anyllm_translate

Pure, IO-free translation between Anthropic Messages API and OpenAI Chat Completions / Responses API formats. Also supports Google Gemini native API translation.

No HTTP clients, no async runtime, no network calls. Just fn(A) -> B transformations.

Quick Start

use anyllm_translate::{TranslationConfig, translate_request, translate_response};
use anyllm_translate::anthropic::MessageCreateRequest;

let config = TranslationConfig::builder()
    .model_map("haiku", "gpt-4o-mini")
    .model_map("sonnet", "gpt-4o")
    .model_map("opus", "gpt-4o")
    .build();

let req: MessageCreateRequest = serde_json::from_str(r#"{
    "model": "claude-sonnet-4-6",
    "max_tokens": 100,
    "messages": [{"role": "user", "content": "Hello"}]
}"#).unwrap();

let openai_req = translate_request(&req, &config).unwrap();
assert_eq!(openai_req.model, "gpt-4o");

// Send openai_req to OpenAI, get response, then:
// let anthropic_resp = translate_response(&openai_resp, &req.model);

Supported APIs

Anthropic Messages API (request/response types, streaming SSE events)
OpenAI Chat Completions API (request/response types, streaming chunks)
OpenAI Responses API (request/response types, streaming events)
Google Gemini native API (generateContent types, streaming)

Features

Default: Pure translation types and mapping functions
middleware: Adds an axum middleware layer that intercepts Anthropic-format requests, translates them, forwards to a configurable backend, and translates responses back

[dependencies]
anyllm_translate = "0.1"

# With middleware support:
anyllm_translate = { version = "0.1", features = ["middleware"] }

Modules

Module	Description
`anthropic`	Anthropic Messages API types (request, response, streaming, errors)
`openai`	OpenAI Chat Completions and Responses API types
`gemini`	Google Gemini native API types
`mapping`	Stateless conversion functions between APIs
`config`	Translation configuration (model mapping, lossy behavior)
`translate`	Convenience wrappers combining config with mapping
`middleware`	Axum middleware layer (requires `middleware` feature)

Translation Coverage

Text messages, multi-turn conversations
System prompts (Anthropic system to OpenAI developer role or Responses instructions)
Tool definitions, tool calls, tool results
Image and document content blocks (documents degrade to text notes)
Streaming SSE event translation (state machines for each backend)
Token usage mapping
Error type/status code translation
Extended thinking (stripped when targeting OpenAI)

This crate is part of anyllm-proxy, which also includes a standalone HTTP proxy server.