From 32fc3ea6f55c32484f600bc56366b49fd0d9cbf8 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 29 Jan 2026 15:33:24 -0600
Subject: [PATCH] config stack

---
 esphome/components/json/json_util.h          | 4 ++--
 esphome/components/web_server/web_server.cpp | 8 ++++----
 esphome/components/web_server/web_server.h   | 2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/esphome/components/json/json_util.h b/esphome/components/json/json_util.h
index 30cf37a90e..596573701b 100644
--- a/esphome/components/json/json_util.h
+++ b/esphome/components/json/json_util.h
@@ -17,9 +17,9 @@ namespace esphome {
 namespace json {
 
 /// Buffer for JSON serialization that uses stack allocation for small payloads.
-/// Template parameter STACK_SIZE specifies the stack buffer size (default 512 bytes).
+/// Template parameter STACK_SIZE specifies the stack buffer size (default 768 bytes).
 /// Supports move semantics for efficient return-by-value.
-template<size_t STACK_SIZE = 512> class JsonBuffer {
+template<size_t STACK_SIZE = 768> class JsonBuffer {
  public:
   /// Construct with known size (typically from measureJson)
   explicit JsonBuffer(size_t size) : size_(size) {
diff --git a/esphome/components/web_server/web_server.cpp b/esphome/components/web_server/web_server.cpp
index 149c23b9b5..86af92078a 100644
--- a/esphome/components/web_server/web_server.cpp
+++ b/esphome/components/web_server/web_server.cpp
@@ -320,7 +320,7 @@ void DeferredUpdateEventSourceList::on_client_connect_(DeferredUpdateEventSource
   ws->defer([ws, source]() {
     // Configure reconnect timeout and send config
     // this should always go through since the AsyncEventSourceClient event queue is empty on connect
-    std::string message = ws->get_config_json();
+    auto message = ws->get_config_json();
     source->try_send_nodefer(message.c_str(), "ping", millis(), 30000);
 
 #ifdef USE_WEBSERVER_SORTING
@@ -329,10 +329,10 @@ void DeferredUpdateEventSourceList::on_client_connect_(DeferredUpdateEventSource
       JsonObject root = builder.root();
       root[ESPHOME_F("name")] = group.second.name;
       root[ESPHOME_F("sorting_weight")] = group.second.weight;
-      message = builder.serialize();
+      auto group_msg = builder.serialize();
 
       // up to 31 groups should be able to be queued initially without defer
-      source->try_send_nodefer(message.c_str(), "sorting_group");
+      source->try_send_nodefer(group_msg.c_str(), "sorting_group");
     }
 #endif
 
@@ -365,7 +365,7 @@ void WebServer::set_css_include(const char *css_include) { this->css_include_ =
 void WebServer::set_js_include(const char *js_include) { this->js_include_ = js_include; }
 #endif
 
-std::string WebServer::get_config_json() {
+json::JsonBuffer<> WebServer::get_config_json() {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
diff --git a/esphome/components/web_server/web_server.h b/esphome/components/web_server/web_server.h
index ed1e492f90..8d6a747bcc 100644
--- a/esphome/components/web_server/web_server.h
+++ b/esphome/components/web_server/web_server.h
@@ -264,7 +264,7 @@ class WebServer : public Controller,
   void handle_index_request(AsyncWebServerRequest *request);
 
   /// Return the webserver configuration as JSON.
-  std::string get_config_json();
+  json::JsonBuffer<> get_config_json();
 
 #ifdef USE_WEBSERVER_CSS_INCLUDE
   /// Handle included css request under '/0.css'.