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Launching the open-source gateway

Codex SDK (gateway)

Route Codex SDK model calls through the Respan gateway. The SDK uses the OpenAI Responses API, which the gateway serves at https://api.respan.ai/api/responses, so only your RESPAN_API_KEY is needed. This page only covers gateway routing and does not install or configure tracing instrumentation.

Paste this into your coding agent:

Help me set up the Respan gateway with the Codex SDK integration.
Follow https://www.respan.ai/docs/integrations/gateway/codex-sdk.md

Setup

Install packages

Terminal
npm install @openai/codex-sdk

Set environment variables

Terminal
export RESPAN_API_KEY="YOUR_RESPAN_API_KEY"
export RESPAN_BASE_URL="https://api.respan.ai/api"

No separate provider key is needed when the gateway route is enabled for your Respan key.

Point Codex SDK to the Respan gateway

TypeScript
import { Codex } from "@openai/codex-sdk";

const codex = new Codex({
  apiKey: process.env.RESPAN_API_KEY,
  baseUrl: process.env.RESPAN_BASE_URL ?? "https://api.respan.ai/api",
  env: {
    ...process.env,
    CODEX_API_KEY: process.env.RESPAN_API_KEY!,
    OPENAI_API_KEY: process.env.RESPAN_API_KEY!,
  },
});

const thread = codex.startThread({
  workingDirectory: process.cwd(),
  skipGitRepoCheck: true,
  sandboxMode: "read-only",
  approvalPolicy: "never",
  model: "gpt-5.5",
});

const result = await thread.run("Explain gateway routing in one short sentence.");
console.log(result.finalResponse);

Codex SDK routing depends on the SDK’s Codex-compatible API path. If your key is not enabled for that route, configure gateway access before using this setup.

Switch models

Change the model option on a Codex thread to use another OpenAI model. Codex talks to the gateway’s Responses API route, which serves OpenAI models only, so Claude and Gemini are not available here.

TypeScript
const thread = codex.startThread({
  workingDirectory: process.cwd(),
  skipGitRepoCheck: true,
  sandboxMode: "read-only",
  approvalPolicy: "never",
  model: "gpt-5-mini",
});

See the full model list .