Codex — VS Code extension

The Codex extension for VS Code reads the same ~/.codex/config.toml file as the Codex CLI — you just edit it from the extension's settings UI instead of a terminal.

Open config.toml from the extension #

1. In the Codex panel, click the gear icon in the top-right corner and choose "Codex settings".

2. In the left sidebar, click "Configuration".

3. Under "Custom config.toml settings", click "Open config.toml".

4. Add the RouterPlex provider block above the [desktop] table, then save.

# ~/.codex/config.toml
model_provider = "routerplex"
model = "gpt-5.6-terra" # Or any other RouterPlex-supported model
model_reasoning_effort = "low"
 
[desktop]
followUpQueueMode = "queue"
 
[model_providers.routerplex]
name = "RouterPlex"
base_url = "https://api.routerplex.com/v1"
wire_api = "responses"
env_key = "ROUTERPLEX_API_KEY"
env_key_instructions = "Set ROUTERPLEX_API_KEY before starting Codex."

model_provider, model, and model_reasoning_effort must go above [desktop] (or any other bracketed table). TOML keys belong to whichever table header precedes them — paste them below [desktop] and Codex reads them as desktop.model_provider instead of the top-level setting, so the provider silently never applies.

The extension may have already generated other keys in the file — notify, [desktop], [marketplaces.openai-bundled]. Leave those as they are; only the two blocks above are RouterPlex-specific.

Set the API key #

Create a dedicated, budget-capped RouterPlex key in the dashboard. env_key tells Codex to read it from ROUTERPLEX_API_KEY in your OS environment — not from config.toml — so set it where VS Code's process can see it.

macOS / Linux — add it to your shell profile so it persists, then reload the shell:

echo 'export ROUTERPLEX_API_KEY="sk-..."' >> ~/.zshrc   # or ~/.bashrc
source ~/.zshrc

If you normally launch VS Code from the Dock or Spotlight rather than a terminal, note that GUI apps don't inherit variables that only live in a shell profile. Either launch VS Code with code . from a terminal that has sourced the profile, or set it machine-wide with launchctl setenv ROUTERPLEX_API_KEY "sk-..." before opening VS Code.

Windows (PowerShell) — setx persists the variable for future sessions, but not for windows already open:

setx ROUTERPLEX_API_KEY "sk-..."

You can also add it under System Properties → Environment Variables → User variables, which has the same effect and doesn't require a terminal.

Restart VS Code #

Environment variables are read once, at process start — fully quit VS Code (not just "Reload Window") and reopen it so the Codex extension picks up ROUTERPLEX_API_KEY. Then open the Codex panel and send a test prompt; it should show up under the dedicated key in the RouterPlex dashboard.

If Codex reports an unsupported API format, make sure wire_api = "responses" is present. If a model is rejected, copy its case-sensitive ID from the live catalog and update the model value.