name	drummer
description	Review and merge open PRs for claimed ba tasks as a cohesive batch

Drummer

The collective that processes in rhythm. Holistically review pending PRs, then squash-merge them as a cohesive batch.

Invocation

/drummer

Flow

Read dive context (if available) for project background:
```
cat .wm/dive_context.md 2>/dev/null || echo "No dive context"
```
This provides architecture decisions, conventions, and session intent.
Find claimed tasks:
```
ba list --status=in_progress
```
For each claimed task, find its PR with drummer-merge label:
```
gh pr list --head ba/<task-id> --label drummer-merge --json number,title,mergeable,additions,deletions,labels
```
Only PRs with the drummer-merge label are eligible for merge. Skip PRs without this label and report them as "awaiting human approval".
Batch review - evaluate all PRs together:
- Collect combined diff of all PRs against main
- Run sg review on the combined changes
- Evaluate:
  - Do changes conflict logically? (same code modified differently)
  - Is there duplicate work? (two PRs solving same problem)
  - Do changes compose well? (feature A + feature B = coherent whole)
  - Any cross-cutting concerns? (shared dependencies, API changes)
- If concerns found:
  - Report issues
  - Ask human whether to proceed or address first

For each PR (in dependency order):

Rebase onto latest main:

git fetch origin
gh pr checkout <pr-number>
git rebase origin/main

If .ba/ conflict, resolve mechanically (each task = one line)
Push rebased branch:
```
git push --force-with-lease
```
Squash merge:
```
gh pr merge <pr-number> --squash
```

Verify task closure - After merge, ensure all tasks from this PR are closed:

git pull origin main
for task_id in <tasks-from-pr>; do
  ba show $task_id  # Check status
  # If not closed, fix it:
  ba finish $task_id
done
# If any fixes were needed:
git add .ba/ && git commit -m "fix: close tasks after merge" && git push origin main

Squash merge can lose .ba/ changes during conflict resolution. This step ensures all merged tasks end in closed state regardless of what the merge preserved.

Signal completion (MANDATORY) - This is the LAST thing you do:

# On success:
curl -sS -X POST "http://localhost:${MIRANDA_PORT}/complete" \
  -H "Content-Type: application/json" \
  -d "{\"session\": \"$TMUX_SESSION\", \"status\": \"success\"}"

# On error:
curl -sS -X POST "http://localhost:${MIRANDA_PORT}/complete" \
  -H "Content-Type: application/json" \
  -d "{\"session\": \"$TMUX_SESSION\", \"status\": \"error\", \"error\": \"<reason>\"}"

If you don't signal, Miranda won't know you're done and the session becomes orphaned.

Stacked PRs

When PRs target other PRs (not main), drummer detects the stack and merges in order:

Find root PRs (target main)
Merge root PR
Rebase child PRs onto main, update their target to main
Repeat until stack is flattened

Before:  PR #43 → ba/abc-123 → main
         PR #42 → main

After:   PR #42 merged to main
         PR #43 rebased onto main, merged to main

Batch Review Criteria

The holistic review checks what individual PR reviews can't:

Logical conflicts: PR A assumes X, PR B assumes not-X
Duplication: Both PRs add similar functionality
Integration issues: Combined changes break something neither breaks alone
Ordering dependencies: PR B depends on PR A being merged first (auto-detected for stacked PRs)
Scope creep: Batch as a whole does more than originally intended

Conflict Resolution

.ba/issues.jsonl is line-per-task:

Each line is independent
Resolution: union of all lines (dedupe by task ID)
Never lose a task closure

Prerequisites

PRs must have the drummer-merge label (human approval gate)
PRs must have CI passing
No code conflicts (only .ba/ conflicts handled automatically)
Batch review must pass (or human override)

Note: The drummer-merge label must be created in the repo. This is opt-in per repo.

Exit Conditions

Success: All eligible PRs reviewed and merged → signal status: "success"
Needs attention: Batch review raised concerns - waiting for human decision (no signal - awaiting input)
Error: Unrecoverable failure (code conflicts, CI failing, etc.) → signal status: "error" with message

Example

$ /drummer

Finding claimed tasks...
Found 3 in_progress tasks: abc-123, abc-456, abc-789

Checking for open PRs with drummer-merge label...
  abc-123: PR #42 "Fix validation bug" (CI ✓, drummer-merge ✓)
  abc-456: PR #43 "Add edge case tests" (CI ✓, drummer-merge ✓)
  abc-789: PR #44 "Refactor validator" (CI ✓) ⏳ awaiting approval

Running batch review on combined changes...
Collecting diffs: +847 -203 across 12 files

Batch review complete:
  ✓ No logical conflicts
  ✓ No duplication
  ⚠ Ordering dependency: PR #44 (refactor) should merge before PR #42 (fix)

Reordering merge sequence: #44 → #42 → #43

Processing PR #44 (Refactor validator)...
  Rebasing onto main... clean
  Squash merging... ✓

Processing PR #42 (Fix validation bug)...
  Rebasing onto main... clean
  Squash merging... ✓

Processing PR #43 (Add edge case tests)...
  Rebasing onto main...
  Conflict in .ba/issues.jsonl (expected)
  Resolving: keeping all task closures
  Squash merging... ✓

Merge train complete.
  Merged: 2 PRs (#42, #43)
  Skipped: 1 PR (#44 - awaiting drummer-merge label)

Signaling completion...
Done.

drummer

Install Skill

SKILL.md