diff --git a/app/Models/Foundation/Summit/Events/SummitEvent.php b/app/Models/Foundation/Summit/Events/SummitEvent.php
index 9b2921437..5f40f83f3 100644
--- a/app/Models/Foundation/Summit/Events/SummitEvent.php
+++ b/app/Models/Foundation/Summit/Events/SummitEvent.php
@@ -1426,7 +1426,6 @@ public function getStreamDuration(): int
     public function setStreamingUrl(?string $streaming_url): void
     {
         $this->streaming_url = $streaming_url;
-        $this->overflow_streaming_url = $streaming_url;;
         $key = $this->getSecureStreamCacheKey();
         $this->skipDateUpdate();
         if (Cache::tags(sprintf('secure_streams_%s', $this->summit->getId()))->has($key))
@@ -1994,8 +1993,6 @@ public function setOverflow(string $overflow_streaming_url,
     {
         $this->overflow_streaming_url = $overflow_streaming_url;
         $this->overflow_stream_is_secure = $overflow_stream_is_secure;
-        $this->streaming_url = $overflow_streaming_url;
-        $this->stream_is_secure = $overflow_stream_is_secure;
         $this->occupancy = self::OccupancyOverflow;
         $this->skipDateUpdate();
     }
diff --git a/tests/Unit/Entities/SummitEventStreamingUrlTest.php b/tests/Unit/Entities/SummitEventStreamingUrlTest.php
new file mode 100644
index 000000000..ee73acfcd
--- /dev/null
+++ b/tests/Unit/Entities/SummitEventStreamingUrlTest.php
@@ -0,0 +1,66 @@
+<?php
+
+namespace Tests\Unit\Entities;
+
+/**
+ * Copyright 2026 OpenStack Foundation
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+use models\summit\SummitEvent;
+use Tests\TestCase;
+
+/**
+ * The primary stream and the overflow stream are two independent URLs on an event.
+ * Setting one must never overwrite the other: the overflow readers (the public ?k= door,
+ * occupancy/overflow) read overflow_streaming_url only, and the primary readers read
+ * streaming_url only.
+ */
+final class SummitEventStreamingUrlTest extends TestCase
+{
+    private const PrimaryUrl = 'https://stream.mux.com/primary123.m3u8';
+    private const OverflowUrl = 'https://stream.mux.com/overflow456.m3u8';
+
+    private function eventWithSummit(): SummitEvent
+    {
+        $summit = TestUtils::mockSummit();
+        $event  = new SummitEvent();
+        $summit->addEvent($event);
+        return $event;
+    }
+
+    public function testSetOverflowLeavesThePrimaryStreamUntouched(): void
+    {
+        $event = $this->eventWithSummit();
+        $event->setStreamingUrl(self::PrimaryUrl);
+        $event->setStreamIsSecure(false);
+
+        $event->setOverflow(self::OverflowUrl, true);
+
+        $this->assertEquals(self::OverflowUrl, $event->getOverflowStreamingUrl());
+        $this->assertTrue($event->getOverflowStreamIsSecure());
+        $this->assertEquals(SummitEvent::OccupancyOverflow, $event->getOccupancy());
+
+        $this->assertEquals(self::PrimaryUrl, $event->getStreamingUrl(), 'setOverflow must not overwrite streaming_url');
+        $this->assertFalse($event->IsSecureStream(), 'setOverflow must not overwrite stream_is_secure');
+    }
+
+    public function testSetStreamingUrlLeavesTheOverflowStreamUntouched(): void
+    {
+        $event = $this->eventWithSummit();
+        $event->setOverflow(self::OverflowUrl, true);
+
+        $event->setStreamingUrl(self::PrimaryUrl);
+
+        $this->assertEquals(self::PrimaryUrl, $event->getStreamingUrl());
+        $this->assertEquals(self::OverflowUrl, $event->getOverflowStreamingUrl(), 'setStreamingUrl must not overwrite overflow_streaming_url');
+    }
+}