CLI Reference

Complete reference for Claude Code command-line interface.

When to Use

• "What CLI flags are available?"
• "How do I use headless mode?"
• "Claude in automation/CI/CD"
• "Output format options"
• "System prompt via CLI"
• "How do I spawn agents properly?"

Core Commands

Command	Description	Example
claude	Start interactive REPL	claude
claude "query"	REPL with initial prompt	claude "explain this project"
claude -p "query"	Headless mode (SDK)	claude -p "explain function"
cat file | claude -p	Process piped content	cat logs.txt | claude -p "explain"
claude -c	Continue most recent	claude -c
claude -c -p "query"	Continue via SDK	claude -c -p "check types"
claude -r "id" "query"	Resume session	claude -r "auth" "finish PR"
claude update	Update version	claude update
claude mcp	Configure MCP servers	See MCP docs

Session Control

Flag	Description	Example
--continue, -c	Load most recent conversation	claude --continue
--resume, -r	Resume session by ID/name	claude --resume auth-refactor
--session-id	Use specific UUID	claude --session-id "550e8400-..."
--fork-session	Create new session on resume	claude --resume abc --fork-session

Headless Mode (Critical for Agents)

Flag	Description	Example
--print, -p	Non-interactive, exit after	claude -p "query"
--output-format	text, json, stream-json	claude -p --output-format json
--max-turns	Limit agentic turns	claude -p --max-turns 100 "query"
--verbose	Full turn-by-turn output	claude --verbose
--dangerously-skip-permissions	Skip permission prompts	claude -p --dangerously-skip-permissions
--include-partial-messages	Include streaming events	claude -p --output-format stream-json --include-partial-messages
--input-format	Input format (text/stream-json)	claude -p --input-format stream-json

Tool Control

Flag	Description	Example
--allowedTools	Auto-approve these tools	"Bash(git log:*)" "Read"
--disallowedTools	Block these tools	"Bash(rm:*)" "Edit"
--tools	Only allow these tools	--tools "Bash,Edit,Read"

Subagent Definition (--agents flag)

Define custom subagents inline via JSON:

claude --agents '{
  "code-reviewer": {
    "description": "Expert code reviewer. Use proactively after code changes.",
    "prompt": "You are a senior code reviewer. Focus on code quality and security.",
    "tools": ["Read", "Grep", "Glob", "Bash"],
    "model": "sonnet"
  },
  "debugger": {
    "description": "Debugging specialist for errors and test failures.",
    "prompt": "You are an expert debugger. Analyze errors and provide fixes."
  }
}'

Agent Fields

Field	Required	Description
description	Yes	When to invoke this agent
prompt	Yes	System prompt for behavior
tools	No	Allowed tools (inherits all if omitted)
model	No	sonnet, haiku, or claude-opus-4-5-20251101

Key Insight

When Lead uses Task tool, it auto-spawns from these definitions. No manual spawn needed.

System Prompt Customization

Flag	Behavior	Modes
--system-prompt	Replace entire prompt	Interactive + Print
--system-prompt-file	Replace from file	Print only
--append-system-prompt	Append to default (recommended)	Interactive + Print

Use --append-system-prompt for most cases - preserves Claude Code capabilities.

Model Selection

Flag	Description	Example
--model	Set model for session	--model claude-sonnet-4-5
--fallback-model	Fallback if default overloaded	--fallback-model sonnet

Aliases: sonnet, opus, haiku

MCP Configuration

Flag	Description	Example
--mcp-config	Load MCP servers from JSON	--mcp-config ./mcp.json
--strict-mcp-config	Only use these MCP servers	--strict-mcp-config --mcp-config ./mcp.json

Advanced Flags

Flag	Description	Example
--add-dir	Add working directories	--add-dir ../apps ../lib
--agent	Specify agent for session	--agent my-custom-agent
--permission-mode	Start in permission mode	--permission-mode plan
--permission-prompt-tool	MCP tool for permissions	--permission-prompt-tool mcp_auth
--plugin-dir	Load plugins from directory	--plugin-dir ./my-plugins
--settings	Load settings from file/JSON	--settings ./settings.json
--setting-sources	Which settings to load	--setting-sources user,project
--betas	Beta API headers	--betas interleaved-thinking
--debug	Enable debug mode	--debug "api,hooks"
--ide	Auto-connect to IDE	--ide
--chrome	Enable Chrome integration	--chrome
--no-chrome	Disable Chrome for session	--no-chrome
--enable-lsp-logging	Verbose LSP debugging	--enable-lsp-logging
--version, -v	Output version	claude -v

Output Formats

JSON (for parsing)

claude -p "query" --output-format json
# {"result": "...", "session_id": "...", "usage": {...}}

Streaming (for real-time monitoring)

claude -p "query" --output-format stream-json
# Newline-delimited JSON events

Structured Output (schema validation)

claude -p "Extract data" \
  --output-format json \
  --json-schema '{"type":"object","properties":{...}}'

Headless Agent Pattern (CRITICAL)

Proper headless agent spawn:

claude -p "$TASK_PROMPT" \
  --session-id "$UUID" \
  --dangerously-skip-permissions \
  --max-turns 100 \
  --output-format stream-json \
  --agents '{...}' \
  --append-system-prompt "Context: ..."

Missing any of these causes hangs:

• --session-id - Track the session
• --dangerously-skip-permissions - Headless requires this
• --max-turns - Prevents infinite loops

Common Patterns

CI/CD Automation

claude -p "Run tests and fix failures" \
  --dangerously-skip-permissions \
  --max-turns 50 \
  --output-format json | jq '.result'

Piped Input

cat error.log | claude -p "Find root cause"
gh pr diff | claude -p "Review for security"

Multi-turn Session

id=$(claude -p "Start task" --output-format json | jq -r '.session_id')
claude -p "Continue" --resume "$id"

Stream Monitoring

claude -p "Long task" \
  --output-format stream-json \
  --include-partial-messages | while read -r line; do
    echo "$line" | jq '.type'
done

Keyboard Shortcuts (Interactive)

Shortcut	Action
Ctrl+C	Cancel current
Ctrl+D	Exit
Ctrl+R	Reverse search history
Esc Esc	Rewind changes
Shift+Tab	Toggle permission mode

Quick Commands

Prefix	Action
/	Slash command
!	Bash mode
#	Add to memory
@	File mention