---
summary: "CLI backends: local AI CLI fallback with optional MCP tool bridge"
read_when:
  - You want a reliable fallback when API providers fail
  - You are running local AI CLIs and want to reuse them
  - You want to understand the MCP loopback bridge for CLI backend tool access
title: "CLI backends"
---

OpenClaw can run **local AI CLIs** as a **text-only fallback** when API providers are down,
rate-limited, or temporarily misbehaving. This is intentionally conservative:

- **OpenClaw tools are not injected directly**, but backends with `bundleMcp: true`
  can receive gateway tools via a loopback MCP bridge.
- **JSONL streaming** for CLIs that support it.
- **Sessions are supported** (so follow-up turns stay coherent).
- **Images can be passed through** if the CLI accepts image paths.

This is designed as a **safety net** rather than a primary path. Use it when you
want "always works" text responses without relying on external APIs.

If you want a full harness runtime with ACP session controls, background tasks,
thread/conversation binding, and persistent external coding sessions, use
[ACP Agents](/tools/acp-agents) instead. CLI backends are not ACP.

<Tip>
  Building a new backend plugin? Use
  [CLI backend plugins](/plugins/cli-backend-plugins). This page is for users
  configuring and operating an already registered backend.
</Tip>

## Beginner-friendly quick start

You can use Claude Code CLI **without any config** (the bundled Anthropic plugin
registers a default backend):

```bash
openclaw agent --agent main --message "hi" --model claude-cli/claude-sonnet-4-6
```

`main` is the default agent id when no explicit agent list is configured. If
you use multiple agents, replace it with the agent id you want to run.

If your gateway runs under launchd/systemd and PATH is minimal, add just the
command path:

```json5
{
  agents: {
    defaults: {
      cliBackends: {
        "claude-cli": {
          command: "/opt/homebrew/bin/claude",
        },
      },
    },
  },
}
```

That's it. No keys, no extra auth config needed beyond the CLI itself.

If you use a bundled CLI backend as the **primary message provider** on a
gateway host, OpenClaw now auto-loads the owning bundled plugin when your config
explicitly references that backend in a model ref or under
`agents.defaults.cliBackends`.

## Using it as a fallback

Add a CLI backend to your fallback list so it only runs when primary models fail:

```json5
{
  agents: {
    defaults: {
      model: {
        primary: "anthropic/claude-opus-4-6",
        fallbacks: ["claude-cli/claude-sonnet-4-6"],
      },
      models: {
        "anthropic/claude-opus-4-6": { alias: "Opus" },
        "claude-cli/claude-sonnet-4-6": {},
      },
    },
  },
}
```

Notes:

- If you use `agents.defaults.models` (allowlist), you must include your CLI backend models there too.
- If the primary provider fails (auth, rate limits, timeouts), OpenClaw will
  try the CLI backend next.

## Configuration overview

All CLI backends live under:

```
agents.defaults.cliBackends
```

Each entry is keyed by a **provider id** (e.g. `claude-cli`, `my-cli`).
The provider id becomes the left side of your model ref:

```
<provider>/<model>
```

### Example configuration

```json5
{
  agents: {
    defaults: {
      cliBackends: {
        "my-cli": {
          command: "my-cli",
          args: ["--json"],
          output: "json",
          input: "arg",
          modelArg: "--model",
          modelAliases: {
            "claude-opus-4-6": "opus",
            "claude-sonnet-4-6": "sonnet",
          },
          sessionArg: "--session",
          sessionMode: "existing",
          sessionIdFields: ["session_id", "conversation_id"],
          systemPromptArg: "--system",
          // For CLIs with a dedicated prompt-file flag:
          // systemPromptFileArg: "--system-file",
          // Codex-style CLIs can point at a prompt file instead:
          // systemPromptFileConfigArg: "-c",
          // systemPromptFileConfigKey: "model_instructions_file",
          systemPromptWhen: "first",
          imageArg: "--image",
          imageMode: "repeat",
          // Opt in only if this backend may reseed safe invalidated sessions
          // from bounded raw OpenClaw transcript history before compaction.
          reseedFromRawTranscriptWhenUncompacted: true,
          serialize: true,
        },
      },
    },
  },
}
```

## How it works

1. **Selects a backend** based on the provider prefix (`claude-cli/...`).
2. **Builds a system prompt** using the same OpenClaw prompt + workspace context.
3. **Executes the CLI** with a session id (if supported) so history stays consistent.
   The bundled `claude-cli` backend keeps a Claude stdio process alive per
   OpenClaw session and sends follow-up turns over stream-json stdin.
4. **Parses output** (JSON or plain text) and returns the final text.
5. **Persists session ids** per backend, so follow-ups reuse the same CLI session.

