From 76cdef966bf2559b99deaa08214ac0a124e80531 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 4 Aug 2025 11:14:22 -1000
Subject: [PATCH 1/2] fix

---
 esphome/components/api/custom_api_device.h | 36 ++++++----------------
 1 file changed, 10 insertions(+), 26 deletions(-)

diff --git a/esphome/components/api/custom_api_device.h b/esphome/components/api/custom_api_device.h
index f67a0832be..2e7bb705af 100644
--- a/esphome/components/api/custom_api_device.h
+++ b/esphome/components/api/custom_api_device.h
@@ -61,7 +61,8 @@ class CustomAPIDevice {
   void register_service(void (T::*callback)(Ts...), const std::string &name,
                         const std::array<std::string, sizeof...(Ts)> &arg_names) {
     static_assert(
-        false, "register_service() requires 'custom_services: true' in the 'api:' section of your YAML configuration");
+        sizeof(T) == 0,
+        "register_service() requires 'custom_services: true' in the 'api:' section of your YAML configuration");
   }
 #endif
 
@@ -91,7 +92,8 @@ class CustomAPIDevice {
 #else
   template<typename T> void register_service(void (T::*callback)(), const std::string &name) {
     static_assert(
-        false, "register_service() requires 'custom_services: true' in the 'api:' section of your YAML configuration");
+        sizeof(T) == 0,
+        "register_service() requires 'custom_services: true' in the 'api:' section of your YAML configuration");
   }
 #endif
 
@@ -151,15 +153,17 @@ class CustomAPIDevice {
   template<typename T>
   void subscribe_homeassistant_state(void (T::*callback)(std::string), const std::string &entity_id,
                                      const std::string &attribute = "") {
-    static_assert(false, "subscribe_homeassistant_state() requires 'homeassistant_states: true' in the 'api:' section "
-                         "of your YAML configuration");
+    static_assert(sizeof(T) == 0,
+                  "subscribe_homeassistant_state() requires 'homeassistant_states: true' in the 'api:' section "
+                  "of your YAML configuration");
   }
 
   template<typename T>
   void subscribe_homeassistant_state(void (T::*callback)(std::string, std::string), const std::string &entity_id,
                                      const std::string &attribute = "") {
-    static_assert(false, "subscribe_homeassistant_state() requires 'homeassistant_states: true' in the 'api:' section "
-                         "of your YAML configuration");
+    static_assert(sizeof(T) == 0,
+                  "subscribe_homeassistant_state() requires 'homeassistant_states: true' in the 'api:' section "
+                  "of your YAML configuration");
   }
 #endif
 
@@ -248,26 +252,6 @@ class CustomAPIDevice {
     }
     global_api_server->send_homeassistant_service_call(resp);
   }
-#else
-  void call_homeassistant_service(const std::string &service_name) {
-    static_assert(false, "call_homeassistant_service() requires 'homeassistant_services: true' in the 'api:' section "
-                         "of your YAML configuration");
-  }
-
-  void call_homeassistant_service(const std::string &service_name, const std::map<std::string, std::string> &data) {
-    static_assert(false, "call_homeassistant_service() requires 'homeassistant_services: true' in the 'api:' section "
-                         "of your YAML configuration");
-  }
-
-  void fire_homeassistant_event(const std::string &event_name) {
-    static_assert(false, "fire_homeassistant_event() requires 'homeassistant_services: true' in the 'api:' section of "
-                         "your YAML configuration");
-  }
-
-  void fire_homeassistant_event(const std::string &service_name, const std::map<std::string, std::string> &data) {
-    static_assert(false, "fire_homeassistant_event() requires 'homeassistant_services: true' in the 'api:' section of "
-                         "your YAML configuration");
-  }
 #endif
 };
 

From fb1d2368a91c6deba836d5085c5579f69ebad370 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 4 Aug 2025 11:15:47 -1000
Subject: [PATCH 2/2] fix

---
 esphome/components/api/custom_api_device.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/esphome/components/api/custom_api_device.h b/esphome/components/api/custom_api_device.h
index 2e7bb705af..44f9eee571 100644
--- a/esphome/components/api/custom_api_device.h
+++ b/esphome/components/api/custom_api_device.h
@@ -252,6 +252,28 @@ class CustomAPIDevice {
     }
     global_api_server->send_homeassistant_service_call(resp);
   }
+#else
+  template<typename T = void> void call_homeassistant_service(const std::string &service_name) {
+    static_assert(sizeof(T) == 0, "call_homeassistant_service() requires 'homeassistant_services: true' in the 'api:' "
+                                  "section of your YAML configuration");
+  }
+
+  template<typename T = void>
+  void call_homeassistant_service(const std::string &service_name, const std::map<std::string, std::string> &data) {
+    static_assert(sizeof(T) == 0, "call_homeassistant_service() requires 'homeassistant_services: true' in the 'api:' "
+                                  "section of your YAML configuration");
+  }
+
+  template<typename T = void> void fire_homeassistant_event(const std::string &event_name) {
+    static_assert(sizeof(T) == 0, "fire_homeassistant_event() requires 'homeassistant_services: true' in the 'api:' "
+                                  "section of your YAML configuration");
+  }
+
+  template<typename T = void>
+  void fire_homeassistant_event(const std::string &service_name, const std::map<std::string, std::string> &data) {
+    static_assert(sizeof(T) == 0, "fire_homeassistant_event() requires 'homeassistant_services: true' in the 'api:' "
+                                  "section of your YAML configuration");
+  }
 #endif
 };