[api] Devirtualize protobuf encode/calculate_size (#14449)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

esphome/components/api/api_connection.h

@@ -129,7 +129,7 @@ class APIConnection final : public APIServerConnectionBase {
   void send_homeassistant_action(const HomeassistantActionRequest &call) {
     if (!this->flags_.service_call_subscription)
       return;
-    this->send_message(call, HomeassistantActionRequest::MESSAGE_TYPE);
+    this->send_message(call);
   }
 #ifdef USE_API_HOMEASSISTANT_ACTION_RESPONSES
   void on_homeassistant_action_response(const HomeassistantActionResponse &msg) override;
@@ -153,7 +153,7 @@ class APIConnection final : public APIServerConnectionBase {
 #ifdef USE_HOMEASSISTANT_TIME
   void send_time_request() {
     GetTimeRequest req;
-    this->send_message(req, GetTimeRequest::MESSAGE_TYPE);
+    this->send_message(req);
   }
 #endif
 
@@ -263,7 +263,19 @@ class APIConnection final : public APIServerConnectionBase {
 
   void on_fatal_error() override;
   void on_no_setup_connection() override;
-  bool send_message_impl(const ProtoMessage &msg, uint8_t message_type) override;
+
+  // Function pointer type for type-erased message encoding
+  using MessageEncodeFn = void (*)(const void *, ProtoWriteBuffer &);
+  // Function pointer type for type-erased size calculation
+  using CalculateSizeFn = uint32_t (*)(const void *);
+
+  template<typename T> bool send_message(const T &msg) {
+    if constexpr (T::ESTIMATED_SIZE == 0) {
+      return this->send_message_(0, T::MESSAGE_TYPE, &encode_msg_noop, &msg);
+    } else {
+      return this->send_message_(msg.calculate_size(), T::MESSAGE_TYPE, &proto_encode_msg<T>, &msg);
+    }
+  }
 
   void prepare_first_message_buffer(std::vector<uint8_t> &shared_buf, size_t header_padding, size_t total_size) {
     shared_buf.clear();
@@ -318,28 +330,68 @@ class APIConnection final : public APIServerConnectionBase {
   void process_state_subscriptions_();
 #endif
 
-  // Non-template helper to encode any ProtoMessage
-  static uint16_t encode_message_to_buffer(ProtoMessage &msg, uint8_t message_type, APIConnection *conn,
-                                           uint32_t remaining_size);
-
-  // Helper to fill entity state base and encode message
-  static uint16_t fill_and_encode_entity_state(EntityBase *entity, StateResponseProtoMessage &msg, uint8_t message_type,
-                                               APIConnection *conn, uint32_t remaining_size) {
-    msg.key = entity->get_object_id_hash();
-#ifdef USE_DEVICES
-    msg.device_id = entity->get_device_id();
-#endif
-    return encode_message_to_buffer(msg, message_type, conn, remaining_size);
+  // Size thunk — converts void* back to concrete type for direct calculate_size() call
+  template<typename T> static uint32_t calc_size(const void *msg) {
+    return static_cast<const T *>(msg)->calculate_size();
   }
 
-  // Helper to fill entity info base and encode message
-  static uint16_t fill_and_encode_entity_info(EntityBase *entity, InfoResponseProtoMessage &msg, uint8_t message_type,
-                                              APIConnection *conn, uint32_t remaining_size);
+  // Shared no-op encode thunk for empty messages (ESTIMATED_SIZE == 0)
+  static void encode_msg_noop(const void *, ProtoWriteBuffer &) {}
 
-  // Wrapper for entity types that have a device_class field
+  // Non-template buffer management for send_message
+  bool send_message_(uint32_t payload_size, uint8_t message_type, MessageEncodeFn encode_fn, const void *msg);
+
+  // Non-template buffer management for batch encoding
+  static uint16_t encode_to_buffer(uint32_t calculated_size, MessageEncodeFn encode_fn, const void *msg,
+                                   APIConnection *conn, uint32_t remaining_size);
+
+  // Thin template wrapper — computes size, delegates buffer work to non-template helper
+  template<typename T> static uint16_t encode_message_to_buffer(T &msg, APIConnection *conn, uint32_t remaining_size) {
+    if constexpr (T::ESTIMATED_SIZE == 0) {
+      return encode_to_buffer(0, &encode_msg_noop, &msg, conn, remaining_size);
+    } else {
+      return encode_to_buffer(msg.calculate_size(), &proto_encode_msg<T>, &msg, conn, remaining_size);
+    }
+  }
+
+  // Non-template core — fills state fields and encodes
+  static uint16_t fill_and_encode_entity_state(EntityBase *entity, StateResponseProtoMessage &msg,
+                                               CalculateSizeFn size_fn, MessageEncodeFn encode_fn, APIConnection *conn,
+                                               uint32_t remaining_size);
+
+  // Thin template wrapper
+  template<typename T>
+  static uint16_t fill_and_encode_entity_state(EntityBase *entity, T &msg, APIConnection *conn,
+                                               uint32_t remaining_size) {
+    return fill_and_encode_entity_state(entity, msg, &calc_size<T>, &proto_encode_msg<T>, conn, remaining_size);
+  }
+
+  // Non-template core — fills info fields, allocates buffers, and encodes
+  static uint16_t fill_and_encode_entity_info(EntityBase *entity, InfoResponseProtoMessage &msg,
+                                              CalculateSizeFn size_fn, MessageEncodeFn encode_fn, APIConnection *conn,
+                                              uint32_t remaining_size);
+
+  // Thin template wrapper
+  template<typename T>
+  static uint16_t fill_and_encode_entity_info(EntityBase *entity, T &msg, APIConnection *conn,
+                                              uint32_t remaining_size) {
+    return fill_and_encode_entity_info(entity, msg, &calc_size<T>, &proto_encode_msg<T>, conn, remaining_size);
+  }
+
+  // Non-template core — fills device_class, then delegates to fill_and_encode_entity_info
   static uint16_t fill_and_encode_entity_info_with_device_class(EntityBase *entity, InfoResponseProtoMessage &msg,
-                                                                StringRef &device_class_field, uint8_t message_type,
-                                                                APIConnection *conn, uint32_t remaining_size);
+                                                                StringRef &device_class_field, CalculateSizeFn size_fn,
+                                                                MessageEncodeFn encode_fn, APIConnection *conn,
+                                                                uint32_t remaining_size);
+
+  // Thin template wrapper
+  template<typename T>
+  static uint16_t fill_and_encode_entity_info_with_device_class(EntityBase *entity, T &msg,
+                                                                StringRef &device_class_field, APIConnection *conn,
+                                                                uint32_t remaining_size) {
+    return fill_and_encode_entity_info_with_device_class(entity, msg, device_class_field, &calc_size<T>,
+                                                         &proto_encode_msg<T>, conn, remaining_size);
+  }
 
 #ifdef USE_VOICE_ASSISTANT
   // Helper to check voice assistant validity and connection ownership

esphome/components/api/api_pb2_service.h

@@ -19,14 +19,6 @@ class APIServerConnectionBase : public ProtoService {
  public:
 #endif
 
