claude-code-headless

# Claude Code Headless Mode

Run Claude Code from scripts without interactive UI.

## Quick Start

```bash
# 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)
```bash
claude -p "Hello"
# Outputs: Human-readable response
```

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

## Common Patterns

### Script with tool restrictions
```bash
claude -p "Analyze the codebase" \
  --allowedTools "Read,Grep,Glob" \
  --disallowedTools "Write,Edit,Bash"
```

### CI/CD integration
```bash
claude -p "Review this PR diff" \
  --permission-mode acceptEdits \
  --output-format json \
  --append-system-prompt "Focus on security issues"
```

### Multi-turn automation
```bash
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

```bash
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

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