Merge Queue

Merge Queue

Instructions

Land every branch that is ready — the whole queue if $ARGUMENTS is empty, otherwise only the work item IDs it names.

/deliver-cluster owns the merge queue for the cluster it is delivering. This skill is for everything that skill cannot see: several agents delivering different use cases or different clusters at the same time, a branch left behind by a run that stopped, or a set of pull requests opened by --review runs that now have to land.

The queue is a discovery-and-ordering skill. It never merges into main itself and it does not own a gate — every item goes through /merge-use-case, which rebases, runs the full unfiltered regression suite, merges, closes the issue, and removes the worktree. The only merge the queue performs is landing an already-gated pull request on GitHub, which /merge-use-case --after-review then books.

When to use

• Several agents delivered work in parallel worktrees and their branches are all waiting.
• A --review run opened pull requests and they are approved and ready to land.
• A previous merge run stopped part-way and left branches behind.

Use /merge-use-case <ID> instead when exactly one branch is waiting.

Prerequisites

• gh is authenticated — the queue reads pull requests and closes issues through it
• At least one worktree or open pull request exists for a work item branch

Nexa Rules Gate

Read and follow ${CLAUDE_PLUGIN_ROOT}/shared/readiness/NEXA_RULES_GATE.md.

No Worktree Gate

This skill runs in the primary checkout on main. It reads worktrees and merges from the primary checkout; it never runs inside one. It is listed in the Exceptions section of ${CLAUDE_PLUGIN_ROOT}/shared/readiness/WORKTREE_GATE.md.

DO NOT

• Merge into main yourself — every item's gate runs through /merge-use-case
• Run two /merge-use-case invocations at the same time, even for unrelated items
• Hold the merge lock across the whole queue — each item takes and releases its own, so an agent that finishes mid-run can still land its branch between two items
• Land an item before an item it depends on
• Retry an item whose gate went red — it leaves the queue for this run
• Remove a worktree whose branch did not merge

Process

Step 1: Discover the candidates

Two sources, because a branch can be waiting in either:

git fetch origin main
git worktree list --porcelain
gh pr list --base main --state open --json number,headRefName,title,reviewDecision

Take every worktree on a uc/UC-*, tt/TT-*, bug/BUG-*, or cr/CR-* branch, plus every open pull request whose head branch matches one of those prefixes. The same item can appear in both — that is one candidate, not two.

If $ARGUMENTS names IDs, keep only those and report any it names that no source produced.

Step 2: Classify each candidate

Read Depends On from docs/use_cases/UC-XXX.md, falling back to docs/engineering/cluster-N-analysis.md, exactly as /deliver-cluster Step 3 does. A work item type other than a use case has no dependency row — treat it as unblocked.

Step 3: Order the queue

Sort so a dependency always lands before what depends on it. Among items with no dependency between them, order by the age of the branch head — the oldest merges first, because it has been diverging from main the longest and its rebase is the one most likely to conflict.

Detect cycles. A cycle in the queue cannot be landed in any order:

MERGE QUEUE BLOCKED — the dependency graph has a cycle

UC-004 -> UC-007 -> UC-004

Nothing was merged. Run /engineer-requirements to split or merge the use cases.

Print the plan before merging anything:

Merge queue — <N> ready, <M> skipped

Order:
  1. UC-001  worktree ../app-UC-001        (no dependencies)
  2. UC-003  worktree ../app-UC-003        (after UC-001)
  3. TT-010  PR #42, approved            (gh pr merge, then --after-review)

Skipped:
  UC-007  awaiting review — <pull request URL>
  UC-009  unproven — worktree exists, pipeline never ran

Step 4: Merge, one at a time

For each item in order, invoke /merge-use-case <ID> — the plain form for a worktree item.

An approved pull request takes the other route. Merge the pull request on GitHub first, then run the bookkeeping form:

gh pr merge <number> --rebase --delete-branch=false

then /merge-use-case <ID> --after-review. Do not send an approved pull request through the plain form: it rebases the branch locally and fast-forwards main without pushing the branch, so the commits GitHub sees on the pull request are never the commits that land. The pull request stays open, its issue stays open, and its worktree leaks.

Wait for it to finish before starting the next. Each invocation takes the merge lock, so a second concurrent one would stop on the lock rather than corrupt anything — but it would also report a failure that is not real. Serial invocation keeps the report honest.

Between items, re-read the state of what is left. A merge sets its work item to Status: Done on main, which can unblock a later item that Step 2 classified as Blocked; bring it into the queue when it becomes ready.

Three outcomes per item:

A red gate on one item never stops the others. An item that depends on the red one stays blocked and is reported as such.

Step 5: Report

## Merge Queue — <n> of <total> landed

| Item   | Route             | Result   |
|--------|-------------------|----------|
| UC-001 | worktree          | merged   |
| UC-003 | worktree          | gate red |
| TT-010 | PR #42 (approved) | merged   |

Landed:    <IDs, in merge order>
Gate red:  <ID — which gate failed, and the worktree that still holds the work>
Locked out: <ID — another agent held the merge lock for the whole run>
Skipped:   <ID — awaiting review / unproven / blocked on X>

No red branch was retried. Fix them in their worktrees, then run /merge-queue again — it also
picks up whatever was locked out.

Name the worktree path for every item that did not land, so the work can be picked up. Never remove a worktree whose branch did not merge — it holds the only copy of that work.

If any item merged, regenerate the project overview with /dashboard and commit it, the same way /deliver-cluster Step 8 does.

Verification

1. At no point were two /merge-use-case runs in flight.
2. <git-common-dir>/nexa-merge.lock does not exist when the run ends.
3. git log --graph --oneline main | head -30 shows no merge commit.
4. Every landed item's worktree is gone from git worktree list; every red item's worktree is still there.
5. No item landed before an item it depends on — git log --oneline main has them in dependency order.
6. Every open pull request that was not approved is still open and untouched.
7. Every approved pull request that landed shows as merged on GitHub, with its issue closed and its worktree removed — the --after-review bookkeeping ran.