-  bool send_message(const ProtoMessage &msg, uint8_t message_type) {
-#ifdef HAS_PROTO_MESSAGE_DUMP
-    DumpBuffer dump_buf;
-    this->log_send_message_(msg.message_name(), msg.dump_to(dump_buf));
-#endif
-    return this->send_message_impl(msg, message_type);
-  }
-
   virtual void on_hello_request(const HelloRequest &value){};
 
   virtual void on_disconnect_request(){};

esphome/components/api/api_server.cpp

@@ -359,11 +359,11 @@ void APIServer::on_update(update::UpdateEntity *obj) {
 #endif
 
 #ifdef USE_ZWAVE_PROXY
-void APIServer::on_zwave_proxy_request(const esphome::api::ProtoMessage &msg) {
+void APIServer::on_zwave_proxy_request(const ZWaveProxyRequest &msg) {
   // We could add code to manage a second subscription type, but, since this message type is
   //  very infrequent and small, we simply send it to all clients
   for (auto &c : this->clients_)
-    c->send_message(msg, api::ZWaveProxyRequest::MESSAGE_TYPE);
+    c->send_message(msg);
 }
 #endif
 
@@ -531,7 +531,7 @@ bool APIServer::update_noise_psk_(const SavedNoisePsk &new_psk, const LogString
       this->set_noise_psk(active_psk);
       for (auto &c : this->clients_) {
         DisconnectRequest req;
-        c->send_message(req, DisconnectRequest::MESSAGE_TYPE);
+        c->send_message(req);
       }
     });
   }
@@ -631,7 +631,7 @@ void APIServer::on_shutdown() {
   // Send disconnect requests to all connected clients
   for (auto &c : this->clients_) {
     DisconnectRequest req;
-    if (!c->send_message(req, DisconnectRequest::MESSAGE_TYPE)) {
+    if (!c->send_message(req)) {
       // If we can't send the disconnect request directly (tx_buffer full),
       // schedule it at the front of the batch so it will be sent with priority
       c->schedule_message_front_(nullptr, DisconnectRequest::MESSAGE_TYPE, DisconnectRequest::ESTIMATED_SIZE);

esphome/components/api/api_server.h

@@ -179,7 +179,7 @@ class APIServer : public Component,
   void on_update(update::UpdateEntity *obj) override;
 #endif
 #ifdef USE_ZWAVE_PROXY
-  void on_zwave_proxy_request(const esphome::api::ProtoMessage &msg);
+  void on_zwave_proxy_request(const ZWaveProxyRequest &msg);
 #endif
 #ifdef USE_IR_RF
   void send_infrared_rf_receive_event(uint32_t device_id, uint32_t key, const std::vector<int32_t> *timings);

esphome/components/api/list_entities.cpp

@@ -94,7 +94,7 @@ ListEntitiesIterator::ListEntitiesIterator(APIConnection *client) : client_(clie
 #ifdef USE_API_USER_DEFINED_ACTIONS
 bool ListEntitiesIterator::on_service(UserServiceDescriptor *service) {
   auto resp = service->encode_list_service_response();
-  return this->client_->send_message(resp, ListEntitiesServicesResponse::MESSAGE_TYPE);
+  return this->client_->send_message(resp);
 }
 #endif
 

esphome/components/api/proto.h

@@ -364,7 +364,11 @@ class ProtoWriteBuffer {
   /// Encode a packed repeated sint32 field (zero-copy from vector)
   void encode_packed_sint32(uint32_t field_id, const std::vector<int32_t> &values);
   /// Encode a nested message field (force=true for repeated, false for singular)
-  void encode_message(uint32_t field_id, const ProtoMessage &value, bool force = true);
+  /// Templated so concrete message type is preserved for direct encode/calculate_size calls.
+  template<typename T> void encode_message(uint32_t field_id, const T &value, bool force = true);
+  // Non-template core for encode_message — all buffer work happens here
+  void encode_message(uint32_t field_id, uint32_t msg_length_bytes, const void *value,
+                      void (*encode_fn)(const void *, ProtoWriteBuffer &), bool force);
   std::vector<uint8_t> *get_buffer() const { return buffer_; }
 
  protected:
@@ -452,20 +456,20 @@ class DumpBuffer {
 
 class ProtoMessage {
  public:
-  // Default implementation for messages with no fields
-  virtual void encode(ProtoWriteBuffer &buffer) const {}
-  // Default implementation for messages with no fields
-  virtual void calculate_size(ProtoSize &size) const {}
-  // Convenience: calculate and return size directly (defined after ProtoSize)
-  uint32_t calculated_size() const;
+  // Non-virtual defaults for messages with no fields.
+  // Concrete message classes hide these with their own implementations.
+  // All call sites use templates to preserve the concrete type, so virtual
+  // dispatch is not needed. This eliminates per-message vtable entries for
+  // encode/calculate_size, saving ~1.3 KB of flash across all message types.
+  void encode(ProtoWriteBuffer &buffer) const {}
+  uint32_t calculate_size() const { return 0; }
 #ifdef HAS_PROTO_MESSAGE_DUMP
   virtual const char *dump_to(DumpBuffer &out) const = 0;
   virtual const char *message_name() const { return "unknown"; }
 #endif
 
  protected:
-  // Non-virtual: messages are never deleted polymorphically.
-  // Protected prevents accidental `delete base_ptr` (compile error).
+  // Non-virtual destructor is protected to prevent polymorphic deletion.
   ~ProtoMessage() = default;
 };
 
@@ -494,32 +498,7 @@ class ProtoDecodableMessage : public ProtoMessage {
 };
 
 class ProtoSize {
- private:
-  uint32_t total_size_ = 0;
-
  public:
-  /**
-   * @brief ProtoSize class for Protocol Buffer serialization size calculation
-   *
-   * This class provides methods to calculate the exact byte counts needed
-   * for encoding various Protocol Buffer field types. The class now uses an
-   * object-based approach to reduce parameter passing overhead while keeping
-   * varint calculation methods static for external use.
-   *
-   * Implements Protocol Buffer encoding size calculation according to:
-   * https://protobuf.dev/programming-guides/encoding/
-   *
-   * Key features:
-   * - Object-based approach reduces flash usage by eliminating parameter passing
-   * - Early-return optimization for zero/default values
-   * - Static varint methods for external callers
-   * - Specialized handling for different field types according to protobuf spec
-   */
-
-  ProtoSize() = default;
-
-  uint32_t get_size() const { return total_size_; }
-
   /**
    * @brief Calculates the size in bytes needed to encode a uint32_t value as a varint
    *
@@ -616,320 +595,77 @@ class ProtoSize {
     return varint(tag);
   }
 
