CLI Reference

Complete reference for Claude Code command-line interface.

When to Use

• "What CLI flags are available?"
• "How do I use headless mode?"
• "Claude in automation/CI/CD"
• "Output format options"
• "System prompt via CLI"
• "How do I spawn agents properly?"

Core Commands

Session Control

Headless Mode (Critical for Agents)

Tool Control

Subagent Definition (--agents flag)

Define custom subagents inline via JSON:

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

Agent Fields

Key Insight

When Lead uses Task tool, it auto-spawns from these definitions. No manual spawn needed.

System Prompt Customization

Use --append-system-prompt for most cases - preserves Claude Code capabilities.

Model Selection

Aliases: sonnet, opus, haiku

MCP Configuration

Advanced Flags

Output Formats

JSON (for parsing)

claude -p "query" --output-format json
# {"result": "...", "session_id": "...", "usage": {...}}

Streaming (for real-time monitoring)

claude -p "query" --output-format stream-json
# Newline-delimited JSON events

Structured Output (schema validation)

claude -p "Extract data" \
  --output-format json \
  --json-schema '{"type":"object","properties":{...}}'

Headless Agent Pattern (CRITICAL)

Proper headless agent spawn:

claude -p "$TASK_PROMPT" \
  --session-id "$UUID" \
  --dangerously-skip-permissions \
  --max-turns 100 \
  --output-format stream-json \
  --agents '{...}' \
  --append-system-prompt "Context: ..."

Missing any of these causes hangs:

• --session-id - Track the session
• --dangerously-skip-permissions - Headless requires this
• --max-turns - Prevents infinite loops

Common Patterns

CI/CD Automation

claude -p "Run tests and fix failures" \
  --dangerously-skip-permissions \
  --max-turns 50 \
  --output-format json | jq '.result'

Piped Input

cat error.log | claude -p "Find root cause"
gh pr diff | claude -p "Review for security"

Multi-turn Session

id=$(claude -p "Start task" --output-format json | jq -r '.session_id')
claude -p "Continue" --resume "$id"

Stream Monitoring

claude -p "Long task" \
  --output-format stream-json \
  --include-partial-messages | while read -r line; do
    echo "$line" | jq '.type'
done

Keyboard Shortcuts (Interactive)

Quick Commands