diff --git a/esphome/components/api/api_frame_helper.h b/esphome/components/api/api_frame_helper.h
index f93b086186..a582307738 100644
--- a/esphome/components/api/api_frame_helper.h
+++ b/esphome/components/api/api_frame_helper.h
@@ -163,9 +163,10 @@ class APIFrameHelper {
   }
   // Write a single protobuf message - the hot path (87-100% of all writes)
   virtual APIError write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) = 0;
-  // Write multiple protobuf messages in a single batched operation
-  // messages contains (message_type, offset, length) for each message in the buffer
-  // The buffer contains all messages with appropriate padding before each
+  // Write multiple protobuf messages in a single batched operation.
+  // messages must not be empty — caller is responsible for checking.
+  // messages contains (message_type, offset, length) for each message in the buffer.
+  // The buffer contains all messages with appropriate padding before each.
   virtual APIError write_protobuf_messages(ProtoWriteBuffer buffer, std::span<const MessageInfo> messages) = 0;
   // Get the frame header padding required by this protocol
   uint8_t frame_header_padding() const { return frame_header_padding_; }
diff --git a/esphome/components/api/api_frame_helper_noise.cpp b/esphome/components/api/api_frame_helper_noise.cpp
index 429f6fde1f..d6b4a72cae 100644
--- a/esphome/components/api/api_frame_helper_noise.cpp
+++ b/esphome/components/api/api_frame_helper_noise.cpp
@@ -511,10 +511,9 @@ APIError APINoiseFrameHelper::write_protobuf_messages(ProtoWriteBuffer buffer, s
   APIError aerr = this->check_data_state_();
   if (aerr != APIError::OK)
     return aerr;
-
-  if (messages.empty()) {
-    return APIError::OK;
-  }
+#ifdef ESPHOME_DEBUG_API
+  assert(!messages.empty());
+#endif
 
   uint8_t *buffer_data = buffer.get_buffer()->data();
   StaticVector<struct iovec, MAX_MESSAGES_PER_BATCH> iovs;
diff --git a/esphome/components/api/api_frame_helper_plaintext.cpp b/esphome/components/api/api_frame_helper_plaintext.cpp
index 6e33f68154..a21d177b7f 100644
--- a/esphome/components/api/api_frame_helper_plaintext.cpp
+++ b/esphome/components/api/api_frame_helper_plaintext.cpp
@@ -302,10 +302,9 @@ APIError APIPlaintextFrameHelper::write_protobuf_messages(ProtoWriteBuffer buffe
   APIError aerr = this->check_data_state_();
   if (aerr != APIError::OK)
     return aerr;
-
-  if (messages.empty()) {
-    return APIError::OK;
-  }
+#ifdef ESPHOME_DEBUG_API
+  assert(!messages.empty());
+#endif
 
   uint8_t *buffer_data = buffer.get_buffer()->data();
   StaticVector<struct iovec, MAX_MESSAGES_PER_BATCH> iovs;