-  /**
-   * @brief Common parameters for all add_*_field methods
-   *
-   * All add_*_field methods follow these common patterns:
-   *   * @param field_id_size Pre-calculated size of the field ID in bytes
-   * @param value The value to calculate size for (type varies)
-   * @param force Whether to calculate size even if the value is default/zero/empty
-   *
-   * Each method follows this implementation pattern:
-   * 1. Skip calculation if value is default (0, false, empty) and not forced
-   * 2. Calculate the size based on the field's encoding rules
-   * 3. Add the field_id_size + calculated value size to total_size
-   */
-
-  /**
-   * @brief Calculates and adds the size of an int32 field to the total message size
-   */
-  inline void add_int32(uint32_t field_id_size, int32_t value) {
-    if (value != 0) {
-      add_int32_force(field_id_size, value);
-    }
+  // Static methods that RETURN size contribution (no ProtoSize object needed).
+  // Used by generated calculate_size() methods to accumulate into a plain uint32_t register.
+  static constexpr uint32_t calc_int32(uint32_t field_id_size, int32_t value) {
+    return value ? field_id_size + (value < 0 ? 10 : varint(static_cast<uint32_t>(value))) : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of an int32 field to the total message size (force version)
-   */
-  inline void add_int32_force(uint32_t field_id_size, int32_t value) {
-    // Always calculate size when forced
-    // Negative values are encoded as 10-byte varints in protobuf
-    total_size_ += field_id_size + (value < 0 ? 10 : varint(static_cast<uint32_t>(value)));
+  static constexpr uint32_t calc_int32_force(uint32_t field_id_size, int32_t value) {
+    return field_id_size + (value < 0 ? 10 : varint(static_cast<uint32_t>(value)));
   }
-
-  /**
-   * @brief Calculates and adds the size of a uint32 field to the total message size
-   */
-  inline void add_uint32(uint32_t field_id_size, uint32_t value) {
-    if (value != 0) {
-      add_uint32_force(field_id_size, value);
-    }
+  static constexpr uint32_t calc_uint32(uint32_t field_id_size, uint32_t value) {
+    return value ? field_id_size + varint(value) : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of a uint32 field to the total message size (force version)
-   */
-  inline void add_uint32_force(uint32_t field_id_size, uint32_t value) {
-    // Always calculate size when force is true
-    total_size_ += field_id_size + varint(value);
+  static constexpr uint32_t calc_uint32_force(uint32_t field_id_size, uint32_t value) {
+    return field_id_size + varint(value);
   }
-
-  /**
-   * @brief Calculates and adds the size of a boolean field to the total message size
-   */
-  inline void add_bool(uint32_t field_id_size, bool value) {
-    if (value) {
-      // Boolean fields always use 1 byte when true
-      total_size_ += field_id_size + 1;
-    }
+  static constexpr uint32_t calc_bool(uint32_t field_id_size, bool value) { return value ? field_id_size + 1 : 0; }
+  static constexpr uint32_t calc_bool_force(uint32_t field_id_size) { return field_id_size + 1; }
+  static constexpr uint32_t calc_float(uint32_t field_id_size, float value) {
+    return value != 0.0f ? field_id_size + 4 : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of a boolean field to the total message size (force version)
-   */
-  inline void add_bool_force(uint32_t field_id_size, bool value) {
-    // Always calculate size when force is true
-    // Boolean fields always use 1 byte
-    total_size_ += field_id_size + 1;
+  static constexpr uint32_t calc_fixed32(uint32_t field_id_size, uint32_t value) {
+    return value ? field_id_size + 4 : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of a float field to the total message size
-   */
-  inline void add_float(uint32_t field_id_size, float value) {
-    if (value != 0.0f) {
-      total_size_ += field_id_size + 4;
-    }
+  static constexpr uint32_t calc_sfixed32(uint32_t field_id_size, int32_t value) {
+    return value ? field_id_size + 4 : 0;
   }
-
-  // NOTE: add_double_field removed - wire type 1 (64-bit: double) not supported
-  // to reduce overhead on embedded systems
-
-  /**
-   * @brief Calculates and adds the size of a fixed32 field to the total message size
-   */
-  inline void add_fixed32(uint32_t field_id_size, uint32_t value) {
-    if (value != 0) {
-      total_size_ += field_id_size + 4;
-    }
+  static constexpr uint32_t calc_sint32(uint32_t field_id_size, int32_t value) {
+    return value ? field_id_size + varint(encode_zigzag32(value)) : 0;
   }
-
-  // NOTE: add_fixed64_field removed - wire type 1 (64-bit: fixed64) not supported
-  // to reduce overhead on embedded systems
-
-  /**
-   * @brief Calculates and adds the size of a sfixed32 field to the total message size
-   */
-  inline void add_sfixed32(uint32_t field_id_size, int32_t value) {
-    if (value != 0) {
-      total_size_ += field_id_size + 4;
-    }
+  static constexpr uint32_t calc_sint32_force(uint32_t field_id_size, int32_t value) {
+    return field_id_size + varint(encode_zigzag32(value));
   }
-
-  // NOTE: add_sfixed64_field removed - wire type 1 (64-bit: sfixed64) not supported
-  // to reduce overhead on embedded systems
-
-  /**
-   * @brief Calculates and adds the size of a sint32 field to the total message size
-   *
-   * Sint32 fields use ZigZag encoding, which is more efficient for negative values.
-   */
-  inline void add_sint32(uint32_t field_id_size, int32_t value) {
-    if (value != 0) {
-      add_sint32_force(field_id_size, value);
-    }
+  static constexpr uint32_t calc_int64(uint32_t field_id_size, int64_t value) {
+    return value ? field_id_size + varint(value) : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of a sint32 field to the total message size (force version)
-   *
-   * Sint32 fields use ZigZag encoding, which is more efficient for negative values.
-   */
-  inline void add_sint32_force(uint32_t field_id_size, int32_t value) {
-    // Always calculate size when force is true
-    // ZigZag encoding for sint32
-    total_size_ += field_id_size + varint(encode_zigzag32(value));
+  static constexpr uint32_t calc_int64_force(uint32_t field_id_size, int64_t value) {
+    return field_id_size + varint(value);
   }
-
-  /**
-   * @brief Calculates and adds the size of an int64 field to the total message size
-   */
-  inline void add_int64(uint32_t field_id_size, int64_t value) {
-    if (value != 0) {
-      add_int64_force(field_id_size, value);
-    }
+  static constexpr uint32_t calc_uint64(uint32_t field_id_size, uint64_t value) {
+    return value ? field_id_size + varint(value) : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of an int64 field to the total message size (force version)
-   */
-  inline void add_int64_force(uint32_t field_id_size, int64_t value) {
-    // Always calculate size when force is true
-    total_size_ += field_id_size + varint(value);
+  static constexpr uint32_t calc_uint64_force(uint32_t field_id_size, uint64_t value) {
+    return field_id_size + varint(value);
   }
-
-  /**
-   * @brief Calculates and adds the size of a uint64 field to the total message size
-   */
-  inline void add_uint64(uint32_t field_id_size, uint64_t value) {
