From 4509e5d3888ee39405084ea49466070e34aa7151 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 8 Sep 2026 02:48:58 +0200
Subject: [PATCH] [api] Assert at compile time that decodable messages carry no
 vtable

Every build below VERY_VERBOSE now checks the base class and each generated decodable
message with std::is_polymorphic_v, so a vtable cannot come back unnoticed.
---
 esphome/components/api/api_pb2.cpp  | 170 ++++++++++++++++++++++++++++
 esphome/components/api/proto.h      |   5 +
 script/api_protobuf/api_protobuf.py |  11 ++
 3 files changed, 186 insertions(+)

diff --git a/esphome/components/api/api_pb2.cpp b/esphome/components/api/api_pb2.cpp
index d0aff048f8..916aa2ba7e 100644
--- a/esphome/components/api/api_pb2.cpp
+++ b/esphome/components/api/api_pb2.cpp
@@ -4188,5 +4188,175 @@ uint32_t BluetoothSetConnectionParamsResponse::calc_size_msg(const void *self) {
   return size;
 }
 #endif
+#ifndef HAS_PROTO_MESSAGE_DUMP
+static_assert(!std::is_polymorphic_v<HelloRequest>, "decodable messages carry no vtable");
+static_assert(!std::is_polymorphic_v<DisconnectRequest>, "decodable messages carry no vtable");
+static_assert(!std::is_polymorphic_v<DisconnectResponse>, "decodable messages carry no vtable");
+static_assert(!std::is_polymorphic_v<PingRequest>, "decodable messages carry no vtable");
+static_assert(!std::is_polymorphic_v<PingResponse>, "decodable messages carry no vtable");
+#ifdef USE_COVER
+static_assert(!std::is_polymorphic_v<CoverCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_FAN
+static_assert(!std::is_polymorphic_v<FanCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_LIGHT
+static_assert(!std::is_polymorphic_v<LightCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_SWITCH
+static_assert(!std::is_polymorphic_v<SwitchCommandRequest>, "decodable messages carry no vtable");
+#endif
+static_assert(!std::is_polymorphic_v<SubscribeLogsRequest>, "decodable messages carry no vtable");
+#ifdef USE_API_NOISE
+static_assert(!std::is_polymorphic_v<NoiseEncryptionSetKeyRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_API_HOMEASSISTANT_ACTION_RESPONSES
+static_assert(!std::is_polymorphic_v<HomeassistantActionResponse>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_API_HOMEASSISTANT_STATES
+static_assert(!std::is_polymorphic_v<HomeAssistantStateResponse>, "decodable messages carry no vtable");
+#endif
+static_assert(!std::is_polymorphic_v<DSTRule>, "decodable messages carry no vtable");
+static_assert(!std::is_polymorphic_v<ParsedTimezone>, "decodable messages carry no vtable");
+static_assert(!std::is_polymorphic_v<GetTimeResponse>, "decodable messages carry no vtable");
+#ifdef USE_API_USER_DEFINED_ACTIONS
+static_assert(!std::is_polymorphic_v<ExecuteServiceArgument>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_API_USER_DEFINED_ACTIONS
+static_assert(!std::is_polymorphic_v<ExecuteServiceRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_CAMERA
+static_assert(!std::is_polymorphic_v<CameraImageRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_CLIMATE
+static_assert(!std::is_polymorphic_v<ClimateCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_WATER_HEATER
+static_assert(!std::is_polymorphic_v<WaterHeaterCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_NUMBER
+static_assert(!std::is_polymorphic_v<NumberCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_SELECT
+static_assert(!std::is_polymorphic_v<SelectCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_SIREN
+static_assert(!std::is_polymorphic_v<SirenCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_LOCK
+static_assert(!std::is_polymorphic_v<LockCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BUTTON
+static_assert(!std::is_polymorphic_v<ButtonCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_MEDIA_PLAYER
+static_assert(!std::is_polymorphic_v<MediaPlayerCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY
+static_assert(!std::is_polymorphic_v<SubscribeBluetoothLEAdvertisementsRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
+static_assert(!std::is_polymorphic_v<BluetoothDeviceRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
+static_assert(!std::is_polymorphic_v<BluetoothGATTGetServicesRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
+static_assert(!std::is_polymorphic_v<BluetoothGATTReadRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
+static_assert(!std::is_polymorphic_v<BluetoothGATTWriteRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
+static_assert(!std::is_polymorphic_v<BluetoothGATTReadDescriptorRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
+static_assert(!std::is_polymorphic_v<BluetoothGATTWriteDescriptorRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
+static_assert(!std::is_polymorphic_v<BluetoothGATTNotifyRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY
+static_assert(!std::is_polymorphic_v<BluetoothScannerSetModeRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<SubscribeVoiceAssistantRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<VoiceAssistantResponse>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<VoiceAssistantEventData>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<VoiceAssistantEventResponse>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<VoiceAssistantAudio>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<VoiceAssistantTimerEventResponse>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<VoiceAssistantAnnounceRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<VoiceAssistantExternalWakeWord>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<VoiceAssistantConfigurationRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VOICE_ASSISTANT
+static_assert(!std::is_polymorphic_v<VoiceAssistantSetConfiguration>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_ALARM_CONTROL_PANEL
+static_assert(!std::is_polymorphic_v<AlarmControlPanelCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_TEXT
+static_assert(!std::is_polymorphic_v<TextCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_DATETIME_DATE
+static_assert(!std::is_polymorphic_v<DateCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_DATETIME_TIME
+static_assert(!std::is_polymorphic_v<TimeCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_VALVE
+static_assert(!std::is_polymorphic_v<ValveCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_DATETIME_DATETIME
+static_assert(!std::is_polymorphic_v<DateTimeCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_UPDATE
+static_assert(!std::is_polymorphic_v<UpdateCommandRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_ZWAVE_PROXY
+static_assert(!std::is_polymorphic_v<ZWaveProxyFrame>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_ZWAVE_PROXY
+static_assert(!std::is_polymorphic_v<ZWaveProxyRequest>, "decodable messages carry no vtable");
+#endif
+#if defined(USE_IR_RF) || defined(USE_RADIO_FREQUENCY)
+static_assert(!std::is_polymorphic_v<InfraredRFTransmitRawTimingsRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_SERIAL_PROXY
+static_assert(!std::is_polymorphic_v<SerialProxyConfigureRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_SERIAL_PROXY
+static_assert(!std::is_polymorphic_v<SerialProxyWriteRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_SERIAL_PROXY
+static_assert(!std::is_polymorphic_v<SerialProxySetModemPinsRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_SERIAL_PROXY
+static_assert(!std::is_polymorphic_v<SerialProxyGetModemPinsRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_SERIAL_PROXY
+static_assert(!std::is_polymorphic_v<SerialProxyRequest>, "decodable messages carry no vtable");
+#endif
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
+static_assert(!std::is_polymorphic_v<BluetoothSetConnectionParamsRequest>, "decodable messages carry no vtable");
+#endif
+#endif
 
