Headless runner

Headless Runner

Run Claude Code programmatically from scripts, CI/CD pipelines, and autonomous agent workflows. Headless mode automatically loads all project configuration (.claude/ directory), giving you full access to skills, agents, hooks, and commands.

Quick Start

Most common usage:

# Basic headless invocation (from project directory)
claude -p "Your prompt here"

# With JSON output for programmatic parsing
claude -p "Run the test suite" --output-format json

# Control tool access
claude -p "Analyze failures" --allowedTools "Bash,Read,Grep"

# Multi-turn conversation
claude -p "Start task" --output-format json > result.json
SESSION_ID=$(jq -r '.session_id' result.json)
claude --resume $SESSION_ID "Continue with next step"

What gets loaded automatically:

• .claude/settings.json and .claude/settings.local.json
• .claude/agents/ (all project agents)
• .claude/skills/ (all project skills)
• Hooks configured in settings
• Slash commands from .claude/commands/
• CLAUDE.md project instructions

When to Use This Skill

Invoke this skill when user asks about:

• "How do I run Claude headless?"
• "Can I automate Claude workflows?"
• "How to use Claude in CI/CD?"
• "Programmatic Claude execution"
• "Script Claude commands"
• "Agent-to-agent communication"
• "Scheduled Claude tasks"

Core Commands

Basic Invocation

# Text output (default)
claude -p "Prompt here"

# JSON output with metadata
claude -p "Prompt here" --output-format json
# Returns: {session_id, result, cost, duration, ...}

# Streaming JSON (for long-running tasks)
claude -p "Prompt here" --output-format stream-json

Tool Permissions

# Allow specific tools
claude -p "Task" --allowedTools "Bash,Read,Write"

# Allow all tools (use with caution)
claude -p "Task" --allowedTools "*"

# Permission mode for edits
claude -p "Task" --permission-mode acceptEdits

Multi-Turn Conversations

# Resume specific session
claude --resume SESSION_ID "Continue task"

# Continue most recent session
claude --continue "Next instruction"

# Extract session ID from JSON output
SESSION_ID=$(claude -p "Start" --output-format json | jq -r '.session_id')
claude --resume $SESSION_ID "Continue"

Common Use Cases

1. CI/CD Integration

# .github/workflows/automated-task.yml
- name: Run automated analysis
  run: |
    claude -p "Analyze test failures and suggest fixes" \
      --output-format json \
      --allowedTools "Bash,Read,Grep" \
      > result.json

- name: Check for issues
  run: |
    STATUS=$(jq -r '.status' result.json)
    if [ "$STATUS" != "success" ]; then
      echo "::error::Analysis failed"
      exit 1
    fi

2. Scheduled Analysis

#!/bin/bash
# cron_daily_check.sh - Run via cron daily

cd /path/to/project

# Run analysis
claude -p "Check for code quality issues" \
  --output-format json > analysis.json

# If issues found, notify
ISSUES=$(jq -r '.issueCount' analysis.json)
if [ "$ISSUES" -gt 0 ]; then
  echo "Found $ISSUES code quality issues"
fi

3. Agent-to-Agent Workflows

#!/bin/bash
# autonomous_workflow.sh

# Agent A: Create design doc
claude -p "Use design-doc-creator to document feature X" \
  --output-format json > design.json
DESIGN_DOC=$(jq -r '.artifactPath' design.json)

# Agent B: Plan sprint from design
claude -p "Use sprint-planner to create plan from $DESIGN_DOC" \
  --output-format json > plan.json
PLAN_FILE=$(jq -r '.planPath' plan.json)

# Agent C: Execute sprint
claude -p "Use sprint-executor to execute $PLAN_FILE" \
  --output-format json > execution.json

4. Automated Testing

#!/bin/bash
# test_quality.sh

# Run tests with analysis
claude -p "Run test suite and analyze any failures" \
  --output-format json > results.json

# Parse results
SUCCESS_RATE=$(jq -r '.successRate' results.json)

# Assert quality threshold
if (( $(echo "$SUCCESS_RATE < 0.75" | bc -l) )); then
  echo "Quality below threshold: $SUCCESS_RATE"
  exit 1
fi

Available Scripts

scripts/test_headless.sh

Test headless mode works correctly with project configuration.

What it tests:

• claude command is available
• Project configuration loads (.claude/ directory)
• Skills are accessible
• Agents are accessible
• JSON output parses correctly
• Multi-turn sessions work

scripts/run_with_retry.sh <prompt> [max_retries]

Run headless command with automatic retry on failure.

Features:

• Retries on transient failures
• Exponential backoff
• JSON output preserved
• Exit codes: 0 (success), 1 (permanent failure), 2 (retries exhausted)

Workflow Patterns

Pattern 1: Single Command

Use for: Simple, one-off tasks

claude -p "Generate changelog from git log since last tag"

Pattern 2: Sequential Pipeline

Use for: Multi-step workflows where each step depends on previous

#!/bin/bash
set -euo pipefail
claude -p "Step 1" --output-format json > step1.json
ARTIFACT1=$(jq -r '.artifact' step1.json)
claude -p "Step 2 using $ARTIFACT1" --output-format json > step2.json

Pattern 3: Conversation Session

Use for: Multi-turn tasks that need context

RESULT=$(claude -p "Analyze codebase for tech debt" --output-format json)
SESSION_ID=$(echo "$RESULT" | jq -r '.session_id')
claude --resume $SESSION_ID "Focus on files over 800 lines"
claude --resume $SESSION_ID "Generate refactoring plan"

Pattern 4: Parallel Execution

Use for: Independent tasks that can run concurrently

claude -p "Task A" --output-format json > taskA.json &
claude -p "Task B" --output-format json > taskB.json &
wait
jq -s '{taskA: .[0], taskB: .[1]}' taskA.json taskB.json

Quick Tips

Output formats:

• --output-format text (default) - Human-readable
• --output-format json - For automation (includes session_id, status, cost)
• --output-format stream-json - For real-time progress

Error handling:

• Always check exit codes: if ! claude -p "..." ; then ...
• Validate JSON: echo "$RESULT" | jq -e '.status == "success"'
• Use retry with backoff (see run_with_retry.sh script)

Tool permissions:

• Analysis: --allowedTools "Read,Grep,Glob"
• Testing: --allowedTools "Bash,Read"
• Development: --allowedTools "Bash,Read,Write,Edit"

Resources

CLI Reference

See resources/cli_reference.md for complete CLI flag documentation.

Examples

See resources/examples.md for comprehensive workflow examples.

Troubleshooting

See resources/troubleshooting.md for common issues and solutions.

Notes

• Requires: Claude Code CLI installed and in PATH
• Context window: Be mindful of token limits for large prompts
• Costs: Track with --output-format json -> .cost field
• Concurrency: Multiple headless sessions can run in parallel
• State: Each invocation is stateless unless using --resume