[DrewBradfordXYZ]

One commit on main (d56195b). It follows up on #170/#183 (the DELETE CHECK): when that merged, you said the follow-ups could go against main. This is the small one, and worktree-safe-to-delete stacks on it.

Why

git worktree lock --reason … is git's way of saying "keep this checkout". Git's own worktree remove and worktree prune refuse a locked worktree. People lock checkouts, and so do agents and tools. One example is a CI or merge-queue tool that reuses a scratch worktree for every run: it locks it so nobody clears it in between.

nebula never showed a lock. Its delete unlocked any lock it found and went ahead. So a locked checkout looked like any other clean one, and one d removed it. Auto-clean merged worktrees could remove one without asking anyone.

What

• The delete confirm leads with the lock. The DELETE CHECK reads it (git worktree list --porcelain), and the confirm's first line is ⚠ locked: <reason> — deleting unlocks it, or no reason given. A bulk delete's line says locked: <reason>. Nothing is assumed about who locked it or whether the lock is stale: the person reads the reason and decides.
• Auto-clean skips a locked checkout and says so: auto-cleanup skipped <branch>: checkout is locked (<reason>).
• Docs: docs/sessions.md (what the confirm lists), docs/keys.md and docs/configuration.md (auto-clean).

Protocol

Protocol 53, additive; MIN_COMPATIBLE_PROTOCOL is unchanged. WorktreeCheck::locked is its last field and stays off the wire when it is None, so a check of an unlocked worktree is byte for byte what it was. The daemon records each client's Hello version and clears the lock for a client older than 53. Compact MessagePack frames are arrays, so an older client fails on a field it doesn't know; serde(default) alone doesn't help in that direction.

53 assumes #174 takes 52. If #174 or #178 lands after this, or this lands first, the number moves to the next free one. It is one constant (WORKTREE_LOCK_PROTOCOL) plus PROTOCOL_VERSION.

How verified

• cargo fmt --all --check and cargo clippy --workspace --all-targets -- -D warnings are clean, and cargo test --workspace passes 1,942 tests on macOS.
• Tests: the git worktree list --porcelain parser picking the target stanza's lock and reason, C-style quoted reasons included; the lock read back from a real git worktree lock (git.rs); auto-clean skipping a locked checkout (registry.rs); the confirm leading with the lock and its reason (delete_check.rs); and a lock costing an older client nothing on the wire (protocol.rs).
• Used daily since 2026-10-21 in a build of nebula with this patch, on a repo whose merge-queue tool locks its own probe worktree: its delete confirm leads with the tool's reason, and auto-clean leaves it.