Overview

At a technical level, Lexi is a direct replacement for the OpenAI and Anthropic base URLs. It is fully API-compatible — streaming, tool calls, structured output, and function calling all work without modification.

Lexi uses a share-of-savings billing model. It earns a percentage of what it reduces on each request. On requests where there is nothing to reduce, there is no Lexi fee.

STONE

Lexi sits between your application and the AI provider. Each request passes through STONE (Semantic Token Optimization and Natural Encoding), which restructures the conversation context to use fewer tokens while preserving meaning.

For a full explanation, see the How It Works page.

Getting Started

Three steps to lower token costs.

const openai = new OpenAI({
  baseURL: 'https://api.lexisaas.com/v1',
  apiKey:  'lx_live_yourkey:sk-your-openai-key',
});

Authentication

All API requests require an API key passed in the Authorization header as a Bearer token.

Authorization: Bearer {lexi_key}:{provider_key}

// Example with OpenAI:
Authorization: Bearer lx_live_abc123:sk-openai-abc456

// Example with Anthropic:
Authorization: Bearer lx_live_abc123:sk-ant-abc456

Endpoints

Lexi mirrors the OpenAI and Anthropic API shapes exactly. Any code written for those APIs works through Lexi without changes.

Proxy Proxy

Account Account

Health

Supported Models

Lexi detects which provider to route to from the model name in your request. Use the same model names you already pass to OpenAI or Anthropic today.

Billing

Lexi charges 40% of the savings it creates. If no tokens are saved, there is no Lexi fee.

Billing formula

// Your provider account is billed:
provider_cost = (restructured_tokens / 1_000_000) × model_input_price

// Your Lexi balance is charged:
lexi_fee = 0.40 × savings

where:
  savings = (original_tokens − restructured_tokens) / 1_000_000 × model_input_price

// No savings → lexi_fee = 0. Turn 1 is always passive.

Credits

Response Headers

Every proxied response exposes 16 canonical X-Lexi-* headers. Access them from the browser via Access-Control-Expose-Headers (auto-set).

Every proxied response includes headers showing exactly what happened with that request.

Canonical billing + telemetry headers (16)

Legacy headers (DEPRECATED — migrate to canonical *-Usd set)