Global Configuration

This guide covers the configuration options for the Semantic Router. The system uses a single YAML configuration file that controls all aspects of routing, classification, and security.

Configuration File

The configuration file is located at config/config.yaml. Here's the structure based on the actual implementation:

# config/config.yaml - Actual configuration structure

# BERT model for semantic similarity
bert_model:
  model_id: sentence-transformers/all-MiniLM-L12-v2
  threshold: 0.6
  use_cpu: true

# Semantic caching
semantic_cache:
  backend_type: "memory"  # Options: "memory" or "milvus"
  enabled: false
  similarity_threshold: 0.8
  max_entries: 1000
  ttl_seconds: 3600
  eviction_policy: "fifo"  # Options: "fifo", "lru", "lfu"

# Tool auto-selection
tools:
  enabled: false
  top_k: 3
  similarity_threshold: 0.2
  tools_db_path: "config/tools_db.json"
  fallback_to_empty: true

# Jailbreak protection
prompt_guard:
  enabled: false
  use_modernbert: true
  model_id: "models/jailbreak_classifier_modernbert-base_model"
  threshold: 0.7
  use_cpu: true

# vLLM endpoints - your backend models
vllm_endpoints:
  - name: "endpoint1"
    address: "your-server.com"  # Replace with your server
    port: 11434
    models:
      - "your-model"           # Replace with your model
    weight: 1

# Model configuration
model_config:
  "your-model":
    pii_policy:
      allow_by_default: true
      pii_types_allowed: ["EMAIL_ADDRESS", "PERSON"]
    preferred_endpoints: ["endpoint1"]

# Classification models
classifier:
  category_model:
    model_id: "models/category_classifier_modernbert-base_model"
    use_modernbert: true
    threshold: 0.6
    use_cpu: true
  pii_model:
    model_id: "models/pii_classifier_modernbert-base_presidio_token_model"
    use_modernbert: true
    threshold: 0.7
    use_cpu: true

# Categories and routing rules
categories:
- name: math
  use_reasoning: true  # Enable reasoning for math
  model_scores:
  - model: your-model
    score: 1.0
- name: computer science
  use_reasoning: true  # Enable reasoning for code
  model_scores:
  - model: your-model
    score: 1.0
- name: other
  use_reasoning: false # No reasoning for general queries
  model_scores:
  - model: your-model
    score: 0.8

default_model: your-model

# Reasoning family configurations - define how different model families handle reasoning syntax
reasoning_families:
  deepseek:
    type: "chat_template_kwargs"
    parameter: "thinking"
  
  qwen3:
    type: "chat_template_kwargs"
    parameter: "enable_thinking"
  
  gpt-oss:
    type: "reasoning_effort"
    parameter: "reasoning_effort"
  
  gpt:
    type: "reasoning_effort"
    parameter: "reasoning_effort"

# Global default reasoning effort level
default_reasoning_effort: "medium"

# Model configurations - assign reasoning families to specific models
model_config:
  # Example: DeepSeek model with custom name
  "ds-v31-custom":
    reasoning_family: "deepseek"  # This model uses DeepSeek reasoning syntax
    preferred_endpoints: ["endpoint1"]
  
  # Example: Qwen3 model with custom name
  "my-qwen3-model":
    reasoning_family: "qwen3"     # This model uses Qwen3 reasoning syntax  
    preferred_endpoints: ["endpoint2"]
  
  # Example: Model without reasoning support
  "phi4":
    # No reasoning_family field - this model doesn't support reasoning mode
    preferred_endpoints: ["endpoint1"]

Key Configuration Sections

Backend Endpoints

Configure your LLM servers:

vllm_endpoints:
  - name: "my_endpoint"
    address: "127.0.0.1"  # Your server IP
    port: 8000                # Your server port
    models:
      - "llama2-7b"          # Model name
    weight: 1                 # Load balancing weight

