Megatron-Bridge submodule version incompatible with GPT-OSS

[domichen35-bot]

• Following the official GitHub instructions:

  git clone git@github.com:NVIDIA-NeMo/RL.git nemo-rl
  cd nemo-rl
  git submodule update --init --recursive

• The command git submodule update --init --recursive pins Megatron-Bridge to a specific commit, but that version is not compatible with GPT-OSS. The error looks like this:
  

• I tried manually updating Megatron-Bridge to the latest branch, but then I encountered the following error:

ImportError: cannot import name 'MegatronLegacyTokenizer' from 'megatron.core.datasets.megatron_tokenizer'

• Following the error messages and adjusting dependencies still leads to other issues.

• Could you provide a Megatron-Bridge version that supports GPT-OSS, or guidance on how to correctly update the submodule?

[euronymous-aithal]

assigning this to @yaoyu-33