vercel/next.js · error

Route ${workStore.route} used `headers()` inside a function

Error message

Route ${workStore.route} used `headers()` inside a function cached with `unstable_cache()`. Accessing Dynamic data sources inside a cache scope is not supported. If you need this data inside a cached function use `headers()` outside of the cached function and pass the required dynamic data in as an argument. See more info here: https://nextjs.org/docs/app/api-reference/functions/unstable_cache

What it means

Error "Route ${workStore.route} used `headers()` inside a function cached with `unstable_cache()`. Accessing Dynamic data sources inside a cache scope is not supported. If you need this data inside a cached function use `headers()` outside of the cached function and pass the required dynamic data in as an argument. See more info here: https://nextjs.org/docs/app/api-reference/functions/unstable_cache" thrown in vercel/next.js.

Source

Thrown at packages/next/src/server/request/headers.ts:70

      // When using forceStatic we override all other logic and always just return an empty
      // headers object without tracking
      const underlyingHeaders = HeadersAdapter.seal(new Headers({}))
      return makeUntrackedHeaders(underlyingHeaders)
    }

    if (workUnitStore) {
      switch (workUnitStore.type) {
        case 'cache': {
          const error = new Error(
            `Route ${workStore.route} used \`headers()\` inside "use cache". Accessing Dynamic data sources inside a cache scope is not supported. If you need this data inside a cached function use \`headers()\` outside of the cached function and pass the required dynamic data in as an argument. See more info here: https://nextjs.org/docs/messages/next-request-in-use-cache`
          )
          Error.captureStackTrace(error, headers)
          applyOwnerStack(error)
          workStore.invalidDynamicUsageError ??= error
          throw error
        }
        case 'unstable-cache':
          throw new Error(
            `Route ${workStore.route} used \`headers()\` inside a function cached with \`unstable_cache()\`. Accessing Dynamic data sources inside a cache scope is not supported. If you need this data inside a cached function use \`headers()\` outside of the cached function and pass the required dynamic data in as an argument. See more info here: https://nextjs.org/docs/app/api-reference/functions/unstable_cache`
          )
        case 'generate-static-params':
          throw new Error(
            `Route ${workStore.route} used \`headers()\` inside \`generateStaticParams\`. This is not supported because \`generateStaticParams\` runs at build time without an HTTP request. Read more: https://nextjs.org/docs/messages/next-dynamic-api-wrong-context`
          )
        case 'prerender':
        case 'prerender-client':
        case 'validation-client':
        case 'private-cache':
        case 'prerender-runtime':
        case 'prerender-legacy':
        case 'request':
          break
        default:
          workUnitStore satisfies never
      }
    }

View on GitHub (pinned to 0eb3775416)

Solutions

1. Call headers() outside the unstable_cache function and pass the values in as arguments.

When it happens

Trigger: headers() is called inside an unstable_cache function.

Common situations: Accessing headers inside a cached function; read them outside and pass as arguments.

AI-assisted analysis of vercel/next.js@0eb3775416 (2026-08-19). Data as JSON: /api/errors/2a1c1d7fd1b0259d. Report an issue: GitHub.