Model Settings

Configure model-specific settings:

model_config:
  "llama2-7b":
    pii_policy:
      allow_by_default: true    # Allow PII by default
      pii_types_allowed: ["EMAIL_ADDRESS", "PERSON"]
    preferred_endpoints: ["my_endpoint"]

Pricing (Optional)

If you want the router to compute request cost and expose Prometheus cost metrics, add per-1M token pricing and currency under each model in model_config.

model_config:
  phi4:
    pricing:
      currency: USD
      prompt_per_1m: 0.07
      completion_per_1m: 0.35
  "mistral-small3.1":
    pricing:
      currency: USD
      prompt_per_1m: 0.1
      completion_per_1m: 0.3
  gemma3:27b:
    pricing:
      currency: USD
      prompt_per_1m: 0.067
      completion_per_1m: 0.267

• Cost formula: (prompt_tokens * prompt_per_1m + completion_tokens * completion_per_1m) / 1_000_000 (in the given currency).
• When not configured, the router still reports token and latency metrics; cost is treated as 0.

Classification Models

Configure the BERT classification models:

classifier:
  category_model:
    model_id: "models/category_classifier_modernbert-base_model"
    use_modernbert: true
    threshold: 0.6            # Classification confidence threshold
    use_cpu: true             # Use CPU (no GPU required)
  pii_model:
    model_id: "models/pii_classifier_modernbert-base_presidio_token_model"
    threshold: 0.7            # PII detection threshold
    use_cpu: true

Categories and Routing

Define how different query types are handled:

categories:
- name: math
  use_reasoning: true              # Enable reasoning for math problems
  reasoning_description: "Mathematical problems require step-by-step reasoning"
  model_scores:
  - model: your-model
    score: 1.0                     # Preference score for this model

- name: computer science
  use_reasoning: true              # Enable reasoning for code
  model_scores:
  - model: your-model
    score: 1.0

- name: other
  use_reasoning: false             # No reasoning for general queries
  model_scores:
  - model: your-model
    score: 0.8

default_model: your-model          # Fallback model

Model Reasoning Configuration

Configure how different models handle reasoning mode syntax. This allows you to add new models without code changes:

# Model reasoning configurations - define how different models handle reasoning syntax
model_reasoning_configs:
  - name: "deepseek"
    patterns: ["deepseek", "ds-", "ds_", "ds:", "ds "]
    reasoning_syntax:
      type: "chat_template_kwargs"
      parameter: "thinking"

  - name: "qwen3"
    patterns: ["qwen3"]
    reasoning_syntax:
      type: "chat_template_kwargs"
      parameter: "enable_thinking"

  - name: "gpt-oss"
    patterns: ["gpt-oss", "gpt_oss"]
    reasoning_syntax:
      type: "reasoning_effort"
      parameter: "reasoning_effort"

  - name: "gpt"
    patterns: ["gpt"]
    reasoning_syntax:
      type: "reasoning_effort"
      parameter: "reasoning_effort"

# Global default reasoning effort level (when not specified per category)
default_reasoning_effort: "medium"

Model Reasoning Configuration Options

Configuration Structure:

• name: A unique identifier for the model family
• patterns: Array of patterns to match against model names
• reasoning_syntax.type: How the model expects reasoning mode to be specified
  • "chat_template_kwargs": Use chat template parameters (for models like DeepSeek, Qwen3)
  • "reasoning_effort": Use OpenAI-compatible reasoning_effort field (for GPT models)
• reasoning_syntax.parameter: The specific parameter name the model uses

Pattern Matching: The system supports both simple string patterns and regular expressions for flexible model matching:

• Simple string matches: "deepseek" matches any model containing "deepseek"
• Prefix patterns: "ds-" matches models starting with "ds-" or exactly "ds"
• Regular expressions: "^gpt-4.*" matches models starting with "gpt-4"
• Wildcard: "*" matches all models (use for fallback configurations)
• Multiple patterns: ["deepseek", "ds-", "^phi.*"] matches any of these patterns

