Subagent-driven development should not auto-create worktrees without user consent

[wesm]

Problem

The subagent-driven-development skill currently auto-creates a git worktree when starting implementation, without asking the user first. If you're on main and ask for a spec to be implemented, the work gets silently redirected to a worktree branch — which is surprising and forces a git workflow the user didn't opt into.

This also creates cleanup burden: the worktree and its branch persist after the session unless the user explicitly removes them, even after the work has been merged back.

Observed behavior

1. User asks to implement a plan
2. subagent-driven-development skill invokes EnterWorktree without asking
3. All work happens in an isolated worktree
4. User has to discover and clean up the worktree afterward
5. If work was already merged to main (e.g., via --ff-only), the worktree is redundant but still sitting on disk

Expected behavior

Worktree creation should be opt-in, not automatic. The skill should prompt the user before creating a worktree, similar to how it offers a choice between inline and subagent-driven execution.

Suggested flow:

"Plan ready. Before I start implementing:

1. Execution: Subagent-driven (recommended) or inline?
2. Isolation: Create a worktree for this work, or work in the current branch?"

If the user has set a preference (e.g., in settings or CLAUDE.md), respect it without asking.

Context

Filed at Jesse Vincent's request after discussion about this behavior. Jesse agrees this should prompt rather than auto-create.

cc @obra

[arittr]

This is fixed on dev by #1121. The worktree flow now asks before setting up an isolated worktree instead of silently creating one, while still honoring existing user/workspace guidance.

This will ship with the next release, so I’m closing this as completed.