module 'xformers.ops' has no attribute 'memory_efficient_attention'
Author: edisonchanCreated Jun 23, 2026Updated Jun 23, 2026
Bug
Run flux.2 klein workflow bundle with ComfyUI popup error message:
[ERROR] !!! Exception during processing !!! module 'xformers.ops' has no attribute 'memory_efficient_attention'
[ERROR] Traceback (most recent call last):
File "/home/edison/Downloads/ComfyUI/execution.py", line 542, 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 "/home/edison/Downloads/ComfyUI/execution.py", line 341, 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 "/home/edison/Downloads/ComfyUI/execution.py", line 315, in _async_map_node_over_list
await process_inputs(input_dict, i)
File "/home/edison/Downloads/ComfyUI/execution.py", line 303, in process_inputs
result = f(**inputs)
File "/home/edison/Downloads/ComfyUI/nodes.py", line 364, in encode
t = vae.encode(pixels)
File "/home/edison/Downloads/ComfyUI/comfy/sd.py", line 1163, in encode
model_management.raise_non_oom(e)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
File "/home/edison/Downloads/ComfyUI/comfy/model_management.py", line 394, in raise_non_oom
raise e
File "/home/edison/Downloads/ComfyUI/comfy/sd.py", line 1156, in encode
out = self.first_stage_model.encode(pixels_in)
File "/home/edison/Downloads/ComfyUI/comfy/ldm/models/autoencoder.py", line 208, in encode
z = self.encoder(x)
File "/home/edison/Downloads/ComfyUI/.venv/lib/python3.14/site-packages/torch/nn/modules/module.py", line 1778, in _wrapped_call_impl
return self._call_impl(*args, **kwargs)
~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
File "/home/edison/Downloads/ComfyUI/.venv/lib/python3.14/site-packages/torch/nn/modules/module.py", line 1789, in _call_impl
return forward_call(*args, **kwargs)
File "/home/edison/Downloads/ComfyUI/comfy/ldm/modules/diffusionmodules/model.py", line 673, in forward
h = self.mid.attn_1(h)
File "/home/edison/Downloads/ComfyUI/.venv/lib/python3.14/site-packages/torch/nn/modules/module.py", line 1778, in _wrapped_call_impl
return self._call_impl(*args, **kwargs)
~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
File "/home/edison/Downloads/ComfyUI/.venv/lib/python3.14/site-packages/torch/nn/modules/module.py", line 1789, in _call_impl
return forward_call(*args, **kwargs)
File "/home/edison/Downloads/ComfyUI/comfy/ldm/modules/diffusionmodules/model.py", line 374, in forward
h_ = self.optimized_attention(q, k, v)
File "/home/edison/Downloads/ComfyUI/comfy/ldm/modules/diffusionmodules/model.py", line 298, in xformers_attention
out = xformers.ops.memory_efficient_attention(q, k, v, attn_bias=None)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: module 'xformers.ops' has no attribute 'memory_efficient_attention'
Command
To Reproduce
Steps to reproduce the behavior:
cd /home/edison/Downloads/ComfyUI source .venv/bin/activate
cd /home/edison/Downloads/xformers pip install -v --no-build-isolation -U git+https://github.com/facebookresearch/xformers.git@main#egg=xformers
cd /home/edison/Downloads/ComfyUI python main.py --listen --enable-manager
Expected behavior
Environment
Ubuntu 26.04 cuda toolkit 13.3 python 3.14 pytorch 2.12
python -m xformers.info
/home/edison/Downloads/ComfyUI/.venv/lib/python3.14/site-packages/torch/cuda/__init__.py:63: FutureWarning: The pynvml package is deprecated. Please install nvidia-ml-py instead. If you did not install pynvml directly, please report this to the maintainers of the package that installed pynvml for you.