Regex Pattern Examples:

patterns:
  - "^gpt-4.*"        # Models starting with "gpt-4"
  - ".*-instruct$"    # Models ending with "-instruct"
  - "phi[0-9]+"       # Models like "phi3", "phi4", etc.
  - "^(llama|mistral)" # Models starting with "llama" or "mistral"

Adding New Models: To support a new model family (e.g., Claude), simply add a new configuration:

model_reasoning_configs:
  - name: "claude"
    patterns: ["claude"]
    reasoning_syntax:
      type: "chat_template_kwargs"
      parameter: "enable_reasoning"

Unknown Models: Models that don't match any configured pattern will have no reasoning fields applied when reasoning mode is enabled. This prevents issues with models that don't support reasoning syntax.

Default Reasoning Effort: Set the global default reasoning effort level used when categories don't specify their own effort level:

default_reasoning_effort: "high"  # Options: "low", "medium", "high"

Category-Specific Reasoning Effort: Override the default effort level per category:

categories:
- name: math
  use_reasoning: true
  reasoning_effort: "high"        # Use high effort for complex math
  model_scores:
  - model: your-model
    score: 1.0

- name: general
  use_reasoning: true
  reasoning_effort: "low"         # Use low effort for general queries
  model_scores:
  - model: your-model
    score: 1.0

Security Features

Configure PII detection and jailbreak protection:

# PII Detection
classifier:
  pii_model:
    threshold: 0.7                 # Higher = more strict PII detection

# Jailbreak Protection
prompt_guard:
  enabled: true                    # Enable jailbreak detection
  threshold: 0.7                   # Detection sensitivity
  use_cpu: true                    # Runs on CPU

# Model-level PII policies
model_config:
  "your-model":
    pii_policy:
      allow_by_default: true       # Allow most content
      pii_types_allowed: ["EMAIL_ADDRESS", "PERSON"]  # Specific allowed types

Optional Features

Configure additional features:

# Semantic Caching
semantic_cache:
  enabled: true                   # Enable semantic caching
  backend_type: "memory"          # Options: "memory" or "milvus"
  similarity_threshold: 0.8       # Cache hit threshold
  max_entries: 1000               # Maximum cache entries
  ttl_seconds: 3600               # Cache expiration time
  eviction_policy: "fifo"         # Options: "fifo", "lru", "lfu"

# Tool Auto-Selection
tools:
  enabled: true                    # Enable automatic tool selection
  top_k: 3                        # Number of tools to select
  similarity_threshold: 0.2        # Tool relevance threshold
  tools_db_path: "config/tools_db.json"
  fallback_to_empty: true         # Return empty on failure

# BERT Model for Similarity
bert_model:
  model_id: sentence-transformers/all-MiniLM-L12-v2
  threshold: 0.6                  # Similarity threshold
  use_cpu: true                   # CPU-only inference

# Batch Classification API Configuration
api:
  batch_classification:
    max_batch_size: 100            # Maximum texts per batch request
    concurrency_threshold: 5       # Switch to concurrent processing at this size
    max_concurrency: 8             # Maximum concurrent goroutines
    
    # Metrics configuration for monitoring
    metrics:
      enabled: true                # Enable Prometheus metrics collection
      detailed_goroutine_tracking: true  # Track individual goroutine lifecycle
      high_resolution_timing: false      # Use nanosecond precision timing
      sample_rate: 1.0                   # Collect metrics for all requests (1.0 = 100%)
      
      # Batch size range labels for metrics (OPTIONAL - uses sensible defaults)
      # Default ranges: "1", "2-5", "6-10", "11-20", "21-50", "50+"
      # Only specify if you need custom ranges:
      # batch_size_ranges:
      #   - {min: 1, max: 1, label: "1"}
      #   - {min: 2, max: 5, label: "2-5"}
      #   - {min: 6, max: 10, label: "6-10"}
      #   - {min: 11, max: 20, label: "11-20"}
      #   - {min: 21, max: 50, label: "21-50"}
      #   - {min: 51, max: -1, label: "50+"}  # -1 means no upper limit
      
