CLASP - Claude Language Agent Super Proxy

A high-performance Go proxy that translates Claude/Anthropic API calls to OpenAI-compatible endpoints, enabling Claude Code to work with any LLM provider.

Features

• Bundled Claude Code: Automatically includes Claude Code as a dependency - single npx clasp-ai installs everything
• Multi-Provider Support: OpenAI, Azure OpenAI, OpenRouter (200+ models), and custom endpoints (Ollama, vLLM, LM Studio)
• Full Protocol Translation: Anthropic Messages API ↔ OpenAI Chat Completions API
• SSE Streaming: Real-time token streaming with state machine processing
• Tool Calls: Complete translation of tool_use/tool_result between formats
• Connection Pooling: Optimized HTTP transport with persistent connections
• Retry Logic: Exponential backoff for transient failures
• Metrics Endpoint: Request statistics and performance monitoring
• API Key Authentication: Secure the proxy with optional API key validation

Installation

Via npm (recommended)

# Install globally
npm install -g clasp-ai

# Or run directly with npx
npx clasp-ai

Via Go

go install github.com/jedarden/clasp/cmd/clasp@latest

From Source

git clone https://github.com/jedarden/CLASP.git
cd CLASP
make build

Via Docker

# Run with Docker (from GitHub Container Registry)
docker run -d -p 8080:8080 \
  -e OPENAI_API_KEY=sk-... \
  ghcr.io/jedarden/clasp:latest

# With specific version
docker run -d -p 8080:8080 \
  -e OPENAI_API_KEY=sk-... \
  ghcr.io/jedarden/clasp:0.24.8

# Or with docker-compose
docker-compose up -d

Available Docker tags:

• latest - Latest stable release
• 0.24 - Latest 0.24.x release
• 0.24.8 - Specific version

Quick Start

Using with OpenAI

# Set your API key
export OPENAI_API_KEY=sk-...

# Start the proxy
clasp -model gpt-4o

# In another terminal, use Claude Code
ANTHROPIC_BASE_URL=http://localhost:8080 claude

Using with Azure OpenAI

export AZURE_API_KEY=your-key
export AZURE_OPENAI_ENDPOINT=https://your-resource.openai.azure.com
export AZURE_DEPLOYMENT_NAME=gpt-4

clasp -provider azure

Using with OpenRouter

export OPENROUTER_API_KEY=sk-or-...

clasp -provider openrouter -model anthropic/claude-3-sonnet

Using with Local Models (Ollama)

export CUSTOM_BASE_URL=http://localhost:11434/v1

clasp -provider custom -model llama3.1

Configuration

Command Line Options

clasp [options]

Options:
  -port <port>           Port to listen on (default: 8080)
  -provider <name>       LLM provider: openai, azure, openrouter, custom
  -model <model>         Default model to use for all requests
  -debug                 Enable debug logging (full request/response)
  -rate-limit            Enable rate limiting
  -cache                 Enable response caching
  -cache-max-size <n>    Maximum cache entries (default: 1000)
  -cache-ttl <n>         Cache TTL in seconds (default: 3600)
  -multi-provider        Enable multi-provider tier routing
  -fallback              Enable fallback routing for auto-failover
  -auth                  Enable API key authentication
  -auth-api-key <key>    API key for authentication (required with -auth)
  -version               Show version information
  -help                  Show help message

Environment Variables

Variable	Description	Default
PROVIDER	LLM provider type	openai
CLASP_PORT	Proxy server port	8080
CLASP_MODEL	Default model	-
CLASP_MODEL_OPUS	Model for Opus tier	-
CLASP_MODEL_SONNET	Model for Sonnet tier	-
CLASP_MODEL_HAIKU	Model for Haiku tier	-
OPENAI_API_KEY	OpenAI API key	-
OPENAI_BASE_URL	Custom OpenAI base URL	https://api.openai.com/v1
AZURE_API_KEY	Azure OpenAI API key	-
AZURE_OPENAI_ENDPOINT	Azure endpoint URL	-
AZURE_DEPLOYMENT_NAME	Azure deployment name	-
AZURE_API_VERSION	Azure API version	2024-02-15-preview
OPENROUTER_API_KEY	OpenRouter API key	-
CUSTOM_BASE_URL	Custom endpoint base URL	-
CUSTOM_API_KEY	Custom endpoint API key	-
CLASP_DEBUG	Enable all debug logging	false
CLASP_DEBUG_REQUESTS	Log requests only	false
CLASP_DEBUG_RESPONSES	Log responses only	false
CLASP_RATE_LIMIT	Enable rate limiting	false
CLASP_RATE_LIMIT_REQUESTS	Requests per window	60
CLASP_RATE_LIMIT_WINDOW	Window in seconds	60
CLASP_RATE_LIMIT_BURST	Burst allowance	10
CLASP_CACHE	Enable response caching	false
CLASP_CACHE_MAX_SIZE	Maximum cache entries	1000
CLASP_CACHE_TTL	Cache TTL in seconds	3600
CLASP_MULTI_PROVIDER	Enable multi-provider routing	false
CLASP_FALLBACK	Enable fallback routing	false
CLASP_AUTH	Enable API key authentication	false
CLASP_AUTH_API_KEY	Required API key for access	-
CLASP_AUTH_ALLOW_ANONYMOUS_HEALTH	Allow /health without auth	true
CLASP_AUTH_ALLOW_ANONYMOUS_METRICS	Allow /metrics without auth	false

