Create Worktree

Create Worktree

Create a dedicated worktree + tmux window via workmux add, with a task prompt injected into the new agent session.

Workflow

1. Determine the Branch Name

The user provides either:

• An explicit branch name (e.g., "create worktree feature/my-thing") -- use as-is
• A task description (e.g., "create a worktree for adding dark mode") -- construct a branch name using the TYPE/SLUG format

Branch naming rules (TYPE/SLUG):

• TYPE: Use fix if the user mentions "fix", "bug", "patch", or similar. Use feature for everything else.
• SLUG: Slugify the description: lowercase, replace spaces and special characters with hyphens, collapse consecutive hyphens, trim leading/trailing hyphens, truncate to 50 characters at a word boundary.

Examples:

• "create worktree for adding dark mode" -> feature/adding-dark-mode
• "spin up a worktree to fix the auth timeout" -> fix/auth-timeout
• "new worktree feature/refactor-config" -> feature/refactor-config (used as-is)

2. Compose the Task Prompt

Build a prompt string that gives the new agent context about its task:

Work on: [user's task description]

Branch: [BRANCH_NAME]

Keep the prompt concise -- a few sentences at most. Use the user's own description of the task as the core content.

If the user provided only a branch name with no description, derive a human-readable description from the branch name (e.g., feature/add-dark-mode becomes "Work on: add dark mode").

3. Create the Worktree

Important: The workmux add command must be fully detached from the Claude Code process. workmux creates tmux windows and spawns new Claude sessions, which cannot initialize while the parent Claude Code process is alive. The launch-workmux script handles backgrounding, detaching, waiting, and outputting the log.

Template escaping: workmux renders the prompt body through MiniJinja, so any literal {{, {%, or {# token in the task description (e.g. GitHub Actions ${{ inputs.x }} expressions, Jinja/Liquid/Tera/Helm/Vue templates, Handlebars-style snippets) would otherwise be parsed as a template variable reference and rejected with Template uses undefined variables. The launch-workmux script reads the prompt from stdin, writes an escaped temporary prompt file for workmux add -P, and removes that temporary file after workmux add exits. Each escaped delimiter renders back to the literal characters, so the prompt stored at /.workmux/PROMPT-*.md matches the original input.

Locating the script: At the start of your session, locate the script by searching for **/create-worktree/scripts/launch-workmux. Note the absolute path and use it with bash as the command prefix in all subsequent invocations. Do not use a shell variable, since shell state does not persist between commands.

In the example below, SCRIPTS_DIR/launch-workmux is a placeholder for the script's quoted absolute path (e.g., "/absolute/path/to/plugins/create-worktree/scripts/launch-workmux"). Always invoke via bash followed by the quoted path. This ensures the command token is bash, which matches stable allowlist patterns regardless of the plugin's installed path or version.

Do not specify --base. Let workmux use its default. Only pass --base BRANCH if the user explicitly requests a specific base branch.

Then launch the worktree:

bash "SCRIPTS_DIR/launch-workmux" "BRANCH_NAME" <<'WORKMUX_PROMPT'
Work on: [user's task description]

Branch: [BRANCH_NAME]
WORKMUX_PROMPT

If the user requested a specific base branch:

bash "SCRIPTS_DIR/launch-workmux" "BRANCH_NAME" --base "BASE_BRANCH" <<'WORKMUX_PROMPT'
Work on: [user's task description]

Branch: [BRANCH_NAME]
WORKMUX_PROMPT

The script outputs the workmux log directly and cleans up its own log file. Verify success:

git worktree list

4. Report Success

After confirming the worktree exists in git worktree list, report:

• The branch name created
• The tmux window name (to help the user switch to it)
• A note that the task prompt was injected into the new session

Error Handling

• If workmux is not installed, inform the user and suggest installing it
• If the branch already exists and --open-if-exists opens it, note that the prompt is only injected on initial creation

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: cboone
• Source: cboone/agent-harness-plugins
• License: MIT
• Homepage: https://github.com/cboone/agent-harness-plugins

Install and usage instructions live in the source repository linked above.