[MODEL] Cherry-pick: Adding Support for Qwen3.5 Models

[ChuanLi1101]

Summary

• Cherry-pick of commit 9562912 from main into amd_dev branch
• Original PR: [MODEL] Adding Support for Qwen3.5 Models #34110
• Adds support for Qwen3.5 and Qwen3.5-MOE models, including MTP (Multi-Token Prediction) speculative decoding

Changes

• New model files: qwen3_5.py, qwen3_5_mtp.py
• Updated model registry, speculative config, and supported models documentation
• 11 files changed, +1501/-9 lines

[mergify]

Documentation preview: https://vllm--37514.org.readthedocs.build/en/37514/

[gemini-code-assist]

Code Review

This pull request introduces support for the Qwen3.5 series of models, including both dense and Mixture-of-Experts (MoE) variants, as well as their Multi-Token Prediction (MTP) counterparts. The changes involve adding new model implementations (qwen3_5.py and qwen3_5_mtp.py), registering them in the model and MTP registries, and updating documentation. Additionally, several configuration accesses in existing Qwen3Next model files were refined to consistently use hf_text_config and include default values for robustness, and speculative decoding support was enabled for Qwen3.5 MTP models while explicitly disabling Mamba with speculative decoding for Qwen3.5 models.

[mergify]

Hi @ChuanLi1101, the pre-commit checks have failed. Please run:

uv pip install pre-commit>=4.5.1
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy failing?

mypy is run differently in CI. If the failure is related to this check, please use the following command to run it locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10

[ChuanLi1101]

Fixed the pre-commit
uff-check import ordering issue in mxfp4.py.
Requesting review from AMD reviewers: @tjtanaa @gshtras