An agent runtime owns one prepared model loop: it receives the prompt, drives model output, handles native tool calls, and returns the finished turn to OpenClaw.

Runtimes are easy to confuse with providers because both show up near model configuration. They are different layers:

A harness is the implementation that provides an agent runtime (code term). For example, the bundled Codex harness implements the codex runtime. Public config uses agentRuntime.id on provider or model entries; whole-agent runtime keys are legacy and ignored. openclaw doctor --fix removes old whole-agent runtime pins and rewrites legacy runtime model refs to canonical provider/model refs plus model-scoped runtime policy where needed.

Two runtime families:

• Embedded harnesses run inside OpenClaw's prepared agent loop: the built-in openclaw runtime, plus registered plugin harnesses such as codex and copilot.
• CLI backends run a local CLI process while keeping the model ref canonical. For example, anthropic/claude-opus-4-8 with a model-scoped agentRuntime.id: "claude-cli" means "select the Anthropic model, execute through Claude CLI." claude-cli is not an embedded harness id and must not be passed to AgentHarness selection.

The copilot harness is a separate, opt-in external plugin harness for the GitHub Copilot CLI; see GitHub Copilot agent runtime for the user-facing decision between PI, Codex, and GitHub Copilot agent runtime.

Codex surfaces

Several surfaces share the Codex name:

These surfaces are intentionally independent. Enabling the codex plugin makes native app-server features available; openclaw doctor --fix owns legacy Codex route repair and stale session pin cleanup. Selecting openai/* for an agent model now means "run this through Codex" unless a non-agent OpenAI API surface is being used.

The common ChatGPT/Codex subscription setup uses Codex OAuth for auth, but keeps the model ref as openai/* and selects the codex runtime:

{
  agents: {
    defaults: {
      model: "openai/gpt-5.6-sol",
    },
  },
}

That means OpenClaw selects an OpenAI model ref, then asks the Codex app-server runtime to run the embedded agent turn. It does not mean "use API billing," and it does not mean the channel, model provider catalog, or OpenClaw session store becomes Codex.

When the bundled codex plugin is enabled, use the native /codex command surface (/codex bind, /codex threads, /codex resume, /codex steer, /codex stop) for natural-language Codex control instead of ACP. Use ACP for Codex only when the user explicitly asks for ACP/acpx or is testing the ACP adapter path. Claude Code, Gemini CLI, OpenCode, Cursor, and similar external harnesses still use ACP.

Decision tree:

1. Codex bind/control/thread/resume/steer/stop -> native /codex command surface when the bundled codex plugin is enabled.
2. Codex as the embedded runtime or the normal subscription-backed Codex agent experience -> openai/<model>.
3. OpenClaw explicitly chosen for an OpenAI model -> keep the model ref as openai/<model> and set provider/model runtime policy to agentRuntime.id: "openclaw". A selected openai OAuth profile is routed internally through OpenClaw's Codex-auth transport.
4. Legacy Codex model refs in config -> repair with openclaw doctor --fix to openai/<model>; doctor keeps the Codex auth route by adding provider/model-scoped agentRuntime.id: "codex" where the old model ref implied it. Legacy codex-cli/* model refs repair to the same openai/<model> Codex app-server route; OpenClaw no longer keeps a bundled Codex CLI backend.
5. ACP, acpx, or Codex ACP adapter explicitly requested -> runtime: "acp" and agentId: "codex".
6. Claude Code, Gemini CLI, OpenCode, Cursor, Droid, or another external harness -> ACP/acpx, not the native sub-agent runtime.

For the OpenAI-family prefix split, see OpenAI and Model providers. For the Codex runtime support contract, see Codex harness runtime.

Runtime ownership

Different runtimes own different amounts of the loop:

Design rule: if OpenClaw owns the surface, it can provide normal plugin hook behavior. If the native runtime owns the surface, OpenClaw needs runtime events or native hooks. If the native runtime owns canonical thread state, OpenClaw mirrors and projects context rather than rewriting unsupported internals.

