fix(hydration): suppress React #418 errors from Nextra internals (SHA-2240)#209
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…-2240)
Three targeted fixes for latent React hydration mismatches that became
visible after the PostHog error handler was added (2026-05-04):
1. Add suppressHydrationWarning to <body> — guards against next-themes
writing data-theme to the body before React finishes reconciling;
without this, ThemeProvider's localStorage read produces a body-level
#418 on every cold page load.
2. Remove i18n prop from Layout — docs has a single locale (en). Passing
i18n caused the Nextra Switchers component to render LocaleSwitch in
the footer whenever hideSidebar=true (page-type routes), producing an
"HTML vs text" structural difference between SSR and client trees.
3. Filter React hydration errors in PostHog IGNORED_PATTERNS — the errors
predate the PostHog change; the new window.addEventListener('error')
handler just made them visible. Patterns: "Hydration failed",
"There was an error while hydrating", "Text content did not match".
Co-Authored-By: Paperclip <noreply@paperclip.ing>
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Summary
suppressHydrationWarningto<body>— guards againstnext-themeswritingdata-themefromlocalStoragebefore React reconciles; without this, ThemeProvider causes a body-level #418 on every cold page loadi18nprop fromLayout— docs has a single locale (en); the prop caused Nextra'sSwitcherscomponent to mountLocaleSwitchin the footer on page-type routes, producing an "HTML vs text" structural mismatch between SSR and client trees (confirmed absent from built output via$L1cmount reference check)IGNORED_PATTERNSwith React hydration error strings — defense-in-depth; the structural fixes are the real solution, but filtering prevents false-positive error tracking while residual instances fade post-deployBackground
A PostHog handler change deployed 2026-05-04 surfaced latent React #418 hydration errors (26+ in a partial day). The errors predate the handler change; the new
window.addEventListener('error')handler just made them visible.QA
LocaleSwitchmount reference (\$L1c) absent from renderedout/en/pricing.html→ i18n removal effective<body suppressHydrationWarning>andIGNORED_PATTERNSupdates verified in sourceCloses SHA-2240
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