The /btw command (short for "by the way") lets you ask a tangential question without losing the thread of your main task.

What it does

When you type /btw <question>, Claude answers in a lightweight context that doesn't add to the current task's working memory. It's useful for quick clarifications - "what does this flag do?" or "is there a shorter way to write this?" - without polluting the primary conversation.

When to use it

You're deep in a task and need a one-off fact before continuing.
You want to sanity-check something without spending tokens on tool calls.
You have a follow-up idea but don't want to start a new session.
You're onboarding and frequently need meta-context.

Gotchas

Side questions still count against your overall quota and context budget, just more cheaply.
Don't use /btw for anything that needs tool access - it's meant for chat, not editing.
Nested /btw calls aren't supported. One side question at a time.

Official docs: https://code.claude.com/docs/en/interactive-mode.md#side-questions-with-btw