{"record":{"id":"ea7fb30939f4aec3","repo":"withastro/astro","slug":"failed-to-prerender-request-url-prerendererr","errorCode":null,"errorMessage":"Failed to prerender ${request.url}: ${prerenderError}","messagePattern":"Failed to prerender (.+?): (.+?)","errorType":"exception","errorClass":"Error","httpStatus":null,"severity":"error","filePath":"packages/integrations/cloudflare/src/prerenderer.ts","lineNumber":278,"sourceCode":"\t\t\t\turl: request.url,\n\t\t\t\trouteData: serializeRouteData(routeData, trailingSlash),\n\t\t\t\tincremental,\n\t\t\t};\n\n\t\t\tconst response = await fetch(`${serverUrl}${PRERENDER_ENDPOINT}`, {\n\t\t\t\tmethod: 'POST',\n\t\t\t\theaders: { 'Content-Type': 'application/json' },\n\t\t\t\tbody: JSON.stringify(body),\n\t\t\t\tredirect: 'manual',\n\t\t\t});\n\n\t\t\t// Check for prerender errors surfaced by the workerd handler via header\n\t\t\t// (the response body may be stripped by the Vite preview server).\n\t\t\t// Only the header marks a failure: pages may intentionally return\n\t\t\t// non-2xx responses while prerendering (e.g. a custom 404 page).\n\t\t\tconst prerenderError = response.headers.get('x-astro-prerender-error');\n\t\t\tif (prerenderError) {\n\t\t\t\tthrow new Error(`Failed to prerender ${request.url}: ${prerenderError}`);\n\t\t\t}\n\n\t\t\t// Incremental builds receive a `PrerenderEnvelope` wrapping the response\n\t\t\t// alongside the metadata collected in workerd, since a raw response\n\t\t\t// cannot carry it. Reconstruct the response and return it paired with\n\t\t\t// the metadata for the build to record.\n\t\t\tif (incremental) {\n\t\t\t\tconst envelope: PrerenderEnvelope = await response.json();\n\t\t\t\tconst reconstructed = new Response(Buffer.from(envelope.body, 'base64'), {\n\t\t\t\t\tstatus: envelope.status,\n\t\t\t\t\tstatusText: envelope.statusText,\n\t\t\t\t\theaders: envelope.headers,\n\t\t\t\t});\n\t\t\t\treturn { response: reconstructed, metadata: envelope.metadata };\n\t\t\t}\n\n\t\t\treturn response;\n\t\t},","sourceCodeStart":260,"sourceCodeEnd":296,"githubUrl":"https://github.com/withastro/astro/blob/d081033d5fe8e8a68c4bbbad4af9d2deb9c74bca/packages/integrations/cloudflare/src/prerenderer.ts#L260-L296","documentation":"Thrown by the Cloudflare prerenderer when the workerd handler reports a per-page prerender failure via the `x-astro-prerender-error` response header. Because pages may legitimately return non-2xx bodies (e.g. a custom 404), only this header marks an actual failure. The error message is the header value, prefixed with the failing URL.","triggerScenarios":"During build, rendering a specific route throws inside workerd; the handler catches it and surfaces the message through the `x-astro-prerender-error` header. The prerenderer detects the header and throws `Failed to prerender <url>: <message>`.","commonSituations":"A page references an undefined variable, a missing component, or a runtime API unavailable in workerd. A data fetch inside the page fails (e.g. a bound service is unreachable). Type errors that only manifest at runtime under workerd.","solutions":["Read the prerender error message after the colon — it is the original throw from the page.","Open the failing route in `astro dev` (with the adapter) to get the full stack trace and HMR diagnostics.","Fix the page-level error (undefined reference, missing import, failed fetch) and rebuild.","If the error is binding-related, verify the binding exists and is wired for local prerender."],"exampleFix":"// before — page throws on undefined\nexport const GET = ({ params }) => new Response(params.missing.id);\n\n// after\nexport const GET = ({ params }) => new Response(params.id);","handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"try {\n  await build();\n} catch (e) {\n  if (/Failed to prerender/.test(e.message)) {\n    const url = e.message.match(/prerender (\\S+):/)?.[1];\n    // open `url` in astro dev to reproduce with full stack trace\n  }\n  throw e;\n}","preventionTips":["Render every route in astro dev with the adapter before building.","Keep page code defensive: null-check params, locals, and bindings.","Use the failing URL from the error to localize the bug quickly."],"tags":["cloudflare","prerender","workerd","build","ssr"],"backgroundTag":null,"analyzedSha":"d081033d5fe8e8a68c4bbbad4af9d2deb9c74bca","analyzedAt":"2026-08-12T13:37:29.035Z","schemaVersion":2},"datasetVersion":"2026-08-12T18:17:37.767Z"}