-    if (value != 0) {
-      add_uint64_force(field_id_size, value);
-    }
+  static constexpr uint32_t calc_length(uint32_t field_id_size, size_t len) {
+    return len ? field_id_size + varint(static_cast<uint32_t>(len)) + static_cast<uint32_t>(len) : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of a uint64 field to the total message size (force version)
-   */
-  inline void add_uint64_force(uint32_t field_id_size, uint64_t value) {
-    // Always calculate size when force is true
-    total_size_ += field_id_size + varint(value);
+  static constexpr uint32_t calc_length_force(uint32_t field_id_size, size_t len) {
+    return field_id_size + varint(static_cast<uint32_t>(len)) + static_cast<uint32_t>(len);
   }
-
-  // NOTE: sint64 support functions (add_sint64_field, add_sint64_field_force) removed
-  // sint64 type is not supported by ESPHome API to reduce overhead on embedded systems
-
-  /**
-   * @brief Calculates and adds the size of a length-delimited field (string/bytes) to the total message size
-   */
-  inline void add_length(uint32_t field_id_size, size_t len) {
-    if (len != 0) {
-      add_length_force(field_id_size, len);
-    }
+  static constexpr uint32_t calc_sint64(uint32_t field_id_size, int64_t value) {
+    return value ? field_id_size + varint(encode_zigzag64(value)) : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of a length-delimited field (string/bytes) to the total message size (repeated
-   * field version)
-   */
-  inline void add_length_force(uint32_t field_id_size, size_t len) {
-    // Always calculate size when force is true
-    // Field ID + length varint + data bytes
-    total_size_ += field_id_size + varint(static_cast<uint32_t>(len)) + static_cast<uint32_t>(len);
+  static constexpr uint32_t calc_sint64_force(uint32_t field_id_size, int64_t value) {
+    return field_id_size + varint(encode_zigzag64(value));
   }
-
-  /**
-   * @brief Adds a pre-calculated size directly to the total
-   *
-   * This is used when we can calculate the total size by multiplying the number
-   * of elements by the bytes per element (for repeated fixed-size types like float, fixed32, etc.)
-   *
-   * @param size The pre-calculated total size to add
-   */
-  inline void add_precalculated_size(uint32_t size) { total_size_ += size; }
-
-  /**
-   * @brief Calculates and adds the size of a nested message field to the total message size
-   *
-   * This helper function directly updates the total_size reference if the nested size
-   * is greater than zero.
-   *
-   * @param nested_size The pre-calculated size of the nested message
-   */
-  inline void add_message_field(uint32_t field_id_size, uint32_t nested_size) {
-    if (nested_size != 0) {
-      add_message_field_force(field_id_size, nested_size);
-    }
+  static constexpr uint32_t calc_fixed64(uint32_t field_id_size, uint64_t value) {
+    return value ? field_id_size + 8 : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of a nested message field to the total message size (force version)
-   *
-   * @param nested_size The pre-calculated size of the nested message
-   */
-  inline void add_message_field_force(uint32_t field_id_size, uint32_t nested_size) {
-    // Always calculate size when force is true
-    // Field ID + length varint + nested message content
-    total_size_ += field_id_size + varint(nested_size) + nested_size;
+  static constexpr uint32_t calc_sfixed64(uint32_t field_id_size, int64_t value) {
+    return value ? field_id_size + 8 : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of a nested message field to the total message size
-   *
-   * This version takes a ProtoMessage object, calculates its size internally,
-   * and updates the total_size reference. This eliminates the need for a temporary variable
-   * at the call site.
-   *
-   * @param message The nested message object
-   */
-  inline void add_message_object(uint32_t field_id_size, const ProtoMessage &message) {
-    // Calculate nested message size by creating a temporary ProtoSize
-    ProtoSize nested_calc;
-    message.calculate_size(nested_calc);
-    uint32_t nested_size = nested_calc.get_size();
-
-    // Use the base implementation with the calculated nested_size
-    add_message_field(field_id_size, nested_size);
+  static constexpr uint32_t calc_message(uint32_t field_id_size, uint32_t nested_size) {
+    return nested_size ? field_id_size + varint(nested_size) + nested_size : 0;
   }
-
-  /**
-   * @brief Calculates and adds the size of a nested message field to the total message size (force version)
-   *
-   * @param message The nested message object
-   */
-  inline void add_message_object_force(uint32_t field_id_size, const ProtoMessage &message) {
-    // Calculate nested message size by creating a temporary ProtoSize
-    ProtoSize nested_calc;
-    message.calculate_size(nested_calc);
-    uint32_t nested_size = nested_calc.get_size();
-
-    // Use the base implementation with the calculated nested_size
-    add_message_field_force(field_id_size, nested_size);
-  }
-
-  /**
-   * @brief Calculates and adds the sizes of all messages in a repeated field to the total message size
-   *
-   * This helper processes a vector of message objects, calculating the size for each message
-   * and adding it to the total size.
-   *
-   * @tparam MessageType The type of the nested messages in the vector
-   * @param messages Vector of message objects
-   */
-  template<typename MessageType>
-  inline void add_repeated_message(uint32_t field_id_size, const std::vector<MessageType> &messages) {
-    // Skip if the vector is empty
-    if (!messages.empty()) {
-      // Use the force version for all messages in the repeated field
-      for (const auto &message : messages) {
-        add_message_object_force(field_id_size, message);
-      }
-    }
-  }
-
-  /**
-   * @brief Calculates and adds the sizes of all messages in a repeated field to the total message size (FixedVector
-   * version)
-   *
-   * @tparam MessageType The type of the nested messages in the FixedVector
-   * @param messages FixedVector of message objects
-   */
-  template<typename MessageType>
-  inline void add_repeated_message(uint32_t field_id_size, const FixedVector<MessageType> &messages) {
-    // Skip if the fixed vector is empty
-    if (!messages.empty()) {
-      // Use the force version for all messages in the repeated field
-      for (const auto &message : messages) {
-        add_message_object_force(field_id_size, message);
-      }
-    }
-  }
-
-  /**
-   * @brief Calculate size of a packed repeated sint32 field
-   */
-  inline void add_packed_sint32(uint32_t field_id_size, const std::vector<int32_t> &values) {
-    if (values.empty())
-      return;
-
-    size_t packed_size = 0;
-    for (int value : values) {
-      packed_size += varint(encode_zigzag32(value));
-    }
-
-    // field_id + length varint + packed data
-    total_size_ += field_id_size + varint(static_cast<uint32_t>(packed_size)) + static_cast<uint32_t>(packed_size);
+  static constexpr uint32_t calc_message_force(uint32_t field_id_size, uint32_t nested_size) {
+    return field_id_size + varint(nested_size) + nested_size;
   }
 };
 
