From 937715c91c35ee9b4e35c05f7fd0f93cb2209544 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 10 Feb 2026 07:09:21 -0600
Subject: [PATCH] [api] Split process_batch_ to reduce stack on single-message
 hot path

Clamp buffer pre-allocation to MAX_BATCH_PACKET_SIZE.
---
 esphome/components/api/api_connection.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/esphome/components/api/api_connection.cpp b/esphome/components/api/api_connection.cpp
index 0881128b74..136c61e3cf 100644
--- a/esphome/components/api/api_connection.cpp
+++ b/esphome/components/api/api_connection.cpp
@@ -1923,6 +1923,10 @@ void APIConnection::process_batch_() {
   for (size_t i = 0; i < num_items; i++) {
     total_estimated_size += this->deferred_batch_[i].estimated_size;
   }
+  // Clamp to MAX_BATCH_PACKET_SIZE — we won't send more than that per batch
+  if (total_estimated_size > MAX_BATCH_PACKET_SIZE) {
+    total_estimated_size = MAX_BATCH_PACKET_SIZE;
+  }
 
   this->prepare_first_message_buffer(shared_buf, header_padding, total_estimated_size);