[DOCS] Document `/subtask` and the new `/fork` background-session behavior

Documentation Type

Unclear/confusing documentation

Documentation Location

https://code.claude.com/docs/en/sub-agents

Section/Topic

“Fork the current conversation” and the relationship between forks, background sessions, and in-session subtasks.

Current Documentation

The subagent guide currently says:

“You can start a fork yourself with /fork followed by a directive...”

and:

“The fork appears in a panel below your prompt and runs in the background while you keep working.”

The command reference describes /fork as a way to hand a side task to a background subagent, but it does not list /subtask.

What's Wrong or Missing?

Claude Code 2.1.212 changes the user-visible distinction between these commands: /fork copies the conversation into a new background session with its own row in claude agents, while the in-session subagent behavior formerly associated with /fork is now /subtask.

The current text explains the fork concept but does not tell users that /subtask is the replacement for an in-session subagent, nor does it explain that /fork creates a separate background session that can be found in agent view. A user following the current guide can therefore choose the wrong command or look for the fork only in the prompt panel.

Suggested Improvement

Update the fork section and command reference to:

1. Add /subtask with a short example and explain that it launches an in-session subagent.
2. State that /fork creates a new background session containing a copy of the current conversation and that the session appears as its own row in claude agents.
3. Add a small comparison table linking /subtask, /fork, and /branch, including whether the command stays in the current session, creates a background row, or switches the user into a conversation copy.

Impact

Medium - Makes feature difficult to understand

Additional Context

Affected Pages:

| Page | Context |
|------|---------|
| https://code.claude.com/docs/en/sub-agents | Fork behavior and /subtask replacement |
| https://code.claude.com/docs/en/commands | Slash-command reference for /fork and /subtask |
| https://code.claude.com/docs/en/agent-view | Where the new background session appears and how it is managed |
| https://code.claude.com/docs/en/sessions | Relationship between background sessions and resumable conversations |

Total scope: 4 pages are relevant to the command and session distinction.

The behavior is introduced in Claude Code 2.1.212; the release notes are listed at https://code.claude.com/docs/en/changelog.