semantic-router Documentation

Technical Documentation: vllm-project/semantic-router

ℹ️ Provenance: Hybrid Fusion: vllm-project/semantic-router + vllm-project/vllm-project.github.io · CodeWiki Reference · Recency: Active (< 180 days)

1. Project Overview & Quickstart (vllm-project/semantic-router) Copy Chapter

About Copy Chapter

vLLM Semantic Router is a programmable routing layer for building Mixture-of-Models systems across heterogeneous LLM infrastructure. It evaluates request signals, user preferences, and application policies to select—or compose—the right model path for each request.

Use it to improve quality, cost, latency, privacy, and safety without hard-coding routing logic into applications.

Explore how it works →

Getting Started Copy Chapter

Install Copy Section

curl -fsSL https://vllm-sr.ai/install.sh | bash

For platform notes, detailed setup options, and troubleshooting, see the Installation Guide.

Online playground credentials

• Username: [email protected]
• Password: vllm-sr

Latest News Copy Chapter

• [2026/07/21] New Blog: Beyond a Single Model: Building Mixture-of-Models Systems with vLLM Semantic Router
• [2026/06/29] New Blog: Micro-Agent: Beat Frontier Models with Collaboration inside Model API
• [2026/06/16] New Blog: Beyond One Model: Fusion in vLLM Semantic Router
• [2026/06/05] v0.3 Released: vLLM Semantic Router v0.3 Themis: From Signals to Stateful Production Routing

Earlier announcements

• [2026/03/24] Vision Paper Released: The Workload-Router-Pool Architecture for LLM Inference Optimization
• [2026/03/10] v0.2 Released: vLLM Semantic Router v0.2 Athena Release
• [2026/02/27] White Paper Released: Signal Driven Decision Routing for Mixture-of-Modality Models
• [2026/01/05] Iris v0.1 Released: vLLM Semantic Router v0.1 Iris: The First Major Release
• [2025/12/16] Collaboration: AMD × vLLM Semantic Router: Building the System Intelligence Together
• [2025/12/15] New Blog: Token-Level Truth: Real-Time Hallucination Detection for Production LLMs
• [2025/11/19] New Blog: Signal-Decision Driven Architecture: Reshaping Semantic Routing at Scale
• [2025/11/03] Paper Published: Category-Aware Semantic Caching for Heterogeneous LLM Workloads
• [2025/10/27] New Blog: Scaling Semantic Routing with Extensible LoRA
• [2025/10/12] Paper Accepted: When to Reason: Semantic Router for vLLM
• [2025/10/08] Collaboration: vLLM Semantic Router with vLLM Production Stack Team.
• [2025/09/01] Released the project: vLLM Semantic Router: Next Phase in LLM inference.

More announcements are available on the Blog and Publications pages.

Community Copy Chapter

For questions, feedback, or to contribute, please join the #semantic-router channel in vLLM Slack.

Community Meetings Copy Section

We host community meetings on the first and third Tuesday of each month to sync with contributors across different time zones:

• First Tuesday of the month: 9:00-10:00 AM EST (accommodates US EST, EU, and Asia Pacific contributors)
  • Zoom Link
  • Google Calendar Invite
  • ics file
• Third Tuesday of the month: 1:00-2:00 PM EST (accommodates US EST and California contributors)
  • Zoom Link
  • Google Calendar Invite
  • ics file
• Meeting recordings: YouTube

Contributing Copy Chapter

If you want to contribute, start with CONTRIBUTING.md.

For repository-native development workflow and validation commands, use AGENTS.md as the entrypoint and tools/agent/docs/README.md as the canonical index.

Citation Copy Chapter

If you find Semantic Router helpful in your research or projects, please consider citing it:

@misc{semanticrouter2025,
  title={vLLM Semantic Router},
  author={vLLM Semantic Router Team},
  year={2025},
  howpublished={\url{https://github.com/vllm-project/semantic-router}},
}

Sponsors Copy Chapter

We are grateful to our sponsors who support us:

AMD provides us with GPU resources and ROCm™ software for training and researching frontier router models, enhancing E2E testing, and building the online models playground.

2. Official Technical Reference & Guides (vllm-project/vllm-project.github.io) Copy Chapter

vLLM blog source

Local development Copy Chapter

1. Install jekyll and bundler by running gem install jekyll bundler. Ask ChatGPT for help if you encounter any issues.
2. bundle install to install the necessary gems.
3. rm ./Gemfile.lock if you meet gem error.
4. bundle exec jekyll server to compile and start the server.

To add a new blogpost, please refer to _posts/2023-06-20-vllm.md as an example. Some notes:

• Google Doc can be saved as markdown format which will make your life easier.
• Note that the blogpost will only show when its date is in the past.
• Add summary front matter for SEO. Keep it concise, specific, and 240 characters or fewer.
• Put figures under assets/figures/yourblogname/.
• Make a pull request.

The blog is automatically built and deployed by GitHub Actions when main is pushed to.

LaTeX Math Copy Chapter

The blog supports LaTeX math via MathJax.

It can be enabled by adding math: true to the document frontmatter. It has been configured to support the standard LaTeX style math notation, i.e.:

$ inline math $

$$
math block
$$

GitHub Flavored Admonitions Copy Chapter

The blog supports GitHub flavored admonitions via jekyll-gfm-admonition. It supports the following syntax:

> [!NOTE]
> Highlights information that users should take into account, even when skimming.
> And supports multi-line text.

> [!TIP]
> Optional information to help a user be more successful.

> [!IMPORTANT]
> Crucial information necessary for users to succeed.

> [!WARNING]
> Critical content demanding immediate
> user attention due to potential risks.

> [!CAUTION]
> Negative potential consequences of an action.
> Opportunity to provide more context.

Theme customization Copy Chapter

The theme we are using is Minima. If you need to customise anything from this theme, see Overriding theme defaults.

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• Canonical Reference: https://codewiki.google/github.com/vllm-project/semantic-router