Headless

Claude Code Headless Mode

Overview

Headless mode enables running Claude Code programmatically via command line without an interactive UI, making it suitable for automation, scripts, and integration with other tools.

Basic Usage

The primary interface is the claude command with the --print (or -p) flag for non-interactive execution:

claude -p "Stage my changes and write commits" \
  --allowedTools "Bash,Read" \
  --permission-mode acceptEdits

Key Configuration Options

Output Formats

Text Output (Default)

Returns plain text response.

JSON Output

Provides structured data with metadata:

{
  "type": "result",
  "subtype": "success",
  "total_cost_usd": 0.003,
  "duration_ms": 1234,
  "num_turns": 6,
  "result": "Response text...",
  "session_id": "abc123"
}

Streaming JSON Output

Emits messages as received in JSONL format, useful for real-time processing.

Input Methods

Text Input

Direct arguments or stdin:

echo "Explain this code" | claude -p

Streaming JSON Input

Multiple conversation turns via stdin using JSONL format with -p, --output-format stream-json, and --input-format stream-json.

Multi-turn Conversations

Resume existing sessions:

claude --continue "Refactor for performance"
claude --resume 550e8400-e29b-41d4-a716-446655440000 "Fix linting issues"

Integration Examples

SRE Incident Response

Diagnose issues with severity assessment using allowed tools and MCP configuration for monitoring integrations.

Security Review

Audit pull request diffs for vulnerabilities and compliance issues using Read and WebSearch tools.

Legal Assistant

Multi-step document review maintaining session context across separate requests.

Best Practices

• Use JSON output for programmatic parsing and integration
• Parse results with tools like jq for data extraction
• Handle errors by checking exit codes and stderr
• Maintain session context for multi-turn workflows
• Implement timeouts for long-running operations
• Respect rate limits with delays between requests
• Leverage session management for maintaining conversation state

Example: Automated Code Review

#!/bin/bash
# Review PR changes in headless mode

RESULT=$(claude -p "Review changes in git diff for security issues" \
  --allowedTools "Bash,Read,Grep" \
  --output-format json \
  --permission-mode acceptAll)

# Parse result
echo "$RESULT" | jq -r '.result'

# Check exit code
if [ $? -ne 0 ]; then
  echo "Review failed"
  exit 1
fi

Example: CI/CD Integration

# In .gitlab-ci.yml or GitHub Actions
claude -p "Run tests and fix any failures" \
  --allowedTools "Bash,Read,Edit,Write" \
  --max-turns 10 \
  --output-format json

Error Handling

Check exit codes and parse error messages:

• Exit code 0: Success
• Non-zero: Error occurred (check stderr)

if ! claude -p "task" 2>error.log; then
  echo "Error: $(cat error.log)"
  exit 1
fi

Session Management

Save session IDs for continuation:

# First run
RESULT=$(claude -p "Start analysis" --output-format json)
SESSION_ID=$(echo "$RESULT" | jq -r '.session_id')

# Continue later
claude --resume "$SESSION_ID" "Continue analysis"