How to configure a custom Base URL and API Key in the VS Code Codex extension

Direct answer

The VS Code Codex extension has no separate Base URL or API Key fields. It shares configuration layers with Codex CLI. Click the gear icon, choose Codex Settings → Open config.toml, and add the BetterToken provider to your user config. Then run Developer: Reload Window so the extension reads the new endpoint, Key, and model.

It is normal if you do not see Base URL or API Key fields in VS Code settings. Do not put the custom endpoint in the general VS Code proxy settings.

Prerequisites

VS Code is installed
The Codex - OpenAI’s coding agent extension is installed
You have a BetterToken API Key (sign up and get one)
You have copied an available model ID from the GPT Key group in the model plaza

Do not put your API Key in project files, AGENTS.md, sample .env files, or public repositories. The configuration below should stay in your local Codex configuration directory.

Setup methods

Recommended: use the Setup dialog
Manual configuration

After you create an API Key, the console opens a Setup dialog. From that dialog, copy API Key and Base URL, then choose a Codex setup method.

Select Codex

Select Codex under Available tools.

Choose a setup method

You can choose:

One-click Bash Configuration: copy the command and run it in your local terminal. Use this for quick setup.
CC Switch Integration: import the provider into CC Switch. Use this when you manage multiple tools.
Manual Configuration: copy API Key and Base URL, then write them into config.toml.

Restart VS Code

After the configuration is written, restart VS Code or run Developer: Reload Window so the Codex extension reads the local configuration again.

Find config.toml

Click the gear icon in the Codex extension and choose Codex Settings → Open config.toml. You can also open:

System	Configuration file
macOS / Linux	`~/.codex/config.toml`
Windows	`C:\Users\YOUR_USER\.codex\config.toml`
Windows + WSL	`~/.codex/config.toml` inside WSL

Codex CLI and the IDE extension read the same config layers. For a project opened through WSL, edit the file inside WSL rather than a separate file in the Windows user directory.

Add the BetterToken provider

Add the configuration below to config.toml. If the file already contains the same top-level fields, merge the configuration instead of writing duplicate model_provider entries.

model_provider = "custom"
model = "gpt-5.5"
review_model = "gpt-5.4"
model_reasoning_effort = "high"
model_context_window = 1000000
model_auto_compact_token_limit = 900000
windows_wsl_setup_acknowledged = true

[model_providers]
[model_providers.custom]
name = "BetterToken"
base_url = "https://www.bettertoken.ai/v1"
wire_api = "responses"
requires_openai_auth = true
experimental_bearer_token = "YOUR_API_KEY"
request_max_retries = 4
stream_max_retries = 8
stream_idle_timeout_ms = 300000
supports_websockets = false

Replace YOUR_API_KEY with your BetterToken API Key.

Confirm the key fields

Check these fields first:

Field	Value
`base_url`	`https://www.bettertoken.ai/v1`
`wire_api`	`responses`
`model`	A model ID copied from the GPT Key group
`experimental_bearer_token`	Your BetterToken API Key

For the VS Code Codex extension, do not convert auth.json into an API Key-only structure. auth.json keeps the official Codex login state; the third-party API Key belongs in experimental_bearer_token.

Restart VS Code

After editing the file, close the current Codex session and restart VS Code.You can also run this from the command palette:

Developer: Reload Window

The VS Code Codex extension depends on Codex app-side capabilities such as the extension UI, session management, and VS Code integration. Keep the official login state while routing model requests through BetterToken. In this configuration:

Setting	What it does
`requires_openai_auth = true`	Keeps the official Codex login state
`experimental_bearer_token = "YOUR_API_KEY"`	Uses your BetterToken API Key for model requests
`base_url = "https://www.bettertoken.ai/v1"`	Sends model requests to BetterToken’s OpenAI-compatible / Responses API endpoint

The official Codex config reference recommends env_key for ordinary custom-provider API Keys. This page uses experimental_bearer_token because this scenario also preserves the official Codex login. If you only use Codex CLI and do not need plugins, Remote Control, or the official login state, use the ordinary custom-provider config.toml setup.

Verify which config the extension reads

After setup, open the Codex extension in VS Code and send a short test message. If you get a normal response, the configuration is active. You can also open config.toml from the extension gear again and confirm it is the file you edited.

Common errors

Symptom	Cause	Fix
Codex CLI works but the VS Code extension fails	The extension runs in another environment or has stale state	Open the actual config from the gear icon; edit the WSL file for WSL projects; run Developer: Reload Window
The extension still asks for official login	The Codex IDE extension needs its application-side login	Complete official sign-in, then keep `requires_openai_auth = true` and the third-party bearer token
`401` or `403`	Wrong API Key or unchanged `experimental_bearer_token`	Copy the Key again and do not replace the official login data in `auth.json`
`404`	Base URL is missing `/v1`	Use `https://www.bettertoken.ai/v1`
Model not found	The Model ID is not in the GPT Key group	Copy a current ID from the model plaza
TOML parse error	A field or table is declared twice	Merge the existing config and keep one `[model_providers.custom]` table

Getting started

Coding Agent setup

AI application platform setup

Advanced

How to configure a custom Base URL and API Key in the VS Code Codex extension

Direct answer

Prerequisites

Setup methods

Verify which config the extension reads

Common errors

References

​Direct answer

​Prerequisites

​Setup methods

​Why keep the official login state?

​Verify which config the extension reads

​Common errors

​Related docs

​References

Direct answer

Prerequisites

Setup methods

Why keep the official login state?

Verify which config the extension reads

Common errors

Related docs

References