diff --git a/autogpt_platform/backend/backend/blocks/io.py b/autogpt_platform/backend/backend/blocks/io.py
index 256dd2777a..8b40c61fc8 100644
--- a/autogpt_platform/backend/backend/blocks/io.py
+++ b/autogpt_platform/backend/backend/blocks/io.py
@@ -470,10 +470,10 @@ class AgentFileInputBlock(AgentInputBlock):
             return
 
         # Determine return format based on user preference
-        # for_block_output: returns workspace:// if available, else data URI
+        # for_external_api: always returns data URI (base64) - honors "Produce Base64 Output"
         # for_local_processing: returns local file path
         return_format = (
-            "for_block_output" if input_data.base_64 else "for_local_processing"
+            "for_external_api" if input_data.base_64 else "for_local_processing"
         )
 
         yield "result", await store_media_file(