maestro/docs/WORKTREES.md

Worktrees

Maestro can create a git worktree for a session and is responsible for it from that moment until the worktree is removed. This document is the contract for that lifetime: where a worktree goes, what ends a session, what survives, and what the operator has to do by hand.

It exists because the rules here are not guessable from the code. Every rule below was decided once, re-litigated in review, and decided the same way again. The reasoning is written down alongside each rule so the next reader does not have to reconstruct it.

Nothing is ever adopted

The daemon only ever removes a worktree it created in this session's lifetime or recorded in its retained store. It never takes ownership of a directory it finds on disk, whatever that directory looks like.

There is no reliable way to ask "is this worktree mine?". A git worktree carries no marker distinguishing one a daemon made from one a human made ten minutes earlier, and any heuristic that answers the question will eventually answer it wrong — in the direction of deleting somebody's work.

So the daemon does not ask. If the target path is occupied by anything at all, it picks a different path.

Placement

A worktree for branch <branch> of repository <repo> goes to <repo>/worktrees/<branch>, where <repo> is the main checkout — not whichever worktree the request happened to come from.

The branch name is used verbatim as a relative path, so feature/login becomes worktrees/feature/login. A branch name that cannot be a relative path falls back to a short hash of the branch.

If that path exists, the daemon appends -2, then -3, and so on until it finds a free one. The suffix names the directory only. The branch is whatever was requested; a second worktree of the same branch is not what happens here, because git refuses to check the same branch out twice and the branch picker already marks branches that are checked out elsewhere.

The worktree_root override

[daemon].worktree_root moves every worktree out of the repository and under one root. The per-repository directory is the repository's basename plus a short digest of its full path — the digest is what keeps two repositories with the same basename apart. Inside it the layout and the collision suffix are the same.

What ends a session

DELETE /api/sessions/:id is refused when the session's worktree holds unsaved work, meaning any of:

• uncommitted changes to tracked files
• untracked files that are not ignored
• commits on the branch reachable from no remote-tracking ref

Ignored files never block. Every Rust worktree has a target/; if ignored files counted, no session would ever be killable.

The refusal is a structured error naming what blocked it and how much of it there is, so a client can say "3 uncommitted files, 2 unpushed commits". The session keeps running and the worktree is untouched.

The point of refusing rather than cleaning up is that the session stays as the operator's handle on their own unfinished work. A session that is killed while its worktree still matters leaves a directory nobody is looking at.

A consequence, accepted deliberately: a feature branch almost always has unpushed commits, so --force is the ordinary way to end a session, not an exception. That is only safe because force retains.

--force

--force overrides the refusal and nothing else. It ends the session and retains the worktree, which enters the retained store with reason force-killed. Force never removes a tree that would have blocked. A tree whose guard is clear never needed the override, so a forced kill removes it as usual — force changes what happens to blocked work, not ordinary cleanup.

Ending a session and destroying its work are two separate destructive acts. Each is chosen on its own, and the second one — reclaim — is chosen while looking at exactly what would be lost.

A forced kill answers with what was retained and why, so a client can say where the work went rather than leaving the operator to wonder.

Exiting on its own

A session that ends by itself — the command finished, the operator typed exit — never reaches the kill path. When the watcher notices the tmux session is gone it applies the same rule: a pristine worktree is removed, anything else is retained with reason exited-with-unsaved-work.

Nobody is waiting for an answer here, so there is nothing to refuse; the choice is only between removing and retaining. It uses the same predicate as the kill, from the same place, so the two paths cannot drift apart.

The retained store

A state_dir-backed record of worktrees the daemon created that no longer have a session. For each one: the path, the base repository, the branch, why it was retained, and when.

It survives a daemon restart. It is the recovery path for everything above — a store that is lost on restart is worse than no store, because the worktrees are still on disk with nothing pointing at them.

Entries leave when the worktree is reclaimed, and when the daemon notices the directory is gone because somebody removed it by hand.

It is not an ownership record. It must never be consulted to decide whether a path may be adopted — see the first rule. Its only job is to remember what the daemon is holding so that it can be listed and reclaimed.

Reclaim

GET /api/worktrees lists the store: path, base repository, branch, reason, when, and what is currently in the way. The in-the-way breakdown is recomputed on read, not stored, so a tree whose work has since been pushed says so.

DELETE /api/worktrees/<id> reclaims one. It removes the directory and drops the store entry. It does not consult the guard — reclaim is the deliberate destructive act, and the operator chose it while looking at what was in the way.

It never deletes the branch. git worktree remove leaves the ref, and reclaiming a tree must not throw away commits on it. This is worth saying out loud in every client, because "reclaim" otherwise sounds like it takes the commits too.

Nothing is reclaimed automatically. There is no age-based expiry and no bulk reclaim.