responses-proxy-0.1.3 is not a library.

responses-proxy

A proxy that converts OpenAI Responses API to Chat Completions API and back. Supports both HTTP SSE and WebSocket streaming, reasoning/thinking content, and tool calling. Works as a drop-in Codex CLI backend via DeepSeek or any Chat API-compatible provider.

Features

HTTP SSE & WebSocket — both POST /v1/responses (SSE) and GET /v1/responses (WebSocket upgrade)
Reasoning / Thinking — maps reasoning.effort to DeepSeek thinking mode, streams reasoning_text.delta events
Tool Calling — full function_call / function_call_output roundtrip with correct message ordering
Codex CLI Compatible — handles warmup, previous_response_id continuation, and full streaming event chain
Multi-Model — configurable per-model downstream providers

Codex CLI

After starting responses-proxy, add the following line to ~/.codex/config.toml:

openai_base_url = "http://localhost:3000/v1"

Then start Codex and it will route all requests through the proxy.

codex        # uses gpt-5.5 model
codex review # uses codex-auto-review model (if configured)

How It Works

Client (Responses API)  →  POST /v1/responses or WS  →  Convert  →  POST /chat/completions  →  Provider
                              ↑                                                              ↓
                              └──────────────── Convert response back ───────────────────────┘

Quick Start

# Edit config.yaml with your provider details, then start
cargo run
# Listening on 0.0.0.0:3000

# List configured models
curl http://localhost:3000/v1/models

# Send a Responses API request
curl http://localhost:3000/v1/responses \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.5",
    "input": "What is 2+2? Reply with just the number."
  }'

Configuration (`config.yaml`)

server:
  listen_addr: "0.0.0.0:3000"
  request_timeout: 30

  # Log level: trace, debug, info, warn, error (default: info)
  # Overridden by RUST_LOG env var if set.
  log_level: info

  # Authentication (optional)
  auth:
    enabled: false # Set to true to require API key
    keys:
      - sk-your-key-here

  # Tool type allowlist (default: ["function"])
  tool_type_allowlist:
    - function

models:
  - model: gpt-5.5
    provider:
      base_url: https://api.deepseek.com
      api_key: $DEEPSEEK_API_KEY # or static key
    downstream_model: deepseek-v4-pro # optional, defaults to model

  - model: codex-auto-review
    provider:
      base_url: https://api.deepseek.com
      api_key: $DEEPSEEK_API_KEY
    downstream_model: deepseek-v4-flash

Endpoints

Method	Path	Auth	Description
`GET`	`/health`	No	Health check
`GET`	`/v1/models`	Optional	List configured models (OpenAI-compatible format)
`POST`	`/v1/responses`	Optional	Main proxy endpoint

Supported Conversions

Request: Responses API → Chat API

Responses Field	Chat Field	Notes
`input` (string or array)	`messages`	String → `[{role:"user", content}]`. Array → converts messages, function_call, function_call_output items
`instructions`	system message	Prepended; merged with existing system/developer messages in input
`reasoning`	`thinking`	Maps to DeepSeek `thinking: {type: "enabled"}`
`max_output_tokens`	`max_tokens`
`tools` (flat)	`tools` (nested)	Wraps fields under `function` key; filtered by `tool_type_allowlist`
`tool_choice`	`tool_choice`	Passthrough
`temperature`, `top_p`, `stream`, `stop`, `top_logprobs`	same	Passthrough

Response: Chat API → Responses API

Chat Field	Responses Field	Notes
`choices[0].message.content`	`output[{type:"message"}]`	Wrapped in `output_text` content blocks
`choices[0].message.tool_calls`	`output[{type:"function_call"}]`
`finish_reason=content_filter` + null content	`output[{type:"refusal"}]`
`usage.prompt_tokens`	`usage.input_tokens`
`prompt_cache_hit/miss_tokens`	`usage.input_tokens_details.cached_tokens`	Sum of hit + miss

Streaming

Set "stream": true in the Responses API request. The proxy converts Chat API SSE chunks into Responses API streaming events (response.created → response.output_text.delta → response.completed). Tool call deltas are accumulated across chunks and emitted in the final event.

Authentication

When server.auth.enabled: true, requests to /v1/models and /v1/responses require an Authorization: Bearer <key> header. The key must match one of the keys in server.auth.keys. /health is always open.

Tool Type Allowlist

server.tool_type_allowlist controls which tool types pass through to the downstream provider. Default is ["function"]. Any tool in the Responses API request whose type is not in this list is silently dropped. For example, to also allow web search tools from compatible providers:

server:
  tool_type_allowlist:
    - function
    - web_search_preview

Environment Variable References

base_url and api_key support $VAR environment variable references:

provider:
  base_url: $MY_BASE_URL        # reads from $MY_BASE_URL
  api_key: $DEEPSEEK_API_KEY    # reads from $DEEPSEEK_API_KEY
  api_key: sk-plain-text-key    # static key

responses-proxy 0.1.3