ChatMock

Allows Codex to work in your favourite chat apps and coding tools.

Install

Homebrew

brew tap RayBytes/chatmock
brew install chatmock

pipx / pip

pipx install chatmock

GUI

Download from releases (macOS & Windows)

Docker

See DOCKER.md

Getting Started

# 1. Sign in with your ChatGPT account
chatmock login

# 2. Start the server
chatmock serve

The server runs at http://127.0.0.1:8000 by default. Use http://127.0.0.1:8000/v1 as your base URL for OpenAI-compatible apps.

Usage

Python

from openai import OpenAI

client = OpenAI(
    base_url="http://127.0.0.1:8000/v1",
    api_key="anything"  # not checked
)

response = client.chat.completions.create(
    model="gpt-5.4",
    messages=[{"role": "user", "content": "hello"}]
)
print(response.choices[0].message.content)

cURL

curl http://127.0.0.1:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.4",
    "messages": [{"role": "user", "content": "hello"}]
  }'

Supported Models

• gpt-5.4
• gpt-5.4-mini
• gpt-5.2
• gpt-5.1
• gpt-5
• gpt-5.3-codex
• gpt-5.3-codex-spark
• gpt-5.2-codex
• gpt-5-codex
• gpt-5.1-codex
• gpt-5.1-codex-max
• gpt-5.1-codex-mini
• codex-mini

Features

• Tool / function calling
• Vision / image input
• Thinking summaries (via think tags)
• Configurable thinking effort
• Fast mode for supported models
• Web search tool
• OpenAI-compatible /v1/responses (HTTP + WebSocket)
• Ollama-compatible endpoints
• Reasoning effort exposed as separate models (optional)

Configuration

All flags go after chatmock serve. These can also be set as environment variables.

Flag	Env var	Options	Default	Description
--reasoning-effort	CHATGPT_LOCAL_REASONING_EFFORT	none, minimal, low, medium, high, xhigh	medium	How hard the model thinks
--reasoning-summary	CHATGPT_LOCAL_REASONING_SUMMARY	auto, concise, detailed, none	auto	Thinking summary verbosity
--reasoning-compat	CHATGPT_LOCAL_REASONING_COMPAT	legacy, o3, think-tags	think-tags	How reasoning is returned to the client
--fast-mode	CHATGPT_LOCAL_FAST_MODE	true/false	false	Priority processing for supported models
--enable-web-search	CHATGPT_LOCAL_ENABLE_WEB_SEARCH	true/false	false	Allow the model to search the web
--expose-reasoning-models	CHATGPT_LOCAL_EXPOSE_REASONING_MODELS	true/false	false	List each reasoning level as its own model

Web search in a request

{
  "model": "gpt-5.4",
  "messages": [{"role": "user", "content": "latest news on ..."}],
  "responses_tools": [{"type": "web_search"}],
  "responses_tool_choice": "auto"
}

Fast mode in a request

{
  "model": "gpt-5.4",
  "input": "summarize this",
  "fast_mode": true
}

Notes

Use responsibly and at your own risk. This project is not affiliated with OpenAI.

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