<Note>
The bundled Anthropic `claude-cli` backend is supported again. Anthropic staff
told us OpenClaw-style Claude CLI usage is allowed again, so OpenClaw treats
`claude -p` usage as sanctioned for this integration unless Anthropic publishes
a new policy.
</Note>

The bundled Anthropic `claude-cli` backend prefers Claude Code's native skill
resolver for OpenClaw skills. When the current skills snapshot includes at least
one selected skill with a materialized path, OpenClaw passes a temporary Claude
Code plugin with `--plugin-dir` and omits the duplicate OpenClaw skills catalog
from the appended system prompt. If the snapshot has no materialized plugin
skill, OpenClaw keeps the prompt catalog as a fallback. Skill env/API key
overrides are still applied by OpenClaw to the child process environment for the
run.

Claude CLI also has its own noninteractive permission mode. OpenClaw maps that
to the existing exec policy instead of adding Claude-specific policy config.
For OpenClaw-managed Claude live sessions, the effective OpenClaw exec policy is
authoritative: YOLO (`tools.exec.security: "full"` and
`tools.exec.ask: "off"`) launches Claude with
`--permission-mode bypassPermissions`, while restrictive effective exec policy
launches Claude with `--permission-mode default`. Per-agent
`agents.list[].tools.exec` settings override global `tools.exec` for that
agent. Raw Claude backend args may still include `--permission-mode`, but live
Claude launches normalize that flag to match the effective OpenClaw exec policy.

The bundled Anthropic `claude-cli` backend also maps OpenClaw `/think` levels
to Claude Code's native `--effort` flag for non-off levels. `minimal` and
`low` map to `low`, `adaptive` and `medium` map to `medium`, and `high`,
`xhigh`, and `max` map directly. Other CLI backends need their owning plugin to
declare an equivalent argv mapper before `/think` can affect the spawned CLI.

Before OpenClaw can use the bundled `claude-cli` backend, Claude Code itself
must already be logged in on the same host:

```bash
claude auth login
claude auth status --text
openclaw models auth login --provider anthropic --method cli --set-default
```

Use `agents.defaults.cliBackends.claude-cli.command` only when the `claude`
binary is not already on `PATH`.

## Sessions

- If the CLI supports sessions, set `sessionArg` (e.g. `--session-id`) or
  `sessionArgs` (placeholder `{sessionId}`) when the ID needs to be inserted
  into multiple flags.
- If the CLI uses a **resume subcommand** with different flags, set
  `resumeArgs` (replaces `args` when resuming) and optionally `resumeOutput`
  (for non-JSON resumes).
- `sessionMode`:
  - `always`: always send a session id (new UUID if none stored).
  - `existing`: only send a session id if one was stored before.
  - `none`: never send a session id.
- `claude-cli` defaults to `liveSession: "claude-stdio"`, `output: "jsonl"`,
  and `input: "stdin"` so follow-up turns reuse the live Claude process while
  it is active. Warm stdio is the default now, including for custom configs
  that omit transport fields. If the Gateway restarts or the idle process
  exits, OpenClaw resumes from the stored Claude session id. Stored session
  ids are verified against an existing readable project transcript before
  resume, so phantom bindings are cleared with `reason=transcript-missing`
  instead of silently starting a fresh Claude CLI session under `--resume`.
- Claude live sessions keep bounded JSONL output guards. Defaults allow up to
  8 MiB and 20,000 raw JSONL lines per turn. Tool-heavy Claude turns can raise
  them per backend with
  `agents.defaults.cliBackends.claude-cli.reliability.outputLimits.maxTurnRawChars`
  and `maxTurnLines`; OpenClaw clamps those settings to 64 MiB and 100,000
  lines.
- Stored CLI sessions are provider-owned continuity. The implicit daily session
  reset does not cut them; `/reset` and explicit `session.reset` policies still
  do.
- Fresh CLI sessions normally reseed only from OpenClaw's compaction summary
  plus post-compaction tail. To recover short sessions that are invalidated
  before compaction, a backend can opt in with
  `reseedFromRawTranscriptWhenUncompacted: true`. OpenClaw still keeps raw
  transcript reseed bounded and limits it to safe invalidations such as missing
  CLI transcripts, system-prompt/MCP changes, or session-expired retry; auth
  profile or credential-epoch changes never reseed raw transcript history.

Serialization notes:

- `serialize: true` keeps same-lane runs ordered.
- Most CLIs serialize on one provider lane.
- OpenClaw drops stored CLI session reuse when the selected auth identity changes,
  including a changed auth profile id, static API key, static token, or OAuth
  account identity when the CLI exposes one. OAuth access and refresh token
  rotation does not cut the stored CLI session. If a CLI does not expose a
  stable OAuth account id, OpenClaw lets that CLI enforce resume permissions.

