claude-headless-mode

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Guide for using claude CLI in headless mode with --print, output formats, and JSON schema

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Sourcemajesticlabs-dev/majestic-marketplace
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NPX Install

npx skill4agent add majesticlabs-dev/majestic-marketplace claude-headless-mode

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claude-cliheadless-modeautomationjson-schemacli-tool

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Claude Headless Mode

Use 
claude -p
(or 
--print
) for non-interactive execution in scripts, CI, and automation.

Basic Usage

bash
# Simple prompt
claude -p "Summarize this repo"

# With file input
claude -p "Review this code" < file.py

# Pipe output
claude -p "List all functions" | grep "def "

Output Formats

FormatFlagUse Case
Text
--output-format text
Human-readable (default)
JSON
--output-format json
Single JSON result
Stream JSON
--output-format stream-json --verbose
Real-time streaming

Text Output (Default)

bash
claude -p "What is 2+2?"
# Output: 4

JSON Output

bash
claude -p "What is 2+2?" --output-format json
Returns wrapper with metadata:
json
{
  "type": "result",
  "subtype": "success",
  "result": "4",
  "duration_ms": 1234,
  "total_cost_usd": 0.01,
  "session_id": "...",
  "structured_output": null
}
Extract just the result:
bash
claude -p "What is 2+2?" --output-format json | jq -r '.result'

Stream JSON Output

bash
claude -p "Long analysis" --output-format stream-json --verbose
  • Streams newline-delimited JSON as execution progresses
  • Shows tool calls, messages, progress in real-time
  • Final line contains the result
  • Requires 
    --verbose
    flag
Extract final result:
bash
claude -p "Analyze code" --output-format stream-json --verbose \
  | tee /dev/stderr \
  | tail -1 \
  | jq -r '.result'

Structured Output with JSON Schema

Force Claude to return data matching a specific schema:
bash
claude -p "Extract function names from auth.py" \
  --output-format json \
  --json-schema '{
    "type": "object",
    "properties": {
      "functions": { "type": "array", "items": { "type": "string" } }
    },
    "required": ["functions"]
  }'
Result appears in 
structured_output
field:
json
{
  "result": "...",
  "structured_output": {
    "functions": ["login", "logout", "verify_token"]
  }
}

Schema Examples

Simple object:
json
{
  "type": "object",
  "properties": {
    "answer": { "type": "integer" }
  },
  "required": ["answer"]
}
Task result (success/failure):
json
{
  "type": "object",
  "properties": {
    "status": { "type": "string", "enum": ["success", "failure"] },
    "summary": { "type": "string" },
    "files_changed": { "type": "array", "items": { "type": "string" } },
    "error_category": { "type": "string" },
    "suggestion": { "type": "string" }
  },
  "required": ["status", "summary"]
}
Extract from schema result:
bash
OUTPUT=$(claude -p "$PROMPT" --output-format json --json-schema "$SCHEMA")
STATUS=$(echo "$OUTPUT" | jq -r '.structured_output.status')
SUMMARY=$(echo "$OUTPUT" | jq -r '.structured_output.summary')

Common Options

OptionDescription
-p, --print
Headless mode (required)
--output-format
text, json, stream-json
--json-schema
Enforce output schema
--verbose
Required for stream-json
--model
Select model (sonnet, opus, haiku)
--max-turns
Limit agentic turns
--permission-mode
bypassPermissions, plan, etc.
--allowedTools
Restrict available tools

Permission Modes

bash
# Skip all permission prompts (trusted environments only)
claude -p "Fix all linting errors" --permission-mode bypassPermissions

# Plan mode (read-only exploration)
claude -p "Analyze architecture" --permission-mode plan

Examples

CI/CD Integration

bash
# Run tests and get structured result
RESULT=$(claude -p "Run tests and report results" \
  --output-format json \
  --json-schema '{"type":"object","properties":{"passed":{"type":"boolean"},"failures":{"type":"array","items":{"type":"string"}}},"required":["passed"]}')

if [ "$(echo $RESULT | jq '.structured_output.passed')" = "true" ]; then
  echo "Tests passed"
else
  echo "Tests failed"
  exit 1
fi

Batch Processing

bash
for file in src/*.py; do
  claude -p "Review $file for security issues" \
    --output-format json \
    --json-schema '{"type":"object","properties":{"issues":{"type":"array"}},"required":["issues"]}' \
    | jq ".structured_output.issues"
done

Fresh Context Task Execution

bash
# Each invocation is independent (no conversation history)
claude -p "Task 1: Create migration" --output-format json
claude -p "Task 2: Add model" --output-format json
claude -p "Task 3: Write tests" --output-format json

Task Coordination

Share TaskList across headless invocations using 
CLAUDE_CODE_TASK_LIST_ID
.

Environment Variable

bash
# All invocations share the same TaskList
export CLAUDE_CODE_TASK_LIST_ID="my-project"
claude -p "Use TaskCreate to add: Setup database"
claude -p "Use TaskCreate to add: Write migrations"
claude -p "Use TaskList to show all tasks"  # Shows both tasks

Pattern: Orchestrator + Workers

bash
TASK_LIST_ID="epic-$(date +%Y%m%d)"
export CLAUDE_CODE_TASK_LIST_ID="$TASK_LIST_ID"

# Orchestrator creates tasks
claude -p "Use TaskCreate for each: Task 1, Task 2, Task 3"

# Workers execute (each sees shared TaskList)
for task_id in 1 2 3; do
  claude -p "Use TaskUpdate to mark task #$task_id as in_progress, implement it, then mark completed"
done

# Check final state
claude -p "Use TaskList to show status"

Task Tools

ToolPurpose
TaskCreate
Create new task with subject, description
TaskList
List all tasks with status
TaskUpdate
Update task status (in_progress, completed) or add blockedBy
TaskGet
Get full details of a specific task

Dependencies

bash
# Task 2 depends on Task 1
claude -p "Use TaskUpdate on task #2 to set blockedBy: [1]"
Tasks persist to 
~/.claude/tasks/
and survive session restarts.

Notes

  • Each 
    -p
    invocation starts fresh (no context from previous runs)
  • Use 
    --output-format json
    for programmatic parsing
  • structured_output
    field contains schema-validated data
  • result
    field contains raw text response
  • Stream JSON requires 
    --verbose
    flag
  • Cost info available in JSON output: 
    total_cost_usd