Use ScaledThought with Codex

POST $ST_BASE_URL/responses speaks the OpenAI Responses API, so clients that use only that protocol, such as Codex, can use ScaledThought as their model provider. It takes input (a string, or messages, function_call and function_call_output items), instructions, function and custom (freeform) tools, tool_choice, max_output_tokens, text.format for JSON output and stream: true (Responses events, ending with response.completed or response.incomplete with its usage, or response.failed with an error).

It is stateless. We store no responses, so send the whole conversation in input every turn (Codex does) and leave out previous_response_id, which returns 400 invalid_request; store is always false. Hosted tools such as file search return 400; a web search tool is ignored. Requests without max_output_tokens get a cap of what the model's context leaves after your prompt, at most 32,768 tokens.

Paste the prompt above into your coding agent, or run the command yourself in your project's directory. It creates the account, writes ST_API_KEY and ST_BASE_URL to ./.env (mode 0600) and adds .env to .gitignore. Only the US region is open; Canada is coming soon.

npx -y scaledthought@0.3 init --region us --source org-codex

Usage is prepaid, so a new account answers 402 insufficient_credits until its first top-up. This prints a payment link and opens it in your browser; nothing is charged until you pay on it. How prepaid credits work

npx -y scaledthought@0.3 billing topup --amount-usd 20
npx -y scaledthought@0.3 billing wait

Add this to ~/.codex/config.toml. npx -y scaledthought@0.3 models --live lists every model live in your region; the examples use deepseek-v4-1-flash.

# ~/.codex/config.toml
model = "deepseek-v4-1-flash"  # or a model id from `npx -y scaledthought@0.3 models --live`
model_provider = "scaledthought"

[model_providers.scaledthought]
name = "ScaledThought"
base_url = "https://api.us.scaledthought.com/v1"  # your ST_BASE_URL
env_key = "ST_API_KEY"
wire_api = "responses"
model_catalog_url = "https://api.us.scaledthought.com/v1/codex/models"  # same host (and region) as base_url

Codex reads the key from the environment, not from .env, so load it first.

set -a; . ./.env; set +a  # puts ST_API_KEY in the environment
codex

• Codex reads ST_API_KEY from the environment, so load ./.env into the shell first. wire_api = "responses" is required: ScaledThought serves Codex over the Responses API.
• model_catalog_url tells Codex the context windows of the models live in your region, so it compacts long sessions in time, and gives it its apply_patch editing tool. It is built from the live models on every request; Codex sends your key with it, so keep it on the same host as base_url (your region's).

• Codex configuration docs, read 2026-10-12.
• ScaledThought: /llms.txt (the setup protocol) and the docs.