streams: push() marks a Readable disturbed (isDisturbed/readableDidRead true before any read) — undici body.text() rejects 'unusable' #11212

In Perry, a producer-side push() marks a Readable as disturbed. stream.isDisturbed(r) and r.readableDidRead become true as soon as data is pushed. In Node both stay false until a consumer reads (read(), 'data', pipe, async iteration).

This is the next undici blocker (#11046), after #11197 (PR #11207). With #11194, #11198 and #11207 applied, the real undici 8.9.0 fixture's request() now resolves for GET, POST and 404. Every response.body.text() / .json() then rejects with TypeError: unusable. undici's consume() checks isUnusable(body) → util.isDisturbed(body) → stream.isDisturbed(body). Perry reports the body as disturbed because undici's onData has already push()ed the response chunk into it, so the body is treated as already consumed.

Repro (no packages)

import { Readable, isDisturbed } from "node:stream";
class Body extends Readable {
  constructor() { super({ autoDestroy: true, read() {}, highWaterMark: 64 * 1024 }); }
}
const b: any = new Body();
console.log("fresh:", isDisturbed(b), b.readableDidRead);
b.push(Buffer.from("hello"));
console.log("after push:", isDisturbed(b), b.readableDidRead);
const p: any = new Readable({ read() {} });
p.push("x");
console.log("plain after push:", isDisturbed(p), p.readableDidRead);

Node 26.5.1:

fresh: false false
after push: false false
plain after push: false false

Perry (main 8708312 + #11207, perry-dev, Linux x64, PERRY_NO_AUTO_OPTIMIZE=1):

fresh: false false
after push: true true
plain after push: true true

Where

crates/perry-runtime/src/node_stream.rs append_readable_output_chunk (and unshift_chunk) call mark_disturbed(stream) for every pushed chunk. In Node, kIsDisturbed / readableDidRead are set on the consumer side: in Readable.prototype.read and in 'data' emission.

undici fixture result for reference: undici 8.9.0, a local Node 26.5.1 HTTP server, auto-optimize ON, PERRY_WORKSPACE_ROOT set.

undici 8.9.0
GET: ERROR TypeError: unusable
POST: ERROR TypeError: unusable
404: ERROR TypeError: unusable

Node gives GET: status=200 body=hello-get / POST: status=200 json={"got":"ping"} / 404: status=404 body=not-found.