Using Git Worktrees

Overview

Git worktrees create isolated workspaces sharing the same repository, allowing work on multiple branches simultaneously without switching.

Core principle: In opencode v2, worktrees are created with the native worktree_* tools, and the session moves into the worktree — not just the shell. This keeps opencode's tracking (list/remove), project config, and AGENTS.md discovery pointing at the right place.

Announce at start: "I'm using the using-git-worktrees skill to set up an isolated workspace."

Default Path: Native Worktree Tools

Use this when running inside opencode v2 (the normal case). The tools are worktree_create, worktree_list, worktree_remove (Code Mode namespace opencode), plus session_move.

1. Create the worktree

Call worktree_create with a name — use the feature/branch name (e.g. auth, fix-login-timeout). It returns { directory }.

Where the worktree lands is decided by the worktree.directory setting in the project's opencode config, not by the skill:

• Not set (default): opencode's data directory, worktree/<project-id prefix>/<name> — outside the repo, so nothing to gitignore.
• Set (e.g. "worktree": { "directory": ".worktrees" }): relative paths resolve against the project's canonical checkout. If the directory is inside the repo, it must be gitignored (see below).

Do not hand-roll the location with git worktree add — opencode only records and manages worktrees it created itself, so manual ones are invisible to worktree_list / worktree_remove.

If the user wants a non-default location, the v2-idiomatic move is to set worktree.directory in the config (and note it in AGENTS.md or memory) — not to pick a path per session.

2. Create the branch

worktree_create does not take a branch name: the new worktree is at a detached HEAD on the repo's current commit. Create the branch from inside the worktree:

git checkout -b "<branch-name>"

(git checkout main would fail — main is already checked out in the primary worktree; that is expected and not an error.)

3. Move the session into the worktree

Call session_move with the worktree directory as directory. The move takes effect at a safe boundary, so destination-dependent work (reads, edits, setup commands) belongs in the next call.

Why this instead of cd: a shell cd only changes one command's working directory; session_move re-roots the session's Location, so tool calls, config discovery, and instruction files all resolve against the worktree checkout.

4. Project-local location safety (only if inside the repo)

When worktree.directory places worktrees inside the checkout (.worktrees/, worktrees/, …), verify the directory is ignored before creating the worktree:

git check-ignore -q .worktrees 2>/dev/null || git check-ignore -q worktrees 2>/dev/null

If not ignored: add it to .gitignore, commit, then create. This prevents worktree contents from polluting git status or being accidentally committed.

5. Run project setup

The worktree is a fresh checkout — dependencies are not shared with the main worktree. Auto-detect and run setup:

# Node.js
[ -f package.json ] && npm install

# Rust
[ -f Cargo.toml ] && cargo build

# Python
[ -f requirements.txt ] && pip install -r requirements.txt
[ -f pyproject.toml ] && poetry install

# Go
[ -f go.mod ] && go mod download

6. Verify clean baseline and report

Run the project's tests to confirm the worktree starts green:

# project-appropriate: npm test / cargo test / pytest / go test ./...

If tests fail: report the failures and ask whether to proceed or investigate. If they pass: report ready.

Worktree ready at <full-path> (branch <name>)
Session moved. Tests passing (<N> tests, 0 failures)
Ready to implement <feature-name>

Cleanup

Pairs with finishing-a-development-branch after the work is done:

• worktree_remove with the worktree directory removes a worktree opencode recorded for the project. It uses the edit permission on that directory; set force: true only to discard uncommitted changes.
• Never remove a worktree with unpushed, unmerged commits without explicit confirmation — that deletes the work.
• A worktree created manually with raw git (fallback below) is not recorded by opencode; remove it with git worktree remove <path> instead.

Fallback: Raw Git

Use git worktree add directly only when:

• Running in a harness without the native tools (Claude Code, Codex, plain terminal).
• The worktree needs a base other than the current HEAD (git worktree add <path> -b <branch> <base-commit>).
• The user explicitly asks for a manual worktree.

The same safety rules apply: gitignore check for project-local paths, setup, baseline tests, and announce the location.

Quick Reference

Common Mistakes

Assuming worktree_create makes a branch

• Problem: It leaves a detached HEAD; commits land nowhere a branch points at.
• Fix: git checkout -b <branch> inside the worktree immediately after creation.

cd-ing into the worktree instead of session_move

• Problem: Only the shell's CWD changes; the session, config, and instruction discovery still point at the old location.
• Fix: Call session_move; put dependent work in the next turn.

Hand-rolling git worktree add in opencode

• Problem: opencode doesn't record manual worktrees, so worktree_list/worktree_remove can't see them, and the location ignores worktree.directory.
• Fix: Use the native tools in v2; raw git is the fallback above.

Proceeding with failing baseline tests

• Problem: Can't distinguish new bugs from pre-existing issues.
• Fix: Report failures, get explicit permission to proceed.

Red Flags

Never:

• Commit on the detached HEAD (create the branch first)
• Remove a worktree with unpushed/unmerged work without confirmation
• Skip baseline test verification
• Assume the default location when the user has a project-local preference — check/set worktree.directory

Always:

• Use native tools in opencode v2, raw git only in the fallback cases
• Move the session with session_move after creation
• Verify gitignore for in-repo locations
• Auto-detect and run project setup, then a clean test baseline

Example Workflow

You: I'm using the using-git-worktrees skill to set up an isolated workspace.

[worktree_create name="auth" -> C:\Users\osmon\.local\share\opencode\worktree\c3488b\auth]
[git checkout -b feature/auth]
[session_move directory=<worktree dir>]
[npm install, npm test - 47 passing]

Worktree ready at C:\Users\osmon\.local\share\opencode\worktree\c3488b\auth (branch feature/auth)
Session moved. Tests passing (47 tests, 0 failures)
Ready to implement auth feature

Integration

Called by:

• subagent-driven-development - REQUIRED before executing any tasks
• executing-plans - REQUIRED before executing any tasks
• Any skill needing an isolated workspace

Pairs with:

• finishing-a-development-branch - REQUIRED for cleanup after work complete