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fix(react): resolve theme toggle hydration mismatch #1103

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fix(react): resolve theme toggle hydration mismatch #1103

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8ea7c65
feat: resolve theme toggle hydration mismatch
puneetnith28 Sep 15, 2026
fcbd764
fix(react): validate stored theme preference on mount
puneetnith28 Sep 16, 2026
e12d85a
refactor: remove redundant key from ThemeToggle
puneetnith28 Sep 16, 2026
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12 changes: 8 additions & 4 deletions packages/react/src/html/ui/hooks/useTheme.mjs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,10 +29,14 @@ const applySystemTheme = () => applyTheme('system');
* @returns {['system'|'light'|'dark', (next: 'system'|'light'|'dark') => void]}
*/
export const useTheme = () => {
// Read stored preference once on mount; default to 'system'.
const [pref, setPref] = useState(() =>
server ? 'system' : (localStorage.getItem('theme') ?? 'system')
);
const [pref, setPref] = useState('system');

useEffect(() => {
const stored = localStorage.getItem('theme');
if (stored === 'light' || stored === 'dark') {
setPref(stored);
}
}, []);
Comment on lines +34 to +39

@TusharThakur04 TusharThakur04 Sep 15, 2026

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Suggested change
useEffect(() => {
const stored = localStorage.getItem('theme');
if (stored) {
setPref(stored);
}
}, []);
useEffect(() => {
const stored = localStorage.getItem('theme');
if (stored === 'light' || stored === 'dark') {
setPref(stored);
}
}, []);

@TusharThakur04 TusharThakur04 Sep 15, 2026

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we dont need to reapply system

@avivkeller avivkeller Sep 15, 2026

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wouldn’t stored !== pref be a little more robust?

@TusharThakur04 TusharThakur04 Sep 15, 2026 •
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if somehow stored is returned as null, its better to check explicitly. WDYT?

@puneetnith28 puneetnith28 Sep 16, 2026

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Updated to explicitly check for 'light' or 'dark' to safely handle null and avoid re-applying system.
Thanks for suggestion !!


// Apply theme on every preference change, and if 'system',
// also listen for OS-level color scheme changes.
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