Codex

Branch off your dev environment to create an isolated config so you control the agent's blast radius.

Branch configs are prefixed with the environment slug. dev_agent_codex lives under dev and inherits from its root unless you override.

Scope it down so Codex picks up OPENAI_API_KEY from the environment automatically.

Do not let the agent populate or modify its own secrets. A human decides what goes in this config; the token in the next step is read-only, so the agent can't write back. Add any work credentials the agent legitimately needs to this same config so they inject together, keeping it minimal.

Bound to this one config, with an expiration so a leaked token dies on its own. Capture it into an environment variable so the next steps can reference it without pasting the raw value around.

Service tokens are read-only by default. The agent can fetch secrets, but never change them. This is the agent's identity.

Bind the agent's token to a single directory so the CLI only uses it there. Run this from the folder Codex will work in.

The --scope . flag locks the token to the current directory. Any doppler command run inside that folder, the doppler run launch below, and anything Codex itself invokes, resolves with this scoped agent token and never your personal CLI token.

Note: Run the agent in a sandbox scoped to that directory. And proceed with caution on production workloads: a non-deterministic agent with live credentials is real blast radius, so keep it pointed at dev/test configs unless you have a specific reason not to.

Doppler injects the config's secrets as environment variables, and Codex inherits them. No .env, and when the process exits, the secrets are gone.

Steps 1–6 give Codex the credentials it runs with. The MCP server lets Codex see and operate Doppler itself: list projects, inspect a config, and understand the secret layout before depending on it. Useful in almost any session, so set it up alongside the injection above.

The MCP server uses the same scoped, read-only token you minted in step 4. Codex reads MCP server env from a native env table in config.toml, so pass the token there and add --read-only because the server can't infer read-only from the token alone.

Alternatively, authenticate once with npx @dopplerhq/mcp-server login and drop the env table. Restart Codex after editing the config.