From 2526c29286eb7ac14b88ab1d9fc810729c2630a2 Mon Sep 17 00:00:00 2001
From: GiHoon1123 <rlaejrqo465@naver.com>
Date: Wed, 30 Sep 2026 16:58:30 +0900
Subject: [PATCH] quic: retain readers for readable streams

Create readers when readable QuicStream instances are constructed so data received before the first async iterator pull survives native stream cleanup. Add a regression test for a peer-initiated unidirectional stream that sends data and FIN before the reader is pulled.

Assisted-by: Codex
Signed-off-by: GiHoon1123 <rlaejrqo465@naver.com>
---
 lib/internal/quic/quic.js                     |  6 +++
 .../test-quic-stream-uni-delayed-reader.mjs   | 47 +++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 test/parallel/test-quic-stream-uni-delayed-reader.mjs

diff --git a/lib/internal/quic/quic.js b/lib/internal/quic/quic.js
index 4922ce562751..88a85c7428c7 100644
--- a/lib/internal/quic/quic.js
+++ b/lib/internal/quic/quic.js
@@ -1659,6 +1659,12 @@ class QuicStream {
     this.#handle = handle;
     handle[kOwner] = this;
     const inner = this.#inner;
+    // Keep a reader alive for readable streams before the native handle can
+    // be destroyed. A peer may send data and FIN before the consumer asks
+    // for its async iterator.
+    if (!isLocal || direction === kStreamDirectionBidirectional) {
+      inner.reader = handle.getReader();
+    }
     inner.session = session;
     inner.direction = direction;
     inner.isLocal = isLocal;
diff --git a/test/parallel/test-quic-stream-uni-delayed-reader.mjs b/test/parallel/test-quic-stream-uni-delayed-reader.mjs
new file mode 100644
index 000000000000..45a233617161
--- /dev/null
+++ b/test/parallel/test-quic-stream-uni-delayed-reader.mjs
@@ -0,0 +1,47 @@
+// Flags: --experimental-quic --experimental-stream-iter --no-warnings
+
+// Test: data received before the async iterator is pulled remains readable
+// after a peer-initiated unidirectional stream closes.
+
+import { hasQuic, skip, mustCall } from '../common/index.mjs';
+import assert from 'node:assert';
+
+if (!hasQuic) {
+  skip('QUIC is not enabled');
+}
+
+const { listen, connect } = await import('../common/quic.mjs');
+const { bytes } = await import('stream/iter');
+
+const encoder = new TextEncoder();
+const expected = encoder.encode('data before the first pull');
+const done = Promise.withResolvers();
+
+const serverEndpoint = await listen(mustCall(async (serverSession) => {
+  await serverSession.opened;
+  const stream = await serverSession.createUnidirectionalStream({
+    body: expected,
+  });
+  await stream.closed;
+  serverSession.close();
+}));
+
+const clientSession = await connect(serverEndpoint.address);
+await clientSession.opened;
+
+clientSession.onstream = mustCall(async (stream) => {
+  const iterator = stream[Symbol.asyncIterator]();
+
+  // Delay the first pull until after the peer has sent FIN and the native
+  // stream handle has been closed.
+  await stream.closed;
+
+  const received = await bytes(iterator);
+  assert.deepStrictEqual(received, expected);
+  clientSession.close();
+  done.resolve();
+});
+
+await done.promise;
+await clientSession.closed;
+await serverEndpoint.close();