 // Implementation of methods that depend on ProtoSize being fully defined
 
-inline uint32_t ProtoMessage::calculated_size() const {
-  ProtoSize size;
-  this->calculate_size(size);
-  return size.get_size();
-}
-
 // Implementation of encode_packed_sint32 - must be after ProtoSize is defined
 inline void ProtoWriteBuffer::encode_packed_sint32(uint32_t field_id, const std::vector<int32_t> &values) {
   if (values.empty())
@@ -949,31 +685,30 @@ inline void ProtoWriteBuffer::encode_packed_sint32(uint32_t field_id, const std:
   }
 }
 
-// Implementation of encode_message - must be after ProtoMessage is defined
-inline void ProtoWriteBuffer::encode_message(uint32_t field_id, const ProtoMessage &value, bool force) {
-  // Calculate the message size first
-  ProtoSize msg_size;
-  value.calculate_size(msg_size);
-  uint32_t msg_length_bytes = msg_size.get_size();
+// Encode thunk — converts void* back to concrete type for direct encode() call
+template<typename T> void proto_encode_msg(const void *msg, ProtoWriteBuffer &buf) {
+  static_cast<const T *>(msg)->encode(buf);
+}
 
-  // Skip empty singular messages (matches add_message_field which skips when nested_size == 0)
-  // Repeated messages (force=true) are always encoded since an empty item is meaningful
+// Implementation of encode_message - must be after ProtoMessage is defined
+template<typename T> inline void ProtoWriteBuffer::encode_message(uint32_t field_id, const T &value, bool force) {
+  this->encode_message(field_id, value.calculate_size(), &value, &proto_encode_msg<T>, force);
+}
+
+// Non-template core for encode_message
+inline void ProtoWriteBuffer::encode_message(uint32_t field_id, uint32_t msg_length_bytes, const void *value,
+                                             void (*encode_fn)(const void *, ProtoWriteBuffer &), bool force) {
   if (msg_length_bytes == 0 && !force)
     return;
-
-  this->encode_field_raw(field_id, 2);  // type 2: Length-delimited message
-
-  // Write the length varint directly through pos_
+  this->encode_field_raw(field_id, 2);
   this->encode_varint_raw(msg_length_bytes);
-
-  // Encode nested message - pos_ advances directly through the reference
 #ifdef ESPHOME_DEBUG_API
   uint8_t *start = this->pos_;
-  value.encode(*this);
+  encode_fn(value, *this);
   if (static_cast<uint32_t>(this->pos_ - start) != msg_length_bytes)
     this->debug_check_encode_size_(field_id, msg_length_bytes, this->pos_ - start);
 #else
-  value.encode(*this);
+  encode_fn(value, *this);
 #endif
 }
 
@@ -993,14 +728,6 @@ class ProtoService {
   virtual void on_no_setup_connection() = 0;
   virtual bool send_buffer(ProtoWriteBuffer buffer, uint8_t message_type) = 0;
   virtual void read_message(uint32_t msg_size, uint32_t msg_type, const uint8_t *msg_data) = 0;
-  /**
-   * Send a protobuf message by calculating its size, allocating a buffer, encoding, and sending.
-   * This is the implementation method - callers should use send_message() which adds logging.
-   * @param msg The protobuf message to send.
-   * @param message_type The message type identifier.
-   * @return True if the message was sent successfully, false otherwise.
-   */
-  virtual bool send_message_impl(const ProtoMessage &msg, uint8_t message_type) = 0;
 
   // Authentication helper methods
   inline bool check_connection_setup_() {

esphome/components/bluetooth_proxy/bluetooth_connection.cpp

@@ -183,10 +183,7 @@ void BluetoothConnection::send_service_for_discovery_() {
   static constexpr size_t MAX_PACKET_SIZE = 1360;
 
   // Keep running total of actual message size
-  size_t current_size = 0;
-  api::ProtoSize size;
-  resp.calculate_size(size);
-  current_size = size.get_size();
+  size_t current_size = resp.calculate_size();
 
   while (this->send_service_ < this->service_count_) {
     esp_gattc_service_elem_t service_result;
@@ -302,9 +299,7 @@ void BluetoothConnection::send_service_for_discovery_() {
     }  // end if (total_char_count > 0)
 
     // Calculate the actual size of just this service
-    api::ProtoSize service_sizer;
-    service_resp.calculate_size(service_sizer);
-    size_t service_size = service_sizer.get_size() + 1;  // +1 for field tag
+    size_t service_size = service_resp.calculate_size() + 1;  // +1 for field tag
 
     // Check if adding this service would exceed the limit
     if (current_size + service_size > MAX_PACKET_SIZE) {
@@ -333,7 +328,7 @@ void BluetoothConnection::send_service_for_discovery_() {
   }
 
   // Send the message with dynamically batched services
-  api_conn->send_message(resp, api::BluetoothGATTGetServicesResponse::MESSAGE_TYPE);
+  api_conn->send_message(resp);
 }
 
 void BluetoothConnection::log_connection_error_(const char *operation, esp_gatt_status_t status) {
@@ -422,7 +417,7 @@ bool BluetoothConnection::gattc_event_handler(esp_gattc_cb_event_t event, esp_ga
       resp.address = this->address_;
       resp.handle = param->read.handle;
       resp.set_data(param->read.value, param->read.value_len);
-      api_connection->send_message(resp, api::BluetoothGATTReadResponse::MESSAGE_TYPE);
+      api_connection->send_message(resp);
       break;
     }
     case ESP_GATTC_WRITE_CHAR_EVT:
@@ -438,7 +433,7 @@ bool BluetoothConnection::gattc_event_handler(esp_gattc_cb_event_t event, esp_ga
       api::BluetoothGATTWriteResponse resp;
       resp.address = this->address_;
       resp.handle = param->write.handle;
-      api_connection->send_message(resp, api::BluetoothGATTWriteResponse::MESSAGE_TYPE);
+      api_connection->send_message(resp);
       break;
     }
     case ESP_GATTC_UNREG_FOR_NOTIFY_EVT: {
@@ -454,7 +449,7 @@ bool BluetoothConnection::gattc_event_handler(esp_gattc_cb_event_t event, esp_ga
       api::BluetoothGATTNotifyResponse resp;
       resp.address = this->address_;
       resp.handle = param->unreg_for_notify.handle;
-      api_connection->send_message(resp, api::BluetoothGATTNotifyResponse::MESSAGE_TYPE);
+      api_connection->send_message(resp);
       break;
     }
     case ESP_GATTC_REG_FOR_NOTIFY_EVT: {
@@ -470,7 +465,7 @@ bool BluetoothConnection::gattc_event_handler(esp_gattc_cb_event_t event, esp_ga
       api::BluetoothGATTNotifyResponse resp;
       resp.address = this->address_;
       resp.handle = param->reg_for_notify.handle;
-      api_connection->send_message(resp, api::BluetoothGATTNotifyResponse::MESSAGE_TYPE);
+      api_connection->send_message(resp);
       break;
     }
     case ESP_GATTC_NOTIFY_EVT: {
@@ -483,7 +478,7 @@ bool BluetoothConnection::gattc_event_handler(esp_gattc_cb_event_t event, esp_ga
       resp.address = this->address_;
       resp.handle = param->notify.handle;
       resp.set_data(param->notify.value, param->notify.value_len);
-      api_connection->send_message(resp, api::BluetoothGATTNotifyDataResponse::MESSAGE_TYPE);
+      api_connection->send_message(resp);
       break;
     }
     default:

esphome/components/bluetooth_proxy/bluetooth_proxy.cpp

@@ -44,7 +44,7 @@ void BluetoothProxy::send_bluetooth_scanner_state_(esp32_ble_tracker::ScannerSta
   resp.configured_mode = this->configured_scan_active_
                              ? api::enums::BluetoothScannerMode::BLUETOOTH_SCANNER_MODE_ACTIVE
                              : api::enums::BluetoothScannerMode::BLUETOOTH_SCANNER_MODE_PASSIVE;
-  this->api_connection_->send_message(resp, api::BluetoothScannerStateResponse::MESSAGE_TYPE);
+  this->api_connection_->send_message(resp);
 }
 
 void BluetoothProxy::log_connection_request_ignored_(BluetoothConnection *connection, espbt::ClientState state) {
@@ -112,7 +112,7 @@ void BluetoothProxy::flush_pending_advertisements() {
     return;
 
