Ace-Step-1.5-ScragVAE

### Custom Node Testing

- [x] I have tried disabling custom nodes and the issue persists (see [how to disable custom nodes](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled) if you need help)

### Expected Behavior

Ace-Step-1.5-ScragVAE not working

### Actual Behavior

### Steps to Reproduce

### Debug Logs

```powershell
Output will be ignored
WARNING: No VAE weights detected, VAE not initalized.
!!! Exception during processing !!! ERROR: VAE is invalid: None

If the VAE is from a checkpoint loader node your checkpoint does not contain a valid VAE.
Traceback (most recent call last):
File "D:\ComfyUI_2026.04.21\ComfyUI\execution.py", line 534, in execute
output_data, output_ui, has_subgraph, has_pending_tasks = await get_output_data(prompt_id, unique_id, obj, input_data_all, execution_block_cb=execution_block_cb, pre_execute_cb=pre_execute_cb, v3_data=v3_data)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "D:\ComfyUI_2026.04.21\ComfyUI\execution.py", line 334, in get_output_data
return_values = await _async_map_node_over_list(prompt_id, unique_id, obj, input_data_all, obj.FUNCTION, allow_interrupt=True, execution_block_cb=execution_block_cb, pre_execute_cb=pre_execute_cb, v3_data=v3_data)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "D:\ComfyUI_2026.04.21\ComfyUI\execution.py", line 308, in _async_map_node_over_list
await process_inputs(input_dict, i)
File "D:\ComfyUI_2026.04.21\ComfyUI\execution.py", line 296, in process_inputs
result = f(**inputs)
File "D:\ComfyUI_2026.04.21\ComfyUI\nodes.py", line 831, in load_vae
vae.throw_exception_if_invalid()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "D:\ComfyUI_2026.04.21\ComfyUI\comfy\sd.py", line 869, in throw_exception_if_invalid
raise RuntimeError("ERROR: VAE is invalid: None\n\nIf the VAE is from a checkpoint loader node your checkpoint does not contain a valid VAE.")
RuntimeError: ERROR: VAE is invalid: None

If the VAE is from a checkpoint loader node your checkpoint does not contain a valid VAE.
```

### Other

_No response_

Start by reproducing the failure with the Ace-Step-1.5-ScragVAE workflow and review the debug path through nodes.py at load_vae and comfy/sd.py at throw_exception_if_invalid. Check the missing VAE-weights condition shown in the logs; done means the workflow loads a valid VAE without raising the reported error.

Written by the indexing model from the issue text.