---
title: "CLI Configuration"
description: "Configure default settings for the Arc CLI with cli.toml"
---

Arc loads CLI defaults from `~/.arc/cli.toml` so you don't have to pass common flags every time. The file is optional — if it doesn't exist, built-in defaults are used.

## File location

The default path is `~/.arc/cli.toml`. Arc silently skips loading if the file is missing.

## Precedence

CLI flags always take the highest priority:

1. **CLI flags** — always win
2. **`cli.toml`** — used when no flag is provided
3. **Built-in defaults** — used when neither flag nor config is set

## Full example

```toml title="cli.toml"
mode = "server"

[server]
base_url = "https://arc.example.com:3000"

[server.tls]
cert = "~/.arc/tls/client.crt"
key = "~/.arc/tls/client.key"
ca = "~/.arc/tls/ca.crt"

[agent]
provider = "anthropic"
model = "claude-opus-4-6"
permissions = "read-write"
output_format = "text"

[llm]
model = "claude-sonnet-4-5"
```

All fields are optional. You can include just the sections and keys you want to override.

## `[agent]` section

Defaults for `arc agent` sessions.

| Key | Description | Values | Default |
|---|---|---|---|
| `provider` | LLM provider | `"anthropic"`, `"openai"`, `"gemini"`, etc. | `"anthropic"` |
| `model` | Model name | Any model ID from `arc model list` | Per provider |
| `permissions` | Tool permission level | `"read-only"`, `"read-write"`, `"full"` | `"read-write"` |
| `output_format` | Output format | `"text"`, `"json"` | `"text"` |

### Permission levels

- **`read-only`** — auto-approves read tools (`read_file`, `grep`, `glob`, `list_dir`) and subagent tools
- **`read-write`** — adds write tools (`write_file`, `edit_file`, `apply_patch`)
- **`full`** — allows all tools including shell commands

Tools outside the permission level are interactively prompted (if a TTY is present) or denied (with `--auto-approve`).

### Output formats

- **`text`** — human-readable terminal output
- **`json`** — NDJSON event stream

## `[llm]` section

Defaults for `arc llm prompt` and `arc llm chat`.

| Key | Description | Values | Default |
|---|---|---|---|
| `model` | Model name | Any model ID from `arc model list` | Per provider |

<Note>
The `[llm]` section only sets the default model. Use `[agent]` to configure provider, permissions, and output format for `arc agent`.
</Note>

## `mode`

Controls whether commands run in-process or delegate to a running Arc API server.

| Value | Description |
|---|---|
| `"standalone"` | Execute locally (default) |
| `"server"` | Delegate to an Arc API server |

Override with the `--mode` CLI flag:

```bash
arc --mode server models list
```

## `[server]` section

Configuration for server mode.

| Key | Description | Default |
|---|---|---|
| `base_url` | Server URL | `"http://localhost:3000"` |

Override the URL with the `--server-url` CLI flag:

```bash
arc --mode server --server-url https://arc.example.com:3000 models list
```

### `[server.tls]` section

Optional mTLS configuration for authenticating with the server. When present, the CLI presents a client certificate during the TLS handshake.

| Key | Description |
|---|---|
| `cert` | Path to client certificate PEM file |
| `key` | Path to client private key PEM file |
| `ca` | Path to CA certificate PEM file (to verify the server) |

Paths support `~/` expansion. Example:

```toml title="cli.toml"
[server.tls]
cert = "~/.arc/tls/client.crt"
key = "~/.arc/tls/client.key"
ca = "~/.arc/tls/ca.crt"
```