Land Stack

Take a finished orchestrate-implementation run from "every ticket has a draft PR" to "every PR is merged and every issue is closed". Each ticket keeps its own chained worktree until its merge is confirmed on the remote, then its environment is retired. Landing is one-way, so each step proves its precondition before acting.

Contract

• Land oldest first. A PR merges only when it targets the target branch, its head equals the ledger's accepted head, and its checks are green.
• Human approval is optional. Without --require-approvals, the loop gate and green checks are the review. Say so in the report.
• Stop at the first PR that cannot merge. Merged tickets stay merged; the run pauses with the ledger and evidence, and resume continues from the next. The order is mechanical, not policy: no one's authority over the repository makes a later PR safe to land while an earlier one is red.
• Archive a ticket environment only after its merge is confirmed on the remote.
• Work from the ledger: read run.json, write every transition.

References

This skill spawns no workers. It needs ../bb-worker-protocol/references/run-lifecycle.md to carry it between turns and ../bb-worker-protocol/references/github.md to decide how the gh commands below actually run. Use ../bb-worker-protocol/references/pr-stack.md to bring each child onto the target branch. The ledger schema is ../bb-worker-protocol/references/run-ledger.md; landing fills tickets.<id>.landing and the top-level landing object.

Prepare

1. Read the run ledger: the attached path, else $BB_THREAD_STORAGE/orchestrate-implementation/run.json. Require state: finished, or landing already present for resume. Reconcile every PR with gh pr view before the first transition.
2. Pick the merge method: --method when given, else the first allowed of merge, squash, rebase from gh api repos/{owner}/{repo} --jq '[.allow_merge_commit,.allow_squash_merge,.allow_rebase_merge]'. A merge commit keeps children retargetable; squash and rebase need the rebase path for every child.
3. Verify authenticated gh, push access, and the tracker workflow in docs/agents/issue-tracker.md. Record landing in the ledger.

Land one ticket

For the oldest unmerged ticket in order:

1. Bring it onto the target with the parent-merge procedure in pr-stack.md (direct retarget or rebase). Its PR must now target <target>. The first ticket of a run already does, so it needs neither.

2. Gate:

   gh pr view "$URL" --json state,isDraft,baseRefName,headRefOid,mergeable,mergeStateStatus,reviewDecision
   gh pr checks "$URL" --watch --fail-fast

   Require baseRefName equal to the target, headRefOid equal to accepted_head, mergeable: MERGEABLE, and no failing check outside the run's ci_baseline or the loop quarantine. A check that already failed on the target branch when the run started is inherited, not caused: report it and merge. A failure matching a quarantined entry is reported with its ticket and merges the same way. A run whose ledger has no ci_baseline measures one now against the target branch rather than treating a red repository as a blocked stack. With --require-approvals, also require reviewDecision: APPROVED and zero unresolved review threads:

   gh api graphql -F o=<owner> -F r=<repo> -F n=<number> -f query='query($o:String!,$r:String!,$n:Int!){repository(owner:$o,name:$r){pullRequest(number:$n){reviewThreads(first:100){nodes{isResolved}}}}}'

   Unresolved threads without --require-approvals are findings: run /review-fix-loop <target> <ticket> --from-pr <url>, refresh the PR body with gh pr edit --body-file, then gate again.

3. Merge:

   gh pr ready "$URL"
   gh pr merge "$URL" --<method> --match-head-commit "$ACCEPTED_HEAD" --delete-branch
   gh pr view "$URL" --json state,mergeCommit,mergedAt

   state must be MERGED. Record merge_commit and merged_at. bb environment pull-request merge takes only --method, so it cannot assert the head or delete the branch; keep gh pr merge here.

4. Close the ticket through the tracker workflow with a comment that links the PR. GitHub closes issues named by Fixes #n on its own, so check first:

   gh issue view <n> --json state
   gh issue close <n> --reason completed --comment "Landed in $URL"

5. Clean up unless --keep-environments:

   bb environment archive-threads "$ENV"
   bb environment show "$ENV" --json          # .status becomes destroying, then destroyed

   Archiving every live thread of a managed worktree destroys that worktree and its local branch. Confirm both the environment status and the missing worktree path before recording environment_state: archived.

6. Write tickets.<id>.state: merged, then continue with the next ticket. Its parent is now merged, so step 1 retargets or rebases it.

Pause

A failing check, a conflict, a head that moved, a non-mergeable PR, or a review decision that blocks pauses the landing. Nothing merged is undone. resume reconciles the ledger and starts at the first unmerged ticket.

Rationalizations

Red flags — stop

• About to merge a PR whose baseRefName is not the target branch
• About to merge without --match-head-commit
• About to archive an environment before gh pr view says MERGED
• About to skip a blocked ticket and land a later one
• About to close a ticket whose PR did not merge
• About to reorder the stack because the person asking outranks you
• About to rebase past a blocked ticket rather than stopping at it

Finish

Report each ticket with its PR, merge commit, issue state, and environment state, plus the merge method and whether approvals were required. Set state: landed in the ledger. Then invoke /verify-landing <ledger path>: landing proves the merges, verification proves the target.