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

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)

Related

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