CLI reference ↗

Documentation Index#

Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt Use this file to discover all available pages before exploring further.

Complete reference for Claude Code command-line interface, including commands and flags.

CLI commands#

You can start sessions, pipe content, resume conversations, and manage updates with these commands:

CLI flags#

Customize Claude Code’s behavior with these command-line flags:

The --output-format json flag is particularly useful for scripting and automation, allowing you to parse Claude’s responses programmatically.

Agents flag format#

The --agents flag accepts a JSON object that defines one or more custom subagents. Each subagent requires a unique name (as the key) and a definition object with the following fields:

Example:

claude --agents '{
  "code-reviewer": {
    "description": "Expert code reviewer. Use proactively after code changes.",
    "prompt": "You are a senior code reviewer. Focus on code quality, security, and best practices.",
    "tools": ["Read", "Grep", "Glob", "Bash"],
    "model": "sonnet"
  },
  "debugger": {
    "description": "Debugging specialist for errors and test failures.",
    "prompt": "You are an expert debugger. Analyze errors, identify root causes, and provide fixes."
  }
}'

For more details on creating and using subagents, see the subagents documentation.

System prompt flags#

Claude Code provides four flags for customizing the system prompt, each serving a different purpose:

When to use each:

• --system-prompt: use when you need complete control over Claude’s system prompt. This removes all default Claude Code instructions, giving you a blank slate.

  claude --system-prompt "You are a Python expert who only writes type-annotated code"

• --system-prompt-file: use when you want to load a custom prompt from a file, useful for team consistency or version-controlled prompt templates.

  claude -p --system-prompt-file ./prompts/code-review.txt "Review this PR"

• --append-system-prompt: use when you want to add specific instructions while keeping Claude Code’s default capabilities intact. This is the safest option for most use cases.

  claude --append-system-prompt "Always use TypeScript and include JSDoc comments"

• --append-system-prompt-file: use when you want to append instructions from a file while keeping Claude Code’s defaults. Useful for version-controlled additions.

  claude -p --append-system-prompt-file ./prompts/style-rules.txt "Review this PR"

--system-prompt and --system-prompt-file are mutually exclusive. The append flags can be used together with either replacement flag.

For most use cases, --append-system-prompt or --append-system-prompt-file is recommended as they preserve Claude Code’s built-in capabilities while adding your custom requirements. Use --system-prompt or --system-prompt-file only when you need complete control over the system prompt.

See also#

• Chrome extension - Browser automation and web testing
• Interactive mode - Shortcuts, input modes, and interactive features
• Quickstart guide - Getting started with Claude Code
• Common workflows - Advanced workflows and patterns
• Settings - Configuration options
• Agent SDK documentation - Programmatic usage and integrations