From a6168c11ad291c1e882ebef41727b719a584eb20 Mon Sep 17 00:00:00 2001
From: Rasad Regmi <regmirasad53@gmail.com>
Date: Wed, 16 Sep 2026 21:45:11 +0545
Subject: [PATCH] child_process: emit close after parent disconnect

The 'close' event was not emitted when the parent called subprocess
disconnect() before the channel reached EOF. _disconnect()'s finish()
closed the channel and emitted 'disconnect' but never accounted for the
channel closure with maybeClose(), so _closesGot never reached
_closesNeeded and the 'close' event was lost.

Account for the channel closure in finish() and defer that accounting to
the EOF handler only when _disconnect() was deferred by a pending handle
queue, to avoid double counting.

Fixes: https://github.com/nodejs/node/issues/65646
Signed-off-by: Rasad Regmi <regmirasad53@gmail.com>
---
 lib/internal/child_process.js                 |  9 ++--
 .../test-child-process-disconnect-close.js    | 43 +++++++++++++++++++
 2 files changed, 49 insertions(+), 3 deletions(-)
 create mode 100644 test/parallel/test-child-process-disconnect-close.js

diff --git a/lib/internal/child_process.js b/lib/internal/child_process.js
index 06daf2183db3..88096def5401 100644
--- a/lib/internal/child_process.js
+++ b/lib/internal/child_process.js
@@ -693,9 +693,11 @@ function setupChannel(target, channel, serializationMode) {
       this.buffering = false;
       target.disconnect();
       channel.onread = nop;
-      channel.close();
-      target.channel = null;
-      maybeClose(target);
+      if (target.channel !== null) {
+        channel.close();
+        target.channel = null;
+        maybeClose(target);
+      }
     }
   };
 
@@ -986,6 +988,7 @@ function setupChannel(target, channel, serializationMode) {
 
       channel.close();
       target.emit('disconnect');
+      maybeClose(target);
     }
 
     // If a message is being read, then wait for it to complete.
diff --git a/test/parallel/test-child-process-disconnect-close.js b/test/parallel/test-child-process-disconnect-close.js
new file mode 100644
index 000000000000..9c968983d533
--- /dev/null
+++ b/test/parallel/test-child-process-disconnect-close.js
@@ -0,0 +1,43 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { spawn } = require('child_process');
+
+if (process.argv[2] === 'child') {
+  process.on('disconnect', common.mustCall(() => {
+    process.exit(0);
+  }));
+  process.send('ready');
+} else {
+  const child = spawn(process.execPath, [__filename, 'child'], {
+    stdio: ['ignore', 'pipe', 'pipe', 'ipc'],
+  });
+
+  let closed = false;
+
+  child.on('disconnect', common.mustCall(() => {
+    assert.strictEqual(child.connected, false);
+  }));
+
+  child.on('exit', common.mustCall((code) => {
+    assert.strictEqual(code, 0);
+  }));
+
+  // Regression test for https://github.com/nodejs/node/issues/65646:
+  // the 'close' event must be emitted after the parent calls disconnect()
+  // even though the channel was closed by the parent instead of reaching EOF.
+  child.on('close', common.mustCall((code, signal) => {
+    closed = true;
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  }));
+
+  child.on('message', common.mustCall((msg) => {
+    assert.strictEqual(msg, 'ready');
+    child.disconnect();
+  }));
+
+  process.on('exit', () => {
+    assert.strictEqual(closed, true);
+  });
+}