   // Send the message
-  this->api_connection_->send_message(this->response_, api::BluetoothLERawAdvertisementsResponse::MESSAGE_TYPE);
+  this->api_connection_->send_message(this->response_);
 
   ESP_LOGV(TAG, "Sent batch of %u BLE advertisements", this->response_.advertisements_len);
 
@@ -269,7 +269,7 @@ void BluetoothProxy::bluetooth_device_request(const api::BluetoothDeviceRequest
       call.success = ret == ESP_OK;
       call.error = ret;
 
-      this->api_connection_->send_message(call, api::BluetoothDeviceClearCacheResponse::MESSAGE_TYPE);
+      this->api_connection_->send_message(call);
 
       break;
     }
@@ -389,7 +389,7 @@ void BluetoothProxy::send_device_connection(uint64_t address, bool connected, ui
   call.connected = connected;
   call.mtu = mtu;
   call.error = error;
-  this->api_connection_->send_message(call, api::BluetoothDeviceConnectionResponse::MESSAGE_TYPE);
+  this->api_connection_->send_message(call);
 }
 void BluetoothProxy::send_connections_free() {
   if (this->api_connection_ != nullptr) {
@@ -398,7 +398,7 @@ void BluetoothProxy::send_connections_free() {
 }
 
 void BluetoothProxy::send_connections_free(api::APIConnection *api_connection) {
-  api_connection->send_message(this->connections_free_response_, api::BluetoothConnectionsFreeResponse::MESSAGE_TYPE);
+  api_connection->send_message(this->connections_free_response_);
 }
 
 void BluetoothProxy::send_gatt_services_done(uint64_t address) {
@@ -406,7 +406,7 @@ void BluetoothProxy::send_gatt_services_done(uint64_t address) {
     return;
   api::BluetoothGATTGetServicesDoneResponse call;
   call.address = address;
-  this->api_connection_->send_message(call, api::BluetoothGATTGetServicesDoneResponse::MESSAGE_TYPE);
+  this->api_connection_->send_message(call);
 }
 
 void BluetoothProxy::send_gatt_error(uint64_t address, uint16_t handle, esp_err_t error) {
@@ -416,7 +416,7 @@ void BluetoothProxy::send_gatt_error(uint64_t address, uint16_t handle, esp_err_
   call.address = address;
   call.handle = handle;
   call.error = error;
-  this->api_connection_->send_message(call, api::BluetoothGATTWriteResponse::MESSAGE_TYPE);
+  this->api_connection_->send_message(call);
 }
 
 void BluetoothProxy::send_device_pairing(uint64_t address, bool paired, esp_err_t error) {
@@ -427,7 +427,7 @@ void BluetoothProxy::send_device_pairing(uint64_t address, bool paired, esp_err_
   call.paired = paired;
   call.error = error;
 
-  this->api_connection_->send_message(call, api::BluetoothDevicePairingResponse::MESSAGE_TYPE);
+  this->api_connection_->send_message(call);
 }
 
 void BluetoothProxy::send_device_unpairing(uint64_t address, bool success, esp_err_t error) {
@@ -438,7 +438,7 @@ void BluetoothProxy::send_device_unpairing(uint64_t address, bool success, esp_e
   call.success = success;
   call.error = error;
 
-  this->api_connection_->send_message(call, api::BluetoothDeviceUnpairingResponse::MESSAGE_TYPE);
+  this->api_connection_->send_message(call);
 }
 
 void BluetoothProxy::bluetooth_scanner_set_mode(bool active) {

esphome/components/voice_assistant/voice_assistant.cpp

@@ -251,8 +251,7 @@ void VoiceAssistant::loop() {
       }
 #endif
 
-      if (this->api_client_ == nullptr ||
-          !this->api_client_->send_message(msg, api::VoiceAssistantRequest::MESSAGE_TYPE)) {
+      if (this->api_client_ == nullptr || !this->api_client_->send_message(msg)) {
         ESP_LOGW(TAG, "Could not request start");
         this->error_trigger_.trigger("not-connected", "Could not request start");
         this->continuous_ = false;
@@ -275,7 +274,7 @@ void VoiceAssistant::loop() {
           api::VoiceAssistantAudio msg;
           msg.data = this->send_buffer_;
           msg.data_len = read_bytes;
-          this->api_client_->send_message(msg, api::VoiceAssistantAudio::MESSAGE_TYPE);
+          this->api_client_->send_message(msg);
         } else {
           if (!this->udp_socket_running_) {
             if (!this->start_udp_socket_()) {
@@ -354,7 +353,7 @@ void VoiceAssistant::loop() {
 
           api::VoiceAssistantAnnounceFinished msg;
           msg.success = true;
-          this->api_client_->send_message(msg, api::VoiceAssistantAnnounceFinished::MESSAGE_TYPE);
+          this->api_client_->send_message(msg);
           break;
         }
       }
@@ -612,7 +611,7 @@ void VoiceAssistant::signal_stop_() {
   ESP_LOGD(TAG, "Signaling stop");
   api::VoiceAssistantRequest msg;
   msg.start = false;
-  this->api_client_->send_message(msg, api::VoiceAssistantRequest::MESSAGE_TYPE);
+  this->api_client_->send_message(msg);
 }
 
 void VoiceAssistant::start_playback_timeout_() {
@@ -622,7 +621,7 @@ void VoiceAssistant::start_playback_timeout_() {
 
     api::VoiceAssistantAnnounceFinished msg;
     msg.success = true;
-    this->api_client_->send_message(msg, api::VoiceAssistantAnnounceFinished::MESSAGE_TYPE);
+    this->api_client_->send_message(msg);
   });
 }
 

esphome/components/zwave_proxy/zwave_proxy.cpp

@@ -119,7 +119,7 @@ void ZWaveProxy::process_uart_() {
           // If this is a data frame, use frame length indicator + 2 (for SoF + checksum), else assume 1 for ACK/NAK/CAN
           this->outgoing_proto_msg_.data_len = this->buffer_[0] == ZWAVE_FRAME_TYPE_START ? this->buffer_[1] + 2 : 1;
         }
-        this->api_connection_->send_message(this->outgoing_proto_msg_, api::ZWaveProxyFrame::MESSAGE_TYPE);
+        this->api_connection_->send_message(this->outgoing_proto_msg_);
       }
     }
   }
@@ -209,7 +209,7 @@ void ZWaveProxy::send_homeid_changed_msg_(api::APIConnection *conn) {
   msg.data_len = this->home_id_.size();
   if (conn != nullptr) {
     // Send to specific connection
-    conn->send_message(msg, api::ZWaveProxyRequest::MESSAGE_TYPE);
+    conn->send_message(msg);
   } else if (api::global_api_server != nullptr) {
     // We could add code to manage a second subscription type, but, since this message is
     //  very infrequent and small, we simply send it to all clients
@@ -346,7 +346,7 @@ void ZWaveProxy::parse_start_(uint8_t byte) {
     this->buffer_[0] = byte;
     this->outgoing_proto_msg_.data = this->buffer_.data();
     this->outgoing_proto_msg_.data_len = 1;
-    this->api_connection_->send_message(this->outgoing_proto_msg_, api::ZWaveProxyFrame::MESSAGE_TYPE);
+    this->api_connection_->send_message(this->outgoing_proto_msg_);
   }
 }
 

script/api_protobuf/api_protobuf.py

@@ -270,18 +270,21 @@ class TypeInfo(ABC):
     def _get_simple_size_calculation(
         self, name: str, force: bool, base_method: str, value_expr: str = None
     ) -> str:
-        """Helper for simple size calculations.
+        """Helper for simple size calculations using static ProtoSize methods.
 