Model Mapping

CLASP can automatically map Claude model tiers to your provider's models:

# Map Claude tiers to specific models
export CLASP_MODEL_OPUS=gpt-4o
export CLASP_MODEL_SONNET=gpt-4o-mini
export CLASP_MODEL_HAIKU=gpt-3.5-turbo

Multi-Provider Routing

Route different Claude model tiers to different LLM providers for cost optimization:

# Enable multi-provider routing
export CLASP_MULTI_PROVIDER=true

# Route Opus tier to OpenAI (premium)
export CLASP_OPUS_PROVIDER=openai
export CLASP_OPUS_MODEL=gpt-4o
export CLASP_OPUS_API_KEY=sk-...  # Optional, inherits from OPENAI_API_KEY

# Route Sonnet tier to OpenRouter (cost-effective)
export CLASP_SONNET_PROVIDER=openrouter
export CLASP_SONNET_MODEL=anthropic/claude-3-sonnet
export CLASP_SONNET_API_KEY=sk-or-...  # Optional, inherits from OPENROUTER_API_KEY

# Route Haiku tier to local Ollama (free)
export CLASP_HAIKU_PROVIDER=custom
export CLASP_HAIKU_MODEL=llama3.1
export CLASP_HAIKU_BASE_URL=http://localhost:11434/v1

clasp -multi-provider

Multi-Provider Environment Variables:

Variable	Description
CLASP_MULTI_PROVIDER	Enable multi-provider routing (true/1)
CLASP_{TIER}_PROVIDER	Provider for tier: openai, openrouter, custom
CLASP_{TIER}_MODEL	Model name for the tier
CLASP_{TIER}_API_KEY	API key (optional, inherits from main config)
CLASP_{TIER}_BASE_URL	Base URL (optional, uses provider default)

Where {TIER} is OPUS, SONNET, or HAIKU.

Benefits:

• Cost Optimization: Use expensive providers only for complex tasks
• Latency Reduction: Route simple requests to faster local models
• Redundancy: Mix cloud and local providers for reliability
• A/B Testing: Compare different models across tiers

API Endpoints

Endpoint	Description
POST /v1/messages	Anthropic Messages API (translated)
GET /health	Health check
GET /metrics	Request statistics (JSON)
GET /metrics/prometheus	Prometheus metrics
GET /	Server info

Example Usage

With curl

curl http://localhost:8080/v1/messages \
  -H "Content-Type: application/json" \
  -H "x-api-key: any-key" \
  -d '{
    "model": "claude-3-5-sonnet-20241022",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": "Hello!"}
    ]
  }'

Streaming

curl http://localhost:8080/v1/messages \
  -H "Content-Type: application/json" \
  -H "x-api-key: any-key" \
  -d '{
    "model": "claude-3-5-sonnet-20241022",
    "max_tokens": 1024,
    "stream": true,
    "messages": [
      {"role": "user", "content": "Count to 5"}
    ]
  }'

Response Caching

CLASP can cache responses to reduce API costs and improve latency for repeated requests:

# Enable caching with defaults (1000 entries, 1 hour TTL)
clasp -cache

# Custom cache settings
clasp -cache -cache-max-size 500 -cache-ttl 1800

# Via environment
CLASP_CACHE=true CLASP_CACHE_MAX_SIZE=500 clasp

Caching behavior:

• Only non-streaming requests are cached
• Requests with temperature > 0 are not cached (non-deterministic)
• Cache uses LRU (Least Recently Used) eviction when full
• Cache entries expire after TTL (time-to-live)
• Response headers include X-CLASP-Cache: HIT or X-CLASP-Cache: MISS

Metrics

Access /metrics for request statistics:

{
  "requests": {
    "total": 100,
    "successful": 98,
    "errors": 2,
    "streaming": 75,
    "tool_calls": 15,
    "success_rate": "98.00%"
  },
  "performance": {
    "avg_latency_ms": "523.50",
    "requests_per_sec": "2.34"
  },
  "cache": {
    "enabled": true,
    "size": 42,
    "max_size": 1000,
    "hits": 156,
    "misses": 44,
    "hit_rate": "78.00%"
  },
  "uptime": "5m30s"
}

Docker

Build and Run

# Build Docker image
make docker

# Run container
make docker-run

# Stop container
make docker-stop

Docker Compose

Create a .env file with your configuration:

PROVIDER=openai
OPENAI_API_KEY=sk-...
CLASP_DEFAULT_MODEL=gpt-4o

Then start the service:

docker-compose up -d

Docker Environment Variables

All configuration is done through environment variables. See the Environment Variables section above.

