diff --git a/libs/core/langchain_core/messages/block_translators/openai.py b/libs/core/langchain_core/messages/block_translators/openai.py
index e99a19cb8dc..ba4fc102fd3 100644
--- a/libs/core/langchain_core/messages/block_translators/openai.py
+++ b/libs/core/langchain_core/messages/block_translators/openai.py
@@ -67,7 +67,7 @@ def convert_to_openai_data_block(
     elif block["type"] == "file":
         if block.get("source_type") == "base64" or "base64" in block:
             # Handle v0 format (Base64CB): {"source_type": "base64", "data": "...", ...}
-            # Handle v1 format (FileCB): {"base64": "...", ...}
+            # Handle v1 format (IDCB): {"base64": "...", ...}
             base64_data = block["data"] if "source_type" in block else block["base64"]
             file = {"file_data": f"data:{block['mime_type']};base64,{base64_data}"}
             if filename := block.get("filename"):
@@ -90,7 +90,7 @@ def convert_to_openai_data_block(
                 formatted_block = {"type": "input_file", **formatted_block["file"]}
         elif block.get("source_type") == "id" or "file_id" in block:
             # Handle v0 format (IDContentBlock): {"source_type": "id", "id": "...", ...}
-            # Handle v1 format (FileCB): {"file_id": "...", ...}
+            # Handle v1 format (IDCB): {"file_id": "...", ...}
             file_id = block["id"] if "source_type" in block else block["file_id"]
             formatted_block = {"type": "file", "file": {"file_id": file_id}}
             if api == "responses":
diff --git a/libs/core/langchain_core/messages/content.py b/libs/core/langchain_core/messages/content.py
index 38e4927eb34..53f2e294d34 100644
--- a/libs/core/langchain_core/messages/content.py
+++ b/libs/core/langchain_core/messages/content.py
@@ -939,7 +939,9 @@ def _get_data_content_block_types() -> tuple[str, ...]:
 
 
 def is_data_content_block(block: dict) -> bool:
-    """Check if the provided content block is a standard v1 data content block.
+    """Check if the provided content block is a data content block.
+
+    Returns for both v0 (old-style) and v1 (new-style) multimodal data blocks.
 
     Args:
         block: The content block to check.
@@ -951,7 +953,9 @@ def is_data_content_block(block: dict) -> bool:
     if block.get("type") not in _get_data_content_block_types():
         return False
 
-    if any(key in block for key in ("url", "base64", "file_id", "text")):
+    if any(key in block for key in ("url", "base64", "file_id")):
+        # Type is valid and at least one data field is present
+        # (Accepts old-style image and audio URLContentBlock)
         return True
 
     # Verify data presence based on source type
@@ -966,6 +970,8 @@ def is_data_content_block(block: dict) -> bool:
         ):
             return True
 
+    # Type may be valid, but no data fields are present
+    # (required case since each is optional and we have no validation)
     return False