Claude Code cheatsheet

# Explain a build error
$ cat error.log | claude -p "explain the root cause"

# Review changed files
$ git diff main --name-only | claude -p "review for issues"

# Analyze logs
$ tail -200 app.log | claude -p "summarize anomalies"

# Save output to file
$ cat data.txt | claude -p "summarize this" > summary.txt

Add Claude as a linter in package.json:

{
  "scripts": {
    "lint:ai": "claude -p 'review changes vs main, report file:line + issue'"
  }
}

Use --output-format for structured output:

$ claude -p "analyze for bugs" --output-format json

Prefer --append-* to preserve Claude's built-in capabilities. Use --system-prompt only when full control is needed.

Enable with /vim or in /config. Esc → NORMAL, i/a/o → INSERT.

macOS: set Option as Meta in terminal prefs for Alt+* shortcuts to work.

During a session:

Press Shift+Tab to cycle:

default → acceptEdits → plan → (auto)

At startup:

$ claude --permission-mode plan
$ claude --permission-mode acceptEdits

Bypass all (containers only):

$ claude --dangerously-skip-permissions

Layer allow / deny rules on top of any mode in .claude/settings.json:

{
  "permissions": {
    "allow": ["Bash(npm test)", "Bash(git log *)"],
    "deny": ["Bash(rm -rf *)"]
  }
}

View and edit rules with /permissions.

Claude saves its own notes in:

~/.claude/projects/<project>/memory/
├── MEMORY.md          # index (first 200 lines loaded)
├── debugging.md       # topic files (loaded on demand)
└── api-conventions.md

• On by default; toggle in /memory or set autoMemoryEnabled: false
• Persists across sessions and worktrees in the same git repo
• Machine-local — not shared across machines

Disable via env:

$ export CLAUDE_CODE_DISABLE_AUTO_MEMORY=1

Reference other files from CLAUDE.md:

See @README.md for project overview.
Build commands: @package.json

# Workflows

@docs/git-workflow.md

• Both relative and absolute paths are supported
• Max import depth: 5 hops
• Imported files are expanded at session start
• HTML comments in CLAUDE.md are stripped from context

#Auto-format After File Edits

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit",
        "hooks": [
          {
            "type": "command",
            "command": "npm run lint --silent"
          }
        ]
      }
    ]
  }
}

#Notify When Claude Needs You (macOS)

{
  "hooks": {
    "Notification": [
      {
        "matcher": "",
        "hooks": [
          {
            "type": "command",
            "command": "osascript -e 'display notification \"Claude needs attention\" with title \"Claude Code\"'"
          }
        ]
      }
    ]
  }
}

Config in ~/.claude/settings.json (user) or .claude/settings.json (project). View hooks with /hooks.

Reference MCP resources with @:

@github:repos/owner/repo/issues
@memory:entities
@filesystem:/path/to/file

Run MCP prompts as slash commands:

/mcp__github__search_repositories
/mcp__memory__create_entities

MCP tool pattern: mcp__<server>__<tool>

Manage in session:

/mcp

Hook on MCP tools:

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "mcp__memory__.*",
        "hooks": [{ "type": "command", "command": "logger.sh" }]
      }
    ]
  }
}

Create in .claude/agents/<name>.md:

---
name: code-reviewer
description: Reviews code for bugs and style
tools:
  - Read
  - Grep
  - Glob
---
You are an expert code reviewer.
Focus on correctness and clarity.

Use subagents naturally in conversation:

• review the auth module for security issues
• use the code-reviewer agent on api.ts
• /agents — manage agent configs

Subagent with worktree isolation:

---
name: parallel-worker
isolation: worktree
description: Works in isolated branch
---

Shared auto memory for subagents — add to frontmatter:

autoMemoryEnabled: true

Create a cloud scheduled task:

/schedule review open PRs every morning at 9am

Session-scoped loop (stays open):

/loop 5m check for new issues

#GitHub Actions

- uses: anthropics/claude-code-action@beta
  with:
    anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
    prompt: 'review this PR for issues and comment'

#GitLab CI/CD

claude-review:
  script:
    - claude -p "review changes in this MR"
      --output-format json