claudex: use Claude Code's interface with GPT/Codex models through CLIProxyAPI

A developer created claudex, a tool that allows users to run OpenAI's GPT/Codex models through Claude Code's interface and terminal UX. It uses a local CLIProxyAPI server to translate and route requests, preserving the original Claude Code and Codex configurations. The tool is designed for developers who prefer Claude Code's agent harness but want to use GPT models underneath.

Inspired by Theo's original post on X . The basic idea: if you prefer Claude Code's agent harness and terminal UX to the Codex CLI, claudex lets you keep Claude Code's interface, tools, permissions, plugins, and workflow while using GPT/Codex models underneath. A local CLIProxyAPI https://github.com/router-for-me/CLIProxyAPI server translates and routes Claude Code's requests to a model available through Codex OAuth. The important isolation rule is: claude continues to work normally with its existing account and configuration. codex continues to work normally with its existing configuration.- Only claudex uses the local proxy and the selected Codex model. Set up a new claudex command on my machine. It must run the Claude Code CLI interface and tooling while using gpt-5.6-sol through my Codex OAuth account and a localhost-only CLIProxyAPI server. Requirements: 1. Inspect before changing anything - Locate cli-proxy-api , claude , and codex and report their versions. - Inspect cli-proxy-api --help and any installed example config or systemd unit. - Inspect my shell configuration for existing claude , claudex , or similar aliases/functions. - Preserve all existing Claude Code and Codex behavior. - Do not print existing OAuth tokens, API keys, or credential-file contents. 2. Install CLIProxyAPI if it is missing - Use the official CLIProxyAPI quick-start documentation for the detected operating system. Do not invent package names or download URLs. - macOS with Homebrew: brew install cliproxyapi Be aware that brew services expects its config at $ brew --prefix /etc/cliproxyapi.conf . If this setup uses ~/.cli-proxy-api/config.yaml , safely back up any existing Homebrew config and symlink that expected path to the user config before starting the service. - Arch Linux: yay -S cli-proxy-api-bin or paru -S cli-proxy-api-bin The package includes an example config and a systemd user service. - Other Linux distributions: use the official installer from router-for-me/cliproxyapi-installer . Download it to a temporary file, inspect it, then run it; do not blindly execute a remote script if the environment's security policy forbids that. - Windows: use the current binary from the official GitHub releases page. This particular claudex alias targets zsh on macOS/Linux/WSL; adapt it to a PowerShell function only if the user explicitly wants native Windows. - Building from source is a fallback only when packages/releases are unsuitable; use the repository's documented go build -o cli-proxy-api ./cmd/server command and verify the required Go version first. - After installation, run cli-proxy-api --help and record the installed version. Confirm that the build exposes Codex and Claude OAuth flags before continuing. - Do not start the background service until a valid config file exists. 3. Configure CLIProxyAPI - Use ~/.cli-proxy-api/config.yaml unless the installed service requires another path. - Bind only to 127.0.0.1 on port 8317 . - Disable TLS for this localhost-only connection. - Disable remote management and its control panel. - Use ~/.cli-proxy-api as the OAuth auth directory. - Generate a new cryptographically random local API key. Never use an example or predictable key. - Store the client copy in ~/.cli-proxy-api/client.key , not directly in the shell alias. - Set the directory to mode 0700 and all config, key, and OAuth JSON files to mode 0600 . - Keep normal retry defaults and use round-robin routing with session affinity disabled. The effective server config should be equivalent to: host: "127.0.0.1" port: 8317 tls: enable: false cert: "" key: "" remote-management: allow-remote: false secret-key: "" disable-control-panel: true auth-dir: "~/.cli-proxy-api" api-keys: - "GENERATE A RANDOM LOCAL KEY" debug: false logging-to-file: false usage-statistics-enabled: false request-retry: 3 max-retry-credentials: 0 max-retry-interval: 30 routing: strategy: "round-robin" session-affinity: false ws-auth: true 4. Run it as a user service - Prefer the systemd user unit included by the installed CLIProxyAPI package. - If no unit exists, create a user unit whose ExecStart runs the discovered binary with -config %h/.cli-proxy-api/config.yaml , restarts on failure, and starts after the network is available. - Run systemctl --user daemon-reload and enable/start the service. - Verify it is active and listening only on 127.0.0.1:8317 . 5. Authenticate both upstream accounts - Run the installed binary's Codex OAuth flow with the explicit config path. Current CLIProxyAPI builds use: cli-proxy-api -config ~/.cli-proxy-api/config.yaml -codex-login - Let me complete the browser approval when prompted. - Run the Claude OAuth flow similarly: cli-proxy-api -config ~/.cli-proxy-api/config.yaml -claude-login - Let me complete that browser approval too. - After each login, set newly created OAuth JSON files to mode 0600 . - Confirm the service hot-loaded both credentials, restarting it only if necessary. 