Dynamic VRAM streaming crashes all generations with HostBuffer.read_file_slice failed → CUDA OOM (regression after Aug 3 2026 update) (CORE-398)

### Mod Note:

_This is a Cuda error and has been reported to NVIDIA_

_To workaround, please start comfy with --cuda-device 0 (or a higher number) to restrict comfy to a single GPU or use --disable-pinned-memory for multi GPU functionality_

_Please start from https://github.com/Comfy-Org/ComfyUI/issues/15255#issuecomment-5202173878 for the latest._

original report
--------------------------------------------------------------

### Custom Node Testing

- [ ] 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

Dynamic VRAM streaming should work as it did prior to today's update, or fail gracefully without crashing the whole queue.

### Actual Behavior

Environment:

ComfyUI version: 0.30.1
comfy-aimdo version: 0.4.11
comfy-kitchen version: 0.2.26
PyTorch: 2.10.0+cu130
OS: Windows (ComfyUI Desktop)
GPUs: RTX 5060 Ti (16GB, primary) + RTX 3060 (12GB, secondary)
Driver: NVIDIA 610.88, CUDA UMD 13.3

Summary:
After updating ComfyUI Desktop today (Aug 3, 2026), every generation — regardless of model (tested with Krea 2) — fails immediately during sampling with a host buffer read failure that cascades into a CUDA OOM error. This worked correctly before today's update.

Steps to reproduce:

Launch ComfyUI Desktop (dynamic VRAM enabled by default — log shows DynamicVRAM support detected and enabled)
Run any generation (tested: Krea 2 text-to-image)
Sampler starts, model loads and stages into VRAM normally
Crashes ~immediately with:
[ERROR] !!! Exception during processing !!! CUDA error: out of memory
...
File "...\comfy\ops.py", line 228, in cast_modules_with_vbar
handle_pin(s, pin, xfer_source, xfer_dest, subset=subset, size=dest_size)
...
File "...\comfy_aimdo\host_buffer.py", line 109, in read_file_slice
raise RuntimeError("HostBuffer.read_file_slice failed")
RuntimeError: HostBuffer.read_file_slice failed

During handling of the above exception, another exception occurred:
...
File "...\comfy\model_management.py", line 2005, in synchronize
torch.cuda.synchronize()
torch.AcceleratorError: CUDA error: out of memory

Notes:

nvidia-smi confirms this is not a real memory shortage — GPU 0 shows only ~2GB used out of 16.3GB before launch, 14+ GB free.
The crash is not model-size dependent — small and large models both fail identically.
Workaround confirmed: launching with --disable-dynamic-vram fixes it completely; all generations succeed normally with this flag.
This strongly points to a regression in comfy-aimdo's host-buffer/dynamic-VRAM-streaming layer introduced in today's update, since disabling that specific subsystem resolves the issue entirely.

### Steps to Reproduce

Image generation in official Comfyui Krea2 turbo / z-image turbo workflows

### Debug Logs

```powershell
File "D:\ComfyUI\standalone-env\Lib\threading.py", line 995, in run
self._target(*self._args, **self._kwargs)
~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "D:\ComfyUI\ComfyUI\main.py", line 372, in prompt_worker
e.execute(item[2], prompt_id, extra_data, item[4])
~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "D:\ComfyUI\ComfyUI\execution.py", line 728, in execute
asyncio.run(self.execute_async(prompt, prompt_id, extra_data, execute_outputs))
~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "D:\ComfyUI\standalone-env\Lib\asyncio\runners.py", line 195, in run
return runner.run(main)
~~~~~~~~~~^^^^^^
File "D:\ComfyUI\standalone-env\Lib\asyncio\runners.py", line 118, in run
return self._loop.run_until_complete(task)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "D:\ComfyUI\standalone-env\Lib\asyncio\base_events.py", line 725, in run_until_complete
return future.result()
~~~~~~~~~~~~~^^
File "D:\ComfyUI\ComfyUI\execution.py", line 789, in execute_async
result, error, ex = await execute(self.server, dynamic_prompt, self.caches, node_id, extra_data, executed, prompt_id, execution_list, pending_subgraph_results, pending_async_nodes, ui_node_outputs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "D:\ComfyUI\ComfyUI\execution.py", line 645, in execute
comfy.model_management.unload_all_models()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "D:\ComfyUI\ComfyUI\comfy\model_management.py", line 2027, in unload_all_models
free_memory(1e30, device)
~~~~~~~~~~~^^^^^^^^^^^^^^
File "D:\ComfyUI\ComfyUI\comfy\model_management.py", line 875, in free_memory
memory_to_free = 0 if device is None else memory_required - get_free_memory(device)
~~~~~~~~~~~~~~~^^^^^^^^
File "D:\ComfyUI\ComfyUI\comfy\model_management.py", line 1747, in get_free_memory
mem_free_cuda, _ = torch.cuda.mem_get_info(dev)
~~~~~~~~~~~~~~~~~~~~~~~^^^^^
File "D:\ComfyUI\ComfyUI\.venv\Lib\site-packages\torch\cuda\memory.py", line 897, in mem_get_info
return torch.cuda.cudart().cudaMemGetInfo(device)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
torch.AcceleratorError: CUDA error: out of memory
Search for `cudaErrorMemoryAllocation' in https://docs.nvidia.com/cuda/cuda-runtime-api/group__CUDART__TYPES.html for more information.
CUDA kernel errors might be asynchronously reported at some other API call, so the stacktrace below might be incorrect.
For debugging consider passing CUDA_LAUNCH_BLOCKING=1
Compile with `TORCH_USE_CUDA_DSA` to enable device-side assertions.

[INFO] FETCH ComfyRegistry Data [DONE]
[INFO] [ComfyUI-Manager] default cache updated: https://api.comfy.org/nodes
FETCH DATA from: D:\ComfyUI\ComfyUI\user\__manager\cache\1514988643_custom-node-list.json [DONE]
[INFO] [ComfyUI-Manager] All startup tasks have been completed.
```

### Other

_No response_