From 3560d6ca9698aa4f29eeff4e77c169bf1e284764 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 29 Sep 2025 12:45:24 -0500
Subject: [PATCH] sane

---
 esphome/components/api/__init__.py  | 35 ++++++++++++++++++++++-------
 esphome/components/api/api_server.h |  7 ++----
 2 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/esphome/components/api/__init__.py b/esphome/components/api/__init__.py
index 9336d31491..c91051ba20 100644
--- a/esphome/components/api/__init__.py
+++ b/esphome/components/api/__init__.py
@@ -160,12 +160,29 @@ CONFIG_SCHEMA = cv.All(
             cv.Optional(CONF_ON_CLIENT_DISCONNECTED): automation.validate_automation(
                 single=True
             ),
-            cv.SplitDefault(CONF_LISTEN_BACKLOG, esp8266=1, default=4): cv.int_range(
-                min=1, max=10
-            ),
-            cv.SplitDefault(CONF_MAX_CONNECTIONS, esp8266=4, default=8): cv.int_range(
-                min=1, max=20
-            ),
+            # Connection limits to prevent memory exhaustion on resource-constrained devices
+            # Each connection uses ~500-1000 bytes of RAM plus system resources
+            # Platform defaults based on available RAM and network stack implementation:
+            cv.SplitDefault(
+                CONF_LISTEN_BACKLOG,
+                esp8266=1,  # Limited RAM (~40KB free), LWIP raw sockets
+                esp32=4,  # More RAM (520KB), BSD sockets
+                rp2040=1,  # Limited RAM (264KB), LWIP raw sockets like ESP8266
+                bk72xx=4,  # Moderate RAM, BSD-style sockets
+                rtl87xx=4,  # Moderate RAM, BSD-style sockets
+                host=4,  # Abundant resources
+                ln882x=4,  # Moderate RAM
+            ): cv.int_range(min=1, max=10),
+            cv.SplitDefault(
+                CONF_MAX_CONNECTIONS,
+                esp8266=4,  # ~40KB free RAM, each connection uses ~500-1000 bytes
+                esp32=8,  # 520KB RAM available
+                rp2040=4,  # 264KB RAM but LWIP constraints
+                bk72xx=8,  # Moderate RAM
+                rtl87xx=8,  # Moderate RAM
+                host=8,  # Abundant resources
+                ln882x=8,  # Moderate RAM
+            ): cv.int_range(min=1, max=20),
         }
     ).extend(cv.COMPONENT_SCHEMA),
     cv.rename_key(CONF_SERVICES, CONF_ACTIONS),
@@ -184,8 +201,10 @@ async def to_code(config):
         cg.add(var.set_password(config[CONF_PASSWORD]))
     cg.add(var.set_reboot_timeout(config[CONF_REBOOT_TIMEOUT]))
     cg.add(var.set_batch_delay(config[CONF_BATCH_DELAY]))
-    cg.add(var.set_listen_backlog(config[CONF_LISTEN_BACKLOG]))
-    cg.add(var.set_max_connections(config[CONF_MAX_CONNECTIONS]))
+    if CONF_LISTEN_BACKLOG in config:
+        cg.add(var.set_listen_backlog(config[CONF_LISTEN_BACKLOG]))
+    if CONF_MAX_CONNECTIONS in config:
+        cg.add(var.set_max_connections(config[CONF_MAX_CONNECTIONS]))
 
     # Set USE_API_SERVICES if any services are enabled
     if config.get(CONF_ACTIONS) or config[CONF_CUSTOM_SERVICES]:
diff --git a/esphome/components/api/api_server.h b/esphome/components/api/api_server.h
index f0c51af460..b9049c1700 100644
--- a/esphome/components/api/api_server.h
+++ b/esphome/components/api/api_server.h
@@ -191,13 +191,10 @@ class APIServer : public Component, public Controller {
   // Group smaller types together
   uint16_t port_{6053};
   uint16_t batch_delay_{100};
-#ifdef USE_ESP8266
-  uint8_t listen_backlog_{1};
-  uint8_t max_connections_{4};
-#else
+  // Connection limits - these defaults will be overridden by config values
+  // from cv.SplitDefault in __init__.py which sets platform-specific defaults
   uint8_t listen_backlog_{4};
   uint8_t max_connections_{8};
-#endif
   bool shutting_down_ = false;
   // 7 bytes used, 1 byte padding