         Args:
             name: Field name
             force: Whether this is for a repeated field
-            base_method: Base method name (e.g., "add_int32")
+            base_method: Base method name (e.g., "int32")
             value_expr: Optional value expression (defaults to name)
         """
         field_id_size = self.calculate_field_id_size()
-        method = f"{base_method}_force" if force else base_method
+        method = f"calc_{base_method}_force" if force else f"calc_{base_method}"
+        # calc_bool_force only takes field_id_size (no value needed - bool is always 1 byte)
+        if base_method == "bool" and force:
+            return f"size += ProtoSize::{method}({field_id_size});"
         value = value_expr or name
-        return f"size.{method}({field_id_size}, {value});"
+        return f"size += ProtoSize::{method}({field_id_size}, {value});"
 
     @abstractmethod
     def get_size_calculation(self, name: str, force: bool = False) -> str:
@@ -410,7 +413,7 @@ class DoubleType(TypeInfo):
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
         field_id_size = self.calculate_field_id_size()
-        return f"size.add_double({field_id_size}, {name});"
+        return f"size += ProtoSize::calc_fixed64({field_id_size}, {name});"
 
     def get_fixed_size_bytes(self) -> int:
         return 8
@@ -434,7 +437,7 @@ class FloatType(TypeInfo):
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
         field_id_size = self.calculate_field_id_size()
-        return f"size.add_float({field_id_size}, {name});"
+        return f"size += ProtoSize::calc_float({field_id_size}, {name});"
 
     def get_fixed_size_bytes(self) -> int:
         return 4
@@ -457,7 +460,7 @@ class Int64Type(TypeInfo):
         return o
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return self._get_simple_size_calculation(name, force, "add_int64")
+        return self._get_simple_size_calculation(name, force, "int64")
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 3  # field ID + 3 bytes typical varint
@@ -477,7 +480,7 @@ class UInt64Type(TypeInfo):
         return o
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return self._get_simple_size_calculation(name, force, "add_uint64")
+        return self._get_simple_size_calculation(name, force, "uint64")
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 3  # field ID + 3 bytes typical varint
@@ -497,7 +500,7 @@ class Int32Type(TypeInfo):
         return o
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return self._get_simple_size_calculation(name, force, "add_int32")
+        return self._get_simple_size_calculation(name, force, "int32")
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 3  # field ID + 3 bytes typical varint
@@ -518,7 +521,7 @@ class Fixed64Type(TypeInfo):
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
         field_id_size = self.calculate_field_id_size()
-        return f"size.add_fixed64({field_id_size}, {name});"
+        return f"size += ProtoSize::calc_fixed64({field_id_size}, {name});"
 
     def get_fixed_size_bytes(self) -> int:
         return 8
@@ -542,7 +545,7 @@ class Fixed32Type(TypeInfo):
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
         field_id_size = self.calculate_field_id_size()
-        return f"size.add_fixed32({field_id_size}, {name});"
+        return f"size += ProtoSize::calc_fixed32({field_id_size}, {name});"
 
     def get_fixed_size_bytes(self) -> int:
         return 4
@@ -563,7 +566,7 @@ class BoolType(TypeInfo):
         return f"out.append(YESNO({name}));"
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return self._get_simple_size_calculation(name, force, "add_bool")
+        return self._get_simple_size_calculation(name, force, "bool")
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 1  # field ID + 1 byte
@@ -647,18 +650,18 @@ class StringType(TypeInfo):
     def get_size_calculation(self, name: str, force: bool = False) -> str:
         # For SOURCE_CLIENT only messages, use the string field directly
         if not self._needs_encode:
-            return self._get_simple_size_calculation(name, force, "add_length")
+            return self._get_simple_size_calculation(name, force, "length")
 
         # Check if this is being called from a repeated field context
         # In that case, 'name' will be 'it' and we need to use the repeated version
         if name == "it":
-            # For repeated fields, we need to use add_length_force which includes field ID
+            # For repeated fields, we need to use length_force which includes field ID
             field_id_size = self.calculate_field_id_size()
-            return f"size.add_length_force({field_id_size}, it.size());"
+            return f"size += ProtoSize::calc_length_force({field_id_size}, it.size());"
 
         # For messages that need encoding, use the StringRef size
         field_id_size = self.calculate_field_id_size()
-        return f"size.add_length({field_id_size}, this->{self.field_name}_ref_.size());"
+        return f"size += ProtoSize::calc_length({field_id_size}, this->{self.field_name}_ref_.size());"
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 8  # field ID + 8 bytes typical string
@@ -721,7 +724,9 @@ class MessageType(TypeInfo):
         return o
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return self._get_simple_size_calculation(name, force, "add_message_object")
+        field_id_size = self.calculate_field_id_size()
+        method = "calc_message_force" if force else "calc_message"
+        return f"size += ProtoSize::{method}({field_id_size}, {name}.calculate_size());"
 
     def get_estimated_size(self) -> int:
         # For message types, we can't easily estimate the submessage size without
@@ -822,7 +827,7 @@ class BytesType(TypeInfo):
         )
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return f"size.add_length({self.calculate_field_id_size()}, this->{self.field_name}_len_);"
+        return f"size += ProtoSize::calc_length({self.calculate_field_id_size()}, this->{self.field_name}_len_);"
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 8  # field ID + 8 bytes typical bytes
@@ -897,7 +902,7 @@ class PointerToBytesBufferType(PointerToBufferTypeBase):
         )
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return f"size.add_length({self.calculate_field_id_size()}, this->{self.field_name}_len);"
+        return f"size += ProtoSize::calc_length({self.calculate_field_id_size()}, this->{self.field_name}_len);"
 
 
 class PointerToStringBufferType(PointerToBufferTypeBase):
@@ -939,7 +944,7 @@ class PointerToStringBufferType(PointerToBufferTypeBase):
         return f'dump_field(out, "{self.name}", this->{self.field_name});'
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return f"size.add_length({self.calculate_field_id_size()}, this->{self.field_name}.size());"
+        return f"size += ProtoSize::calc_length({self.calculate_field_id_size()}, this->{self.field_name}.size());"
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 8  # field ID + 8 bytes typical string
@@ -1103,9 +1108,9 @@ class FixedArrayBytesType(TypeInfo):
 
