From afbc45bf32fe8146183d0d44fc16213cdebddbdb Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Thu, 19 Feb 2026 20:35:42 -0600
Subject: [PATCH] [e131] Drain all queued packets per loop iteration (#14133)

---
 esphome/components/e131/e131.cpp | 26 +++++---------------------
 esphome/components/e131/e131.h   |  9 +++++++++
 2 files changed, 14 insertions(+), 21 deletions(-)

diff --git a/esphome/components/e131/e131.cpp b/esphome/components/e131/e131.cpp
index 941927122c..a7a695c167 100644
--- a/esphome/components/e131/e131.cpp
+++ b/esphome/components/e131/e131.cpp
@@ -70,27 +70,12 @@ void E131Component::loop() {
   E131Packet packet;
   int universe = 0;
   uint8_t buf[1460];
+  ssize_t len;
 
-#if defined(USE_SOCKET_IMPL_BSD_SOCKETS) || defined(USE_SOCKET_IMPL_LWIP_SOCKETS)
-  ssize_t len = this->socket_->read(buf, sizeof(buf));
-  if (len == -1) {
-    return;
-  }
-
-  if (!this->packet_(buf, (size_t) len, universe, packet)) {
-    ESP_LOGV(TAG, "Invalid packet received of size %d.", (int) len);
-    return;
-  }
-
-  if (!this->process_(universe, packet)) {
-    ESP_LOGV(TAG, "Ignored packet for %d universe of size %d.", universe, packet.count);
-  }
-#elif defined(USE_SOCKET_IMPL_LWIP_TCP)
-  while (auto packet_size = this->udp_.parsePacket()) {
-    auto len = this->udp_.read(buf, sizeof(buf));
-    if (len <= 0)
-      continue;
-
+  // Drain all queued packets so multi-universe frames are applied
+  // atomically before the light writes. Without this, each universe
+  // packet would trigger a separate full-strip write causing tearing.
+  while ((len = this->read_(buf, sizeof(buf))) > 0) {
     if (!this->packet_(buf, (size_t) len, universe, packet)) {
       ESP_LOGV(TAG, "Invalid packet received of size %d.", (int) len);
       continue;
@@ -100,7 +85,6 @@ void E131Component::loop() {
       ESP_LOGV(TAG, "Ignored packet for %d universe of size %d.", universe, packet.count);
     }
   }
-#endif
 }
 
 void E131Component::add_effect(E131AddressableLightEffect *light_effect) {
diff --git a/esphome/components/e131/e131.h b/esphome/components/e131/e131.h
index fee447b678..8f0b808946 100644
--- a/esphome/components/e131/e131.h
+++ b/esphome/components/e131/e131.h
@@ -46,6 +46,15 @@ class E131Component : public esphome::Component {
   void set_method(E131ListenMethod listen_method) { this->listen_method_ = listen_method; }
 
  protected:
+  inline ssize_t read_(uint8_t *buf, size_t len) {
+#if defined(USE_SOCKET_IMPL_BSD_SOCKETS) || defined(USE_SOCKET_IMPL_LWIP_SOCKETS)
+    return this->socket_->read(buf, len);
+#elif defined(USE_SOCKET_IMPL_LWIP_TCP)
+    if (!this->udp_.parsePacket())
+      return -1;
+    return this->udp_.read(buf, len);
+#endif
+  }
   bool packet_(const uint8_t *data, size_t len, int &universe, E131Packet &packet);
   bool process_(int universe, const E131Packet &packet);
   bool join_igmp_groups_();