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Custom Not Found Handler

By default, Zuplo will return a 404 (using problem details) if no matching path/method combination is found. You can override this behavior by adding code to the zuplo.runtime.ts file (see runtime extensions).

For example - a custom not found handler can be used to return a 405 - Method Not Allowed if a matching path is found, but no matching METHOD, here is an example function that would implement this behavior:

export function runtimeInit(runtime: RuntimeExtensions) {
//add a custom not found handler
runtime.notFoundHandler = async (request, context, notFoundOptions) => {
if (notFoundOptions.routesMatchedByPathOnly.length > 0) {
// It is required to have an 'Allow' header with a 405 response
// Generate a string of allowed methods
const allowedMethods = notFoundOptions.routesMatchedByPathOnly
.map((route) => route.methods)
.reduce((acc, val) => acc.concat(val), [])
.join(", ");

return HttpProblems.methodNotAllowed(
{ allow: allowedMethods }

return HttpProblems.notFound(request, context);


An error in your zuplo.runtime.ts can break your gateway for all requests. Be sure to carefully review any custom code in this file and add generous error handling where appropriate.