What are side chats? Claude Code, Codex, Cursor, and Grok

A side chat is a question you ask next to the coding session you already have open. The answer uses that session’s context. It does not get written into the main transcript.

You use one when a detail would pull the agent off the task. “Does this handler read the body twice?” is that kind of question. A new session is the wrong tool for it. So is a subagent, which is a separate worker with its own job.

How a side chat works

The tool copies or reads the current session so the side question has something to answer from. The reply is stored beside the main thread. Follow-ups stay there. The main transcript still ends where it ended before you asked.

What “beside” means depends on the product. Claude Code’s CLI can show you the latest side question again in that session. The desktop app drops side chats when you quit. Codex calls its version an ephemeral fork. Cursor keeps a durable child conversation you can archive. Grok Build’s command list only says the question does not interrupt.

Side chats in each tool

The command is /btw or /side. The lifetime of the answer is not the same.

Claude Code

In the CLI, /btw plus a question asks about the current session without adding to the conversation. /btw with no question shows the most recent side question, so you can browse earlier answers. If you have not asked one yet, Claude Code prints a usage line. The during-a-task page points at /btw for a side question that should stay out of the history.

In the desktop app, a side chat uses the session’s context and adds nothing back to the main conversation. Open it with Cmd+; on macOS, Ctrl+; on Windows, or /btw. It can read the main thread up to that point. Close it and the main session continues. This works in local, SSH, and WSL sessions. The desktop app does not save side chats to disk, so you cannot return to one after you close the app.

The CLI behavior and the desktop behavior are different. Browsing earlier answers is the CLI. Losing the side chat when the app closes is the desktop app.

See Claude Code commands and Claude Code Desktop.

OpenAI Codex

/side and /btw start an ephemeral side chat. The point is a focused follow-up that does not disrupt the main chat’s transcript.

/side opens that fork without switching away from the main chat. You can pass the question inline. The docs’ example is /side Check whether this plan has an obvious risk. The side transcript is separate from the parent. While you are in side mode, the TUI still shows the parent chat’s status, so you can see whether the main chat is still running.

/side is unavailable inside another side chat, and unavailable during review mode. /delete is unavailable while a chat is running or while you are in a side chat.

See Codex slash commands.

Cursor

A side chat is a durable child conversation attached to a parent agent. The parent’s history is copied in as reference context for the model. That history is not rendered in the side-chat transcript. Only the side prompt and its follow-ups show up there.

By default the side chat focuses on reading, searching, and answering, so the main agent keeps working. Open one with /side, and append the question if you want it sent immediately. You can also select text or a diff and choose Ask in Side Chat. The shortcut is Shift+Cmd+S on Mac and Shift+Ctrl+S on Windows and Linux.

Follow-ups stay in the side chat. They do not appear in the parent. To bring something back, @-mention the side chat in the main thread. The close button archives the side chat. It does not delete the conversation.

Forking is a different action. A fork copies messages into a new chat. A side chat only seeds the parent history as hidden context. Nesting is not supported. A side chat cannot start its own side chat.

Side chats are local. They are not available for Cloud Agents. A side chat stays on the parent it was opened from. Starting a new conversation leaves it there until you archive it.

The CLI slash-command reference lists /fork and /ask. It does not list /side. The side-chat help page is the IDE chat.

See Cursor side chats and the CLI slash commands.

Grok Build

The command table lists /btw <question> as a side question that does not interrupt. The page does not describe /btw with an empty argument, and it does not say where the answer is stored.

The Build changelog adds three behaviors. Side questions reuse the parent session’s cached prefix. /btw retries when the model is temporarily overloaded. Inside grok --minimal, the answer shows in the live area and is committed to the scrollback when you press Esc.

See Grok Build modes and commands and the Build changelog.

Details checked against each vendor’s documentation in November 2026.

A real example

You are in the middle of a plan and you want a check that should not become the next instruction. In Codex the documented form is:

/side Check whether this plan has an obvious risk

The same shape in Claude Code and Grok Build is /btw plus the question:

/btw Why does this handler read the body twice?

In Cursor’s IDE chat, /side opens the child conversation. Shift+Cmd+S does it from the current selection on a Mac.

When to use a side chat

Use one for a question about the code or the plan in front of you, when the answer should not steer the next edit. A naming question, a “is this assumption true?” check, and a short explanation of a function you are about to change all fit.

Skip it when you want the answer to become the task. Say that in the main thread. Skip it when you want a worker that edits files on its own. That is a subagent, or a second session. Too many conversations with coding agents is the case against opening those by habit.

Pitfalls

The four commands look alike and they do not keep the answer for the same amount of time. Claude Code Desktop drops the side chat when you quit. Cursor keeps it until you archive it, and archiving is the close button. Codex calls the chat ephemeral and keeps the parent status visible while you are in it.

A side chat still spends a model call. Grok Build reuses the parent session’s cached prefix, which is a cache hit, not a free question. The main context window is what that prefix comes from.

Cursor will not nest a side chat inside a side chat, and Codex will not open /side inside a side chat or during review mode. If the command does nothing, you are probably already in one.

The Cursor CLI reference has /fork, not /side. Forking copies the chat. That is the opposite of keeping the main transcript clean.

Related on flaviocopes.com

• The complete guide to the Codex CLI shows /side and /btw in the session commands.
• A deep dive into Grok Build uses /btw for a question that should not stop the current turn.
• Too many conversations with coding agents is the argument for not opening another full session.
• Work Tracebook is a timeline of finished agent work. A side question is how you ask without starting another session that would land on that timeline.

Related glossary entries

• Sessions: A session is a saved coding-agent conversation you can resume later. How Claude Code, Codex, the Cursor CLI and Grok Build store, name, resume and fork one.
• Slash commands: Slash commands are the /name controls inside a coding agent session. How they work in Claude Code, Codex, Cursor and Grok Build, and how to add your own.
• Context window: The context window is everything a coding agent can see at once. How to check it, free it and keep it small in Claude Code, Codex, Cursor and Grok Build.
• Subagents: A subagent is a helper your coding agent starts with its own context window. How subagents work in Claude Code, Codex, Cursor and Grok Build.

All AI glossary entries →

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