fix(backend): address workspace file handling bugs

- Fix data loss on overwrite: defer old file deletion until new file is
  written to storage, preventing data loss if the write fails
- Fix GCS download: move return before cleanup so download success isn't
  lost if client.close() fails
- Fix AgentFileInputBlock: use for_block_output instead of
  for_local_processing so files persist in CoPilot workspace

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

autogpt_platform/backend/backend/blocks/io.py

@@ -471,10 +471,8 @@ class AgentFileInputBlock(AgentInputBlock):
 
         # Determine return format based on user preference
         # for_external_api: always returns data URI (base64) - honors "Produce Base64 Output"
-        # for_local_processing: returns local file path
-        return_format = (
-            "for_external_api" if input_data.base_64 else "for_local_processing"
-        )
+        # for_block_output: smart format - workspace:// in CoPilot, data URI in graphs
+        return_format = "for_external_api" if input_data.base_64 else "for_block_output"
 
         yield "result", await store_media_file(
             file=input_data.value,

autogpt_platform/backend/backend/util/gcs_utils.py

@@ -60,16 +60,21 @@ async def download_with_fresh_session(bucket: str, blob: str) -> bytes:
     session = aiohttp.ClientSession(
         connector=aiohttp.TCPConnector(limit=10, force_close=True)
     )
+    client: async_gcs_storage.Storage | None = None
     try:
         client = async_gcs_storage.Storage(session=session)
         content = await client.download(bucket, blob)
-        await client.close()
         return content
     except Exception as e:
         if "404" in str(e) or "Not Found" in str(e):
             raise FileNotFoundError(f"File not found: gcs://{bucket}/{blob}")
         raise
     finally:
+        if client:
+            try:
+                await client.close()
+            except Exception:
+                pass  # Best-effort cleanup
         await session.close()
 
 

autogpt_platform/backend/backend/util/workspace.py

@@ -196,13 +196,13 @@ class WorkspaceManager:
         # Resolve path with session prefix
         path = self._resolve_path(path)
 
-        # Check if file exists at path
-        existing = await get_workspace_file_by_path(self.workspace_id, path)
-        if existing is not None:
-            if overwrite:
-                # Delete existing file first
-                await self.delete_file(existing.id)
-            else:
+        # Check if file exists at path (only error for non-overwrite case)
+        # For overwrite=True, we let the write proceed and handle via UniqueViolationError
+        # This ensures the new file is written to storage BEFORE the old one is deleted,
+        # preventing data loss if the new write fails
+        if not overwrite:
+            existing = await get_workspace_file_by_path(self.workspace_id, path)
+            if existing is not None:
                 raise ValueError(f"File already exists at path: {path}")
 
         # Auto-detect MIME type if not provided