No active session at get currentSessionId when run "Classify" again

[ibelem]

Since the following two PRs have been merged and available in https://www.npmjs.com/package/onnxruntime-web/v/1.22.0-dev.20250306-ccf8fdd9ea , I tried to build latest Transformers.js dist based on 1.22.0-dev.20250306-ccf8fdd9ea to verify #69 .

• [WebNN] Fixes MLTensor caching across different contexts onnxruntime#23100 Fixes MLTensor caching across different contexts - Merged
• [WebNN EP] Automatically move input CPU tensors to ml-tensor onnxruntime#23073 Automatically move input CPU tensors to ml-tensor - Merged

Tried the ibelem/transformers.js@6cb6a4d and ibelem@a4fc70f to use ORT Web 1.22.0-dev.20250306-ccf8fdd9ea and Transformers.js 3.4.0 , but the no active session at get currentSessionId error occurs in the demo.

Repro Steps:

1. Enable WebNN on Chrome Canary
2. Visit Image Classification demo https://ibelem.github.io/webnn-developer-preview/demos/image-classification/?provider=webnn&devicetype=gpu&model=mobilenet-v2&run=1
3. Click Classify button

Actual Result

PASS

Repro Steps: (cont.)

4. Click Classify button again

Actual Result

Uncaught (in promise) Error: No active session at get currentSessionId ( at dn.ensureTensor

This issue is also reproducible when switching to another models and clicking Classify button after step 3.

Enrico Galli (@egalli) Could you please help to investigate this issue, or please let me know if I missed somthing. Thank you!

[egalli]

This seems to be caused when a WebNN EP session and a WebGPU EP session are created concurrently.

It seems that transformers.js uses a WebGPU EP session (empty options options) in the ops registry. This registry is used for top_k.
https://github.com/huggingface/transformers.js/blob/5b5e5ed31ec6d268a96004705ab2574b956c531f/src/ops/registry.js#L112-L121

I have started a PR that lets you create a WebNN EP session and a WebGPU sessions. microsoft/onnxruntime#23998

[ibelem]

Enrico Galli (@egalli) Thanks a lot for your quick investigation and PR submission!