Ensuring correct device dispatch after module replacement

[yiliu30]

When loading a model across multiple devices using device_map="auto", the accelerate library attaches hooks to move module inputs to the correct devices automatically.
For certain models (for example, gpt‑oss), we replace the original MoE modules during initialization. However, after this replacement, the newly inserted modules do not have the required Accelerate hooks attached. As a result, input tensors may not be dispatched to the correct devices.
We need to investigate when Accelerate binds these hooks during the model loading process. Based on that, we should re-dispatch (or re-attach hooks to) the replaced modules if necessary to ensure correct multi-device execution.

If needed, we can dispatch the replaced model with dispatch_model:

from accelerate.big_modeling import dispatch_model

[yiliu30]

@wenhuach21 I don’t assign the owner for now. Let’s check whether any community users would like to take it. If not, I can take it on later.