 }  // namespace esphome::api
diff --git a/esphome/components/api/proto.h b/esphome/components/api/proto.h
index 4e19e5016a..e48364885d 100644
--- a/esphome/components/api/proto.h
+++ b/esphome/components/api/proto.h
@@ -10,6 +10,7 @@
 
 #include <cassert>
 #include <cstring>
+#include <type_traits>
 #include <vector>
 
 #ifdef ESPHOME_LOG_HAS_VERY_VERBOSE
@@ -741,6 +742,10 @@ class ProtoDecodableMessage : public ProtoMessage {
    */
   static uint32_t count_repeated_field(const uint8_t *buffer, size_t length, uint32_t target_field_id);
 };
+#ifndef HAS_PROTO_MESSAGE_DUMP
+// decode() passes decode_field explicitly, so nothing here may add a vtable
+static_assert(!std::is_polymorphic_v<ProtoDecodableMessage>, "decodable messages carry no vtable");
+#endif
 
 class ProtoSize {
  public:
diff --git a/script/api_protobuf/api_protobuf.py b/script/api_protobuf/api_protobuf.py
index d0b763cb37..6067832ea6 100755
--- a/script/api_protobuf/api_protobuf.py
+++ b/script/api_protobuf/api_protobuf.py
@@ -3385,6 +3385,7 @@ static void dump_bytes_field(DumpBuffer &out, const char *field_name, const uint
 
     # Generate message types with base class information
     # Simple grouping by ifdef
+    decodable_messages: list[tuple[str, str | None]] = []
     current_ifdef = None
 
     for m in mt:
@@ -3401,6 +3402,8 @@ static void dump_bytes_field(DumpBuffer &out, const char *field_name, const uint
             continue
 
         s, c, dc = build_message_type(m, base_class_fields, message_source_map)
+        if message_source_map[m.name] in (SOURCE_BOTH, SOURCE_CLIENT):
+            decodable_messages.append((m.name, message_ifdef_map.get(m.name)))
         msg_ifdef = message_ifdef_map.get(m.name)
 
         # Handle ifdef changes
@@ -3427,6 +3430,14 @@ static void dump_bytes_field(DumpBuffer &out, const char *field_name, const uint
         cpp += "#endif\n"
         dump_cpp += "#endif\n"
 
+    # decode() passes decode_field explicitly, so without the dump virtuals no decodable message
+    # may carry a vtable; a build at any level below VERY_VERBOSE proves it
+    cpp += "#ifndef HAS_PROTO_MESSAGE_DUMP\n"
+    for name, msg_ifdef in decodable_messages:
+        line = f'static_assert(!std::is_polymorphic_v<{name}>, "decodable messages carry no vtable");'
+        cpp += "\n".join(wrap_with_ifdef(line, msg_ifdef)) + "\n"
+    cpp += "#endif\n"
+
     content += """\
 
 }  // namespace esphome::api