LLMs

> A universal LLM API transformation server, initially developed for the claude-code-router.

How it works

The LLM API transformation server acts as a middleware to standardize requests and responses between different LLM providers (Anthropic, Gemini, Deepseek, etc.). It uses a modular transformer system to handle provider-specific API formats.

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1. Transformers: Each provider (e.g., Anthropic, Gemini) has a dedicated transformer class that implements:

- transformRequestIn: Converts the provider's request format to a unified format.
- transformResponseIn: Converts the provider's response format to a unified format.
- transformRequestOut: Converts the unified request format to the provider's format.
- transformResponseOut: Converts the unified response format back to the provider's format.
- endPoint: Specifies the API endpoint for the provider (e.g., "/v1/messages" for Anthropic).

2. Unified Formats:

- Requests and responses are standardized using UnifiedChatRequest and UnifiedChatResponse types.

3. Streaming Support:
- Handles real-time streaming responses for providers like Anthropic, converting chunked data into a standardized format.

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1. Request:

- Incoming provider-specific requests are transformed into the unified format.
- The unified request is processed by the server.

2. Response:
- The server's unified response is transformed back into the provider's format.
- Streaming responses are handled with chunked data conversion.

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- Anthropic: Converts between OpenAI-style and Anthropic-style message formats.
- Gemini: Adjusts tool definitions and parameter formats for Gemini compatibility.
- Deepseek: Enforces token limits and handles reasoning content in streams.

Run this repo

- Install dependencies:
``sh
npm install
# or pnpm install
`
- Development:
`sh
npm run dev
# Uses nodemon + tsx for hot-reloading src/server.ts
`
- Build:
`sh
npm run build
# Outputs to dist/cjs and dist/esm
`
- Test:
`sh
npm test
# See CLAUDE.md for details
`
- Path alias:
- @ is mapped to the src directory, use import xxx from '@/xxx'.
- Environment variables:
- Supports .env and config.json, see src/services/config.ts`.

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Working with this repo

👉 Contributing Guide