      # Histogram buckets - choose from presets below or customize
      duration_buckets: [0.001, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10, 30]
      size_buckets: [1, 2, 5, 10, 20, 50, 100, 200]
      
      # Preset examples for quick configuration (copy values above)
      preset_examples:
        fast:
          duration: [0.0001, 0.0005, 0.001, 0.005, 0.01, 0.05, 0.1]
          size: [1, 2, 3, 5, 8, 10]
        standard:
          duration: [0.001, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10]
          size: [1, 2, 5, 10, 20, 50, 100]
        slow:
          duration: [0.1, 0.5, 1, 5, 10, 30, 60, 120]
          size: [10, 50, 100, 500, 1000, 5000]

How to Use Preset Examples

The configuration includes preset examples for quick setup. Here's how to use them:

Step 1: Choose your scenario

• fast - For real-time APIs (microsecond to millisecond response times)
• standard - For typical web APIs (millisecond to second response times)
• slow - For batch processing or heavy computation (seconds to minutes)

Step 2: Copy the preset values

# Example: Switch to fast API configuration
# Copy from preset_examples.fast and paste to the actual config:
duration_buckets: [0.0001, 0.0005, 0.001, 0.005, 0.01, 0.05, 0.1]
size_buckets: [1, 2, 3, 5, 8, 10]

Step 3: Restart the service

pkill -f "router"
make run-router

Default Batch Size Ranges

The system provides sensible default batch size ranges that work well for most use cases:

• "1" - Single text requests
• "2-5" - Small batch requests
• "6-10" - Medium batch requests
• "11-20" - Large batch requests
• "21-50" - Very large batch requests
• "50+" - Maximum batch requests

You don't need to configure batch_size_ranges unless you have specific requirements. The defaults are automatically used when the configuration is omitted.

Configuration Examples by Use Case

Real-time Chat API (fast preset)

# Copy these values to your config for sub-millisecond monitoring
duration_buckets: [0.0001, 0.0005, 0.001, 0.005, 0.01, 0.05, 0.1]
size_buckets: [1, 2, 3, 5, 8, 10]
# batch_size_ranges: uses defaults (no configuration needed)

E-commerce API (standard preset)

# Copy these values for typical web API response times
duration_buckets: [0.001, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10]
size_buckets: [1, 2, 5, 10, 20, 50, 100]
# batch_size_ranges: uses defaults (no configuration needed)

Data Processing Pipeline (slow preset)

# Copy these values for heavy computation workloads
duration_buckets: [0.1, 0.5, 1, 5, 10, 30, 60, 120]
size_buckets: [10, 50, 100, 500, 1000, 5000]
# Custom batch size ranges for large-scale processing (overrides defaults)
batch_size_ranges:
  - {min: 1, max: 50, label: "1-50"}
  - {min: 51, max: 200, label: "51-200"}
  - {min: 201, max: 1000, label: "201-1000"}
  - {min: 1001, max: -1, label: "1000+"}

Available Metrics:

• batch_classification_requests_total - Total number of batch requests
• batch_classification_duration_seconds - Processing duration histogram
• batch_classification_texts_total - Total number of texts processed
• batch_classification_errors_total - Error count by type
• batch_classification_concurrent_goroutines - Active goroutine count
• batch_classification_size_distribution - Batch size distribution

Access metrics at: http://localhost:9190/metrics

Common Configuration Examples

Enable All Security Features

# Enable PII detection
classifier:
  pii_model:
    threshold: 0.8              # Strict PII detection

# Enable jailbreak protection
prompt_guard:
  enabled: true
  threshold: 0.7

# Configure model PII policies
model_config:
  "your-model":
    pii_policy:
      allow_by_default: false   # Block all PII by default
      pii_types_allowed: []     # No PII allowed

