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:

bash

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)

bash

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

Streaming (for real-time monitoring)

bash

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

Structured Output (schema validation)

bash

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

Headless Agent Pattern (CRITICAL)

Proper headless agent spawn:

bash

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

bash

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

Piped Input

bash

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

Multi-turn Session

bash

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

Stream Monitoring

bash

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

cli-reference

NPX Install

Tags

SKILL.md Content

CLI Reference

When to Use

Core Commands

Session Control

Headless Mode (Critical for Agents)

Tool Control

Subagent Definition (--agents flag)

Agent Fields

Key Insight

System Prompt Customization

Model Selection

MCP Configuration

Advanced Flags

Output Formats

JSON (for parsing)

Streaming (for real-time monitoring)

Structured Output (schema validation)

Headless Agent Pattern (CRITICAL)

Common Patterns

CI/CD Automation

Piped Input

Multi-turn Session

Stream Monitoring

Keyboard Shortcuts (Interactive)

Quick Commands