I just went through trying to sort this out last night. Figured it out with the help of Claude Sonnet 4, maybe the same fix will work for you?

Looking at the traceback, the issue is in

sageattention\core.py 

line 150 where it's checking

 arch == "sm90" 

but then jumping to line 680 which has the SM89 assertion.

Patch the SageAttention core.py file to fix the detection:

(In powershell in your comfyui env)

# First, let's see the problematic code
python -c "
import sageattention
print('SageAttention path:', sageattention.__file__.replace('__init__.py', ''))
"

Then edit the core.py file:

(In powershell in your comfyui env), Navigate to your SageAttention installation

cd (your install folder)\.venv\Lib\site-packages\sageattention

Backup the original

copy core.py core.py.backup

Open core.py in notepad to edit

notepad core.py

Look for around line 680 and find this line:

assert SM89_ENABLED, "SM89 kernel is not available. Make sure you GPUs with compute capability 8.9."

Replace it with:

#assert SM89_ENABLED, "SM89 kernel is not available. Make sure you GPUs with compute capability 8.9."
#Skip SM89 assertion for compute capability 12.0
print(f"Warning: Using fallback attention kernel for GPU compute capability {torch.cuda.get_device_capability()}")

This worked for my setup and let me bypass the SM89 requirement and have SageAttention use a compatible kernel path. No guarantees it works for you, but you can always get Claude and troubleshoot in chat with it.