Performance Optimization

# Enable caching
semantic_cache:
  enabled: true
  backend_type: "memory"
  similarity_threshold: 0.85    # Higher = more cache hits
  max_entries: 5000
  ttl_seconds: 7200             # 2 hour cache
  eviction_policy: "fifo"       # Options: "fifo", "lru", "lfu"

# Enable tool selection
tools:
  enabled: true
  top_k: 5                     # Select more tools
  similarity_threshold: 0.1    # Lower = more tools selected

Development Setup

# Disable security for testing
prompt_guard:
  enabled: false

# Disable caching for consistent results
semantic_cache:
  enabled: false

# Lower classification thresholds
classifier:
  category_model:
    threshold: 0.3             # Lower = more specialized routing

Configuration Validation

Test Your Configuration

Validate your configuration before starting:

# Test configuration syntax
python -c "import yaml; yaml.safe_load(open('config/config.yaml'))"

# Test the router with your config
make build
make run-router

Common Configuration Patterns

Multiple Models:

vllm_endpoints:
  - name: "math_endpoint"
    address: "math-server.com"
    port: 8000
    models: ["math-model"]
    weight: 1
  - name: "general_endpoint"
    address: "general-server.com"
    port: 8000
    models: ["general-model"]
    weight: 1

categories:
- name: math
  model_scores:
  - model: math-model
    score: 1.0
- name: other
  model_scores:
  - model: general-model
    score: 1.0

Load Balancing:

vllm_endpoints:
  - name: "endpoint1"
    address: "server1.com"
    port: 8000
    models: ["my-model"]
    weight: 2              # Higher weight = more traffic
  - name: "endpoint2"
    address: "server2.com"
    port: 8000
    models: ["my-model"]
    weight: 1

Best Practices

Security Configuration

For production environments:

# Enable all security features
classifier:
  pii_model:
    threshold: 0.8              # Strict PII detection

prompt_guard:
  enabled: true                 # Enable jailbreak protection
  threshold: 0.7

model_config:
  "your-model":
    pii_policy:
      allow_by_default: false   # Block PII by default

Performance Tuning

For high-traffic scenarios:

# Enable caching
semantic_cache:
  enabled: true
  backend_type: "memory"
  similarity_threshold: 0.85    # Higher = more cache hits
  max_entries: 10000
  ttl_seconds: 3600
  eviction_policy: "lru"        

# Optimize classification
classifier:
  category_model:
    threshold: 0.7              # Balance accuracy vs speed

Development vs Production

Development:

# Relaxed settings for testing
classifier:
  category_model:
    threshold: 0.3              # Lower threshold for testing
prompt_guard:
  enabled: false                # Disable for development
semantic_cache:
  enabled: false                # Disable for consistent results

Production:

# Strict settings for production
classifier:
  category_model:
    threshold: 0.7              # Higher threshold for accuracy
prompt_guard:
  enabled: true                 # Enable security
semantic_cache:
  enabled: true                 # Enable for performance

Troubleshooting

Common Issues

Invalid YAML syntax:

# Validate YAML syntax
python -c "import yaml; yaml.safe_load(open('config/config.yaml'))"

Missing model files:

# Check if models are downloaded
ls -la models/
# If missing, run: make download-models

Endpoint connectivity:

# Test your backend server
curl -f http://your-server:8000/health

Configuration not taking effect:

# Restart the router after config changes
make run-router

Testing Configuration

# Test with different queries
make test-auto-prompt-reasoning      # Math query
make test-auto-prompt-no-reasoning   # General query
make test-pii                        # PII detection
make test-prompt-guard               # Jailbreak protection

Model Reasoning Configuration Issues

Model not getting reasoning fields:

