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[Models] Step-3.5-Flash#33523

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youkaichao merged 34 commits intovllm-project:mainfrom
stepfun-ai:step3p5-vllm-pr-base-main
Feb 2, 2026
Merged

[Models] Step-3.5-Flash#33523
youkaichao merged 34 commits intovllm-project:mainfrom
stepfun-ai:step3p5-vllm-pr-base-main

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@csy0225 csy0225 commented Feb 1, 2026 •
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Purpose

Step-3.5-Flash model support.

Test Plan

Test Result

Essential Elements of an Effective PR Description Checklist
  • The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
  • The test plan, such as providing test command.
  • The test results, such as pasting the results comparison before and after, or e2e results
  • (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
  • (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

csy0225 and others added 30 commits February 2, 2026 06:44
@csy0225
step3p5-turbo-support
f9af118
@csy0225
fix: resove diff from 014
4c60890
@csy0225
fix: fp8 activation should support swigluoai_step
28eecba
@csy0225
format: fix review comments for step3p5, remove groupwise-quant code
17494c7
@csy0225
feat: add step3p5_tool_parser
9b0cbdb
@csy0225
fix: attn module import error
3268d78
@csy0225
feat: support mtp3
b020ee2
@csy0225
fix: FlashInferExperts.apply() got an unexpected keyword argument 'ac…
b247624 
…tivation_limit'
@csy0225
fix: step3p5 reasoning parser error
45eeaf8
@csy0225
Revert "feat: support mtp3"
f911ab0
@csy0225
revert routed_scaling_factor passthrough in fused moe
ede83c9
@csy0225
refactor: revert activation_limit for swiglustep
03c65f8
@csy0225
fix step3p5 reasoning parser
952026e
@csy0225
fix: fix comments about swiglustep, default limit=7.0
285a3ab
@csy0225
format: remove useless field in step3p5 config
864602c
@csy0225
format: simplified rope scaling params update
5389b7d
@csy0225
fix: mtp
459448f
@csy0225
format: fix config.json default value
a5ab370
@csy0225
format: pre-commit tool fix
4086e80
@csy0225
fix: remove moe_dynamic_exp_p from config
67ced2d
@csy0225
fix: mtp3 weights load error
9fded69
@csy0225
format: some review comments fix
0689253
@jeejeelee @csy0225
Refactor moe
b2b55de 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
@jeejeelee @csy0225
fix shared moe
128c8c7 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
@jeejeelee @csy0225
NIT
d66b2de 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
@jeejeelee @csy0225
NIT
82631af 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
@csy0225
feat: keep router logits in fp32 precision
f35951b
@jeejeelee @csy0225
gate
2faeea8 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
@jeejeelee @csy0225
Fix MTP
5147782 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
@jeejeelee @csy0225
triton act
1c4d28c 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
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github-actions bot commented Feb 1, 2026

👋 Hi! Thank you for contributing to the vLLM project.

💬 Join our developer Slack at https://slack.vllm.ai to discuss your PR in #pr-reviews, coordinate on features in #feat- channels, or join special interest groups in #sig- channels.

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dosubot bot commented Feb 1, 2026

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mergify bot commented Feb 1, 2026

Documentation preview: https://vllm--33523.org.readthedocs.build/en/33523/

@mergify mergify bot added documentation Improvements or additions to documentation new-model Requests to new models labels Feb 1, 2026
gemini-code-assist[bot]
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Code Review

This pull request introduces support for the Step-3.5-Flash model, including its core implementation, a new Triton kernel for the swiglustep activation, and associated configurations, tests, and parsers for reasoning and tool use. The changes are well-structured and align with the existing architecture of the project. I have one minor suggestion to improve code clarity.

@jeejeelee jeejeelee added the ready ONLY add when PR is ready to merge/full CI is needed label Feb 1, 2026
jeejeelee
jeejeelee approved these changes Feb 2, 2026
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Thank you for contribution

@youkaichao youkaichao merged commit c3b40dc into vllm-project:main Feb 2, 2026
54 of 56 checks passed
khluu pushed a commit that referenced this pull request Feb 2, 2026
@csy0225 @jeejeelee @khluu
[Models] Step-3.5-Flash (#33523)
8b45c58 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
Co-authored-by: i-zhangmingming <i-zhangmingming@stepfun.com>
Co-authored-by: xiewuxun <xiewuxun@stepfun.com>
Co-authored-by: zetaohong <i-hongzetao@stepfun.com>
Co-authored-by: Jee Jee Li <pandaleefree@gmail.com>
(cherry picked from commit c3b40dc)
PiratePai pushed a commit to PiratePai/epd_shm that referenced this pull request Feb 3, 2026
@csy0225 @jeejeelee @PiratePai
[Models] Step-3.5-Flash (vllm-project#33523)
9df6f73 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
Co-authored-by: i-zhangmingming <i-zhangmingming@stepfun.com>
Co-authored-by: xiewuxun <xiewuxun@stepfun.com>
Co-authored-by: zetaohong <i-hongzetao@stepfun.com>
Co-authored-by: Jee Jee Li <pandaleefree@gmail.com>
Signed-off-by: Pai <416932041@qq.com>
ItzDEXX pushed a commit to ItzDEXX/vllm that referenced this pull request Feb 19, 2026
@csy0225 @jeejeelee @ItzDEXX
[Models] Step-3.5-Flash (vllm-project#33523)
324a984 
Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
Co-authored-by: i-zhangmingming <i-zhangmingming@stepfun.com>
Co-authored-by: xiewuxun <xiewuxun@stepfun.com>
Co-authored-by: zetaohong <i-hongzetao@stepfun.com>
Co-authored-by: Jee Jee Li <pandaleefree@gmail.com>
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@jeejeelee jeejeelee jeejeelee approved these changes

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@csy0225 @jeejeelee @youkaichao