6. Add only the claudex alias - Add the following logical alias to the correct zsh startup file, adapting paths if my shell or home layout differs: alias claudex='ANTHROPIC BASE URL=http://127.0.0.1:8317 ANTHROPIC AUTH TOKEN="$ <"$HOME/.cli-proxy-api/client.key" " CLAUDE CODE SUBAGENT MODEL=gpt-5.6-sol CLAUDE CODE ALWAYS ENABLE EFFORT=1 CLAUDE CODE MAX TOOL USE CONCURRENCY=3 ENABLE TOOL SEARCH=false claude --model gpt-5.6-sol' - Keep these environment variables invocation-scoped. Do not export them globally and do not add them to ~/.claude/settings.json . - Preserve argument forwarding so commands such as claudex --continue , claudex --resume , and claudex -p "..." work. - Do not redefine or wrap the normal claude or codex commands. 7. Verify the complete setup - An unauthenticated request to http://127.0.0.1:8317/v1/models must be rejected. - An authenticated request using client.key must succeed. - Confirm the returned model catalog contains gpt-5.6-sol and Claude models. - If gpt-5.6-sol is unavailable, stop and tell me; do not silently choose another model. - Run claudex --version to confirm argument forwarding. - Run one minimal request: claudex -p "Reply with exactly: claudex route works" . - Require the exact successful response before declaring completion. - Open a clean shell and prove ANTHROPIC BASE URL and ANTHROPIC AUTH TOKEN are unset globally. - Prove normal claude and codex still resolve exactly as they did before. - Report the final service status and credential permissions without revealing any secrets. Security constraints: - Never expose the proxy beyond localhost. - Never commit, paste, log, or display the generated local key or OAuth credentials. - Do not weaken TLS verification, Claude Code permissions, or sandbox settings. - Do not overwrite whole config files when a narrow merge is possible. - Ask me only for browser OAuth approval or genuinely missing product choices; handle discoverable machine details yourself. ANTHROPIC BASE URL sends this Claude Code invocation to the local Anthropic-compatible proxy. ANTHROPIC AUTH TOKEN authenticates to the local proxy using a protected file. --model gpt-5.6-sol selects the Codex-backed model for the main Claude Code session. CLAUDE CODE SUBAGENT MODEL keeps Claude Code subagents on the same model. CLAUDE CODE ALWAYS ENABLE EFFORT=1 enables effort controls for the custom model. CLAUDE CODE MAX TOOL USE CONCURRENCY=3 caps concurrent tool calls. ENABLE TOOL SEARCH=false disables dynamic tool search on the non-Anthropic gateway. Because all variables are attached to the alias invocation, they do not change the normal claude or codex environment. claudex claudex --continue claudex --resume claudex -p "Explain this repository" Model availability depends on the authenticated Codex account and the CLIProxyAPI version. Do not rename or silently substitute the requested model if it is missing from /v1/models . CLIProxyAPI changes quickly, so check the linked quick-start page before copying a command. brew install cliproxyapi When managed by brew services , Homebrew reads $ brew --prefix /etc/cliproxyapi.conf . The official docs show how to symlink that path to ~/.cli-proxy-api/config.yaml if you want the same layout used in this guide. yay -S cli-proxy-api-bin or paru -S cli-proxy-api-bin The AUR package includes /usr/share/doc/cli-proxy-api-bin/config.example.yaml and a systemd user unit. Create the config before enabling the service. The official quick start currently provides this installer: curl -fsSL https://raw.githubusercontent.com/router-for-me/cliproxyapi-installer/refs/heads/master/cliproxyapi-installer | bash For a safer agent workflow, download the installer to a temporary file, inspect it, and then execute it instead of piping it directly to a shell. Download the appropriate binary from the project's official GitHub releases. Native Windows needs a PowerShell equivalent of the zsh alias; WSL can follow the Linux/zsh flow. CLIProxyAPI repository https://github.com/router-for-me/CLIProxyAPI CLIProxyAPI official quick start and installation https://help.router-for.me/introduction/quick-start CLIProxyAPI basic configuration https://help.router-for.me/configuration/basic CLIProxyAPI example configuration https://github.com/router-for-me/CLIProxyAPI/blob/main/config.example.yaml CLIProxyAPI Codex OAuth https://help.router-for.me/configuration/provider/codex CLIProxyAPI Claude OAuth https://help.router-for.me/configuration/provider/claude-code CLIProxyAPI Claude Code client configuration https://help.router-for.me/agent-client/claude-code Claude Code environment variables https://code.claude.com/docs/en/env-vars Claude Code authentication and credential precedence https://code.claude.com/docs/en/team Claude Code model configuration https://code.claude.com/docs/en/model-config Original https://x.com/theo/status/2076114415368482854 claudex inspiration from Theo