## Fallback prelude from claude-cli sessions

When a `claude-cli` attempt fails over to a non-CLI candidate in
[`agents.defaults.model.fallbacks`](/concepts/model-failover), OpenClaw seeds
the next attempt with a context prelude harvested from Claude Code's local
JSONL transcript at `~/.claude/projects/`. Without this seed, the fallback
provider would start cold because OpenClaw's own session transcript is empty
for `claude-cli` runs.

- The prelude prefers the latest `/compact` summary or `compact_boundary`
  marker, then appends the most recent post-boundary turns up to a char
  budget. Pre-boundary turns are dropped because the summary already represents
  them.
- Tool blocks are coalesced to compact `(tool call: name)` and
  `(tool result: …)` hints to keep the prompt budget honest. The summary is
  labeled `(truncated)` if it overflows.
- Same-provider `claude-cli` to `claude-cli` fallbacks rely on Claude's own
  `--resume` and skip the prelude.
- The seed reuses the existing Claude session-file path validation, so
  arbitrary paths cannot be read.

## Images (pass-through)

If your CLI accepts image paths, set `imageArg`:

```json5
imageArg: "--image",
imageMode: "repeat"
```

OpenClaw will write base64 images to temp files. If `imageArg` is set, those
paths are passed as CLI args. If `imageArg` is missing, OpenClaw appends the
file paths to the prompt (path injection), which is enough for CLIs that auto-
load local files from plain paths.

## Inputs / outputs

- `output: "json"` (default) tries to parse JSON and extract text + session id.
- For Gemini CLI JSON output, OpenClaw reads reply text from `response` and usage
  from `stats` when `usage` is missing or empty. The bundled Gemini CLI default
  uses `stream-json`, but old `--output-format json` overrides still use the
  JSON parser.
- `output: "jsonl"` parses JSONL streams and extracts the final agent message plus session
  identifiers when present.
- `output: "text"` treats stdout as the final response.

Input modes:

- `input: "arg"` (default) passes the prompt as the last CLI arg.
- `input: "stdin"` sends the prompt via stdin.
- If the prompt is very long and `maxPromptArgChars` is set, stdin is used.

## Defaults (plugin-owned)

Bundled CLI backend defaults live with their owning plugin. For example,
Anthropic owns `claude-cli` and Google owns `google-gemini-cli`. OpenAI Codex
agent runs use the Codex app-server harness through `openai/*`; OpenClaw no
longer registers a bundled `codex-cli` backend.

The bundled Anthropic plugin registers a default for `claude-cli`:

- `command: "claude"`
- `args: ["-p","--output-format","stream-json","--include-partial-messages","--verbose", ...]`
- `output: "jsonl"`
- `input: "stdin"`
- `modelArg: "--model"`
- `sessionMode: "always"`

The bundled Google plugin also registers a default for `google-gemini-cli`:

- `command: "gemini"`
- `args: ["--skip-trust", "--approval-mode", "auto_edit", "--output-format", "stream-json", "--prompt", "{prompt}"]`
- `resumeArgs: ["--skip-trust", "--approval-mode", "auto_edit", "--resume", "{sessionId}", "--output-format", "stream-json", "--prompt", "{prompt}"]`
- `output: "jsonl"`
- `resumeOutput: "jsonl"`
- `jsonlDialect: "gemini-stream-json"`
- `imageArg: "@"`
- `imagePathScope: "workspace"`
- `modelArg: "--model"`
- `sessionMode: "existing"`
- `sessionIdFields: ["session_id", "sessionId"]`

Prerequisite: the local Gemini CLI must be installed and available as
`gemini` on `PATH` (`brew install gemini-cli` or
`npm install -g @google/gemini-cli`).

Gemini CLI output notes:

- The default `stream-json` parser reads assistant `message` events, tool events,
  final `result` usage, and fatal Gemini error events.
- If you override Gemini args to `--output-format json`, OpenClaw normalizes that
  backend back to `output: "json"` and reads reply text from the JSON `response`
  field.
- Usage falls back to `stats` when `usage` is absent or empty.
- `stats.cached` is normalized into OpenClaw `cacheRead`.
- If `stats.input` is missing, OpenClaw derives input tokens from
  `stats.input_tokens - stats.cached`.

Override only if needed (common: absolute `command` path).

## Plugin-owned defaults

CLI backend defaults are now part of the plugin surface:

- Plugins register them with `api.registerCliBackend(...)`.
- The backend `id` becomes the provider prefix in model refs.
- User config in `agents.defaults.cliBackends.<id>` still overrides the plugin default.
- Backend-specific config cleanup stays plugin-owned through the optional
  `normalizeConfig` hook.

