console.log(ctx) / util.inspect(ctx.res) throws 'Cannot read private member #headersList' on Node (guarded stub headers) #1000

console.log(ctx) in a handler, and util.inspect(ctx.res) or util.inspect(ctx.res.headers), throw on Node:

TypeError: Cannot read private member #headersList from an object whose class did not declare it

It happens in every scope, not only a cached one. On workerd there is no throw, because its Headers has no Node inspect hook.

Cause

The #713 response-header guard shadows the stub response's headers with a Proxy whose target is a fresh, empty new Headers(). Its get trap forwards to the real rawStubHeaders (packages/rangojs-router/src/server/request-context.ts:1199-1211 on bad36a6b). Node's util.inspect unwraps the Proxy and runs undici's Headers inspect hook. That hook reads #headersList from a receiver that is not a real Headers, and throws.

Repro

This mirrors the guard shape without any router code (Node 22.18):

import { inspect } from "node:util";
const raw = new Response(null).headers;
const guarded = new Proxy(new Headers(), {
  get(_t, prop) {
    const v = Reflect.get(raw, prop);
    return typeof v === "function" ? v.bind(raw) : v;
  },
});
inspect(guarded); // TypeError: Cannot read private member #headersList ...

Through the router: in any handler, console.log(ctx) or console.log(ctx.res) on the Node dev server.

Suggested fix

Give the guarded proxy an own [Symbol.for("nodejs.util.inspect.custom")] that inspects rawStubHeaders. Alternatively, have the trap handle that symbol. #976 / #999 takes the same approach for ctx.request. Add a unit test that inspects ctx, ctx.res and ctx.res.headers.