From 39723424ece85b0a143f9053fa142ad0d4c4e85c Mon Sep 17 00:00:00 2001
From: Kadir Can Ozden <101993364+bysiber@users.noreply.github.com>
Date: Fri, 20 Feb 2026 09:26:31 +0300
Subject: [PATCH] Fix error message: says stdout but checks stdin

The ValueError raised when stdin=subprocess.PIPE is used without
nursery.start incorrectly says 'stdout=subprocess.PIPE'.  This is
confusing for users since the actual problem is with the stdin
argument, not stdout.
---
 src/trio/_subprocess.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/trio/_subprocess.py b/src/trio/_subprocess.py
index 145c2de9b..d73ba3dc2 100644
--- a/src/trio/_subprocess.py
+++ b/src/trio/_subprocess.py
@@ -675,7 +675,7 @@ async def my_deliver_cancel(process):
     if task_status is trio.TASK_STATUS_IGNORED:
         if stdin is subprocess.PIPE:
             raise ValueError(
-                "stdout=subprocess.PIPE is only valid with nursery.start, "
+                "stdin=subprocess.PIPE is only valid with nursery.start, "
                 "since that's the only way to access the pipe; use nursery.start "
                 "or pass the data you want to write directly",
             )