Plugins that need tiny prompt/message compatibility shims can declare
bidirectional text transforms without replacing a provider or CLI backend:

```typescript
api.registerTextTransforms({
  input: [
    { from: /red basket/g, to: "blue basket" },
    { from: /paper ticket/g, to: "digital ticket" },
    { from: /left shelf/g, to: "right shelf" },
  ],
  output: [
    { from: /blue basket/g, to: "red basket" },
    { from: /digital ticket/g, to: "paper ticket" },
    { from: /right shelf/g, to: "left shelf" },
  ],
});
```

`input` rewrites the system prompt and user prompt passed to the CLI. `output`
rewrites streamed assistant deltas and parsed final text before OpenClaw handles
its own control markers and channel delivery.

For CLIs that emit provider-specific JSONL events, set `jsonlDialect` on that
backend's config. Supported dialects are `claude-stream-json` for Claude
Code-compatible streams and `gemini-stream-json` for Gemini CLI `stream-json`
events.

## Native compaction ownership

Some CLI backends run an agent that compacts its **own** transcript, so OpenClaw must
not run its safeguard summarizer against them - doing so fights the backend's own
compaction and can hard-fail the turn.

`claude-cli` has no harness endpoint - Claude Code compacts internally - so it declares
`ownsNativeCompaction: true`, and OpenClaw returns a no-op from the compaction path.
Native-harness sessions such as Codex keep routing to their harness compaction endpoint
instead.

Because the backend owns compaction, the old stopgap of setting
`contextTokens: 1_000_000` purely to keep OpenClaw's safeguard from firing on a
claude-cli session is **no longer needed** - the opt-out replaces it.

```typescript
api.registerCliBackend({ id: "my-cli", ownsNativeCompaction: true /* ... */ });
```

Only declare `ownsNativeCompaction` for a backend that genuinely owns its compaction: it
must reliably bound its own transcript as it nears its context window and persist a
resumable session (e.g. `--resume` / `--session-id`); otherwise a deferred session can
stay over budget. Matching `agentHarnessId` sessions still route to the harness endpoint.

## Bundle MCP overlays

CLI backends do **not** receive OpenClaw tool calls directly, but a backend can
opt into a generated MCP config overlay with `bundleMcp: true`.

Current bundled behavior:

- `claude-cli`: generated strict MCP config file
- `google-gemini-cli`: generated Gemini system settings file

When bundle MCP is enabled, OpenClaw:

- spawns a loopback HTTP MCP server that exposes gateway tools to the CLI process
- authenticates the bridge with a per-session token (`OPENCLAW_MCP_TOKEN`)
- scopes tool access to the current session, account, and channel context
- loads enabled bundle-MCP servers for the current workspace
- merges them with any existing backend MCP config/settings shape
- rewrites the launch config using the backend-owned integration mode from the owning extension

If no MCP servers are enabled, OpenClaw still injects a strict config when a
backend opts into bundle MCP so background runs stay isolated.

Session-scoped bundled MCP runtimes are cached for reuse within a session, then
reaped after `mcp.sessionIdleTtlMs` milliseconds of idle time (default 10
minutes; set `0` to disable). One-shot embedded runs such as auth probes,
slug generation, and active-memory recall request cleanup at run end so stdio
children and Streamable HTTP/SSE streams do not outlive the run.

## Reseed history cap

When a fresh CLI session is seeded from a prior OpenClaw transcript (for
example after a `session_expired` retry), the rendered
`<conversation_history>` block is capped to keep reseed prompts from
exploding. The default is `12288` characters (about 3000 tokens).

Claude CLI backends automatically use a larger cap derived from the resolved
Claude context tier. Standard 200K-token Claude runs keep a larger transcript
slice, and 1M-token Claude runs keep a larger slice again, while other CLI
backends keep the conservative default.

- The cap only governs the reseed prompt's prior-history block. Live-session
  output limits are tuned separately under `reliability.outputLimits`
  (see [Sessions](#sessions)).

## Limitations

- **No direct OpenClaw tool calls.** OpenClaw does not inject tool calls into
  the CLI backend protocol. Backends only see gateway tools when they opt into
  `bundleMcp: true`.
- **Streaming is backend-specific.** Some backends stream JSONL; others buffer
  until exit.
- **Structured outputs** depend on the CLI's JSON format.

## Troubleshooting

- **CLI not found**: set `command` to a full path.
- **Wrong model name**: use `modelAliases` to map `provider/model` → CLI model.
- **No session continuity**: ensure `sessionArg` is set and `sessionMode` is not
  `none`.
- **Images ignored**: set `imageArg` (and verify CLI supports file paths).

## Related

- [Gateway runbook](/gateway)
- [Local models](/gateway/local-models)
