dec04ec8d8
## Summary
- Fix incorrect layer count calculation for MTP (Multi-Token Prediction)
models in `update_aclgraph_sizes()` function
- For MTP models, the draft model's layer count is stored in
`num_nextn_predict_layers` or `mtp_num_hidden_layers` (for Qwen3.5), not
in the standard `num_hidden_layers` field
- Directly accessing `draft.hf_config.num_hidden_layers` returns the
main model's layer count instead of the MTP draft model's layer count
## Bug Description
In `vllm_ascend/utils.py`, the `update_aclgraph_sizes()` function
calculates `resources_per_graph` for speculative decoding scenarios.
When calculating the resources needed for the draft model, the original
code directly accessed:
```python
resources_per_graph += draft.hf_config.num_hidden_layers + 1
```
This works correctly for standard draft models, but **fails for MTP
models** (like DeepSeek-V3's MTP or Qwen3.5's MTP) because:
1. MTP models store their layer count in model-specific fields:
- `num_nextn_predict_layers` (DeepSeek-V3 MTP)
- `mtp_num_hidden_layers` (Qwen3.5 MTP)
2. The `num_hidden_layers` field in these models contains the **main
model's** layer count, not the MTP layer count
3. This leads to **grossly overestimating** the `resources_per_graph`,
which in turn causes the calculated `max_batch_sizes` to be
unnecessarily small
## Fix
Use `draft.get_total_num_hidden_layers()` instead of directly accessing
`draft.hf_config.num_hidden_layers`. This method correctly handles
different model types through the `model_arch_config_convertor`
infrastructure, returning the appropriate layer count for:
- Standard draft models → `num_hidden_layers`
- DeepSeek-V3 MTP → `num_nextn_predict_layers`
- Qwen3.5 MTP → `mtp_num_hidden_layers`
🤖 Generated with [Claude Code](https://claude.com/claude-code)
- vLLM version: v0.16.0
- vLLM main:
4034c3d32e
Signed-off-by: wanghuanjun2113 <wanghuanjun2113@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
vLLM Ascend Plugin
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Latest News 🔥
- [2026/02] We released the new official version v0.13.0! Please follow the official guide to start using vLLM Ascend Plugin on Ascend.
- [2025/12] We released the new official version v0.11.0! Please follow the official guide to start using vLLM Ascend Plugin on Ascend.
- [2025/09] We released the new official version v0.9.1! Please follow the official guide to start deploying large-scale Expert Parallelism (EP) on Ascend.
- [2025/08] We hosted the vLLM Beijing Meetup with vLLM and Tencent! Please find the meetup slides here.
- [2025/06] User stories page is now live! It kicks off with LLaMA-Factory/verl/TRL/GPUStack to demonstrate how vLLM Ascend assists Ascend users in enhancing their experience across fine-tuning, evaluation, reinforcement learning (RL), and deployment scenarios.
- [2025/06] Contributors page is now live! All contributions deserve to be recorded, thanks for all contributors.
- [2025/05] We've released the first official version v0.7.3! We collaborated with the vLLM community to publish a blog post sharing our practice: Introducing vLLM Hardware Plugin, Best Practice from Ascend NPU.
- [2025/03] We hosted the vLLM Beijing Meetup with vLLM team! Please find the meetup slides here.
- [2025/02] vLLM community officially created vllm-project/vllm-ascend repo for running vLLM seamlessly on the Ascend NPU.
- [2024/12] We are working with the vLLM community to support [RFC]: Hardware pluggable.
Overview
vLLM Ascend (vllm-ascend) is a community maintained hardware plugin for running vLLM seamlessly on the Ascend NPU.
It is the recommended approach for supporting the Ascend backend within the vLLM community. It adheres to the principles outlined in the [RFC]: Hardware pluggable, providing a hardware-pluggable interface that decouples the integration of the Ascend NPU with vLLM.
By using vLLM Ascend plugin, popular open-source models, including Transformer-like, Mixture-of-Experts (MoE), Embedding, Multi-modal LLMs can run seamlessly on the Ascend NPU.
Prerequisites
- Hardware: Atlas 800I A2 Inference series, Atlas A2 Training series, Atlas 800I A3 Inference series, Atlas A3 Training series, Atlas 300I Duo (Experimental)
- OS: Linux
- Software:
- Python >= 3.10, < 3.12
- CANN == 8.5.0 (Ascend HDK version refers to here)
- PyTorch == 2.9.0, torch-npu == 2.9.0
- vLLM (the same version as vllm-ascend)
Getting Started
Please use the following recommended versions to get started quickly:
| Version | Release type | Doc |
|---|---|---|
| v0.14.0rc1 | Latest release candidate | See QuickStart and Installation for more details |
| v0.13.0 | Latest stable version | See QuickStart and Installation for more details |
Contributing
See CONTRIBUTING for more details, which is a step-by-step guide to help you set up the development environment, build and test.
We welcome and value any contributions and collaborations:
- Please let us know if you encounter a bug by filing an issue
- Please use User forum for usage questions and help.
Branch
vllm-ascend has a main branch and a dev branch.
- main: main branch, corresponds to the vLLM main branch, and is continuously monitored for quality through Ascend CI.
- releases/vX.Y.Z: development branch, created alongside new releases of vLLM. For example,
releases/v0.13.0is the dev branch for vLLMv0.13.0version.
Below are the maintained branches:
| Branch | Status | Note |
|---|---|---|
| main | Maintained | CI commitment for vLLM main branch and vLLM v0.13.0 tag |
| v0.7.1-dev | Unmaintained | Only doc fixes are allowed |
| v0.7.3-dev | Maintained | CI commitment for vLLM 0.7.3 version, only bug fixes are allowed, and no new release tags anymore. |
| v0.9.1-dev | Maintained | CI commitment for vLLM 0.9.1 version |
| v0.11.0-dev | Maintained | CI commitment for vLLM 0.11.0 version |
| releases/v0.13.0 | Maintained | CI commitment for vLLM 0.13.0 version |
| rfc/feature-name | Maintained | Feature branches for collaboration |
Please refer to Versioning policy for more details.
Weekly Meeting
- vLLM Ascend Weekly Meeting: https://tinyurl.com/vllm-ascend-meeting
- Wednesday, 15:00 - 16:00 (UTC+8, Convert to your timezone)
License
Apache License 2.0, as found in the LICENSE file.