diff --git a/esphome/components/api/proto.h b/esphome/components/api/proto.h
index 2a77116f5a..a5fd5c67b2 100644
--- a/esphome/components/api/proto.h
+++ b/esphome/components/api/proto.h
@@ -132,15 +132,20 @@ class ProtoVarInt {
   uint64_t value_;
 };
 
-// Forward declaration for decode_to_message
-class ProtoMessage;
-
 class ProtoLengthDelimited {
  public:
   explicit ProtoLengthDelimited(const uint8_t *value, size_t length) : value_(value), length_(length) {}
   std::string as_string() const { return std::string(reinterpret_cast<const char *>(this->value_), this->length_); }
 
-  // Non-template method to decode into an existing message instance
+  /**
+   * Decode the length-delimited data into an existing ProtoMessage instance.
+   *
+   * This method allows decoding without templates, enabling use in contexts
+   * where the message type is not known at compile time. The ProtoMessage's
+   * decode() method will be called with the raw data and length.
+   *
+   * @param msg The ProtoMessage instance to decode into
+   */
   void decode_to_message(ProtoMessage &msg) const;
 
  protected:
diff --git a/script/api_protobuf/api_protobuf.py b/script/api_protobuf/api_protobuf.py
index 8395045b3c..1bb8789904 100755
--- a/script/api_protobuf/api_protobuf.py
+++ b/script/api_protobuf/api_protobuf.py
@@ -540,7 +540,10 @@ class MessageType(TypeInfo):
 
     @property
     def decode_length(self) -> str:
-        # For non-template decoding, we need to handle this differently
+        # Override to return None for message types because we can't use template-based
+        # decoding when the specific message type isn't known at compile time.
+        # Instead, we use the non-template decode_to_message() method which allows
+        # runtime polymorphism through virtual function calls.
         return None
 
     @property