First Session & REPL Basics

A Claude Code session is an interactive REPL in your terminal where you type natural-language requests, watch tool calls, approve actions, and steer a multi-turn conversation about your repo.

Why it matters

The REPL is where you actually drive the agent, and a few primitives — slash commands, approval prompts, @ file mentions, interrupt — separate a smooth session from a frustrating one. Knowing them turns “type and pray” into a controllable loop: you stay in the conversation, redirect mid-task, and keep the context window healthy instead of restarting from scratch.

How it works

Run claude to enter the REPL. You type a request, Claude responds and may call tools; for anything mutating (Edit, Bash) it pauses for approval unless permissions allow it (see permission-modes).

Input	Effect
plain text	a request / message to Claude
/command	a slash command — REPL control
@path/to/file	mention a file to pull it into context
Esc	interrupt Claude mid-response or mid-tool
Ctrl+C / Ctrl+D	cancel input / exit the session

• Conversation is stateful: each turn sees the prior turns until you /clear or the window fills.
• Useful built-in-slash-commands: /help, /status, /clear (wipe context), /compact (summarize to reclaim room) — see managing-context-clear-compact.
• Esc twice (or /rewind-style) lets you back out of a wrong direction without killing the session.
• A long answer can be interrupted with Esc to add a correction — you don’t have to wait for it to finish.
• Multi-line input and an optional vim editing mode exist for composing bigger prompts — see keyboard-shortcuts-vim-mode.

Example

$ claude
> add input validation to the signup handler and run the tests
  ⏺ Grep "signup" … Read src/auth/signup.ts
  ⏺ Edit src/auth/signup.ts  [approve? y]
  ⏺ Bash: npm test            [approve? y]
  … 2 failing → Edit → re-run → green
> /compact         # summarize this thread, free up context
> now add a test for the empty-email case

One continuous conversation: it built on the earlier edits because the session kept that history.

Pitfalls

• Letting context bloat. A 200-message thread degrades and gets slow; /clear between unrelated tasks and /compact within a long one.
• Walking away during approvals. In default mode Claude blocks waiting for your y; an unattended session can stall for hours on the first Bash prompt.
• Forgetting @ exists. Describing a file in prose when you could @-mention it wastes tokens and risks Claude grepping for the wrong one.
• Ctrl+C to fix a typo. It cancels the turn; use Esc to interrupt and steer while keeping the conversation alive.

See also

• interactive-mode
• managing-context-clear-compact
• keyboard-shortcuts-vim-mode