         if force:
             # For repeated fields, always calculate size (no zero check)
-            return f"size.add_length_force({field_id_size}, {length_field});"
-        # For non-repeated fields, add_length already checks for zero
-        return f"size.add_length({field_id_size}, {length_field});"
+            return f"size += ProtoSize::calc_length_force({field_id_size}, {length_field});"
+        # For non-repeated fields, length already checks for zero
+        return f"size += ProtoSize::calc_length({field_id_size}, {length_field});"
 
     def get_estimated_size(self) -> int:
         # Estimate based on typical BLE advertisement size
@@ -1132,7 +1137,7 @@ class UInt32Type(TypeInfo):
         return o
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return self._get_simple_size_calculation(name, force, "add_uint32")
+        return self._get_simple_size_calculation(name, force, "uint32")
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 3  # field ID + 3 bytes typical varint
@@ -1168,7 +1173,7 @@ class EnumType(TypeInfo):
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
         return self._get_simple_size_calculation(
-            name, force, "add_uint32", f"static_cast<uint32_t>({name})"
+            name, force, "uint32", f"static_cast<uint32_t>({name})"
         )
 
     def get_estimated_size(self) -> int:
@@ -1190,7 +1195,7 @@ class SFixed32Type(TypeInfo):
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
         field_id_size = self.calculate_field_id_size()
-        return f"size.add_sfixed32({field_id_size}, {name});"
+        return f"size += ProtoSize::calc_sfixed32({field_id_size}, {name});"
 
     def get_fixed_size_bytes(self) -> int:
         return 4
@@ -1214,7 +1219,7 @@ class SFixed64Type(TypeInfo):
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
         field_id_size = self.calculate_field_id_size()
-        return f"size.add_sfixed64({field_id_size}, {name});"
+        return f"size += ProtoSize::calc_sfixed64({field_id_size}, {name});"
 
     def get_fixed_size_bytes(self) -> int:
         return 8
@@ -1237,7 +1242,7 @@ class SInt32Type(TypeInfo):
         return o
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return self._get_simple_size_calculation(name, force, "add_sint32")
+        return self._get_simple_size_calculation(name, force, "sint32")
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 3  # field ID + 3 bytes typical varint
@@ -1257,7 +1262,7 @@ class SInt64Type(TypeInfo):
         return o
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        return self._get_simple_size_calculation(name, force, "add_sint64")
+        return self._get_simple_size_calculation(name, force, "sint64")
 
     def get_estimated_size(self) -> int:
         return self.calculate_field_id_size() + 3  # field ID + 3 bytes typical varint
@@ -1694,11 +1699,17 @@ class RepeatedTypeInfo(TypeInfo):
         # For repeated fields, we always need to pass force=True to the underlying type's calculation
         # This is because the encode method always sets force=true for repeated fields
 
-        # Handle message types separately as they use a dedicated helper
+        # Handle message types separately - generate inline loop
         if isinstance(self._ti, MessageType):
             field_id_size = self._ti.calculate_field_id_size()
-            container = f"*{name}" if self._use_pointer else name
-            return f"size.add_repeated_message({field_id_size}, {container});"
+            container_ref = f"*{name}" if self._use_pointer else name
+            empty_check = f"{name}->empty()" if self._use_pointer else f"{name}.empty()"
+            o = f"if (!{empty_check}) {{\n"
+            o += f"  for (const auto &it : {container_ref}) {{\n"
+            o += f"    size += ProtoSize::calc_message_force({field_id_size}, it.calculate_size());\n"
+            o += "  }\n"
+            o += "}"
+            return o
 
         # For non-message types, generate size calculation with iteration
         container_ref = f"*{name}" if self._use_pointer else name
@@ -1713,14 +1724,14 @@ class RepeatedTypeInfo(TypeInfo):
             field_id_size = self._ti.calculate_field_id_size()
             bytes_per_element = field_id_size + num_bytes
             size_expr = f"{name}->size()" if self._use_pointer else f"{name}.size()"
-            o += f"  size.add_precalculated_size({size_expr} * {bytes_per_element});\n"
+            o += f"  size += {size_expr} * {bytes_per_element};\n"
         else:
             # Other types need the actual value
             # Special handling for const char* elements
             if self._use_pointer and "const char" in self._container_no_template:
                 field_id_size = self.calculate_field_id_size()
                 o += f"  for (const char *it : {container_ref}) {{\n"
-                o += f"    size.add_length_force({field_id_size}, strlen(it));\n"
+                o += f"    size += ProtoSize::calc_length_force({field_id_size}, strlen(it));\n"
             else:
                 auto_ref = "" if self._ti_is_bool else "&"
                 o += f"  for (const auto {auto_ref}it : {container_ref}) {{\n"
@@ -2233,23 +2244,19 @@ def build_message_type(
             o += indent("\n".join(encode)) + "\n"
             o += "}\n"
         cpp += o
-        prot = "void encode(ProtoWriteBuffer &buffer) const override;"
+        prot = "void encode(ProtoWriteBuffer &buffer) const;"
         public_content.append(prot)
     # If no fields to encode or message doesn't need encoding, the default implementation in ProtoMessage will be used
 
     # Add calculate_size method only if this message needs encoding and has fields
     if needs_encode and size_calc:
-        o = f"void {desc.name}::calculate_size(ProtoSize &size) const {{"
-        # For a single field, just inline it for simplicity
-        if len(size_calc) == 1 and len(size_calc[0]) + len(o) + 3 < 120:
-            o += f" {size_calc[0]} }}\n"
-        else:
-            # For multiple fields
-            o += "\n"
-            o += indent("\n".join(size_calc)) + "\n"
-            o += "}\n"
+        o = f"uint32_t {desc.name}::calculate_size() const {{\n"
+        o += "  uint32_t size = 0;\n"
+        o += indent("\n".join(size_calc)) + "\n"
+        o += "  return size;\n"
+        o += "}\n"
         cpp += o
-        prot = "void calculate_size(ProtoSize &size) const override;"
+        prot = "uint32_t calculate_size() const;"
         public_content.append(prot)
     # If no fields to calculate size for or message doesn't need encoding, the default implementation in ProtoMessage will be used
 
@@ -2933,14 +2940,8 @@ static const char *const TAG = "api.service";
     hpp += " public:\n"
     hpp += "#endif\n\n"
 
-    # Add non-template send_message method
-    hpp += "  bool send_message(const ProtoMessage &msg, uint8_t message_type) {\n"
-    hpp += "#ifdef HAS_PROTO_MESSAGE_DUMP\n"
-    hpp += "    DumpBuffer dump_buf;\n"
-    hpp += "    this->log_send_message_(msg.message_name(), msg.dump_to(dump_buf));\n"
-    hpp += "#endif\n"
-    hpp += "    return this->send_message_impl(msg, message_type);\n"
-    hpp += "  }\n\n"
+    # send_message is now a template on APIConnection directly
+    # No non-template send_message method needed here
 
     # Add logging helper method implementations to cpp
     cpp += "#ifdef HAS_PROTO_MESSAGE_DUMP\n"