diff --git a/backend/src/backend/scripts.py b/backend/src/backend/scripts.py
index da047f0..c7545b4 100644
--- a/backend/src/backend/scripts.py
+++ b/backend/src/backend/scripts.py
@@ -424,14 +424,21 @@ async def create_script_record(
     workspace_id = context.workspace.workspace_id
     content_hash = hashlib.sha256(content).hexdigest()
     size_bytes = len(content)
-    if parent_ulid:
-        try:
-            await runtime_client.ensure_directory(workspace_id, f"{user_id}/{parent_ulid}")
-        except RuntimeClientError as exc:
-            raise HTTPException(
-                status_code=exc.status_code,
-                detail=exc.detail,
-            ) from exc
+    # Jupyter Contents API PUT does not create intermediate directories.
+    # Make sure the user's own subfolder exists at the Jupyter level before
+    # we try to write into it; on nested creates, also ensure the parent
+    # directory under it. ensure_directory is idempotent (GET-first pattern).
+    try:
+        await runtime_client.ensure_directory(workspace_id, user_id)
+        if parent_ulid:
+            await runtime_client.ensure_directory(
+                workspace_id, f"{user_id}/{parent_ulid}"
+            )
+    except RuntimeClientError as exc:
+        raise HTTPException(
+            status_code=exc.status_code,
+            detail=exc.detail,
+        ) from exc
 
     try:
         if script_type == "notebook":
@@ -826,14 +833,21 @@ async def create_workspace_directory(
     runtime_client = request.app.state.runtime_client
     workspace_id = context.workspace.workspace_id
 
-    if parent_ulid:
-        try:
-            await runtime_client.ensure_directory(workspace_id, f"{user_id}/{parent_ulid}")
-        except RuntimeClientError as exc:
-            raise HTTPException(
-                status_code=exc.status_code,
-                detail=exc.detail,
-            ) from exc
+    # Jupyter Contents API PUT does not create intermediate directories.
+    # Make sure the user's own subfolder exists at the Jupyter level before
+    # we try to write into it; on nested creates, also ensure the parent
+    # directory under it. ensure_directory is idempotent (GET-first pattern).
+    try:
+        await runtime_client.ensure_directory(workspace_id, user_id)
+        if parent_ulid:
+            await runtime_client.ensure_directory(
+                workspace_id, f"{user_id}/{parent_ulid}"
+            )
+    except RuntimeClientError as exc:
+        raise HTTPException(
+            status_code=exc.status_code,
+            detail=exc.detail,
+        ) from exc
 
     try:
         await runtime_client.create_directory(workspace_id, name=jupyter_path)