--- title: "Codex Harness" summary: "Run OpenClaw embedded agent turns through the bundled Codex app-server harness" read_when: - You want to use the bundled Codex app-server harness - You need Codex model refs and config examples - You want to disable PI fallback for Codex-only deployments --- # Codex Harness The bundled `codex` plugin lets OpenClaw run embedded agent turns through the Codex app-server instead of the built-in PI harness. Use this when you want Codex to own the low-level agent session: model discovery, native thread resume, native compaction, and app-server execution. OpenClaw still owns chat channels, session files, model selection, tools, approvals, media delivery, and the visible transcript mirror. The harness is off by default. It is selected only when the `codex` plugin is enabled and the resolved model is a `codex/*` model, or when you explicitly force `embeddedHarness.runtime: "codex"` or `OPENCLAW_AGENT_RUNTIME=codex`. If you never configure `codex/*`, existing PI, OpenAI, Anthropic, Gemini, local, and custom-provider runs keep their current behavior. ## Pick the right model prefix OpenClaw has separate routes for OpenAI and Codex-shaped access: | Model ref | Runtime path | Use when | | ---------------------- | -------------------------------------------- | ----------------------------------------------------------------------- | | `openai/gpt-5.4` | OpenAI provider through OpenClaw/PI plumbing | You want direct OpenAI Platform API access with `OPENAI_API_KEY`. | | `openai-codex/gpt-5.4` | OpenAI Codex OAuth provider through PI | You want ChatGPT/Codex OAuth without the Codex app-server harness. | | `codex/gpt-5.4` | Bundled Codex provider plus Codex harness | You want native Codex app-server execution for the embedded agent turn. | The Codex harness only claims `codex/*` model refs. Existing `openai/*`, `openai-codex/*`, Anthropic, Gemini, xAI, local, and custom provider refs keep their normal paths. ## Requirements - OpenClaw with the bundled `codex` plugin available. - Codex app-server `0.118.0` or newer. - Codex auth available to the app-server process. The plugin blocks older or unversioned app-server handshakes. That keeps OpenClaw on the protocol surface it has been tested against. For live and Docker smoke tests, auth usually comes from `OPENAI_API_KEY`, plus optional Codex CLI files such as `~/.codex/auth.json` and `~/.codex/config.toml`. Use the same auth material your local Codex app-server uses. ## Minimal config Use `codex/gpt-5.4`, enable the bundled plugin, and force the `codex` harness: ```json5 { plugins: { entries: { codex: { enabled: true, }, }, }, agents: { defaults: { model: "codex/gpt-5.4", embeddedHarness: { runtime: "codex", fallback: "none", }, }, }, } ``` If your config uses `plugins.allow`, include `codex` there too: ```json5 { plugins: { allow: ["codex"], entries: { codex: { enabled: true, }, }, }, } ``` Setting `agents.defaults.model` or an agent model to `codex/` also auto-enables the bundled `codex` plugin. The explicit plugin entry is still useful in shared configs because it makes the deployment intent obvious. ## Add Codex without replacing other models Keep `runtime: "auto"` when you want Codex for `codex/*` models and PI for everything else: ```json5 { plugins: { entries: { codex: { enabled: true, }, }, }, agents: { defaults: { model: { primary: "codex/gpt-5.4", fallbacks: ["openai/gpt-5.4", "anthropic/claude-opus-4-6"], }, models: { "codex/gpt-5.4": { alias: "codex" }, "codex/gpt-5.4-mini": { alias: "codex-mini" }, "openai/gpt-5.4": { alias: "gpt" }, "anthropic/claude-opus-4-6": { alias: "opus" }, }, embeddedHarness: { runtime: "auto", fallback: "pi", }, }, }, } ``` With this shape: - `/model codex` or `/model codex/gpt-5.4` uses the Codex app-server harness. - `/model gpt` or `/model openai/gpt-5.4` uses the OpenAI provider path. - `/model opus` uses the Anthropic provider path. - If a non-Codex model is selected, PI remains the compatibility harness. ## Codex-only deployments Disable PI fallback when you need to prove that every embedded agent turn uses the Codex harness: ```json5 { agents: { defaults: { model: "codex/gpt-5.4", embeddedHarness: { runtime: "codex", fallback: "none", }, }, }, } ``` Environment override: ```bash OPENCLAW_AGENT_RUNTIME=codex \ OPENCLAW_AGENT_HARNESS_FALLBACK=none \ openclaw gateway run ``` With fallback disabled, OpenClaw fails early if the Codex plugin is disabled, the requested model is not a `codex/*` ref, the app-server is too old, or the app-server cannot start. ## Per-agent Codex You can make one agent Codex-only while the default agent keeps normal auto-selection: ```json5 { agents: { defaults: { embeddedHarness: { runtime: "auto", fallback: "pi", }, }, list: [ { id: "main", default: true, model: "anthropic/claude-opus-4-6", }, { id: "codex", name: "Codex", model: "codex/gpt-5.4", embeddedHarness: { runtime: "codex", fallback: "none", }, }, ], }, } ``` Use normal session commands to switch agents and models. `/new` creates a fresh OpenClaw session and the Codex harness creates or resumes its sidecar app-server thread as needed. `/reset` clears the OpenClaw session binding for that thread. ## Model discovery By default, the Codex plugin asks the app-server for available models. If discovery fails or times out, it uses the bundled fallback catalog: - `codex/gpt-5.4` - `codex/gpt-5.4-mini` - `codex/gpt-5.2` You can tune discovery under `plugins.entries.codex.config.discovery`: ```json5 { plugins: { entries: { codex: { enabled: true, config: { discovery: { enabled: true, timeoutMs: 2500, }, }, }, }, }, } ``` Disable discovery when you want startup to avoid probing Codex and stick to the fallback catalog: ```json5 { plugins: { entries: { codex: { enabled: true, config: { discovery: { enabled: false, }, }, }, }, }, } ``` ## Tools, media, and compaction The Codex harness changes the low-level embedded agent executor only. OpenClaw still builds the tool list and receives dynamic tool results from the harness. Text, images, video, music, TTS, approvals, and messaging-tool output continue through the normal OpenClaw delivery path. When the selected model uses the Codex harness, native thread compaction is delegated to Codex app-server. OpenClaw keeps a transcript mirror for channel history, search, `/new`, `/reset`, and future model or harness switching. Media generation does not require PI. Image, video, music, PDF, TTS, and media understanding continue to use the matching provider/model settings such as `agents.defaults.imageGenerationModel`, `videoGenerationModel`, `pdfModel`, and `messages.tts`. ## Troubleshooting **Codex does not appear in `/model`:** enable `plugins.entries.codex.enabled`, set a `codex/*` model ref, or check whether `plugins.allow` excludes `codex`. **OpenClaw falls back to PI:** set `embeddedHarness.fallback: "none"` or `OPENCLAW_AGENT_HARNESS_FALLBACK=none` while testing. **The app-server is rejected:** upgrade Codex so the app-server handshake reports version `0.118.0` or newer. **Model discovery is slow:** lower `plugins.entries.codex.config.discovery.timeoutMs` or disable discovery. **A non-Codex model uses PI:** that is expected. The Codex harness only claims `codex/*` model refs. ## Related - [Agent Harness Plugins](/plugins/sdk-agent-harness) - [Model Providers](/concepts/model-providers) - [Configuration Reference](/gateway/configuration-reference) - [Testing](/help/testing#live-codex-app-server-harness-smoke)