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Pre-release

This release is a pre-release and may not be stable for production use.

vLLM Semantic Router

Intelligent Router for Mixture-of-Models (MoM).

GitHub: https://github.com/vllm-project/semantic-router

Quick Start

Installation

# Install from PyPI
pip install vllm-sr

# Or install from source (development)
cd src/vllm-sr
pip install -e .

Usage

# Initialize vLLM Semantic Router Configuration
vllm-sr init

# Start the router (includes dashboard)
vllm-sr serve

# Open dashboard in browser
vllm-sr dashboard

# View logs
vllm-sr logs router
vllm-sr logs envoy
vllm-sr logs dashboard

# Check status
vllm-sr status

# Stop
vllm-sr stop

Features

  • Router: Intelligent request routing based on intent classification
  • Envoy Proxy: High-performance proxy with ext_proc integration
  • Dashboard: Web UI for monitoring and testing (http://localhost:8700)
  • Metrics: Prometheus metrics endpoint (http://localhost:9190/metrics)

Endpoints

After running vllm-sr serve, the following endpoints are available:

Endpoint Port Description
Dashboard 8700 Web UI for monitoring and Playground
API 8888* Chat completions API (configurable in config.yaml)
Metrics 9190 Prometheus metrics
gRPC 50051 Router gRPC (internal)

*Default port, configurable via listeners in config.yaml

Configuration

Plugin Configuration

The CLI supports configuring plugins in your routing decisions. Plugins are per-decision behaviors that customize request handling (security, caching, customization, debugging).

Supported Plugin Types:

  • semantic-cache - Cache similar requests for performance
  • jailbreak - Detect and block adversarial prompts
  • pii - Detect and enforce PII policies
  • system_prompt - Inject custom system prompts
  • header_mutation - Add/modify HTTP headers
  • hallucination - Detect hallucinations in responses
  • router_replay - Record routing decisions for debugging

Plugin Examples:

  1. semantic-cache - Cache similar requests:
plugins:
  - type: "semantic-cache"
    configuration:
      enabled: true
      similarity_threshold: 0.92  # 0.0-1.0, higher = more strict
      ttl_seconds: 3600  # Optional: cache TTL in seconds
  1. jailbreak - Block adversarial prompts:
plugins:
  - type: "jailbreak"
    configuration:
      enabled: true
      threshold: 0.8  # Optional: detection sensitivity 0.0-1.0
  1. pii - Enforce PII policies:
plugins:
  - type: "pii"
    configuration:
      enabled: true
      threshold: 0.7  # Optional: detection sensitivity 0.0-1.0
      pii_types_allowed: ["EMAIL_ADDRESS"]  # Optional: list of allowed PII types
  1. system_prompt - Inject custom instructions:
plugins:
  - type: "system_prompt"
    configuration:
      enabled: true
      system_prompt: "You are a helpful assistant."
      mode: "replace"  # "replace" (default) or "insert" (prepend)
  1. header_mutation - Modify HTTP headers:
plugins:
  - type: "header_mutation"
    configuration:
      add:
        - name: "X-Custom-Header"
          value: "custom-value"
      update:
        - name: "User-Agent"
          value: "SemanticRouter/1.0"
      delete:
        - "X-Old-Header"
  1. hallucination - Detect hallucinations:
plugins:
  - type: "hallucination"
    configuration:
      enabled: true
      use_nli: false  # Optional: use NLI for detailed analysis
      hallucination_action: "header"  # "header", "body", or "none"
  1. router_replay - Record decisions for debugging:
plugins:
  - type: "router_replay"
    configuration:
      enabled: true
      max_records: 200  # Optional: max records in memory (default: 200)
      capture_request_body: false  # Optional: capture request payloads (default: false)
      capture_response_body: false  # Optional: capture response payloads (default: false)
      max_body_bytes: 4096  # Optional: max bytes to capture (default: 4096)

Validation Rules:

  • Plugin Type: Must be one of: semantic-cache, jailbreak, pii, system_prompt, header_mutation, hallucination, router_replay
  • enabled: Must be a boolean (required for most plugins)
  • threshold/similarity_threshold: Must be a float between 0.0 and 1.0
  • max_records/max_body_bytes: Must be a positive integer
  • ttl_seconds: Must be a non-negative integer
  • pii_types_allowed: Must be a list of strings (if provided)
  • system_prompt: Must be a string (if provided)
  • mode: Must be "replace" or "insert" (if provided)

CLI Commands:

# Initialize config with plugin examples
vllm-sr init

# Validate configuration (including plugins)
vllm-sr validate config.yaml

# Generate router config with plugins
vllm-sr config router --config config.yaml

File Descriptor Limits

The CLI automatically sets file descriptor limits to 65,536 for Envoy proxy. To customize:

export VLLM_SR_NOFILE_LIMIT=100000  # Optional (min: 8192)
vllm-sr serve

License

Apache 2.0

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