Codex

Codex is OpenAI's terminal AI coding assistant and can connect to SilvaMux Coding Plan.

SilvaMux Coding Plan provides only the Chat Completions and Anthropic Messages endpoints and no Responses API, so Codex must use wire_api = "chat" with a Codex version that supports it.

Before You Start

  1. Purchase a subscription: buy a Coding Plan Personal subscription (Lite / Pro / Max with monthly, quarterly, or yearly billing) on the subscription page; it takes effect immediately after payment.
  2. Create a subscription API key: in the console, go to Coding Plan → API Keys, create a key, and copy the full value starting with cp_live_ right away.
  3. Confirm endpoints and protocols: all tools share the Base URL https://www.silvamux.com/api/coding-plan/v1, compatible with both the OpenAI and Anthropic protocols; see Endpoints & Protocols for endpoint details.

For the full flow of purchasing, key creation, and a verification call, see Quick Start.

Install Codex

  1. Install or update Node.js (v18.0 or later).
  2. Run the following command in a terminal to install Codex.
npm install -g @openai/codex

Verify the install.

codex --version

If the current version no longer supports wire_api = "chat", install a version that does (for example 0.80.0):

npm install -g @openai/codex@0.80.0

Configure Credentials

Edit ~/.codex/config.toml and set model to a supported Coding Plan model:

model_provider = "silvamux_coding_plan"
model = "deepseek-v4-pro"

[model_providers.silvamux_coding_plan]
name = "SilvaMux Coding Plan"
base_url = "https://www.silvamux.com/api/coding-plan/v1"
env_key = "OPENAI_API_KEY"
wire_api = "chat"

The available models follow GET /api/coding-plan/v1/models and the Model Plaza.

Configure Environment Variables

Set the OPENAI_API_KEY environment variable to your cp_live_ key.

macOS

zsh:

echo 'export OPENAI_API_KEY="YOUR_API_KEY"' >> ~/.zshrc
source ~/.zshrc

bash:

echo 'export OPENAI_API_KEY="YOUR_API_KEY"' >> ~/.bash_profile
source ~/.bash_profile

Windows

CMD:

setx OPENAI_API_KEY "YOUR_API_KEY"

PowerShell:

[Environment]::SetEnvironmentVariable("OPENAI_API_KEY", "YOUR_API_KEY", [EnvironmentVariableTarget]::User)

Open a new terminal and confirm it took effect with echo $OPENAI_API_KEY (echo %OPENAI_API_KEY% in Windows CMD).

Use Codex

Open a new terminal and run the following to enter Codex and start chatting:

codex

FAQ

wire_api configuration errors

  • wire_api = "chat" is no longer supported: the current Codex version no longer supports the chat protocol; install a version that does (for example 0.80.0).
  • unknown configuration field wire_api: remove the wire_api field from the corresponding provider section in config.toml.

Error: 401 Unauthorized

  • Confirm you are using a Coding Plan cp_live_ key, not a regular sk_live_ key.
  • Confirm the subscription has not expired and re-copy the key in full (avoid stray spaces).

Error: 404 Not Found

Check that base_url in config.toml is https://www.silvamux.com/api/coding-plan/v1 and that wire_api matches your Codex version.

Error: 429

When any subscription quota window is exhausted, calls return 429 QUOTA_EXCEEDED (the message identifies 5h / weekly / monthly). Wait for the window to recover, or check remaining quota in the console.