vllm-sr 0.2.0.dev20260313094400

vLLM Semantic Router - Intelligent routing for Mixture-of-Models

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

# Start the router (includes dashboard and first-run setup)
HF_TOKEN=hf_xxx vllm-sr serve

# Start an isolated second local stack on offset host ports
VLLM_SR_STACK_NAME=lane-b VLLM_SR_PORT_OFFSET=200 HF_TOKEN=hf_xxx vllm-sr serve

# Open the dashboard
# http://localhost:8700
# second stack example: http://localhost:8900

# Optional: open the dashboard in your 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

If you start in an empty directory, vllm-sr serve bootstraps a minimal workspace and opens the dashboard in setup mode. Configure your first model there, then activate routing.

Local dashboard state is persisted under .vllm-sr/dashboard-data/ and bind-mounted into the container at /app/data. User accounts, evaluation history, and ML pipeline artifacts survive vllm-sr stop followed by a new vllm-sr serve as long as that workspace directory is kept.

To run parallel local stacks from the same machine or multiple worktrees, set VLLM_SR_STACK_NAME and VLLM_SR_PORT_OFFSET before vllm-sr serve, vllm-sr status, vllm-sr dashboard, and vllm-sr stop. The stack name isolates container and network names, and the port offset shifts the published host ports while keeping internal container ports unchanged.

Advanced YAML-first setup

# Generate an advanced sample config if you prefer editing YAML directly
vllm-sr init

# Validate the sample before serving
vllm-sr validate config.yaml

vllm-sr init is optional. It generates a lean advanced sample plus .vllm-sr/router-defaults.yaml for users who want to hand-author routing config. router-defaults.yaml contains advanced runtime defaults; it is not required for first-run dashboard setup.

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)
Jaeger UI	16686	Distributed tracing UI
Grafana (embedded)	8700	Dashboards at /embedded/grafana
Prometheus UI	9090	Metrics storage and querying

*Default port, configurable via listeners in config.yaml

Observability

vllm-sr serve automatically starts the observability stack:

• Jaeger: Distributed tracing embedded at http://localhost:8700/embedded/jaeger (also available directly at http://localhost:16686)
• Grafana: Pre-configured dashboards embedded at http://localhost:8700/embedded/grafana
• Prometheus: Metrics collection at http://localhost:9090

Note: Grafana is optimized for embedded access through the dashboard. For the best experience, use http://localhost:8700/embedded/grafana where anonymous authentication is pre-configured.

Tracing is enabled by default. Traces are visible in Jaeger under the vllm-sr service name.

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

2. jailbreak - Block adversarial prompts:

plugins:
  - type: "jailbreak"
    configuration:
      enabled: true
      threshold: 0.8  # Optional: detection sensitivity 0.0-1.0

3. 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

4. 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)

5. 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"

6. 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"

7. 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:

# Generate an advanced YAML sample if you want to edit config directly
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