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.

For local testing of branch changes, use 18000 as the default test port so you do not disturb the main service on 8000. That applies to both backend work and browser-admin UI verification.

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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