with hoisted functions, and another that stops no-var from firing when a variable is shadowed by a catch parameter. That last one is the kind of edge case that has bitten real codebases, so it's welcome — but it's also a reminder that "autofix safe" is a sliding scale. Something that was blindly rewritable yesterday now correctly backs off, which means your CI output may look different even if your code doesn't.
The prefer-template fix is the one to watch. An invalid autofix that created a tagged template call has been corrected. If you've ever seen a "fixed" string interpolation turn into nonsense, you know how much of a relief this is — and how much you should re-run your tests after upgrading.
Things to Keep in Mind Before Upgrading
- Two new rule capabilities mean existing configs using these rules may surface new errors on code that previously passed.
- Autofix behavior changed in three places; run your full suite, don't just trust
--fix. - The rest of the release is documentation — useful, but it won't change how your lint output looks.
Bottom line: ESLint 10.9.0 is a solid patch release, not a revolution. Upgrade for the correctness fixes, keep your tests handy, and don't let the "safe autofix" framing lull you into skipping a review pass.