• Check that the model name matches a pattern in model_reasoning_configs
• Verify the pattern syntax (exact matches vs prefixes)
• Unknown models will have no reasoning fields applied (this is by design)

Wrong reasoning syntax applied:

• Ensure the reasoning_syntax.type matches your model's expected format
• Check the reasoning_syntax.parameter name is correct
• DeepSeek models typically use chat_template_kwargs with "thinking"
• GPT models typically use reasoning_effort

Adding support for new models:

# Add a new model configuration
model_reasoning_configs:
  - name: "my-new-model"
    patterns: ["my-model"]
    reasoning_syntax:
      type: "chat_template_kwargs"  # or "reasoning_effort"
      parameter: "custom_parameter"

Testing model reasoning configuration:

# Test reasoning with your specific model
curl -X POST http://localhost:8801/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "your-model-name",
    "messages": [{"role": "user", "content": "What is 2+2?"}]
  }'

Configuration Generation

The Semantic Router supports automated configuration generation based on model performance benchmarks. This workflow uses MMLU-Pro evaluation results to determine optimal model routing for different categories.

Benchmarking Workflow

1. Run MMLU-Pro Evaluation:

   # Evaluate models using MMLU-Pro benchmark
   python src/training/model_eval/mmlu_pro_vllm_eval.py \
     --endpoint http://localhost:8000/v1 \
     --models phi4,gemma3:27b,mistral-small3.1 \
     --samples-per-category 5 \
     --use-cot \
     --concurrent-requests 4 \
     --output-dir results

2. Generate Configuration:

   # Generate config.yaml from benchmark results
   python src/training/model_eval/result_to_config.py \
     --results-dir results \
     --output-file config/config.yaml \
     --similarity-threshold 0.80

Generated Configuration Features

The generated configuration includes:

• Model Performance Rankings: Models are ranked by performance for each category
• Reasoning Settings: Automatically configures reasoning requirements per category:
  • use_reasoning: Whether to use step-by-step reasoning
  • reasoning_description: Description of reasoning approach
  • reasoning_effort: Required effort level (low/medium/high)
• Default Model Selection: Best overall performing model is set as default
• Security and Performance Settings: Pre-configured optimal values for:
  • PII detection thresholds
  • Semantic cache settings
  • Tool selection parameters

Customizing Generated Config

The generated config.yaml can be customized by:

1. Editing category-specific settings in result_to_config.py
2. Adjusting thresholds and parameters via command line arguments
3. Manually modifying the generated config.yaml

Example Workflow

Here's a complete example workflow for generating and testing a configuration:

# Run MMLU-Pro evaluation
# Option 1: Specify models manually
python src/training/model_eval/mmlu_pro_vllm_eval.py \
  --endpoint http://localhost:8000/v1 \
  --models phi4,gemma3:27b,mistral-small3.1 \
  --samples-per-category 5 \
  --use-cot \
  --concurrent-requests 4 \
  --output-dir results \
  --max-tokens 2048 \
  --temperature 0.0 \
  --seed 42

# Option 2: Auto-discover models from endpoint
python src/training/model_eval/mmlu_pro_vllm_eval.py \
  --endpoint http://localhost:8000/v1 \
  --samples-per-category 5 \
  --use-cot \
  --concurrent-requests 4 \
  --output-dir results \
  --max-tokens 2048 \
  --temperature 0.0 \
  --seed 42

# Generate initial config
python src/training/model_eval/result_to_config.py \
  --results-dir results \
  --output-file config/config.yaml \
  --similarity-threshold 0.80

# Test the generated config
make test

This workflow ensures your configuration is:

• Based on actual model performance
• Properly tested before deployment
• Version controlled for tracking changes
• Optimized for your specific use case

Next Steps

• Installation Guide - Setup instructions
• Quick Start Guide - Basic usage examples
• API Documentation - Complete API reference

The configuration system is designed to be simple yet powerful. Start with the basic configuration and gradually enable advanced features as needed.