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"
Verwandte Skills
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.