From a246afa33a424d831b6f5c59fac7f07aebdf4a03 Mon Sep 17 00:00:00 2001
From: Tianyi Cui <53024+tianyicui@users.noreply.github.com>
Date: Sun, 19 Jul 2026 14:14:00 +0800
Subject: [PATCH] test(acp-snapshot): detach the inherited-stdio fixture

Windows does not guarantee that an ordinary child process will continue after its parent exits. The fake ACP agent exited immediately after spawning its late-output descendant, so Windows could tear down that descendant and close the protocol stream before the delayed ACP update was written.

Launch the descendant in detached mode while continuing to inherit stdout and stderr, then unref it as before. This preserves the intended regression boundary: launcher shutdown must wait for descendant-held stdio and parse the final buffered frame after the direct ACP parent exits.
---
 packages/support/acp-snapshot/tests/fixtures/fake-acp-agent.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/packages/support/acp-snapshot/tests/fixtures/fake-acp-agent.ts b/packages/support/acp-snapshot/tests/fixtures/fake-acp-agent.ts
index fbac6dfa10..c5a5810068 100644
--- a/packages/support/acp-snapshot/tests/fixtures/fake-acp-agent.ts
+++ b/packages/support/acp-snapshot/tests/fixtures/fake-acp-agent.ts
@@ -267,6 +267,7 @@ function flushLogsAndExit(): void {
       `setTimeout(() => process.stderr.write(${JSON.stringify('late inherited stderr\n')}), 75)`,
     ].join(';')
     spawn(process.execPath, ['-e', code], {
+      detached: true,
       stdio: ['ignore', 'inherit', 'inherit'],
     }).unref()
   }