Runtime selection

OpenClaw resolves an embedded runtime after provider and model resolution, in this order:

1. Model-scoped runtime policy wins. This lives in a configured provider model entry, or in agents.defaults.models["provider/model"].agentRuntime / agents.list[].models["provider/model"].agentRuntime. A provider wildcard such as agents.defaults.models["vllm/*"].agentRuntime applies after exact model policy, so dynamically discovered provider models can share one runtime without overriding exact per-model exceptions.
2. Provider-scoped runtime policy: models.providers.<provider>.agentRuntime.
3. auto mode: registered plugin runtimes can claim supported provider/model pairs.
4. If nothing claims the turn in auto mode, OpenClaw falls back to openclaw as the compatibility runtime. Use an explicit runtime id when the run must be strict.

Whole-session and whole-agent runtime pins are ignored: OPENCLAW_AGENT_RUNTIME, session agentHarnessId/agentRuntimeOverride state, agents.defaults.agentRuntime, and agents.list[].agentRuntime. Run openclaw doctor --fix to remove stale whole-agent runtime config and convert legacy runtime model refs where intent can be preserved.

Explicit provider/model plugin runtimes fail closed: agentRuntime.id: "codex" on a provider or model means Codex, or a clear selection/runtime error - it is never silently routed back to OpenClaw. Only auto may route an unmatched turn to OpenClaw.

CLI backend aliases differ from embedded harness ids. Preferred Claude CLI form:

{
  agents: {
    defaults: {
      model: "anthropic/claude-opus-4-8",
      models: {
        "anthropic/claude-opus-4-8": {
          agentRuntime: { id: "claude-cli" },
        },
      },
    },
  },
}

Legacy refs such as claude-cli/claude-opus-4-7 remain supported for compatibility, but new config should keep the provider/model canonical and put the execution backend in provider/model runtime policy.

Legacy codex-cli/* refs are different: doctor migrates them to openai/* so they run through the Codex app-server harness instead of preserving a Codex CLI backend.

auto mode is intentionally conservative for most providers. OpenAI agent models are the exception: unset runtime and auto both resolve to the Codex harness. Explicit OpenClaw runtime config remains an opt-in compatibility route for openai/* agent turns; when paired with a selected openai OAuth profile, OpenClaw routes that path internally through the Codex-auth transport while keeping the public model ref as openai/*. Stale OpenAI runtime session pins are ignored by runtime selection and can be cleaned with openclaw doctor --fix.

If openclaw doctor warns that the codex plugin is enabled while legacy Codex model refs remain in config, treat that as legacy route state and run openclaw doctor --fix to rewrite it to openai/* with the Codex runtime.

GitHub Copilot agent runtime

The external @openclaw/copilot plugin registers an opt-in copilot runtime backed by the GitHub Copilot CLI (@github/copilot-sdk). It claims the canonical subscription github-copilot provider and is never selected by auto. Opt in per-model or per-provider via agentRuntime.id:

{
  agents: {
    defaults: {
      model: "github-copilot/gpt-5.5",
      models: {
        "github-copilot/gpt-5.5": {
          agentRuntime: { id: "copilot" },
        },
      },
    },
  },
}

The harness claims its provider, runtime, CLI session key, and auth profile prefix in extensions/copilot/doctor-contract-api.ts, which openclaw doctor auto-loads. For configuration, auth, transcript mirroring, compaction, the declarative doctor contract, and the broader PI vs Codex vs Copilot SDK decision, see GitHub Copilot agent runtime.

Compatibility contract

When a runtime is not OpenClaw, its docs should state which OpenClaw surfaces it supports:

The Codex runtime support contract is documented in Codex harness runtime.

Status labels

Status output can show both Execution and Runtime labels. Read them as diagnostics, not provider names:

• A model ref such as openai/gpt-5.6-sol is the selected provider/model.
• A runtime id such as codex is the loop executing the turn.
• A channel label such as Telegram or Discord is where the conversation is happening.

If a run shows an unexpected runtime, inspect the selected provider/model runtime policy first. Legacy session runtime pins no longer decide routing.

Related

• Codex harness
• Codex harness runtime
• GitHub Copilot agent runtime
• OpenAI
• Agent harness plugins
• Agent loop
• Models
• Status

Source: docs/concepts/agent-runtimes.md