import pynvml # type: ignore[import]
xFormers 0.0.35+42fc265.d20260623
indexing.scaled_index_addF: available
indexing.scaled_index_addB: available
indexing.index_select: available
sp24.sparse24_sparsify_both_ways: available
sp24.sparse24_apply: available
sp24.sparse24_apply_dense_output: available
sp24._sparse24_gemm: available
[email protected]: available
[email protected]: available
is_triton_available: True
pytorch.version: 2.12.1+cu130
pytorch.cuda: available
gpu.compute_capability: 12.0
gpu.name: NVIDIA GeForce RTX 5070
dcgm_profiler: unavailable
build.info: available
build.cuda_version: 1303
build.hip_version: None
build.python_version: 3.14.4
build.torch_version: 2.12.1+cu130
build.env.TORCH_CUDA_ARCH_LIST: None
build.env.PYTORCH_ROCM_ARCH: None
build.env.XFORMERS_BUILD_TYPE: None
build.env.XFORMERS_ENABLE_DEBUG_ASSERTIONS: None
build.env.NVCC_FLAGS: None
build.env.XFORMERS_PACKAGE_FROM: None
build.nvcc_version: 13.3.33
source.privacy: open source
(.venv) edison@u24:~/Downloads/ComfyUI$ pip install nvidia-ml-py
Looking in indexes: https://mirrors.cloud.tencent.com/pypi/simple/
Requirement already satisfied: nvidia-ml-py in ./.venv/lib/python3.14/site-packages (13.610.43)
(.venv) edison@u24:~/Downloads/ComfyUI$ nvidia-smi
Tue Jun 23 23:53:26 2026
+-----------------------------------------------------------------------------------------+
| NVIDIA-SMI 610.43.02 KMD Version: 610.43.02 CUDA UMD Version: 13.3 |
+-----------------------------------------+------------------------+----------------------+
| GPU Name Persistence-M | Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap | Memory-Usage | GPU-Util Compute M. |
| | | MIG M. |
|=========================================+========================+======================|
| 0 NVIDIA GeForce RTX 5070 Off | 00000000:01:00.0 On | N/A |
| 0% 45C P8 4W / 250W | 34MiB / 12227MiB | 0% Default |
| | | N/A |
+-----------------------------------------+------------------------+----------------------+
+-----------------------------------------------------------------------------------------+
| Processes: |
| GPU GI CI PID Type Process name GPU Memory |
| ID ID Usage |
|=========================================================================================|
| No running processes found |
+-----------------------------------------------------------------------------------------+
You can run the script with:
# For security purposes, please check the contents of collect_env.py before running it.
python -m torch.utils.collect_envpython -m torch.utils.collect_env
/home/edison/Downloads/ComfyUI/.venv/lib/python3.14/site-packages/torch/cuda/__init__.py:63: FutureWarning: The pynvml package is deprecated. Please install nvidia-ml-py instead. If you did not install pynvml directly, please report this to the maintainers of the package that installed pynvml for you.
import pynvml # type: ignore[import]
<frozen runpy>:128: RuntimeWarning: 'torch.utils.collect_env' found in sys.modules after import of package 'torch.utils', but prior to execution of 'torch.utils.collect_env'; this may result in unpredictable behaviour
Collecting environment information...
PyTorch version: 2.12.1+cu130
Is debug build: False
CUDA used to build PyTorch: 13.0
ROCM used to build PyTorch: N/A
OS: Ubuntu 26.04 LTS (x86_64)
GCC version: (Ubuntu 13.4.0-10ubuntu1) 13.4.0
Clang version: 20.1.8 (https://github.com/llvm/llvm-project.git 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
CMake version: version 4.2.3
Libc version: glibc-2.43
Python version: 3.14.4 (main, Apr 8 2026, 04:02:31) [GCC 15.2.0] (64-bit runtime)
Python platform: Linux-7.0.0-22-generic-x86_64-with-glibc2.43
Is CUDA available: True
CUDA runtime version: 13.3.33
CUDA_MODULE_LOADING set to:
GPU models and configuration: GPU 0: NVIDIA GeForce RTX 5070
Nvidia driver version: Could not collect
cuDNN version: Probably one of the following:
/usr/lib/x86_64-linux-gnu/libcudnn.so.9.22.0
/usr/lib/x86_64-linux-gnu/libcudnn_adv.so.9.22.0
/usr/lib/x86_64-linux-gnu/libcudnn_cnn.so.9.22.0
/usr/lib/x86_64-linux-gnu/libcudnn_engines_precompiled.so.9.22.0
/usr/lib/x86_64-linux-gnu/libcudnn_engines_runtime_compiled.so.9.22.0
/usr/lib/x86_64-linux-gnu/libcudnn_engines_tensor_ir.so.9.22.0
/usr/lib/x86_64-linux-gnu/libcudnn_ext.so.9.22.0
/usr/lib/x86_64-linux-gnu/libcudnn_graph.so.9.22.0
/usr/lib/x86_64-linux-gnu/libcudnn_heuristic.so.9.22.0
/usr/lib/x86_64-linux-gnu/libcudnn_ops.so.9.22.0
Is XPU available: False
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True
Caching allocator config: N/A
CPU:
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Address sizes: 48 bits physical, 48 bits virtual
Byte Order: Little Endian
CPU(s): 8
On-line CPU(s) list: 0-7
Vendor ID: AuthenticAMD
Model name: AMD Ryzen 7 9850X3D 8-Core Processor
CPU family: 26
Model: 68
Thread(s) per core: 1
Core(s) per socket: 8
Socket(s): 1
Stepping: 0
Frequency boost: enabled
CPU(s) scaling MHz: 50%
CPU max MHz: 5653.6240
CPU min MHz: 613.0440
BogoMIPS: 9399.97
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good amd_lbr_v2 nopl xtopology nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpuid_fault cpb cat_l3 cdp_l3 hw_pstate ssbd mba perfmon_v2 ibrs ibpb stibp ibrs_enhanced vmmcall fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid cqm rdt_a avx512f avx512dq rdseed adx smap avx512ifma clflushopt clwb avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local user_shstk avx_vnni avx512_bf16 clzero irperf xsaveerptr rdpru wbnoinvd cppc arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif x2avic v_spec_ctrl vnmi avx512vbmi umip pku ospke avx512_vbmi2 gfni vaes vpclmulqdq avx512_vnni avx512_bitalg avx512_vpopcntdq rdpid bus_lock_detect movdiri movdir64b overflow_recov succor smca fsrm avx512_vp2intersect flush_l1d amd_lbr_pmc_freeze
Virtualization: AMD-V
L1d cache: 384 KiB (8 instances)
L1i cache: 256 KiB (8 instances)
L2 cache: 8 MiB (8 instances)
L3 cache: 96 MiB (1 instance)
NUMA node(s): 1
NUMA node0 CPU(s): 0-7
Vulnerability Gather data sampling: Not affected
Vulnerability Ghostwrite: Not affected
Vulnerability Indirect target selection: Not affected
Vulnerability Itlb multihit: Not affected
Vulnerability L1tf: Not affected
Vulnerability Mds: Not affected
Vulnerability Meltdown: Not affected
Vulnerability Mmio stale data: Not affected
Vulnerability Old microcode: Not affected
Vulnerability Reg file data sampling: Not affected
Vulnerability Retbleed: Not affected
Vulnerability Spec rstack overflow: Mitigation; IBPB on VMEXIT only
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl
Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2: Mitigation; Enhanced / Automatic IBRS; IBPB conditional; STIBP disabled; PBRSB-eIBRS Not affected; BHI Not affected
Vulnerability Srbds: Not affected
Vulnerability Tsa: Not affected
Vulnerability Tsx async abort: Not affected
Vulnerability Vmscape: Mitigation; IBPB on VMEXIT
Versions of relevant libraries:
[pip3] came-pytorch==0.1.3
[pip3] lion-pytorch==0.2.4
[pip3] numpy==2.4.0
[pip3] nvidia-cublas==13.1.1.3
[pip3] nvidia-cuda-cupti==13.0.85
[pip3] nvidia-cuda-nvrtc==13.0.88
[pip3] nvidia-cuda-runtime==13.0.96
[pip3] nvidia-cudnn-cu13==9.20.0.48
[pip3] nvidia-cufft==12.0.0.61
[pip3] nvidia-curand==10.4.0.35
[pip3] nvidia-cusolver==12.0.4.66
[pip3] nvidia-cusparse==12.6.3.3
[pip3] nvidia-cusparselt-cu13==0.8.1
[pip3] nvidia-nccl-cu13==2.29.7
[pip3] nvidia-nvjitlink==13.0.88
[pip3] nvidia-nvtx==13.0.85
[pip3] onnx==1.22.0
[pip3] onnxruntime==1.27.0
[pip3] onnxruntime-gpu==1.27.0
[pip3] open_clip_torch==3.3.0
[pip3] rotary-embedding-torch==0.9.1
[pip3] torch==2.12.1
[pip3] torchaudio==2.11.0
[pip3] torchsde==0.2.6
[pip3] torchvision==0.27.1
[pip3] triton==3.7.1
[conda] Could not collect
Additional context
Source: facebookresearch/xformers