stack

name	stack
description	Stack a new workspace on top of the current branch — a handoff into a NEW workspace whose new branch is based off, and targets, the current branch.
when_to_use	Invoke when the user wants to branch off the current work into a separate, parallel workspace stacked on the current branch — e.g. "stack a new agent on this", "spin off a follow-up based on this branch", or to keep the current agent focused while a fresh agent tackles a dependent piece of work. The new branch is based off the current branch AND targets it, so its diff and any MR are scoped to just the changes made on top of the current work.
user_invocable	true

Stack

ARGUMENTS: $ARGUMENTS

Step 0 — Refuse if not in a worktree workspace

Stacking is only supported in worktree workspaces. The stacked workspace is created via git worktree add in the project's on-disk git repo, and only worktree source workspaces share that git (so the current branch is locally resolvable). From a clone or in-place workspace, the stacked workspace cannot find the current branch as a ref — pushing to origin doesn't help because git worktree add doesn't DWIM a bare branch name to origin/<branch>.

Check the strategy first:

sculpt workspace show "$SCULPT_WORKSPACE_ID" --json | jq -r .strategy

If the result is not WORKTREE, stop and tell the user (using their strategy name):

Stacking isn't supported from a <strategy> workspace — the stacked workspace wouldn't be able to base off your current branch. Use /sculptor-experimental:handoff (new agent in the same workspace) to continue this work, or move it into a worktree workspace first.

Only proceed if the strategy is WORKTREE.

Steps 1–4 — Hand off into a new workspace

Stacking is a handoff into a new workspace, specialized for building on top of the current branch. Follow the /sculptor-experimental:handoff skill — invoke it and do what its "new workspace" path does (run the pre-flight commit check, compose a self-contained context-summary prompt, create the workspace + agent with sculpt run, then report the new IDs) — with these differences:

1. Don't ask which destination. Stacking always creates a new workspace, so skip handoff's Step 1 question entirely.
2. Target the current branch. Pass --target-branch <current-branch> in addition to --branch <current-branch>. This scopes the new workspace's diff/MR to only the changes stacked on top of the current branch, instead of the repo's default target (e.g. main). This is the defining trait of a stack.

So the create command (handoff's Step 4 new-workspace command, with --target-branch added) is:

git rev-parse --abbrev-ref HEAD   # current branch = source AND target

sculpt run \
  --strategy worktree \
  --branch "<current-branch>" \
  --target-branch "<current-branch>" \
  --name "<short task name>" \
  --json \
  "<context-summary prompt>"

Use sculpt run, not sculpt workspace create. sculpt run creates the workspace, its agent, and the git worktree in one step. sculpt workspace create only registers a workspace record — no agent, no checkout — so it renders as a blank screen in the UI. To add an agent to an already-empty workspace, run sculpt agent create -w <ws_id> -p "...".