Development

# Build
make build

# Run tests
make test

# Build for all platforms
make build-all

# Build Docker image
make docker

# Format code
make fmt

Debugging

Enable debug logging to troubleshoot issues:

# Via CLI flag
clasp -debug

# Via environment variable
CLASP_DEBUG=true clasp

# Log only requests or responses
CLASP_DEBUG_REQUESTS=true clasp
CLASP_DEBUG_RESPONSES=true clasp

Debug output includes:

• Incoming Anthropic requests
• Outgoing OpenAI requests
• Raw OpenAI responses
• Transformed Anthropic responses

Authentication

Secure your CLASP proxy with API key authentication to control access:

# Enable authentication with CLI flags
clasp -auth -auth-api-key "my-secret-key"

# Or via environment variables
CLASP_AUTH=true CLASP_AUTH_API_KEY="my-secret-key" clasp

Providing the API Key

Clients can provide the API key in two ways:

# Via x-api-key header
curl http://localhost:8080/v1/messages \
  -H "x-api-key: my-secret-key" \
  -H "Content-Type: application/json" \
  -d '{"model": "claude-3-5-sonnet-20241022", ...}'

# Via Authorization header (Bearer token)
curl http://localhost:8080/v1/messages \
  -H "Authorization: Bearer my-secret-key" \
  -H "Content-Type: application/json" \
  -d '{"model": "claude-3-5-sonnet-20241022", ...}'

Authentication Options

Variable	Description	Default
CLASP_AUTH	Enable authentication	false
CLASP_AUTH_API_KEY	Required API key	-
CLASP_AUTH_ALLOW_ANONYMOUS_HEALTH	Allow /health without auth	true
CLASP_AUTH_ALLOW_ANONYMOUS_METRICS	Allow /metrics without auth	false

Endpoint Access with Authentication Enabled

Endpoint	Default Access
/	Always accessible
/health	Anonymous by default
/metrics	Requires auth by default
/metrics/prometheus	Requires auth by default
/v1/messages	Requires auth

Using with Claude Code

When authentication is enabled, set both the base URL and API key:

# Start CLASP with auth
OPENAI_API_KEY=sk-... clasp -auth -auth-api-key "proxy-key"

# Use with Claude Code (the proxy key is passed as the Anthropic key)
ANTHROPIC_BASE_URL=http://localhost:8080 ANTHROPIC_API_KEY=proxy-key claude

Request Queuing

Queue requests during provider outages for automatic retry:

# Enable request queuing
clasp -queue

# Custom queue settings
clasp -queue -queue-max-size 200 -queue-max-wait 60

# Via environment
CLASP_QUEUE=true CLASP_QUEUE_MAX_SIZE=200 clasp

Queue Options

Variable	Description	Default
CLASP_QUEUE	Enable request queuing	false
CLASP_QUEUE_MAX_SIZE	Maximum queued requests	100
CLASP_QUEUE_MAX_WAIT	Queue timeout in seconds	30
CLASP_QUEUE_RETRY_DELAY	Retry delay in milliseconds	1000
CLASP_QUEUE_MAX_RETRIES	Maximum retries per request	3

Circuit Breaker

Prevent cascade failures with circuit breaker pattern:

# Enable circuit breaker
clasp -circuit-breaker

# Custom circuit breaker settings
clasp -circuit-breaker -cb-threshold 10 -cb-recovery 3 -cb-timeout 60

# Via environment
CLASP_CIRCUIT_BREAKER=true clasp

Circuit Breaker Options

Variable	Description	Default
CLASP_CIRCUIT_BREAKER	Enable circuit breaker	false
CLASP_CIRCUIT_BREAKER_THRESHOLD	Failures before opening circuit	5
CLASP_CIRCUIT_BREAKER_RECOVERY	Successes to close circuit	2
CLASP_CIRCUIT_BREAKER_TIMEOUT	Timeout in seconds before retry	30

Circuit Breaker States

• Closed: Normal operation, requests pass through
• Open: Circuit tripped, requests fail fast with 503
• Half-Open: Testing if service recovered, limited requests allowed

Maximum Resilience Configuration

For production deployments requiring maximum resilience:

# Enable queue + circuit breaker + fallback
OPENAI_API_KEY=sk-xxx OPENROUTER_API_KEY=sk-or-xxx \
  clasp -queue -circuit-breaker -fallback \
    -queue-max-size 200 \
    -cb-threshold 5 \
    -cb-timeout 30

License

MIT License - see LICENSE for details.

Contributing

Contributions are welcome! Please open an issue or submit a pull request on GitHub.