From 1938a8db4efca2a2d45f3f5658a23b0033d631af Mon Sep 17 00:00:00 2001
From: edwloef <edwin.frank.loeffler@gmail.com>
Date: Sun, 9 Aug 2026 08:58:31 +0200
Subject: [PATCH] don't allocate empty streams in `Task::batch`

---
 runtime/src/task.rs | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/runtime/src/task.rs b/runtime/src/task.rs
index 5575bcf26b..bb7008556b 100644
--- a/runtime/src/task.rs
+++ b/runtime/src/task.rs
@@ -96,11 +96,14 @@ impl<T> Task<T> {
     where
         T: 'static,
     {
+        let mut last_stream = None;
         let mut select_all = stream::SelectAll::new();
         let mut units = 0;
 
         for task in tasks.into_iter() {
-            if let Some(stream) = task.stream {
+            if let Some(stream) = task.stream
+                && let Some(stream) = last_stream.replace(stream)
+            {
                 select_all.push(stream);
             }
 
@@ -108,7 +111,12 @@ impl<T> Task<T> {
         }
 
         Self {
-            stream: Some(boxed_stream(select_all)),
+            stream: if select_all.is_empty() {
+                last_stream
+            } else {
+                select_all.extend(last_stream);
+                Some(boxed_stream(select_all))
+            },
             units,
         }
     }