What is Claude Code?
An agentic CLI tool that reads your codebase, edits files, runs shell commands, and manages git workflows. It works across your terminal, VS Code, JetBrains, a desktop app, and the web. |
It is not a chat interface that suggests code. |
Claude plans work, writes across multiple files, runs tests, and creates PRs. It can take actions you can't undo — permissions matter. |
First Run
cd your-project
claude # interactive session
claude auth login # if not authenticated
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On first run Claude reads your repo and prompts for auth. Run /init inside a session to generate a CLAUDE.md project file.
Claude Code CLI Flags
Session Control |
-c |
Continue most recent session |
-r <name> |
Resume session by name |
--resume <id> |
Resume session by ID |
--bg |
Run session in background |
Output and Automation |
-p "prompt" |
Non-interactive, print and exit |
--output-format json |
Machine-readable output |
--output-format stream-json |
Stream JSON as it arrives |
--max-turns N |
Limit agentic turns |
Tools and Permissions |
--allowed-tools |
Comma-separated allow list, e.g. Read,Grep |
--permission-mode |
default | acceptEdits | auto | bypassPermissions |
--model <name> |
Override model for this session |
--dangerously-skip-permissions |
DANGER No prompts — CI only |
Keyboard Shortcuts
Esc Esc |
Interrupt current action and rewind the last message |
Ctrl+C |
Cancel current generation (keeps history) |
Shift+Tab |
Cycle permission mode: ask → auto → bypass |
Ctrl+B |
Push session to background; reclaim terminal |
@filename |
Include a file's contents inline in your message |
!`cmd` |
Run a bash command and inject output into message |
↑ / ↓ |
Navigate message history |
/keybindings |
Edit shortcuts — stored in ~/.claude/keybindings.json |
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Slash Commands
Context management |
/compact |
Compress history to free context. Pass a focus hint: /compact keep auth module |
/clear |
Wipe conversation history entirely. Start fresh. |
/status |
Show context usage, session ID, model, cost |
Session navigation |
/rename |
Name the current session (no arg = auto-name) |
/fork |
Branch conversation at this point (try alternatives without losing current state) |
/resume |
Resume a previous session by name or ID |
/export |
Export conversation as plain text |
Tools and Config |
/model <name> |
Switch model mid-session. Takes effect next message. |
/doctor |
Diagnose auth, config, and connection issues |
/init |
Generate CLAUDE.md for current project |
/schedule |
Create a recurring automated task |
/help |
List all current slash commands |
Model Aliases |
opus / sonnet / haiku |
Short aliases: /model opus
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auto |
Claude picks model per task |
Planning and Flow Commands
/plan |
Ask Claude to produce a plan before writing any code. Review and approve, then Claude executes. Use for any non-trivial change. |
/goal |
Set a persistent session goal. Claude references it to stay on track across compacts and model switches. Useful for long sessions. |
/effort |
Set reasoning depth: low | normal | high. Default on Opus 4.8 is high. Lower for speed/cost, higher for architecture decisions. |
/checkpoint |
Save current conversation state as a named restore point. Useful before risky tool sequences. |
/review |
Request a code review of current working state. Add --fix to apply findings immediately. |
/workflow |
Trigger a dynamic workflow — sequences of steps Claude will walk through. See ~/.claude/commands/ for custom workflows. |
Typical Flow Example:
/goal Refactor the auth module to PSR-12
/plan
# review the plan, press y to approve
# Claude writes code
/compact focus on auth module
/review --fix
Custom Slash Commands
File Locations |
.claude/commands/ |
Project commands (team-shared) |
~/.claude/commands/ |
Personal commands (all projects) |
Each .md file becomes a slash command named after the file. Invoked with /filename. |
Example: .claude/commands/pr-review.md |
Review the current branch diff against main.
List bugs and security issues as a numbered list.
Then summarise in one sentence.
Arguments: $ARGUMENTS
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Use !`git diff main`
in the file body to pre-inject bash output. Use @path/to/file
to inline a file. Use $ARGUMENTS
to accept runtime args: /pr-review focus on SQL
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CLAUDE.md: Project Instructions
Read at the start of every session. The primary way to give Claude persistent context about your project without repeating yourself. |
Locations (in priority order) |
./CLAUDE.md |
Project root — committed to repo, shared with team |
./.claude/CLAUDE.md |
Project-local, can be gitignored |
~/.claude/CLAUDE.md |
Personal global — applies to all projects |
What To Put In It |
Stack & conventions |
PHP version, framework, coding standard (PSR-12) |
Build & test commands |
How to run tests, linter, deploy |
Off-limits files |
Files Claude should never touch |
Project structure |
Where things live and why |
Behaviour rules |
Always write tests, never edit migrations |
Example CLAUDE.md snippet
Stack: PHP 8.3, Laravel 11, MySQL 8
Standard: PSR-12. Run: ./vendor/bin/pint
Tests: ./vendor/bin/pest — must pass before commit
Never edit files in /database/migrations/
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Headless and Pipe Mode
# Pipe content as context
cat src/Auth.php | claude -p "Find security issues"
git diff main | claude -p "Review this diff"
git log --oneline -10 | claude -p "Write release notes"
# JSON output (includes cost, session ID, turn count)
claude -p "list TODOs" --output-format json | jq .
# Read-only: no file writes or bash
claude -p "explain architecture" \
--allowed-tools Read,Grep
# Multi-step: reuse session across calls
SID=$(claude -p "analyse test failures" \
--output-format json | jq -r '.session_id')
claude -p "fix the failures" --resume "$SID"
# Append system prompt for specialised context
claude -p "review errors" \
--append-system-prompt "You are an SRE expert"
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Use -p for scripts and CI. Claude runs the prompt and exits — no interactive session.
Permissions and Safety
Permission Modes |
default |
acceptEdits |
auto |
bypassPermissions |
Tool allow/deny in settings |
# .claude/settings.json
{
"permissions": {
"allow": ["Bash(git:)", "Read", "Write"],
"deny": ["Bash(rm -rf)"]
}
}
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Restrict in CLI |
claude --allowed-tools Read,Grep "review auth"
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