Codex is a terminal coding tool that can read and modify project files. You do not need it for ordinary web chat.

​
Install

Install Node.js, then run: 
npm install -g @openai/codex

​
Set the key in your current terminal

PowerShell: 
$env:INFISTAR_API_KEY = "YOUR_API_KEY"
macOS or Linux: 
export INFISTAR_API_KEY="YOUR_API_KEY"

​
Configure the provider

Edit %USERPROFILE%\.codex\config.toml on Windows or ~/.codex/config.toml on macOS/Linux. Replace the placeholder model with an exact Responses-compatible model ID available to your key: 
model = "YOUR_EXACT_MODEL_ID"
model_provider = "infistar"

[model_providers.infistar]
name = "Infistar"
base_url = "https://infistar.ai/v1"
env_key = "INFISTAR_API_KEY"
wire_api = "responses"
The environment variable must be available in the same terminal that runs codex; setting it in one shell does not automatically persist it in a new shell.

​
Verify

Run codex in your project directory. For an initial configuration check, ask: 
Reply only with "Configuration successful". Do not read or modify files, and do not run commands.
If the key is missing, set the variable again in that terminal. For 404, check the base URL includes /v1 exactly once. For model errors, copy the current exact ID from Model Square. Review proposed actions and diffs before permitting edits. Provider fields follow the official Codex configuration reference.