Next.js Sitemap Not Updating? Here's the Real Fix

Short summary

A detailed debugging guide for a Next.js sitemap cache-coherence bug where revalidateTag invalidates inner data cache but leaves the outer route handler's statically rendered XML untouched. The fix is a single line—export const revalidate = 3600—forcing the sitemap route to re-render on a bounded interval. The article also explains a broader principle: revalidateTag clears data, not the route that renders it, so any stacked cache requires either route-level revalidate or revalidatePath.

• •Sitemap staleness caused by dual-layer caching: unstable_cache invalidated but route handler output remains frozen
• •Fix: add export const revalidate = 3600 to sitemap.ts for route-level ISR
• •Broader rule: revalidateTag clears data, not the route; always set route-level revalidate or call revalidatePath

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