claude-code-headless

Claude Code Headless Mode

Run Claude Code from scripts without interactive UI.

Quick Start

# Basic headless execution
claude -p "Explain this code" --allowedTools "Read,Grep"

# JSON output for parsing
claude -p "List files" --output-format json

# Continue conversation
claude -p "Start analysis" --output-format json > result.json
session=$(jq -r '.session_id' result.json)
claude --resume "$session" "Now fix the issues"

Essential CLI Options

| Flag | Description | |------|-------------| | -p, --print | Non-interactive (headless) mode | | --output-format | text, json, stream-json | | -r, --resume | Resume by session ID | | -c, --continue | Continue most recent session | | --allowedTools | Comma-separated allowed tools | | --disallowedTools | Comma-separated denied tools | | --mcp-config | Path to MCP server config JSON | | --verbose | Enable verbose logging | | --append-system-prompt | Add to system prompt |

Permission Modes

| Mode | Flag | Effect | |------|------|--------| | Default | (none) | Prompt for permissions | | Accept edits | --permission-mode acceptEdits | Auto-accept file changes | | Bypass | --permission-mode bypassPermissions | Skip all prompts |

Output Formats

Text (default)

claude -p "Hello"
# Outputs: Human-readable response

JSON

claude -p "Hello" --output-format json

{
  "type": "result",
  "subtype": "success",
  "result": "Hello! How can I help?",
  "session_id": "abc123",
  "total_cost_usd": 0.001,
  "duration_ms": 1234,
  "num_turns": 1
}

Stream-JSON

claude -p "Hello" --output-format stream-json
# Real-time JSONL output for each message

Common Patterns

Script with tool restrictions

claude -p "Analyze the codebase" \
  --allowedTools "Read,Grep,Glob" \
  --disallowedTools "Write,Edit,Bash"

CI/CD integration

claude -p "Review this PR diff" \
  --permission-mode acceptEdits \
  --output-format json \
  --append-system-prompt "Focus on security issues"

Multi-turn automation

session=$(claude -p "Start task" --output-format json | jq -r '.session_id')
claude --resume "$session" "Continue with step 2"
claude --resume "$session" "Finalize and report"

Error Handling

result=$(claude -p "Task" --output-format json)
if [[ $(echo "$result" | jq -r '.is_error') == "true" ]]; then
    echo "Error: $(echo "$result" | jq -r '.result')" >&2
    exit 1
fi

Official Documentation

• https://code.claude.com/docs/en/headless - Headless mode reference
• https://code.claude.com/docs/en/settings - Settings and permissions

Additional Resources

• ./references/cli-options.md - Complete CLI flag reference
• ./references/output-formats.md - Output format schemas
• ./references/integration-patterns.md - CI/CD and scripting examples

See Also: claude-code-hooks for automation events, claude-code-debug for troubleshooting